Fluorine-18-labeled sodium fluoride (18F-NaF) uptake measured with PET in the vessel walls can indicate active microcalcification, a potential biomarker of higher-risk plaques, which are not indicated by macrocalcification measured with computed tomography (CT). The aim of this study was to determine the extent to which 18F-NaF uptake is correlated with calcification at arterial plaques in cancer patients undergoing whole-body PET/CT imaging.
Patients and methods
Image data from 179 patients who underwent 18F-NaF PET/CT were evaluated retrospectively. Plaques were categorized into four groups by calcium score (CS) on CT: CS1 (≥1000); CS2 (400–999); CS3 (100–399), and CS4 (<100) and into three groups by 18F-NaF target-to-background ratio (TBR) on PET: TBRlow (≤1.0), TBRmedium (1.0–1.5), and TBRhigh (>1.5). Correlations between 18F-NaF uptake and CS were evaluated.
Plaques with 18F-NaF uptake or arterial calcification were observed in 122 (76%) of the 179 patients. We found a weak but statistically significant positive correlation between CS and 18F-NaF uptake. The TBR in CS1 plaques was higher than those in CS3 and CS4 plaques, and the TBR in CS2 plaques was higher than that in CS3 plaques (P<0.05). Compared with patients whose plaques were with 18F-NaF uptake (TBR>1.5) or arterial calcification (CS>0), patients without plaques of 18F-NaF uptake or calcification were significantly younger (P=0.00) or with significantly more women (P=0.02).
Our finding of a weak but significant positive correlation between 18F-NaF uptake and arterial calcification suggests that 18F-NaF PET/CT could provide complementary information of active microcalcification for atherosclerosis evaluation in cancer patients.