Benzodiazepine-resistant "brown fat" pattern in positron emission tomography: Two case reports of resolution with temperature control

PURPOSE: Supraclavicular uptake of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) on positron emission tomography (PET) scan is attributed to lymph node, muscle, or brown fat activity. Differentiation between physiological or pathological etiologies is necessary. Benzodiazepine premedication to reduce physiological uptake has been attempted with variable success. A relationship between brown-fat FDG uptake and cold temperature has also been established. To our knowledge, no case reports or studies have been published to demonstrate whether controlling the temperature can alter the physiological uptake in these regions. PROCEDURES: Two teenage female patients with these patterns on PET scans performed with oral benzodiazepine administration underwent repeat imaging with temperature-controlled environment settings. RESULTS: Resolution of supraclavicular FDG uptake with temperature control in two patients in whom benzodiazepine had no prior effect. CONCLUSION: Although the exact mechanism remains unknown, we propose that the control of temperature reduces the metabolism of glucose by brown fat. Further studies are warranted to confirm the above observations, and, if confirmed, to determine the most efficient and effective use of temperature control to minimize supraclavicular and axillary FDG uptake. (C) 2004 Elsevier Inc. All rights reserved.