Divergent determinants of 18F–NaF uptake and visible calcium deposition in large arteries: relationship with Framingham risk score

To compare regional vascular distribution and biological determinants of visible calcium load, as assessed by computed tomography, as well as of molecular calcium deposition as assessed by 18F–NaF positron emission tomography. Eighty oncologic patients undergoing 18F–NaF PET/CT scan were included in the study. Cardiovascular-risk stratification was performed according to a simplified version of the Framingham model [including age, diabetes, smoking, systolic blood pressure and body mass index (BMI)]. Arterial 18F–NaF uptake was measured by drawing regions of interest comprising the arteries on each slice of the transaxial PET/CT and normalized to blood 18F–NaF activity to obtain the arterial target-to-background ratio (TBR). The degree of arterial calcification (AC) was measured using a software program providing Agatston-like scores. Differences in mean values and regression analysis were tested. Predictors of AC and TBR were evaluated by univariate and multivariate analysis. p value of 0.05 was considered statistically significant. No correlation was documented between regional calcium load and regional TBR in any of the studied arterial segments. Visible calcium deposition was found to be dependent upon age while it was not influenced by all the remaining determinants of cardiovascular risk. By contrast, 18F–NaF uptake was significantly correlated with all descriptors of cardiovascular risk, with the exception of BMI. Vascular 18F–NaF uptake displays a different regional distribution, as well as different biological predictors, when compared to macroscopic AC. The tight dependency of tracer retention upon ongoing biological determinants of vascular damage suggests that this tool might provide an unexplored window on plaque pathophysiology.