Dynamically Applied Multiple B1+ Shimming Scheme for Arterial Spin Labeling of the Prostate at 7T

Xiufeng Li¹, Pierre-Francois Van de Moortele¹, Kamil Ugurbil¹, Greg Metzger¹

The destructive interference of RF pulses is one well-known challenge for ultrahigh field MR imaging. B1+ shimming for the target anatomy alone is not sufficient for ASL, where each RF pulse in the sequence has varying requirements with respect to B1+ amplitude, homogeneity, location and spatial coverage. To optimally use the RF power available and simultaneously manage the RF deposition in the body, different RF optimization solutions were applied dynamically during an ASL sequence. Preliminary results show that optimization of B1+ for each RF pulse in a sequence and applying those solutions dynamically during imaging acquisition appear to improve ASL perfusion results in the prostate at 7T.