In the absence of arterial input function from the present design, quantification of TSPO-specific PET-CT data from patients with Huntington’s disease and marked atrophy required extra steps.40,41 By reviewing former research work on PBR28, TSPO expression and Huntington’s disease pathology, we decided to use the CC as the reference region after exploring several brain regions, including the cerebellum.29 The gene discussed is TSPO; the disease is Atrophy.