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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


M Belley

M Belley*, P Segars, A Kapadia, Duke University, Durham, NC

SU-C-144-4 Sunday 1:00PM - 1:55PM Room: 144

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 256x256x600 voxels (3.125x3.125x3.125mm^3). A monoenergetic rectangular beam of neutrons or gammas with 1.6x10^7 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.

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