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 T(1) measurements using inversion recovery (IR) echoplanar imaging (EPI) to evaluate reproducibility, normal values, and T(1) 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 T(1) maps and compared to hypointense T(1) 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 T(1) values. T(1) histogram analysis in controls showed a sharp WM peak centered on a T(1) value of 729 msec (range = 679-765) with extension into a shoulder of higher T(1) values. In MS patients, a shift toward higher T(1) values (mean = 788 msec, range = 700-957) with a lower relative peak amplitude was present, predominantly resulting from T(1) prolongation in NAWM. T(1) histogram parameters strongly related to hypointense T(1) lesion volume and brain atrophy in MS patients.

CONCLUSIONS

IR-EPI provides a reproducible method to obtain T(1) values in the brain. Regional variation in T(1) values is present in N(A)WM of volunteers and MS patients. Since T(1) 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.