NASA's first ground-based Galactic Cosmic Ray Simulator: Enabling a new era in space radiobiology research.

With exciting new NASA plans for a sustainable return to the moon, astronauts will once again leave Earth's protective magnetosphere only to endure higher levels of radiation from galactic cosmic radiation (GCR) and the possibility of a large solar particle event (SPE). Gateway, lunar landers, and surface habitats will be designed to protect crew against SPEs with vehicle optimization, storm shelter concepts, and/or active dosimetry; however, the ever penetrating GCR will continue to pose the most significant health risks especially as lunar missions increase in duration and as NASA sets its aspirations on Mars. The primary risks of concern include carcinogenesis, central nervous system (CNS) effects resulting in potential in-mission cognitive or behavioral impairment and/or late neurological disorders, degenerative tissue effects including circulatory and heart disease, as well as potential immune system decrements impacting multiple aspects of crew health. Characterization and mitigation of these risks requires a significant reduction in the large biological uncertainties of chronic (low-dose rate) heavy-ion exposures and the validation of countermeasures in a relevant space environment. Historically, most research on understanding space radiation-induced health risks has been performed using acute exposures of monoenergetic single-ion beams. However, the space radiation environment consists of a wide variety of ion species over a broad energy range. Using the fast beam switching and controls systems technology recently developed at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory, a new era in radiobiological research is possible. NASA has developed the "GCR Simulator" to generate a spectrum of ion beams that approximates the primary and secondary GCR field experienced at human organ locations within a deep-space vehicle. The majority of the dose is delivered from protons (approximately 65%-75%) and helium ions (approximately 10%-20%) with heavier ions (Z ≥ 3) contributing the remainder. The GCR simulator exposes state-of-the art cellular and animal model systems to 33 sequential beams including 4 proton energies plus degrader, 4 helium energies plus degrader, and the 5 heavy ions of C, O, Si, Ti, and Fe. A polyethylene degrader system is used with the 100 MeV/n H and He beams to provide a nearly continuous distribution of low-energy particles. A 500 mGy exposure, delivering doses from each of the 33 beams, requires approximately 75 minutes. To more closely simulate the low-dose rates found in space, sequential field exposures can be divided into daily fractions over 2 to 6 weeks, with individual beam fractions as low as 0.1 to 0.2 mGy. In the large beam configuration (60 × 60 cm2), 54 special housing cages can accommodate 2 to 3 mice each for an approximately 75 min duration or 15 individually housed rats. On June 15, 2018, the NSRL made a significant achievement by completing the first operational run using the new GCR simulator. This paper discusses NASA's innovative technology solution for a ground-based GCR simulator at the NSRL to accelerate our understanding and mitigation of health risks faced by astronauts. Ultimately, the GCR simulator will require validation across multiple radiogenic risks, endpoints, doses, and dose rates.

Metabolic oxygen consumption measurement with a single-cell biosensor after particle microbeam irradiation.

A noninvasive, self-referencing biosensor/probe system has been integrated into the Columbia University Radiological Research Accelerator Facility Microbeam II end station. A single-cell oxygen consumption measurement has been conducted with this type of oxygen probe in 37° C Krebs-Ringer Bicarbonate buffer immediately before and after a single-cell microbeam irradiation. It is the first such measurement made for a microbeam irradiation, and a six fold increment of oxygen flux induced during a 15-s period of time has been observed following radiation exposure. The experimental procedure and the results are discussed.

Simulation study of delivery of subnanosecond pulses to biological tissues with an impulse radiating antenna.

We have numerically studied the delivery of subnanosecond pulsed radiation to biological tissues for bioelectric applications. The antenna fed by 200 ps pulses uses an elliptical reflector in conjunction with a dielectric lens. Two numerical targets were studied: one was a hemispherical tissue with a resistivity of 0.3-1 S/m and a relative permittivity of 9-70 and the other was a realistic human head model (HUGO). The electromagnetic simulation shows that despite tissue heterogeneity of the human head, the electric field converges to a spot 8 cm in depth and the spot volume is approximately 1 cm × 2 cm × 1 cm in both cases when using only the reflector and a lens as an addition. Rather than increasing as it approaches the converging point, the electric field decreases strongly with distance from the skin to the converging point due to tissue resistive loss. The electric field distribution, however, can be reversed by making the dielectric lens lossy with the two innermost layers being partially resistive. The lossy lens causes an attenuation of the electric field near the axis, but the electric field generated by the waves which pass the lens at a wider angles compensate for this loss. A local maximum electric field in a deeper region of the tissue may form with the lossy lens. The study shows that it is possible to generate the desired electric field distribution in the complex biological target by modifying the dielectric properties of the lens used in conjunction with the reflector antenna.

"Broadbeam" irradiation of mammalian cells using a vertical microbeam facility.

A "broadbeam" facility is demonstrated for the vertical microbeam at Surrey's Ion Beam Centre, validating the new technique used by Barazzuol et al. (Radiat Res 177:651-662, 2012). Here, droplets with a diameter of about 4 mm of 15,000 mammalian cells in suspension were pipetted onto defined locations on a 42-mm-diameter cell dish with each droplet individually irradiated in "broadbeam" mode with 2 MeV protons and 4 MeV alpha particles and assayed for clonogenicity. This method enables multiple experimental data points to be rapidly collected from the same cell dish. Initially, the Surrey vertical beamline was designed for the targeted irradiation of single cells with single counted ions. Here, the benefits of both targeted single-cell and broadbeam irradiations being available at the same facility are discussed: in particular, high-throughput cell irradiation experiments can be conducted on the same system as time-intensive focused-beam experiments with the added benefits of fluorescent microscopy, cell recognition and time-lapse capabilities. The limitations of the system based on a 2 MV tandem accelerator are also discussed, including the uncertainties associated with particle Poisson counting statistics, spread of linear energy transfer in the nucleus and a timed dose delivery. These uncertainties are calculated with Monte Carlo methods. An analysis of how this uncertainty affects relative biological effect measurements is made and discussed.

UV microspot irradiator at Columbia University.

The Radiological Research Accelerator Facility at Columbia University has recently added a UV microspot irradiator to a microbeam irradiation platform. This UV microspot irradiator applies multiphoton excitation at the focal point of an incident laser as the source for cell damage, and with this approach, a single cell within a 3D sample can be targeted and exposed to damaging UV. The UV microspot's ability to impart cellular damage within 3D is an advantage over all other microbeam techniques, which instead impart damage to numerous cells along microbeam tracks. This short communication is an overview, and a description of the UV microspot including the following applications and demonstrations of selective damage to live single cell targets: DNA damage foci formation, patterned irradiation, photoactivation, targeting of mitochondria, and targeting of individual cardiomyocytes in a live zebrafish embryo.

Optimisation of exposure conditions for in vitro radiobiology experiments.

Despite the long history of using cell cultures in vitro for radiobiological studies, there is to date no study specifically addressing the dosimetric implications of flask selection and exposure environment in clonogenic assays. The consequent variability in dosimetry between laboratories impedes the comparison of results. In this study we compare the dose to cells adherent to the base of three types of commonly used culture flasks or plates. The cells are exposed to a 6MV clinical photon beam using either an open or a half blocked field. The depth of medium in each flask is varied with the medium surrounding the flask either water or air. The results show that the dose to the cells is more affected by the scattering conditions surrounding the flasks than by the level of filling within the flask. It is recommended that water or a water equivalent phantom material is used to surround the flasks or plates to approximate full scatter conditions at the cell layer. However for modulated fields, surrounding the 24 well plates with water-equivalent material is inadequate because of the large volume of air surrounding individual wells. Our results stress the importance of measuring the dose for new experimental configurations.

[Gamma knife radiosurgery]. / La radiochirurgie par Gamma Knife.

Gamma Knife radiosurgery can be used as an alternative or complementary therapy to neurosurgery or radiotherapy for the treatment of some brain disorders or tumors of small volume. The most frequent indications are brain metastases, vestibular schwannomas, meningiomas, trigeminal neuralgia, arteriovenous malformations, some gliomas, and pituitary adenomas. Created in 1999, the Gamma Knife Center of the ULB remains currently the unique center in Belgium where a Gamma Knife radiosurgery treatment can be performed.

A new platform for ultra-high dose rate radiobiological research using the BELLA PW laser proton beamline.

Radiotherapy is the current standard of care for more than 50% of all cancer patients. Improvements in radiotherapy (RT) technology have increased tumor targeting and normal tissue sparing. Radiations at ultra-high dose rates required for FLASH-RT effects have sparked interest in potentially providing additional differential therapeutic benefits. We present a new experimental platform that is the first one to deliver petawatt laser-driven proton pulses of 2 MeV energy at 0.2 Hz repetition rate by means of a compact, tunable active plasma lens beamline to biological samples. Cell monolayers grown over a 10 mm diameter field were exposed to clinically relevant proton doses ranging from 7 to 35 Gy at ultra-high instantaneous dose rates of 107 Gy/s. Dose-dependent cell survival measurements of human normal and tumor cells exposed to LD protons showed significantly higher cell survival of normal-cells compared to tumor-cells for total doses of 7 Gy and higher, which was not observed to the same extent for X-ray reference irradiations at clinical dose rates. These findings provide preliminary evidence that compact LD proton sources enable a new and promising platform for investigating the physical, chemical and biological mechanisms underlying the FLASH effect.

Heavy charged particle radiobiology: using enhanced biological effectiveness and improved beam focusing to advance cancer therapy.

Ionizing radiation causes many types of DNA damage, including base damage and single- and double-strand breaks. Photons, including X-rays and γ-rays, are the most widely used type of ionizing radiation in radiobiology experiments, and in radiation cancer therapy. Charged particles, including protons and carbon ions, are seeing increased use as an alternative therapeutic modality. Although the facilities needed to produce high energy charged particle beams are more costly than photon facilities, particle therapy has shown improved cancer survival rates, reflecting more highly focused dose distributions and more severe DNA damage to tumor cells. Despite early successes of charged particle radiotherapy, there is room for further improvement, and much remains to be learned about normal and cancer cell responses to charged particle radiation.

Rescue effects in radiobiology: unirradiated bystander cells assist irradiated cells through intercellular signal feedback.

Mammalian cells respond to ionization radiation by sending out extracellular signals to affect non-irradiated neighboring cells, which is referred to as radiation induced bystander effect. In the present paper, we described a phenomenon entitled the "rescue effects", where the bystander cells rescued the irradiated cells through intercellular signal feedback. The effect was observed in both human primary fibroblast (NHLF) and cancer cells (HeLa) using two-cell co-culture systems. After co-culturing irradiated cells with unirradiated bystander cells for 24h, the numbers of 53BP1 foci, corresponding to the number of DNA double-strand breaks in the irradiated cells were less than those in the irradiated cells that were not co-cultured with the bystander cells (0.78±0.04foci/cell vs. 0.90±0.04foci/cell) at a statistically significant level. Similarly, both micronucleus formation and extent of apoptosis in the irradiated cells were different at statistically significant levels if they were co-cultured with the bystander cells. Furthermore, it was found that unirradiated normal cells would also reduce the micronucleus formation in irradiated cancer cells. These results suggested that the rescue effects could participate in repairing the radiation-induced DNA damages through a media-mediated signaling feedback, thereby mitigating the cytotoxicity and genotoxicity of ionizing radiation.

Current progress of the biological single-ion microbeam at FUDAN.

A biological microbeam for precisely positioned single-ion/single cell irradiation is built in the Institute of Modern Physics in Fudan University, Shanghai, China, based on the tandem accelerator (2 × 3MV) in the laboratory. In this paper, the developing progress of the FUDAN microbeam is reported, including the newly constructed beam line, the microbeam collimator, the ion detection system, and the cell-imaging and targeting systems. Statistical models are proposed for evaluating the spatial resolution and dosage precision of the microbeam. By taking the collimated ions as a Gaussian beam, the spatial resolution can be evaluated by the full width at half maximum of the 2-D Gaussian distribution, which is determined by fitting the proportions of peripheral pits outside specific radii in the pit clusters etched on ion track detectors to a 2-D Gaussian distribution. In the preset hitting of defined ion number, by taking the real delivered number of ions as an independent identically distributed random variable (iidrv), according to the Law of Large Numbers and Central Limit Theorem, the expected value µ and standard deviation σ of the real delivered ion number in a preset N-ion hitting can be determined by approaching the normal distribution of N (µ, σ (2)/n) with the proportions of the mean counts of pits in multiple pit clusters on ion track detectors. By the values of µ, σ and additional assumptions, statistical dosage precision evaluations can be made on the preset hitting. From the linear fit curve of µ(N) and the power function fit curve of σ(N) on different preset ion numbers, characteristic factors k, b, A, p can be extracted for a precision evaluation independent of the specific preset ion number.

New challenges in radiobiology research with microbeams.

There is a continuing interest in the use of microbeam systems designed to deliver ionizing radiation (both photons and particles) with a resolution of a few micrometers or less in biological targets. With more than 30 facilities currently in operation, several new research topics can be explored. In the 9th International Microbeam Workshop held in Darmstadt, Germany, in July 2010, several new ideas and results have been presented, indicating that microbeams will be increasingly important in radiobiology. Subnuclear targeting of single cells for DNA repair studies and microirradiation of 3D or small animal models are among the most promising new research perspectives.

Characterization of a custom-made 241Am alpha-source for radiobiological studies.

A compact in-house alpha particle source has been developed and fully characterized. The irradiation source is a large area, 25 cm2, 5.4 MeV average energy 241Am source, above which a Mylar dish containing a monolayer of target cells can be placed at defined positions. The source uniformity, flux, particle energy and dose rate were determined experimentally. The dose rate to the nucleus at the closest position was 1.57 Gy/min. Furthermore, a 3D printed collimator was tested and found to improve the uniformity of the energy spectra of particles reaching the target. For validation, prostate PC-3 cells were irradiated in our experimental setup with absorbed doses up to 2 Gy and for reference compared with cells irradiated with conventional X-rays with doses up to 8 Gy. The Relative Biological Effectiveness for alpha particles at 10% survival was 3.66± 0.40 agreeing with previously published data. Data presented here show the feasibility of utilising a low-cost alpha-irradiation source for accurate in vitro assays to better understand the radiobiological effects of high LET alpha particles.

Space radiation research in Europe: flight experiments and ground-based studies.

Exposure to space radiation has long been acknowledged as a potential showstopper for long-duration manned interplanetary missions. In an effort to gain more information on space radiation risk and to develop countermeasures, NASA initiated several years ago a Space Radiation Health Program, which is currently supporting biological experiments performed at the Brookhaven National Laboratory. Accelerator-based radiobiology research in the field of space radiation research is also under way in Russia and Japan. The European Space Agency (ESA) supports research in the field in three main directions: spaceflight experiments on the International Space Station; modeling and simulations of the space radiation environment and transport; and, recently, ground-based radiobiology experiments exploiting the high-energy SIS18 synchrotron at GSI in Germany (IBER program). Several experiments are currently under way within IBER, and so far, beams of C and Fe-ions at energies between 11 and 1,000 MeV/n have been used in cell and tissue targets.

STATE INSTITUTION «NATIONAL RESEARCH CENTER FOR RADIATION MEDICINE OF THE NATIONAL ACADEMY OF MEDICAL SCIENCES OF UKRAINE¼ - RESEARCH ACTIVITIES AND SCIENTIFIC ADVANCE IN 2019. / REZUL'TATY ROBOTY DU «NATsIONAL'NYI NAUKOVYI TsENTR RADIATsIINOÏ MEDYTsYNY AKADEMIÏ MEDYChNYKh NAUK UKRAÏNY¼ U 2019 ROTsI.

Research activities and scientific advance achieved in 2019 at the State Institution «National Research Center forRadiation Medicine of the National Academy of Medical Sciences of Ukraine¼ (NRCRM) concerning medical problemsof the Chornobyl disaster, radiation medicine, radiobiology, radiation hygiene and epidemiology in collaborationwith the WHO network of medical preparedness and assistance in radiation accidents are outlined in the annualreport. The report presents the results of fundamental and applied research works of the study of radiation effectsand health effects of the Chornobyl accident.The report also shows the results of scientific-organizational and health care work, staff training.The Scientific Council meeting of NAMS approved the NRCRM Annual Report.

Ionizing radiation microbeam facilities for radiobiological studies in Europe.

A growing body of experimental evidence gathered in the last 10-15 years with regard to targeted and non-targeted effects of low doses of ionizing radiation (hyper-radiosensitivity, induced radio-resistance, adaptive response, genomic instability, bystander effects) has pushed the radiobiology research towards a better understanding of the mechanisms underlying these phenomena, the extent to which they are active in-vivo, and how they are inter-related. In such a way factors could be obtained and included in the estimation of potential cancer risk to the human population of exposure to low levels of ionizing radiation. Different experimental approaches have been developed and employed to study such effects in-vitro (medium transfer experiments; broad-field irradiation at low doses also with insert or shielding systems...). In this regard, important contributions came from ionizing radiation microbeam facilities that turn to be powerful tools to perform selective irradiations of individual cells inside a population with an exact, defined and reproducible dose (i.e. number of particles, in case of charged particle microbeams). Over the last 20 years the use of microbeams for radiobiological applications increased substantially and a continuously growing number of such facilities, providing X-rays, electrons, light and heavy ions, has been developing all over the world. Nowadays, just in Europe there are 12 microbeam facilities fully-operational or under-development, out of more than 30 worldwide. An overview of the European microbeam facilities for radiobiological studies is presented and discussed in this paper.

Microbeam studies of the bystander response.

Microbeams have undergone a renaissance since their introduction and early use in the mid 60s. Recent advances in imaging, software and beam delivery have allowed rapid technological developments in microbeams for use in a range of experimental studies. The resurgence in the use of microbeams since the mid 90s has coincided with major changes in our understanding of how radiation interacts with cells. In particular, the evidence that bystander responses occur, where cells not directly irradiated can respond to irradiated neighbours, has brought about the evolution of new models of radiation response. Although these processes have been studied using a range of experimental approaches, microbeams offer a unique route by which bystander responses can be elucidated. Without exception, all of the microbeams currently active internationally have studied bystander responses in a range of cell and tissue models. Together these studies have considerably advanced our knowledge of bystander responses and the underpinning mechanisms. Much of this has come from charged particle microbeam studies, but increasingly, X-ray and electron microbeams are starting to contribute quantitative and mechanistic information on bystander effects. A recent development has been the move from studies with 2-D cell culture models to more complex 3-D systems where the possibilities of utilizing the unique characteristics of microbeams in terms of their spatial and temporal delivery will make a major impact.

Microbeam irradiation facilities for radiobiology in Japan and China.

In order to study the radiobiological effects of low dose radiation, microbeam irradiation facilities have been developed in the world. This type of facilities now becomes an essential tool for studying bystander effects and relating signaling phenomena in cells or tissues. This review introduces you available microbeam facilities in Japan and in China, to promote radiobiology using microbeam probe and to encourage collaborative research between radiobiologists interested in using microbeam in Japan and in China.

Expanding the question-answering potential of single-cell microbeams at RARAF, USA.

Charged-particle microbeams, developed to provide targeted irradiation of individual cells, and then of sub-cellular components, and then of 3-D tissues and now organisms, have been instrumental in challenging and changing long accepted paradigms of radiation action. However the potential of these valuable tools can be enhanced by integrating additional components with the direct ability to measure biological responses in real time, or to manipulate the cell, tissue or organism of interest under conditions where information gained can be optimized. The RARAF microbeam has recently undergone an accelerator upgrade, and been modified to allow for multiple microbeam irradiation laboratories. Researchers with divergent interests have expressed desires for particular modalities to be made available and ongoing developments reflect these desires. The focus of this review is on the design, incorporation and use of multiphoton and other imaging, micro-manipulation and single cell biosensor capabilities at RARAF. Additionally, an update on the status of the other biology oriented microbeams in the Americas is provided.

Applications of particle microbeams in space radiation research.

Galactic cosmic radiation is acknowledged as one of the major barriers to human space exploration. In space, astronauts are exposed to charged particles from Z = 1 (H) up to Z = 28 (Ni), but the probability of a hit to a specific single cell in the human body is low. Particle microbeams can deliver single charged particles of different charge and energy to single cells from different tissues, and microbeam studies are therefore very useful for improving current risk estimates for long-term space travel. 2D in vitro cell cultures can be very useful for establishing basic molecular mechanisms, but they are not sufficient to extrapolate risk, given the substantial evidence proving tissue effects are key in determining the response to radiation insult. 3D tissue or animal systems represent a more promising target for space radiobiology using microbeams.