Abstract 1916: Atherosclerosis Inflammation Imaging With FDG-PET/CT is Highly Reproducibile in Carotid, Iliac and Femoral Arteries
Introduction: FDG PET can be used to quantify inflammation within atherosclerotic plaque, and can differentiate symptomatic from asymptomatic lesions. What is unknown are the inter- and intra-observer agreement of the technique and the short-term variability of the arterial FDG signal (inter-scan reproducibility). This information is crucial before FDG PET can be used as a surrogate marker of anti-atherosclerosis drug efficacy. We hypothesized that intraclass correlation coefficient values would be >0.80.
Methods: 19 asymptomatic patients with known vascular disease underwent carotid and iliac artery PET/CT imaging on a GE Discovery LS scanner. Femoral artery images were also acquired in 12 of the patients. Images were obtained 90 minutes after 10mCi FDG. To estimate FDG uptake into vessel, standardized uptake values (SUV) were calculated using ROI applied to the PET/CT images and corrected for blood FDG activity. To estimate interscan reproducibility, scans were repeated after 14 days. To assess inter- and intra-observer agreement, the first scan was read independently by 2 readers, and on two separate occasions by reader 1.
Results: Mean age was 65 years with 5 diabetics. The mean (standard deviation) SUV values were: iliac artery 1.25 (0.18), femoral artery 1.22 (0.17), carotid artery 1.64 (0.21). All territories showed excellent reproducibility (Table⇓), with the carotid artery performing best on all three measures.
Conclusions: FDG PET is a highly reproducible technique for atherosclerosis imaging, comparing well with ultrasound, CT and MRI. There is low short term variation in plaque FDG signal over 14 days. In addition, SUV standard deviation values are low relative to the mean. These results mean that PET is a powerful technique to detect small changes in plaque inflammation and that drug trials will require relatively small patient numbers to show efficacy. We suggest the carotid arteries are the most reproducible territories to choose for future trials.