Brown fat imaging with (18)F-6-fluorodopamine PET/CT, (18)F-FDG PET/CT, and (123)I-MIBG SPECT: a study of patients being evaluated for pheochromocytoma.
Several 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.


METHODS
The 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.


RESULTS
Of 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.


CONCLUSIONS
(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.
Hadi
Mohiuddin
M
Department of Nuclear Medicine, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland, USA.
Chen
Clara C
CC
Whatley
Millie
M
Pacak
Karel
K
Carrasquillo
Jorge A
JA
D019797:3-Iodobenzylguanidine; D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000294:innervation; D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004298:Dopamine / Q000031:analogs & derivatives*; D004837:Epinephrine / Q000097:blood; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010673:Pheochromocytoma / Q000175:diagnosis / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D013564:Sympathetic Nervous System / Q000000981:diagnostic imaging; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
D005462:Fluorine Radioisotopes; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D019797:3-Iodobenzylguanidine; C029253:6-fluorodopamine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine