Q: 45 year old man is in ICU and going for PET scan for unrelated reason. Radiology department ask you to administer IV Lorazepam if feasible before PET scan. What is the reason behind it?


Answer: Brown adipose tissue in the body  can cause increase uptake of fluorodeoxyglucose (FDG) and give false positive results Brown tissue is usually found at the base of the neck, in the supraclavicular region, in the superior mediastinum, and in the upper abdomen. Benzodiazepines decreases the sympathetic tone, and reduces the metabolism of brown fat, and helps in decreasing the likelihood of false positive results of PET scan.


References: 

O'Donnell JS, Rini J, Chusid J, Shah R. Abnormal Uptake on PET/CT: Imitators of Malignancy in Thoracic Imaging. Contemporary Diagnostic Radiology 2011; 34:1.