Comparison of postmortem in situ 3T MRI and ex vivo ultra-high-resolution 7T MRI in multiple sclerosis cortical lesions

Motivation: Cortical lesions in multiple sclerosis are clinically relevant but cannot be detected reliably using conventional MRI. Ex vivo ultra-high-resolution MRI is reliable in cortical lesion detection. Goal(s): Identify cortical lesions on ex vivo 7T MRI in comparison to postmortem in situ conventional 3T MRI. Approach: Retrospective visual assessment of cortical lesions on conventional MRI. Results: 3T T1-weighted MPRAGE showed the highest sensitivity (66%), followed by T2-weighted SPACE (52%), and 3D FLAIR (48%) for detection of cortical lesions. Purely cortical lesions were less visible on in situ MRIs. Some leukocortical lesions appeared juxtacortical white matter lesions on conventional MRI. Impact: Ultra-high-resolution MRI provides a platform to investigate substrates of cortical pathology in multiple sclerosis by bridging the gap between macroscopic conventional MRI and pathology.