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Abstract #1287

Improving TOF Angiography Contrast Homogeneity with B1+ Shimming at 7 Tesla: Benefits & Challenges

Sebastian Schmitter1, Edward J. Auerbach1, Gregor Adriany1, Kamil Ugurbil1, Pierre-Francois Van De Moortele1

1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

In Time-of-flight (TOF) angiography a contrast is generated between static tissues, partially saturated due to a high flip angle (&alpha=20-30) with short TR<<T1, and vessels, with strong signal from inflowing blood in the slab. Benefiting from high SNR and long T1, TOF studies at 7T provide good vessel-to-background contrast. However, a significant drawback observed at 7T is the spatially inhomogeneous magnitude of transmit B1 (B1+), resulting in non-uniform TOF contrast. The aim of this work was to investigate the potential and challenges of using B1+ phase shimming to improve the uniformity of TOF contrast in the brain at 7T.