Toward three-dimensional patient-specific internal dosimetry using GATE Monte Carlo technique. (June 2022)

• Record Type: Journal Article
• Authors: Karimipourfard, M.; Sina, S.; Alavi, M.S.
• Is Part Of: Radiation physics and chemistry. Volume 195(2022)
• Publication Date: 2022-06
• Subjects: Internal dosimetry -- Monte Carlo -- GATE -- TAC -- Patient dosimetry; Radiation chemistry -- Periodicals; Radiometry -- Periodicals; Radiation -- Periodicals; Chimie sous rayonnement -- Périodiques; 539.2
• DOI: 10.1016/j.radphyschem.2022.110046
• Languages: English
• ISSNs: 0969-806X

Abstract

Abstract: Patient-specific internal dosimetry with a high accuracy is one of the most significant issues in the field of nuclear medicine. In recent investigations, there has been a dramatic alter in the different methods for computing the correct organ doses from the injected radioactivity. Monte Carlo simulations have yielded highly accurate results for voxel-based dosimetry techniques. This paper aims to present a precise methodology based on full Monte Carlo simulations, and time-activity curve estimation using three individual scans over 90 min. In this study, a dataset of patients who were injected with F-Fluor-2-D-Glucose, F18-FDG (10 normal cases, 60 ± 8.2 kg, injected activity, 370 ± 10 MBq), was acquired in 3 different time sequences (20, 60, 90 min post-injection). First, the GATE Monte Carlo results were validated using experimental measurements. Subsequently, the Monte Carlo code was considered for S-value calculations. The CT and PET images were used to obtain attenuation maps and activity distribution inside the patients' phantom, respectively. The CT and PET images were registered using an image processing software to achieve the same matrix and pixel sizes. Regions of interest, such as the kidneys, spleen, bladder, lung, pancreas, liver, stomach, and heart wall, were identified on CT images. The segmented ROIs of the CT images were reconstructed and the voxelized phantom and voxelized source of each patient at specific time intervals were generated. The time activity curves (TACs) were obtained based on PET images. The results of the F18-FDG dose distribution in patient-specific phantoms indicate that the bladder, lung, heart, and liver absorbed more activity than other organs, as expected from the PET images. Close agreement was observed between the results obtained in this study and those of previous investigations that used biokinetic models. The dose per activity values was reported within 0.02–0.06 mGy/MBq for most organs with simulation uncertainty less than 7%. There is ample room for further progress in the clinical use of the Monte Carlo method and the improvement of the phantom-based model. Highlights: Estimate internal patient dose related to GATE Monte Carlo method. The procedure of the mentioned method is validated with experimental and simulation steps. TAC was performed based on static time sequences. The results of TAC estimation were compared with the biokinetic curves of previous studies. This study surveyed the internal dosimetry procedure based on patient data.