Pediatric nuclear medicine dosimetry: A monte carlo study on S-value variability due to patient specific characteristics

Evaluation of 18F-FDG absorbed dose ratios in percent in adult and pediatric reference phantoms using DoseCalcs Monte Carlo platform

This study investigates the field of radiation exposure in nuclear medicine, which might have implications for exposure to ionizing radiation in pediatric cases. To demonstrate the difference in radiosensitivity between younger patients and adults and to highlight the need for individualized radiation protection procedures when investigating medical imaging and therapy, this study examines the absorbed dose ratios in percent (ADR%) for 18F-FDG. This parameter is an important indicator, illustrating the percentage of radiation dose absorbed by specific organs/tissues concerning the emitted radiation from different body regions. The methodology involves calculating ADR% in twelve voxel-based models for adults, children, and newborns, as referenced by International Commission on Radiological Protection (ICRP) Publications 110 and 143. The simulations used the 18F positron spectrum from ICRP Publication 107 and Livermore models. These simulations were performed using the DoseCalcs Monte Carlo platform. We have calculated the S-values and ADR% using the DoseCalcs simulations of the 18F positrons and provided a comprehensive dataset of ADR% results. This dataset evaluates the impact of anatomical variation on absorbed dose in target regions. It consists of 141 target regions and 8 different source regions. Significant differences in radiosensitivity were observed in ADR% values among various source-target combinations for each age and sex group. The self-irradiation ADR% reaches up to 95%, while the cross-irradiation ADR% varies, ranging approximately from 0.1% to 12%, depending on the mass of the target organ, the distance between it and the source organ, and the chemical composition of these organs. Also, the variations observed across different age and sex phantoms highlight the importance of personalized internal dosimetry, especially for pediatric cases with heightened radiosensitivity. Healthcare practitioners can use the dataset of ADR% values as the first stage to illustrate variability and optimize nuclear medicine imaging with 18F-FDG while reducing radiation risks.