Multimodal MRI Changes in Cortical Grey Matter Following Formalin Fixation

Klaus Schmierer¹, Janet R. Thavarajah¹, Harold G. Parkes¹, David H. Miller¹, Daniel J. Tozer¹

Post mortem multiple sclerosis (MS) brain is being used to establish the pathological correlates of changes detected using MRI. Fixation of brain tissue introduces a potential confounder that may affect the inference of in vivo changes from MR/histology studies. This study investigated changes following fixation of quantitative MR indices in MS cortical grey matter (CGM). Fixation results in a substantial drop of T1, less so of magnetization transfer ratio, and an increase of macromolecular proton fraction in post mortem MS CGM. These changes are likely due to (i) direct formaldehyde effects and (ii) intra- and intermolecular cross-linking of macromolecules.