Monte Carlo Simulation of Testicular Absorbed Dose in the Digimouse Phantom: Assessing the Impact of Organ Position and Surrounding Tissue Composition
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Abstract
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.
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