Imaging cortical lesions in multiple sclerosis with ultra-high-field magnetic resonance imaging

Objective: To determine the sensitivity of T2*-weighted gradient-echo (T2*GRE) and inversion recovery turbo-field-echo (TFE) sequences for cortical multiple sclerosis lesions at 7 T. Design, Setting, and Participants: Autopsied brain tissue from individuals with multiple sclerosis was scanned with 3-dimensional T2*GRE and 3-dimensional inversion recovery white matter-attenuated TFE sequences at 7 T. Cortical lesions visible with either sequence were scored for each anatomical lesion type. Imaged brain tissue was then processed for immunohistochemical analysis, and cortical lesions were identified by labeling with antibody against myelin basic protein and CD68 for microglia. Magnetic resonance images were matched with corresponding histological sections and scored retrospectively to determine the sensitivity for each cortical lesion type. Main Outcome Measure: Cortical lesion detection by 3-dimensional T2*GRE and white matter-attenuated TFE sequences. Results: The 3-dimensional T2*GRE and white matter-attenuated TFE sequences retrospectively detected 93% and 82% of all cortical lesions, respectively (with varying sensitivities for different lesion types). Lesion visibility was primarily determined by size as all undetected lesions were smaller than 1.1 mm at their smallest diameter. The T2*GRE images showed hypointense rings in some cortical lesions that corresponded with increased density of activated microglia. Conclusions: Three-dimensional T2*GREand white matter-attenuated TFE sequences at a 7-T field strength detect most cortical lesions in postmortem multiple sclerosis tissue. This study indicates the potential of T2*GRE and white matter-attenuated TFE sequences in ultra-high-field magnetic resonance imaging for cortical lesion detection in patients with multiple sclerosis.