Myelin imaging: past, present, and beyond

In multiple sclerosis (MS) patients, the myelin sheath, which is the protective layer covering nerves, gets damaged. For monitoring of the progression of myelin damage and its repair an accurate direct measurement of myelin density is needed. In this thesis, we show the performances, pitfalls, and practical applications of myelin imaging methods for objectively measuring myelin density. [11C]MeDAS PET scanning is such a method. We demonstrated that [11C]MeDAS PET is a promising method for measuring myelin density as its signal in the brain, spinal cord, and MS lesions corresponded well with the physiological distribution of myelin. Furthermore, with [11C]MeDAS PET a decrease in myelin density within white matter lesions in MS patients over time could be detected. In addition, we used advanced diffusion MRI techniques and showed it enabled MS lesion characterization beyond traditional measures. Advanced analysis of brain networks with diagnostic MRI revealed some deterioration of brain regions involved in motor function. We also found that advanced statistical analyses applied to MRI data could be used to discriminate different MS subtypes.