Multislice T1 Relaxation Time Measurements in the Brain Using IR-EPI: Reproducibility, Normal Values, and Histogram Analysis in Patients with Multiple Sclerosis

Purpose: To perform T₁ measurements using inversion recovery (IR) echoplanar imaging (EPI) to evaluate reproducibility, normal values, and T₁ histogram analysis as a measure of disease progression in multiple sclerosis (MS) patients. Materials and Methods: Multislice IR-EPI was performed in 10 controls and 36 MS patients. Region-of-interest (ROI) and T ₁ histogram analysis were performed on T₁ maps and compared to hypointense T₁ lesions and brain atrophy in MS patients. Results: Coefficient of variation (COV) varied from 1.6% to 4.9%. Callosal normal (appearing) white matter (N(A)WM) showed the lowest and cortical gray matter the highest T₁ values. T₁ histogram analysis in controls showed a sharp WM peak centered on a T₁ value of 729 msec (range = 679-765) with extension into a shoulder of higher T₁ values. In MS patients, a shift toward higher T₁ values (mean = 788 msec, range = 700-957) with a lower relative peak amplitude was present, predominantly resulting from T₁ prolongation in NAWM. T₁ histogram parameters strongly related to hypointense T₁ lesion volume and brain atrophy in MS patients. Conclusions: IR-EPI provides a reproducible method to obtain T₁ values in the brain. Regional variation in T₁ values is present in N(A)WM of volunteers and MS patients. Since T₁ histogram parameters reflect changes in NAWM and correlate with conventional measures of disease burden in MS patients, T ₁ histogram analysis may provide a global measure of disease progression in MS.