Atherosclerosis inflammation imaging with ¹⁸F-FDG PET: Carotid, iliac, and femoral uptake reproducibility, quantification methods, and recommendations

Atherosclerosis imaging with ¹⁸F-FDG PET is useful for tracking inflammation within plaque and monitoring the response to drug therapy. Short-term reproducibility of this technique in peripheral artery disease has not been assessed, and the optimal method of ¹⁸F-FDG quantification is still debated. We imaged 20 patients with vascular disease using ¹⁸F-FDG PET twice, 14 d apart, and used these data to assess reproducibility measures and compare 2 methods of ¹⁸F-FDG uptake measurement. We also reviewed the literature on quantification methods to determine the optimal measures of arterial ¹⁸F-FDG uptake for future studies. Methods: Twenty patients with vascular disease underwent PET/CT of the iliac, femoral, and carotid arteries 90 min after ¹⁸F-FDG administration. In 19 patients, repeat testing was performed at 2 wk. Coregistration and attenuation correction were performed with CT. Vessel ¹⁸F-FDG uptake was measured as both the mean and maximum blood-normalized standardized uptake value (SUV), known as the target-to-background ratio (TBR). We assessed interscan, interobserver, and intraobserver agreement. Results: Nineteen patients completed both imaging sessions. The carotid and peripheral arteries all have excellent short-term reproducibility of the ¹⁸F-FDG signal, with intraclass correlation coefficients all greater than 0.8 for all measures of reproducibility. Both mean and maximum TBR measurements for quantifying ¹⁸F-FDG uptake are equally reproducible. ¹⁸F-FDG uptake was significantly higher in the carotid arteries than in both iliac and femoral vessels (P < 0.001 for both). Conclusion: We found that both mean and maximum TBR in the carotid, iliac, and femoral arteries were highly reproducible. We suggest the mean TBR be used for tracking systemic arterial therapies, whereas the maximum TBR is optimal for detecting and monitoring local, plaque-based therapy.