Objective:To investigate the effects of total-body PET/CT imaging with short acquisition time on image quality and lesion detectability in lungs and parenchymal organs.Methods:Sixty patients (31 males, 29 females, age (61.1±11.8) years) with pulmonary nodules (PN) and 53 patients (29 males, 24 females, age (56.7±17.2) years) with parenchymal organ lesions (POL) who underwent total-body PET/CT imaging in the First Affiliated Hospital of Shandong First Medical University between October 2021 and April 2022 were retrospectively analyzed. The acquisition time with PET was 600 s, and the reconstructed images were divided into 6 groups based on different duration (30, 60, 120, 180, 300 and 600 s), namely G30, G60, G120, G180, G300 and G600 groups. The subjective analysis was carried out with the 5-point Likert scale in 3 aspects: the overall impression of image quality, noise, and lesion conspicuity. The objective analysis indicators included the SUV mean of the mediastinal blood pool (MBP); the SUV mean, standard deviation (SD) and signal-to-noise ratio (SNR) of the liver; SUV max and target-to-background ratio (TBR) of the lesions. Differences of the indicators among 6 groups were analyzed by Friedman test with Bonferroni correction. G600 served as the reference for the other 5 groups to test their lesion detectability. Results:The subjective image quality of different groups for PN and that of G120, G180, G300 groups for POL could meet the needs of clinical diagnosis in terms of the overall image quality, noise, and lesion conspicuity (all scores>3). There was no significant difference in the SUV mean of MBP among different time groups (median for PN: 1.52-1.56, median for POL: 1.35-1.47; χ2 values: 10.23, 11.02, both P>0.05). Difference was not found in SUV mean of the liver either (median for PN: 2.51-2.56, median for POL: 2.33-2.40; χ2 values: 8.35, 8.93, both P>0.05). The liver SD significantly increased along with the shortened acquisition time ( χ2 values: 400.99, 400.00, both P<0.001; z values: from -16.90 to -3.15, all P<0.003). The SNR significantly decreased along with the shortened acquisition time ( χ2 values: 397.32, 400.00, both P<0.001; z values: 2.98-16.90, all P<0.003). The SUV max (median for PN: 3.55-4.01, median for POL: 5.77-6.08; χ2 values: 8.58, 3.02, both P>0.05) and TBR (median for PN: 2.42-2.81, median for POL: 2.36-2.45; χ2 values: 9.83, 3.69, both P>0.05) of lesion were not significantly different among 6 groups. Taking G600 group as a reference, the lesion detection rates were 100% in G30 group and other 4 groups for PN (81/81) and in G120, G180, G300 groups for POL (80/80). Conclusion:Total-body PET/CT imaging with acquisition time of 30 s for lungs and that with acquisition time of 120 s for parenchymal organs are feasible for clinical use, with the PET image quality and lesion detectability maintained.

Total-body PET/CT, with its long axial field of view and high sensitivity detector, has shown potential for reducing the dose of radiopharmaceuticals. However, pediatric patients are significantly more sensitive to radiation and have a higher long-term cancer risk than adults, posing fundamental challenges for dose management in PET/CT examinations for these patients. In this article, the technical characteristics of total-body PET/CT and its radiation exposure status in children were systematically analyzed. The radiation exposure could be controlled by the following optimization strategies: adjusting the CT exposure parameters, optimizing the scanning mode, adding reconstruction algorithm, and reducing the injected dose of radioactive tracer. By addressing both external and internal radiation during the PET/CT scanning process, the overall radiation dose received by pediatric patients can be reduced within a certain range. In addition, this article also discusses the technical differences between “total-body” and “whole-body” concepts, and emphasizes that the future optimization of radiation dose in pediatric PET/CT should be realized by integration of personalized scanning protocols. Through reasonable management of scanning protocols and processes, low-dose and high-quality PET/CT imaging can be achieved in clinical environments, thus maximizing protection of pediatric patient health while minimizing the risks associated with ionizing radiation exposure.