The incidence of pulmonary embolism and associated FDG-PET findings on IV contrast enhanced PET/CT

Objectives The majority of FDG PET/CT studies are performed on cancer patients. These patients are at increased risk of pulmonary embolism (PE, Ref 1 & 2). In this retrospective review, we determined the rate of pulmonary embolism, and the prevalence of associated FDG PET findings on IV contract enhanced PET/CT.

Methods We identified all PET/CT studies performed at our institution with a reported finding of PE between January 2005 and October 2012. The medical record was reviewed for symptoms which were identified following the diagnosis of PE, and whether the patients received treatment. The prevalence of associated FDG PET findings was determined.

Results 65 total cases of pulmonary embolism (of 18272 total PET/CT examinations) were identified of which 59 were previously unknown. This gives an incidental pulmonary embolism rate of 0.32%. Of the patients where sufficient clinical information was available, 34/36 (94%) were treated, either with therapeutic anticoagulation or IVC filter, and 30/36 (83%) were asymptomatic in retrospect. Of the patients with incidental PE, we found 9 (15.2%) with associated focal pulmonary artery hypermetabolism, three (5.1%) with hypermetabolic pulmonary infarction, and one with increased isolated right ventricular FDG uptake (1.7%). One case of chronic pulmonary embolism demonstrated a focal hypometabolic filling defect in a pulmonary artery on PET.

Conclusions We found incidental pulmonary embolism in 0.32% of PET/CT scans. Focal pulmonary artery hypermetabolism or hypometabolism, and hypermetabolic pulmonary artery infarction with the “rim sign” were uncommonly associated with PE (Ref 3 & 4). These findings could raise the possibility of incidental PE in non IV-contrast enhanced PET/CT studies.