SU‐C‐144‐04: Whole Body and Relative Organ Dose Values From Neutron and Gamma Irradiation of the Liver and Breast in a Voxelized Anthropomorphic Phantom Using Monte Carlo Methods

Purpose: Using Monte Carlo, we estimated the 3‐dimensional organ‐dose distribution for neutron and gamma irradiation of the male liver, female liver, and female breasts for neutron‐and gamma‐stimulated imaging. Understanding the dose distribution from these diagnostic scans is essential for assessing radiation risk. Methods: Monte Carlo was performed using the GEANT4 GATE application and a voxelized XCAT human phantom. Male and female XCAT phantoms were voxelized into 256×256×600 voxels (3.125×3.125×3.125mm^{^}3). A monoenergetic rectangular beam of neutrons or gammas with 1.6×10^{^}7 particles was irradiated onto a 2cm thick slice at eight different angles from 0–180°. For the liver, the beam rotated about the axis of the torso. For the breast, the beam rotated around the pendulous breasts. The neutron irradiation utilized a 5MeV neutron beam and the gamma irradiation utilized a 7MeV gamma beam. Dose volume histograms were computed to analyze the absolute and relative doses in each organ. Results: The neutron irradiation of the liver for both the male/female phantoms imparted the highest organ dose to the liver. All other organ doses were below ∼15% of the liver dose, except for the stomach‐wall which registered ∼80% and ∼70% respectively for the male and female. The highest dose for gamma irradiation of the liver occurred in the stomach‐wall, with a relative liver dose of ∼70% in the male and ∼75% in the female. Most other organ doses were below ∼10% of the stomach dose. For the breast scans, both the neutron and gamma irradiation registered maximum organ doses in the breasts, with all other relative organ doses being well below 2% of the breast dose. Conclusion: Neutron and gamma irradiation of target organs such as the liver and breasts imparts the maximum dose to the primary target organ and a considerably lower dose to proximal organs outside of the beam plane.