Regional variability of atherosclerotic disease in various anatomic segments of aorta as revealed by FDG-PET/CT imaging

Objectives The aim of this study was to demonstrate the regional variability of atherosclerosis quantification in different segments of aorta (infradiaphragmatic vs supradiaphragmatic).

Methods Thirty two patients, who underwent PET/CT imaging for lung cancer, were included in this study. Each patient underwent multiple-time-point PET/CT imaging at 1, 2 and 3 hours following the administration of FDG. Atherosclerotic plaque FDG-uptake, quantified as weighted average SUVmean [wA-SUVmean = ∑ (SUVmean x surface area x thickness) / ∑volume], was determined by placing ROIs around the arterial wall from the cardiac origin of the aorta down to the level of the aortic bifurcation. Infradiaphragmatic and supradiaphragmatic atherosclerosis were compared using paired t-test.

Results Preliminary data of 32 patients with a mean age of 65 ± 14 showed that wA-SUVmean was higher in infra-diaphragmatic aorta compared to the supra-diaphragmatic aorta at all three time-points; however the difference was significant only in 3 hour time-point images (wA-SUVmean = 1.27, 1.47 in supra- and infradiaphragmatic aorta, respectively, P < 0.001).

Conclusions The preliminary data show increased FDG uptake in the infradiaphragmatic aorta compared to the supradiaphragmatic aorta. This effect reaches statistical significance only in PET images acquired 3 hours following the administration of FDG. Two phenomena, the delayed accumulation of FDG in atherosclerotic plaques and the declining levels of FDG in the blood pool, could account for this important observation. These data support the benefit of delayed-time-point imaging in assessing atherosclerotic plaque activity in any setting and its capabilities in the assessment of new treatment.

Research Support Supported in part by VISN 4 CPPF grant.