Temporal relationship between ¹⁸F-sodium fluoride uptake in the abdominal aorta and evolution of CT-verified vascular calcification

Background: Fluoride-18 sodium fluoride (¹⁸F-NaF) localizes in microcalcifications in atheroma. The microcalcifications may aggregate, passing the resolution threshold to visualize on computed tomography (CT). We evaluated serial NaF positron emission tomography (PET)-CT scans to determine the temporal relationship between vascular NaF uptake and CT evident calcification in the abdominal aorta. Methods: Prostate cancer patients who had at least 3 NaF PET-CT scans over at least 1.5 years were retrospectively enrolled. Regions of interest were traced in the abdominal aorta on both PET and CT images, excluding skeletal NaF activity. The maximum standardized uptake value (SUV_max) of NaF and the density and volume of calcium (exceeding 130 HU) were summed and divided by the number of slices to produce the SUV_max/slice and the mm³·slice⁻¹ of calcium. Results: Of 437 patients, 45 patients met criteria. NaF uptake waxed and waned between scans, while the calcium volume plateaued or increased over time. NaF uptake correlated with calcium volume on the baseline scan (P =.60, <.0001^†) and calcium volume increment, especially from 1.0 to 1.5 years (r =.79, P <.0001^†). Patients with persistently high NaF uptake showed a higher calcium volume increment (0-1.5 years) than patients with low or transiently high NaF uptake. Conclusions: Abdominal aortic NaF uptake varied over time. NaF uptake on the baseline scans and high NaF uptake on the serial scans preceded an increase in calcium volume, especially by 1.0-1.5 years. Persistently high NaF uptake was associated with a greater increment in calcium volume than patients with transiently elevated or persistently low fluoride uptake.