The effects of bone erosion from aortic aneurysm on the regional uptake of FDG

A 71-year-old white man with a known right-sided apical nonsmall cell lung carcinoma was referred for a F-18 FDG whole body PET-CT examination after chemotherapy before radiotherapy. A staging CT scan had revealed an asymptomatic fusiform 65 mm in diameter nondissecting aneurysm of the thoracic aorta just below the carina. An abnormal crescent-shaped uptake was identified at the margin between the aneurysm and the adjacent thoracic vertebral bodies. At this site a correspondingly shaped bone erosion on CT was proof of the chronic effects of the aneurysm. There were no signs of regional inflammation or malignancy. The FDG uptake was interpreted as evidence of ongoing nonmalignant bone remodeling secondary to the pulsating pressure of the aneurysm. This case demonstrates a potential pitfall in the interpretation of bone associated foci using FDG PET, and once again underlines the importance of correlated anatomic imaging for appropriate clinical management.