Jiazheng Zhou1,2, Jason P Stockmann3,4, Nicolas Arango3,5, Thomas Witzel3,4, Klaus Scheffler1,6, Lawrence L Wald3,4, Fa-Hsuan Lin7,8,9. 1. High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany. 2. Graduate Training Center of Neuroscience, IMPRS, University of Tübingen, Tübingen, Germany. 3. A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts. 4. Harvard Medical School, Boston, Massachusetts. 5. Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts. 6. Biomedical Magnetic Resonance, University Hospital Tübingen (UKT), Tübingen, Germany. 7. Department of Medical Biophysics, University of Toronto, Toronto, Canada. 8. Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada. 9. Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland.
Abstract
PURPOSE: We designed and implemented an orthogonal shim array consisting of shim coils with their planes perpendicular to the planes of neighboring RF coils. This shim coil improves the magnetic field homogeneity by minimizing the interference to RF coils. METHODS: Using realistic off-resonance maps of the human brain, we first evaluated the performance of shim coils in different orientations. Based on simulations, we developed a 7-channel orthogonal shim array, whose coil plan was perpendicular to neighboring RF coils, at the forehead. A programmable open-source current driver supplied shim currents. RESULTS: The 7-channel orthogonal shim array caused only marginal SNR loss to the integrated 32-channel RF-shim array. The 7-channel orthogonal shim array itself improved the magnetic field homogeneity by 30% in slice-optimized shimming, comparable to the baseline shimming offered by the scanner's 2nd order spherical harmonic shimming. CONCLUSION: Orthogonal shim coils can improve the field homogeneity while maintaining high image SNR.
PURPOSE: We designed and implemented an orthogonal shim array consisting of shim coils with their planes perpendicular to the planes of neighboring RF coils. This shim coil improves the magnetic field homogeneity by minimizing the interference to RF coils. METHODS: Using realistic off-resonance maps of the human brain, we first evaluated the performance of shim coils in different orientations. Based on simulations, we developed a 7-channel orthogonal shim array, whose coil plan was perpendicular to neighboring RF coils, at the forehead. A programmable open-source current driver supplied shim currents. RESULTS: The 7-channel orthogonal shim array caused only marginal SNR loss to the integrated 32-channel RF-shim array. The 7-channel orthogonal shim array itself improved the magnetic field homogeneity by 30% in slice-optimized shimming, comparable to the baseline shimming offered by the scanner's 2nd order spherical harmonic shimming. CONCLUSION: Orthogonal shim coils can improve the field homogeneity while maintaining high image SNR.
Authors: Christoph Juchem; Terence W Nixon; Scott McIntyre; Douglas L Rothman; Robin A de Graaf Journal: J Magn Reson Date: 2010-03-11 Impact factor: 2.229
Authors: Michael Schwerter; Hoby Hetherington; Chan Hong Moon; Jullie Pan; Jörg Felder; Lutz Tellmann; N Jon Shah Journal: Magn Reson Med Date: 2019-03-18 Impact factor: 4.668
Authors: Christoph Juchem; Terence W Nixon; Scott McIntyre; Douglas L Rothman; Robin A de Graaf Journal: Magn Reson Med Date: 2010-01 Impact factor: 4.668
Authors: Hoby P Hetherington; Chan Hong Moon; Michael Schwerter; Nadim Joni Shah; Jullie W Pan Journal: Magn Reson Med Date: 2020-08-28 Impact factor: 4.668