BACKGROUND: Atherosclerotic plaque vulnerability is comprised by plaque composition driven by inflammatory activity and these features can be depicted with 3D ultrasound and 2-[18F]FDG-PET, respectively. The study investigated timely changes in carotid artery plaque inflammation and morphology after a thromboembolic event with PET/CT and novel ultrasound volumetric grayscale median (GSM) readings. Patients with a single hemisphere-specific neurological symptom and the presence of an ipsilateral carotid artery atherosclerotic plaque were prospectively included to both 2-[18F]FDG PET/CT and 3D ultrasound scans of the plaque immediately after their event and again three months later. On PET/CT images the maximum standardized uptake value (SUVmax) was measured and the volumetric ultrasound acquisitions were analyzed using a semiautomated software measuring GSM values.

RESULTS: Baseline scans were performed by a mean of 7 days (range 2-14) after the symptom and again after 98 days (range 91-176). For the entire group (n = 14), we found a decrease in average SUVmax from baseline to follow-up of - 0.18 (95% confidence interval: - 0.34 to - 0.02, P = 0.034). GSM did not increase significantly over time (mean change: + 2.21, 95% confidence interval: - 17.02 to 21.44, P = 0.808).

CONCLUSION: A decrease in culprit lesion 2-[18F]FDG-uptake 3 months after an event indicates a decrease in inflammatory activity, suggesting that carotid plaque stabilization over time. 3D ultrasound morphological quantitative differences in GSM were not detectable after 3 months.