What is the natural history of ¹⁸F-FDG uptake in arterial atheroma on PET/CT? Implications for imaging the vulnerable plaque

Abstract 

Purpose

Increased uptake of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) in atherosclerotic plaque on Positron Emission Tomography (PET), predicts vulnerability. Recent studies have shown that the PET signal is reproducible over a 2-week period and as a result drug trials are underway. However, the natural history of these lesions is unknown. The aim of this study is determine the natural history of increased vascular wall uptake of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG).

Methods

Following institutional ethics committee approval, we retrospectively examined PET/CT images of patients from our Institution that had at least 4 examinations in the last 5 years. This represented 205 studies in total, from 50 patients (29 men, 21 women, mean age 49.4±12.1 years, mean 5.1±1.7 studies/patient). The mean follow-up was 27.2±11.8 months. The carotids and the aorta were evaluated for increased ¹⁸F-FDG uptake with a maximum Standardized Uptake Value (SUV_max) >2.5, and >3.0, and calcification. Plots of SUV_max and Hounsfield units (HU) were made versus time.

Results

The initial prevalence of increased focal arterial ¹⁸F-FDG uptake was 17/50 patients and of arterial calcification 19/50. 132 sites of ¹⁸F-FDG uptake in total were observed longitudinally. ¹⁸F-FDG vascular uptake did not persist with time. There was no correlation between ¹⁸F-FDG uptake and HU. No calcifications developed at sites of focal increased ¹⁸F-FDG uptake.

Conclusions

Arterial lesions with increased ¹⁸F-FDG uptake represent transient phenomena. This data is important for the interpretation of findings of clinical trials using arterial ¹⁸F-FDG uptake as an imaging biomarker to monitor pharmacological intervention.

Abbreviations: ¹⁸F-FDG¹⁸, F-fluorodeoxyglucose, PET, Positron Emission Tomography, CT, computed tomography, CRP, C-reactive protein, MBq, MegaBecquerel, SUV, standardized uptake value, SD, standard deviation, HU, Hounsfield unit

Keywords: Atherosclerosis, Imaging agents, Positron Emission Tomography, Fluorodeoxyglucose, Vulnerable plaque