Activated microglia indicated by PET-[11C]PBR28 binding in multiple sclerosis correlates with MRI measures of inflammation and demyelination

Motivation: [11C]PBR28-PET can detect translocator protein, a marker for activated microglia. Advanced MR techniques are sensitive to different tissue properties such as myelin, axons and gliosis. Goal(s): The goals of our study were to compare the binding of [11C]PBR28 in lesions and NAWM in different MS subtypes and to determine the correlation between [11C]PBR28 binding and advanced MRI metrics in NAWM. Approach: Thirteen people living with MS and 5 controls were scanned with [11C]PBR28-PET and advanced 3T MRI. Results: NAWM [11C]PBR28 differed significantly between MS and controls. Correlations were found between 11C]PBR28 binding and MR measures of myelin and gliosis. Impact: Increased inflammation and gliosis may be driving demyelination, especially in progressive forms of multiple sclerosis. The ability to measure diffuse inflammation using PET-[11C]PBR28 and MRI could allow monitoring of therapies designed to target immune activity within the whole brain.