Abstract
BACKGROUND: To assess the test-retest reproducibility of cortical mapping of T2 * relaxation rates at 7 Tesla (T) MRI. T2 * maps have been used for studying cortical myelo-architecture patterns in vivo and for characterizing conditions associated with changes in iron and/or myelin concentration. METHODS: T2 * maps were calculated from 7T multi-echo T2 *-weighted images acquired during separate scanning sessions on 8 healthy subjects. The reproducibility of surface-based cortical T2 * mapping was assessed at different depths of the cortex; from pial surface (0% depth) towards gray/white matter boundary (100% depth), across cortical regions and hemispheres, using coefficients of variation (COVs = SD/mean) between each couple (scan-rescan) of average T2 * measurements. RESULTS: Average cortical T2 * was significantly different among 25%, 50%, and 75% depths (analysis of variance, P < 0.001). Coefficient of variations were very low within cortical regions, and whole cortex (average COV = 0.83-1.79%), indicating a high degree of reproducibility in T2 * measures. CONCLUSION: Surface-based mapping of T2 * relaxation rates as a function of cortical depth is reproducible and could prove useful for studying the laminar architecture of the cerebral cortex in vivo, and for investigating physiological and pathological states associated with changes in iron and/or myelin concentration.