Development and validation of a comprehensive S-value database for small animal internal dosimetry in nuclear medicine using the DM_Bra mouse phantom

Animal models are essential in the development of new radiopharmaceuticals in nuclear medicine, particularly for accurate dose calculation in small animal internal dosimetry. This study presents a comprehensive dataset of S-values for eleven commonly used radionuclides, calculated using the DM_Bra mouse phantom with the GATE Monte Carlo simulation code. To validate our approach, we first compared S-values obtained from the DM_Bra phantom with published values derived from the Digimouse phantom using a Tc-99 m source. The differences between the two phantoms range from 0.68% to 12.45% for self-irradiation and from 0.15% to 4.19% for cross-irradiation when the source is the stomach. These results demonstrate good agreement with reference data, supporting the reliability of our dataset. We then expanded our analysis by generating S-values for additional radionuclides, reflecting their usage in both diagnostic and therapeutic applications. Furthermore, to assess the impact of varying mouse geometries on S-values, the DM_Bra phantom (26.9 g) was rescaled to represent two other mouse sizes (19.6 g and 35.9 g). The statistical uncertainty associated with all these S-values remains below 2%. This study offers a valuable resource for internal dosimetry in mice, providing detailed S-values for a wide range of radionuclides and organ geometries, which can be used in small animal PET and SPECT studies.