MS cortical lesions on double inversion recovery MRI

Abstract

Double inversion recovery (DIR) MRI is a relatively novel imaging technique in which both white matter (WM) and CSF signals are suppressed; cortical lesions are thereby identified as focal areas of hyperintensity relative to surrounding gray matter (GM).1 Three dimensional DIR increases intracortical lesion detection by 500% compared to lesion identification on T2-weighted spin-echo, and by more than 150% when compared to 3D fluid-attenuated inversion recovery (FLAIR).1 Despite these improvements, DIR-detected lesions are fewer than expected based on postmortem studies2: less than 7 (on average) per patient in relapsing-remitting (RR), primary progressive (PP), and secondary progressive (SP) multiple sclerosis (MS).3,–,5 This low rate of detection could be due to technical factors, such as low signal-to-noise ratio, poor definition of lesion boundaries, and the high likelihood of artifacts (e.g., flow, signal intensity differences between slabs, and vessel hyperintensities). It is not easy to see cortical lesions on DIR images, and even when following the conservative international recommendations on lesion scoring (subpial lesions are excluded), experts reached complete agreement in only 19% of the lesions scored.6 Why have these challenges and limitations not discouraged the use of DIR in clinical studies? The short answer is that there is a …