Regional cerebral relaxation times measured by magnetic resonance imaging at 3.0 Tesla

Abstract

Brain tissue T₁ and T₂ relaxation times were measured at 3.0 T from a total of 8 (M/F = 5/3) healthy volunteers, selecting 9 regions of interest (ROIs) in the prefrontal, frontal, parietal, occipitoparietal and hippocampal regions. Apart from the prefrontal region, the other four ROIs were selected within the left and right brain hemispheres. The selected ROIs contained either grey matter (GM) or white matter (WM) or both. The T₁ measurements were done using the saturation recovery imaging method at 8 different repetition times (TRs) whereas the T₂ measurements were carried out using the multiple spin-echo imaging method at 12 different echo times (TEs). The average T₁ values (mean ± SE, ms) from 4 (M/F = 2/2) volunteers were: 1942 ± 29 (prefrontal GM), 1203 ± 40 (frontal WM), 1217 ± 21 (parietal WM), 1425 ± 29 (occipitoparietal GM/WM), and 1435 ± 62 (hippocampi). The average T₂ estimates (mean ± SE, ms) from another group of 4 (M/F = 3/1) volunteers were: 147 ± 9 (prefrontal GM), 121 ± 3 (frontal WM), 131 ± 4 (parietal WM), 127 ± 1 (occipitoparietal GM/WM), and 142 ± 8 (hippocampi). Neither T₁ nor T₂ relaxation times differed significantly between the two brain hemispheres by paired t-tests (p > 0.05). However, regional T₁ was found to vary significantly (p < 0.01) while regional T₂ did not vary significantly (p = 0.07) by one-way ANOVA. These findings are consistent with theory and published data for the ROIs studied. The results could thus serve as a reference data set for brain MRI pulse sequence optimisation at 3.0 T and could as well be useful in multicentre data set comparisons aimed at developing a database of in vivo brain relaxation times.

Keywords: MRI, brain, saturation recovery, spin echo, relaxation time