Vincent Oltman Boer1, Jan Ole Pedersen2, Nick Arango3, Irene Kuang3, Jason Stockmann4,5, Esben Thade Petersen6,7. 1. Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, section 714, Kettegård Allé 30, 2650, Hvidovre, Hvidovre, Denmark. vincentob@drcmr.dk. 2. Philips Healthcare, Copenhagen, Denmark. 3. Massachusetts Institute of Technology, Cambridge, MA, USA. 4. Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA. 5. Harvard Medical School, Boston, MA, USA. 6. Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, section 714, Kettegård Allé 30, 2650, Hvidovre, Hvidovre, Denmark. 7. Department of Health Technology, Centre for Magnetic Resonance, Technical University of Denmark, Kgs. Lyngby, Denmark.
Abstract
OBJECT: Improve shimming capabilities of ultra-high field systems, with addition of an accessible low-complexity B0 shim array for head MRI at 7 T. MATERIALS AND METHODS: An eight channel B0 shim coil array was designed as a tradeoff between shimming improvement and construction complexity, to provide an easy to use shim array that can be employed with the standard 7 T head coil. The array was interfaced using an open-source eight-channel shim amplifier rack. Improvements in field homogeneity for whole-brain and slice-based shimming were compared to standard second-order shimming, and to more complex higher order dynamic shimming and shim arrays with 32 and 48 channels. RESULTS: The eight-channel shim array provided 12% improvement in whole brain static shimming and provided 33% improvement when using slice-based shimming. With this, the eight-channel array performed similar to third-order dynamic shimming (without the need for higher order eddy current compensation). More complex shim arrays with 32 and 48 channels performed better, but require a dedicated RF coil. DISCUSSION: The designed eight-channel shim array provides a low-complexity and low-cost approach for improving B0 field shimming on an ultra-high field system. In both static and dynamic shimming, it provides improved B0 homogeneity over standard shimming.
OBJECT: Improve shimming capabilities of ultra-high field systems, with addition of an accessible low-complexity B0 shim array for head MRI at 7 T. MATERIALS AND METHODS: An eight channel B0 shim coil array was designed as a tradeoff between shimming improvement and construction complexity, to provide an easy to use shim array that can be employed with the standard 7 T head coil. The array was interfaced using an open-source eight-channel shim amplifier rack. Improvements in field homogeneity for whole-brain and slice-based shimming were compared to standard second-order shimming, and to more complex higher order dynamic shimming and shim arrays with 32 and 48 channels. RESULTS: The eight-channel shim array provided 12% improvement in whole brain static shimming and provided 33% improvement when using slice-based shimming. With this, the eight-channel array performed similar to third-order dynamic shimming (without the need for higher order eddy current compensation). More complex shim arrays with 32 and 48 channels performed better, but require a dedicated RF coil. DISCUSSION: The designed eight-channel shim array provides a low-complexity and low-cost approach for improving B0 field shimming on an ultra-high field system. In both static and dynamic shimming, it provides improved B0 homogeneity over standard shimming.
Authors: Ariane Fillmer; Signe Johanna Vannesjo; Matteo Pavan; Milan Scheidegger; Klaas Paul Pruessmann; Anke Henning Journal: Magn Reson Med Date: 2015-05-07 Impact factor: 4.668
Authors: Cristina Cudalbu; Kevin L Behar; Pallab K Bhattacharyya; Wolfgang Bogner; Tamas Borbath; Robin A de Graaf; Rolf Gruetter; Anke Henning; Christoph Juchem; Roland Kreis; Phil Lee; Hongxia Lei; Małgorzata Marjańska; Ralf Mekle; Saipavitra Murali-Manohar; Michal Považan; Veronika Rackayová; Dunja Simicic; Johannes Slotboom; Brian J Soher; Zenon Starčuk; Jana Starčuková; Ivan Tkáč; Stephen Williams; Martin Wilson; Andrew Martin Wright; Lijing Xin; Vladimír Mlynárik Journal: NMR Biomed Date: 2020-11-25 Impact factor: 4.044