Biological dosimetry of ionizing radiation: Evaluation of the dose with cytogenetic methodologies by the construction of calibration curves (original) (raw)
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Atom Indonesia
Cytological biodosimetry methodology has been widely used for determining and estimating the precise irradiation dose received by victims in the situation of emergency irradiation exposure. The aim of this study was to assess the gamma-ray induced dicentric chromosomes and micronuclei (MN) in peripheral blood lymphocytes for preliminary reconstruction of cytogenetic biodosimetry. The study was performed by exposing blood samples taken from seven healthy donors to gamma rays at dose range of 0.1 to 4.0 Gy, followed by culturing them for 48-72 hours at 37 °C by the standard technique. After being harvested, the chromosome spread at metaphase and MN were stained with Giemsa's solution. The results showed that the frequency of both dicentrics and MN of samples were increased with the increase of radiation dose. Considerable increases of both cytologic damages were found in the samples exposed to higher doses (>2 Gy). Significant differences (p>0.05) only found in mean frequencies of MN for all doses tested. Reconstruction of the relationship of these frequencies with doses was found to follow linear-quadratic curve lines and was consistent with that of other studies. Due to the aforementioned advantages namely the dependence of radiation dose and dose rate on the frequency of of both dicentric and MN, despite some limitations, these assays have been found to be suitable to be used as biological dosimetry. It is concluded that in order for this cytogenetic biodosimety method by means of scoring/assessing the radiation-induced dicentrics and MN could be used in radiation emergency and protection, and further studies with larger numbers of samples need to be done.
Cytogenetic Biodosimetry for Radiation Disasters: Recent Advances
2005
Potential scenarios of radiation exposure resulting in mass casualties require individual, early, and definitive diagnostic radiation dose assessment to help provide medical aid within days of the occurrence of a catastrophe. The long-range goal of the Armed Forces Radiobiology Research Institute (AFRRI) Biological Dosimetry Team is to identify, develop, and optimize broad dose-range biodosimetry methods, using in vitro models, and to validate those methods, using suitable in vivo models. Of these methods, the cytological biodosimetry methods are capable of assessing radiation dose both in whole-body and partial-body radiation exposure scenarios. Chromosome-aberration analysis in exposed individual's peripheral blood lymphocytes is an internationally accepted "gold standard" cytogenetic biodosimetry method that can be used to assess dose to help develop a treatment strategy within days of a radiation catastrophe. We have established the conventional lymphocyte metaphase-spread dicentric assay, in accordance with international harmonized protocols, and have used the assay to estimate radiation doses in several accidents. Current efforts focus on increasing sample throughput via automation. We systematically addressed the development of an automated cytogenetic laboratory that can triage by exposure group (not life-threatening, potentially life-threatening, and significantly life-threatening) and thereby efficiently differentiate radiation-exposed individuals from the "concerned public" following a disaster. Our studies included concept feasibility, workflow analysis, possible process reengineering, bottleneck elimination in manual processing, and proof-in-principle experiments. With automation, up to 500 samples per week can be analyzed in triage mode in which chromosome aberration analysis is restricted to 20 to 50 metaphase spreads per sample compared with the conventional approach of 500 to 1000 spreads. In another effort, we are developing and validating a novel cytogenetic bioassay, the rapid interphase chromosome aberration (RICA) assay, using suitable in vivo models. In this innovative method, radiation-induced chromosome aberrations in specific chromosomes are studied directly and rapidly in resting peripheral blood lymphocytes after inducing premature chromosome condensation either by fluorescence in situ hybridization or by immuno-enzymatic detection based on bright-field microscopy. The latter method is amenable to automation using image analysis. We used an accidentally radiation-exposed cohort, in Thailand in Feb. 2000, to determine the ability of the RICA assay to assess whole-body equivalent dose; our results indicated that the RICA assay can be used to assess radiation-induced damage to a specific chromosome in interphase cells. We are using a rodent model to determine the persistency of radiation-induced damage and the influence of sampling delay on dose estimation. These studies, in general, will contribute to an improved diagnostic response to a mass-casualty situation and will improve protection and survivability in adverse ionizing radiation environments.
Radiation Environment and Medicine, 2022
Chromosomes are observed during the mitotic phase of the cell-cycle. As organisms have a species-specific chromosome number and morphology, any changes in the number or morphology can be considered as chromosome aberrations. It is well known that radiation exposure causes chromosome aberrations, and multiple studies have reported on the mechanisms of radiationinduced chromosome aberrations and the effects of radiation dose and quality on chromosome aberrations. Radiation-induced chromosome aberrations can be divided into 2 categories: stable chromosome aberrations which are inherited by daughter cells in cell division (e.g. translocations, inversions, partial deletions and duplications) and unstable chromosome aberrations which cause cell death and eventually disappear (e.g. dicentrics, rings and acentric fragments). In acute external exposure, unstable chromosome aberrations are usually used as indicators for accurate dose assessment to facilitate radiation emergency medical care. On the other hand, stable aberrations are generally used for retrospective dosimetry caused by past exposures. This article summarizes the essential information on chromosomes and chromosome aberrations for cytogenetic biodosimetry.
Genome Integrity, 2016
The utility of a biological dosimeter based on the analysis of dicentrics is invaluable in the event of a radiological emergency wherein the estimated absorbed dose of an exposed individual is crucial in the proper medical management of patients. The technique is also used for routine monitoring of occupationally exposed workers to determine radiation exposure. An in vitro irradiation study of human peripheral blood lymphocytes was conducted to establish a dose-response curve for radiation-induced dicentric aberrations. Blood samples were collected from volunteer donors and together with optically stimulated luminescence (OSL) dosimeters and were irradiated at 0, 0.1, 0.25, 0.5, 0.75, 1, 2, 4, and 6 Gy using a cobalt-60 radiotherapy unit. Blood samples were cultured for 48 h, and the metaphase chromosomes were prepared following the procedure of the International Atomic Energy Agency's Emergency Preparedness and Response – Biodosimetry 2011 manual. At least 100 metaphases were s...
3 Biotech, 2014
In cases of public or occupational radiation overexposure and eventual radiological accidents, it is important to provide dose assessment, medical triage, diagnoses and treatment to victims. Cytogenetic biodosimetry based on scoring of dicentric chromosomal aberrations assay (DCA) is the ''gold standard'' biotechnology technique for estimating medically relevant radiation doses. Under the auspices of the National Science, Technology and Innovation Plan in Saudi Arabia, we have set up a biodosimetry laboratory and produced a national standard dose-response calibration curve for DCA, prerequired to estimate the doses received. For this, the basic cytogenetic DCA technique needed to be established. Peripheral blood lymphocytes were collected from four healthy volunteers and irradiated with radiation doses between 0 and 5 Gy of 320 keV X-rays. Then, lymphocytes were PHA stimulated, Colcemid division arrested and stained cytogenetic slides were prepared. The Metafer4 system (MetaSystem) was used for automatic and manually assisted metaphase finding and scoring of dicentric chromosomes. Results were fit to the linear-quadratic doseeffect model according to the IAEA EPR-Biodosimetry-2011 report. The resulting manually assisted dose-response calibration curve (Y = 0.0017 ? 0.026 9 D ? 0.081 9 D 2) was in the range of those described in other populations. Although the automated scoring over-and-under estimates DCA at low (\1 Gy) and high ([2 Gy) doses, respectively, it showed potential for use in triage mode to segregate between victims with potential risk to develop acute radiotoxicity syndromes. In conclusion, we have successfully established the first biodosimetry laboratory in the region and have produced a preliminary national doseresponse calibration curve. The laboratory can now contribute to the national preparedness plan in response to eventual radiation emergencies in addition to providing information for decision makers and public health officials who assess the magnitude of public, medical, occupational and accidental radiation exposures.
Genetics and Molecular Biology, 2005
Scoring of unstable chromosome aberrations (dicentrics, rings and fragments) and micronuclei in circulating lymphocytes are the most extensively studied biological means for estimating individual exposure to ionizing radiation (IR), which can be used as complementary methods to physical dosimetry or when the latter cannot be performed. In this work, the quantification of the frequencies of chromosome aberrations and micronuclei were carried out based on cytogenetic analyses of peripheral blood samples from 5 patients with cervical uterine cancer following radiotherapy in order to evaluate the absorbed dose as a result of partial-body exposure to 60 Co source. Blood samples were collected from each patient in three phases of the treatment: before irradiation, 24 h after receiving 0.08 Gy and 1.8 Gy, respectively. The results presented in this report emphasize biological dosimetry, employing the quantification of chromosome aberrations and micronuclei in lymphocytes from peripheral blood, as an important methodology of dose assessment for either whole or partial-body exposure to IR.
Health Physics, 2014
Large scale radiological emergencies require high throughput techniques of biological dosimetry for population triage in order to identify individuals indicated for medical treatment. The dicentric assay is the "gold standard" technique for the performance of biological dosimetry, but it is very time consuming and needs well trained scorers. To increase the throughput of blood samples, semi-automation of dicentric scoring was investigated in the framework of the MULTIBIODOSE EU FP7 project, and dose effect curves were established in six biodosimetry laboratories. To validate these dose effect curves, blood samples from 33 healthy donors (>10 donors/scenario) were irradiated in vitro with 60 Co gamma rays simulating three different exposure scenarios: acute whole body, partial body, and protracted exposure, with three different doses for each scenario. All the blood samples were irradiated at Ghent University, Belgium, and then shipped blind coded to the participating laboratories. The blood samples were set up by each lab using their own standard protocols, and metaphase slides were prepared to validate the calibration curves established by semi-automatic dicentric scoring. In order to achieve this, 300 metaphases per sample were captured, and the doses were estimated using the newly formed dose effect curves. After acute uniform exposure, all laboratories were able to distinguish between 0 Gy, 0.5 Gy, 2.0, and 4.0 Gy (p < 0.001), and, in most cases, the dose estimates were within a range of ± 0.5 Gy of the given dose. After protracted exposure, all laboratories were able to distinguish between 1.0 Gy, 2.0 Gy, and 4.0 Gy (p < 0.001), and here also a large number of the dose estimates were within ± 0.5 Gy of the irradiation dose. After simulated partial body exposure, all laboratories were able to distinguish between 2.0 Gy, 4.0 Gy, and 6.0 Gy (p < 0.001). Overdispersion of the dicentric distribution enabled the detection of the partial body samples; however, this result was clearly dose-dependent. For partial body exposures, only a few dose estimates were in the range of ± 0.5 Gy of the given dose, but an improvement could be achieved with higher cell numbers. The new method of semi-automation of the dicentric assay was introduced successfully in a network of six laboratories. It is therefore concluded that this method can be used as a high-throughput screening tool in a large-scale radiation accident.
Stem cells (Dayton, Ohio), 1995
The premature chromosome condensation (PCC) assay has been proposed as a useful and rapid end point for biological dosimetry following accidental high-dose radiation overexposures. A major benefit of the PCC assay is that it does not require cells to divide for evaluation of cytogenetic damage. The PCC assay was performed on isolated human peripheral lymphocytes exposed in vitro to doses from 1 to 9 Gy of 250 kVp x-rays. The dose-response relationships of the frequency distribution and the yield of PCC fragments in cells were determined after one day of repair at 37 degrees C. A Qpcc approach, which involves the analysis of the yield of excess PCC fragments in damaged cells, was used to establish a dose-response calibration curve. This method is identical in concept to the Qdr technique introduced by Sasaki for partial-body exposure dose-estimates using asymmetrical chromosome aberrations (i.e., dicentrics and rings) in metaphase spreads of human lymphocytes. A simulated in vitro te...
OBM genetics, 2018
The technique of in situ hybridization (ISH) using radioactively labeled DNA probes was first described in the late 1960s and early 1970s. The first use of fluorescence in situ hybridization (FISH) was reported in 1980s where RNA labeled with a fluorophore at the 3' end was used to detect specific DNA sequences. Since then, the technique has undergone various modifications for detecting single genes, chromosomes and whole genomes on various targets such as interphase nucleus, prematurely condensed chromosomes, metaphase chromosomes, fresh and paraffinized tissue sections. Although FISH is quite frequently used in clinical diagnostics, its use has recently been extended to the field of radiation biodosimetry where both stable (translocations) and unstable aberrations (dicentrics and rings) are detected with high resolution for estimating the absorbed radiation dose in humans after incidental, accidental or occupational exposure to ionizing radiation. This review summarizes the diverse applications of FISH in radiation biodosimetry that range from radiation dose estimation to prediction of deterministic (i.e. acute radiation syndrome severity) and stochastic (i.e. genetic mutations and cancer) effects in the affected human population.
Biological Dosimetry Using Human Interphase Peripheral Blood Lymphocytes
Military Medicine, 2002
Conventional metaphase-spread chromosome-aberrationbased biodosimetry techniques for radiation dose assessment, although robust, are laborious and time consuming. The molecular cytogenetic laboratory of the Armed Forces Radiobiology Research Institute is developing simple and rapid interphase-based cytological assays that will be applicable to a broad range of radiation exposure scenarios. These assays include analysis of chromosome aberrations (premature chromosome condensation-fluorescence in situ hybridization assay) and mitochondrial DNA mutations (mtDNA4977 deletion assay) using resting human peripheral blood lymphocytes. The dose-effect relationship for radiation-induced aberrations involving chromosome 1 after 24 hours of repair at 37°C in resting human peripheral blood lymphocytes was studied using fluorescence in situ hybridization after chemical induction of premature chromosome condensation as previously explained. In the present study, we examined whether gamma irradiation in the range of 0 to 7.5 Gy induces a dose-dependent increase in aberrations manifested as "excess spots." The number of excess spots per cell, reflecting aberrations involving chromosome 1, increased from 0.035 at 0.5 Gy to 0.236 at 7.5 Gy. This observed dose-effect relationship was fit with a nonlinear power model. This technique may be extended to the study of radiation-induced translocations in interphase cells for retrospective dose reconstruction. With a recently developed in situ polymerase chain reaction method to detect and quantify mtDNA deletion in interphase cells after radiation exposure in cultured human peripheral blood lymphocytes, 90% to 95% of cells are analyzable. We discuss the potential use of the mtDNA deletion assay in biological dosimetry applications. Interphase-based cytological assays may eliminate some inherent problems associated with metaphase-spread-based assays. These problems involve (1) the limited number of analyzable cells containing chromosome aberrations, which is due to various factors including radiation-induced cell death and delay in cell cycle progression into mitosis, and (2) the requirements for radiation cytogenetics expertise and tedious labor to manually score chromosome aberrations.