Brown adipose tissue: Evaluation with ²⁰¹Tl and ^99mTc-sestamibi dual-tracer SPECT

Brown adipose tissue is one kind of adipose tissue and regulates body temperature and balance of energy via non-shivering thermogenesis. The authors present a case that strongly suggested the presence of activated brown adipose tissue in the neck, shoulders and axillary space by increased ¹⁸F-FDG uptake. ^99mTc-sestamibi and ²⁰¹Tl dual-tracer SPECT study showed increased ^99mTc-sestamibi uptake and non-increased ²⁰¹Tl uptake in the corresponding ¹⁸F-FDG uptake sites. Brown adipose tissue has dense mitochondria in the cells, which play an important role in thermogenesis. ^99mTc-sestamibi uptake and retention depend on the mitochondrial activity but ²⁰¹Tl uptake does not. Therefore, the activity of mitochondria in activated brown adipose tissue may explain the discrepant uptake between ^99mTc-sestamibi and ²⁰¹Tl.