Estimating the Lowest Detectable Dose of Ionizing Radiation by the Cytokinesis-Block Micronucleus Assay (original) (raw)
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An in vitro study of the dose responses of human peripheral blood lymphocytes was conducted with the aim of creating calibrated dose-response curves for biodosimetry measuring up to 4 Gy (0.25-4 Gy) of gamma radiation. The cytokinesis-blocked micronucleus (CBMN) assay was employed to obtain the frequencies of micronuclei (MN) per binucleated cell in blood samples from 16 healthy donors (eight males and eight females) in two age ranges of 20-34 and 35-50 years. The data were used to construct the calibration curves for men and women in two age groups, separately. An increase in micronuclei yield with the dose in a linear-quadratic way was observed in all groups. To verify the applicability of the constructed calibration curve, MN yields were measured in peripheral blood lymphocytes of two real overexposed subjects and three irradiated samples with unknown dose, and the results were compared with dose values obtained from measuring dicentric chromosomes. The comparison of the results obtained by the two techniques indicated a good agreement between dose estimates. The average baseline frequency of MN for the 130 healthy non-exposed donors (77 men and 55 women, 20-60 years old divided into four age groups) ranged from 6 to 21 micronuclei per 1000 binucleated cells. Baseline MN frequencies were higher for women and for the older age group. The results presented in this study point out that the CBMN assay is a reliable, easier and valuable alternative method for biological dosimetry.
The micronucleus assay as a biological dosimeter of in vivo ionising radiation exposure
Mutagenesis, 2011
Biological dosimetry, based on the analysis of micronuclei (MN) in the cytokinesis-block micronucleus (CBMN) assay can be used as an alternative method for scoring dicentric chromosomes in the field of radiation protection. Biological dosimetry or Biodosimetry, is mainly performed, in addition to physical dosimetry, with the aim of individual dose assessment. Many studies have shown that the number of radiation-induced MN is strongly correlated with dose and quality of radiation. The CBMN assay has become, in the last years, a thoroughly validated and standardised technique to evaluate in vivo radiation exposure of occupational, medical and accidentally exposed individuals. Compared to the gold standard, the dicentric assay, the CBMN assay has the important advantage of allowing economical, easy and quick analysis. The main disadvantage of the CBMN assay is related to the variable micronucleus (MN) background frequency, by which only in vivo exposures in excess of 0.2-0.3 Gy X-rays can be detected.
REVIEW The micronucleus assay as a biological dosimeter of in vivo ionising radiation exposure
2010
Biological dosimetry, based on the analysis of micronuclei (MN) in the cytokinesis-block micronucleus (CBMN) assay can be used as an alternative method for scoring dicentric chromosomes in the field of radiation protection. Biological dosimetry or Biodosimetry, is mainly performed, in addition to physical dosimetry, with the aim of individual dose assessment. Many studies have shown that the number of radiation-induced MN is strongly correlated with dose and quality of radiation. The CBMN assay has become, in the last years, a thoroughly validated and standardised technique to evaluate in vivo radiation exposure of occupational, medical and accidentally ex-posed individuals. Compared to the gold standard, the dicentric assay, the CBMN assay has the important advantage of allowing economical, easy and quick analysis.
Radiation and Environmental Biophysics
Radiation dose estimations performed by automated counting of micronuclei (MN) have been studied for their utility for triage following large-scale radiological incidents; although speed is essential, it also is essential to estimate radiation doses as accurately as possible for long-term epidemiological follow-up. Our goal in this study was to evaluate and improve the performance of automated MN counting for biodosimetry using the cytokinesis-block micronucleus (CBMN) assay. We measured false detection rates and used them to improve the accuracy of dosimetry. The average false-positive rate for binucleated cells was 1.14%; average false-positive and -negative MN rates were 1.03% and 3.50%, respectively. Detection errors seemed to be correlated with radiation dose. Correction of errors by visual inspection of images used for automated counting, called the semi-automated and manual scoring method, increased accuracy of dose estimation. Our findings suggest that dose assessment of the...
The micronucleus assay in radiation accidents
Annali dell'Istituto superiore di sanità, 2009
The cytokinesis-block micronucleus assay in peripheral blood lymphocytes is a standardised and validated technique for biodosimetry. Automated scoring of micronuclei allows large scale applications as in population triage in case of radiation accidents or malevolent use of radioactive sources. The dose detection limit (95% confidence) of the micronucleus assay for individual dose assessment is restricted to 0.2 Gy but can be decreased to 0.1 Gy by scoring centromeres in micronuclei using fluorescence in situ hybridization (FISH). In the past the micronucleus assay was applied for a number of large scale biomonitoring studies of nuclear power plant workers and hospital workers. Baseline micronucleus frequencies depend strongly on age and gender. The assay was also already used for biodosimetry of radiation accidents. In a multiple endpoint biodosimetry study for dose assessment of a worker exposed accidentally in 2003 to X-rays, a good agreement was obtained between dose estimates re...
The scoring of micronuclei in human peripheral blood lymphocytes is used as a biomarker and dosimeter of radiation exposure. In this paper we investigated a dose response curve for micronuclei in human lymphocytes following Cs-137 irradiation in vitro. The lymphocytes were obtained from 7 different donors aged between 24 and 51 years. The applied doses were: 0.0, 0.05, 0.1, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 3.0 and 4.0 Gy. There was an increase of micronuclei frequency MN with the dose. The dose-effect relationship was expressed with the following linear-quadratic equation Y = 20,56 + 39,59.D + 17,01.D 2 , where (Y)-represents the micronuclei yield, (D)-represents the applied radiation dose. A software program for absorbed dose assessment based on this equation was created.
International Journal of Radiation Biology, 2019
Comparative study of Micronucleus assays and Dicentric plus ring chromosomes for dose assessment in particular cases of partial-body exposure ABSTRACT Purpose: The goal was to compare the micronucleus (MN) and dicentric plus ring chromosomes (D+R) assays for dose assessment in cases of partial body irradiations (PBI). Materials and methods: We constructed calibration curves for each assay at doses ranging from 0 to 5 Gy. In order to simulate partial-body exposures, blood samples from two donors were irradiated with 0.5, 1, 2 and 4 Gy and the ratios of irradiated to unirradiated blood were 25, 50, and 100%. Different tests were used to confirm if all samples were overdispersed or zero-inflated and for partial-body dose assessment we used the Qdr, Dolphin and Bayesian model. Results: In our samples for D+R calibration curve, practically all doses agreed with Poisson assumption, but MN exhibited cellular distributions that tend to be overdispersed and zero-inflated. The exact Poisson tests and zero-inflated tests demonstrate that virtually all samples of D+R from PBI simulation fit the Poisson distribution and were not zero-inflated, but almost all doses from MN samples were overdispersed and zero-inflated. In the partial-body estimation, when Qdr and Dolphin methods were used the results from dicentrics were better than MN, but in our samples from D+R and MN the dose estimation defined by the Bayesian methodology were more accurate than the classically methods used in biodosimetry. Conclusions: Dicentric chromosomes continue to prove to be the best biological marker for dose assessment. However exposure scenarios of partial-body estimation, overdispersion and zero-inflation may not occur, it being a critical point not only for dose assessment, but also to confirm partial-body exposure. MN could be used as alternative assays for partial-body dose estimation, but only in case when we have sure about the accident.
Scientific Reports
A radiological or nuclear attack could involve such a large number of subjects as to overwhelm the emergency facilities in charge. Resources should therefore be focused on those subjects needing immediate medical attention and care. In such a scenario, for the triage management by first responders, it is necessary to count on efficient biological dosimetry tools capable of early detection of the absorbed dose. At present the validated assays for measuring the absorbed dose are dicentric chromosomes and micronuclei counts, which require more than 2–3 days to obtain results. To overcome this limitation the NATO SPS Programme funded an Italian–Egyptian collaborative project aimed at validating a fast, accurate and feasible tool for assessing the absorbed dose early after radiation exposure. Biomarkers as complete blood cell counts, DNA breaks and radio-inducible proteins were investigated on blood samples collected before and 3 h after the first fraction of radiotherapy in patients tre...
The quantification of micronuclei in lymphocytes is a method for estimating of individual exposure to ionizing radiation, which can be used complementary to physical dosimetry or when this later cannot be performed. In this work, the quantification of micronuclei was carried out using cytogenetic analyzes of peripheral blood samples from 5 patients with cervical uterine cancer following radiotherapy, in order to evaluate the absorbed dose as a result of exposure to 60 Co source. From each patient, blood samples were collected in three phases of the treatment: before irradiation, 24 h after receiving 0.08 Gy and 1.8 Gy, respectively. A good agreement was obtained between doses estimated by calibration curve of dose versus the frequencies of micronuclei and the values previously planned to the radiotherapy. The results presented in this report emphasizes biological dosimetry, based on the quantification of micronuclei in lymphocytes from peripheral blood, as an important methodology f...
HELIYON , 2023
In the modern developing society, application of radiation has increased extensively. With significant improvement in the radiation protection practices, exposure to human could be minimized substantially, but cannot be avoided completely. Assessment of exposure is essential for regulatory decision and medical management as applicable. Until now, cytogenetic changes have served as surrogate marker of radiation exposure and have been extensively employed for biological dose estimation of various planned and unplanned exposures. Dicentric Chromosomal Aberration (DCA) is radiation specific and is considered as gold standard, micronucleus is not very specific to radiation and is considered as an alternative method for biodosimetry. In this study dose response curves were generated for X-ray induced “dicentric + ring” and micronuclei, in lymphocytes of three healthy volunteers [2 females (age 22, 23 years) and 1 male (24 year)]. The blood samples were irradiated with X-ray using LINAC (energy 6 MV, dose rate 6 Gy/min), in the dose range of 0–5Gy. Irradiated blood samples were cultured and processed to harvest metaphases, as per standard procedures recommended by International Atomic Energy Agency. Pooled data obtained from all the three volunteers, were in agreement with Poisson distribution for “dicentric + ring”, however over dispersion was observed for micronuclei. Data (“dicentric + ring” and micronuclei) were fitted by linear quadratic model of the expression Y– –C + αD + βD2 using Dose Estimate software, version 5.2. The data fit has resulted in linear coefficient α = 0.0006 (±0.0068) “dicentric + ring” cell− 1 Gy− 1 and quadratic coefficient β = 0.0619 (±0.0043) “dicentric + ring” cell− 1 Gy− 2 for “dicentric + ring” and linear coefficient α = 0.0459 ± (0.0038) micronuclei cell− 1 Gy− 1 and quadratic coefficient β = 0.0185 ± (0.0010) micronuclei cell− 1 Gy− 2 for micronuclei, respectively. Background frequencies for “dicentric + ring” and micronuclei were 0.0006 ± 0.0004 and 0.0077 ± 0.0012 cell− 1, respectively. Established curves were validated, by reconstructing the doses of 8 dose blinded samples (4 by DCA and 4 by CBMN) using coefficients generated here. Estimated doses were within the variation of 0.9–16% for “dicentric + ring” and 21.7–31.2% for micronuclei respectively. These established curves have potential to be employed for biodosimetry of occupational, clinical and accidental exposures, for initial triage and medical management.