The feasibility of ultralow-activity 18F-FDG dynamic PET imaging in lung adenocarcinoma patients through total-body PET/CT scanner

Objective To explore the feasibility of ultralow-activity 18 F-FDG total-body dynamic PET imaging for clinical practice in patients with lung adenocarcinoma. Methods Eight of 18 patients were randomly injected with 18 F-FDG with full activity (3.7 MBq/kg) for total-body dynamic PET imaging, while 10 received one-tenth activity (0.37 MBq/kg). The generated time-to-activity curves (TACs) according to the regions of interest (ROIs) were processed by PMOD through standard FDG two-tissue compartment model fitting. The kinetic constant rates (K1, K2, K3, and Ki), radiation dose, prompt counts, and data storage size were analysed between the full- and ultralow-activity groups. The SUVmax-Tumour/SUVmax-Liver and SUVmax-Tumour/SUVmax-Muscle on static PET images were also assessed. Results Each of the fitted models has a satisfactory goodness-of-fit with R 2 greater than 0.9 except 3 (3/234) in ultralow-activity group, where one in pancreas ( R 2 = 0.851), another one in muscle ( R 2 = 0.868), and the third one in bone marrow ( R 2 = 0.895). All the fitted models in the full-activity group had a better goodness-of-fit than those in the ultralow-activity group. However, no significant differences were found in any of the kinetic metrics or image quality between the two groups except in the reduction of radiation dose and data storage size. Conclusions The 10 × reduction of injected 18 F-FDG could achieve comparable kinetic metrics and T/N ratios by total-body dynamic PET imaging in lung adenocarcinoma patients. Ultralow-activity total-body PET imaging is feasible for clinical practice in oncological patients without obesity, especially in dynamic PET scanning.