Introduction:Current standard-of-care tests for atherosclerosis can detect calcification of arteries only at later stages of the disease. Commuted Tomography (CT) calcium score, for example, is only effective once appreciable amounts of plaque have formed. 18F-Sodium Fluoride (NaF) is a radiopharmaceutical with affinity of fluoride to hydroxyapatite. For this reason, it is appealing for bone imaging. Recent studies have shown that NaF could also be used to detect calcified micro-deposits within coronary plaque. The goal of this study was to test if changes in coronary microcalcification over a two year period assessed by NaF PET/CT are associated with baseline subject characteristics.

Methods:This prospective study included healthy female (N = 8, age 52 ± 10 years, BMI 24 ± 1.7 kg/m2) and male (N = 15, age 50 ± 10 years, BMI 27 ± 2.9 kg/m2) participants who had NaF PET/CT scans taken two years apart. Imaging was performed 90 minutes after intravenous injection of 2.2 MBq of NaF per kilogram of body weight. The analysis regions were selected on CT images by drawing volumes of interest around the entire heart using a semi-automatic segmentation method.SUVmean and SUVmax were calculated in the same regions of the registered PET images. Percent change in SUV between the two time points were correlated against baseline age, BMI, cardiovascular risk factors, and blood chemistry.

Results: In males, percent change in SUVmean over the two year period was positively correlated with baseline BMI (r= 0.85, P< 0.0001) and systolic blood pressure (r= 0.65, P= 0.0082). These baseline values were not significantly correlated with SUVmean in females or SUVmax and CT HUmean in either gender.

Discussion:High BMI is a known risk factor for atherosclerosis. Our data showed that rate of increase in coronary microcalcification over time measured by NaF PET/CT is associated with baseline BMI and some clinical risk factors in males. Lack of such associations in females could be due to low sample size (N = 8). Further prospective studies are needed to determine if baseline BMI and clinical factors could be used to predict rate of increase in coronary microcalcification which could provide the basis for managing the progression of atherosclerosis in patient-specific manner.