TSPO and myeloid sarcoma: Pitombeira et al., using PET/MR and two radiolabels: [11C]-PIB and the marker of innate immune cell activation-(R)-[11C]PK11195 (TSPO) in opposition to previous studies, found no significant difference in the distribution volume (VT) of (R)-[11C]PK11195 in any of the VOIs (Volume of Interest) tested between the MS patient group and the healthy subject group [36].