Visualization of brown adipose tissue with 99mTc-methoxyisobutylisonitrile on SPECT/CT.

UNLABELLED Brown adipose tissue (BAT) is retained into adulthood in some patients. It has been imaged using several radiopharmaceuticals, including (18)F-FDG. Using SPECT/CT, we assessed whether and how frequently uptake of (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) was present in expected locations of BAT. METHODS A total of 205 SPECT/CT scans using (99m)Tc-MIBI for parathyroid imaging were reviewed for the presence of (99m)Tc-MIBI uptake in expected locations of BAT. RESULTS We detected (99m)Tc-MIBI uptake in BAT in 13 of 205 patients (6.3%). When BAT was visualized, it was detected on both early and delayed scans. The patients with (99m)Tc-MIBI uptake in BAT were younger than the patients with no (99m)Tc-MIBI uptake (P=0.044). CONCLUSION Uptake of (99m)Tc-MIBI in BAT is relatively common in this adult patient population and should not be confused with (99m)Tc-MIBI-avid-tumors. SPECT/CT can be useful for defining such tracer uptake as a normal physiologic variant.