18Fluorodeoxyglucose Positron Emission Tomography Imaging of Atherosclerotic Plaque Inflammation Is Highly Reproducible: Implications for Atherosclerosis Therapy Trials

18Fluorodeoxyglucose Positron Emission Tomography Imaging of Atherosclerotic Plaque Inflammation Is Highly Reproducible: Implications for Atherosclerosis Therapy Trials

James H. F. Rudd, Kelly S. Myers, Sameer Bansilal, Josef Machac, Ash Rafique, Michael Farkouh, Valentin Fuster, Zahi A. Fayad

18Fluorodeoxyglucose positron emission tomography (FDG-PET) can image inflammation in atherosclerosis, and serial imaging might be used to measure drug effectiveness. To plan clinical trials, the variability of FDG uptake must be known. We imaged the carotid arteries and aorta in 11 subjects twice within 2 weeks. Interscan reproducibility was excellent in all regions (intraclass correlation coefficients [ICC] 0.79 to 0.92), as was inter- and intraobserver agreement (ICC 0.90 to 0.98, excluding aortic arch). We provide sample size estimates for future studies. This work supports future use of FDG-PET for noninvasively testing novel drugs in atherosclerosis.

Objectives

This study tested the near-term reproducibility of 18fluorodeoxyglucose positron emission tomography (FDG-PET) imaging of atherosclerosis.

Background

It is known that FDG-PET can measure inflammation within the aorta, carotid, and vertebral arteries with histologic validation in humans and animal models of disease. By tracking changes in inflammation over time, PET could be used as a surrogate marker of antiatheroma drug efficacy. However, the short-term variability and reproducibility of the technique are unknown.

Methods

We imaged the carotid arteries and aorta in 11 subjects with FDG-PET/computed tomography twice, 14 days apart. We assessed interobserver and intraobserver agreement and interscan variability.

Results

Interscan plaque FDG variability over 2 weeks was very low; intraclass correlation coefficients (ICC) ranged between 0.79 and 0.92. Interobserver agreement was high across all territories imaged except aortic arch (ICC values from 0.90 to 0.97, arch 0.71). Intraobserver agreement was high, with ICC values between 0.93 and 0.98.

Conclusions

Spontaneous change in plaque FDG uptake is low over 2 weeks, with favorable inter- and intraobserver agreement. Power calculations suggest that drug studies using FDG-PET imaging would require few subjects compared with other imaging modalities. This study strengthens the case for FDG-PET as a noninvasive plaque imaging technique.