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

Abstract

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.