Increased spatial resolution using a three-dimensional T1-weighted gradient-echo MR sequence results in greater hypointense lesion volumes in multiple sclerosis

PURPOSE: Our goal was to evaluate whether improved spatial resolution of MR images results in the detection of higher volumes of hypointense lesions in patients with multiple sclerosis (MS). METHODS: A magnetization-prepared rapid acquisition gradient-echo (MP-RAGE) sequence with subsequent reconstruction of axial sections with 5-, 3-, and 1-mm thickness and a dual-echo sequence were obtained in 16 patients with relapsing-remitting or secondary-progressive MS. The volumes of MR imaging abnormalities present on each of these studies were measured using a semiautomated segmentation technique based on local thresholding. The hypointense lesion volumes seen on the three reconstructed MP-RAGE sets of images were compared using the Friedman test and correlated with the hyperintense lesion volume on proton density-weighted images and with scores on the Expanded Disability Status Scale using Spearman's rank correlation coefficient. RESULTS: The median volume of hypointense lesions increased from 1.2 mL (range, 0 to 14.9 mL) on the 5-mm-thick MP-RAGE images to 1.7 mL (range, 0 to 15.8 mL) on the 3-mm-thick images, and to 1.9 mL (range, 0 to 16.2 mL) on the 1-mm-thick images. The hypointense lesion volumes measured on the three MP-RAGE images correlated significantly with the degree of disability, whereas this correlation was not significant with the T2- weighted lesion load. CONCLUSION: Our findings indicate that a significant increase in the volume of potentially disabling MS lesions is observed when obtaining MR images with thin sections.