[Show abstract][Hide abstract] ABSTRACT: In case of a radiological emergency it is essential to assess the possible dose received by possible victims. Several disciplines, such as physical dosimetry, dose reconstruction and biological dosimetry should put together their expertise to respond as fast as possible. Among different methods used in biological dosimetry, " dicentric analysis " is still the most widely used method, as it has the lowest detection limit, is the one that most accurately estimates the dose, and distinguishes between whole-and partial-body irradiations. To score dicentric chromosomes, peripheral blood lymphocytes have to be stimulated to enter the cell cycle and reach metaphase. In addition, skilled scorers should analyze at the microscope complete cells containing 46 centromeres and to recognize dicentrics chromosomes with their corresponding acentric fragment. For this reason, dicentric analysis is time consuming and in case of an accident involving a large number of victims, it should not be possible to respond promptly. One promising improvement of the methodology is to automate dicentric analysis, and nowadays several laboratories of biological dosimetry have the equipment needed to perform automatic dicentric scoring (ADS). Here we present a review of different experiences carried out at the " Institut de Radioprotection et Sûreté Nucléaire " from France to compare ADS in relation to manual scoring (MS) and evaluate the feasibility to introduce ADS as a real option to be used instead of MS. The experience obtained indicates that automatic dicentric scoring is a real alternative and is mature enough to substitute manual scoring.
[Show abstract][Hide abstract] ABSTRACT: The combination of automatic image acquisition and automatic image analysis of premature chromosome condensation (PCC) spreads
was tested as a rapid biodosimeter protocol. Human peripheral lymphocytes were irradiated with 60Co gamma rays in a single dose of between 1 and 20 Gy, stimulated with phytohaemaglutinin and incubated for 48 h, division
blocked with Colcemid, and PCC-induced by Calyculin A. Images of chromosome spreads were captured and analysed automatically
by combining the Metafer 4 and CellProfiler platforms. Automatic measurement of chromosome lengths allows the calculation
of the length ratio (LR) of the longest and the shortest piece that can be used for dose estimation since this ratio is correlated
with ionizing radiation dose. The LR of the longest and the shortest chromosome pieces showed the best goodness-of-fit to
a linear model in the dose interval tested. The application of the automatic analysis increases the potential use of the PCC
method for triage in the event of massive radiation causalities.
Full-text · Article · Apr 2014 · Journal of Radiation Research
[Show abstract][Hide abstract] ABSTRACT: The estimation of the dose and the irradiated fraction of the body is important information in the primary medical response in case of a radiological accident. The PCC-R assay has been developed for high-dose estimations, but little attention has been given to its applicability for partial-body irradiations. In the present work we estimated the doses and the percentage of the irradiated fraction in simulated partial-body radiation exposures at high doses using the PCC-R assay. Peripheral whole blood of three healthy donors was exposed to doses from 0-20 Gy, with (60)Co gamma radiation. To simulate partial body irradiations, irradiated and non-irradiated blood was mixed to obtain proportions of irradiated blood from 10-90%. Lymphocyte cultures were treated with Colcemid and Calyculin-A before harvest. Conventional and triage scores were performed for each dose, proportion of irradiated blood and donor. The Papworth's u test was used to evaluate the PCC-R distribution per cell. A dose-response relationship was fitted according to the maximum likelihood method using the frequencies of PCC-R obtained from 100% irradiated blood. The dose to the partially irradiated blood was estimated using the Contaminated Poisson method. A new D0 value of 10.9 Gy was calculated and used to estimate the initial fraction of irradiated cells. The results presented here indicate that by PCC-R it is possible to distinguish between simulated partial- and whole-body irradiations by the u-test, and to accurately estimate the dose from 10-20 Gy, and the initial fraction of irradiated cells in the interval from 10-90%.
Full-text · Article · Apr 2013 · Journal of Radiation Research
[Show abstract][Hide abstract] ABSTRACT: Dicentric chromosome analysis remains the most widely used method in biodosimetry. It not only has an excellent lower detection limit of about 0.1 Gy, but also allows one to distinguish between whole- and partial-body exposures. A drawback of the dicentric analysis is that it is a time consuming method and maybe difficult to implement in a mass casualty event. To try to increase the analysis capacity, automatic dicentric scoring (ADS) using image analysis software is being incorporated in several laboratories. Here we present the results obtained in an emergency exercise simulating 50 victims. The ability to distinguish different radiations scenarios is evaluated. To simulate whole-body exposures peripheral blood samples were irradiated at doses between 0-4.7 Gy, and to simulate partial-body exposures irradiated and nonirradiated blood were mixed in different proportions. With the data obtained from the first slide analyzed (with about 300-400 cells), 32 of 34 simulated whole-body exposures were correctly classified according to radiation exposure levels. For simulated partial-body irradiations, it was possible to detect them as partial exposures at the end of the first slide analyzed but only at the highest doses. In all cases the classification was updated every time the analysis of one additional slide was finished. The comparison between our present results and those reported in the literature for manual scoring shows that for triage purposes the ADS based on 300-400 cells is similar in efficiency to classifying the cases based on manual scoring of 50 cells. However, if one accounts for the associated uncertainties and the time needed for ADS, we suggest that ADS triage scoring should be based on about 1,000 cells. For final dose estimations the number of cells to score will depend on the initial estimated dose, and on the information contributed from physical dose-reconstruction or clinical symptoms. At doses higher than 1 Gy, we propose analysis of 1,500 and for lower doses or suspected partial-body exposures, the number of cells to score should be 3,000.
No preview · Article · Apr 2013 · Radiation Research
[Show abstract][Hide abstract] ABSTRACT: The worldwide use of sources of ionizing radiation for medical, industrial, research and other purposes is inextricably associated with the risk of accidental human exposure. In addition, a constant threat of a nuclear explosion or radiation release, whether during military or terrorist events or as a result of accidents in nuclear power plants keeps raising a possibility of overexposure of the military personnel, workers, and general public to ionizing radiation. As indicated by the recent events at the Fukushima power plant, ongoing terrorist activities, and intelligence information, there is a strong sentiment that it is not a Discussion of if, but when, a radiological or nuclear event materializes. The high potential for the occurrence of such events calls for action plans, guidance, and pre-positioned resources and expertise provided by the defence forces in order to assess, triage and medically manage the exposed individuals and inform commanders’ options for operating in contaminated or potentially contaminated areas. The need to research and develop new and improved methods to counter the nuclear/radiological threats is clear and unambiguous.
[Show abstract][Hide abstract] ABSTRACT: In accidental exposure to ionizing radiation, it is essential to estimate the dose received by the victims. Currently dicentric scoring is the best biological indicator of exposure. The standard biological dosimetry procedure (500 metaphases scored manually) is suitable for a few dose estimations, but the time needed for analysis can be problematic in the case of a large-scale accident. Recently, a new methodology using automatic detection of dicentrics has greatly decreased the time needed for dose estimation and preserves the accuracy of the estimation. However, the capability to detect nonhomogeneous partial-body exposures is an important advantage of dicentric scoring-based biodosimetry, and this remains to be tested with automatic scoring. Thus we analyzed the results obtained with in vitro blood dilutions and in real cases of accidental exposure (partial- or whole-body exposure) using manual scoring and automatic detection of dicentrics. We confirmed that automatic detection allows threefold quicker dicentric scoring than the manual procedure with similar dose estimations and uncertainty intervals. The results concerning partial-body exposures were particularly promising, and homogeneously exposed samples were correctly distinguished from heterogeneously exposed samples containing 5% to 75% of blood irradiated with 2 Gy. In addition, the results obtained for real accident cases were similar whatever the methodology used. This study demonstrates that automatic detection of dicentrics is a credible alternative for recent and acute cases of whole- and partial-body accidental exposures to ionizing radiation.
No preview · Article · Dec 2011 · Radiation Research
[Show abstract][Hide abstract] ABSTRACT: After large-scale accidental overexposure to ionizing radiation, a rapid triage of the exposed population can be performed by scoring dicentrics and ring chromosomes among 50 metaphases. This is rapid but is not accurate because the sensitivity is around 0.5 Gy. After the triage step, dose can be estimated by scoring 500 metaphases. This is lengthy but very accurate because the sensitivity is between 0.1 and 0.2 Gy. To improve the methodology, we propose the use of software for automatic dicentric scoring that was tested on victims of an accident in Dakar. Manual scoring of 50 metaphases was carried out, then manual scoring of 500 metaphases, and automatic scoring. Comparison between the dose classifications obtained with manual scoring on 50 metaphases and 500 metaphases showed 50% misclassification with the manual scoring on 50 metaphases. Comparison between the dose classifications obtained with the automatic scoring and manual scoring on 500 metaphases showed only 4.35% misclassification with the automatic scoring. The automatic scoring method is more accurate than the manual scoring on 50 metaphases and can therefore be used for triage, and in place of the manual scoring on 500 metaphases method for individual dose estimation, because it is as accurate and much faster.
No preview · Article · Jun 2009 · Radiation Research
[Show abstract][Hide abstract] ABSTRACT: Preservation of hematopoietic stem and progenitor cells from early radiation-induced apoptosis is the rationale for emergency antiapoptotic cytokine therapy (EACK) after radiation accidents. This strategy is based on the combination of stem cell factor + Flt3-ligand + thrombopoietin + interleukin 3 (SFT3). The long-term safety and efficacy of EACK in managing severe radiation exposure were evaluated.
Early administration of SFT3 + pegfilgrastim was assessed in 7-Gy gamma total body-irradiated (TBI) monkeys. Efficiency of delayed administration was also addressed after 5-Gy TBI.
Here we showed that a single, intravenous injection of SFT3 2 hours after 7-Gy TBI reduced the period of thrombocytopenia (platelet count <20 x 10(9)/L: 0.8 +/- 1.5 day vs 23.8 +/- 15.9 days in controls; p < 0.05) and blood transfusion needs. Moreover, addition of pegfilgrastim to SFT3 treatment shortened the period of neutropenia compared with SFT3 and control groups (neutrophil count <0.5 x 10(9)/L: 7 +/- 1.4 days vs 13 +/- 3.2 days and 15.2 +/- 1.5 days; p < 0.05). In both SFT3 groups, bone marrow activity recovered earlier and, in contrast with controls, platelet count returned to baseline values from 250 days after irradiation. Furthermore, delayed (48 hours) single SFT3 administration in 5-Gy irradiated monkeys significantly reduced thrombocytopenia compared to controls. Finally, SFT3 did not increase frequency of total chromosome translocations observed in the blood lymphocytes of controls 1 year after 5 Gy TBI.
These results suggest the safety and efficacy of EACK in managing severe radiation exposure.
No preview · Article · Aug 2007 · Experimental Hematology