Assessing the applicability of PMOD residence times model for PET image-based radiation dosimetry

The effective dose represents the overall internal radiation exposure to the whole body when exposed to radiation sources. This study aims to compare conventional and software-aided methods to derive the effective dose. In the present study, ⁸F-T807 and ¹⁸F-Mefway, specific radiotracers for the paired helical tau and serotonin 1A receptor, were administered to healthy subjects (n = 6, each radiotracer), following which whole-body positron emission tomography (PET) images were obtained for 2 h. Subsequently, time-activity curves for major organs were obtained, and the residence times were calculated using the "conventional" and "Residence Times model" tools in PMOD software. The residence times from each method was input into OLINDA/EXM software, and the effective dose was estimated. The differences in the average residence times of the brain, heart, lung, and liver were 18.4, 20.8, 10.4, and 13.3% for ¹⁸F-T807, and 17.5, 16.4, 18.1, and 17.5% for ¹⁸F-Mefway, respectively. For the mean effective dose, the error rates between the methods were 3.8 and 1.9% for ¹⁸F-T807 and ¹⁸F-Mefway, respectively. The organs that showed the greatest difference in the absorbed dose were the urinary bladder for ¹⁸F-T807 (40.4%) and the liver for ¹⁸F-Mefway (14.1%). This method of obtaining the residence time using PMOD can be easily used to derive the effective dose, and is applicable in evaluating the safety of radiotracers for clinical trials.