• Mohiuddin Hadi, Clara C Chen, Millie Whatley, Karel Pacak, and Jorge A Carrasquillo.
• Department of Nuclear Medicine, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland, USA.
• J. Nucl. Med. 2007 Jul 1; 48 (7): 1077-83.

UnlabelledSeveral radiopharmaceuticals such as (18)F-FDG, (123)I-metaiodobenzylguanidine (MIBG), and (99m)Tc-tetrofosmin have demonstrated uptake in brown adipose tissue (BAT). It is important to recognize these normal variants so that they are not misinterpreted as a significant pathologic state. In addition, these radiopharmaceuticals may shed light on BAT physiology. (18)F-6-fluorodopamine (F-DA) is being used as a PET radiopharmaceutical to image adrenergic innervation and suspected pheochromocytoma. Past reports have suggested that BAT is increased in pheochromocytoma patients.MethodsThe images of 96 patients evaluated with (18)F-F-DA or (18)F-FDG PET/CT for known or suspected pheochromocytoma were reviewed retrospectively to determine whether localized uptake of a pattern typically associated with BAT was present. When available, contemporaneous images obtained using (123)I-MIBG were also reviewed for the presence of BAT.ResultsOf 67 patients imaged with (18)F-F-DA, BAT was found in 17.9%. Of 83 patients imaged with (18)F-FDG, 19.2% had BAT. Discordant findings related to uptake in BAT were often seen in patients studied with (18)F-FDG, (18)F-F-DA, or (123)I-MIBG. Overall, 26 (27.0%) of 96 patients showed BAT on at least 1 of the 3 imaging modalities.Conclusion(18)F-F-DA can image BAT, most likely by localizing to sympathetic innervations in a manner similar to (123)I-MIBG. Patients with pheochromocytoma may have a greater BAT tissue mass or activation because of elevated levels of circulating catecholamines. Quantitative PET with (18)F-FDG and (18)F-F-DA may have a role in in vivo studies of BAT physiology in humans or animal models.

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