UTE-Based DW-SSFP MRI for 7T

Motivation: At 7T the conventional spin-echo EPI diffusion sequence suffers from the B1+ inhomogeneity and geometric distortion due to refocusing RF pulses and EPI readout. Goal(s): To develop a diffusion imaging sequence without refocusing RF pulses and EPI readout at 7T. Approach: Develop a 3-dimensional DW-SSFP sequence with a spiral readout to reduce the geometric distortion, to maximize the diffusion gradient time, and to reduce susceptibility effect. Results: The proposed DW-SSFP sequence was successful in reducing the B1+ inhomogeneity, the geometric distortion, and the susceptibility effect compared to the spin-echo EPI diffusion sequence using cadaveric head specimens at 7T. Impact: This sequence enables the acquisition of high-resolution diffusion images that do not suffer from the B1+ inhomogeneity and geometric distortion often observed at 7T. It provides good quality fiber tracts and fractional anisotropy maps of the brain.