Local bone-marrow exposure: how to interpret the data on stable chromosome aberrations in circulating lymphocytes? (some comments on the use of FISH method for dose reconstruction for Techa riverside Residents)

FISH unveils a unified method for multi-marker biodose assessment

Accurate dose assessment following radiation disasters or accidents is crucial for informed medical interventions. Cytogenetic biomarkers, such as dicentrics (dic), translocations, and chromosomal fragments, are essential for radiation biodosimetry in various exposure scenarios. However, quantifying these markers via separate staining and detection methods presents challenges in terms of efficiency and consistency. This study aimed to quantify multiple cytogenetic markers, including dic, balanced and unbalanced translocations and acentric fragments, from the same metaphases via fluorescence in situ hybridization (FISH). By enabling multimarker dose estimation from a single sample, this approach minimizes interexperimental variation and improves overall accuracy. Independent calibration curves were generated for each marker, enabling precise dose estimation with smaller class intervals, in accordance with the IAEA and ISO guidelines. The method was validated by estimating doses for five blinded samples via both standard cytogenetic methods and protein biomarkers (γH2AX and 53BP1). The multimarker approach yielded the closest estimates with 2-7% variation from true doses, providing the most accurate results among all cytogenetic techniques. This unified FISH-based approach enhances the precision of dose estimation for both recent and past radiation exposures, offering a more reliable tool for diverse biodosimetry applications.

Model of age-dependent dynamics and biokinetics of T-cells as natural biodosimeters

Circulating T-lymphocytes are used as "natural biodosimeters" for estimating radiation doses, since the frequency of chromosomal aberrations induced in them is proportional to the accumulated dose. Moreover, stable chromosomal aberrations (translocations) are detected years and decades after exposure. Internal incorporation of radionuclides often leads to non-uniform exposure, which resulted in difficulties in the application of retrospective biodosimetry using T-lymphocytes. Some properties of T-lymphocytes complicate retrospective biodosimetry in this case: (1) the thymic production of T-cells depends significantly on age, the maximum is observed in early childhood; (2) the "lymphocyte-dosimeter" accumulates changes (translocations) while circulating through the body. The objective of this paper is to describe the technical characteristics of the model of age dynamics and T-cell biokinetics and approaches to assessing the dose to circulating lymphocytes under various exposure scenarios. The model allows to quantify the fractions of T-lymphocytes that were formed before and after exposure. The model takes into account the time fractions that circulating lymphocytes spend in various lymphoid organs. Age-related thymic involution was also considered. The model predicts that after internal exposure to 90Sr, the doses to T-lymphocytes can differ significantly from the doses to the bone marrow and other tissues. For uniform external γ-exposure, and for internal exposure due to non-bone -seeking radionuclides (for example, 144Ce), predicted doses to T-lymphocytes are very close to bone marrow doses. The model allows to quantify the correction factors for FISH-based doses to obtain doses to organs and tissues.

Eurados review of retrospective dosimetry techniques for internal exposures to ionising radiation and their applications

This work presents an overview of the applications of retrospective dosimetry techniques in case of incorporation of radionuclides. The fact that internal exposures are characterized by a spatially inhomogeneous irradiation of the body, which is potentially prolonged over large periods and variable over time, is particularly problematic for biological and electron paramagnetic resonance (EPR) dosimetry methods when compared with external exposures. The paper gives initially specific information about internal dosimetry methods, the most common cytogenetic techniques used in biological dosimetry and EPR dosimetry applied to tooth enamel. Based on real-case scenarios, dose estimates obtained from bioassay data as well as with biological and/or EPR dosimetry are compared and critically discussed. In most of the scenarios presented, concomitant external exposures were responsible for the greater portion of the received dose. As no assay is available which can discriminate between radiation of different types and different LETs on the basis of the type of damage induced, it is not possible to infer from these studies specific conclusions valid for incorporated radionuclides alone. The biological dosimetry assays and EPR techniques proved to be most applicable in cases when the radionuclides are almost homogeneously distributed in the body. No compelling evidence was obtained in other cases of extremely inhomogeneous distribution. Retrospective dosimetry needs to be optimized and further developed in order to be able to deal with real exposure cases, where a mixture of both external and internal exposures will be encountered most of the times.

Retrospective biodosimetry techniques: Focus on cytogenetics assays for individuals exposed to ionizing radiation

In the absence of physical data, biodosimetry tools are required for fast dose and risk assessment in the event of radiological or nuclear mass accidents or attacks to triage exposed humans and take immediate medical countermeasures. Biodosimetry tools have mostly been developed for retrospective dose assessment and the follow-up of victims of irradiation. Among them, cytogenetics analyses, to reveal chromosome damage, are the most developed and allow the determination of doses from blood samples as low as 100 mGy. Various cytogenetic tests have already allowed retrospective dose assessment of Chernobyl liquidators and military personnel exposed to nuclear tests after decades. In this review, we discuss the properties of various biodosimetry techniques, such as their sensitivity and limitations as a function of the time from exposure, using multiple examples of nuclear catastrophes or working exposure. Among them, chromosome FISH hybridization, which reveals chromosome translocations, is the most reliable due to the persistence of translocations for decades, whereas dicentric chromosome and micronuclei assays allow rapid and accurate dose assessment a short time after exposure. Both need to be adjusted through mathematical algorithms for retrospective analyses, accounting for the time since exposure and the victims' age. The goal for the future will be to better model chromosome damage, reduce the time to result, and develop new complementary biodosimetry approaches, such as mutation signatures.

Quantities for assessing high doses to the body: a short review of the current status

Tissue reactions are the most clinically significant consequences of high-dose exposures to ionizing radiation. However, there is currently no universally recognized or recommended dose quantity that can be used to assess generalized risks to individuals following whole body exposures in the high-dose range. This is particularly problematic in emergency response situations, for example, following external exposures of large numbers of individuals: in attempts to relate the triage dosemeter absorbed dose to the risk to the individual, such that a 'dose' may subsequently be reported to medical professionals, it is necessary to first agree on the quantity to be reported. The current paper presents a brief review of the likely scenarios and emergency dosimetry techniques that require such a quantity, before examining the biological constraints and requirements that might underpin any future definition. The aim of this work is to outline the arguments for developing a commonly agreed dose quantity for reporting high-dose radiation exposures.