Pseudoreference Regions for Glial Imaging with 11C-PBR28: Investigation in 2 Clinical Cohorts

The translocator protein (TSPO) is a commonly used imaging target to investigate neuroinflammation. Although TSPO imaging demonstrates great promise, its signal exhibits substantial interindividual variability, which needs to be accounted for to uncover group effects that are truly reflective of neuroimmune activation. Recent evidence suggests that relative metrics computed using pseudoreference approaches can minimize within-group variability and increase sensitivity to detect physiologically meaningful group differences. Here, we evaluated various ratio approaches for TSPO imaging and compared them with standard kinetic modeling techniques, analyzing 2 different disease cohorts. Patients with chronic low back pain (cLBP) or amyotrophic lateral sclerosis (ALS) and matching healthy controls received 11C-PBR28 PET scans. The occipital cortex, cerebellum and whole brain were first evaluated as candidate pseudoreference regions by testing for the absence of group differences in SUV and distribution volume (VT) estimated with an arterial input function. The SUV from target regions (cLBP study, thalamus; ALS study, precentral gyrus) was normalized with the SUV from candidate pseudoreference regions (i.e., occipital cortex, cerebellum, and whole brain) to obtain SUVRoccip, SUVRcereb, and SUVRWB. The sensitivity to detect group differences in target regions was compared using various SUVR approaches, as well as distribution volume ratio (DVR) estimated with (blDVR) or without arteri...

Source: Journal of Nuclear Medicine - January 2, 2018 Category: Nuclear Medicine Authors: Albrecht, D. S., Normandin, M. D., Shcherbinin, S., Wooten, D. W., Schwarz, A. J., Zurcher, N. R., Barth, V. N., Guehl, N. J., Akeju, O., Atassi, N., Veronese, M., Turkheimer, F., Hooker, J. M., Loggia, M. L. Tags: Clinical Source Type: research