Tehran University of Medical Sciences Frontiers in Biomedical Technologies 2345-5837 0 0 2026 01 04 1165 1165 Akbar Farhadi Istanbul Technical University, Energy Institute, Division of Nuclear research, Istanbul, Turkiye Farhad Zolfagharpour Department of Physics, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran Ahmet Bozkurt Istanbul Technical University, Informatics Institute, Division of Computational Science and Engineering, Istanbul, Turkiye Arash Abdolmaleki Department of Biophysics, Faculty of Advanced Technologies, University of Mohaghegh Ardabili, Namin, Iran Asadollah Asadid Department of Biology, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran 2024 12 03 2025 02 15 Purpose: This article investigates the influence of testicular positioning and surrounding organ compositions on the absorbed dose in the testicles across a wide range of photon energies. Materials and Methods: Using the Digimouse phantom in Geant4 with the mesh approach, the absorbed dose and deposited energy in mouse testicular tissue were calculated. Organ compositions followed ICRP Publication 145 guidelines. Four identical mono-energetic planar radiation sources (10 × 2.2 cm) emitting photons in the 2–10,000 keV range were positioned equidistantly around the mouse phantom at the head, tail, and both sides, 2 cm away, to ensure uniform irradiation. Simulations were conducted both with surrounding organs in anatomically accurate positions and with these organs replaced by air to assess their impact on dose distribution. Results: Without surrounding organs, the absorbed dose was minimally influenced (<6%) by radiation source orientation. When surrounding organs were included, significant differences were observed, particularly at low photon energies (<25 keV), where notable radiation shielding occurred. Above 25 keV, adjacent organs increased energy deposition in testicular tissue due to secondary scattering, with absorbed dose differences between opposing orientations (e.g., head vs. tail) ranging from 30–92%. At 25 keV, surrounding organs did not affect energy deposition. Conclusion: Surrounding organs significantly influence testicular absorbed dose, particularly at low photon energies where shielding dominates, and at higher energies where secondary scattering enhances deposition. These findings highlight the importance of considering organ interactions and source positioning in dosimetry to optimize radiation therapy protocols and reduce risks to sensitive organs. https://fbt.tums.ac.ir/index.php/fbt/article/view/1165 https://fbt.tums.ac.ir/index.php/fbt/article/download/1165/537