In vivo measurements of irreversible and reversible transverse relaxation rates in human basal ganglia at 7 T: making inferences about the microscopic and mesoscopic structure of iron and calcification deposits

Abstract

The goal of this study was to measure irreversible and reversible transverse relaxation rates in the globus pallidus and putamen at 7 T, and to use these rates to make inferences about the sub‐voxel structure of iron and calcification deposits. Gradient Echo Sampling of a Spin Echo (GESSE) data were acquired at 7 T on eighteen volunteers spanning a large range of ages (23–85 years), with calcifications in the globus pallidus incidentally observed in one volunteer. Maps of transverse relaxation rates were derived from the GESSE data, and the mean value of these rates in globus pallidus and putamen was estimated for each volunteer. Both irreversible and reversible transverse relaxation rates increased with the expected age‐dependent iron content in these structures, except for the individual with calcifications for whom extremely large reversible relaxation rates but normal irreversible relaxation rates were found in the globus pallidus. Given the sensitivity of irreversible and reversible transverse relaxation rates to microscopic and mesoscopic field variations, respectively, our findings suggest that joint consideration of these rates may yield information not only about the amount of iron and calcification deposited in the brain, but also about the sub‐voxel structure of these deposits, perhaps revealing certain aspects of their geometry and cellular distribution.

Simultaneous T2 and mapping of multiple sclerosis lesions with radial RARE‐EPI

“…Given the characteristic MRI features of MS lesions, it is conceptually appealing to pursue techniques that support simultaneous generation of quantitative maps of multiple MR contrasts. 32,[49][50][51][52][53][54][55][56][57][58][59][60] Dual contrast techniques offer substantial scan time reduction, eliminate the risk for slice misregistration, improve the immunity to bulk motion, and boost clinical use. The current study presents a modular rapid acquisition with relaxation enhancement (RARE)-EPI hybrid, which is a combined acquisition technique variant.…”