The role of edema and demyelination in chronic T1 black holes:: A quantitative magnetization transfer study

Purpose: To use quantitative magnetization transfer imaging (qMTI) in an investigation of T-1-weighted hypointensity observed in clinical magnetic resonance imaging (MRI) scans of multiple sclerosis (MS) patients, which has previously been proposed as a more specific indicator of tissue damage than the more commonly detected T-2 hyperintensity. Materials and Methods: A cross-sectional study of 10 MS patients was performed using qMTI. A total of 60 MTI measurements were collected in each patient at a resolution of 2 x 2 x 7 mm. over a range of saturation pulses. The observed T-1 and T-2 were also measured. qMT model parameters were estimated using a voxel-by-voxel fit. Results: A total of 65 T-2-hyper-intense lesions were identified; 53 were also T-1 hypointense. In these black holes, the qMTI-derived semisolid pool fraction F correlated negatively with T-1,T-obs (r(2) = 0. 76; P < 0.0001). The water pool absolute size (PDf) showed a weaker correlation with T-1.obs (positive. r(2) = 0.53: P < 0.0001). The magnetization transfer ratio (MTR) showed a similarly strong correlation with F and a weaker correlation with PDf (r(2) = 0. 18: P < 0.04). Conclusion: T-1 increases in chronic black holes strongly correlated with the decline in semisolid pool size, and somewhat less to the confounding effect of edema. MTR was less sensitive than T-1.obs to liquid pool changes associated with edema.