Abstract #4406

Design of a universal RF-shimming drive mode for head and neck imaging at 7 Tesla using a 16-channel pTx array

Ehsan Kazemivalipour^1,2, Markus W. May^3,4, D. Rangaprakash^1,2, Berkin Bilgic^1,2,5, Jason P. Stockmann^1,2, Robert L. Barry^1,2, Boris Keil^6,7, Lawrence L. Wald^1,2,5, and Bastien Guerin^1,2

¹A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, ⁴High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, ⁵Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States, ⁶Institute of Medical Physics and Radiation Protection, Department of Life Science Engineering, Mittelhessen University of Applied Sciences, Giessen, Germany, ⁷Center for Mind, Brain and Behavior (CMBB), Philipps-University Marburg, Marburg, Germany

Synopsis

Keywords: RF Pulse Design & Fields, RF Pulse Design & FieldsWe calculate “universal” RF-shimming excitations that provide maximum B₁⁺ coverage and homogeneity across the brain & c-spine using a patient-friendly 16-channel pTx array. We simulated three body models and three z-positions to ensure robustness to both B₁⁺ and SAR variation across a range of head/neck sizes and shapes (universal design). We provide two solutions, both of which may be saved on the scanner: a low-SAR solution that improves flip-angle uniformity by 13% compared to the BC mode excitation (same SAR) and a high-SAR excitation that improves flip-angle non-uniformity by 25% at the cost of a 2x local SAR increase.

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