T2* Relaxation Time Measurements of Various Brain Regions at 0.5 T

Motivation: Accurate knowledge of T2* relaxation times is important for optimizing contrast and SNR in multi-echo gradient echo sequences. Goal(s): To measure the nominal T2* relaxation parameter at 0.5 T over subregions in the brain. Approach: A 2 mm isotropic 3D multi-echo GRE sequence was acquired in 5 healthy volunteers. T2* estimates were computed over regions of interest using a mono-exponential fit. Results: T2* estimates of gray (86±8 ms) and white (78±5 ms) matter are in good agreement with previously published measurements in the mid-field. In the deep brain, average T2* values ranged between 70±2 ms to 89±5 ms. Impact: For optimal T2* contrast in the brain at 0.5 T, echoes from multi-echo acquisitions should extend beyond 60 ms. For optimal SNR, echoes should be combined with a target T2* of ~80 ms.