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• Critical Offset Magnetic PArticle SpectroScopy for rapid and highly sensitive medical point-of-care diagnostics Vogel, Patrick; Rückert, Martin Andreas; Friedrich, Bernhard; Tietze, Rainer; Lyer, Stefan; Kampf, Thomas; Hennig, Thomas; Dölken, Lars; Alexiou, Christoph; Behr, Volker Christian in Nat. Commun. (2022). 13(1) 7230.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  • [ DOI ]
  Magnetic nanoparticles (MNPs) have been adapted for many applications, e.g., bioassays for the detection of biomarkers such as antibodies, by controlled engineering of specific surface properties. Specific measurement of such binding states is of high interest but currently limited to highly sensitive techniques such as ELISA or flow cytometry, which are relatively inflexible, difficult to handle, expensive and time-consuming. Here we report a method named COMPASS (Critical-Offset-Magnetic-Particle-SpectroScopy), which is based on a critical offset magnetic field, enabling sensitive detection to mini- mal changes in mobility of MNP ensembles, e.g., resulting from SARS-CoV-2 antibodies binding to the S antigen on the surface of functionalized MNPs. With a sensitivity of 0.33 fmole/50 μl (≙7 pM) for SARS-CoV-2-S1 antibodies, measured with a low-cost portable COMPASS device, the proposed technique is competitive with respect to sensitivity while providing flexibility, robustness, and a measurement time of seconds per sample. In addition, initial results with blood serum demonstrate high specificity.

  @article{vogel2022critical, abstract = {Magnetic nanoparticles (MNPs) have been adapted for many applications, e.g., bioassays for the detection of biomarkers such as antibodies, by controlled engineering of specific surface properties. Specific measurement of such binding states is of high interest but currently limited to highly sensitive techniques such as ELISA or flow cytometry, which are relatively inflexible, difficult to handle, expensive and time-consuming. Here we report a method named COMPASS (Critical-Offset-Magnetic-Particle-SpectroScopy), which is based on a critical offset magnetic field, enabling sensitive detection to mini- mal changes in mobility of MNP ensembles, e.g., resulting from SARS-CoV-2 antibodies binding to the S antigen on the surface of functionalized MNPs. With a sensitivity of 0.33 fmole/50 μl (≙7 pM) for SARS-CoV-2-S1 antibodies, measured with a low-cost portable COMPASS device, the proposed technique is competitive with respect to sensitivity while providing flexibility, robustness, and a measurement time of seconds per sample. In addition, initial results with blood serum demonstrate high specificity.}, author = {Vogel, Patrick and Rückert, Martin Andreas and Friedrich, Bernhard and Tietze, Rainer and Lyer, Stefan and Kampf, Thomas and Hennig, Thomas and Dölken, Lars and Alexiou, Christoph and Behr, Volker Christian}, journal = {Nat. Commun.}, keywords = {peer}, month = 11, number = 1, pages = 7230, title = {Critical Offset Magnetic PArticle SpectroScopy for rapid and highly sensitive medical point-of-care diagnostics}, volume = 13, year = 2022 }

  %0 Journal Article %1 vogel2022critical %A Vogel, Patrick %A Rückert, Martin Andreas %A Friedrich, Bernhard %A Tietze, Rainer %A Lyer, Stefan %A Kampf, Thomas %A Hennig, Thomas %A Dölken, Lars %A Alexiou, Christoph %A Behr, Volker Christian %D 2022 %J Nat. Commun. %N 1 %P 7230 %R 10.1038/s41467-022-34941-y %T Critical Offset Magnetic PArticle SpectroScopy for rapid and highly sensitive medical point-of-care diagnostics %V 13 %X Magnetic nanoparticles (MNPs) have been adapted for many applications, e.g., bioassays for the detection of biomarkers such as antibodies, by controlled engineering of specific surface properties. Specific measurement of such binding states is of high interest but currently limited to highly sensitive techniques such as ELISA or flow cytometry, which are relatively inflexible, difficult to handle, expensive and time-consuming. Here we report a method named COMPASS (Critical-Offset-Magnetic-Particle-SpectroScopy), which is based on a critical offset magnetic field, enabling sensitive detection to mini- mal changes in mobility of MNP ensembles, e.g., resulting from SARS-CoV-2 antibodies binding to the S antigen on the surface of functionalized MNPs. With a sensitivity of 0.33 fmole/50 μl (≙7 pM) for SARS-CoV-2-S1 antibodies, measured with a low-cost portable COMPASS device, the proposed technique is competitive with respect to sensitivity while providing flexibility, robustness, and a measurement time of seconds per sample. In addition, initial results with blood serum demonstrate high specificity.

• Magnetic particle imaging for artifact-free imaging of intracranial flow diverter stents: A phantom study Herzberg, M.; Dorn, F.; Dietrich, P.; Rückert, M.A.; Kampf, T.; Bley, T.A.; Behr, V.C.; Herz, S.; Vogel, P. in Phys. Med. (2021). 88 65–70.
  • [ Abstract ]
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  Purpose Magnetic Particle Imaging (MPI) is a new, background- and radiation-free tomographic imaging method that enables near real-time imaging of superparamagnetic iron-oxide nanoparticles (SPIONs) with high temporal and spatial resolution. This phantom study aims to investigate the potential of MPI for visualization of the stent lumen in intracranial flow diverters (FD). Methods Nitinol FD of different dimensions (outer diameter: 3.5 mm, 4.0 mm, 5.5 mm; total length: 22–40 mm) were scanned in vascular phantoms in a custom-built MPI scanner (in-plane resolution: ~ 2 mm, field of view: 65 mm length, 29 mm diameter). Phantoms were filled with diluted (1:50) SPION tracer agent Ferucarbotran (10 µmol (Fe)/ml; NaCL). Each phantom was measured in 32 different projections (overall acquisition time per image: 3200 ms, 5 averages). After image reconstruction from raw data, two radiologists assessed image quality using a 5-point Likert scale. The signal intensity profile was measured using a semi-automatic evaluation tool. Results MPI visualized the lumen of all FD without relevant differences between the stented vessel phantom and the reference phantom. At 3.5 mm image quality was slightly inferior to the larger diameters. The FD themselves neither generated an MPI signal nor did they lead to relevant imaging artifacts. Ratings of both radiologists showed no significant difference, interrater reliability was good (ICC 0.84). A quantitative evaluation of the signal intensity profile did not reveal any significant differences (p > 0.05) either. Conclusion MPI visualizes the lumen of nitinol FD stents in vessel phantoms without relevant stent-induced artifacts.

  @article{herzberg2021magnetic, abstract = {Purpose Magnetic Particle Imaging (MPI) is a new, background- and radiation-free tomographic imaging method that enables near real-time imaging of superparamagnetic iron-oxide nanoparticles (SPIONs) with high temporal and spatial resolution. This phantom study aims to investigate the potential of MPI for visualization of the stent lumen in intracranial flow diverters (FD). Methods Nitinol FD of different dimensions (outer diameter: 3.5 mm, 4.0 mm, 5.5 mm; total length: 22–40 mm) were scanned in vascular phantoms in a custom-built MPI scanner (in-plane resolution:   2 mm, field of view: 65 mm length, 29 mm diameter). Phantoms were filled with diluted (1:50) SPION tracer agent Ferucarbotran (10 µmol (Fe)/ml; NaCL). Each phantom was measured in 32 different projections (overall acquisition time per image: 3200 ms, 5 averages). After image reconstruction from raw data, two radiologists assessed image quality using a 5-point Likert scale. The signal intensity profile was measured using a semi-automatic evaluation tool. Results MPI visualized the lumen of all FD without relevant differences between the stented vessel phantom and the reference phantom. At 3.5 mm image quality was slightly inferior to the larger diameters. The FD themselves neither generated an MPI signal nor did they lead to relevant imaging artifacts. Ratings of both radiologists showed no significant difference, interrater reliability was good (ICC 0.84). A quantitative evaluation of the signal intensity profile did not reveal any significant differences (p > 0.05) either. Conclusion MPI visualizes the lumen of nitinol FD stents in vessel phantoms without relevant stent-induced artifacts.}, author = {Herzberg, M. and Dorn, F. and Dietrich, P. and Rückert, M.A. and Kampf, T. and Bley, T.A. and Behr, V.C. and Herz, S. and Vogel, P.}, journal = {Phys. Med.}, keywords = {peer}, month = 8, pages = {65-70}, title = {Magnetic particle imaging for artifact-free imaging of intracranial flow diverter stents: A phantom study}, volume = 88, year = 2021 }

  %0 Journal Article %1 herzberg2021magnetic %A Herzberg, M. %A Dorn, F. %A Dietrich, P. %A Rückert, M.A. %A Kampf, T. %A Bley, T.A. %A Behr, V.C. %A Herz, S. %A Vogel, P. %D 2021 %J Phys. Med. %P 65-70 %R 10.1016/j.ejmp.2021.06.018 %T Magnetic particle imaging for artifact-free imaging of intracranial flow diverter stents: A phantom study %V 88 %X Purpose Magnetic Particle Imaging (MPI) is a new, background- and radiation-free tomographic imaging method that enables near real-time imaging of superparamagnetic iron-oxide nanoparticles (SPIONs) with high temporal and spatial resolution. This phantom study aims to investigate the potential of MPI for visualization of the stent lumen in intracranial flow diverters (FD). Methods Nitinol FD of different dimensions (outer diameter: 3.5 mm, 4.0 mm, 5.5 mm; total length: 22–40 mm) were scanned in vascular phantoms in a custom-built MPI scanner (in-plane resolution: ~ 2 mm, field of view: 65 mm length, 29 mm diameter). Phantoms were filled with diluted (1:50) SPION tracer agent Ferucarbotran (10 µmol (Fe)/ml; NaCL). Each phantom was measured in 32 different projections (overall acquisition time per image: 3200 ms, 5 averages). After image reconstruction from raw data, two radiologists assessed image quality using a 5-point Likert scale. The signal intensity profile was measured using a semi-automatic evaluation tool. Results MPI visualized the lumen of all FD without relevant differences between the stented vessel phantom and the reference phantom. At 3.5 mm image quality was slightly inferior to the larger diameters. The FD themselves neither generated an MPI signal nor did they lead to relevant imaging artifacts. Ratings of both radiologists showed no significant difference, interrater reliability was good (ICC 0.84). A quantitative evaluation of the signal intensity profile did not reveal any significant differences (p > 0.05) either. Conclusion MPI visualizes the lumen of nitinol FD stents in vessel phantoms without relevant stent-induced artifacts.
• Synomag®: The new high-performance tracer for magnetic particle imaging Vogel, Patrick; Kampf, Thomas; Rückert, Martin; Grüttner, Cordula; Kowalski, Anja; Teller, Henrik; Behr, Volker in Int. J. Magn. Part. Imag. (2021). 7(1) 2103003.
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  The success of tracer-based tomographic methods, such as Magnetic Particle Imaging (MPI), depends on two factors primarily: scanner hardware and tracer performance. Within the last years, several hardware improvements have been presented improving temporal and spatial resolution of MPI systems. However, there was still a lack of efficient commercially available tracers for MPI. Here we report on synomag® particles as a new tracer tailored for MPI, which shows almost four-times higher signal in a Traveling Wave MPI scanner than the established tracer Resovist®.

  @article{vogel2021synomag, abstract = {The success of tracer-based tomographic methods, such as Magnetic Particle Imaging (MPI), depends on two factors primarily: scanner hardware and tracer performance. Within the last years, several hardware improvements have been presented improving temporal and spatial resolution of MPI systems. However, there was still a lack of efficient commercially available tracers for MPI. Here we report on synomag® particles as a new tracer tailored for MPI, which shows almost four-times higher signal in a Traveling Wave MPI scanner than the established tracer Resovist®.}, author = {Vogel, Patrick and Kampf, Thomas and Rückert, Martin and Grüttner, Cordula and Kowalski, Anja and Teller, Henrik and Behr, Volker}, journal = {Int. J. Magn. Part. Imag.}, keywords = {peer}, month = 3, number = 1, pages = 2103003, title = {Synomag®: The new high-performance tracer for magnetic particle imaging}, volume = 7, year = 2021 }

  %0 Journal Article %1 vogel2021synomag %A Vogel, Patrick %A Kampf, Thomas %A Rückert, Martin %A Grüttner, Cordula %A Kowalski, Anja %A Teller, Henrik %A Behr, Volker %D 2021 %J Int. J. Magn. Part. Imag. %N 1 %P 2103003 %R 10.18416/IJMPI.2021.2103003 %T Synomag®: The new high-performance tracer for magnetic particle imaging %V 7 %X The success of tracer-based tomographic methods, such as Magnetic Particle Imaging (MPI), depends on two factors primarily: scanner hardware and tracer performance. Within the last years, several hardware improvements have been presented improving temporal and spatial resolution of MPI systems. However, there was still a lack of efficient commercially available tracers for MPI. Here we report on synomag® particles as a new tracer tailored for MPI, which shows almost four-times higher signal in a Traveling Wave MPI scanner than the established tracer Resovist®.
• Near real-time magnetic particle imaging for visual assessment of vascular stenosis in a phantom model Dietrich, Philipp; Vogel, Patrick; Kampf, Thomas; Rückert, Martin A.; Behr, Volker C.; Bley, Thorsten A.; Herz, Stefan in Phys. Med. (2021). 81 210–214.
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  Purpose This study aimed to investigate the potential of magnetic particle imaging (MPI) to quantify artificial stenoses in vessel phantoms in near real-time. Methods Custom-made stenosis phantoms with different degrees of stenosis (0%, 25%, 50%, 75%, and 100%; length 40 mm, inner diameter 8 mm, Polyoxymethylene) were filled with diluted Ferucarbotran (superparamagnetic iron-oxide nanoparticle (SPION) tracer agent, 500 mmol (Fe)/l). A traveling wave MPI scanner (spatial resolution ~ 2 mm, gradient strength ~ 1.5 T/m, field of view: 65 mm length and 29 mm diameter, frequencies f1 = 1050 Hz and f2 = 12150 Hz) was used to acquire images of the phantoms (200 ms total acquisition time per image, 10 averages). Standardized grey scaling was used for comparability. All measured stenoses (n = 80) were graded manually using a dedicated software tool. Results MPI allowed for accurate visualization of stenoses at a frame rate of 5 frames per second. Less severe stenoses were detected more precisely than higher-grade stenoses and came with smaller standard deviations. In particular, the 0%, 25%, 50%, 75%, and 100% stenosis phantom were measured as 3.7 ± 2.7% (mean ± standard deviation), 18.6 ± 1.8%, 52.8 ± 3.7%, 77.8 ± 14.8% and 100 ± 0%. Geometrical distortions occurred around the center of the high-grade stenosis and led to higher standard deviations compared to lower grade stenoses. In the frame of this study the MPI signal depended linearly on the SPION concentration down to 0.05 mmol (Fe)/l. Conclusion Near real-time MPI accurately visualized and quantified different stenosis grades in vascular phantoms.

  @article{dietrich2021realtime, abstract = {Purpose This study aimed to investigate the potential of magnetic particle imaging (MPI) to quantify artificial stenoses in vessel phantoms in near real-time. Methods Custom-made stenosis phantoms with different degrees of stenosis (0%, 25%, 50%, 75%, and 100%; length 40 mm, inner diameter 8 mm, Polyoxymethylene) were filled with diluted Ferucarbotran (superparamagnetic iron-oxide nanoparticle (SPION) tracer agent, 500 mmol (Fe)/l). A traveling wave MPI scanner (spatial resolution   2 mm, gradient strength   1.5 T/m, field of view: 65 mm length and 29 mm diameter, frequencies f1 = 1050 Hz and f2 = 12150 Hz) was used to acquire images of the phantoms (200 ms total acquisition time per image, 10 averages). Standardized grey scaling was used for comparability. All measured stenoses (n = 80) were graded manually using a dedicated software tool. Results MPI allowed for accurate visualization of stenoses at a frame rate of 5 frames per second. Less severe stenoses were detected more precisely than higher-grade stenoses and came with smaller standard deviations. In particular, the 0%, 25%, 50%, 75%, and 100% stenosis phantom were measured as 3.7 ± 2.7% (mean ± standard deviation), 18.6 ± 1.8%, 52.8 ± 3.7%, 77.8 ± 14.8% and 100 ± 0%. Geometrical distortions occurred around the center of the high-grade stenosis and led to higher standard deviations compared to lower grade stenoses. In the frame of this study the MPI signal depended linearly on the SPION concentration down to 0.05 mmol (Fe)/l. Conclusion Near real-time MPI accurately visualized and quantified different stenosis grades in vascular phantoms.}, author = {Dietrich, Philipp and Vogel, Patrick and Kampf, Thomas and Rückert, Martin A. and Behr, Volker C. and Bley, Thorsten A. and Herz, Stefan}, journal = {Phys. Med.}, keywords = {peer}, month = 1, pages = {210-214}, title = {Near real-time magnetic particle imaging for visual assessment of vascular stenosis in a phantom model}, volume = 81, year = 2021 }

  %0 Journal Article %1 dietrich2021realtime %A Dietrich, Philipp %A Vogel, Patrick %A Kampf, Thomas %A Rückert, Martin A. %A Behr, Volker C. %A Bley, Thorsten A. %A Herz, Stefan %D 2021 %J Phys. Med. %P 210-214 %R 10.1016/j.ejmp.2020.12.020 %T Near real-time magnetic particle imaging for visual assessment of vascular stenosis in a phantom model %V 81 %X Purpose This study aimed to investigate the potential of magnetic particle imaging (MPI) to quantify artificial stenoses in vessel phantoms in near real-time. Methods Custom-made stenosis phantoms with different degrees of stenosis (0%, 25%, 50%, 75%, and 100%; length 40 mm, inner diameter 8 mm, Polyoxymethylene) were filled with diluted Ferucarbotran (superparamagnetic iron-oxide nanoparticle (SPION) tracer agent, 500 mmol (Fe)/l). A traveling wave MPI scanner (spatial resolution ~ 2 mm, gradient strength ~ 1.5 T/m, field of view: 65 mm length and 29 mm diameter, frequencies f1 = 1050 Hz and f2 = 12150 Hz) was used to acquire images of the phantoms (200 ms total acquisition time per image, 10 averages). Standardized grey scaling was used for comparability. All measured stenoses (n = 80) were graded manually using a dedicated software tool. Results MPI allowed for accurate visualization of stenoses at a frame rate of 5 frames per second. Less severe stenoses were detected more precisely than higher-grade stenoses and came with smaller standard deviations. In particular, the 0%, 25%, 50%, 75%, and 100% stenosis phantom were measured as 3.7 ± 2.7% (mean ± standard deviation), 18.6 ± 1.8%, 52.8 ± 3.7%, 77.8 ± 14.8% and 100 ± 0%. Geometrical distortions occurred around the center of the high-grade stenosis and led to higher standard deviations compared to lower grade stenoses. In the frame of this study the MPI signal depended linearly on the SPION concentration down to 0.05 mmol (Fe)/l. Conclusion Near real-time MPI accurately visualized and quantified different stenosis grades in vascular phantoms.

• Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas Franich, Robert A.; Meder, Roger; Behr, Volker C. in Molecules (2020). 25(22) 5367.
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  Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO2 volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.

  @article{franich2020dewatering, abstract = {Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO2 volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.}, author = {Franich, Robert A. and Meder, Roger and Behr, Volker C.}, journal = {Molecules}, keywords = {peer}, month = 11, number = 22, pages = 5367, title = {Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas}, volume = 25, year = 2020 }

  %0 Journal Article %1 franich2020dewatering %A Franich, Robert A. %A Meder, Roger %A Behr, Volker C. %D 2020 %J Molecules %N 22 %P 5367 %R 10.3390/molecules25225367 %T Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas %V 25 %X Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO2 volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.
• Adjustable Hardware Lens for Traveling Wave Magnetic Particle Imaging Vogel, P.; Kampf, T.; Herz, S.; Rückert, M. A.; Bley, T. A.; Behr, V. C. in IEEE Trans. Magn. (2020). 56(11) 5300506.
  • [ Abstract ]
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  Magnetic Particle Imaging (MPI) is a promising tomographic technique for fast and sensitive visualization of superparamagnetic iron-oxide nanoparticles (SPIONs). Different types of MPI scanners have been presented in the past providing 2D as well as 3D data with different sizes of the field of view (FOV). With increasing FOVs, often the spatial resolution decreases. Traveling Wave MPI scanners provide the possibility to visualize the entire available FOV within the scanner at once with a good spatial resolution and a high temporal resolution. However, a more selective imaging process, such as scanning specific areas within the sample collecting more information, is of high interest. This can be performed by adjusting the sequences for signal acquisition, e.g., by modulation of the amplitude, to actively suppress signal generation in specific areas. Unfortunately, this method requires adaptation of the hardware. In this manuscript a novel approach for imaging specific areas within the FOV of a Traveling Wave MPI scanner is presented without specific hardware modifications. Furthermore, this technique offers the possibility to increase the resolution by up to 40 %, which reveals more details in this area, similar to a magnification effect.

  @article{vogel2020adjustable, abstract = {Magnetic Particle Imaging (MPI) is a promising tomographic technique for fast and sensitive visualization of superparamagnetic iron-oxide nanoparticles (SPIONs). Different types of MPI scanners have been presented in the past providing 2D as well as 3D data with different sizes of the field of view (FOV). With increasing FOVs, often the spatial resolution decreases. Traveling Wave MPI scanners provide the possibility to visualize the entire available FOV within the scanner at once with a good spatial resolution and a high temporal resolution. However, a more selective imaging process, such as scanning specific areas within the sample collecting more information, is of high interest. This can be performed by adjusting the sequences for signal acquisition, e.g., by modulation of the amplitude, to actively suppress signal generation in specific areas. Unfortunately, this method requires adaptation of the hardware. In this manuscript a novel approach for imaging specific areas within the FOV of a Traveling Wave MPI scanner is presented without specific hardware modifications. Furthermore, this technique offers the possibility to increase the resolution by up to 40 %, which reveals more details in this area, similar to a magnification effect.}, author = {Vogel, P. and Kampf, T. and Herz, S. and Rückert, M. A. and Bley, T. A. and Behr, V. C.}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 11, number = 11, pages = 5300506, title = {Adjustable Hardware Lens for Traveling Wave Magnetic Particle Imaging}, volume = 56, year = 2020 }

  %0 Journal Article %1 vogel2020adjustable %A Vogel, P. %A Kampf, T. %A Herz, S. %A Rückert, M. A. %A Bley, T. A. %A Behr, V. C. %D 2020 %J IEEE Trans. Magn. %N 11 %P 5300506 %R 10.1109/TMAG.2020.3023686 %T Adjustable Hardware Lens for Traveling Wave Magnetic Particle Imaging %V 56 %X Magnetic Particle Imaging (MPI) is a promising tomographic technique for fast and sensitive visualization of superparamagnetic iron-oxide nanoparticles (SPIONs). Different types of MPI scanners have been presented in the past providing 2D as well as 3D data with different sizes of the field of view (FOV). With increasing FOVs, often the spatial resolution decreases. Traveling Wave MPI scanners provide the possibility to visualize the entire available FOV within the scanner at once with a good spatial resolution and a high temporal resolution. However, a more selective imaging process, such as scanning specific areas within the sample collecting more information, is of high interest. This can be performed by adjusting the sequences for signal acquisition, e.g., by modulation of the amplitude, to actively suppress signal generation in specific areas. Unfortunately, this method requires adaptation of the hardware. In this manuscript a novel approach for imaging specific areas within the FOV of a Traveling Wave MPI scanner is presented without specific hardware modifications. Furthermore, this technique offers the possibility to increase the resolution by up to 40 %, which reveals more details in this area, similar to a magnification effect.
• A dynamic bolus phantom for the evaluation of the spatio-temporal resolution of MPI scanners Dutz, Silvio; Stang, Anton; Wöckel, Lucas; Kosch, Olaf; Vogel, Patrick; Behr, Volker C.; Wiekhorst, Frank in J. Magn. Magn. Mater. (2020). 519 167446.
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  Magnetic particle imaging (MPI) is a tomographic imaging method to determine the spatial distribution of magnetic nanoparticles (MNP) within a defined volume. To evaluate the spatio-temporal resolution of existing MPI scanners, enabling the consistent comparison of the performance of different scanner setups, we developed dynamic MPI measurement phantoms based on segmented flow. These segmented flow phantoms comprise a defined bolus of ferrofluid tracer material, which can be pumped through a tube system with defined velocities. Using a hydrophobic organic carrier oil, cylindrically shaped boluses of different diameter, length, and flow velocity can be emulated. Moving boluses were imaged by different MPI scanner types and the correlation of spatial resolution und velocity of the bolus was investigated. For all bolus dimension and flow velocity combinations investigated, we observed a decreasing spatial resolution and increasing blurring for increasing bolus velocity and decreasing bolus volume.

  @article{dutz2020dynamic, abstract = {Magnetic particle imaging (MPI) is a tomographic imaging method to determine the spatial distribution of magnetic nanoparticles (MNP) within a defined volume. To evaluate the spatio-temporal resolution of existing MPI scanners, enabling the consistent comparison of the performance of different scanner setups, we developed dynamic MPI measurement phantoms based on segmented flow. These segmented flow phantoms comprise a defined bolus of ferrofluid tracer material, which can be pumped through a tube system with defined velocities. Using a hydrophobic organic carrier oil, cylindrically shaped boluses of different diameter, length, and flow velocity can be emulated. Moving boluses were imaged by different MPI scanner types and the correlation of spatial resolution und velocity of the bolus was investigated. For all bolus dimension and flow velocity combinations investigated, we observed a decreasing spatial resolution and increasing blurring for increasing bolus velocity and decreasing bolus volume.}, author = {Dutz, Silvio and Stang, Anton and Wöckel, Lucas and Kosch, Olaf and Vogel, Patrick and Behr, Volker C. and Wiekhorst, Frank}, journal = {J. Magn. Magn. Mater.}, keywords = {peer}, month = 10, pages = 167446, title = {A dynamic bolus phantom for the evaluation of the spatio-temporal resolution of MPI scanners}, volume = 519, year = 2020 }

  %0 Journal Article %1 dutz2020dynamic %A Dutz, Silvio %A Stang, Anton %A Wöckel, Lucas %A Kosch, Olaf %A Vogel, Patrick %A Behr, Volker C. %A Wiekhorst, Frank %D 2020 %J J. Magn. Magn. Mater. %P 167446 %R 10.1016/j.jmmm.2020.167446 %T A dynamic bolus phantom for the evaluation of the spatio-temporal resolution of MPI scanners %V 519 %X Magnetic particle imaging (MPI) is a tomographic imaging method to determine the spatial distribution of magnetic nanoparticles (MNP) within a defined volume. To evaluate the spatio-temporal resolution of existing MPI scanners, enabling the consistent comparison of the performance of different scanner setups, we developed dynamic MPI measurement phantoms based on segmented flow. These segmented flow phantoms comprise a defined bolus of ferrofluid tracer material, which can be pumped through a tube system with defined velocities. Using a hydrophobic organic carrier oil, cylindrically shaped boluses of different diameter, length, and flow velocity can be emulated. Moving boluses were imaged by different MPI scanner types and the correlation of spatial resolution und velocity of the bolus was investigated. For all bolus dimension and flow velocity combinations investigated, we observed a decreasing spatial resolution and increasing blurring for increasing bolus velocity and decreasing bolus volume.
• Novel Fabrication Method for Nested Saddle Coils Vogel, P.; Kampf, T.; Rückert, M. A.; Behr, V. C. in IEEE Trans. Magn. (2020). 56(9) 1–6.
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  The generation and measurement of static and time-varying magnetic fields using electromagnetic coils is a common method in various fields. Multiple applications require special geometries, e.g., complex structures on curved surfaces. The fabrication of such complex saddle coils on curved surfaces without special equipment is challenging and requires time-consuming techniques and lot of experience to produce coils with high accuracy. The novel approach uses dedicated slits in a tubular structure to guide and self-fixate the windings of the desired coil structure and allows a fast and easy fabrication with high accuracy and without special skills. In this article, an introduction into the basic idea is given followed by a generalization for arbitrary nested saddle-coil structures. Finally, a first 3-D printed prototype is presented.

  @article{vogel2020novel, abstract = {The generation and measurement of static and time-varying magnetic fields using electromagnetic coils is a common method in various fields. Multiple applications require special geometries, e.g., complex structures on curved surfaces. The fabrication of such complex saddle coils on curved surfaces without special equipment is challenging and requires time-consuming techniques and lot of experience to produce coils with high accuracy. The novel approach uses dedicated slits in a tubular structure to guide and self-fixate the windings of the desired coil structure and allows a fast and easy fabrication with high accuracy and without special skills. In this article, an introduction into the basic idea is given followed by a generalization for arbitrary nested saddle-coil structures. Finally, a first 3-D printed prototype is presented.}, author = {Vogel, P. and Kampf, T. and Rückert, M. A. and Behr, V. C.}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 9, number = 9, pages = {1-6}, title = {Novel Fabrication Method for Nested Saddle Coils}, volume = 56, year = 2020 }

  %0 Journal Article %1 vogel2020novel %A Vogel, P. %A Kampf, T. %A Rückert, M. A. %A Behr, V. C. %D 2020 %J IEEE Trans. Magn. %N 9 %P 1-6 %R 10.1109/TMAG.2020.3007358 %T Novel Fabrication Method for Nested Saddle Coils %V 56 %X The generation and measurement of static and time-varying magnetic fields using electromagnetic coils is a common method in various fields. Multiple applications require special geometries, e.g., complex structures on curved surfaces. The fabrication of such complex saddle coils on curved surfaces without special equipment is challenging and requires time-consuming techniques and lot of experience to produce coils with high accuracy. The novel approach uses dedicated slits in a tubular structure to guide and self-fixate the windings of the desired coil structure and allows a fast and easy fabrication with high accuracy and without special skills. In this article, an introduction into the basic idea is given followed by a generalization for arbitrary nested saddle-coil structures. Finally, a first 3-D printed prototype is presented.
• Wall shear stress analysis using 17.6 Tesla MRI: A longitudinal study in ApoE-/- mice with histological analysis Riedl, Katharina A.; Kampf, Thomas; Herold, Volker; Behr, Volker C.; Bauer, Wolfgang R. in PLOS ONE (2020). 15(8) 1–13.
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  This longitudinal study was performed to evaluate the feasibility of detecting the interaction between wall shear stress (WSS) and plaque development. 20 ApoE-/- mice were separated in 12 mice with Western Diet and 8 mice with Chow Diet. Magnetic resonance (MR) scans at 17.6 Tesla and histological analysis were performed after one week, eight and twelve weeks. All in vivo MR measurements were acquired using a flow sensitive phase contrast method for determining vectorial flow. Histological sections were stained with Hematoxylin and Eosin, Elastica van Gieson and CD68 staining. Data analysis was performed using Ensight and a Matlab-based “Flow Tool”. The body weight of ApoE-/- mice increased significantly over 12 weeks. WSS values increased in the Western Diet group over the time period; in contrast, in the Chow Diet group the values decreased from the first to the second measurement point. Western Diet mice showed small plaque formations with elastin fragmentations after 8 weeks and big plaque formations after 12 weeks; Chow Diet mice showed a few elastin fragmentations after 8 weeks and small plaque formations after 12 weeks. Favored by high-fat diet, plaque formation results in higher values of WSS. With wall shear stress being a known predictor for atherosclerotic plaque development, ultra highfield MRI can serve as a tool for studying the causes and beginnings of atherosclerosis.

  @article{riedl2020shear, abstract = {This longitudinal study was performed to evaluate the feasibility of detecting the interaction between wall shear stress (WSS) and plaque development. 20 ApoE-/- mice were separated in 12 mice with Western Diet and 8 mice with Chow Diet. Magnetic resonance (MR) scans at 17.6 Tesla and histological analysis were performed after one week, eight and twelve weeks. All in vivo MR measurements were acquired using a flow sensitive phase contrast method for determining vectorial flow. Histological sections were stained with Hematoxylin and Eosin, Elastica van Gieson and CD68 staining. Data analysis was performed using Ensight and a Matlab-based “Flow Tool”. The body weight of ApoE-/- mice increased significantly over 12 weeks. WSS values increased in the Western Diet group over the time period; in contrast, in the Chow Diet group the values decreased from the first to the second measurement point. Western Diet mice showed small plaque formations with elastin fragmentations after 8 weeks and big plaque formations after 12 weeks; Chow Diet mice showed a few elastin fragmentations after 8 weeks and small plaque formations after 12 weeks. Favored by high-fat diet, plaque formation results in higher values of WSS. With wall shear stress being a known predictor for atherosclerotic plaque development, ultra highfield MRI can serve as a tool for studying the causes and beginnings of atherosclerosis.}, author = {Riedl, Katharina A. and Kampf, Thomas and Herold, Volker and Behr, Volker C. and Bauer, Wolfgang R.}, journal = {PLOS ONE}, keywords = {peer}, month = {08}, number = 8, pages = {1-13}, publisher = {Public Library of Science}, title = {Wall shear stress analysis using 17.6 Tesla MRI: A longitudinal study in ApoE-/- mice with histological analysis}, volume = 15, year = 2020 }

  %0 Journal Article %1 riedl2020shear %A Riedl, Katharina A. %A Kampf, Thomas %A Herold, Volker %A Behr, Volker C. %A Bauer, Wolfgang R. %D 2020 %I Public Library of Science %J PLOS ONE %N 8 %P 1-13 %R 10.1371/journal.pone.0238112 %T Wall shear stress analysis using 17.6 Tesla MRI: A longitudinal study in ApoE-/- mice with histological analysis %V 15 %X This longitudinal study was performed to evaluate the feasibility of detecting the interaction between wall shear stress (WSS) and plaque development. 20 ApoE-/- mice were separated in 12 mice with Western Diet and 8 mice with Chow Diet. Magnetic resonance (MR) scans at 17.6 Tesla and histological analysis were performed after one week, eight and twelve weeks. All in vivo MR measurements were acquired using a flow sensitive phase contrast method for determining vectorial flow. Histological sections were stained with Hematoxylin and Eosin, Elastica van Gieson and CD68 staining. Data analysis was performed using Ensight and a Matlab-based “Flow Tool”. The body weight of ApoE-/- mice increased significantly over 12 weeks. WSS values increased in the Western Diet group over the time period; in contrast, in the Chow Diet group the values decreased from the first to the second measurement point. Western Diet mice showed small plaque formations with elastin fragmentations after 8 weeks and big plaque formations after 12 weeks; Chow Diet mice showed a few elastin fragmentations after 8 weeks and small plaque formations after 12 weeks. Favored by high-fat diet, plaque formation results in higher values of WSS. With wall shear stress being a known predictor for atherosclerotic plaque development, ultra highfield MRI can serve as a tool for studying the causes and beginnings of atherosclerosis.
• Parallel magnetic particle imaging Vogel, Patrick; Kampf, Thomas; Herz, Stefan; Rückert, Martin A.; Bley, Thorsten A.; Behr, Volker C. in Rev. Sci. Instrum. (2020). 91(4) 045117.
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  Magnetic Particle Imaging (MPI) is a promising tomographic method to visualize the distribution of superparamagnetic materials in three-dimensions. For encoding, a strong gradient represented by a field free point (FFP) or a field free line (FFL) is steered rapidly through the field of view (FOV), acquiring the signal successively. Conventional MPI scanners only provide a single FFP or FFL to sample the entire scan volume, which limits the size of the FOV and/or the temporal resolution. The alternative scanner concept of Traveling Wave MPI (TWMPI) uses a dynamic linear gradient array (dLGA) for dynamic FFP generation along the symmetry axis. The TWMPI scanner is capable of creating multiple FFPs simultaneously, and usually care is taken to locate only a single FFP in the desired FOV. In this manuscript, the concept of parallel MPI utilizing multiple FFPs simultaneously is introduced. For that, conceptual simulations are presented followed by reconstruction approaches for visualization of parallel MPI signals. In addition, an initial parallel MPI experiment with simultaneous acquisition of signals from two FFPs inside the FOV of the same scanner using two receive chains is demonstrated. This allows scanning a doubled FOV within the same acquisition time without sacrificing resolution compared to the standard TWMPI scanner.

  @article{vogel2020parallel, abstract = {Magnetic Particle Imaging (MPI) is a promising tomographic method to visualize the distribution of superparamagnetic materials in three-dimensions. For encoding, a strong gradient represented by a field free point (FFP) or a field free line (FFL) is steered rapidly through the field of view (FOV), acquiring the signal successively. Conventional MPI scanners only provide a single FFP or FFL to sample the entire scan volume, which limits the size of the FOV and/or the temporal resolution. The alternative scanner concept of Traveling Wave MPI (TWMPI) uses a dynamic linear gradient array (dLGA) for dynamic FFP generation along the symmetry axis. The TWMPI scanner is capable of creating multiple FFPs simultaneously, and usually care is taken to locate only a single FFP in the desired FOV. In this manuscript, the concept of parallel MPI utilizing multiple FFPs simultaneously is introduced. For that, conceptual simulations are presented followed by reconstruction approaches for visualization of parallel MPI signals. In addition, an initial parallel MPI experiment with simultaneous acquisition of signals from two FFPs inside the FOV of the same scanner using two receive chains is demonstrated. This allows scanning a doubled FOV within the same acquisition time without sacrificing resolution compared to the standard TWMPI scanner.}, author = {Vogel, Patrick and Kampf, Thomas and Herz, Stefan and Rückert, Martin A. and Bley, Thorsten A. and Behr, Volker C.}, journal = {Rev. Sci. Instrum.}, keywords = {peer}, month = 4, number = 4, pages = {045117}, publisher = {American Institute of Physics}, title = {Parallel magnetic particle imaging}, volume = 91, year = 2020 }

  %0 Journal Article %1 vogel2020parallel %A Vogel, Patrick %A Kampf, Thomas %A Herz, Stefan %A Rückert, Martin A. %A Bley, Thorsten A. %A Behr, Volker C. %D 2020 %I American Institute of Physics %J Rev. Sci. Instrum. %N 4 %P 045117 %R 10.1063/1.5126108 %T Parallel magnetic particle imaging %V 91 %X Magnetic Particle Imaging (MPI) is a promising tomographic method to visualize the distribution of superparamagnetic materials in three-dimensions. For encoding, a strong gradient represented by a field free point (FFP) or a field free line (FFL) is steered rapidly through the field of view (FOV), acquiring the signal successively. Conventional MPI scanners only provide a single FFP or FFL to sample the entire scan volume, which limits the size of the FOV and/or the temporal resolution. The alternative scanner concept of Traveling Wave MPI (TWMPI) uses a dynamic linear gradient array (dLGA) for dynamic FFP generation along the symmetry axis. The TWMPI scanner is capable of creating multiple FFPs simultaneously, and usually care is taken to locate only a single FFP in the desired FOV. In this manuscript, the concept of parallel MPI utilizing multiple FFPs simultaneously is introduced. For that, conceptual simulations are presented followed by reconstruction approaches for visualization of parallel MPI signals. In addition, an initial parallel MPI experiment with simultaneous acquisition of signals from two FFPs inside the FOV of the same scanner using two receive chains is demonstrated. This allows scanning a doubled FOV within the same acquisition time without sacrificing resolution compared to the standard TWMPI scanner.
• Crosslinked Coating Improves the Signal-to-Noise Ratio of Iron Oxide Nanoparticles in Magnetic Particle Imaging (MPI) Horvat, Sonja; Vogel, Patrick; Kampf, Thomas; Brandl, Andreas; Alshamsan, Aws; Alhadlaq, Hisham A.; Ahamed, Maqusood; Albrecht, Krystyna; Behr, Volker C.; Beilhack, Andreas; Groll, Jürgen in Chem. Nano. Mat. (2020). 6(5) 755–758.
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  Magnetic particle imaging is an emerging tomographic method used for evaluation of the spatial distribution of iron‐oxide nanoparticles. In this work, the effect of the polymer coating on the response of particles was studied. Particles with covalently crosslinked coating showed improved signal and image resolution.

  @article{horvat2020crosslinked, abstract = {Magnetic particle imaging is an emerging tomographic method used for evaluation of the spatial distribution of iron‐oxide nanoparticles. In this work, the effect of the polymer coating on the response of particles was studied. Particles with covalently crosslinked coating showed improved signal and image resolution.}, author = {Horvat, Sonja and Vogel, Patrick and Kampf, Thomas and Brandl, Andreas and Alshamsan, Aws and Alhadlaq, Hisham A. and Ahamed, Maqusood and Albrecht, Krystyna and Behr, Volker C. and Beilhack, Andreas and Groll, Jürgen}, journal = {Chem. Nano. Mat.}, keywords = {peer}, month = 4, number = 5, pages = {755-758}, publisher = {Wiley}, title = {Crosslinked Coating Improves the Signal-to-Noise Ratio of Iron Oxide Nanoparticles in Magnetic Particle Imaging (MPI)}, volume = 6, year = 2020 }

  %0 Journal Article %1 horvat2020crosslinked %A Horvat, Sonja %A Vogel, Patrick %A Kampf, Thomas %A Brandl, Andreas %A Alshamsan, Aws %A Alhadlaq, Hisham A. %A Ahamed, Maqusood %A Albrecht, Krystyna %A Behr, Volker C. %A Beilhack, Andreas %A Groll, Jürgen %D 2020 %I Wiley %J Chem. Nano. Mat. %N 5 %P 755-758 %R 10.1002/cnma.202000009 %T Crosslinked Coating Improves the Signal-to-Noise Ratio of Iron Oxide Nanoparticles in Magnetic Particle Imaging (MPI) %V 6 %X Magnetic particle imaging is an emerging tomographic method used for evaluation of the spatial distribution of iron‐oxide nanoparticles. In this work, the effect of the polymer coating on the response of particles was studied. Particles with covalently crosslinked coating showed improved signal and image resolution.
• Tree Species Identification via 1H NMR Fingerprinting of Supercritical Carbon Dioxide Wood Extractives Raymond, Laura G.; Sandquist, David; Hill, Stefan J.; Meder, Roger; Behr, Volker C. in BioResources (2020). 15(2) 2371–2384.
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  Six tree species were examined using 1H NMR spectroscopy of sap extracted by supercritical CO2. A metabolomic approach was developed to evaluate the sap extracted from sapwood of Norway spruce (Picea abies), Sitka spruce (Picea sitchensis), radiata pine (Pinus radiata), macrocarpa (Cupressus macrocarpa), and two Eucalyptus species—shining gum and mountain ash (Eucalyptus nitens and Eucalyptus regnans. The sap extraction patterns in the different species were visualised using 1H magnetic resonance imaging. In softwoods with distinct annual rings, water was first removed from the latewood bands, and then gradually from the earlywood bands. In the case of the hardwood species an almost random water redistribution, rather than water expulsion, was observed. Analysis of the principal component analysis loading plots showed that the significant differences in the sap between each species were due to the carbohydrate region. Key discriminators were identified as pinitol, sucrose, glucose, and fructose.

  @article{raymond2020species, abstract = {Six tree species were examined using 1H NMR spectroscopy of sap extracted by supercritical CO2. A metabolomic approach was developed to evaluate the sap extracted from sapwood of Norway spruce (Picea abies), Sitka spruce (Picea sitchensis), radiata pine (Pinus radiata), macrocarpa (Cupressus macrocarpa), and two Eucalyptus species—shining gum and mountain ash (Eucalyptus nitens and Eucalyptus regnans. The sap extraction patterns in the different species were visualised using 1H magnetic resonance imaging. In softwoods with distinct annual rings, water was first removed from the latewood bands, and then gradually from the earlywood bands. In the case of the hardwood species an almost random water redistribution, rather than water expulsion, was observed. Analysis of the principal component analysis loading plots showed that the significant differences in the sap between each species were due to the carbohydrate region. Key discriminators were identified as pinitol, sucrose, glucose, and fructose.}, author = {Raymond, Laura G. and Sandquist, David and Hill, Stefan J. and Meder, Roger and Behr, Volker C.}, journal = {BioResources}, keywords = {peer}, month = 2, number = 2, pages = {2371-2384}, title = {Tree Species Identification via 1H NMR Fingerprinting of Supercritical Carbon Dioxide Wood Extractives}, volume = 15, year = 2020 }

  %0 Journal Article %1 raymond2020species %A Raymond, Laura G. %A Sandquist, David %A Hill, Stefan J. %A Meder, Roger %A Behr, Volker C. %D 2020 %J BioResources %N 2 %P 2371-2384 %T Tree Species Identification via 1H NMR Fingerprinting of Supercritical Carbon Dioxide Wood Extractives %U https://bioresources.cnr.ncsu.edu/wp-content/uploads/2020/02/BioRes_15_2_2371_Raymond_SHMB_Tree_Sp_ID_H_NMR_Fingerprinting_Extracts_Wood_Supercritical_CO2_Extrac_16159.pdf %V 15 %X Six tree species were examined using 1H NMR spectroscopy of sap extracted by supercritical CO2. A metabolomic approach was developed to evaluate the sap extracted from sapwood of Norway spruce (Picea abies), Sitka spruce (Picea sitchensis), radiata pine (Pinus radiata), macrocarpa (Cupressus macrocarpa), and two Eucalyptus species—shining gum and mountain ash (Eucalyptus nitens and Eucalyptus regnans. The sap extraction patterns in the different species were visualised using 1H magnetic resonance imaging. In softwoods with distinct annual rings, water was first removed from the latewood bands, and then gradually from the earlywood bands. In the case of the hardwood species an almost random water redistribution, rather than water expulsion, was observed. Analysis of the principal component analysis loading plots showed that the significant differences in the sap between each species were due to the carbohydrate region. Key discriminators were identified as pinitol, sucrose, glucose, and fructose.
• Superspeed Bolus Visualization for Vascular Magnetic Particle Imaging Vogel, Patrick; Rückert, Martin A.; Kampf, Thomas; Herz, Stefan; Stang, Anton; Wöckel, Lucas; Bley, Thorsten A.; Dutz, Silvio; Behr, Volker C. in IEEE Trans. Med. Imag. (2020). 39(6) 2133–2139.
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  Magnetic Particle Imaging (MPI) is a fast imaging technique to visualize the distribution of superparamagnetic iron-oxide nanoparticles (SPIONs). For spatial encoding, a field free area is moved rapidly through the field of view (FOV) generating localized signal. Fast moving samples, e.g., a bolus of SPIONs traveling through the large veins in the human body carried by blood flow with velocities in the order of ~45 cm/s, cause temporal blurring in MPI measurements using common sequences and reconstruction techniques. This hampers the evaluation of dynamics of fast moving samples. In this manuscript, a first study on fast moving samples visualized within an MPI scanner is demonstrated. By optimizing parameters for imaging and reconstruction, the dynamics of a fast moving bolus at different velocities can be visualized with high temporal resolution without blurring artifacts.

  @article{vogel2020superspeed, abstract = {Magnetic Particle Imaging (MPI) is a fast imaging technique to visualize the distribution of superparamagnetic iron-oxide nanoparticles (SPIONs). For spatial encoding, a field free area is moved rapidly through the field of view (FOV) generating localized signal. Fast moving samples, e.g., a bolus of SPIONs traveling through the large veins in the human body carried by blood flow with velocities in the order of  45 cm/s, cause temporal blurring in MPI measurements using common sequences and reconstruction techniques. This hampers the evaluation of dynamics of fast moving samples. In this manuscript, a first study on fast moving samples visualized within an MPI scanner is demonstrated. By optimizing parameters for imaging and reconstruction, the dynamics of a fast moving bolus at different velocities can be visualized with high temporal resolution without blurring artifacts.}, author = {Vogel, Patrick and Rückert, Martin A. and Kampf, Thomas and Herz, Stefan and Stang, Anton and Wöckel, Lucas and Bley, Thorsten A. and Dutz, Silvio and Behr, Volker C.}, journal = {IEEE Trans. Med. Imag.}, keywords = {peer}, month = 1, number = 6, pages = {2133-2139}, title = {Superspeed Bolus Visualization for Vascular Magnetic Particle Imaging}, volume = 39, year = 2020 }

  %0 Journal Article %1 vogel2020superspeed %A Vogel, Patrick %A Rückert, Martin A. %A Kampf, Thomas %A Herz, Stefan %A Stang, Anton %A Wöckel, Lucas %A Bley, Thorsten A. %A Dutz, Silvio %A Behr, Volker C. %D 2020 %J IEEE Trans. Med. Imag. %N 6 %P 2133-2139 %R 10.1109/TMI.2020.2965724 %T Superspeed Bolus Visualization for Vascular Magnetic Particle Imaging %V 39 %X Magnetic Particle Imaging (MPI) is a fast imaging technique to visualize the distribution of superparamagnetic iron-oxide nanoparticles (SPIONs). For spatial encoding, a field free area is moved rapidly through the field of view (FOV) generating localized signal. Fast moving samples, e.g., a bolus of SPIONs traveling through the large veins in the human body carried by blood flow with velocities in the order of ~45 cm/s, cause temporal blurring in MPI measurements using common sequences and reconstruction techniques. This hampers the evaluation of dynamics of fast moving samples. In this manuscript, a first study on fast moving samples visualized within an MPI scanner is demonstrated. By optimizing parameters for imaging and reconstruction, the dynamics of a fast moving bolus at different velocities can be visualized with high temporal resolution without blurring artifacts.

• Micro-Traveling Wave Magnetic Particle Imaging - Sub-Millimeter Resolution With Optimized Tracer LS-008 Vogel, P.; Rückert, M.A.; Kemp, S.J.; Khandhar, A.P.; Ferguson, R.M.; Herz, S.; Vilter, A.; Klauer, P.; Bley, T.A.; Krishnan, K.M.; Behr, V.C. in IEEE Trans. Magn. (2019). 55(10) 5300207.
  • [ Abstract ]
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  Magnetic particle imaging (MPI) is a novel tomographic imaging method, which allows determining the distribution of superparamagnetic iron-oxide nanoparticles in three dimensions. So far, various MPI systems have been presented with each one emphasizing different scanner features such as large field of view (FOV) or high resolution. For imaging with both high resolution and a large FOV, the optimization and harmonization of hardware parameters as well as tracer material are key prerequisites. The traveling wave MPI (TWMPI) approach uses an array of electromagnets, which can provide a high magnetic field gradient for a high resolution as well as a mouse-sized FOV at the same time. In combination with the tracer LS-008, which is optimized for the MPI technique, a resolution in the sub-millimeter range can be achieved. In this paper, an optimized scanner is presented based on the TWMPI approach featuring a gradient strength up to almost 10 T/m in an FOV with a length of 45 mm providing a high resolution below 500 microns using the optimized LS-008 tracer.

  @article{vogel2019microtraveling, abstract = {Magnetic particle imaging (MPI) is a novel tomographic imaging method, which allows determining the distribution of superparamagnetic iron-oxide nanoparticles in three dimensions. So far, various MPI systems have been presented with each one emphasizing different scanner features such as large field of view (FOV) or high resolution. For imaging with both high resolution and a large FOV, the optimization and harmonization of hardware parameters as well as tracer material are key prerequisites. The traveling wave MPI (TWMPI) approach uses an array of electromagnets, which can provide a high magnetic field gradient for a high resolution as well as a mouse-sized FOV at the same time. In combination with the tracer LS-008, which is optimized for the MPI technique, a resolution in the sub-millimeter range can be achieved. In this paper, an optimized scanner is presented based on the TWMPI approach featuring a gradient strength up to almost 10 T/m in an FOV with a length of 45 mm providing a high resolution below 500 microns using the optimized LS-008 tracer.}, author = {Vogel, P. and Rückert, M.A. and Kemp, S.J. and Khandhar, A.P. and Ferguson, R.M. and Herz, S. and Vilter, A. and Klauer, P. and Bley, T.A. and Krishnan, K.M. and Behr, V.C.}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 10, number = 10, pages = 5300207, title = {Micro-Traveling Wave Magnetic Particle Imaging - Sub-Millimeter Resolution With Optimized Tracer LS-008}, volume = 55, year = 2019 }

  %0 Journal Article %1 vogel2019microtraveling %A Vogel, P. %A Rückert, M.A. %A Kemp, S.J. %A Khandhar, A.P. %A Ferguson, R.M. %A Herz, S. %A Vilter, A. %A Klauer, P. %A Bley, T.A. %A Krishnan, K.M. %A Behr, V.C. %D 2019 %J IEEE Trans. Magn. %N 10 %P 5300207 %R 10.1109/TMAG.2019.2924198 %T Micro-Traveling Wave Magnetic Particle Imaging - Sub-Millimeter Resolution With Optimized Tracer LS-008 %V 55 %X Magnetic particle imaging (MPI) is a novel tomographic imaging method, which allows determining the distribution of superparamagnetic iron-oxide nanoparticles in three dimensions. So far, various MPI systems have been presented with each one emphasizing different scanner features such as large field of view (FOV) or high resolution. For imaging with both high resolution and a large FOV, the optimization and harmonization of hardware parameters as well as tracer material are key prerequisites. The traveling wave MPI (TWMPI) approach uses an array of electromagnets, which can provide a high magnetic field gradient for a high resolution as well as a mouse-sized FOV at the same time. In combination with the tracer LS-008, which is optimized for the MPI technique, a resolution in the sub-millimeter range can be achieved. In this paper, an optimized scanner is presented based on the TWMPI approach featuring a gradient strength up to almost 10 T/m in an FOV with a length of 45 mm providing a high resolution below 500 microns using the optimized LS-008 tracer.
• Magnetic Particle Imaging meets Computed Tomography: first simultaneous imaging Vogel, Patrick; Markert, Jonathan; Rückert, Martin A.; Herz, Stefan; Keßler, Benedikt; Dremel, Kilian; Althoff, Daniel; Weber, Matthias; Buzug, Thorsten M.; Bley, Thorsten A.; Kullmann, Walter H.; Hanke, Randolf; Zabler, Simon; Behr, Volker C. in Sci. Rep. (2019). 9(1) 12627.
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  Magnetic Particle Imaging (MPI) is a promising new tomographic modality for fast as well as three-dimensional visualization of magnetic material. For anatomical or structural information an additional imaging modality such as computed tomography (CT) is required. In this paper, the first hybrid MPI-CT scanner for multimodal imaging providing simultaneous data acquisition is presented.

  @article{vogel2019magnetic, abstract = {Magnetic Particle Imaging (MPI) is a promising new tomographic modality for fast as well as three-dimensional visualization of magnetic material. For anatomical or structural information an additional imaging modality such as computed tomography (CT) is required. In this paper, the first hybrid MPI-CT scanner for multimodal imaging providing simultaneous data acquisition is presented.}, author = {Vogel, Patrick and Markert, Jonathan and Rückert, Martin A. and Herz, Stefan and Keßler, Benedikt and Dremel, Kilian and Althoff, Daniel and Weber, Matthias and Buzug, Thorsten M. and Bley, Thorsten A. and Kullmann, Walter H. and Hanke, Randolf and Zabler, Simon and Behr, Volker C.}, journal = {Sci. Rep.}, keywords = {peer}, month = 9, number = 1, pages = 12627, title = {Magnetic Particle Imaging meets Computed Tomography: first simultaneous imaging}, volume = 9, year = 2019 }

  %0 Journal Article %1 vogel2019magnetic %A Vogel, Patrick %A Markert, Jonathan %A Rückert, Martin A. %A Herz, Stefan %A Keßler, Benedikt %A Dremel, Kilian %A Althoff, Daniel %A Weber, Matthias %A Buzug, Thorsten M. %A Bley, Thorsten A. %A Kullmann, Walter H. %A Hanke, Randolf %A Zabler, Simon %A Behr, Volker C. %D 2019 %J Sci. Rep. %N 1 %P 12627 %R 10.1038/s41598-019-48960-1 %T Magnetic Particle Imaging meets Computed Tomography: first simultaneous imaging %V 9 %X Magnetic Particle Imaging (MPI) is a promising new tomographic modality for fast as well as three-dimensional visualization of magnetic material. For anatomical or structural information an additional imaging modality such as computed tomography (CT) is required. In this paper, the first hybrid MPI-CT scanner for multimodal imaging providing simultaneous data acquisition is presented.
• Magnetic Particle Imaging-Guided Stenting Herz, Stefan; Vogel, Patrick; Kampf, Thomas; Dietrich, Philipp; Veldhoen, Simon; Rückert, Martin A.; Kickuth, Ralph; Behr, Volker C.; Bley, Thorsten A. in J. Endovasc. Ther. (2019). 26(4) 512–519.
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  Purpose: To assess the feasibility of magnetic particle imaging (MPI) to guide stenting in a phantom model. Materials and Methods: MPI is a new tomographic imaging method based on the background-free magnetic field detection of a tracer agent composed of superparamagnetic iron oxide nanoparticles (SPIOs). All experiments were conducted on a custom-built MPI scanner (field of view: 29-mm diameter, 65-mm length; isotropic spatial resolution 1–1.5-mm). Stenosis phantoms (n=3) consisted of polyvinyl chloride (PVC) tubes (8-mm inner diameter) prepared with centrally aligned cable binders to form a ~50% stenosis. A dedicated image reconstruction algorithm allowed precise tracking of endovascular instruments at 8 frames/s with a latency time of ~115 ms. A custom-made MPI-visible lacquer was used to manually label conventional guidewires, balloon catheters, and stainless steel balloon-expandable stents. Vascular stenoses were visualized by injecting a diluted SPIO tracer (ferucarbotran, 10 mmol iron/L) into the vessel phantoms. Balloon angioplasty and stent placement were performed by inflating balloon catheters and stent delivery balloons with diluted ferucarbotran. Results: After deployment of the stent, the markers on its ends were clearly visible. The applied lacquer markers were thin enough to not relevantly alter gliding properties of the devices while withstanding friction during the experiments. Placing an optimized flexible lacquer formulation on the preexisting radiopaque stent markers provided enough stability to withstand stent expansion. Final MPA confirmed successful stenosis treatment, facilitated by the disappearance of the lacquer markers on the stent due to differences in SPIO concentration. Thus, the in-stent lumen could be visualized without interference by the signal from the markers. Conclusion: Near real-time visualization of MPI-guided stenting of stenoses in a phantom model is feasible. Optimized MPI-visible markers can withstand the expansion process of stents.

  @article{herz2019magnetic, abstract = {Purpose: To assess the feasibility of magnetic particle imaging (MPI) to guide stenting in a phantom model. Materials and Methods: MPI is a new tomographic imaging method based on the background-free magnetic field detection of a tracer agent composed of superparamagnetic iron oxide nanoparticles (SPIOs). All experiments were conducted on a custom-built MPI scanner (field of view: 29-mm diameter, 65-mm length; isotropic spatial resolution 1–1.5-mm). Stenosis phantoms (n=3) consisted of polyvinyl chloride (PVC) tubes (8-mm inner diameter) prepared with centrally aligned cable binders to form a  50% stenosis. A dedicated image reconstruction algorithm allowed precise tracking of endovascular instruments at 8 frames/s with a latency time of  115 ms. A custom-made MPI-visible lacquer was used to manually label conventional guidewires, balloon catheters, and stainless steel balloon-expandable stents. Vascular stenoses were visualized by injecting a diluted SPIO tracer (ferucarbotran, 10 mmol iron/L) into the vessel phantoms. Balloon angioplasty and stent placement were performed by inflating balloon catheters and stent delivery balloons with diluted ferucarbotran. Results: After deployment of the stent, the markers on its ends were clearly visible. The applied lacquer markers were thin enough to not relevantly alter gliding properties of the devices while withstanding friction during the experiments. Placing an optimized flexible lacquer formulation on the preexisting radiopaque stent markers provided enough stability to withstand stent expansion. Final MPA confirmed successful stenosis treatment, facilitated by the disappearance of the lacquer markers on the stent due to differences in SPIO concentration. Thus, the in-stent lumen could be visualized without interference by the signal from the markers. Conclusion: Near real-time visualization of MPI-guided stenting of stenoses in a phantom model is feasible. Optimized MPI-visible markers can withstand the expansion process of stents.}, author = {Herz, Stefan and Vogel, Patrick and Kampf, Thomas and Dietrich, Philipp and Veldhoen, Simon and Rückert, Martin A. and Kickuth, Ralph and Behr, Volker C. and Bley, Thorsten A.}, journal = {J. Endovasc. Ther.}, keywords = {peer}, month = 8, number = 4, pages = {512-519}, title = {Magnetic Particle Imaging-Guided Stenting}, volume = 26, year = 2019 }

  %0 Journal Article %1 herz2019magnetic %A Herz, Stefan %A Vogel, Patrick %A Kampf, Thomas %A Dietrich, Philipp %A Veldhoen, Simon %A Rückert, Martin A. %A Kickuth, Ralph %A Behr, Volker C. %A Bley, Thorsten A. %D 2019 %J J. Endovasc. Ther. %N 4 %P 512-519 %R 10.1177/1526602819851202 %T Magnetic Particle Imaging-Guided Stenting %V 26 %X Purpose: To assess the feasibility of magnetic particle imaging (MPI) to guide stenting in a phantom model. Materials and Methods: MPI is a new tomographic imaging method based on the background-free magnetic field detection of a tracer agent composed of superparamagnetic iron oxide nanoparticles (SPIOs). All experiments were conducted on a custom-built MPI scanner (field of view: 29-mm diameter, 65-mm length; isotropic spatial resolution 1–1.5-mm). Stenosis phantoms (n=3) consisted of polyvinyl chloride (PVC) tubes (8-mm inner diameter) prepared with centrally aligned cable binders to form a ~50% stenosis. A dedicated image reconstruction algorithm allowed precise tracking of endovascular instruments at 8 frames/s with a latency time of ~115 ms. A custom-made MPI-visible lacquer was used to manually label conventional guidewires, balloon catheters, and stainless steel balloon-expandable stents. Vascular stenoses were visualized by injecting a diluted SPIO tracer (ferucarbotran, 10 mmol iron/L) into the vessel phantoms. Balloon angioplasty and stent placement were performed by inflating balloon catheters and stent delivery balloons with diluted ferucarbotran. Results: After deployment of the stent, the markers on its ends were clearly visible. The applied lacquer markers were thin enough to not relevantly alter gliding properties of the devices while withstanding friction during the experiments. Placing an optimized flexible lacquer formulation on the preexisting radiopaque stent markers provided enough stability to withstand stent expansion. Final MPA confirmed successful stenosis treatment, facilitated by the disappearance of the lacquer markers on the stent due to differences in SPIO concentration. Thus, the in-stent lumen could be visualized without interference by the signal from the markers. Conclusion: Near real-time visualization of MPI-guided stenting of stenoses in a phantom model is feasible. Optimized MPI-visible markers can withstand the expansion process of stents.
• Uncovering supercritical CO2 wood dewatering via interleaved 1H-imaging and 13C-spectroscopy with real-time reconstruction Franich, Robert A.; Meder, Roger; Falge, Mirjam; Fuchs, Johannes; Behr, Volker C. in J. Supercrit. Fluids (2019). 144 56–62.
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  Real-time observation of green radiata pine sapwood specimens undergoing dewatering using a cyclical process in which supercritical CO2 changes to gas phase has been achieved using rapid interleaved 1H magnetic resonance imaging (MRI) and 13C nuclear magnetic resonance (NMR) spectroscopy. The 1H and 13C data were produced as videos showing in real-time changes in cell water distribution within the wood specimen together with the water flow from the specimen undergoing dewatering, and changes in CO213C NMR spectrum with pressure change and CO2 phase change. The results presented here enable refinement of understanding of the green wood dewatering mechanism driven by phase change of supercritical CO2 to gas, and provide insights into the physical and chemical interaction of supercritical CO2 and wood cell water.

  @article{franich2019uncovering, abstract = {Real-time observation of green radiata pine sapwood specimens undergoing dewatering using a cyclical process in which supercritical CO2 changes to gas phase has been achieved using rapid interleaved 1H magnetic resonance imaging (MRI) and 13C nuclear magnetic resonance (NMR) spectroscopy. The 1H and 13C data were produced as videos showing in real-time changes in cell water distribution within the wood specimen together with the water flow from the specimen undergoing dewatering, and changes in CO213C NMR spectrum with pressure change and CO2 phase change. The results presented here enable refinement of understanding of the green wood dewatering mechanism driven by phase change of supercritical CO2 to gas, and provide insights into the physical and chemical interaction of supercritical CO2 and wood cell water.}, author = {Franich, Robert A. and Meder, Roger and Falge, Mirjam and Fuchs, Johannes and Behr, Volker C.}, journal = {J. Supercrit. Fluids}, keywords = {peer}, month = 2, pages = {56-62}, title = {Uncovering supercritical CO2 wood dewatering via interleaved 1H-imaging and 13C-spectroscopy with real-time reconstruction}, volume = 144, year = 2019 }

  %0 Journal Article %1 franich2019uncovering %A Franich, Robert A. %A Meder, Roger %A Falge, Mirjam %A Fuchs, Johannes %A Behr, Volker C. %D 2019 %J J. Supercrit. Fluids %P 56-62 %R 10.1016/j.supflu.2018.10.006 %T Uncovering supercritical CO2 wood dewatering via interleaved 1H-imaging and 13C-spectroscopy with real-time reconstruction %V 144 %X Real-time observation of green radiata pine sapwood specimens undergoing dewatering using a cyclical process in which supercritical CO2 changes to gas phase has been achieved using rapid interleaved 1H magnetic resonance imaging (MRI) and 13C nuclear magnetic resonance (NMR) spectroscopy. The 1H and 13C data were produced as videos showing in real-time changes in cell water distribution within the wood specimen together with the water flow from the specimen undergoing dewatering, and changes in CO213C NMR spectrum with pressure change and CO2 phase change. The results presented here enable refinement of understanding of the green wood dewatering mechanism driven by phase change of supercritical CO2 to gas, and provide insights into the physical and chemical interaction of supercritical CO2 and wood cell water.

• Novel Field Geometry UsingTwo Halbach Cylinders for FFL-MPI Weber, Matthias; Beuke, Jonas; von Gladiss, Anselm; Gräfe, Ksenija; Vogel, Patrick; Behr, Volker C.; Buzug, Thorsten M. in Int. J. Magn. Part. Imag. (2018). 4(2) 1811004.
  • [ Abstract ]
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  Magnetic Particle Imaging (MPI) offers several methods for encoding magnetic materials in three-dimensions. The complexity of the imaging device in MPI using a field free line (FFL) is the biggest challenge in realizing such devices. This is especially the case for systems featuring large bores, high gradients or high temporal resolution. In this work, we suggest a novel Halbach cylinder based field generator that is able to generate an FFL with a gradient of 5 T/m. By rotating the Halbach array, FFL projections can be acquired. Furthermore, just one static drive field coil is needed for two-dimensional imaging. The presented concept could combine high gradient strength and high temporal resolution with minimum space requirements for FFL-MPI imaging in the future.

  @article{weber2018novel, abstract = {Magnetic Particle Imaging (MPI) offers several methods for encoding magnetic materials in three-dimensions. The complexity of the imaging device in MPI using a field free line (FFL) is the biggest challenge in realizing such devices. This is especially the case for systems featuring large bores, high gradients or high temporal resolution. In this work, we suggest a novel Halbach cylinder based field generator that is able to generate an FFL with a gradient of 5 T/m. By rotating the Halbach array, FFL projections can be acquired. Furthermore, just one static drive field coil is needed for two-dimensional imaging. The presented concept could combine high gradient strength and high temporal resolution with minimum space requirements for FFL-MPI imaging in the future.}, author = {Weber, Matthias and Beuke, Jonas and von Gladiss, Anselm and Gräfe, Ksenija and Vogel, Patrick and Behr, Volker C. and Buzug, Thorsten M.}, journal = {Int. J. Magn. Part. Imag.}, keywords = {peer}, month = 11, number = 2, pages = 1811004, title = {Novel Field Geometry UsingTwo Halbach Cylinders for FFL-MPI}, volume = 4, year = 2018 }

  %0 Journal Article %1 weber2018novel %A Weber, Matthias %A Beuke, Jonas %A von Gladiss, Anselm %A Gräfe, Ksenija %A Vogel, Patrick %A Behr, Volker C. %A Buzug, Thorsten M. %D 2018 %J Int. J. Magn. Part. Imag. %N 2 %P 1811004 %R 10.18416/ijmpi.2018.1811004 %T Novel Field Geometry UsingTwo Halbach Cylinders for FFL-MPI %V 4 %X Magnetic Particle Imaging (MPI) offers several methods for encoding magnetic materials in three-dimensions. The complexity of the imaging device in MPI using a field free line (FFL) is the biggest challenge in realizing such devices. This is especially the case for systems featuring large bores, high gradients or high temporal resolution. In this work, we suggest a novel Halbach cylinder based field generator that is able to generate an FFL with a gradient of 5 T/m. By rotating the Halbach array, FFL projections can be acquired. Furthermore, just one static drive field coil is needed for two-dimensional imaging. The presented concept could combine high gradient strength and high temporal resolution with minimum space requirements for FFL-MPI imaging in the future.
• Magnetic Particle Imaging Guided Real-Time Percutaneous Transluminal Angioplasty in a Phantom Model Herz, Stefan; Vogel, Patrick; Dietrich, Philipp; Kampf, Thomas; R{\"u}ckert, Martin A.; Kickuth, Ralph; Behr, Volker C.; Bley, Thorsten A. in Cardiovasc. Intervent. Radiol. (2018). 41(7) 1100–1105.
  • [ Abstract ]
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  Purpose: To investigate the potential of real-time magnetic particle imaging (MPI) to guide percutaneous transluminal angioplasty (PTA) of vascular stenoses in a phantom model. Materials and Methods: Experiments were conducted on a custom-built MPI scanner. Vascular stenosis phantoms consisted of polyvinyl chloride tubes (inner diameter 8 mm) prepared with a centrally aligned cable tie to form ~ 50% stenoses. MPI angiography for visualization of stenoses was performed using the superparamagnetic iron oxide nanoparticle-based contrast agent Ferucarbotran (10 mmol (Fe)/l). Balloon catheters and guidewires for PTA were visualized using custom-made lacquer markers based on Ferucarbotran. Stenosis dilation (n = 3) was performed by manually inflating the PTA balloon with diluted Ferucarbotran. An online reconstruction framework was implemented for real-time imaging with very short latency time. Results: Visualization of stenosis phantoms and guidance of interventional instruments in real-time (4 frames/s, ~ 100 ms latency time) was possible using an online reconstruction algorithm. Labeling of guidewires and balloon catheters allowed for precise visualization of instrument positions. Conclusion: Real-time MPI-guided PTA in a phantom model is feasible.

  @article{herz2018magnetic, abstract = {Purpose: To investigate the potential of real-time magnetic particle imaging (MPI) to guide percutaneous transluminal angioplasty (PTA) of vascular stenoses in a phantom model. Materials and Methods: Experiments were conducted on a custom-built MPI scanner. Vascular stenosis phantoms consisted of polyvinyl chloride tubes (inner diameter 8 mm) prepared with a centrally aligned cable tie to form   50% stenoses. MPI angiography for visualization of stenoses was performed using the superparamagnetic iron oxide nanoparticle-based contrast agent Ferucarbotran (10 mmol (Fe)/l). Balloon catheters and guidewires for PTA were visualized using custom-made lacquer markers based on Ferucarbotran. Stenosis dilation (n = 3) was performed by manually inflating the PTA balloon with diluted Ferucarbotran. An online reconstruction framework was implemented for real-time imaging with very short latency time. Results: Visualization of stenosis phantoms and guidance of interventional instruments in real-time (4 frames/s,   100 ms latency time) was possible using an online reconstruction algorithm. Labeling of guidewires and balloon catheters allowed for precise visualization of instrument positions. Conclusion: Real-time MPI-guided PTA in a phantom model is feasible.}, author = {Herz, Stefan and Vogel, Patrick and Dietrich, Philipp and Kampf, Thomas and R{\"u}ckert, Martin A. and Kickuth, Ralph and Behr, Volker C. and Bley, Thorsten A.}, journal = {Cardiovasc. Intervent. Radiol.}, keywords = {peer}, month = 7, number = 7, pages = {1100-1105}, title = {Magnetic Particle Imaging Guided Real-Time Percutaneous Transluminal Angioplasty in a Phantom Model}, volume = 41, year = 2018 }

  %0 Journal Article %1 herz2018magnetic %A Herz, Stefan %A Vogel, Patrick %A Dietrich, Philipp %A Kampf, Thomas %A R{\"u}ckert, Martin A. %A Kickuth, Ralph %A Behr, Volker C. %A Bley, Thorsten A. %D 2018 %J Cardiovasc. Intervent. Radiol. %N 7 %P 1100-1105 %R 10.1007/s00270-018-1955-7 %T Magnetic Particle Imaging Guided Real-Time Percutaneous Transluminal Angioplasty in a Phantom Model %V 41 %X Purpose: To investigate the potential of real-time magnetic particle imaging (MPI) to guide percutaneous transluminal angioplasty (PTA) of vascular stenoses in a phantom model. Materials and Methods: Experiments were conducted on a custom-built MPI scanner. Vascular stenosis phantoms consisted of polyvinyl chloride tubes (inner diameter 8 mm) prepared with a centrally aligned cable tie to form ~ 50% stenoses. MPI angiography for visualization of stenoses was performed using the superparamagnetic iron oxide nanoparticle-based contrast agent Ferucarbotran (10 mmol (Fe)/l). Balloon catheters and guidewires for PTA were visualized using custom-made lacquer markers based on Ferucarbotran. Stenosis dilation (n = 3) was performed by manually inflating the PTA balloon with diluted Ferucarbotran. An online reconstruction framework was implemented for real-time imaging with very short latency time. Results: Visualization of stenosis phantoms and guidance of interventional instruments in real-time (4 frames/s, ~ 100 ms latency time) was possible using an online reconstruction algorithm. Labeling of guidewires and balloon catheters allowed for precise visualization of instrument positions. Conclusion: Real-time MPI-guided PTA in a phantom model is feasible.
• Dynamic Linear Gradient Array for Traveling Wave Magnetic Particle Imaging Vogel, Patrick; Klauer, Peter; Rückert, Martin A.; Bley, Thorsten A.; Kullmann, Walter H.; Jakob, Peter M.; Behr, Volker C. in IEEE Trans. Magn. (2018). 54(2) 5300109.
  • [ Abstract ]
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  Magnetic particle imaging (MPI) is a young imaging modality using the nonlinear magnetization properties of superparamagnetic iron-oxide nanoparticles to acquire them. It is a highly sensitive and fast method allowing both a quantitative and a qualitative analysis of the measured signal. Since its first publication in 2005, several different scanner types have been presented. Most of them work with permanent magnets and therefore have a small field of view. In 2014, an alternative scanner concept, the traveling wave MPI (TWMPI), was presented, which allows scanning an entire mouse-sized volume at once. In this paper, a detailed description of the main field generator, the dynamic linear gradient array (dLGA), used for TWMPI is given. This paper guides the reader to the first dLGA prototype, deriving relations between the length of the dLGA and the diameter of the segment coils.

  @article{vogel2018dynamic, abstract = {Magnetic particle imaging (MPI) is a young imaging modality using the nonlinear magnetization properties of superparamagnetic iron-oxide nanoparticles to acquire them. It is a highly sensitive and fast method allowing both a quantitative and a qualitative analysis of the measured signal. Since its first publication in 2005, several different scanner types have been presented. Most of them work with permanent magnets and therefore have a small field of view. In 2014, an alternative scanner concept, the traveling wave MPI (TWMPI), was presented, which allows scanning an entire mouse-sized volume at once. In this paper, a detailed description of the main field generator, the dynamic linear gradient array (dLGA), used for TWMPI is given. This paper guides the reader to the first dLGA prototype, deriving relations between the length of the dLGA and the diameter of the segment coils.}, author = {Vogel, Patrick and Klauer, Peter and Rückert, Martin A. and Bley, Thorsten A. and Kullmann, Walter H. and Jakob, Peter M. and Behr, Volker C.}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 2, number = 2, pages = 5300109, title = {Dynamic Linear Gradient Array for Traveling Wave Magnetic Particle Imaging}, volume = 54, year = 2018 }

  %0 Journal Article %1 vogel2018dynamic %A Vogel, Patrick %A Klauer, Peter %A Rückert, Martin A. %A Bley, Thorsten A. %A Kullmann, Walter H. %A Jakob, Peter M. %A Behr, Volker C. %D 2018 %J IEEE Trans. Magn. %N 2 %P 5300109 %R 10.1109/TMAG.2017.2764440 %T Dynamic Linear Gradient Array for Traveling Wave Magnetic Particle Imaging %V 54 %X Magnetic particle imaging (MPI) is a young imaging modality using the nonlinear magnetization properties of superparamagnetic iron-oxide nanoparticles to acquire them. It is a highly sensitive and fast method allowing both a quantitative and a qualitative analysis of the measured signal. Since its first publication in 2005, several different scanner types have been presented. Most of them work with permanent magnets and therefore have a small field of view. In 2014, an alternative scanner concept, the traveling wave MPI (TWMPI), was presented, which allows scanning an entire mouse-sized volume at once. In this paper, a detailed description of the main field generator, the dynamic linear gradient array (dLGA), used for TWMPI is given. This paper guides the reader to the first dLGA prototype, deriving relations between the length of the dLGA and the diameter of the segment coils.
• Magnetic Particle Imaging for Quantification of Vascular Stenoses: A Phantom Study Herz, Stefan; Vogel, Patrick; Kampf, Thomas; Rückert, Martin A.; Veldhoen, Simon; Behr, Volker C.; Bley, Thorsten A. in IEEE Trans. Med. Imag. (2018). 37(1) 61–67.
  • [ Abstract ]
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  Magnetic particle imaging (MPI) is a promising new tomographic imaging method to detect the spatial distribution of superparamagnetic iron-oxide nanoparticles (SPIOs). The aim of this paper was to investigate the potential of MPI to quantify artificial stenoses in vessel phantoms. Custom-made stenosis phantoms (length 40 mm; inner diameter 8 mm) with different degrees of stenosis (0%, 25%, 50%, 75%, and 100%) were scanned in a custom-built MPI scanner (in-plane resolution: ~1–1.5 mm and field of view: 65 × 29 × 29 mm3). Phantoms were filled with diluted Feru-carbotran [SPIO agent, 5 mmol (Fe)/l]. Each measurement (overall acquisition time: 20 ms per image, 400 averages) was repeated ten times to assess reproducibility. The MPI signal was used for semi-automatic stenosis quantification. Two stenosis evaluation approaches were compared based on the signal intensity profile alongside the stenosis phantoms. Using a novel multi-step image evaluation approach, MPI allowed for accurate quantification of different stenosis grades. While low grade stenoses were slightly over-estimated, high grade stenoses were slightly underestimated. In particular, the 0%, 25%, and 50% stenosis phantoms revealed a 6.2% ± 0.8, 25.7% ± 1.0, and 48.0% ± 1.5 stenosis, respectively. The higher grade 75% stenosis phantom revealed a 73.3% ± 2.8 and the 100% stenosis phantom a 95.8% ± 1.9 stenosis. MPI accurately visualized and quantified different stenosis grades in vessel phantoms with high reproducibility demonstrating its great potential for fast and radiation-free preclinical cardiovascular imaging.

  @article{herz2018magnetic, abstract = {Magnetic particle imaging (MPI) is a promising new tomographic imaging method to detect the spatial distribution of superparamagnetic iron-oxide nanoparticles (SPIOs). The aim of this paper was to investigate the potential of MPI to quantify artificial stenoses in vessel phantoms. Custom-made stenosis phantoms (length 40 mm; inner diameter 8 mm) with different degrees of stenosis (0%, 25%, 50%, 75%, and 100%) were scanned in a custom-built MPI scanner (in-plane resolution:  1–1.5 mm and field of view: 65 × 29 × 29 mm3). Phantoms were filled with diluted Feru-carbotran [SPIO agent, 5 mmol (Fe)/l]. Each measurement (overall acquisition time: 20 ms per image, 400 averages) was repeated ten times to assess reproducibility. The MPI signal was used for semi-automatic stenosis quantification. Two stenosis evaluation approaches were compared based on the signal intensity profile alongside the stenosis phantoms. Using a novel multi-step image evaluation approach, MPI allowed for accurate quantification of different stenosis grades. While low grade stenoses were slightly over-estimated, high grade stenoses were slightly underestimated. In particular, the 0%, 25%, and 50% stenosis phantoms revealed a 6.2% ± 0.8, 25.7% ± 1.0, and 48.0% ± 1.5 stenosis, respectively. The higher grade 75% stenosis phantom revealed a 73.3% ± 2.8 and the 100% stenosis phantom a 95.8% ± 1.9 stenosis. MPI accurately visualized and quantified different stenosis grades in vessel phantoms with high reproducibility demonstrating its great potential for fast and radiation-free preclinical cardiovascular imaging.}, author = {Herz, Stefan and Vogel, Patrick and Kampf, Thomas and Rückert, Martin A. and Veldhoen, Simon and Behr, Volker C. and Bley, Thorsten A.}, journal = {IEEE Trans. Med. Imag.}, keywords = {peer}, month = 1, number = 1, pages = {61-67}, title = {Magnetic Particle Imaging for Quantification of Vascular Stenoses: A Phantom Study}, volume = 37, year = 2018 }

  %0 Journal Article %1 herz2018magnetic %A Herz, Stefan %A Vogel, Patrick %A Kampf, Thomas %A Rückert, Martin A. %A Veldhoen, Simon %A Behr, Volker C. %A Bley, Thorsten A. %D 2018 %J IEEE Trans. Med. Imag. %N 1 %P 61-67 %R 10.1109/TMI.2017.2717958 %T Magnetic Particle Imaging for Quantification of Vascular Stenoses: A Phantom Study %V 37 %X Magnetic particle imaging (MPI) is a promising new tomographic imaging method to detect the spatial distribution of superparamagnetic iron-oxide nanoparticles (SPIOs). The aim of this paper was to investigate the potential of MPI to quantify artificial stenoses in vessel phantoms. Custom-made stenosis phantoms (length 40 mm; inner diameter 8 mm) with different degrees of stenosis (0%, 25%, 50%, 75%, and 100%) were scanned in a custom-built MPI scanner (in-plane resolution: ~1–1.5 mm and field of view: 65 × 29 × 29 mm3). Phantoms were filled with diluted Feru-carbotran [SPIO agent, 5 mmol (Fe)/l]. Each measurement (overall acquisition time: 20 ms per image, 400 averages) was repeated ten times to assess reproducibility. The MPI signal was used for semi-automatic stenosis quantification. Two stenosis evaluation approaches were compared based on the signal intensity profile alongside the stenosis phantoms. Using a novel multi-step image evaluation approach, MPI allowed for accurate quantification of different stenosis grades. While low grade stenoses were slightly over-estimated, high grade stenoses were slightly underestimated. In particular, the 0%, 25%, and 50% stenosis phantoms revealed a 6.2% ± 0.8, 25.7% ± 1.0, and 48.0% ± 1.5 stenosis, respectively. The higher grade 75% stenosis phantom revealed a 73.3% ± 2.8 and the 100% stenosis phantom a 95.8% ± 1.9 stenosis. MPI accurately visualized and quantified different stenosis grades in vessel phantoms with high reproducibility demonstrating its great potential for fast and radiation-free preclinical cardiovascular imaging.

• Selective Signal Suppression in Traveling Wave MPI: Focusing on Areas with Low Concentration of Magnetic Particles Herz, Stefan; Vogel, Patrick; Kampf, Thomas; Rückert, Martin A.; Behr, Volker C.; Bley, Thorsten A. in Int. J. Magn. Part. Imag. (2017). 3(2) 1709001.
  • [ Abstract ]
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  Introduction: Common MPI scanners have difficulties to correctly visualize areas with a broad signal intensity spectrum due to their low signal dynamic capability. The aim of this study was to develop a selective signal suppression technique using an advanced trajectory design to circumvent this issue. Materials and Methods: Simulations where performed for a traveling wave (TW) MPI scanner. In the so called slice-scanning mode the field free points (FFPs) travel through the scanner on a sinusoidal trajectory given by the frequencies of the dynamic linear gradient array and a perpendicular saddle coil system. The signal can be selectively suppressed by locally reducing the speed of the FFPs. Series of measurements with two point samples containing different SPIO concentrations with and without selective signal suppression technique were simulated. Results: When imaging samples with two markedly different SPIO concentrations in the slice-scanning mode the signal of the lower concentration cannot be properly reconstructed. Applying the signal suppression technique to the area of the high concentration sample selectively reduces this signal and demarcates samples with lower concentrations. Conclusion: A selective signal suppression technique for TWMPI is introduced which allows to focus on low SPIO concentrations in samples with a large range of tracer concentrations. This can facilitate preclinical functional imaging in the proximity of organs with high unspecific SPIO uptake such as the liver.

  @article{herz2017selective, abstract = {Introduction: Common MPI scanners have difficulties to correctly visualize areas with a broad signal intensity spectrum due to their low signal dynamic capability. The aim of this study was to develop a selective signal suppression technique using an advanced trajectory design to circumvent this issue. Materials and Methods: Simulations where performed for a traveling wave (TW) MPI scanner. In the so called slice-scanning mode the field free points (FFPs) travel through the scanner on a sinusoidal trajectory given by the frequencies of the dynamic linear gradient array and a perpendicular saddle coil system. The signal can be selectively suppressed by locally reducing the speed of the FFPs. Series of measurements with two point samples containing different SPIO concentrations with and without selective signal suppression technique were simulated. Results: When imaging samples with two markedly different SPIO concentrations in the slice-scanning mode the signal of the lower concentration cannot be properly reconstructed. Applying the signal suppression technique to the area of the high concentration sample selectively reduces this signal and demarcates samples with lower concentrations. Conclusion: A selective signal suppression technique for TWMPI is introduced which allows to focus on low SPIO concentrations in samples with a large range of tracer concentrations. This can facilitate preclinical functional imaging in the proximity of organs with high unspecific SPIO uptake such as the liver.}, author = {Herz, Stefan and Vogel, Patrick and Kampf, Thomas and Rückert, Martin A. and Behr, Volker C. and Bley, Thorsten A.}, journal = {Int. J. Magn. Part. Imag.}, keywords = {peer}, month = 9, number = 2, pages = 1709001, title = {Selective Signal Suppression in Traveling Wave MPI: Focusing on Areas with Low Concentration of Magnetic Particles}, volume = 3, year = 2017 }

  %0 Journal Article %1 herz2017selective %A Herz, Stefan %A Vogel, Patrick %A Kampf, Thomas %A Rückert, Martin A. %A Behr, Volker C. %A Bley, Thorsten A. %D 2017 %J Int. J. Magn. Part. Imag. %N 2 %P 1709001 %R 10.18416/ijmpi.2017.1709001 %T Selective Signal Suppression in Traveling Wave MPI: Focusing on Areas with Low Concentration of Magnetic Particles %V 3 %X Introduction: Common MPI scanners have difficulties to correctly visualize areas with a broad signal intensity spectrum due to their low signal dynamic capability. The aim of this study was to develop a selective signal suppression technique using an advanced trajectory design to circumvent this issue. Materials and Methods: Simulations where performed for a traveling wave (TW) MPI scanner. In the so called slice-scanning mode the field free points (FFPs) travel through the scanner on a sinusoidal trajectory given by the frequencies of the dynamic linear gradient array and a perpendicular saddle coil system. The signal can be selectively suppressed by locally reducing the speed of the FFPs. Series of measurements with two point samples containing different SPIO concentrations with and without selective signal suppression technique were simulated. Results: When imaging samples with two markedly different SPIO concentrations in the slice-scanning mode the signal of the lower concentration cannot be properly reconstructed. Applying the signal suppression technique to the area of the high concentration sample selectively reduces this signal and demarcates samples with lower concentrations. Conclusion: A selective signal suppression technique for TWMPI is introduced which allows to focus on low SPIO concentrations in samples with a large range of tracer concentrations. This can facilitate preclinical functional imaging in the proximity of organs with high unspecific SPIO uptake such as the liver.
• Low Latency Real-time Reconstruction for MPI Systems Vogel, Patrick; Herz, Stefan; Kampf, Thomas; Rückert, Martin A.; Bley, Thorsten A.; Behr, Volker C. in Int. J. Magn. Part. Imag. (2017). 3(2) 1707002.
  • [ Abstract ]
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  • [ DOI ]
  In the last decade research in the Magnetic Particle Imaging community focused mainly on hardware development as well as the optimization of reconstruction. These steps were essential for improving MPI technology and advance it to pre-clinical applications. However, another important part is the software package working behind MPI systems. This software has to be able to keep up with modern scanner features and should be able to support features such as adjustable scanning trajectories or multiple reconstruction methods. Especially a real-time reconstruction feature is important to use the full potential of the fast imaging capabilities of modern MPI scanners. This could be pivotal in applications such as guided vascular interventions. In this work, a software package is presented, which improves reconstructing MPI data with different reconstruction methods in real-time and with low latency.

  @article{vogel2017latency, abstract = {In the last decade research in the Magnetic Particle Imaging community focused mainly on hardware development as well as the optimization of reconstruction. These steps were essential for improving MPI technology and advance it to pre-clinical applications. However, another important part is the software package working behind MPI systems. This software has to be able to keep up with modern scanner features and should be able to support features such as adjustable scanning trajectories or multiple reconstruction methods. Especially a real-time reconstruction feature is important to use the full potential of the fast imaging capabilities of modern MPI scanners. This could be pivotal in applications such as guided vascular interventions. In this work, a software package is presented, which improves reconstructing MPI data with different reconstruction methods in real-time and with low latency.}, author = {Vogel, Patrick and Herz, Stefan and Kampf, Thomas and Rückert, Martin A. and Bley, Thorsten A. and Behr, Volker C.}, journal = {Int. J. Magn. Part. Imag.}, keywords = {peer}, month = 7, number = 2, pages = 1707002, title = {Low Latency Real-time Reconstruction for MPI Systems}, volume = 3, year = 2017 }

  %0 Journal Article %1 vogel2017latency %A Vogel, Patrick %A Herz, Stefan %A Kampf, Thomas %A Rückert, Martin A. %A Bley, Thorsten A. %A Behr, Volker C. %D 2017 %J Int. J. Magn. Part. Imag. %N 2 %P 1707002 %R 10.18416/ijmpi.2017.1707002 %T Low Latency Real-time Reconstruction for MPI Systems %V 3 %X In the last decade research in the Magnetic Particle Imaging community focused mainly on hardware development as well as the optimization of reconstruction. These steps were essential for improving MPI technology and advance it to pre-clinical applications. However, another important part is the software package working behind MPI systems. This software has to be able to keep up with modern scanner features and should be able to support features such as adjustable scanning trajectories or multiple reconstruction methods. Especially a real-time reconstruction feature is important to use the full potential of the fast imaging capabilities of modern MPI scanners. This could be pivotal in applications such as guided vascular interventions. In this work, a software package is presented, which improves reconstructing MPI data with different reconstruction methods in real-time and with low latency.
• Real-time 3D Dynamic Rotating Slice-Scanning Mode for Traveling Wave MPI Vogel, Patrick; Rückert, Martin A.; Klauer, Peter; Herz, Stefan; Kampf, Thomas; Bley, Thorsten; Behr, Volker C. in Int. J. Magn. Part. Imag. (2017). 3(2) 1706001.
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  Magnetic Particle Imaging is a tomographic imaging technique offering high sensitivity and temporal resolution and is a promising tool for pre-clinical applications. The state of the art Traveling Wave Magnetic Particle Imaging (TWMPI) scanners offer a mouse-sized FOV, which can be scanned at once. Since the first introduction of TWMPI, several sequences have been introduced to scan the FOV in 2D as well as 3D. So far, the proposed 3D sequences do not provide real-time capability, which is an important feature for future clinical applications such as guided vascular interventions. In this study a modified sequence for TWMPI scanners is presented, which allows scanning an entire 3D volume on a short time scale. Furthermore, for real-time capability a novel reconstruction method using an image-based approach is used providing a 3D visualization in real-time.

  @article{vogel2017realtime, abstract = {Magnetic Particle Imaging is a tomographic imaging technique offering high sensitivity and temporal resolution and is a promising tool for pre-clinical applications. The state of the art Traveling Wave Magnetic Particle Imaging (TWMPI) scanners offer a mouse-sized FOV, which can be scanned at once. Since the first introduction of TWMPI, several sequences have been introduced to scan the FOV in 2D as well as 3D. So far, the proposed 3D sequences do not provide real-time capability, which is an important feature for future clinical applications such as guided vascular interventions. In this study a modified sequence for TWMPI scanners is presented, which allows scanning an entire 3D volume on a short time scale. Furthermore, for real-time capability a novel reconstruction method using an image-based approach is used providing a 3D visualization in real-time.}, author = {Vogel, Patrick and Rückert, Martin A. and Klauer, Peter and Herz, Stefan and Kampf, Thomas and Bley, Thorsten and Behr, Volker C.}, journal = {Int. J. Magn. Part. Imag.}, keywords = {peer}, month = 6, number = 2, pages = 1706001, title = {Real-time 3D Dynamic Rotating Slice-Scanning Mode for Traveling Wave MPI}, volume = 3, year = 2017 }

  %0 Journal Article %1 vogel2017realtime %A Vogel, Patrick %A Rückert, Martin A. %A Klauer, Peter %A Herz, Stefan %A Kampf, Thomas %A Bley, Thorsten %A Behr, Volker C. %D 2017 %J Int. J. Magn. Part. Imag. %N 2 %P 1706001 %R 10.18416/ijmpi.2017.1706001 %T Real-time 3D Dynamic Rotating Slice-Scanning Mode for Traveling Wave MPI %V 3 %X Magnetic Particle Imaging is a tomographic imaging technique offering high sensitivity and temporal resolution and is a promising tool for pre-clinical applications. The state of the art Traveling Wave Magnetic Particle Imaging (TWMPI) scanners offer a mouse-sized FOV, which can be scanned at once. Since the first introduction of TWMPI, several sequences have been introduced to scan the FOV in 2D as well as 3D. So far, the proposed 3D sequences do not provide real-time capability, which is an important feature for future clinical applications such as guided vascular interventions. In this study a modified sequence for TWMPI scanners is presented, which allows scanning an entire 3D volume on a short time scale. Furthermore, for real-time capability a novel reconstruction method using an image-based approach is used providing a 3D visualization in real-time.

• Flexible and Dynamic Patch Reconstruction for Traveling Wave Magnetic Particle Imaging Vogel, Patrick; Kampf, Thomas; Rückert, Martin Andreas; Behr, Volker Christian in Int. J. Magn. Part. Imag. (2016). 2(2) 1611001.
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  Different types of scanners have been presented since the first publication of Magnetic Particle Imaging (MPI) in 2005. As a result, there are different types of reconstruction methods available, which can be separated into two basic concepts: reconstruction using a system matrix and reconstruction using a direct deconvolution. Both methods have their merits and drawbacks. For the first approach hardware parameters like sampling rate and frequencies have to be chosen carefully to fit the parameter selection process required for the system matrix. For the other approach the temporal and spatial homogeneity of the magnetic field gradient over the entire FOV has to be high to perform an accurate reconstruction, which results in smaller FOVs. In this paper a novel reconstruction method is presented, which combines the advantages of both reconstruction methods to be more flexible during the entire reconstruction process. Furthermore, it enables the possibility of performing a dynamic patch reconstruction, which allows to select arbitrary areas of the FOV for higher resolution reducing reconstruction time significantly. In addition, this new reconstruction improved the image quality of a Traveling Wave MPI scanner substantially.

  @article{vogel2016flexible, abstract = {Different types of scanners have been presented since the first publication of Magnetic Particle Imaging (MPI) in 2005. As a result, there are different types of reconstruction methods available, which can be separated into two basic concepts: reconstruction using a system matrix and reconstruction using a direct deconvolution. Both methods have their merits and drawbacks. For the first approach hardware parameters like sampling rate and frequencies have to be chosen carefully to fit the parameter selection process required for the system matrix. For the other approach the temporal and spatial homogeneity of the magnetic field gradient over the entire FOV has to be high to perform an accurate reconstruction, which results in smaller FOVs. In this paper a novel reconstruction method is presented, which combines the advantages of both reconstruction methods to be more flexible during the entire reconstruction process. Furthermore, it enables the possibility of performing a dynamic patch reconstruction, which allows to select arbitrary areas of the FOV for higher resolution reducing reconstruction time significantly. In addition, this new reconstruction improved the image quality of a Traveling Wave MPI scanner substantially.}, author = {Vogel, Patrick and Kampf, Thomas and Rückert, Martin Andreas and Behr, Volker Christian}, journal = {Int. J. Magn. Part. Imag.}, keywords = {peer}, month = 11, number = 2, pages = 1611001, title = {Flexible and Dynamic Patch Reconstruction for Traveling Wave Magnetic Particle Imaging}, volume = 2, year = 2016 }

  %0 Journal Article %1 vogel2016flexible %A Vogel, Patrick %A Kampf, Thomas %A Rückert, Martin Andreas %A Behr, Volker Christian %D 2016 %J Int. J. Magn. Part. Imag. %N 2 %P 1611001 %R 10.18416/ijmpi.2016.1611001 %T Flexible and Dynamic Patch Reconstruction for Traveling Wave Magnetic Particle Imaging %V 2 %X Different types of scanners have been presented since the first publication of Magnetic Particle Imaging (MPI) in 2005. As a result, there are different types of reconstruction methods available, which can be separated into two basic concepts: reconstruction using a system matrix and reconstruction using a direct deconvolution. Both methods have their merits and drawbacks. For the first approach hardware parameters like sampling rate and frequencies have to be chosen carefully to fit the parameter selection process required for the system matrix. For the other approach the temporal and spatial homogeneity of the magnetic field gradient over the entire FOV has to be high to perform an accurate reconstruction, which results in smaller FOVs. In this paper a novel reconstruction method is presented, which combines the advantages of both reconstruction methods to be more flexible during the entire reconstruction process. Furthermore, it enables the possibility of performing a dynamic patch reconstruction, which allows to select arbitrary areas of the FOV for higher resolution reducing reconstruction time significantly. In addition, this new reconstruction improved the image quality of a Traveling Wave MPI scanner substantially.
• First in vivo traveling wave magnetic particle imaging of a beating mouse heart Vogel, Patrick; Rückert, Martin Andreas; Klauer, Peter; Kullmann, Walter Heinrich; Jakob, Peter Michael; Behr, Volker Christian in Phys. Med. Biol. (2016). 61(18) 6620–6634.
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  Magnetic particle imaging (MPI) is a non-invasive imaging modality for direct detection of superparamagnetic iron-oxide nanoparticles based on the nonlinear magnetization response of magnetic materials to alternating magnetic fields. This highly sensitive and rapid method allows both a quantitative and a qualitative analysis of the measured signal. Since the first publication of MPI in 2005 several different scanner concepts have been presented and in 2009 the first in vivo imaging results of a beating mouse heart were shown. However, since the field of view (FOV) of the first MPI-scanner only covers a small region several approaches and hardware enhancements were presented to overcome this issue and could increase the FOV on cost of acquisition speed. In 2014 an alternative scanner concept, the traveling wave MPI (TWMPI), was presented, which allows scanning an entire mouse-sized volume at once. In this paper the first in vivo imaging results using the TWMPI system are presented. By optimizing the trajectory the temporal resolution is sufficiently high to resolve the dynamic of a beating mouse heart.

  @article{vogel2016first, abstract = {Magnetic particle imaging (MPI) is a non-invasive imaging modality for direct detection of superparamagnetic iron-oxide nanoparticles based on the nonlinear magnetization response of magnetic materials to alternating magnetic fields. This highly sensitive and rapid method allows both a quantitative and a qualitative analysis of the measured signal. Since the first publication of MPI in 2005 several different scanner concepts have been presented and in 2009 the first in vivo imaging results of a beating mouse heart were shown. However, since the field of view (FOV) of the first MPI-scanner only covers a small region several approaches and hardware enhancements were presented to overcome this issue and could increase the FOV on cost of acquisition speed. In 2014 an alternative scanner concept, the traveling wave MPI (TWMPI), was presented, which allows scanning an entire mouse-sized volume at once. In this paper the first in vivo imaging results using the TWMPI system are presented. By optimizing the trajectory the temporal resolution is sufficiently high to resolve the dynamic of a beating mouse heart.}, author = {Vogel, Patrick and Rückert, Martin Andreas and Klauer, Peter and Kullmann, Walter Heinrich and Jakob, Peter Michael and Behr, Volker Christian}, journal = {Phys. Med. Biol.}, keywords = {peer}, month = 9, number = 18, pages = {6620-6634}, title = {First in vivo traveling wave magnetic particle imaging of a beating mouse heart}, volume = 61, year = 2016 }

  %0 Journal Article %1 vogel2016first %A Vogel, Patrick %A Rückert, Martin Andreas %A Klauer, Peter %A Kullmann, Walter Heinrich %A Jakob, Peter Michael %A Behr, Volker Christian %D 2016 %J Phys. Med. Biol. %N 18 %P 6620-6634 %R 10.1088/0031-9155/61/18/6620 %T First in vivo traveling wave magnetic particle imaging of a beating mouse heart %V 61 %X Magnetic particle imaging (MPI) is a non-invasive imaging modality for direct detection of superparamagnetic iron-oxide nanoparticles based on the nonlinear magnetization response of magnetic materials to alternating magnetic fields. This highly sensitive and rapid method allows both a quantitative and a qualitative analysis of the measured signal. Since the first publication of MPI in 2005 several different scanner concepts have been presented and in 2009 the first in vivo imaging results of a beating mouse heart were shown. However, since the field of view (FOV) of the first MPI-scanner only covers a small region several approaches and hardware enhancements were presented to overcome this issue and could increase the FOV on cost of acquisition speed. In 2014 an alternative scanner concept, the traveling wave MPI (TWMPI), was presented, which allows scanning an entire mouse-sized volume at once. In this paper the first in vivo imaging results using the TWMPI system are presented. By optimizing the trajectory the temporal resolution is sufficiently high to resolve the dynamic of a beating mouse heart.
• Numerical Simulations of 3D Rotational Drift Vilter, Anna; Rückert, Martin Andreas; Kampf, Thomas; Sturm, Volker Jörg Friedrich; Behr, Volker Christian in Int. J. Magn. Part. Imag. (2016). 2(1) 1607001.
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  Due to its broad range of applications in biology and medicine, detection of magnetic particles gains increasing importance. The established method of magnetic particle imaging (MPI) bases on the non-linear magnetization behavior of superparamagnetic nanoparticles [1]. As an alternative approach, rotational drift spectroscopy (RDS) [2,3] aims at detecting the properties of magnetic particles in liquid suspensions based on their motional behavior inside an external rotating magnetic field. Serving as basis for the physical understanding and further development of RDS, the rotational behavior of particles with and without motional restriction is studied by numerical simulation. For this purpose, two different approaches were implemented: one using an explicit Euler algorithm and an improved version using a semi-analytical two-step procedure in order to overcome numerical instabilities of the original code. The results show independently of motional restriction two characteristic types of rotational behavior. The particles either follow the external field with a locked phase lag or exhibit a rotational drift.

  @article{vilter2016numerical, abstract = {Due to its broad range of applications in biology and medicine, detection of magnetic particles gains increasing importance. The established method of magnetic particle imaging (MPI) bases on the non-linear magnetization behavior of superparamagnetic nanoparticles [1]. As an alternative approach, rotational drift spectroscopy (RDS) [2,3] aims at detecting the properties of magnetic particles in liquid suspensions based on their motional behavior inside an external rotating magnetic field. Serving as basis for the physical understanding and further development of RDS, the rotational behavior of particles with and without motional restriction is studied by numerical simulation. For this purpose, two different approaches were implemented: one using an explicit Euler algorithm and an improved version using a semi-analytical two-step procedure in order to overcome numerical instabilities of the original code. The results show independently of motional restriction two characteristic types of rotational behavior. The particles either follow the external field with a locked phase lag or exhibit a rotational drift.}, author = {Vilter, Anna and Rückert, Martin Andreas and Kampf, Thomas and Sturm, Volker Jörg Friedrich and Behr, Volker Christian}, journal = {Int. J. Magn. Part. Imag.}, keywords = {rds}, month = 7, number = 1, pages = 1607001, title = {Numerical Simulations of 3D Rotational Drift}, volume = 2, year = 2016 }

  %0 Journal Article %1 vilter2016numerical %A Vilter, Anna %A Rückert, Martin Andreas %A Kampf, Thomas %A Sturm, Volker Jörg Friedrich %A Behr, Volker Christian %D 2016 %J Int. J. Magn. Part. Imag. %N 1 %P 1607001 %R 10.18416/ijmpi.2016.1607001 %T Numerical Simulations of 3D Rotational Drift %V 2 %X Due to its broad range of applications in biology and medicine, detection of magnetic particles gains increasing importance. The established method of magnetic particle imaging (MPI) bases on the non-linear magnetization behavior of superparamagnetic nanoparticles [1]. As an alternative approach, rotational drift spectroscopy (RDS) [2,3] aims at detecting the properties of magnetic particles in liquid suspensions based on their motional behavior inside an external rotating magnetic field. Serving as basis for the physical understanding and further development of RDS, the rotational behavior of particles with and without motional restriction is studied by numerical simulation. For this purpose, two different approaches were implemented: one using an explicit Euler algorithm and an improved version using a semi-analytical two-step procedure in order to overcome numerical instabilities of the original code. The results show independently of motional restriction two characteristic types of rotational behavior. The particles either follow the external field with a locked phase lag or exhibit a rotational drift.
• Proton magnetic resonance imaging used to investigate dewatering of green sapwood by cycling carbon dioxide between supercritical fluid and gas phase Newman, Roger H.; Franich, Robert A.; Meder, Roger; Hill, Stefan J.; Kroese, Hank; Sandquist, David; Hindmarsh, Jason P.; Schmid, Martin W.; Fuchs, Johannes; Behr, Volker C. in J. Supercrit. Fluids (2016). 111 36–42.
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  Proton magnetic resonance (MR) imaging at 300 MHz was used to characterise the dewatering of Pinus radiata sapwood. The sapwood was immersed in CO2 that was cycled at temperatures greater than 31 °C between gas (0.1–6 MPa) and supercritical fluid (15–20 MPa) phase. A combination of FLASH and RARE pulse sequences were used to highlight differences in T2*(H) and T2(H) relaxation. It was observed that CO2 entered into the green sapwood via air or water vapour-filled cells in the latewood and then diffused into earlywood cells adjacent to the pith side of the latewood bands. The dissolved CO2 reduced the surface tension of water which facilitated the expulsion of sap. As the pressure was released, and CO2 bubbles formed and expanded, the sap flowed tangentially towards the surfaces. This accounted, in part, for the observed independence of sample size on the supercritical CO2 dewatering process.

  @article{newman2016proton, abstract = {Proton magnetic resonance (MR) imaging at 300 MHz was used to characterise the dewatering of Pinus radiata sapwood. The sapwood was immersed in CO2 that was cycled at temperatures greater than 31 °C between gas (0.1–6 MPa) and supercritical fluid (15–20 MPa) phase. A combination of FLASH and RARE pulse sequences were used to highlight differences in T2*(H) and T2(H) relaxation. It was observed that CO2 entered into the green sapwood via air or water vapour-filled cells in the latewood and then diffused into earlywood cells adjacent to the pith side of the latewood bands. The dissolved CO2 reduced the surface tension of water which facilitated the expulsion of sap. As the pressure was released, and CO2 bubbles formed and expanded, the sap flowed tangentially towards the surfaces. This accounted, in part, for the observed independence of sample size on the supercritical CO2 dewatering process.}, author = {Newman, Roger H. and Franich, Robert A. and Meder, Roger and Hill, Stefan J. and Kroese, Hank and Sandquist, David and Hindmarsh, Jason P. and Schmid, Martin W. and Fuchs, Johannes and Behr, Volker C.}, journal = {J. Supercrit. Fluids}, keywords = {peer}, month = 5, pages = {36-42}, title = {Proton magnetic resonance imaging used to investigate dewatering of green sapwood by cycling carbon dioxide between supercritical fluid and gas phase}, volume = 111, year = 2016 }

  %0 Journal Article %1 newman2016proton %A Newman, Roger H. %A Franich, Robert A. %A Meder, Roger %A Hill, Stefan J. %A Kroese, Hank %A Sandquist, David %A Hindmarsh, Jason P. %A Schmid, Martin W. %A Fuchs, Johannes %A Behr, Volker C. %D 2016 %J J. Supercrit. Fluids %P 36-42 %R 10.1016/j.supflu.2016.01.007 %T Proton magnetic resonance imaging used to investigate dewatering of green sapwood by cycling carbon dioxide between supercritical fluid and gas phase %V 111 %X Proton magnetic resonance (MR) imaging at 300 MHz was used to characterise the dewatering of Pinus radiata sapwood. The sapwood was immersed in CO2 that was cycled at temperatures greater than 31 °C between gas (0.1–6 MPa) and supercritical fluid (15–20 MPa) phase. A combination of FLASH and RARE pulse sequences were used to highlight differences in T2*(H) and T2(H) relaxation. It was observed that CO2 entered into the green sapwood via air or water vapour-filled cells in the latewood and then diffused into earlywood cells adjacent to the pith side of the latewood bands. The dissolved CO2 reduced the surface tension of water which facilitated the expulsion of sap. As the pressure was released, and CO2 bubbles formed and expanded, the sap flowed tangentially towards the surfaces. This accounted, in part, for the observed independence of sample size on the supercritical CO2 dewatering process.

• Self diffusion coefficients of organic solvents and their binary mixtures with CO2 in silica alcogels at pressures up to 6 MPa derived by NMR pulsed gradient spin echo Behr, Wolfgang; Behr, Volker C.; Reichenauer, Gudrun in J. Supercrit. Fluids (2015). 106 50–56.
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  Self diffusion coefficients were determined using NMR (nuclear magnetic resonance) pulsed gradient spin echo (PGSE) in combination with a special high pressure autoclave. The goal was to determine the self diffusion coefficients for different CO2/methanol and CO2/ethanol mixtures within the pore phase of silica alcogels at pressures up to 6 MPa. These values are required as input data for the modeling of process steps preceding the supercritical drying of these gels. The self diffusion coefficients derived with the set-up at 15 °C for unconfined CO2/methanol and CO2/ethanol mixtures as a function of concentration of the organic solvent as well as of fluid pressure are in line with results from previous publications thus proofing the approach to provide reliable data. Measurements of self diffusion coefficients of methanol at different pressures and methanol/CO2 ratios were performed in tetramethoxysilane based silica alcogels with target densities ranging from 80 to 200 kg/m3; the results reveal tortuosities of up to 2.5 depending on the silica fraction in the gel as well as its structure. The experimental self diffusion coefficients are in good agreement with the transport diffusion coefficient determined from time resolved NMR imaging of a fluid exchange within a alcogel of methanol for CO2 at 5.8 MPa.

  @article{behr2015diffusion, abstract = {Self diffusion coefficients were determined using NMR (nuclear magnetic resonance) pulsed gradient spin echo (PGSE) in combination with a special high pressure autoclave. The goal was to determine the self diffusion coefficients for different CO2/methanol and CO2/ethanol mixtures within the pore phase of silica alcogels at pressures up to 6 MPa. These values are required as input data for the modeling of process steps preceding the supercritical drying of these gels. The self diffusion coefficients derived with the set-up at 15 °C for unconfined CO2/methanol and CO2/ethanol mixtures as a function of concentration of the organic solvent as well as of fluid pressure are in line with results from previous publications thus proofing the approach to provide reliable data. Measurements of self diffusion coefficients of methanol at different pressures and methanol/CO2 ratios were performed in tetramethoxysilane based silica alcogels with target densities ranging from 80 to 200 kg/m3; the results reveal tortuosities of up to 2.5 depending on the silica fraction in the gel as well as its structure. The experimental self diffusion coefficients are in good agreement with the transport diffusion coefficient determined from time resolved NMR imaging of a fluid exchange within a alcogel of methanol for CO2 at 5.8 MPa.}, author = {Behr, Wolfgang and Behr, Volker C. and Reichenauer, Gudrun}, journal = {J. Supercrit. Fluids}, keywords = {peer}, month = 11, pages = {50-56}, title = {Self diffusion coefficients of organic solvents and their binary mixtures with CO2 in silica alcogels at pressures up to 6 MPa derived by NMR pulsed gradient spin echo}, volume = 106, year = 2015 }

  %0 Journal Article %1 behr2015diffusion %A Behr, Wolfgang %A Behr, Volker C. %A Reichenauer, Gudrun %D 2015 %J J. Supercrit. Fluids %P 50-56 %R 10.1016/j.supflu.2015.05.024 %T Self diffusion coefficients of organic solvents and their binary mixtures with CO2 in silica alcogels at pressures up to 6 MPa derived by NMR pulsed gradient spin echo %V 106 %X Self diffusion coefficients were determined using NMR (nuclear magnetic resonance) pulsed gradient spin echo (PGSE) in combination with a special high pressure autoclave. The goal was to determine the self diffusion coefficients for different CO2/methanol and CO2/ethanol mixtures within the pore phase of silica alcogels at pressures up to 6 MPa. These values are required as input data for the modeling of process steps preceding the supercritical drying of these gels. The self diffusion coefficients derived with the set-up at 15 °C for unconfined CO2/methanol and CO2/ethanol mixtures as a function of concentration of the organic solvent as well as of fluid pressure are in line with results from previous publications thus proofing the approach to provide reliable data. Measurements of self diffusion coefficients of methanol at different pressures and methanol/CO2 ratios were performed in tetramethoxysilane based silica alcogels with target densities ranging from 80 to 200 kg/m3; the results reveal tortuosities of up to 2.5 depending on the silica fraction in the gel as well as its structure. The experimental self diffusion coefficients are in good agreement with the transport diffusion coefficient determined from time resolved NMR imaging of a fluid exchange within a alcogel of methanol for CO2 at 5.8 MPa.
• A comparative study of dewatering of Pinus radiata sapwood using supercritical CO2 and conventional forced air-drying via in situ magnetic resonance microimaging (MRI) Meder, Roger; Franich, Robert A.; Callaghan, Paul T.; Behr, Volker C. in Holzforschung (2015). 69(9) 1137–1142.
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  A comparison of moisture loss from Pinus radiata sapwood by conventional forced air-drying and a novel supercritical carbon dioxide (scCO2) dewatering process has been examined in situ using magnetic resonance microimaging. Air-drying results in the nonuniform removal of moisture within the wood volume, leading to a dry core and wet perimeter where water evaporated, whereas the scCO2 dewatering process resulted in moisture expulsion more uniformly throughout the volume of the specimen, especially so within the earlywood.

  @article{meder2015comparative, abstract = {A comparison of moisture loss from Pinus radiata sapwood by conventional forced air-drying and a novel supercritical carbon dioxide (scCO2) dewatering process has been examined in situ using magnetic resonance microimaging. Air-drying results in the nonuniform removal of moisture within the wood volume, leading to a dry core and wet perimeter where water evaporated, whereas the scCO2 dewatering process resulted in moisture expulsion more uniformly throughout the volume of the specimen, especially so within the earlywood.}, author = {Meder, Roger and Franich, Robert A. and Callaghan, Paul T. and Behr, Volker C.}, journal = {Holzforschung}, keywords = {peer}, month = 11, number = 9, pages = {1137-1142}, title = {A comparative study of dewatering of Pinus radiata sapwood using supercritical CO2 and conventional forced air-drying via in situ magnetic resonance microimaging (MRI)}, volume = 69, year = 2015 }

  %0 Journal Article %1 meder2015comparative %A Meder, Roger %A Franich, Robert A. %A Callaghan, Paul T. %A Behr, Volker C. %D 2015 %J Holzforschung %N 9 %P 1137-1142 %R 10.1515/hf-2014-0134 %T A comparative study of dewatering of Pinus radiata sapwood using supercritical CO2 and conventional forced air-drying via in situ magnetic resonance microimaging (MRI) %V 69 %X A comparison of moisture loss from Pinus radiata sapwood by conventional forced air-drying and a novel supercritical carbon dioxide (scCO2) dewatering process has been examined in situ using magnetic resonance microimaging. Air-drying results in the nonuniform removal of moisture within the wood volume, leading to a dry core and wet perimeter where water evaporated, whereas the scCO2 dewatering process resulted in moisture expulsion more uniformly throughout the volume of the specimen, especially so within the earlywood.
• Analysis of the Noise Correlation in MRI Coil Arrays Loaded With Metamaterial Magnetoinductive Lenses Algarin, Jose M.; Breuer, Felix; Behr, Volker C.; Freire, Manuel J. in IEEE Trans. Med. Imaging (2015). 34(5) 1148–1154.
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  A numerical method is shown for calculating the noise correlation coefficient in arrays of magnetic resonance imaging (MRI) coils loaded with capacitively-loaded ring metamaterial lenses, and in the presence of a conducting half-space resembling a sample. This numerical method is validated by comparison with experimental results obtained in two different experimental procedures for double check: noise resistance measurements with a network analyzer and noise correlation measurements in an MRI system. It is found that, for practical array configurations such as overlapping coils or capacitively-decoupled coils, the noise correlation coefficient turns negative for coils loaded with metamaterial lenses. In particular, the analysis is carried out with metamaterial structures known as magnetoinductive lenses, which have been demonstrated in previous works to improve the signal-to-noise ratio of MRI coils. Results are also shown to demonstrate that negative noise correlations have as an effect the improvement of the g-factor in coil arrays for parallel MRI.

  @article{algarin2015analysis, abstract = {A numerical method is shown for calculating the noise correlation coefficient in arrays of magnetic resonance imaging (MRI) coils loaded with capacitively-loaded ring metamaterial lenses, and in the presence of a conducting half-space resembling a sample. This numerical method is validated by comparison with experimental results obtained in two different experimental procedures for double check: noise resistance measurements with a network analyzer and noise correlation measurements in an MRI system. It is found that, for practical array configurations such as overlapping coils or capacitively-decoupled coils, the noise correlation coefficient turns negative for coils loaded with metamaterial lenses. In particular, the analysis is carried out with metamaterial structures known as magnetoinductive lenses, which have been demonstrated in previous works to improve the signal-to-noise ratio of MRI coils. Results are also shown to demonstrate that negative noise correlations have as an effect the improvement of the g-factor in coil arrays for parallel MRI.}, author = {Algarin, Jose M. and Breuer, Felix and Behr, Volker C. and Freire, Manuel J.}, journal = {IEEE Trans. Med. Imaging}, keywords = {peer}, month = 5, number = 5, pages = {1148-1154}, title = {Analysis of the Noise Correlation in MRI Coil Arrays Loaded With Metamaterial Magnetoinductive Lenses}, volume = 34, year = 2015 }

  %0 Journal Article %1 algarin2015analysis %A Algarin, Jose M. %A Breuer, Felix %A Behr, Volker C. %A Freire, Manuel J. %D 2015 %J IEEE Trans. Med. Imaging %N 5 %P 1148-1154 %R 10.1109/TMI.2014.2377792 %T Analysis of the Noise Correlation in MRI Coil Arrays Loaded With Metamaterial Magnetoinductive Lenses %V 34 %X A numerical method is shown for calculating the noise correlation coefficient in arrays of magnetic resonance imaging (MRI) coils loaded with capacitively-loaded ring metamaterial lenses, and in the presence of a conducting half-space resembling a sample. This numerical method is validated by comparison with experimental results obtained in two different experimental procedures for double check: noise resistance measurements with a network analyzer and noise correlation measurements in an MRI system. It is found that, for practical array configurations such as overlapping coils or capacitively-decoupled coils, the noise correlation coefficient turns negative for coils loaded with metamaterial lenses. In particular, the analysis is carried out with metamaterial structures known as magnetoinductive lenses, which have been demonstrated in previous works to improve the signal-to-noise ratio of MRI coils. Results are also shown to demonstrate that negative noise correlations have as an effect the improvement of the g-factor in coil arrays for parallel MRI.
• Simulating the Signal Generation of Rotational Drift Spectroscopy Rückert, Martin Andreas; Vogel, Patrick; Kampf, Thomas; Kullmann, Walter H; Jakob, Peter Michael; Behr, Volker Christian in IEEE Trans. Magn. (2015). 51(2) 6500704.
  • [ Abstract ]
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  Magnetic particles have become a core ingredient for many applications in chemistry, biology, and medical diagnostics, e.g., as basis for bioanalytical methods or tracer material for medical imaging. This paper discusses the theory and presents numerical simulations of a new method called rotational drift spectroscopy (RDS), which uses rotating magnetic fields for measuring the properties of magnetic nanoparticles (MNPs) in liquid suspensions. The RDS signal is based on the nonlinear rotational drift behavior of MNPs in rotating magnetic fields, which is highly dependent on the properties of the MNPs as well as their interaction with the environment. This dependence makes it a highly promising tool for detecting the binding of functionalized MNPs with, e.g., proteins, viruses, or cells. This paper presents the theory and numerical simulations of this method.

  @article{rckert2015simulating, abstract = {Magnetic particles have become a core ingredient for many applications in chemistry, biology, and medical diagnostics, e.g., as basis for bioanalytical methods or tracer material for medical imaging. This paper discusses the theory and presents numerical simulations of a new method called rotational drift spectroscopy (RDS), which uses rotating magnetic fields for measuring the properties of magnetic nanoparticles (MNPs) in liquid suspensions. The RDS signal is based on the nonlinear rotational drift behavior of MNPs in rotating magnetic fields, which is highly dependent on the properties of the MNPs as well as their interaction with the environment. This dependence makes it a highly promising tool for detecting the binding of functionalized MNPs with, e.g., proteins, viruses, or cells. This paper presents the theory and numerical simulations of this method.}, author = {Rückert, Martin Andreas and Vogel, Patrick and Kampf, Thomas and Kullmann, Walter H and Jakob, Peter Michael and Behr, Volker Christian}, journal = {IEEE Trans. Magn.}, keywords = {rds}, month = 2, number = 2, pages = 6500704, title = {Simulating the Signal Generation of Rotational Drift Spectroscopy}, volume = 51, year = 2015 }

  %0 Journal Article %1 rckert2015simulating %A Rückert, Martin Andreas %A Vogel, Patrick %A Kampf, Thomas %A Kullmann, Walter H %A Jakob, Peter Michael %A Behr, Volker Christian %D 2015 %J IEEE Trans. Magn. %N 2 %P 6500704 %R 10.1109/TMAG.2014.2335536 %T Simulating the Signal Generation of Rotational Drift Spectroscopy %V 51 %X Magnetic particles have become a core ingredient for many applications in chemistry, biology, and medical diagnostics, e.g., as basis for bioanalytical methods or tracer material for medical imaging. This paper discusses the theory and presents numerical simulations of a new method called rotational drift spectroscopy (RDS), which uses rotating magnetic fields for measuring the properties of magnetic nanoparticles (MNPs) in liquid suspensions. The RDS signal is based on the nonlinear rotational drift behavior of MNPs in rotating magnetic fields, which is highly dependent on the properties of the MNPs as well as their interaction with the environment. This dependence makes it a highly promising tool for detecting the binding of functionalized MNPs with, e.g., proteins, viruses, or cells. This paper presents the theory and numerical simulations of this method.
• Rotating Slice Scanning Mode for Traveling Wave MPI Vogel, Patrick; Rückert, Martin Andreas; Klauer, Peter; Kullmann, Walter H; Jakob, Peter Michael; Behr, Volker Christian in IEEE Trans. Magn. (2015). 51(2) 6501503.
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  Since the introduction of magnetic particle imaging in 2005, several different types of scanner were presented. One of them is the traveling wave magnetic particle imaging (TWMPI) scanner. It uses for imaging a dynamic linear gradient array for a dynamic generation of a strong gradient and field free point. An unresolved issue of the TWMPI approach so far is the non-isotropic spatial resolution. As an alternative in this paper, a rotating slice scanning mode for TWMPI is presented to overcome this issue. This approach rotates the scanning-slices around the scanner axis and uses a projection reconstruction method to get a 3-D volume with a high isotropic resolution.

  @article{vogel2015rotating, abstract = {Since the introduction of magnetic particle imaging in 2005, several different types of scanner were presented. One of them is the traveling wave magnetic particle imaging (TWMPI) scanner. It uses for imaging a dynamic linear gradient array for a dynamic generation of a strong gradient and field free point. An unresolved issue of the TWMPI approach so far is the non-isotropic spatial resolution. As an alternative in this paper, a rotating slice scanning mode for TWMPI is presented to overcome this issue. This approach rotates the scanning-slices around the scanner axis and uses a projection reconstruction method to get a 3-D volume with a high isotropic resolution.}, author = {Vogel, Patrick and Rückert, Martin Andreas and Klauer, Peter and Kullmann, Walter H and Jakob, Peter Michael and Behr, Volker Christian}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 2, number = 2, pages = 6501503, title = {Rotating Slice Scanning Mode for Traveling Wave MPI}, volume = 51, year = 2015 }

  %0 Journal Article %1 vogel2015rotating %A Vogel, Patrick %A Rückert, Martin Andreas %A Klauer, Peter %A Kullmann, Walter H %A Jakob, Peter Michael %A Behr, Volker Christian %D 2015 %J IEEE Trans. Magn. %N 2 %P 6501503 %R 10.1109/TMAG.2014.2335255 %T Rotating Slice Scanning Mode for Traveling Wave MPI %V 51 %X Since the introduction of magnetic particle imaging in 2005, several different types of scanner were presented. One of them is the traveling wave magnetic particle imaging (TWMPI) scanner. It uses for imaging a dynamic linear gradient array for a dynamic generation of a strong gradient and field free point. An unresolved issue of the TWMPI approach so far is the non-isotropic spatial resolution. As an alternative in this paper, a rotating slice scanning mode for TWMPI is presented to overcome this issue. This approach rotates the scanning-slices around the scanner axis and uses a projection reconstruction method to get a 3-D volume with a high isotropic resolution.
• Bimodal TWMPI-MRI Hybrid Scanner - Coil Setup and Electronics Klauer, Peter; Vogel, Patrick; Rückert, Martin Andreas; Kullmann, Walter H; Jakob, Peter Michael; Behr, Volker Christian in IEEE Trans. Magn. (2015). 51(2) 5300504.
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  Magnetic particle imaging (MPI) was first presented in 2005. It is based on the nonlinear response of ferromagnetic material and the fact that the magnetization saturates at sufficiently high magnetic fields. In contrast to magnetic resonance imaging (MRI), MPI directly detects the concentration and distribution of superparamagnetic iron-oxide nanoparticles without any background of any tissue. To overcome this issue, a traveling wave MPI (TWMPI) device was combined with a low field MRI scanner to demonstrate the feasibility of a hybrid scanner, which contains both imaging modalities in a single device. The hardware of both separate approaches should be improved and optimized to reach higher fields and a higher resolution, especially for the MRI measurement. Therefore, the dynamic linear gradient array from the TWMPI scanner was modified in a way to produce also a homogenous magnetic field, which can be used for MRI.

  @article{klauer2015bimodal, abstract = {Magnetic particle imaging (MPI) was first presented in 2005. It is based on the nonlinear response of ferromagnetic material and the fact that the magnetization saturates at sufficiently high magnetic fields. In contrast to magnetic resonance imaging (MRI), MPI directly detects the concentration and distribution of superparamagnetic iron-oxide nanoparticles without any background of any tissue. To overcome this issue, a traveling wave MPI (TWMPI) device was combined with a low field MRI scanner to demonstrate the feasibility of a hybrid scanner, which contains both imaging modalities in a single device. The hardware of both separate approaches should be improved and optimized to reach higher fields and a higher resolution, especially for the MRI measurement. Therefore, the dynamic linear gradient array from the TWMPI scanner was modified in a way to produce also a homogenous magnetic field, which can be used for MRI.}, author = {Klauer, Peter and Vogel, Patrick and Rückert, Martin Andreas and Kullmann, Walter H and Jakob, Peter Michael and Behr, Volker Christian}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 2, number = 2, pages = 5300504, title = {Bimodal TWMPI-MRI Hybrid Scanner - Coil Setup and Electronics}, volume = 51, year = 2015 }

  %0 Journal Article %1 klauer2015bimodal %A Klauer, Peter %A Vogel, Patrick %A Rückert, Martin Andreas %A Kullmann, Walter H %A Jakob, Peter Michael %A Behr, Volker Christian %D 2015 %J IEEE Trans. Magn. %N 2 %P 5300504 %R 10.1109/TMAG.2014.2324180 %T Bimodal TWMPI-MRI Hybrid Scanner - Coil Setup and Electronics %V 51 %X Magnetic particle imaging (MPI) was first presented in 2005. It is based on the nonlinear response of ferromagnetic material and the fact that the magnetization saturates at sufficiently high magnetic fields. In contrast to magnetic resonance imaging (MRI), MPI directly detects the concentration and distribution of superparamagnetic iron-oxide nanoparticles without any background of any tissue. To overcome this issue, a traveling wave MPI (TWMPI) device was combined with a low field MRI scanner to demonstrate the feasibility of a hybrid scanner, which contains both imaging modalities in a single device. The hardware of both separate approaches should be improved and optimized to reach higher fields and a higher resolution, especially for the MRI measurement. Therefore, the dynamic linear gradient array from the TWMPI scanner was modified in a way to produce also a homogenous magnetic field, which can be used for MRI.
• μMPI - Initial Experiments With an Ultrahigh Resolution MPI Vogel, Patrick; Rückert, Martin Andreas; Jakob, Peter Michael; Behr, Volker Christian in IEEE Trans. Magn. (2015). 51(2) 6502104.
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  Magnetic particle imaging (MPI) is a novel imaging method for the depiction of superparamagnetic materials. Since the first publication several MPI scanner were presented, which work at gradient strength of ~2-7 T/m. This is reasonable for in vivo imaging and provides a resolution of ~1 mm. In this paper, several approaches for a micro-MPI (μMPI) device for very small samples are presented, which works at a very high magnetic gradient strength of ~85 T/m. This results in a theoretical resolution <100 μm. This μMPI device can be operated at several modes, which have different advantages. In preliminary tests, the feasibility of the μMPI device has been proven.

  @article{vogel2015initial, abstract = {Magnetic particle imaging (MPI) is a novel imaging method for the depiction of superparamagnetic materials. Since the first publication several MPI scanner were presented, which work at gradient strength of  2-7 T/m. This is reasonable for in vivo imaging and provides a resolution of  1 mm. In this paper, several approaches for a micro-MPI (μMPI) device for very small samples are presented, which works at a very high magnetic gradient strength of  85 T/m. This results in a theoretical resolution <100 μm. This μMPI device can be operated at several modes, which have different advantages. In preliminary tests, the feasibility of the μMPI device has been proven.}, author = {Vogel, Patrick and Rückert, Martin Andreas and Jakob, Peter Michael and Behr, Volker Christian}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 2, number = 2, pages = 6502104, title = {μMPI - Initial Experiments With an Ultrahigh Resolution MPI}, volume = 51, year = 2015 }

  %0 Journal Article %1 vogel2015initial %A Vogel, Patrick %A Rückert, Martin Andreas %A Jakob, Peter Michael %A Behr, Volker Christian %D 2015 %J IEEE Trans. Magn. %N 2 %P 6502104 %R 10.1109/TMAG.2014.2329135 %T μMPI - Initial Experiments With an Ultrahigh Resolution MPI %V 51 %X Magnetic particle imaging (MPI) is a novel imaging method for the depiction of superparamagnetic materials. Since the first publication several MPI scanner were presented, which work at gradient strength of ~2-7 T/m. This is reasonable for in vivo imaging and provides a resolution of ~1 mm. In this paper, several approaches for a micro-MPI (μMPI) device for very small samples are presented, which works at a very high magnetic gradient strength of ~85 T/m. This results in a theoretical resolution <100 μm. This μMPI device can be operated at several modes, which have different advantages. In preliminary tests, the feasibility of the μMPI device has been proven.
• Superspeed Traveling Wave Magnetic Particle Imaging Vogel, Patrick; Rückert, Martin Andreas; Klauer, Peter; Kullmann, Walter H; Jakob, Peter Michael; Behr, Volker Christian in IEEE Trans. Magn. (2015). 51(2) 6501603.
  • [ Abstract ]
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  Since the first publication in 2005, several different scanner types for magnetic particle imaging (MPI) have been presented. One of these scanner concepts is traveling wave MPI (TWMPI). It uses a dynamic linear gradient array, which generates and moves a field free point with a strong gradient, which is necessary for scanning the sample in 3-D. Due to the linear properties of the TWMPI device, very fast 2-D imaging with frame rates higher than 1500 frames/s is possible (superspeed mode). Using the superspeed mode different high speed measurements are conceivable, e.g., fluid-dynamic investigations.

  @article{vogel2015superspeed, abstract = {Since the first publication in 2005, several different scanner types for magnetic particle imaging (MPI) have been presented. One of these scanner concepts is traveling wave MPI (TWMPI). It uses a dynamic linear gradient array, which generates and moves a field free point with a strong gradient, which is necessary for scanning the sample in 3-D. Due to the linear properties of the TWMPI device, very fast 2-D imaging with frame rates higher than 1500 frames/s is possible (superspeed mode). Using the superspeed mode different high speed measurements are conceivable, e.g., fluid-dynamic investigations.}, author = {Vogel, Patrick and Rückert, Martin Andreas and Klauer, Peter and Kullmann, Walter H and Jakob, Peter Michael and Behr, Volker Christian}, journal = {IEEE Trans. Magn.}, keywords = {peer}, month = 2, number = 2, pages = 6501603, title = {Superspeed Traveling Wave Magnetic Particle Imaging}, volume = 51, year = 2015 }

  %0 Journal Article %1 vogel2015superspeed %A Vogel, Patrick %A Rückert, Martin Andreas %A Klauer, Peter %A Kullmann, Walter H %A Jakob, Peter Michael %A Behr, Volker Christian %D 2015 %J IEEE Trans. Magn. %N 2 %P 6501603 %R 10.1109/TMAG.2014.2322897 %T Superspeed Traveling Wave Magnetic Particle Imaging %V 51 %X Since the first publication in 2005, several different scanner types for magnetic particle imaging (MPI) have been presented. One of these scanner concepts is traveling wave MPI (TWMPI). It uses a dynamic linear gradient array, which generates and moves a field free point with a strong gradient, which is necessary for scanning the sample in 3-D. Due to the linear properties of the TWMPI device, very fast 2-D imaging with frame rates higher than 1500 frames/s is possible (superspeed mode). Using the superspeed mode different high speed measurements are conceivable, e.g., fluid-dynamic investigations.
• Rotational Drift Spectroscopy for Magnetic Particle Ensembles Rückert, Martin Andreas; Vogel, Patrick; Vilter, Anna; Kullmann, Walter H; Jakob, Peter Michael; Behr, Volker Christian in IEEE Trans. Magn. (2015). 51(2) 6500604.
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  Magnetic particles have become a core ingredient for many applications in chemistry, biology, and medical diagnostics, e.g., as a basis for bioanalytical methods or as tracer material for medical imaging. This paper presents a new method called rotational drift spectroscopy (RDS) which uses rotating magnetic fields for measuring the properties of magnetic nanoparticles (MNPs) in liquid suspensions. The RDS signal is based on the nonlinear rotational drift behavior of MNPs in rotating magnetic fields, which is highly dependent on the properties of the MNPs as well as their interaction with the environment. This dependency allows detecting the binding of functionalized MNPs with, e.g., proteins, viruses, or cells with potentially very high sensitivity. This paper presents first experiments demonstrating rotational drift behavior on aggregated magnetic particle ensembles and the corresponding experimental setup.

  @article{rckert2015rotational, abstract = {Magnetic particles have become a core ingredient for many applications in chemistry, biology, and medical diagnostics, e.g., as a basis for bioanalytical methods or as tracer material for medical imaging. This paper presents a new method called rotational drift spectroscopy (RDS) which uses rotating magnetic fields for measuring the properties of magnetic nanoparticles (MNPs) in liquid suspensions. The RDS signal is based on the nonlinear rotational drift behavior of MNPs in rotating magnetic fields, which is highly dependent on the properties of the MNPs as well as their interaction with the environment. This dependency allows detecting the binding of functionalized MNPs with, e.g., proteins, viruses, or cells with potentially very high sensitivity. This paper presents first experiments demonstrating rotational drift behavior on aggregated magnetic particle ensembles and the corresponding experimental setup.}, author = {Rückert, Martin Andreas and Vogel, Patrick and Vilter, Anna and Kullmann, Walter H and Jakob, Peter Michael and Behr, Volker Christian}, journal = {IEEE Trans. Magn.}, keywords = {rds}, month = 2, number = 2, pages = 6500604, title = {Rotational Drift Spectroscopy for Magnetic Particle Ensembles}, volume = 51, year = 2015 }

  %0 Journal Article %1 rckert2015rotational %A Rückert, Martin Andreas %A Vogel, Patrick %A Vilter, Anna %A Kullmann, Walter H %A Jakob, Peter Michael %A Behr, Volker Christian %D 2015 %J IEEE Trans. Magn. %N 2 %P 6500604 %R 10.1109/TMAG.2014.2334138 %T Rotational Drift Spectroscopy for Magnetic Particle Ensembles %V 51 %X Magnetic particles have become a core ingredient for many applications in chemistry, biology, and medical diagnostics, e.g., as a basis for bioanalytical methods or as tracer material for medical imaging. This paper presents a new method called rotational drift spectroscopy (RDS) which uses rotating magnetic fields for measuring the properties of magnetic nanoparticles (MNPs) in liquid suspensions. The RDS signal is based on the nonlinear rotational drift behavior of MNPs in rotating magnetic fields, which is highly dependent on the properties of the MNPs as well as their interaction with the environment. This dependency allows detecting the binding of functionalized MNPs with, e.g., proteins, viruses, or cells with potentially very high sensitivity. This paper presents first experiments demonstrating rotational drift behavior on aggregated magnetic particle ensembles and the corresponding experimental setup.

• Carbon-13 {NMR} chemical-shift imaging study of dewatering of green sapwood by cycling carbon dioxide between the supercritical fluid and gas phases Behr, Volker C.; Hill, Stefan J.; Meder, Roger; Sandquist, David; Hindmarsh, Jason P.; Franich, Robert A.; Newman, Roger H. in J. Supercrit. Fluids (2014). 95 535–540.
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  Carbon-13 chemical-shift imaging (CSI) was used to study the distribution of CO2 in green pine sapwood that was partially dewatered by a process in which CO2 was cycled between the supercritical fluid and gas phases. Proton magnetic resonance imaging (MRI) was used to characterise the corresponding distribution of water. The CSI experiment showed strongest signals from cells with weakest proton MRI signals. This was consistent with a mechanism in which latewood bands provide pathways for supercritical CO2 to penetrate into the interior of a specimen. Supercritical CO2 also penetrated earlywood exposed on surfaces of the specimen.

  @article{behr2014carbon13, abstract = {Carbon-13 chemical-shift imaging (CSI) was used to study the distribution of CO2 in green pine sapwood that was partially dewatered by a process in which CO2 was cycled between the supercritical fluid and gas phases. Proton magnetic resonance imaging (MRI) was used to characterise the corresponding distribution of water. The CSI experiment showed strongest signals from cells with weakest proton MRI signals. This was consistent with a mechanism in which latewood bands provide pathways for supercritical CO2 to penetrate into the interior of a specimen. Supercritical CO2 also penetrated earlywood exposed on surfaces of the specimen.}, author = {Behr, Volker C. and Hill, Stefan J. and Meder, Roger and Sandquist, David and Hindmarsh, Jason P. and Franich, Robert A. and Newman, Roger H.}, journal = {J. Supercrit. Fluids}, keywords = {peer}, month = 11, pages = {535-540}, title = {Carbon-13 {NMR} chemical-shift imaging study of dewatering of green sapwood by cycling carbon dioxide between the supercritical fluid and gas phases}, volume = 95, year = 2014 }

  %0 Journal Article %1 behr2014carbon13 %A Behr, Volker C. %A Hill, Stefan J. %A Meder, Roger %A Sandquist, David %A Hindmarsh, Jason P. %A Franich, Robert A. %A Newman, Roger H. %D 2014 %J J. Supercrit. Fluids %P 535-540 %R 10.1016/j.supflu.2014.08.026 %T Carbon-13 {NMR} chemical-shift imaging study of dewatering of green sapwood by cycling carbon dioxide between the supercritical fluid and gas phases %V 95 %X Carbon-13 chemical-shift imaging (CSI) was used to study the distribution of CO2 in green pine sapwood that was partially dewatered by a process in which CO2 was cycled between the supercritical fluid and gas phases. Proton magnetic resonance imaging (MRI) was used to characterise the corresponding distribution of water. The CSI experiment showed strongest signals from cells with weakest proton MRI signals. This was consistent with a mechanism in which latewood bands provide pathways for supercritical CO2 to penetrate into the interior of a specimen. Supercritical CO2 also penetrated earlywood exposed on surfaces of the specimen.
• MRI Meets MPI: A Bimodal MPI-MRI Tomograph Vogel, Patrick; Lother, Steffen; Rückert, Martin Andreas; Kullmann, Walter H; Jakob, Peter Michael; Fidler, Florian; Behr, Volker Christian in IEEE Trans. Med. Imag. (2014). 33(10) 1954–1959.
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  While magnetic particle imaging (MPI) constitutes a novel biomedical imaging technique for tracking superpara magnetic nanoparticles in vivo, unlike magnetic resonance imaging (MRI), it cannot provide anatomical background information. Until now these two modalities have been performed in separate scanners and image co-registration has been hampered by the need to reposition the sample in both systems as similarly as possible. This paper presents a bimodal MPI-MRI-tomograph that combines both modalities in a single system. MPI and MRI images can thus be acquired without moving the sample or replacing any parts in the setup. The images acquired with the presented setup show excellent agreement between the localization of the nano particles in MPI and the MRI background data. A combination of two highly complementary imaging modalities has been achieved.

  @article{vogel2014meets, abstract = {While magnetic particle imaging (MPI) constitutes a novel biomedical imaging technique for tracking superpara magnetic nanoparticles in vivo, unlike magnetic resonance imaging (MRI), it cannot provide anatomical background information. Until now these two modalities have been performed in separate scanners and image co-registration has been hampered by the need to reposition the sample in both systems as similarly as possible. This paper presents a bimodal MPI-MRI-tomograph that combines both modalities in a single system. MPI and MRI images can thus be acquired without moving the sample or replacing any parts in the setup. The images acquired with the presented setup show excellent agreement between the localization of the nano particles in MPI and the MRI background data. A combination of two highly complementary imaging modalities has been achieved.}, author = {Vogel, Patrick and Lother, Steffen and Rückert, Martin Andreas and Kullmann, Walter H and Jakob, Peter Michael and Fidler, Florian and Behr, Volker Christian}, journal = {IEEE Trans. Med. Imag.}, keywords = {peer}, month = 10, number = 10, pages = {1954-1959}, title = {MRI Meets MPI: A Bimodal MPI-MRI Tomograph}, volume = 33, year = 2014 }

  %0 Journal Article %1 vogel2014meets %A Vogel, Patrick %A Lother, Steffen %A Rückert, Martin Andreas %A Kullmann, Walter H %A Jakob, Peter Michael %A Fidler, Florian %A Behr, Volker Christian %D 2014 %J IEEE Trans. Med. Imag. %N 10 %P 1954-1959 %R 10.1109/TMI.2014.2327515 %T MRI Meets MPI: A Bimodal MPI-MRI Tomograph %V 33 %X While magnetic particle imaging (MPI) constitutes a novel biomedical imaging technique for tracking superpara magnetic nanoparticles in vivo, unlike magnetic resonance imaging (MRI), it cannot provide anatomical background information. Until now these two modalities have been performed in separate scanners and image co-registration has been hampered by the need to reposition the sample in both systems as similarly as possible. This paper presents a bimodal MPI-MRI-tomograph that combines both modalities in a single system. MPI and MRI images can thus be acquired without moving the sample or replacing any parts in the setup. The images acquired with the presented setup show excellent agreement between the localization of the nano particles in MPI and the MRI background data. A combination of two highly complementary imaging modalities has been achieved.
• Metamaterial magnetoinductive lens performance as a function of field strength Algarín, José M.; Freire, Manuel J.; Breuer, Felix; Behr, Volker C. in J. Magn. Reson. (2014). 247 9–14.
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  Metamaterials are artificial composites that exhibit exotic electromagnetic properties, as the ability of metamaterial slabs to behave like lenses with sub-wavelength resolution for the electric or the magnetic field. In previous works, the authors investigated magnetic resonance imaging (MRI) applications of metamaterial slabs that behave like lenses for the radiofrequency magnetic field. In particular, the authors investigated the ability of MRI metamaterial lenses to increase the signal-to-noise ratio (SNR) of surface coils, and to localize the field of view (FOV) of the coils, which is of interest for parallel MRI (pMRI) applications. A metamaterial lens placed between a surface coil and the tissue enhances the sensitivity of the coil. Although the metamaterial lens introduces losses which add to the losses of the tissue, the enhancement of the sensitivity can compensate these additional losses and the SNR of the coil is increased. In a previous work, an optimization procedure was followed to find a metamaterial structure with minimum losses that will maximize the SNR. This structure was termed magnetoinductive (MI) lens by the authors. The properties of surface coils in the presence of MI lenses were investigated in previous works at the proton frequency of 1.5 T systems. The different frequency dependence of the losses in both the MI lenses and the tissue encouraged us to investigate the performance of MI lenses at different frequencies. Thus, in the present work, the SNR and the pMRI ability of MI lenses are investigated as a function of field strength. A numerical analysis is carried out with an algorithm developed by the authors to predict the SNR behavior of a surface coil loaded with a MI lens at the proton frequencies of 0.5 T, 1.5 T and 3 T systems. The results show that, at 0.5 T, there is a gain in the SNR for short distances, but the SNR is highly degraded at deeper distances. However, at 1.5 T and 3 T, the MI lenses provide a gain in the SNR up to a certain penetration depth, which is deeper at 3 T, and do not degrade the SNR at deeper distances. These numerical results are checked by means of an experiment. Moreover, a second experiment developed with two-channel arrays of surface coils loaded with MI lenses shows that the pMRI ability of the lenses also improves from 1.5 T to 3 T. This improvement was quantified by means of the calculation of the GRAPPA g-factor.

  @article{algarn2014metamaterial, abstract = {Metamaterials are artificial composites that exhibit exotic electromagnetic properties, as the ability of metamaterial slabs to behave like lenses with sub-wavelength resolution for the electric or the magnetic field. In previous works, the authors investigated magnetic resonance imaging (MRI) applications of metamaterial slabs that behave like lenses for the radiofrequency magnetic field. In particular, the authors investigated the ability of MRI metamaterial lenses to increase the signal-to-noise ratio (SNR) of surface coils, and to localize the field of view (FOV) of the coils, which is of interest for parallel MRI (pMRI) applications. A metamaterial lens placed between a surface coil and the tissue enhances the sensitivity of the coil. Although the metamaterial lens introduces losses which add to the losses of the tissue, the enhancement of the sensitivity can compensate these additional losses and the SNR of the coil is increased. In a previous work, an optimization procedure was followed to find a metamaterial structure with minimum losses that will maximize the SNR. This structure was termed magnetoinductive (MI) lens by the authors. The properties of surface coils in the presence of MI lenses were investigated in previous works at the proton frequency of 1.5 T systems. The different frequency dependence of the losses in both the MI lenses and the tissue encouraged us to investigate the performance of MI lenses at different frequencies. Thus, in the present work, the SNR and the pMRI ability of MI lenses are investigated as a function of field strength. A numerical analysis is carried out with an algorithm developed by the authors to predict the SNR behavior of a surface coil loaded with a MI lens at the proton frequencies of 0.5 T, 1.5 T and 3 T systems. The results show that, at 0.5 T, there is a gain in the SNR for short distances, but the SNR is highly degraded at deeper distances. However, at 1.5 T and 3 T, the MI lenses provide a gain in the SNR up to a certain penetration depth, which is deeper at 3 T, and do not degrade the SNR at deeper distances. These numerical results are checked by means of an experiment. Moreover, a second experiment developed with two-channel arrays of surface coils loaded with MI lenses shows that the pMRI ability of the lenses also improves from 1.5 T to 3 T. This improvement was quantified by means of the calculation of the GRAPPA g-factor.}, author = {Algarín, José M. and Freire, Manuel J. and Breuer, Felix and Behr, Volker C.}, journal = {J. Magn. Reson.}, keywords = {peer}, month = 10, pages = {9-14}, title = {Metamaterial magnetoinductive lens performance as a function of field strength}, volume = 247, year = 2014 }

  %0 Journal Article %1 algarn2014metamaterial %A Algarín, José M. %A Freire, Manuel J. %A Breuer, Felix %A Behr, Volker C. %D 2014 %J J. Magn. Reson. %P 9-14 %R doi.org/10.1016/j.jmr.2014.08.006 %T Metamaterial magnetoinductive lens performance as a function of field strength %V 247 %X Metamaterials are artificial composites that exhibit exotic electromagnetic properties, as the ability of metamaterial slabs to behave like lenses with sub-wavelength resolution for the electric or the magnetic field. In previous works, the authors investigated magnetic resonance imaging (MRI) applications of metamaterial slabs that behave like lenses for the radiofrequency magnetic field. In particular, the authors investigated the ability of MRI metamaterial lenses to increase the signal-to-noise ratio (SNR) of surface coils, and to localize the field of view (FOV) of the coils, which is of interest for parallel MRI (pMRI) applications. A metamaterial lens placed between a surface coil and the tissue enhances the sensitivity of the coil. Although the metamaterial lens introduces losses which add to the losses of the tissue, the enhancement of the sensitivity can compensate these additional losses and the SNR of the coil is increased. In a previous work, an optimization procedure was followed to find a metamaterial structure with minimum losses that will maximize the SNR. This structure was termed magnetoinductive (MI) lens by the authors. The properties of surface coils in the presence of MI lenses were investigated in previous works at the proton frequency of 1.5 T systems. The different frequency dependence of the losses in both the MI lenses and the tissue encouraged us to investigate the performance of MI lenses at different frequencies. Thus, in the present work, the SNR and the pMRI ability of MI lenses are investigated as a function of field strength. A numerical analysis is carried out with an algorithm developed by the authors to predict the SNR behavior of a surface coil loaded with a MI lens at the proton frequencies of 0.5 T, 1.5 T and 3 T systems. The results show that, at 0.5 T, there is a gain in the SNR for short distances, but the SNR is highly degraded at deeper distances. However, at 1.5 T and 3 T, the MI lenses provide a gain in the SNR up to a certain penetration depth, which is deeper at 3 T, and do not degrade the SNR at deeper distances. These numerical results are checked by means of an experiment. Moreover, a second experiment developed with two-channel arrays of surface coils loaded with MI lenses shows that the pMRI ability of the lenses also improves from 1.5 T to 3 T. This improvement was quantified by means of the calculation of the GRAPPA g-factor.
• Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock Vogel, Patrick; Rückert, Martin Andreas; Klauer, Peter; Kullmann, Walter H; Jakob, Peter Michael; Behr, Volker Christian in diffusion-fundamentals.org (2014). 22(12) 1–5.
  • [ Abstract ]
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  Determining the composition of solid materials is of high interest in areas such as material research or quality assurance. There are several modalities at disposal with which various parameters of the material can be observed, but of those only magnetic resonance imaging (MRI) or computer tomography (CT) offer a non-destructive determination of material distribution in 3D. A novel non-destructive imaging method is Magnetic Particle Imaging (MPI), which uses dynamic magnetic fields for a direct determination of the distribution of magnetic materials in 3D. With this approach, it is possible to determine and differentiate magnetic and nonmagnetic behaviour. In this paper, the first proof-of-principle measurements of magnetic properties in solid environments are presented using a home-built traveling wave magnetic particle imaging scanner.

  @article{vogel2014traveling, abstract = {Determining the composition of solid materials is of high interest in areas such as material research or quality assurance. There are several modalities at disposal with which various parameters of the material can be observed, but of those only magnetic resonance imaging (MRI) or computer tomography (CT) offer a non-destructive determination of material distribution in 3D. A novel non-destructive imaging method is Magnetic Particle Imaging (MPI), which uses dynamic magnetic fields for a direct determination of the distribution of magnetic materials in 3D. With this approach, it is possible to determine and differentiate magnetic and nonmagnetic behaviour. In this paper, the first proof-of-principle measurements of magnetic properties in solid environments are presented using a home-built traveling wave magnetic particle imaging scanner.}, author = {Vogel, Patrick and Rückert, Martin Andreas and Klauer, Peter and Kullmann, Walter H and Jakob, Peter Michael and Behr, Volker Christian}, journal = {diffusion-fundamentals.org}, keywords = {peer}, month = 3, number = 12, pages = {1-5}, title = {Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock}, volume = 22, year = 2014 }

  %0 Journal Article %1 vogel2014traveling %A Vogel, Patrick %A Rückert, Martin Andreas %A Klauer, Peter %A Kullmann, Walter H %A Jakob, Peter Michael %A Behr, Volker Christian %D 2014 %J diffusion-fundamentals.org %N 12 %P 1-5 %T Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock %U http://www.uni-leipzig.de/diffusion/pdf/volume22/diff_fund_22(2014)12.pdf %V 22 %X Determining the composition of solid materials is of high interest in areas such as material research or quality assurance. There are several modalities at disposal with which various parameters of the material can be observed, but of those only magnetic resonance imaging (MRI) or computer tomography (CT) offer a non-destructive determination of material distribution in 3D. A novel non-destructive imaging method is Magnetic Particle Imaging (MPI), which uses dynamic magnetic fields for a direct determination of the distribution of magnetic materials in 3D. With this approach, it is possible to determine and differentiate magnetic and nonmagnetic behaviour. In this paper, the first proof-of-principle measurements of magnetic properties in solid environments are presented using a home-built traveling wave magnetic particle imaging scanner.
• Traveling Wave Magnetic Particle Imaging Vogel, Patrick; Rückert, Martin Andreas; Klauer, Peter; Kullmann, Walter H; Jakob, Peter Michael; Behr, Volker Christian in IEEE Trans. Med. Imag. (2014). 33(2) 400–407.
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  Most 3-D magnetic particle imaging (MPI) scanners currently use permanent magnets to create the strong gradient field required for high resolution MPI. However, using permanent magnets limits the field of view (FOV) due to the large amount of energy required to move the field free point (FFP) from the center of the scanner. To address this issue, an alternative approach called “Traveling Wave MPI” is here presented. This approach employs a novel gradient system, the dynamic linear gradient array, to cover a large FOV while dynamically creating a strong magnetic gradient. The proposed design also enables the use of a so-called line-scanning mode, which simplifies the FFP trajectory to a linear path through the 3-D volume. This results in simplified mathematics, which facilitates the image reconstruction.

  @article{vogel2014traveling, abstract = {Most 3-D magnetic particle imaging (MPI) scanners currently use permanent magnets to create the strong gradient field required for high resolution MPI. However, using permanent magnets limits the field of view (FOV) due to the large amount of energy required to move the field free point (FFP) from the center of the scanner. To address this issue, an alternative approach called “Traveling Wave MPI” is here presented. This approach employs a novel gradient system, the dynamic linear gradient array, to cover a large FOV while dynamically creating a strong magnetic gradient. The proposed design also enables the use of a so-called line-scanning mode, which simplifies the FFP trajectory to a linear path through the 3-D volume. This results in simplified mathematics, which facilitates the image reconstruction.}, author = {Vogel, Patrick and Rückert, Martin Andreas and Klauer, Peter and Kullmann, Walter H and Jakob, Peter Michael and Behr, Volker Christian}, journal = {IEEE Trans. Med. Imag.}, keywords = {peer}, month = 2, number = 2, pages = {400-407}, title = {Traveling Wave Magnetic Particle Imaging}, volume = 33, year = 2014 }

  %0 Journal Article %1 vogel2014traveling %A Vogel, Patrick %A Rückert, Martin Andreas %A Klauer, Peter %A Kullmann, Walter H %A Jakob, Peter Michael %A Behr, Volker Christian %D 2014 %J IEEE Trans. Med. Imag. %N 2 %P 400-407 %R 10.1109/TMI.2013.2285472 %T Traveling Wave Magnetic Particle Imaging %V 33 %X Most 3-D magnetic particle imaging (MPI) scanners currently use permanent magnets to create the strong gradient field required for high resolution MPI. However, using permanent magnets limits the field of view (FOV) due to the large amount of energy required to move the field free point (FFP) from the center of the scanner. To address this issue, an alternative approach called “Traveling Wave MPI” is here presented. This approach employs a novel gradient system, the dynamic linear gradient array, to cover a large FOV while dynamically creating a strong magnetic gradient. The proposed design also enables the use of a so-called line-scanning mode, which simplifies the FFP trajectory to a linear path through the 3-D volume. This results in simplified mathematics, which facilitates the image reconstruction.

• Numerically Efficient Estimation of Relaxation Effects in Magnetic Particle Imaging Rückert, Martin Andreas; Vogel, Patrick; Jakob, Peter Michael; Behr, Volker Christian in Biomed. Tech. (2013). 58(6) 593–600.
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  Current simulations of the signal in magnetic particle imaging (MPI) are either based on the Langevin function or on directly measuring the system function. The former completely ignores the influence of finite relaxation times of magnetic particles, and the latter requires time-consuming reference scans with an existing MPI scanner. Therefore, the resulting system function only applies for a given tracer type and the properties of the applied scanning trajectory. It requires separate reference scans for different trajectories and does not allow simulating theoretical magnetic particle suspensions. The most accessible and accurate way for including relaxation effects in the signal simulation would be using the Langevin equation. However, this is a very time-consuming approach because it calculates the stochastic dynamics of the individual particles and averages over large particle ensembles. In the current article, a numerically efficient way for approximating the averaged Langevin equation is proposed, which is much faster than the approach based on the Langevin equation because it is directly calculating the averaged time evolution of the magnetization. The proposed simulation yields promising results. Except for the case of small orthogonal offset fields, a high agreement with the full but significantly slower simulation could be shown.

  @article{rckert2013numerically, abstract = {Current simulations of the signal in magnetic particle imaging (MPI) are either based on the Langevin function or on directly measuring the system function. The former completely ignores the influence of finite relaxation times of magnetic particles, and the latter requires time-consuming reference scans with an existing MPI scanner. Therefore, the resulting system function only applies for a given tracer type and the properties of the applied scanning trajectory. It requires separate reference scans for different trajectories and does not allow simulating theoretical magnetic particle suspensions. The most accessible and accurate way for including relaxation effects in the signal simulation would be using the Langevin equation. However, this is a very time-consuming approach because it calculates the stochastic dynamics of the individual particles and averages over large particle ensembles. In the current article, a numerically efficient way for approximating the averaged Langevin equation is proposed, which is much faster than the approach based on the Langevin equation because it is directly calculating the averaged time evolution of the magnetization. The proposed simulation yields promising results. Except for the case of small orthogonal offset fields, a high agreement with the full but significantly slower simulation could be shown.}, author = {Rückert, Martin Andreas and Vogel, Patrick and Jakob, Peter Michael and Behr, Volker Christian}, journal = {Biomed. Tech.}, keywords = {peer}, month = 12, number = 6, pages = {593-600}, title = {Numerically Efficient Estimation of Relaxation Effects in Magnetic Particle Imaging}, volume = 58, year = 2013 }

  %0 Journal Article %1 rckert2013numerically %A Rückert, Martin Andreas %A Vogel, Patrick %A Jakob, Peter Michael %A Behr, Volker Christian %D 2013 %J Biomed. Tech. %N 6 %P 593-600 %R 10.1515/bmt-2013-0015 %T Numerically Efficient Estimation of Relaxation Effects in Magnetic Particle Imaging %V 58 %X Current simulations of the signal in magnetic particle imaging (MPI) are either based on the Langevin function or on directly measuring the system function. The former completely ignores the influence of finite relaxation times of magnetic particles, and the latter requires time-consuming reference scans with an existing MPI scanner. Therefore, the resulting system function only applies for a given tracer type and the properties of the applied scanning trajectory. It requires separate reference scans for different trajectories and does not allow simulating theoretical magnetic particle suspensions. The most accessible and accurate way for including relaxation effects in the signal simulation would be using the Langevin equation. However, this is a very time-consuming approach because it calculates the stochastic dynamics of the individual particles and averages over large particle ensembles. In the current article, a numerically efficient way for approximating the averaged Langevin equation is proposed, which is much faster than the approach based on the Langevin equation because it is directly calculating the averaged time evolution of the magnetization. The proposed simulation yields promising results. Except for the case of small orthogonal offset fields, a high agreement with the full but significantly slower simulation could be shown.
• An advanced, integrated large-volume high-pressure autoclave and 1h/13c double-tuned resonator for chemistry and materials nuclear magnetic resonance spectroscopy and microscopy investigations Behr, Volker C.; Schmid, Martin W.; Franich, Robert A.; Meder, Roger in Concepts Magn. Reson. B Magn. Reson. Eng. (2013). 43B(2) 49–58.
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  Nuclear magnetic resonance spectroscopy and imaging are well-established tools in chemistry, physics, and life sciences. Nevertheless, most applications are performed at room temperature and atmospheric pressure. To study the processes in supercritical fluids, sample containers and coils have to be redesigned to especially allow for higher pressures up to several hundred times the atmospheric pressure. In this study, we present a setup for performing spectroscopic and imaging experiments on wood immersed in supercritical CO2 at up to 20 MPa for drying. A magnetic resonance-compatible autoclave as well as a double-tuned 1H/13C-birdcage coil was designed and a setup for regulating pressure and storing gases was assembled. We were able to successfully perform measurements on the wood and water during the drying process and gaininsights into the displacement of water and its chemical reactions with the highly pressurized CO2.

  @article{behr2013advanced, abstract = {Nuclear magnetic resonance spectroscopy and imaging are well-established tools in chemistry, physics, and life sciences. Nevertheless, most applications are performed at room temperature and atmospheric pressure. To study the processes in supercritical fluids, sample containers and coils have to be redesigned to especially allow for higher pressures up to several hundred times the atmospheric pressure. In this study, we present a setup for performing spectroscopic and imaging experiments on wood immersed in supercritical CO2 at up to 20 MPa for drying. A magnetic resonance-compatible autoclave as well as a double-tuned 1H/13C-birdcage coil was designed and a setup for regulating pressure and storing gases was assembled. We were able to successfully perform measurements on the wood and water during the drying process and gaininsights into the displacement of water and its chemical reactions with the highly pressurized CO2.}, author = {Behr, Volker C. and Schmid, Martin W. and Franich, Robert A. and Meder, Roger}, journal = {Concepts Magn. Reson. B Magn. Reson. Eng.}, keywords = {peer}, month = 4, number = 2, pages = {49-58}, title = {An advanced, integrated large-volume high-pressure autoclave and 1h/13c double-tuned resonator for chemistry and materials nuclear magnetic resonance spectroscopy and microscopy investigations}, volume = {43B}, year = 2013 }

  %0 Journal Article %1 behr2013advanced %A Behr, Volker C. %A Schmid, Martin W. %A Franich, Robert A. %A Meder, Roger %D 2013 %J Concepts Magn. Reson. B Magn. Reson. Eng. %N 2 %P 49-58 %R 10.1002/cmr.b.21233 %T An advanced, integrated large-volume high-pressure autoclave and 1h/13c double-tuned resonator for chemistry and materials nuclear magnetic resonance spectroscopy and microscopy investigations %V 43B %X Nuclear magnetic resonance spectroscopy and imaging are well-established tools in chemistry, physics, and life sciences. Nevertheless, most applications are performed at room temperature and atmospheric pressure. To study the processes in supercritical fluids, sample containers and coils have to be redesigned to especially allow for higher pressures up to several hundred times the atmospheric pressure. In this study, we present a setup for performing spectroscopic and imaging experiments on wood immersed in supercritical CO2 at up to 20 MPa for drying. A magnetic resonance-compatible autoclave as well as a double-tuned 1H/13C-birdcage coil was designed and a setup for regulating pressure and storing gases was assembled. We were able to successfully perform measurements on the wood and water during the drying process and gaininsights into the displacement of water and its chemical reactions with the highly pressurized CO2.

• Nonlinear split-ring metamaterial slabs for magnetic resonance imaging Lopez, Marcos A.; Freire, Manuel J.; Algarin, Jose M.; Behr, Volker C.; Jakob, Peter M.; Marqués, Ricardo in Appl. Phys. Lett. (2011). 98(13) 133508.
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  This work analyzes the ability of split-ring metamaterial slabs with zero/high permeability to reject/confine the radiofrequency magnetic field in magnetic resonance imaging systems. Split-ring slabs are designed and fabricated to work in a 1.5 T system. Nonlinear elements consisting of pairs of crossed diodes are inserted in the split-rings, so that the slab permeability can be switched between a value close to unity when interacting with the strong field of the transmitting coil, and zero or high values when interacting with the weak field produced by protons in tissue. Experiments are shown where these slabs locally increase the signal-to-noise-ratio.

  @article{lopez2011nonlinear, abstract = {This work analyzes the ability of split-ring metamaterial slabs with zero/high permeability to reject/confine the radiofrequency magnetic field in magnetic resonance imaging systems. Split-ring slabs are designed and fabricated to work in a 1.5 T system. Nonlinear elements consisting of pairs of crossed diodes are inserted in the split-rings, so that the slab permeability can be switched between a value close to unity when interacting with the strong field of the transmitting coil, and zero or high values when interacting with the weak field produced by protons in tissue. Experiments are shown where these slabs locally increase the signal-to-noise-ratio.}, author = {Lopez, Marcos A. and Freire, Manuel J. and Algarin, Jose M. and Behr, Volker C. and Jakob, Peter M. and Marqués, Ricardo}, journal = {Appl. Phys. Lett.}, keywords = {peer}, month = 3, number = 13, pages = 133508, title = {Nonlinear split-ring metamaterial slabs for magnetic resonance imaging}, volume = 98, year = 2011 }

  %0 Journal Article %1 lopez2011nonlinear %A Lopez, Marcos A. %A Freire, Manuel J. %A Algarin, Jose M. %A Behr, Volker C. %A Jakob, Peter M. %A Marqués, Ricardo %D 2011 %J Appl. Phys. Lett. %N 13 %P 133508 %R 10.1063/1.3574916 %T Nonlinear split-ring metamaterial slabs for magnetic resonance imaging %V 98 %X This work analyzes the ability of split-ring metamaterial slabs with zero/high permeability to reject/confine the radiofrequency magnetic field in magnetic resonance imaging systems. Split-ring slabs are designed and fabricated to work in a 1.5 T system. Nonlinear elements consisting of pairs of crossed diodes are inserted in the split-rings, so that the slab permeability can be switched between a value close to unity when interacting with the strong field of the transmitting coil, and zero or high values when interacting with the weak field produced by protons in tissue. Experiments are shown where these slabs locally increase the signal-to-noise-ratio.
• Analysis of the resolution of split-ring metamaterial lenses with application in parallel magnetic resonance imaging Algarin, Jose M.; Freire, Manuel J.; Lopez, Marcos A.; Lapine, Mikhail; Jakob, Peter M.; Behr, Volker C.; Marqués, Ricardo in Appl. Phys. Lett. (2011). 98(1) 014105.
  • [ Abstract ]
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  In this work, we experimentally determine the resolution of split-ring metamaterials lenses with emphasis in magnetic resonance imaging applications. Two small sources are used to determine the minimal resolution of the lens, which is compared with previous theoretical predictions. Taking into account this minimal resolution, a second experiment is designed in order to study the ability of a split-ring lens to improve the localization of the field produced by two closely spaced coils. This ability could find application in parallel magnetic resonance imaging, which take advantage of the distinct coil sensitivities in order to reduce the image acquisition time.

  @article{algarin2011analysis, abstract = {In this work, we experimentally determine the resolution of split-ring metamaterials lenses with emphasis in magnetic resonance imaging applications. Two small sources are used to determine the minimal resolution of the lens, which is compared with previous theoretical predictions. Taking into account this minimal resolution, a second experiment is designed in order to study the ability of a split-ring lens to improve the localization of the field produced by two closely spaced coils. This ability could find application in parallel magnetic resonance imaging, which take advantage of the distinct coil sensitivities in order to reduce the image acquisition time.}, author = {Algarin, Jose M. and Freire, Manuel J. and Lopez, Marcos A. and Lapine, Mikhail and Jakob, Peter M. and Behr, Volker C. and Marqués, Ricardo}, journal = {Appl. Phys. Lett.}, keywords = {peer}, month = 1, number = 1, pages = {014105}, title = {Analysis of the resolution of split-ring metamaterial lenses with application in parallel magnetic resonance imaging}, volume = 98, year = 2011 }

  %0 Journal Article %1 algarin2011analysis %A Algarin, Jose M. %A Freire, Manuel J. %A Lopez, Marcos A. %A Lapine, Mikhail %A Jakob, Peter M. %A Behr, Volker C. %A Marqués, Ricardo %D 2011 %J Appl. Phys. Lett. %N 1 %P 014105 %R 10.1063/1.3533394 %T Analysis of the resolution of split-ring metamaterial lenses with application in parallel magnetic resonance imaging %V 98 %X In this work, we experimentally determine the resolution of split-ring metamaterials lenses with emphasis in magnetic resonance imaging applications. Two small sources are used to determine the minimal resolution of the lens, which is compared with previous theoretical predictions. Taking into account this minimal resolution, a second experiment is designed in order to study the ability of a split-ring lens to improve the localization of the field produced by two closely spaced coils. This ability could find application in parallel magnetic resonance imaging, which take advantage of the distinct coil sensitivities in order to reduce the image acquisition time.

• Enhanced cortical reperfusion protects coagulation factor XII-deficient mice from ischemic stroke as revealed by high-field MRI Pham, M.; Kleinschnitz, C.; Helluy, X.; Bartsch, A.J.; Austinat, M.; Behr, V.C.; Renné, T.; Nieswandt, B.; Stoll, G.; Bendszus, M. in NeuroImage (2010). 49(4) 2907–2914.
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  Intrinsic coagulation factor XII deficient (FXII−/−) mice are protected from ischemic stroke. To elucidate underlying mechanisms we investigated the early ischemic period in vivo by multimodal magnetic resonance imaging (MRI) at 17.6 Tesla. Cerebral ischemia was induced by either transient (60 min) or permanent occlusion of the middle cerebral artery (t/pMCAO). 10 FXII−/− mice underwent t- , 10 FXII−/− mice p- and 10 Wildtype (Wt) mice tMCAO. Cerebral blood flow (CBF), diffusion-weighted-imaging (DWI) and T2-relaxometry were measured at 2 h and 24 h after MCAO. Outcome measures were evaluated after motion correction and normalization to atlas space. 2 h after tMCAO CBF reduction was similar in FXII−/− and Wt mice extending over cortical (CBF (ml/100 g/min) 33.6 ± 6.9 vs. 35.3 ± 4.6, p = 0.42) and subcortical regions (25.7 ± 4.5 vs. 31.6 ± 4.0, p = 0.17). At 24 h, recovery of cortical CBF by +36% was observed only in tMCAO FXII−/− mice contrasting a further decrease of – 30% in Wt mice after tMCAO (p = 0.02, F(1,18) = 6.24). In FXII−/− mice in which patency of the MCA was not restored (pMCAO) a further decrease of − 75% was observed. Cortical reperfusion in tMCAO FXII−/− mice was related to a lower risk of infarction of 59% vs. 93% in Wt mice (p = 0.04). Subcortical CBF was similarly decreased in both tMCAO groups (Wt and FXII−/−) relating to a similar risk of infarction of 89% (Wt) vs. 99% (FXII−/−, p = 0.17). Deficiency of FXII allows neocortical reperfusion after tMCAO and rescues brain tissue by this mechanism. This study supports the concept of FXII as a promising new target for stroke prevention and therapy.

  @article{Pham_2010, abstract = {Intrinsic coagulation factor XII deficient (FXII−/−) mice are protected from ischemic stroke. To elucidate underlying mechanisms we investigated the early ischemic period in vivo by multimodal magnetic resonance imaging (MRI) at 17.6 Tesla. Cerebral ischemia was induced by either transient (60 min) or permanent occlusion of the middle cerebral artery (t/pMCAO). 10 FXII−/− mice underwent t- , 10 FXII−/− mice p- and 10 Wildtype (Wt) mice tMCAO. Cerebral blood flow (CBF), diffusion-weighted-imaging (DWI) and T2-relaxometry were measured at 2 h and 24 h after MCAO. Outcome measures were evaluated after motion correction and normalization to atlas space. 2 h after tMCAO CBF reduction was similar in FXII−/− and Wt mice extending over cortical (CBF (ml/100 g/min) 33.6 ± 6.9 vs. 35.3 ± 4.6, p = 0.42) and subcortical regions (25.7 ± 4.5 vs. 31.6 ± 4.0, p = 0.17). At 24 h, recovery of cortical CBF by +36% was observed only in tMCAO FXII−/− mice contrasting a further decrease of – 30% in Wt mice after tMCAO (p = 0.02, F(1,18) = 6.24). In FXII−/− mice in which patency of the MCA was not restored (pMCAO) a further decrease of − 75% was observed. Cortical reperfusion in tMCAO FXII−/− mice was related to a lower risk of infarction of 59% vs. 93% in Wt mice (p = 0.04). Subcortical CBF was similarly decreased in both tMCAO groups (Wt and FXII−/−) relating to a similar risk of infarction of 89% (Wt) vs. 99% (FXII−/−, p = 0.17). Deficiency of FXII allows neocortical reperfusion after tMCAO and rescues brain tissue by this mechanism. This study supports the concept of FXII as a promising new target for stroke prevention and therapy.}, author = {Pham, M. and Kleinschnitz, C. and Helluy, X. and Bartsch, A.J. and Austinat, M. and Behr, V.C. and Renné, T. and Nieswandt, B. and Stoll, G. and Bendszus, M.}, journal = {NeuroImage}, keywords = {peer}, month = 2, number = 4, pages = {2907-2914}, title = {Enhanced cortical reperfusion protects coagulation factor XII-deficient mice from ischemic stroke as revealed by high-field MRI}, volume = 49, year = 2010 }

  %0 Journal Article %1 Pham_2010 %A Pham, M. %A Kleinschnitz, C. %A Helluy, X. %A Bartsch, A.J. %A Austinat, M. %A Behr, V.C. %A Renné, T. %A Nieswandt, B. %A Stoll, G. %A Bendszus, M. %D 2010 %J NeuroImage %N 4 %P 2907-2914 %R 10.1016/j.neuroimage.2009.11.061 %T Enhanced cortical reperfusion protects coagulation factor XII-deficient mice from ischemic stroke as revealed by high-field MRI %V 49 %X Intrinsic coagulation factor XII deficient (FXII−/−) mice are protected from ischemic stroke. To elucidate underlying mechanisms we investigated the early ischemic period in vivo by multimodal magnetic resonance imaging (MRI) at 17.6 Tesla. Cerebral ischemia was induced by either transient (60 min) or permanent occlusion of the middle cerebral artery (t/pMCAO). 10 FXII−/− mice underwent t- , 10 FXII−/− mice p- and 10 Wildtype (Wt) mice tMCAO. Cerebral blood flow (CBF), diffusion-weighted-imaging (DWI) and T2-relaxometry were measured at 2 h and 24 h after MCAO. Outcome measures were evaluated after motion correction and normalization to atlas space. 2 h after tMCAO CBF reduction was similar in FXII−/− and Wt mice extending over cortical (CBF (ml/100 g/min) 33.6 ± 6.9 vs. 35.3 ± 4.6, p = 0.42) and subcortical regions (25.7 ± 4.5 vs. 31.6 ± 4.0, p = 0.17). At 24 h, recovery of cortical CBF by +36% was observed only in tMCAO FXII−/− mice contrasting a further decrease of – 30% in Wt mice after tMCAO (p = 0.02, F(1,18) = 6.24). In FXII−/− mice in which patency of the MCA was not restored (pMCAO) a further decrease of − 75% was observed. Cortical reperfusion in tMCAO FXII−/− mice was related to a lower risk of infarction of 59% vs. 93% in Wt mice (p = 0.04). Subcortical CBF was similarly decreased in both tMCAO groups (Wt and FXII−/−) relating to a similar risk of infarction of 89% (Wt) vs. 99% (FXII−/−, p = 0.17). Deficiency of FXII allows neocortical reperfusion after tMCAO and rescues brain tissue by this mechanism. This study supports the concept of FXII as a promising new target for stroke prevention and therapy.

• Sensitive J-coupled metabolite mapping using Sel-MQC with selective multi-spin-echo readout Melkus, Gerd; Mörchel, Philipp; Behr, Volker C.; Kotas, Markus; Flentje, Michael; Jakob, Peter M. in Magn. Reson. Med. (2009). 62(4) 880–887.
  • [ Abstract ]
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  The selective multiple quantum coherence technique is combined with a read gradient to accelerate the measurement of a specific scalar-coupled metabolite. The sensitivities of the localization using pure phase encoding and localization with the read gradient are compared in experiments at high magnetic field strength (17.6 T). Multiple spin-echoes of the selective multiple quantum coherence edited metabolite are acquired using frequency-selective refocusing of the specified molecule group. The frequency-selective refocusing does not affect the J-modulation of a coupled spin system, and the echo time is not limited to a multiple of 1/J to acquire pure in-phase or antiphase signal. The multiple echoes can be used to accelerate the metabolite imaging experiment or to measure the apparent transverse relaxation T2. A simple phase-shifting scheme is presented, which enables the suppression of editing artifacts resulting from the multiple spin-echoes of the water resonance. The experiments are carried out on phantoms, in which lactate and polyunsaturated fatty acids are edited, and in vivo on tumors, in which lactate content and T2 are imaged. The method is of particular interest when a fast and sensitive selective multiple quantum coherence editing is necessary, e.g., for spatial three dimensional experiments.

  @article{melkus2009sensitive, abstract = {The selective multiple quantum coherence technique is combined with a read gradient to accelerate the measurement of a specific scalar-coupled metabolite. The sensitivities of the localization using pure phase encoding and localization with the read gradient are compared in experiments at high magnetic field strength (17.6 T). Multiple spin-echoes of the selective multiple quantum coherence edited metabolite are acquired using frequency-selective refocusing of the specified molecule group. The frequency-selective refocusing does not affect the J-modulation of a coupled spin system, and the echo time is not limited to a multiple of 1/J to acquire pure in-phase or antiphase signal. The multiple echoes can be used to accelerate the metabolite imaging experiment or to measure the apparent transverse relaxation T2. A simple phase-shifting scheme is presented, which enables the suppression of editing artifacts resulting from the multiple spin-echoes of the water resonance. The experiments are carried out on phantoms, in which lactate and polyunsaturated fatty acids are edited, and in vivo on tumors, in which lactate content and T2 are imaged. The method is of particular interest when a fast and sensitive selective multiple quantum coherence editing is necessary, e.g., for spatial three dimensional experiments.}, author = {Melkus, Gerd and Mörchel, Philipp and Behr, Volker C. and Kotas, Markus and Flentje, Michael and Jakob, Peter M.}, journal = {Magn. Reson. Med.}, keywords = {peer}, number = 4, pages = {880-887}, title = {Sensitive J-coupled metabolite mapping using Sel-MQC with selective multi-spin-echo readout}, volume = 62, year = 2009 }

  %0 Journal Article %1 melkus2009sensitive %A Melkus, Gerd %A Mörchel, Philipp %A Behr, Volker C. %A Kotas, Markus %A Flentje, Michael %A Jakob, Peter M. %D 2009 %J Magn. Reson. Med. %N 4 %P 880-887 %R 10.1002/mrm.22108 %T Sensitive J-coupled metabolite mapping using Sel-MQC with selective multi-spin-echo readout %V 62 %X The selective multiple quantum coherence technique is combined with a read gradient to accelerate the measurement of a specific scalar-coupled metabolite. The sensitivities of the localization using pure phase encoding and localization with the read gradient are compared in experiments at high magnetic field strength (17.6 T). Multiple spin-echoes of the selective multiple quantum coherence edited metabolite are acquired using frequency-selective refocusing of the specified molecule group. The frequency-selective refocusing does not affect the J-modulation of a coupled spin system, and the echo time is not limited to a multiple of 1/J to acquire pure in-phase or antiphase signal. The multiple echoes can be used to accelerate the metabolite imaging experiment or to measure the apparent transverse relaxation T2. A simple phase-shifting scheme is presented, which enables the suppression of editing artifacts resulting from the multiple spin-echoes of the water resonance. The experiments are carried out on phantoms, in which lactate and polyunsaturated fatty acids are edited, and in vivo on tumors, in which lactate content and T2 are imaged. The method is of particular interest when a fast and sensitive selective multiple quantum coherence editing is necessary, e.g., for spatial three dimensional experiments.

• Short-echo spectroscopic imaging combined with lactate editing in a single scan Melkus, Gerd; Mörchel, Philipp; Behr, Volker C.; Kotas, Markus; Flentje, Michael; Jakob, Peter M. in NMR Biomed. (2008). 21(10) 1076–1086.
  • [ Abstract ]
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  A short-echo spectroscopic imaging sequence extended with a frequency-selective multiple-quantum- coherence technique (Sel-MQC) is presented. The method enables acquisition of a complete water-suppressed proton spectrum with a short echo time and filtering of the J-coupling metabolite, lactate, from co-resonant lipids in one scan. The purpose of the study was to validate this combined pulse sequence in vitro and in vivo. Measurements on phantoms confirmed the feasibility of the method, and, for a practical in vivo application, experiments were carried out on eight tumors from two different tumor models [UT-SCC-8 (n = 4) and SAS (n = 4)]. T1- and T2-weighted metabolite and lipid ratios were calculated, and the tumors showed different values in the central and outer regions. The ratio of the lipid methylene peak area (1.30 ppm) to choline peak area (3.20 ppm) was significantly (p < 0.01) different in the central tumor area between the two models, and lactate was detected in only three out of four tumors in the SAS tumor line. The present approach of combining short-echo spectroscopic imaging and lactate editing allows the characterization of tumor-specific metabolites such as choline, lipid methylene and methyl resonances as well as lactate in a single scan.

  @article{melkus2008shortecho, abstract = {A short-echo spectroscopic imaging sequence extended with a frequency-selective multiple-quantum- coherence technique (Sel-MQC) is presented. The method enables acquisition of a complete water-suppressed proton spectrum with a short echo time and filtering of the J-coupling metabolite, lactate, from co-resonant lipids in one scan. The purpose of the study was to validate this combined pulse sequence in vitro and in vivo. Measurements on phantoms confirmed the feasibility of the method, and, for a practical in vivo application, experiments were carried out on eight tumors from two different tumor models [UT-SCC-8 (n = 4) and SAS (n = 4)]. T1- and T2-weighted metabolite and lipid ratios were calculated, and the tumors showed different values in the central and outer regions. The ratio of the lipid methylene peak area (1.30 ppm) to choline peak area (3.20 ppm) was significantly (p < 0.01) different in the central tumor area between the two models, and lactate was detected in only three out of four tumors in the SAS tumor line. The present approach of combining short-echo spectroscopic imaging and lactate editing allows the characterization of tumor-specific metabolites such as choline, lipid methylene and methyl resonances as well as lactate in a single scan.}, author = {Melkus, Gerd and Mörchel, Philipp and Behr, Volker C. and Kotas, Markus and Flentje, Michael and Jakob, Peter M.}, journal = {NMR Biomed.}, keywords = {peer}, month = 12, number = 10, pages = {1076-1086}, title = {Short-echo spectroscopic imaging combined with lactate editing in a single scan}, volume = 21, year = 2008 }

  %0 Journal Article %1 melkus2008shortecho %A Melkus, Gerd %A Mörchel, Philipp %A Behr, Volker C. %A Kotas, Markus %A Flentje, Michael %A Jakob, Peter M. %D 2008 %J NMR Biomed. %N 10 %P 1076-1086 %R 10.1002/nbm.1284 %T Short-echo spectroscopic imaging combined with lactate editing in a single scan %V 21 %X A short-echo spectroscopic imaging sequence extended with a frequency-selective multiple-quantum- coherence technique (Sel-MQC) is presented. The method enables acquisition of a complete water-suppressed proton spectrum with a short echo time and filtering of the J-coupling metabolite, lactate, from co-resonant lipids in one scan. The purpose of the study was to validate this combined pulse sequence in vitro and in vivo. Measurements on phantoms confirmed the feasibility of the method, and, for a practical in vivo application, experiments were carried out on eight tumors from two different tumor models [UT-SCC-8 (n = 4) and SAS (n = 4)]. T1- and T2-weighted metabolite and lipid ratios were calculated, and the tumors showed different values in the central and outer regions. The ratio of the lipid methylene peak area (1.30 ppm) to choline peak area (3.20 ppm) was significantly (p < 0.01) different in the central tumor area between the two models, and lactate was detected in only three out of four tumors in the SAS tumor line. The present approach of combining short-echo spectroscopic imaging and lactate editing allows the characterization of tumor-specific metabolites such as choline, lipid methylene and methyl resonances as well as lactate in a single scan.
• A novel modular probe base design Behr, Volker C.; Kaufmann, Ilja; Haase, Axel; Jakob, Peter M. in Concepts Magn. Reson. B Magn. Reson. Eng. (2008). 33B(1) 55–61.
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  Commercially available probe bases often impose limitations for their use with different setups. The goal of this work was to design and construct a universally applicable probe base to be used in radio frequency (rf) applications such as NMR imaging and spectroscopy. The concept is to support several arbitrarily combinable rf channels as well as additional devices, for example, a climate chamber for plants, an animal handling system, a perfusion device, or further specialized equipment. The concept and a prototype of such a probe base were successfully developed and are presented in this work.

  @article{behr2008novel, abstract = {Commercially available probe bases often impose limitations for their use with different setups. The goal of this work was to design and construct a universally applicable probe base to be used in radio frequency (rf) applications such as NMR imaging and spectroscopy. The concept is to support several arbitrarily combinable rf channels as well as additional devices, for example, a climate chamber for plants, an animal handling system, a perfusion device, or further specialized equipment. The concept and a prototype of such a probe base were successfully developed and are presented in this work.}, author = {Behr, Volker C. and Kaufmann, Ilja and Haase, Axel and Jakob, Peter M.}, journal = {Concepts Magn. Reson. B Magn. Reson. Eng.}, keywords = {peer}, month = 2, number = 1, pages = {55–61}, title = {A novel modular probe base design}, volume = {33B}, year = 2008 }

  %0 Journal Article %1 behr2008novel %A Behr, Volker C. %A Kaufmann, Ilja %A Haase, Axel %A Jakob, Peter M. %D 2008 %J Concepts Magn. Reson. B Magn. Reson. Eng. %N 1 %P 55–61 %R 10.1002/cmr.b.20107 %T A novel modular probe base design %V 33B %X Commercially available probe bases often impose limitations for their use with different setups. The goal of this work was to design and construct a universally applicable probe base to be used in radio frequency (rf) applications such as NMR imaging and spectroscopy. The concept is to support several arbitrarily combinable rf channels as well as additional devices, for example, a climate chamber for plants, an animal handling system, a perfusion device, or further specialized equipment. The concept and a prototype of such a probe base were successfully developed and are presented in this work.

• In Vivo High-Resolution MR Imaging of Neuropathologic Changes in the Injured Rat Spinal Cord Weber, T.; Vroemen, M.; Behr, V.; Neuberger, T.; Jakob, P.; Haase, A.; Schuierer, G.; Bogdahn, U.; Faber, C.; Weidner, N. in Am. J. Neuroradiol. (2006). 27(3) 598–604.
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  BACKGROUND AND PURPOSE: MR imaging is the most comprehensive noninvasive means to assess structural changes in injured central nervous system (CNS) tissue in humans over time. The few published in vivo MR imaging studies of spinal cord injury in rodent models by using field strengths ≤7T suffer from low spatial resolution, flow, and motion artifacts. The aim of this study was to assess the capacity of a 17.6T imaging system to detect pathologic changes occurring in a rat spinal cord contusion injury model ex vivo and in vivo. METHODS: Seven adult female Fischer 344 rats received contusion injuries at thoracic level T10, which caused severe and reproducible lesions of the injured spinal cord parenchyma. Two to 58 days postinjury, high-resolution MR imaging was performed ex vivo (2) or in vivo in anesthetized rats (5 spinal cord injured + one intact control animal) by using 2D multisection spin- and gradient-echo imaging sequences, respectively, combined with electrocardiogram triggering and respiratory gating. RESULTS: The acquired images provided excellent resolution and gray/white matter differentiation without significant artifacts. Signal intensity changes, which were detected with ex vivo and in vivo MR imaging following spinal cord injury, could be correlated with histologically defined structural changes such as edema, fibroglial scar, and hemorrhage. CONCLUSIONS: These results demonstrate that MR imaging at 17.6T allows high-resolution structural analysis of spinal cord pathology after injury.

  @article{weber2006highresolution, abstract = {BACKGROUND AND PURPOSE: MR imaging is the most comprehensive noninvasive means to assess structural changes in injured central nervous system (CNS) tissue in humans over time. The few published in vivo MR imaging studies of spinal cord injury in rodent models by using field strengths ≤7T suffer from low spatial resolution, flow, and motion artifacts. The aim of this study was to assess the capacity of a 17.6T imaging system to detect pathologic changes occurring in a rat spinal cord contusion injury model ex vivo and in vivo. METHODS: Seven adult female Fischer 344 rats received contusion injuries at thoracic level T10, which caused severe and reproducible lesions of the injured spinal cord parenchyma. Two to 58 days postinjury, high-resolution MR imaging was performed ex vivo (2) or in vivo in anesthetized rats (5 spinal cord injured + one intact control animal) by using 2D multisection spin- and gradient-echo imaging sequences, respectively, combined with electrocardiogram triggering and respiratory gating. RESULTS: The acquired images provided excellent resolution and gray/white matter differentiation without significant artifacts. Signal intensity changes, which were detected with ex vivo and in vivo MR imaging following spinal cord injury, could be correlated with histologically defined structural changes such as edema, fibroglial scar, and hemorrhage. CONCLUSIONS: These results demonstrate that MR imaging at 17.6T allows high-resolution structural analysis of spinal cord pathology after injury.}, author = {Weber, T. and Vroemen, M. and Behr, V. and Neuberger, T. and Jakob, P. and Haase, A. and Schuierer, G. and Bogdahn, U. and Faber, C. and Weidner, N.}, journal = {Am. J. Neuroradiol.}, keywords = {peer}, month = 3, number = 3, pages = {598-604}, title = {In Vivo High-Resolution MR Imaging of Neuropathologic Changes in the Injured Rat Spinal Cord}, volume = 27, year = 2006 }

  %0 Journal Article %1 weber2006highresolution %A Weber, T. %A Vroemen, M. %A Behr, V. %A Neuberger, T. %A Jakob, P. %A Haase, A. %A Schuierer, G. %A Bogdahn, U. %A Faber, C. %A Weidner, N. %D 2006 %J Am. J. Neuroradiol. %N 3 %P 598-604 %T In Vivo High-Resolution MR Imaging of Neuropathologic Changes in the Injured Rat Spinal Cord %U http://www.ajnr.org/content/27/3/598 %V 27 %X BACKGROUND AND PURPOSE: MR imaging is the most comprehensive noninvasive means to assess structural changes in injured central nervous system (CNS) tissue in humans over time. The few published in vivo MR imaging studies of spinal cord injury in rodent models by using field strengths ≤7T suffer from low spatial resolution, flow, and motion artifacts. The aim of this study was to assess the capacity of a 17.6T imaging system to detect pathologic changes occurring in a rat spinal cord contusion injury model ex vivo and in vivo. METHODS: Seven adult female Fischer 344 rats received contusion injuries at thoracic level T10, which caused severe and reproducible lesions of the injured spinal cord parenchyma. Two to 58 days postinjury, high-resolution MR imaging was performed ex vivo (2) or in vivo in anesthetized rats (5 spinal cord injured + one intact control animal) by using 2D multisection spin- and gradient-echo imaging sequences, respectively, combined with electrocardiogram triggering and respiratory gating. RESULTS: The acquired images provided excellent resolution and gray/white matter differentiation without significant artifacts. Signal intensity changes, which were detected with ex vivo and in vivo MR imaging following spinal cord injury, could be correlated with histologically defined structural changes such as edema, fibroglial scar, and hemorrhage. CONCLUSIONS: These results demonstrate that MR imaging at 17.6T allows high-resolution structural analysis of spinal cord pathology after injury.
• Transmit-Receive Coil-Arrays at 17.6T, Configurations for 1H, 23Na and 31P MRI Gareis, Daniel; Neuberger, Thomas; Behr, Volker C.; Jakob, Peter M.; Faber, C.; Griswold, Mark A. in Concepts Magn. Reson. B Magn. Reson. Eng. (2006). 29B(1) 20–27.
  • [ Abstract ]
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  Array coil imaging is a popular technique in whole-body MRI systems but has seldom been implemented in vertical bore high-field magnets. In this work, three transmit-receive phased arrays for 1H, 23Na, and 31P were built to examine the feasibility of using these arrays at the magnetic field strength of 17.6 Tesla. The coils were designed for in vivo applications on mice and rats with an inner diameter of 38 mm. Each array consisted of two surface coils. The decoupling of adjacent coils was achieved by a variable decoupling capacitor on the common conductor of the two surface-coils. The coils can be driven simultaneously to provide an area of relatively high transmit homogeneity using a relative phase shift between the coils. The area with best homogeneity changes, depending on this phase shift. Images were simultaneously acquired with two receivers and showed essentially no coupling between the two channels. The arrays provide an SNR-gain compared to a single-channel birdcage-volume resonator of up to 34% near the surface. The arrays are most suitable for objects near the coils with a penetration depth of up to 20 mm (e.g., the spinal cord or the brain of a rat)

  @article{gareis2006transmitreceive, abstract = {Array coil imaging is a popular technique in whole-body MRI systems but has seldom been implemented in vertical bore high-field magnets. In this work, three transmit-receive phased arrays for 1H, 23Na, and 31P were built to examine the feasibility of using these arrays at the magnetic field strength of 17.6 Tesla. The coils were designed for in vivo applications on mice and rats with an inner diameter of 38 mm. Each array consisted of two surface coils. The decoupling of adjacent coils was achieved by a variable decoupling capacitor on the common conductor of the two surface-coils. The coils can be driven simultaneously to provide an area of relatively high transmit homogeneity using a relative phase shift between the coils. The area with best homogeneity changes, depending on this phase shift. Images were simultaneously acquired with two receivers and showed essentially no coupling between the two channels. The arrays provide an SNR-gain compared to a single-channel birdcage-volume resonator of up to 34% near the surface. The arrays are most suitable for objects near the coils with a penetration depth of up to 20 mm (e.g., the spinal cord or the brain of a rat)}, author = {Gareis, Daniel and Neuberger, Thomas and Behr, Volker C. and Jakob, Peter M. and Faber, C. and Griswold, Mark A.}, journal = {Concepts Magn. Reson. B Magn. Reson. Eng.}, keywords = {peer}, month = 2, number = 1, pages = {20-27}, title = {Transmit-Receive Coil-Arrays at 17.6T, Configurations for 1H, 23Na and 31P MRI}, volume = {29B}, year = 2006 }

  %0 Journal Article %1 gareis2006transmitreceive %A Gareis, Daniel %A Neuberger, Thomas %A Behr, Volker C. %A Jakob, Peter M. %A Faber, C. %A Griswold, Mark A. %D 2006 %J Concepts Magn. Reson. B Magn. Reson. Eng. %N 1 %P 20-27 %R 10.1002/cmr.b.20055 %T Transmit-Receive Coil-Arrays at 17.6T, Configurations for 1H, 23Na and 31P MRI %V 29B %X Array coil imaging is a popular technique in whole-body MRI systems but has seldom been implemented in vertical bore high-field magnets. In this work, three transmit-receive phased arrays for 1H, 23Na, and 31P were built to examine the feasibility of using these arrays at the magnetic field strength of 17.6 Tesla. The coils were designed for in vivo applications on mice and rats with an inner diameter of 38 mm. Each array consisted of two surface coils. The decoupling of adjacent coils was achieved by a variable decoupling capacitor on the common conductor of the two surface-coils. The coils can be driven simultaneously to provide an area of relatively high transmit homogeneity using a relative phase shift between the coils. The area with best homogeneity changes, depending on this phase shift. Images were simultaneously acquired with two receivers and showed essentially no coupling between the two channels. The arrays provide an SNR-gain compared to a single-channel birdcage-volume resonator of up to 34% near the surface. The arrays are most suitable for objects near the coils with a penetration depth of up to 20 mm (e.g., the spinal cord or the brain of a rat)

• Inert fluorinated gas T1 calculator Kuethe, Dean O.; Pietraß, Tanja; Behr, Volker C. in J. Magn. Reson. (2005). 177(2) 212–220.
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  The physics of spin–rotation interaction in roughly spherical perfluorinated gas molecules has been studied extensively. But, it is difficult to calculate a spin–lattice relaxation time constant T1 for any given temperature and pressure using the published literature. We give a unified parameterization that makes use of the Clausius equation of state, Lennard-Jones collision dynamics, and a formulaic temperature dependence for collision cross section for rotational change. The model fits T1s for SF6, CF4, C2F6, and c-C4F8 for temperatures from 180 to 360 K and pressures from 2 to 210 kPa and in mixtures with other common gases to within our limits of measurement. It also fits previous data tabulated according to known number densities. Given a pressure, temperature, and mixture composition, one can now calculate T1s for common laboratory conditions with a known accuracy, typically 0.5%. Given the success of the model’s formulaic structure, it is likely to apply to even broader ranges of physical conditions and to other gases that relax by spin–rotation interaction.

  @article{kuethe2005inert, abstract = {The physics of spin–rotation interaction in roughly spherical perfluorinated gas molecules has been studied extensively. But, it is difficult to calculate a spin–lattice relaxation time constant T1 for any given temperature and pressure using the published literature. We give a unified parameterization that makes use of the Clausius equation of state, Lennard-Jones collision dynamics, and a formulaic temperature dependence for collision cross section for rotational change. The model fits T1s for SF6, CF4, C2F6, and c-C4F8 for temperatures from 180 to 360 K and pressures from 2 to 210 kPa and in mixtures with other common gases to within our limits of measurement. It also fits previous data tabulated according to known number densities. Given a pressure, temperature, and mixture composition, one can now calculate T1s for common laboratory conditions with a known accuracy, typically 0.5%. Given the success of the model’s formulaic structure, it is likely to apply to even broader ranges of physical conditions and to other gases that relax by spin–rotation interaction.}, author = {Kuethe, Dean O. and Pietraß, Tanja and Behr, Volker C.}, journal = {J. Magn. Reson.}, keywords = {peer}, month = 12, number = 2, pages = {212-220}, title = {Inert fluorinated gas T1 calculator}, volume = 177, year = 2005 }

  %0 Journal Article %1 kuethe2005inert %A Kuethe, Dean O. %A Pietraß, Tanja %A Behr, Volker C. %D 2005 %J J. Magn. Reson. %N 2 %P 212-220 %R 10.1016/j.jmr.2005.07.022 %T Inert fluorinated gas T1 calculator %V 177 %X The physics of spin–rotation interaction in roughly spherical perfluorinated gas molecules has been studied extensively. But, it is difficult to calculate a spin–lattice relaxation time constant T1 for any given temperature and pressure using the published literature. We give a unified parameterization that makes use of the Clausius equation of state, Lennard-Jones collision dynamics, and a formulaic temperature dependence for collision cross section for rotational change. The model fits T1s for SF6, CF4, C2F6, and c-C4F8 for temperatures from 180 to 360 K and pressures from 2 to 210 kPa and in mixtures with other common gases to within our limits of measurement. It also fits previous data tabulated according to known number densities. Given a pressure, temperature, and mixture composition, one can now calculate T1s for common laboratory conditions with a known accuracy, typically 0.5%. Given the success of the model’s formulaic structure, it is likely to apply to even broader ranges of physical conditions and to other gases that relax by spin–rotation interaction.

• High-resolution MR imaging of the rat spinal cord in vivo in a wide-bore magnet at 17.6 Tesla Behr, V. C.; Weber, T.; Neuberger, T.; Vroemen, M.; Weidner, N.; Bogdahn, U.; Haase, A.; Jakob, P. M.; Faber, C. in Magn. Reson. Mater. Phy. (2004). 17(3-6) 353–358.
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  The objective was to demonstrate the feasibility and to evaluate the performance of high-resolution in vivo magnetic resonance (MR) imaging of the rat spinal cord in a 17.6-T vertical wide-bore magnet. A probehead consisting of a surface coil that offers enlarged sample volume suitable for rats up to a weight of 220 g was designed. ECG triggered and respiratory-gated gradient echo experiments were performed on a Bruker Avance 750 wide-bore spectrometer for high-resolution imaging. With T2* values between 5 and 20 ms, good image contrast could be obtained using short echo times, which also minimizes motion artifacts. Anatomy of healthy spinal cords and pathomorphological changes in traumatically injured rat spinal cord in vivo could be visualized with microscopic detail. It was demonstrated that imaging of the rat spinal cord in vivo using a vertical wide-bore high-magnetic-field system is feasible. The potential to obtain high-resolution images in short scan times renders high-field imaging a powerful diagnostic tool.

  @article{behr2004highresolution, abstract = {The objective was to demonstrate the feasibility and to evaluate the performance of high-resolution in vivo magnetic resonance (MR) imaging of the rat spinal cord in a 17.6-T vertical wide-bore magnet. A probehead consisting of a surface coil that offers enlarged sample volume suitable for rats up to a weight of 220 g was designed. ECG triggered and respiratory-gated gradient echo experiments were performed on a Bruker Avance 750 wide-bore spectrometer for high-resolution imaging. With T2* values between 5 and 20 ms, good image contrast could be obtained using short echo times, which also minimizes motion artifacts. Anatomy of healthy spinal cords and pathomorphological changes in traumatically injured rat spinal cord in vivo could be visualized with microscopic detail. It was demonstrated that imaging of the rat spinal cord in vivo using a vertical wide-bore high-magnetic-field system is feasible. The potential to obtain high-resolution images in short scan times renders high-field imaging a powerful diagnostic tool.}, author = {Behr, V. C. and Weber, T. and Neuberger, T. and Vroemen, M. and Weidner, N. and Bogdahn, U. and Haase, A. and Jakob, P. M. and Faber, C.}, journal = {Magn. Reson. Mater. Phy.}, keywords = {peer}, month = 12, number = {3-6}, pages = {353–358}, title = {High-resolution MR imaging of the rat spinal cord in vivo in a wide-bore magnet at 17.6 Tesla}, volume = 17, year = 2004 }

  %0 Journal Article %1 behr2004highresolution %A Behr, V. C. %A Weber, T. %A Neuberger, T. %A Vroemen, M. %A Weidner, N. %A Bogdahn, U. %A Haase, A. %A Jakob, P. M. %A Faber, C. %D 2004 %J Magn. Reson. Mater. Phy. %N 3-6 %P 353–358 %R 10.1007/s10334-004-0057-5 %T High-resolution MR imaging of the rat spinal cord in vivo in a wide-bore magnet at 17.6 Tesla %V 17 %X The objective was to demonstrate the feasibility and to evaluate the performance of high-resolution in vivo magnetic resonance (MR) imaging of the rat spinal cord in a 17.6-T vertical wide-bore magnet. A probehead consisting of a surface coil that offers enlarged sample volume suitable for rats up to a weight of 220 g was designed. ECG triggered and respiratory-gated gradient echo experiments were performed on a Bruker Avance 750 wide-bore spectrometer for high-resolution imaging. With T2* values between 5 and 20 ms, good image contrast could be obtained using short echo times, which also minimizes motion artifacts. Anatomy of healthy spinal cords and pathomorphological changes in traumatically injured rat spinal cord in vivo could be visualized with microscopic detail. It was demonstrated that imaging of the rat spinal cord in vivo using a vertical wide-bore high-magnetic-field system is feasible. The potential to obtain high-resolution images in short scan times renders high-field imaging a powerful diagnostic tool.
• RF flux guides for excitation and reception in 31P spectroscopic and imaging experiments at 2 Tesla Behr, Volker C.; Haase, Axel; Jakob, Peter M. in Concepts Magn. Reson. B Magn. Reson. Eng. (2004). 23B(1) 44–49.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  • [ DOI ]
  Radio frequency (RF) flux guides consist of microstructured materials that are able to transport magnetic flux even within strong static magnetic fields, such as those found inside a superconducting magnet used for nuclear magnetic resonance (NMR) experiments. This offers the possibility to examine samples whose geometries impose restrictions on the direct accessibility of the sample. In these cases, flux guides can transmit the magnetic flux from a remote resonator into the sample, thereby occupying less space and allowing a wider range of coil designs. An RF flux guide is presented in 31P spectroscopic and imaging experiments on a clinical system operating at 2 T. It is employed for transmission of the excitation pulses as well as the received NMR signal. In this way, RF flux guide/coil combinations can be used in experiments with any nuclei without the need for an additional coil for excitation.

  @article{behr2004guides, abstract = {Radio frequency (RF) flux guides consist of microstructured materials that are able to transport magnetic flux even within strong static magnetic fields, such as those found inside a superconducting magnet used for nuclear magnetic resonance (NMR) experiments. This offers the possibility to examine samples whose geometries impose restrictions on the direct accessibility of the sample. In these cases, flux guides can transmit the magnetic flux from a remote resonator into the sample, thereby occupying less space and allowing a wider range of coil designs. An RF flux guide is presented in 31P spectroscopic and imaging experiments on a clinical system operating at 2 T. It is employed for transmission of the excitation pulses as well as the received NMR signal. In this way, RF flux guide/coil combinations can be used in experiments with any nuclei without the need for an additional coil for excitation.}, author = {Behr, Volker C. and Haase, Axel and Jakob, Peter M.}, journal = {Concepts Magn. Reson. B Magn. Reson. Eng.}, keywords = {peer}, month = 10, number = 1, pages = {44-49}, title = {RF flux guides for excitation and reception in 31P spectroscopic and imaging experiments at 2 Tesla}, volume = {23B}, year = 2004 }

  %0 Journal Article %1 behr2004guides %A Behr, Volker C. %A Haase, Axel %A Jakob, Peter M. %D 2004 %J Concepts Magn. Reson. B Magn. Reson. Eng. %N 1 %P 44-49 %R 10.1002/cmr.b.20019 %T RF flux guides for excitation and reception in 31P spectroscopic and imaging experiments at 2 Tesla %V 23B %X Radio frequency (RF) flux guides consist of microstructured materials that are able to transport magnetic flux even within strong static magnetic fields, such as those found inside a superconducting magnet used for nuclear magnetic resonance (NMR) experiments. This offers the possibility to examine samples whose geometries impose restrictions on the direct accessibility of the sample. In these cases, flux guides can transmit the magnetic flux from a remote resonator into the sample, thereby occupying less space and allowing a wider range of coil designs. An RF flux guide is presented in 31P spectroscopic and imaging experiments on a clinical system operating at 2 T. It is employed for transmission of the excitation pulses as well as the received NMR signal. In this way, RF flux guide/coil combinations can be used in experiments with any nuclei without the need for an additional coil for excitation.

• Volume of rat lungs measured throughout the respiratory cycle using 19F NMR of the inert gas SF6 Kuethe, Dean O.; Behr, Volker C.; Begay, Stephanie in Magn. Reson. Med. (2002). 48(3) 547–549.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  • [ DOI ]
  The lung volumes of mechanically ventilated rats were measured over the course of the respiratory cycle using the NMR signal strength from inhaled sulfurhexafluoride. Rats with elastase-induced emphysema showed larger lung volumes and slower exhalation than control rats. For humans the technique should be able to provide lung volume measurements at least 20 times a second.

  @article{kuethe2002volume, abstract = {The lung volumes of mechanically ventilated rats were measured over the course of the respiratory cycle using the NMR signal strength from inhaled sulfurhexafluoride. Rats with elastase-induced emphysema showed larger lung volumes and slower exhalation than control rats. For humans the technique should be able to provide lung volume measurements at least 20 times a second.}, author = {Kuethe, Dean O. and Behr, Volker C. and Begay, Stephanie}, journal = {Magn. Reson. Med.}, keywords = {peer}, month = 9, number = 3, pages = {547-549}, title = {Volume of rat lungs measured throughout the respiratory cycle using 19F NMR of the inert gas SF6}, volume = 48, year = 2002 }

  %0 Journal Article %1 kuethe2002volume %A Kuethe, Dean O. %A Behr, Volker C. %A Begay, Stephanie %D 2002 %J Magn. Reson. Med. %N 3 %P 547-549 %R 10.1002/mrm.10245 %T Volume of rat lungs measured throughout the respiratory cycle using 19F NMR of the inert gas SF6 %V 48 %X The lung volumes of mechanically ventilated rats were measured over the course of the respiratory cycle using the NMR signal strength from inhaled sulfurhexafluoride. Rats with elastase-induced emphysema showed larger lung volumes and slower exhalation than control rats. For humans the technique should be able to provide lung volume measurements at least 20 times a second.