Dynamic changes of blood pool activity in the arteries and the veins over time on FDG-PET/CT images: Implications of this observation in assessing atherosclerotic lesions

Objectives The main objective of this research was to determine the optimal timing for examining major arteries for the presence of atherosclerotic plaques and testing the novel quantitative approaches for efficient use of FDG-PET/CT imaging in this setting.

Methods In this prospective study, nine patients who underwent FDG-PET/CT imaging for assessment of disease stage for lung cancer before surgery were included. Following the administration of the standard dose of FDG, whole body images were acquired at 1, 2, and 3 hours. FDG-uptake in aortic plaques, quantified as weighted average SUVmean (ASUVmean) [∑ (SUVmean x surface area x thickness) / ∑volume], was determined in the aorta by placing ROIs around the arterial wall in every slice (5 mm) of the attenuation corrected PET/CT images. Regions of interest assigned to the femoral veins and mean venous blood pool activity (VSUVmean) was measured; ArterioVenous Ratio (AIR) was calculated as ASUVmean/VSUVmean. For each patient, change of ASUVmean, VSUVmean, and AVR was evaluate in each time point.

Results VSUVmean showed rapidly declining activity from the first hour to the third hour (1.4 , 1, and 0.6 respectively). Similarly, the arterial blood appeared to decline with time (1.9, 1.5, and 1.3). In contrast, AVR revealed a significant rise with time (1.3, 1.6, and 2.1).

Conclusions Blood pool activity in the arterial system in early images (within the first 2 hours) following the administration of FDG, substantially decreases the efficacy of this powerful methodology in assessing atherosclerotic burden. These data described in this abstract imply that further delays in initiating PET images may improve the ability to visualize atherosclerotic plaques