Correlation of F18-sodium fluoride (NaF) uptake and calcification of the major blood vessels of the F18-NaF PET/CT scans

Purpose: F18-sodium fluoride (NaF) PET/CT can be used to identify skeletal metastases, including localization and determination of the extent of disease. Uptake of NaF can also indicate active calcification in the vessel walls, a potential biomarker for high risk plaques. We investigate the correlation of NaF target-to-background ratio (TBR) and calcium score (CS) of the plaques in the major blood vessels of the patients scanned with the F18-NaF PET/CT for the indication of skeletal metastases.

Methods: 179 patients with suspected bone metastasis imaged with F18-NaF PET/CT, were retrospectively enrolled in the study. Patient demographics were 148 males and 31 females, age: 59.7±16.3 yr, height: 1.74±0.09 m, weight: 83.2±21.0 kg, and BMI: 19.8±5.1. TBR and calcium score (HU>130) of the plaques in the major blood vessels of the carotid artery, brachiocephalic trunk, aortic arch, thoracic aorta, abdominal aorta, iliac artery, and femoral artery were grouped into NaF-positive (TBR > 1.5) or NaF-negative (TBR < 1), as well as calcium scores (>1000, 400-1000, 100-399, and 0-100). Results: There were 865 plaques in 122 patients (68.2%) with NaF-positive or calcified plaques. These patients were significantly older than the rest of the patients (P<0.05). Five plaques in four patients were NaF-positive but without calcification. The frequency of calcified or NaF-positive plaques was higher in men than in women (P<0.05). Higher TBR also correlated with the degree of calcification (CS), except at the onset of calcification when NaF uptake was higher in the CS 0-100 group (lower calcification) than in the CS 100-399 group (higher calcification). Conclusions: Gender and age play a significant role in plaque formation. Larger amount of calcium typically implies higher NaF uptake. There is a higher NaF uptake at the onset of calcification, suggesting NaF can be a potential biomarker for higher risk plaques.