Abstract
1439
Objectives: Rheumatoid arthritis (RA) is associated with increased rate of atherosclerosis.18F-sodium fluoride (NaF) has been known to detect active calcification in the early stages of atherosclerotic plaques. Furthermore, over the past decade, FDG-PET has been used as a molecular probe to detect inflammation in atherosclerotic plaques. Our goal was to determine whether NaF-FDG-PET imaging can detect active abdominal aortic calcification or inflammation in the abdominal aorta of RA patients.
Methods: In this study, 15 RA patients (4 women, 11 men; mean age 53.8±10.8 y, range 25-64) and 15 healthy controls (4 women, 11 men; mean age 53.6 ±11.3 y, range 25-64) were included. The controls were matched to patients by sex and age (±4 years). All subjects underwent NaF-PET/CT scanning 90 minutes after the administration of NaF. FDG-PET/CT imaging was performed 180 minutes after the injection of FDG. Using OsiriX software, regions of interest (ROI) were manually drawn around the abdominal aorta wall in its entirety (starting with the upper pole of the left kidney, ending with the last slice before the aortic bifurcation). The global mean standardized uptake value (global SUVmean) was then calculated. Blood pool activity of both NaF and FDG was determined by drawing two ROIs in the lumen of superior vena cava and calculating the average. Target-to-background ratios (TBR) were calculated by dividing the global NaF or FDG SUVmean in the aortic wall by the mean tracer activity in the blood pool. A non-parametric test (Mann-Whitney U test) was used to assess the difference in the mean values generated in the population examined.
Results: The NaF TBRmean of RA patients ranged from 1.25 to 2.15, and from 1.03 to 1.78 in healthy controls. Moreover, average NaF TBRmean scores among RA patients was significantly greater than that of healthy controls (1.63±0.24 and 1.41±0.19, respectively, P=0.01). The FDG TBRmean of RA patients ranged from 0.88 to 1.88, and from 1.09 to 1.89 in healthy controls. There was no significant difference between the average FDG TBRmean scores in the RA patients when compared to healthy controls (1.35±0.28 and 1.37±0.22, respectively, P>0.05).
Conclusions: Our findings indicate that global assessment with NaF-PET/CT is a powerful imaging technique in detecting and quantifying molecular calcification in the abdominal aorta. FDG TBRmean did not show a significant difference between the two groups indicating the low sensitivity of FDG PET in detecting and characterizing atherosclerotic plaques. Further studies are needed to confirm the potential role of NaF to diagnose, monitor and assess the treatment response in patients at high risk for atherosclerosis.