B1 Inhomogeneity in the Thigh at 3T and Implications for Peripheral Vascular Imaging

Pippa Storey¹, Vivian S. Lee¹, Daniel K. Sodickson¹, Davide Santoro¹, Bei Zhang¹, Ruth P. Lim¹, Iliyana P. Atanasova¹, David R. Stoffel¹, Qun Chen¹, Graham C. Wiggins¹

Signal loss in the proximal right femoral artery is evident to some degree on contrast-enhanced MR angiograms, and to a greater extent on non-contrast MRA. Using 3D B1 mapping and RF field simulations, we show that the B1 profile exhibits a rotational symmetry in the thighs, with minima on the anterior medial side of the right leg, and the posterior medial side of the left leg. The fact that the proximal right femoral artery coincides with a B1 minimum explains the signal loss. We investigate the use of dielectric pads and a coupling coil to mitigate the problem.