TSPO and relapsing-remitting multiple sclerosis: To explore whether BRL could serve as an in vivo biomarker for MS progression, we analyzed a TSPO PET MS cohort (n = 114; 32 (28%) males, 82 (72%) females; 31 (27%) with secondary progressive multiple sclerosis (SPMS) and 83 (73%) RRMS patients; Fig. 1).