NaF PET/CT in Assessing the Atherosclerotic Burden in Major Arteries Supplying the Lower Limbs

Objectives: We aimed to assess the association between age and active atherosclerotic arterial wall calcification in major arteries supplying the leg by quantifying NaF uptake on PET/CT scans.

Methods: In this study, 75 healthy controls (38 males and 39 females, aged 21-66, mean age 42.8 ± 13.5 years) and 44 patients with a high risk of cardiovascular disease (21 males and 24 females, aged 23-75, mean age 56.1 ± 11.5) underwent PET/CT imaging 90 minutes following the injection of the NaF (2.2MBq/Kg). A standard and uniform protocol (GE Discovery STE, VCT, RX, and 690/710) was used for acquisition and CT imaging (140kV, 30-110 mA, noise index 25, 0.8 seconds per rotation, slice thickness 3.75 mm) was performed for attenuation correction and anatomic referencing with PET images. PET images were also corrected for attenuation, scatter, scanner dead time, and random coincidence. Analysis was performed on axial sections of the arteries using standard operator guided computer software (OsiriX MD software, version 9.0.2) and the following vessels were examined: common iliac artery (CIA), external iliac artery (EIA), femoral artery (FA), popliteal artery (PA). Quantification of NaF uptake in the CIA reached from the bifurcation of the abdominal aorta to the beginning of the EIA. EIA uptake was noted from the division of the CIA into the internal and external iliac arteries to the level of the inguinal ligament. FA uptake was measured from the inguinal ligament to the crossing of the adductor hiatus. PA uptake was measured from the adductor hiatus to the level of the popliteus. Regions of interests were created that precisely defined the arterial vessels. Average SUVmean (aSUVmean) was calculated for each arterial segment in all subjects. The potential association of NaF uptake with age in controls and patients was investigated by means of linear correlation analysis.

Results: In patients, the correlation of aSUVmean with age was highly significant in all four arteries: CIA (r=0.35, p=0.0006), EIA (r=0.44, p=0.00001), FA (r=0.57, p=<0.00001), and PA (r=0.58, p=0.002). In controls, the correlation of aSUVmean with age was found to be: CIA (r=0.15, p=0.07), EIA (r=0.11, p=0.15), FA (r=0.18, p=0.01), and PA (r=0.34, p=0.24).

Conclusions: NaF PET/CT demonstrated a larger atherosclerotic burden in the major arteries in the legs of patients with significant cardiovascular risk than in healthy controls. In patients, this higher burden was significantly associated with age, whereas the lower burden in healthy controls was not. NaF PET/CT appears to be a useful imaging modality for assessment of the atherosclerotic burden in the major arteries supplying the lower limbs.