Dual time-point [¹⁸F]FDG PET imaging for quantification of metabolic uptake rate: Evaluation of a simple, clinically...

We aimed to investigate whether a clinically feasible dual time-point (DTP) approach can accurately estimate the metabolic uptake rate constant (K_i) and to explore reliable acquisition times through simulations and clinical assessment considering patient comfort and quantification accuracy.

We simulated uptake kinetics in different tumors for four sets of DTP PET images within the routine clinical static acquisition at 60-min post-injection (p.i.). We determined K_i for a total of 81 lesions. K_i quantification from full dynamic PET data (Patlak-K_i) and K_i from DTP (DTP-K_i) were compared. In addition, we scaled a population-based input function (PBIF_scl) with the image-derived blood pool activity sampled at different time points to assess the best scaling time-point for K_i quantifications in the simulation data.

In the simulation study, K_i estimated using DTP via (30,60-min), (30,90-min), (60,90-min), and (60,120-min) samples showed strong correlations (r ≥ 0.944, P < 0.0001) with the true value of K_i. The DTP results with the PBIF_scl at 60-min time-point in (30,60-min), (60,90-min), and (60,120-min) were linearly related to the true K_i with a slope of 1.037, 1.008, 1.013 and intercept of -6 × 10^-4, 2 × 10^-5, 5 × 10^-5, respectively. In a clinical study, strong correlations (r ≥ 0.833, P < 0.0001) were observed between Patlak-K_i and DTP-K_i. The Patlak-derived mean values of K_i, tumor-to-background-ratio, signal-to-noise-ratio, and contrast-to-noise-ratio were linearly correlated with the DTP method.

Besides calculating the retention index as a commonly used quantification parameter inDTP imaging,our DTP method can accurately estimate K_i.