PET Imaging of Human Brown Adipose Tissue with the TSPO Tracer [

PURPOSE: Brown adipose tissue (BAT) in adult humans has been recently rediscovered and intensively investigated as a new potential therapeutic target for obesity and type 2 diabetes (T2D). However, reliable assessment of BAT mass in vivo represents a considerable challenge. The purpose of this investigation is to demonstrate for the first time that human BAT depots can be imaged with a translocator protein (TSPO)-specific positron emission tomography (PET) tracer [(11)C]PBR28 under thermoneutral conditions. PROCEDURES: In this retrospective analysis, we analyzed the images of three healthy volunteers who underwent PET/magnetic resonance (MR) imaging after injection of 14 m Ci of [(11)C]PBR28 at room temperature. Thirty-minute static PET images were reconstructed from the data obtained 60–90 min after the injection of the tracer. RESULTS: [(11)C]PBR28 uptake in the neck/supraclavicular regions was identified, which was parallel to the known distribution pattern of human BAT depots. These areas co-localized with the areas of hyperintensity and corresponded to fat on T1-weighted MR images. Standardized uptake value (SUV) was used to quantify [(11)C]PBR28 signal in BAT depots. The average (± SD) SUV((mean)) and SUV(max) for BAT depots was 2.13 (± 0.33) and 3.19 (± 0.34), respectively, while the average SUV((mean)) for muscle and subcutaneous adipose tissue was 0.79 (± 0.1) and 0.18 (± 0.04), respectively. CONCLUSIONS: In this brief article, we provide the first evidence suggesting that [(11)C]PBR28, a widely available TSPO-specific PET tracer, can be used for imaging human BAT mass under thermoneutral conditions.