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Monte Carlo Calculation of Radiation Exposure to Astronauts Using 4D Extended Cardiac-Torso (XCAT) Phantoms

J Houri*, P Segars, A Kapadia, Duke University, Durham, NC


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Current Monte Carlo simulations modeling space radiation exposure typically use simplistic human phantoms with low anatomical detail and minimal variability in physical characteristics. We developed a new Geant4-based simulation framework (ATOM - Atmospheric, Trajectory, and Orbital Modeling) that incorporates highly realistic and diverse 4D extended cardiac-torso (XCAT) digital phantoms, combined with NASA models of planetary atmospheres, orbits and spaceflight trajectories, and galactic cosmic radiation (GCR) to evaluate radiation exposure during spaceflight and in extraterrestrial habitats.

Methods: ATOM utilizes voxelized XCAT phantoms, which are anatomically realistic human body models with over 100 segmented structures including 26 different materials. XCAT models range in age from neonate to 78 years and cover various combinations of height, weight, and BMI. The free-space radiation field is determined by the Badhwar-O’Neill model, which provides spectra for each GCR ion depending on radial distance from the Sun and solar activity. Atmospheres are simulated using NASA’s global reference atmospheric models, which provide mean atmospheric data for any altitude, latitude, longitude, and time. Planetary orbits and rotation along with spaceflight trajectories are described by NASA’s SPICE observation geometry information system.

Results: ATOM was used to determine the dose rate to an unshielded male XCAT phantom on the surface of Mars at the Curiosity rover landing site at local noon for standard conditions and in the presence of an atmospheric dust storm. Under maximum atmospheric dust loading, effective dose decreased by 7.04%. Changes in individual organ dose ranged from -1.21% for red bone marrow to 3.10% for lung.

Conclusion: ATOM, utilizing XCAT phantoms, is a promising tool for accurate estimation of whole-body and organ dose in space. ATOM’s geometric versatility makes it ideal for evaluating doses to diverse populations of phantoms within different types of planetary habitats and spacecraft, enabling optimization of mission planning with respect to radiation exposure.


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