Infradiaphragmatic Brown Fat Uptake

Brown fat uptake in FDG-PET is usually fairly characteristic in the neck, shoulder and costovertebral regions: bilateral, symmetric, intense uptake that is usually multifocal although linear uptake is also possible.

Infradiaphragmatic brown fat uptake poses a challenge when asymmetrical or focal, and may be mistaken for adrenal malignancy or misregistration due to respiration. Correlation with PET images shows the uptake to be located in infradiaphragmatic fat.

References

• Bar-Shalom R, Gaitini D, Keidar Z, Israel O. Non-malignant FDG uptake in infradiaphragmatic adipose tissue: a new site of physiological tracer biodistribution characterised by PET/CT. Eur J Nucl Med Mol Imaging. 2004 Aug;31(8):1105-13.
• Reddy MP, Ramaswamy MR. FDG uptake in brown adipose tissue mimicking an adrenal metastasis: source of false-positive interpretation. Clin Nucl Med. 2005 Apr;30(4):257-8.