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Organ dose conversion factors for murine galactic cosmic ray irradiation

Year: 2026
Type: article
Abstract: Galactic cosmic rays (GCR) are a principal source of ionizing radiation exposure for astronauts during deep space missions. Given the ambition to expand manned space exploration to distant destinations like Mars, it is essential to accurately predict the radiation doses astronauts are likely to encounter and the consequent biological impacts. Accurate dose predictions are important for operational radiation safety, ensuring that risk assessments and protective measures are appropriately calibrated to the myriad of challenges of deep space travel. The GCRsim facility at the NASA Space Radiation Laboratory enables small animal radiobiology studies of GCR exposure, offering a controlled setting to mimic the complex radiation conditions found in deep space. This manuscript introduces a series of Dose Conversion Factors (DCFs) which enable rigorous absorbed dose calculations for mice irradiated at the GCRsim. METHODS A formalism was introduced for calculating organ-level and voxel-level radiation dose to a representative mouse phantom, based on DCFs quantifying radiation absorbed dose per unit fluence of different GCRsim beam components for different irradiation orientations. The PHITS Monte Carlo code was employed to compute the DCFs in units of Gy∙cm 2 ∙ion −1 . RESULTS A library of murine DCFs were derived using the PHITS Monte Carlo code for six irradiation orientations: right-left, anterior-posterior, superior-inferior, and their opposed variations. Absorbed doses to the murine total body were calculated with the method and compared with ion chamber measurements, which agreed within 10%. CONCLUSION A library of dose conversion factors for mouse irradiation at GCRsim was developed and validated against physical measurements. These DCFs account for organ-specific variations in radiation dose from different GCRsim beam components, enabling improved assessments of potential radiogenic effects, toward improving astronaut safety measures for future deep space missions.
DOI: 10.1016/j.lssr.2026.02.001
Language: English
Field: Medicine
Open Access status: hybrid
Estimated APC paid: $3,060
Award: THE PRIMARY RISK FACTOR LIMITING THE AMOUNT OF TIME AN ASTRONAUT CAN SPEND IN FLIGHT IS THE RISK OF CANCER INDUCTION RESULTING FROM THE UNIQUE RADIATIONS INHERENT TO THE DEEP SPACE ENVIRONMENT. ONE STRATEGY FOR MITIGATING RADIATION INDUCED CARCINOGENESIS IS TO PROVIDE BIOLOGICAL COUNTERMEASURES THAT MITIGATE RADIATION INJURY AND CANCER INDUCTION. TO DATE THE ONLY FDA APPROVED RADIOPROTECTOR IS THE FREE RADICAL SCAVENGER AMIFOSTINE; HOWEVER CONCERNS ABOUT TOXICITY AND REPORTS OF SEVERE ANAPHYLACTIC REACTIONS TO THIS DRUG PREVENT ITS USE IN SPACEFLIGHT. THEREFORE THERE IS A NEED TO DETERMINE AND VALIDATE APPROPRIATE BIOLOGICAL COUNTERMEASURES TO MITIGATE SPACE RADIATION CARCINOGENESIS THEREBY INCREASING THE AMOUNT OF TIME ASTRONAUTS CAN SAFELY SPEND IN SPACE. IN THE PROPOSED STUDIES WE WILL EVALUATE THE RADIO PROTECTIVE POTENTIAL OF GC4419 A NOVEL SUPEROXIDE DISMUTASE MIMETIC DEVELOPED BY GALERA THERAPUTICS (ST. LOUIS MO) IN MITIGATING SPACE RADIATION CARCINOGENESIS. DUE TO ITS EFFICACY IN PHASE 1 CLINICAL TRIALS AND PRE-CLINICAL DATA GENERATED BY OUR GROUP GC4419 IS CURRENTLY BEING FAST TRACKED INTO FDA PHASE II HUMAN CLINICAL TRIALS AS A RADIOPROTECTOR FOR PATIENTS UNDERGOING CHEMORADIATION THERAPY FOR THE TREATMENT OF HEAD AND NECK CANCER. NOT ONLY DOES GC4419 REDUCE THE FREQUENCY OF RADIATION INDUCED ADVERSE EFFECTS PRE-CLINICAL DATA SUGGEST IT HAS POTENT ANTI-CARCINOGENIC AND ANTI-TUMOR EFFECTS AS WELL. THEREFORE GC4419 REPRESENTS A SAFE CLINICALLY TESTED COUNTERMEASURE TO REDUCE RADIATION INJURY. IN THE PROPOSED STUDIES WE WILL EVALUATE THE EFFICACY OF GC4419 IN PREVENTING SPACE RADIATION INDUCED CARCINOGENESIS FOCUSING SPECIFICALLY ON THE LUNG AS A PRIMARY TUMOR SITE.
OpenAlex ID: W7127954840
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