Focal cortical lesion detection in multiple sclerosis: 3 tesla DIR versus 7 tesla FLASH-T2*

Purpose: To evaluate the inter-rater agreement of cortical lesion detection using 7 Tesla (T) FLASH-T2* and 3T DIR sequences. Materials and Methods: Twenty-six patients with multiple sclerosis were scanned on a human 7T (Siemens) and 3T MRI (TIM Trio, Siemens) to acquire 3T DIR/MEMPR and 7T FLASH-T2* sequences. Four independent reviewers scored and categorized cortical lesions in the bilateral precentral gyri (motor strips) as leukocortical, intracortical, or subpial. Inter-rater agreement was assessed according to lesion category using the kappa statistic. The sensitivity of recent MAGNIMS consensus guidelines for cortical lesion detection using 3T DIR was assessed with 7T FLASH-T2* as the reference gold standard. Results: Inter-rater agreement at 7T was excellent compared with 3T (k 0.97 versus 0.12). FLASH-T2* at 7T detected subpial lesions while 3T DIR did not. The predicted sensitivity of 3T DIR sequence for cortical lesions in vivo is modest (range of 13.6 to 18.3%). Conclusion: The 7T FLASH-T2* detects more corticalparticularly subpial-lesions compared with 3T DIR. In the absence of DIR/postmortem data, 7T FLASH-T2* is a suitable gold-standard instrument and should be incorporated into future consensus guidelines.