Increased PET 11C-PBR28 binding in multiple sclerosis normal-appearing white matter correlates with MRI measures of myelin loss

INTRODUCTION: C-PBR28 binds to the Translocator Protein (TSPO), a marker of activated microglia. Advanced Magnetic Resonance (MR) techniques are sensitive to different tissue properties such as myelin (myelin water fraction, MWF; magnetisation transfer ratio, MTR; radial diffusivity, RD; choline, tCho), axons (axial diffusivity, AD; n-acetylaspartate, tNAA) and gliosis (myo-inositol, mI). OBJECTIVE: C-PBR28 binding and advanced MR measures in normal-appearing white matter (NAWM) and lesions. METHODS: ). Advanced 3T MR included myelin water imaging, diffusion tensor imaging and spectroscopy. Mean measurements were extracted from lesion and NAWM masks. RESULTS: and MWF (R=-0.71, p = 0.001) and MTR (R=-0.68, p = 0.003). CONCLUSIONS: C-PBR28 binding in NAWM are associated with demyelination (decreased MWF and MTR), especially in PMS. The ability to measure and monitor diffuse inflammation could help evaluate therapies designed to target whole brain immune activity and more specifically microglia.