T₁/T₂ ratio from 3T MRI improves multiple sclerosis cortical lesion contrast

Background and PurposeCortical demyelinated lesions are prevalent in multiple sclerosis (MS), associated with disability, and have recently been incorporated into MS diagnostic criteria. Presently, advanced and ultrahigh-field MRIs-not routinely available in clinical practice-are the most sensitive methods for detection of cortical lesions. Approaches utilizing MRI sequences obtainable in routine clinical practice remain an unmet need. We plan to assess the sensitivity of the ratio of T-1-weighted and T-2-weighted (T-1/T-2) signal intensity for focal cortical lesions in comparison to other high-field imaging methods. Methods3-Tesla and 7-Tesla MRI collected from 10 adults with MS were included in the study. T-1/T-2 images were calculated by dividing 3T T-1-weighted (T(1)w) images by 3T T-2-weighted (T(2)w) fluid-attenuated inversion recovery images for each participant. A total of 614 cortical lesions were identified using 7T T-2*w and T(1)w images and corresponding voxels were assessed on registered 3T images. Signal intensities were compared across 3T imaging sequences, including T-1/T-2, T(1)w, T(2)w, and inversion recovery susceptibility-weighted imaging with enhanced T-2 weighting (IR-SWIET) images. ResultsT(1)/T-2 images demonstrated a larger contrast between median lesional and nonlesional cortical signal intensity (median ratio = 1.29, range: 1.19-1.38) when compared to T(1)w (1.01, 0.97-1.10, p < .002), T(2)w (1.17, 1.07-1.26, p < .002), and IR-SWIET (1.21, 1.01-1.29, p < .03). ConclusionT(1)/T-2 images are sensitive to cortical lesions. Approaches incorporating T-1/T-2 could improve the accessibility of cortical lesion detection in research settings and clinical practice.