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Abstract #4686

Implications of within-scan patient head motion on B1+ homogeneity and Specific Absorption Rate at 7T

Emre Kopanoglu1, Alix Jean Deeley Plumley1, M. Arcan Erturk2, Cem M. Deniz3, and Richard G. Wise1

1CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 3Department of Radiology, School of Medicine, New York University, New York, NY, United States

Parallel-transmit pulses are commonly used to improve B1+-homogeneity at higher field strengths, while local-SAR constraints are applied to ensure safety. However, patient motion may become unavoidable with longer scans or less cooperative patients, and motion may affect B1+-homogeneity and local-SAR. We investigated the effect of all 6 degrees-of-freedom of head motion on B1+-homogeneity and local-SAR for parallel-transmit multi-spoke pulses using simulations. We observed more than a 2-fold increase in local-SAR due to motion for some pulses. We also investigated the changes in B1+-homogeneity of spokes pulses using in-vivo B1+-maps and showed regional variations between 12%-22% in the excitation profile.

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