Detecting multiple sclerosis cortical lesions post-mortem using 7 Tesla Magnetic Resonance Imaging

Introduction: Although originally considered a white matter (WM) disease, it is now clear that focal cortical grey matter (GM) pathology is an important component of multiple sclerosis (MS). Presently available magnetic resonance imaging (MRI) techniques fail in detecting the actual amount of cortical lesions (CLs). The reason for such a failure is twofold: (i) the small size of CLs relative to image resolution and (ii) the low contrast between CLs and the surrounding healthy or seemingly normal GM tissue. MRI at ultra-high field strengths such as 7 Tesla (T) has the potential to superbly enhance MS-induced CLs visibility. First, ultra-high filed MRI yields images at highest resolution. Second, a greatly enhanced T2 contrast is offered by scanning at 7 T. Moreover, the R2 (1/T2) maps are sensitive to the local susceptibility shifts induced by different tissue contents, such as iron and myelin lipid [1,2]. Fueled by this motivation we here apply ultra-high resolution R2 maps to detect and evaluate CLs and their subtypes post-mortem.