Abnormally increased uptake of 18F-FDG in the forearm and hand following intra-arterial injection -- hot forearm and hot hand signs.

The aim of this study is to describe the appearance of intra-arterial administration of 18F-fluorodeoxyglucose (18F-FDG). The effect of this finding on the standard uptake values (SUVs) is also briefly discussed. Three cases of 18F-FDG positron emission tomography (PET) scans, detected over 2 years (2004-2006), with different presentations producing hot forearm and hot hand signs are described. It was shown that intra-arterial injections of 18F-FDG producing "the hot forearm sign" and the hot hand sign" are similar to the glove pattern of uptake noted following intra-arterial administration of technetium-99m methylene diphosphonate. Following intra-arterial injection, uptake of 18F-FDG is accentuated by hypoxia and exercise. A comparison is also made with the pattern of soft-tissue uptake seen following true intravenous injections with similar pre-injection vein enhancement techniques to the intra-arterial injections. Evaluation of the maximum intensity projection (MIP) and transaxial PET/CT fusion images of the arm, forearm and hand helps to confirm the diagnosis. Hands are often not included in PET/CT imaging and therefore cases might be missed. In conclusion, intra-arterial injection of 18F-FDG produces a "hot forearm sign" and "hot hand sign". Hands are often not included in PET/CT imaging, and therefore the presence of hot forearm sign should suggest further investigation. It should be mentioned in the radiology report, as it may alter the sensitivity and specificity of the SUV value.