Superiority of 3D-DIR over 3D-FLAIR in the Detection of Cortical Lesions and Correlation with Disability in Multiple Sclerosis: A Multicenter Study

<b>Background/Objectives</b>: The aim of the study was to compare diagnostic performance of 3D-Double Inversion Recovery (DIR) and 3D-Fluid-Attenuated Inversion Recovery (FLAIR) sequences in the detection of brain lesions in Multiple Sclerosis (MS) patients, especially cortical ones, and to evaluate potential correlation between lesion number and clinical outcome. <b>Methods</b>: From April 2021 to July 2024, 278 MS patients (201 females, 77 males, mean age 47.01 ± 12.668 years) underwent brain MRI in three Italian Institutions using 1.5 T systems; 3D-FLAIR and 3D-DIR sequences were obtained with an identical anatomic position. Clinical disability was evaluated by the expanded disability state score (EDSS). Data analysis was performed using the Wilcoxon test for lesion count differences (primary endpoint), and Chi-square test and Spearman for EDSS correlation (secondary endpoint); a <i>p</i> < 0.05 was considered as statistically significant. <b>Results</b>: A significantly higher total number of lesions was displayed on DIR images (<i>n</i> = 6601) compared with FLAIR (<i>n</i> = 6484) (<i>p</i> < 0.001). The mean number of cortical lesions identified with DIR (1.56 ± 2.767) was significantly higher than the mean number of cortical lesions detected with FLAIR (0.52 ± 1.029) (<i>p</i> < 0.001). Conversely, FLAIR sequences detected a significantly higher mean number of subcortical lesions (9.34 ± 8.663) compared to DIR (8.94 ± 8.415) (<i>p</i> < 0.001). A significant correlation was found between EDSS and the number of juxtacortical and cortical lesions detected with DIR with a <i>p</i> < 0.001. <b>Conclusions</b>: 3D-DIR is superior to 3D-FLAIR in detecting cortical lesions, which are correlated to clinical disability, and it should be implemented for the diagnosis and prognostic evaluation in MS patients.