Three hours after injection of 18F-fluoro-2-deoxy-D-glucose is optimal for imaging atherosclerosis in carotid arteries with positron emission tomography

Objectives We investigated the optimal imaging time after injection of 18F-fluoro-2-deoxy-D-glucose(FDG) to measure atherosclerosis in carotid arteries with positron emission tomography/computed tomography (PET/CT).

Methods The study subjects were 12 patients who have had recent symptomatic plaques in their carotid arteries. For carotid plague imaging, we underwent FDG-PET/CT imaging at 2 hr in five and at 3 hr in seven patients after FDG injection. Vessel wall uptake were measured using the maximal standardized uptake value (maxSUV) and, mean and maximal blood normalized standardized uptake value (target-to-background ratio, TBR) of the symptomatic carotid arteries. Blood pool activity was measured as mean SUV of superior vena cava (SVC) and jugular vein in these patients as well as age and sex matched 14 patients who underwent whole body FDG-PET/CT examinations 1 hr after FDG injection as a routine follow-up schedule.

Results FDG-PET/CT revealed visible FDG uptake in all patients with symptomatic carotid plaque. There were no difference of maxSUV between 2 hr and 3 hr groups (2.62±0.45 vs. 3.00±0.85, P = 0.335). However, maximal and mean TBR values that were normalized to blood pool activity in SVC were different significantly (2.04±0.22 vs. 3.54±0.62, P<0.05; 1.65±0.15 vs. 2.70±0.42, P < 0.05, respectively). TBR normalized to jugular vein activity also showed the same difference (P < 0.05). Blood pool activity in SVC and jugular vein showed a time-dependent decrease in SUV values (SUV normalized for SVC at 1, 2 and 3 hr: 1.18±0.15, 0.85±0.05 and 0.56±0.10, P < 0.05; SUV normalized for jugular vein: 1.04±0.16, 0.79±0.03 and 0.66±0.04, P < 0.05).

Conclusions Our results suggest that imaging at 3 hr after 18F-FDG injection may be optimal to assess atherosclerosis in carotid arteries as it shows higher TBR and lower blood pool activity