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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