Novel Tetrahedral Human Phantoms for Space Radiation Dose Assessment

Space radiation remains one of the primary hazards to spaceflight crews. The unique nature of the intravehicular radiation spectrum makes prediction of biological outcomes difficult, with computational simulation-based efforts stymied by lack of computational resources or accurate modeling capabilities. Recent advancements in both Monte Carlo simulations and computational human phantom developments have allowed for complex radiation simulations and dosimetric calculations to be performed for numerous applications. In this work, advanced tetrahedral-type human phantoms were exposed to a simulated spectrum of particles equivalent to a single days exposure in the International Space Station in Low Earth Orbit. 3D Monte Carlo techniques were used to produce and simulate the radiation spectra. Organ absorbed dose, average energy deposition, and the whole-body integral dose was determined for a male and female phantom. Results were then extrapolated for two long-term scenarios: a 6-9 month mission on the International Space Station and a 3-year mission to Mars. The whole-body integral dose for the male and female models were found to be 0.2985 +- 0.0002 mGy/day 0.3050 +- 0.0002 mGy/day, respectively, which is within 10% of recorded dose values from the International Space Station. This work presents a novel approach to assess absorbed dose from space-like radiation fields using high-fidelity computational phantoms, highlighting the utility of complex models for space radiation research.Comment: 10 pages, 3 figures, 2 table

Everything you wanted to know about space radiation but were afraid to ask

The space radiation environment is a complex combination of fast-moving ions derived from all atomic species found in the periodic table. The energy spectrum of each ion species varies widely but is prominently in the range of 400–600 MeV/n. The large dynamic range in ion energy is difficult to simulate in ground-based radiobiology experiments. Most ground-based irradiations with mono-energetic beams of a single one ion species are delivered at comparatively high dose rates. In some cases, sequences of such beams are delivered with various ion species and energies to crudely approximate the complex space radiation environment. This approximation may cause profound experimental bias in processes such as biologic repair of radiation damage, which are known to have strong temporal dependencies. It is possible that this experimental bias leads to an over-prediction of risks of radiation effects that have not been observed in the astronaut cohort. None of the primary health risks presumably attributed to space radiation exposure, such as radiation carcinogenesis, cardiovascular disease, cognitive deficits, etc., have been observed in astronaut or cosmonaut crews. This fundamentally and profoundly limits our understanding of the effects of GCR on humans and limits the development of effective radiation countermeasures

Real-Time Culture-Independent Microbial Profiling Onboard the International Space Station Using Nanopore Sequencing

For the past two decades, microbial monitoring of the International Space Station (ISS) has relied on culture-dependent methods that require return to Earth for analysis. This has a number of limitations, with the most significant being bias towards the detection of culturable organisms and the inherent delay between sample collection and ground-based analysis. In recent years, portable and easy-to-use molecular-based tools, such as Oxford Nanopore Technologies’ MinION™ sequencer and miniPCR bio’s miniPCR™ thermal cycler, have been validated onboard the ISS. Here, we report on the development, validation, and implementation of a swab-to-sequencer method that provides a culture-independent solution to real-time microbial profiling onboard the ISS. Method development focused on analysis of swabs collected in a low-biomass environment with limited facility resources and stringent controls on allowed processes and reagents. ISS-optimized procedures included enzymatic DNA extraction from a swab tip, bead-based purifications, altered buffers, and the use of miniPCR and the MinION. Validation was conducted through extensive ground-based assessments comparing current standard culture-dependent and newly developed culture-independent methods. Similar microbial distributions were observed between the two methods; however, as expected, the culture-independent data revealed microbial profiles with greater diversity. Protocol optimization and verification was established during NASA Extreme Environment Mission Operations (NEEMO) analog missions 21 and 22, respectively. Unique microbial profiles obtained from analog testing validated the swab-to-sequencer method in an extreme environment. Finally, four independent swab-to-sequencer experiments were conducted onboard the ISS by two crewmembers. Microorganisms identified from ISS swabs were consistent with historical culture-based data, and primarily consisted of commonly observed human-associated microbes. This simplified method has been streamlined for high ease-of-use for a non-trained crew to complete in an extreme environment, thereby enabling environmental and human health diagnostics in real-time as future missions take us beyond low-Earth orbit

Real-Time Culture-Independent Microbial Profiling Onboard the International Space Station Using Nanopore Sequencing

For the past two decades, microbial monitoring of the International Space Station (ISS) has relied on culture-dependent methods that require return to Earth for analysis. This has a number of limitations, with the most significant being bias towards the detection of culturable organisms and the inherent delay between sample collection and ground-based analysis. In recent years, portable and easy-to-use molecular-based tools, such as Oxford Nanopore Technologies’ MinION™ sequencer and miniPCR bio’s miniPCR™ thermal cycler, have been validated onboard the ISS. Here, we report on the development, validation, and implementation of a swab-to-sequencer method that provides a culture-independent solution to real-time microbial profiling onboard the ISS. Method development focused on analysis of swabs collected in a low-biomass environment with limited facility resources and stringent controls on allowed processes and reagents. ISS-optimized procedures included enzymatic DNA extraction from a swab tip, bead-based purifications, altered buffers, and the use of miniPCR and the MinION. Validation was conducted through extensive ground-based assessments comparing current standard culture-dependent and newly developed culture-independent methods. Similar microbial distributions were observed between the two methods; however, as expected, the culture-independent data revealed microbial profiles with greater diversity. Protocol optimization and verification was established during NASA Extreme Environment Mission Operations (NEEMO) analog missions 21 and 22, respectively. Unique microbial profiles obtained from analog testing validated the swab-to-sequencer method in an extreme environment. Finally, four independent swab-to-sequencer experiments were conducted onboard the ISS by two crewmembers. Microorganisms identified from ISS swabs were consistent with historical culture-based data, and primarily consisted of commonly observed human-associated microbes. This simplified method has been streamlined for high ease-of-use for a non-trained crew to complete in an extreme environment, thereby enabling environmental and human health diagnostics in real-time as future missions take us beyond low-Earth orbit

Specific Immunologic Countermeasure Protocol for Deep-Space Exploration Missions

Historically, serious illness of astronauts on orbit is rare, however clinical episodes requiring therapeutic intervention have occurred during International Space Station (ISS) missions at a noteworthy rate (1, 2). Persistent exposure to the space environment exacerbates perturbations to the immune system (3). In support, the NASA “twins” study—an evaluation of a crewmember during a 1-year ISS mission—revealed significant changes between in-flight and non-flight time points in the gene expression patterns of several immune response pathways, DNA methylation patterns of genes that regulate T cell responses, and the signatures of plasma cytokines, to promote during spaceflight decreased cellular responsiveness and increased inflammation (4). Because future deep-space exploration missions will endure for an unprecedented amount of time, with increased magnitude of mission-associated stressors, it is reasonable to expect a higher incidence of morbidities. Previously, we published a comprehensive review of potential countermeasures to obviate the immune “problem” associated with spaceflight. Now, we present a specific and personalized immune countermeasure prescription for prospective astronauts embarking on deep-space voyageGerman National Space Program [50WB1622]; European Space Agency (ESA)'s Topical Team Stress and Immunity - ESA ELIPS 4 program; European Space Agency (ESA)'s Topical Team Stress and Immunity - ESA SciSpacE programOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]