Test-retest repeatability of quantitative organ and tissue uptake using 20-minute dynamic multiparametric whole-body...

Recently developed dynamic whole-body PET/CT (D-WB PET/CT) protocols allow for measurements of potentially more precise metabolic parameters than the commonly used semiquantitative SUV. Most notable is the metabolic rate of FDG uptake (MR_FDG), which reflects quantitative glucose uptake into tissues and organs. However, data on the reproducibility of MR_FDG measurements are scarce, particularly in patients with perturbed glucose homeostasis such as type 2 diabetes. We therefore aimed to evaluate the test-retest repeatability of both MR_FDG and SUV in these patients.

Fifteen participants (mean age 71 ± 7 years; 2 females) with type 2 diabetes underwent a short 20-minute [¹⁸F]FDG D-WB PET/CT after 6 h fasting on two consecutive days. Both SUV and MR_FDG images were reconstructed from D-WB PET/CT data obtained 60-80 min post-injection of [¹⁸F]FDG. MR_FDG and SUV data were measured in organs and tissues, and repeatability was assessed with Bland-Altman analysis, intraclass correlation coefficients (ICC), repeatability coefficients (RPC) and coefficients of variation (wCV). There was high repeatability of both SUV_mean and MR_FDG-mean in all measured organs (ICC range: 0.65-0.95 for SUV_mean and 0.66-0.94 for MR_FDG-mean). SUV_mean generally demonstrated higher reliability (ICC) and lower variability (%RPC and %wCV) when compared to MR_FDG-mean. However, MR_FDG test-retest variation was < 19% in most analysed tissues, demonstrating that MR_FDG may be used as a precise marker of treatment response.

This study demonstrates that MR_FDG calculated from D-WB PET/CT exhibit high repeatability, comparable to SUVs across most organs in patients with type 2 diabetes.