Incidental diagnosis of thrombus within an aneurysm on 18F-FDG PET/CT: frequency in 926 patients.

Our objective was to evaluate the incidence of aneurysm and the frequency of thrombus within an aneurysm on unenhanced 18 F-FDG PET/CT studies. Methods: We reviewed 1,540 PET/ CT scans from 926 patients. A log recorded whether each case of aneurysm had a suspected thrombus. The maximal standardized uptake value of the patent vessel was compared with the thrombus. Findings were confirmed using all available follow-up data. Results: Aneurysm was found incidentally in 16 (1.7%) of the 926 patients, with 15 occurring in the abdominal aorta and 1 in the internal jugular vein. Seven of these 16 patients had shown suggestions of thrombus on unenhanced PET/CT, and in all 7, thrombi were confirmed on contrastenhanced CT. Conclusion: In 1.7% of patients, aneurysm was found incidentally on PET/CT, and thrombus was present in 44% of these cases.