Quantifying the effects of neutron dose, dose protraction, age and sex on mouse survival using parametric regression and machine learning on a 21,000-mouse data set

The biological effects of densely-ionizing radiations such as neutrons and heavy ions encountered in space travel, nuclear incidents, and cancer radiotherapy, significantly differ from those of sparsely-ionizing photons and necessitate a comprehensive understanding for improved protection measures. Data on lifespan studies of laboratory rodents exposed to fission neutrons, accumulated in the Janus archive, afford unique insights into the impact of densely ionizing radiation on mortality from cancers and various organ dysfunction. We extracted and analyzed data for 21,308 individual B6CF1 mice to investigate the effects of neutron dose, fractionation, protraction, age, and sex on mortality. As Cox regression encountered limitations owing to assumption violations, we turned to Random Survival Forests (RSF), a machine learning algorithm adept at modeling nonlinear relationships. RSF interpretation using Shapley Additive Explanations revealed a dose response for mortality risk that curved upwards at low doses < 20 cGy, became nearly-linear over 20-150 cGy, and saturated at high doses. The response was enhanced by fractionation/protraction of irradiation (exhibiting an inverse dose rate effect), and diminished by older age at exposure. Somewhat reduced mortality was predicted for males vs females. This research expands our knowledge on the long-term effects of densely ionizing radiations on mammal mortality.

Review of nanomaterial advances for ionizing radiation dosimetry

There are a wide range of applications with ionizing radiation and a common theme throughout these is that accurate dosimetry is usually required, although many newer demands are provided by improved features in higher range, multi-spectral and particle type detected. Today, the array of dosimeters includes both offline and online tools, such as gel dosimeters, thermoluminescence (TL), scintillators, optically stimulated luminescence (OSL), radiochromic polymeric films, gels, ionization chambers, colorimetry, and electron spin resonance (ESR) measurement systems. Several future nanocomposite features and interpretation of their substantial behaviors are discussed that can lead to improvements in specific features, such as (1) lower sensitivity range, (2) less saturation at high range, (3) overall increased dynamic range, (4) superior linearity, (5) linear energy transfer and energy independence, (6) lower cost, (7) higher ease of use, and (8) improved tissue equivalence. Nanophase versions of TL and ESR dosimeters and scintillators each have potential for higher range of linearity, sometimes due to superior charge transfer to the trapping center. Both OSL and ESR detection of nanomaterials can have increased dose sensitivity because of their higher readout sensitivity with nanoscale sensing. New nanocrystalline scintillators, such as perovskite, have fundamentally important advantages in sensitivity and purposeful design for key new applications. Nanoparticle plasmon coupled sensors doped within a lower Zeff material have been an effective way to achieve enhanced sensitivity of many dosimetry systems while still achieving tissue equivalency. These nanomaterial processing techniques and unique combinations of them are key steps that lead to the advanced features. Each must be realized through industrial production and quality control with packaging into dosimetry systems that maximize stability and reproducibility. Ultimately, recommendations for future work in this field of radiation dosimetry were summarized throughout the review.

Machine intelligence for radiation science: summary of the Radiation Research Society 67th annual meeting symposium

The era of high-throughput techniques created big data in the medical field and research disciplines. Machine intelligence (MI) approaches can overcome critical limitations on how those large-scale data sets are processed, analyzed, and interpreted. The 67^th Annual Meeting of the Radiation Research Society featured a symposium on MI approaches to highlight recent advancements in the radiation sciences and their clinical applications. This article summarizes three of those presentations regarding recent developments for metadata processing and ontological formalization, data mining for radiation outcomes in pediatric oncology, and imaging in lung cancer.

Findings from international archived data: Fractionation reduces mortality risk of ionizing radiation for total doses below 4 Gray in rodents

Ionizing radiation is omnipresent and unavoidable on Earth; nevertheless, the range of doses and modes of radiation delivery that represent health risks remain controversial. Radiation protection policy for civilians in US is set at 1 mSv per year. Average persons from contemporary populations are exposed to several hundred milliSieverts (mSv) over their lifetimes from both natural and human made sources such as radon, cosmic rays, CT-scans (20-50 mSv partial body exposure per scan), etc. Health risks associated with these and larger exposures are focus of many epidemiological studies, but uncertainties of these estimates coupled with individual and environmental variation make it is prudent to attempt to use animal models and tightly controlled experimental conditions to supplement our evaluation of radiation risk question. Data on 11,528 of rodents of both genders exposed to x-ray or gamma-ray radiation in facilities in US and Europe were used for this analysis; animal mortality data argue that fractionated radiation exposures have about 2 fold less risk per Gray than acute radiation exposures in the range of doses between 0.25 and 4 Gy.

Omics in Radiation Biology: Surprised but Not Disappointed

High-throughput omics platforms have pioneered our approach to understanding biological and cellular processes. Omics technologies provide powerful tools for studying various molecules, such as genes, proteins, and metabolites, in a particular state and at a particular time. Although omics has had a presence in the radiation community for more than 3 decades, the use of it is still in its infancy. Omics studies enable radiation researchers to understand the molecular mechanism underlying the biological effects of radiation exposure on normal and cancerous tissues, and to answer critical questions such as individual sensitivity, risk assessment, and biomarker discovery. In this commentary, we take a look back at the omics studies that have been conducted in radiation research in the last 20 years and discuss whether omics has fulfilled expectations by examining the knowledge and research gaps in radiation omics.

Effects of low dose and low dose rate low linear energy transfer radiation on animals - review of recent studies relevant for carcinogenesis

Purpose: Carcinogenic effects of radiation are often assumed to be universally understood, more often than, for example, carcinogenic effects of many different chemicals. This in turn leads to an assumption that any dose of radiation, delivered at any dose rate, poses a serious health challenge. This remains an issue of dispute and low dose radiation research is focused on understanding whether these exposures contribute to cancer incidence. This review is focused on the low linear energy transfer (low LET) radiation exposures for which the data is the most abundant in recent years. Materials and methods: Review of the literature between 2008 and today, highlighting some of the most diverse studies in low dose research. Results: Low dose and low dose rate, low LET ionizing radiation animal studies suggest that the effects of exposure very much depend on animal genotype and health status.Conclusions: Only the integration of all of the data from different models and studies will lead to a fuller understanding of low dose radiation effects. Therefore, we hope to see an increase in international archival efforts and exchange of raw data information opening the possibilities for new types of meta analyses.

SURVEY ON DATA MANAGEMENT IN RADIATION PROTECTION RESEARCH

The importance of datasharing is of increasing concern to funding bodies and institutions. With some prescience, the radiobiology community has established datasharing infrastructures over the last two decades, including STORE; however, the utilization of these databases is disappointing. The aim of the present study was to identify the current state of datasharing amongst researchers in radiation protection, and to identify barriers to effective sharing. An electronic survey was prepared, including questions on post-publication data provision, institutional, funding agency, and journal policies, awareness of datasharing infrastructures, attitudinal barriers and technical support. The survey was sent to the members of a mailing list maintained by the EC funded CONCERT project. Responses identified that the radiation protection community shared similar concerns to other groups canvassed in earlier studies; the perceived negative impact of datasharing on competitiveness, career development and reputation, along with concern about the costs of data management. More surprising was the lack of awareness of existing datasharing platforms. We find that there is a clear need for education and training in data management and for a significant programme of improving awareness of Open Data issues.

Radiation databases and archives - examples and comparisons

Studies of ionizing radiation effects through the archiving of data began with standardizing medical treatments in the early 1900s shortly after the discovery of X-rays. Once the breadth of the delayed effects of ionizing radiation was recognized, the need for long-term follow up became apparent. There are now many human archives of data from nuclear disasters and accidents, occupational exposures, and medical procedures. Planned animal irradiation experiments began around the time of the Cold War and included a variety of doses, fractions, dose rates, and types of ionizing radiation. The goal of most of these studies was to supplement information coming from human data through carefully planned experimental conditions and immediate and uninterrupted data collection. This review aims to highlight major archives and databases that have shaped the field of radiation biology and provide a broad range of the types of datasets currently available. By preserving all of these data and tissue sets, radiation biologists can combine databases and conduct large-scale analyses of detailed existing data and perform new assays with cutting edge scientific approaches.

Typical doses and dose rates in studies pertinent to radiation risk inference at low doses and low dose rates

In order to quantify radiation risks at exposure scenarios relevant for radiation protection, often extrapolation of data obtained at high doses and high dose rates down to low doses and low dose rates is needed. Task Group TG91 on 'Radiation Risk Inference at Low-dose and Low-dose Rate Exposure for Radiological Protection Purposes' of the International Commission on Radiological Protection is currently reviewing the relevant cellular, animal and human studies that could be used for that purpose. This paper provides an overview of dose rates and doses typically used or present in those studies, and compares them with doses and dose rates typical of those received by the A-bomb survivors in Japan.

Lower thresholds for lifetime health effects in mammals from high-LET radiation - Comparison with chronic low-LET radiation

Lower threshold dose rates and confidence limits are quantified for lifetime radiation effects in mammalian animals from internally deposited alpha-emitting radionuclides. Extensive datasets on effects from internal alpha-emitters are compiled from the International Radiobiological Archives. In total, the compiled database includes 257 records, which are analyzed by means of non-parametric order statistics. The generic lower threshold for alpha-emitters in mammalian animals (combined datasets) is 6.6·10^-5 Gy day^-1. Thresholds for individual alpha-emitting elements differ considerably: plutonium and americium - 2.0·10^-5 Gy day^-1; radium - 2.1·10^-4 Gy day^-1. Threshold for chronic low-LET radiation is previously estimated at 1·10^-3 Gy day^-1. For low exposures, the following values of alpha radiation weighting factor w_R for internally deposited alpha-emitters in mammals are quantified: w_R(α) = 15 as a generic value for the whole group of alpha-emitters; w_R(Pu) = 50 for plutonium; w_R(Am) = 50 for americium; w_R(Ra) = 5 for radium. These values are proposed to serve as radiation weighting factors in calculations of equivalent doses to non-human biota. The lower threshold dose rate for long-lived mammals (dogs) is significantly lower than comparing with the threshold for short-lived mammals (mice): 2.7·10^-5 Gy day^-1, and 2.0·10^-4 Gy day^-1, respectively. The difference in thresholds is exactly reflecting the relationship between the natural longevity of these two species. Graded scale of severity in lifetime radiation effects in mammals is developed, based on compiled datasets. Being placed on the severity scale, the effects of internal alpha-emitters are situated in the zones of considerably lower dose rates than effects of the same severity caused by low-LET radiation. RBE values, calculated for effects of equal severity, are found to depend on the intensity of chronic exposure: different RBE values are characteristic for low, moderate, and high lifetime exposures (30, 70, and 13, respectively). The results of the study provide a basis for selecting correct values of radiation weighting factors in dose assessment to non-human biota.

The German Thorotrast Cohort Study: a review and how to get access to the data

It is well known that exposures like those from (226)Ra, (224)Ra and Thorotrast(®) injections increase the risk of neoplasia in bone marrow and liver. The thorium-based radioactive contrast agent Thorotrast(®) was introduced in 1929 and applied worldwide until the 1950s, especially in angiography and arteriography. Due to the extremely long half-life of several hundred years and the life-long retention of the thorium dioxide particles in the human body, patients suffer lifetime internal exposure. The health effects from the incorporated thorium were investigated in a few cohort studies with a German study being the largest among them. This retrospective cohort study was set up in 1968 with a follow-up until 2004. The study comprises 2326 Thorotrast patients and 1890 patients of a matched control group. For those being alive at the start of the study in 1968 follow-up was done by clinical examinations on a biannual basis. For the others, causes of death were collected in various ways. Additionally, clinical, radiological and biophysical studies of patients were conducted and large efforts were made to best estimate the radiation doses associated with incorporation of the Thorotrast. The aim of this paper is to describe the cohort, important results and some open questions. The data from the German Thorotrast Study are available to other interested researchers. Information can be found at http://storedb.org .

Dose-rate effects in radiation biology and radiation protection

Quantification of biological effects (cancer, other diseases, and cell damage) associated with exposure to ionising radiation has been a major issue for the International Commission on Radiological Protection (ICRP) since its foundation in 1928. While there is a wealth of information on the effects on human health for whole-body doses above approximately 100 mGy, the effects associated with doses below 100 mGy are still being investigated and debated intensively. The current radiological protection approach, proposed by ICRP for workers and the public, is largely based on risks obtained from high-dose and high-dose-rate studies, such as the Japanese Life Span Study on atomic bomb survivors. The risk coefficients obtained from these studies can be reduced by the dose and dose-rate effectiveness factor (DDREF) to account for the assumed lower effectiveness of low-dose and low-dose-rate exposures. The 2007 ICRP Recommendations continue to propose a value of 2 for DDREF, while other international organisations suggest either application of different values or abandonment of the factor. This paper summarises the current status of discussions, and highlights issues that are relevant to reassessing the magnitude and application of DDREF.

Low Dose Effects: Benefit or Harm?

This forum article discusses issues related to the effects of low dose radiation, an area that is under intense study but difficult to assess. Experiments with large-scale animal studies are included in this paper; these studies point to the need for international consortia to examine and balance the results of these large-scale studies and databases.

Dose and dose-rate effects of ionizing radiation: a discussion in the light of radiological protection

The biological effects on humans of low-dose and low-dose-rate exposures to ionizing radiation have always been of major interest. The most recent concept as suggested by the International Commission on Radiological Protection (ICRP) is to extrapolate existing epidemiological data at high doses and dose rates down to low doses and low dose rates relevant to radiological protection, using the so-called dose and dose-rate effectiveness factor (DDREF). The present paper summarizes what was presented and discussed by experts from ICRP and Japan at a dedicated workshop on this topic held in May 2015 in Kyoto, Japan. This paper describes the historical development of the DDREF concept in light of emerging scientific evidence on dose and dose-rate effects, summarizes the conclusions recently drawn by a number of international organizations (e.g., BEIR VII, ICRP, SSK, UNSCEAR, and WHO), mentions current scientific efforts to obtain more data on low-dose and low-dose-rate effects at molecular, cellular, animal and human levels, and discusses future options that could be useful to improve and optimize the DDREF concept for the purpose of radiological protection.

The European Radiobiological Archives: online access to data from radiobiological experiments is available now

The European Radiobiological Archive can be accessed at no cost at https://era.bfs.de. The necessary ID and password can be obtained from the curators at era@bfs.de.