Twenty-two years later: consistent dose estimation of an accidental overexposure by retrospective biological dosimetry.

The goal of this study was to retrospectively estimate the exposure dose of a victim from the Lilo radiological accident in Georgia after 22 y and compare it with the original cytogenetics-based analysis performed in our laboratory. Similar types of studies have been published, notably involving victims of the Chernobyl, Goiânia and Tammiku accidents. Nevertheless, their estimations were done after shorter periods of time post-exposure, and in some cases, the exposure might not have been exclusively of an external nature. In this study, Fluorescence In Situ Hybridization (FISH) was used to score chromosomal translocations in lymphocytes from a recent blood sample of the victim and the dose assessment was performed using our laboratory's FISH calibration curve. The resulting whole-body exposure dose of 0.35 Gy [0.12, 0.72] was similar to the one obtained when reanalysing the original scoring data from 1997 (0.38 Gy [0.13-0.75]), suggesting that our current calibration curve could be used for relative dose estimations long time after external exposure.

RENEB Inter-Laboratory Comparison 2021: Inter-Assay Comparison of Eight Dosimetry Assays.

Tools for radiation exposure reconstruction are required to support the medical management of radiation victims in radiological or nuclear incidents. Different biological and physical dosimetry assays can be used for various exposure scenarios to estimate the dose of ionizing radiation a person has absorbed. Regular validation of the techniques through inter-laboratory comparisons (ILC) is essential to guarantee high quality results. In the current RENEB inter-laboratory comparison, the performance quality of established cytogenetic assays [dicentric chromosome assay (DCA), cytokinesis-block micronucleus assay (CBMN), stable chromosomal translocation assay (FISH) and premature chromosome condensation assay (PCC)] was tested in comparison to molecular biological assays [gamma-H2AX foci (gH2AX), gene expression (GE)] and physical dosimetry-based assays [electron paramagnetic resonance (EPR), optically or thermally stimulated luminescence (LUM)]. Three blinded coded samples (e.g., blood, enamel or mobiles) were exposed to 0, 1.2 or 3.5 Gy X-ray reference doses (240 kVp, 1 Gy/min). These doses roughly correspond to clinically relevant groups of unexposed to low exposed (0-1 Gy), moderately exposed (1-2 Gy, no severe acute health effects expected) and highly exposed individuals (>2 Gy, requiring early intensive medical care). In the frame of the current RENEB inter-laboratory comparison, samples were sent to 86 specialized teams in 46 organizations from 27 nations for dose estimation and identification of three clinically relevant groups. The time for sending early crude reports and more precise reports was documented for each laboratory and assay where possible. The quality of dose estimates was analyzed with three different levels of granularity, 1. by calculating the frequency of correctly reported clinically relevant dose categories, 2. by determining the number of dose estimates within the uncertainty intervals recommended for triage dosimetry (±0.5 Gy or ±1.0 Gy for doses <2.5 Gy or >2.5 Gy), and 3. by calculating the absolute difference (AD) of estimated doses relative to the reference doses. In total, 554 dose estimates were submitted within the 6-week period given before the exercise was closed. For samples processed with the highest priority, earliest dose estimates/categories were reported within 5-10 h of receipt for GE, gH2AX, LUM, EPR, 2-3 days for DCA, CBMN and within 6-7 days for the FISH assay. For the unirradiated control sample, the categorization in the correct clinically relevant group (0-1 Gy) as well as the allocation to the triage uncertainty interval was, with the exception of a few outliers, successfully performed for all assays. For the 3.5 Gy sample the percentage of correct classifications to the clinically relevant group (≥2 Gy) was between 89-100% for all assays, with the exception of gH2AX. For the 1.2 Gy sample, an exact allocation to the clinically relevant group was more difficult and 0-50% or 0-48% of the estimates were wrongly classified into the lowest or highest dose categories, respectively. For the irradiated samples, the correct allocation to the triage uncertainty intervals varied considerably between assays for the 1.2 Gy (29-76%) and 3.5 Gy (17-100%) samples. While a systematic shift towards higher doses was observed for the cytogenetic-based assays, extreme outliers exceeding the reference doses 2-6 fold were observed for EPR, FISH and GE assays. These outliers were related to a particular material examined (tooth enamel for EPR assay, reported as kerma in enamel, but when converted into the proper quantity, i.e. to kerma in air, expected dose estimates could be recalculated in most cases), the level of experience of the teams (FISH) and methodological uncertainties (GE). This was the first RENEB ILC where everything, from blood sampling to irradiation and shipment of the samples, was organized and realized at the same institution, for several biological and physical retrospective dosimetry assays. Almost all assays appeared comparably applicable for the identification of unexposed and highly exposed individuals and the allocation of medical relevant groups, with the latter requiring medical support for the acute radiation scenario simulated in this exercise. However, extreme outliers or a systematic shift of dose estimates have been observed for some assays. Possible reasons will be discussed in the assay specific papers of this special issue. In summary, this ILC clearly demonstrates the need to conduct regular exercises to identify research needs, but also to identify technical problems and to optimize the design of future ILCs.

RENEB Inter-Laboratory Comparison 2021: The Dicentric Chromosome Assay.

After large-scale radiation accidents where many individuals are suspected to be exposed to ionizing radiation, biological and physical retrospective dosimetry assays are important tools to aid clinical decision making by categorizing individuals into unexposed/minimally, moderately or highly exposed groups. Quality-controlled inter-laboratory comparisons of simulated accident scenarios are regularly performed in the frame of the European legal association RENEB (Running the European Network of Biological and Physical retrospective Dosimetry) to optimize international networking and emergency readiness in case of large-scale radiation events. In total 33 laboratories from 22 countries around the world participated in the current RENEB inter-laboratory comparison 2021 for the dicentric chromosome assay. Blood was irradiated in vitro with X rays (240 kVp, 13 mA, ∼75 keV, 1 Gy/min) to simulate an acute, homogeneous whole-body exposure. Three blood samples (no. 1: 0 Gy, no. 2: 1.2 Gy, no. 3: 3.5 Gy) were sent to each participant and the task was to culture samples, to prepare slides and to assess radiation doses based on the observed dicentric yields from 50 manually or 150 semi-automatically scored metaphases (triage mode scoring). Approximately two-thirds of the participants applied calibration curves from irradiations with γ rays and about 1/3 from irradiations with X rays with varying energies. The categorization of the samples in clinically relevant groups corresponding to individuals that were unexposed/minimally (0-1 Gy), moderately (1-2 Gy) or highly exposed (>2 Gy) was successfully performed by all participants for sample no. 1 and no. 3 and by ≥74% for sample no. 2. However, while most participants estimated a dose of exactly 0 Gy for the sham-irradiated sample, the precise dose estimates of the samples irradiated with doses >0 Gy were systematically higher than the corresponding reference doses and showed a median deviation of 0.5 Gy (sample no. 2) and 0.95 Gy (sample no. 3) for manual scoring. By converting doses estimated based on γ-ray calibration curves to X-ray doses of a comparable mean photon energy as used in this exercise, the median deviation decreased to 0.27 Gy (sample no. 2) and 0.6 Gy (sample no. 3). The main aim of biological dosimetry in the case of a large-scale event is the categorization of individuals into clinically relevant groups, to aid clinical decision making. This task was successfully performed by all participants for the 0 Gy and 3.5 Gy samples and by 74% (manual scoring) and 80% (semiautomatic scoring) for the 1.2 Gy sample. Due to the accuracy of the dicentric chromosome assay and the high number of participating laboratories, a systematic shift of the dose estimates could be revealed. Differences in radiation quality (X ray vs. γ ray) between the test samples and the applied dose effect curves can partly explain the systematic shift. There might be several additional reasons for the observed bias (e.g., donor effects, transport, experimental conditions or the irradiation setup) and the analysis of these reasons provides great opportunities for future research. The participation of laboratories from countries around the world gave the opportunity to compare the results on an international level.

RENEB Inter-Laboratory Comparison 2021: The FISH-Based Translocation Assay.

Translocation analysis using fluorescence in situ hybridization (FISH) is the method of choice for dose assessment in case of chronic or past exposures to ionizing radiation. Although it is a widespread technique, unlike dicentrics, the number of FISH-based inter-laboratory comparisons is small. For this reason, although the current Running the European Network of Biological and Physical retrospective Dosimetry (RENEB) inter-laboratory comparison 2021 was designed as a fast response to a real emergency scenario, it was considered a good opportunity to perform an inter-laboratory comparison using the FISH technique to gain further experience. The Bundeswehr Institute of Radiobiology provided peripheral blood samples from one healthy human volunteer. Three test samples were irradiated with blinded doses of 0, 1.2, and 3.5 Gy, respectively. Samples were then sent to the seven participating laboratories. The FISH technique was applied according to the standard procedure of each laboratory. Both, the frequency of translocations and the estimated dose for each sample were sent to the coordinator using a special scoring sheet for FISH. All participants sent their results in due time. However, although it was initially requested to send the results based on the full analysis, evaluating 500 equivalent cells, most laboratories only sent the results based on triage, with a smaller number of analyzed cells. In the triage analysis, there was great heterogeneity in the number of equivalent cells scored. On the contrary, for the full analysis, this number was more homogeneous. For all three samples, one laboratory showed outlier yields compared to the other laboratories. Excluding these results, in the triage analysis, the frequency of translocations in sample no. 1 ranged from 0 to 0.013 translocations per cell, and for samples no. 2 and no. 3 the genomic mean frequency were 0.27 ± 0.03 and 1.47 ± 0.14, with a coefficient of variation of 0.29 and 0.23 respectively. Considering only results obtained in the triage analysis for sample no. 1, all laboratories, except one, classified this sample as the non-irradiated one. For sample no. 2, excluding the outlier value, the mean reported dose was 1.74 ± 0.16 Gy indicating a mean deviation of about 0.5 Gy to the delivered dose of 1.2 Gy. For sample no. 3 the mean dose estimated was 4.21 ± 0.21 Gy indicating a mean deviation of about 0.7 Gy to the delivered dose of 3.5 Gy. In the frame of RENEB, this is the second FISH-based inter-laboratory comparison. The whole exercise was planned as a response to an emergency, therefore, a triage analysis was requested for all the biomarkers except for FISH. Although a full analysis was initially requested for FISH, most of the laboratories reported only a triage-based result. The main reason is that it was not clearly stated what was required before starting the exercise. Results show that most of the laboratories successfully discriminated unexposed and irradiated samples from each other without any overlap. A good agreement in the observed frequencies of translocations was observed but there was a tendency to overestimate the delivered doses. Efforts to improve the harmonization of this technique and subsequent exercises to elucidate the reason for this trend should be promoted.

Pro re nata medications in mental health: Results of a transversal study.

BACKGROUND: Pro re nata are frequent in psychiatry. The risks engendered by this treatment requires that their prescription and administration be made safer. The frequency of administration of pro re nata depends mainly on the nurse's clinical judgment. AIMS: Our first objective was to assess nurses' satisfaction about the quality of doctors' pro re nata prescriptions. Our second objective was to assess the nurses' self-reported practices for administering pro re nata treatments as written in the prescription. METHOD: Self-administered questionnaires were sent by the hospital's internal mail between November 13, 2014, and December 10, 2014 to all nurses in our psychiatric establishment in France. The questionnaire included multiple-choice questions and questions based on clinical vignettes. RESULTS: The response rate was 51.9% (124/239). Overall, 75.6% considered that the quality of the prescriptions in terms of dosage was satisfactory. However, regardless of the quality of the doctor's pro re nata prescription, nurses did not contact the doctor even when the prescription quality was poor. Unexpectedly, we found that 88.7% have administered medication "as needed" without a doctor's prescription and sometimes acted without consulting doctors. CONCLUSIONS: The nurses appeared globally satisfied with doctors' prescriptions of pro re nata medications. On the other hand, most administered some medications without any prescription, that is, illegally. Physicians must be rigorous in the quality of their PRN prescriptions. At the same time, nurses must comply with the medical prescription or contact the physician if the quality of the PRN prescription appears poor.

The 2019-2020 EURADOS WG10 and RENEB Field Test of Retrospective Dosimetry Methods in a Small-Scale Incident Involving Ionizing Radiation.

With the use of ionizing radiation comes the risk of accidents and malevolent misuse. When unplanned exposures occur, there are several methods which can be used to retrospectively reconstruct individual radiation exposures; biological methods include analysis of aberrations and damage of chromosomes and DNA, while physical methods rely on luminescence (TL/OSL) or EPR signals. To ensure the quality and dependability of these methods, they should be evaluated under realistic exposure conditions. In 2019, EURADOS Working Group 10 and RENEB organized a field test with the purpose of evaluating retrospective dosimetry methods as carried out in potential real-life exposure scenarios. A 1.36 TBq 192Ir source was used to irradiate anthropomorphic phantoms in different geometries at doses of several Gy in an outdoor open-air geometry. Materials intended for accident dosimetry (including mobile phones and blood) were placed on the phantoms together with reference dosimeters (LiF, NaCl, glass). The objective was to estimate radiation exposures received by individuals as measured using blood and fortuitous materials, and to evaluate these methods by comparing the estimated doses to reference measurements and Monte Carlo simulations. Herein we describe the overall planning, goals, execution and preliminary outcomes of the 2019 field test. Such field tests are essential for the development of new and existing methods. The outputs from this field test include useful experience in terms of planning and execution of future exercises, with respect to time management, radiation protection, and reference dosimetry to be considered to obtain relevant data for analysis.

Amplification of R-spondin1 signaling induces granulosa cell fate defects and cancers in mouse adult ovary.

R-spondin1 is a secreted regulator of WNT signaling, involved in both embryonic development and homeostasis of adult organs. It can have a dual role, acting either as a mitogen or as a tumor suppressor. During ovarian development, Rspo1 is a key factor required for sex determination and differentiation of the follicular cell progenitors, but is downregulated after birth. In human, increased RSPO1 expression is associated with ovarian carcinomas, but it is not clear whether it is a cause or a consequence of the tumorigenic process. To address the role of Rspo1 expression in adult ovaries, we generated an Rspo1 gain-of-function mouse model. Females were hypofertile and exhibited various ovarian defects, ranging from cysts to ovarian tumors. Detailed phenotypical characterization showed anomalies in the ovulation process. Although follicles responded to initial follicle-stimulating hormone stimulation and developed normally until the pre-ovulatory stage, they did not progress any further. Although non-ovulated oocytes degenerated, the surrounding follicular cells did not begin atresia. RSPO1-induced expression not only promotes canonical WNT signaling but also alters granulosa cell fate decisions by maintaining epithelial-like traits in these cells. This prevents follicle cells from undergoing apoptosis, leading to the accumulation of granulosa cell tumors that reactivates the epithelial program from their progenitors. Taken together, our data demonstrate that activation of RSPO1 is sufficient in promoting ovarian tumors and thus supports a direct involvement of this gene in the commencement of ovarian cancers.

Late postpancreatectomy hemorrhage: Predictive factors of morbidity and mortality after percutaneous endovascular treatment.

PURPOSE: The objective of this study was to evaluate the effectiveness of endovascular treatment in patients presenting with late hemorrhage after pancreatectomy (LPPH). MATERIAL AND METHOD: Between 2008 and 2012, 53 percutaneous arterial procedures were performed in 42 patients with LPPH. There were 27 men and 15 women (mean age, 61.8 years±14.5 [SD]; range: 19-81 years). Clinical and technical success along with frequency of complications associated with the use of different endovascular techniques in patients with and without arterial anatomical variation were assessed. RESULTS: Clinical success was observed in 35/42 patients (85%). The technical success was 37.5% in patients with anatomical variation versus 82.8% for those with modal anatomy (P=0.003). Repeat bleeding (P=0.029), complications (P=0.013) and mortality (P=0.045) were more frequent in patients with variation of celiac artery than in those with modal anatomy. For hepatic and gastroduodenal artery stump bleeding, the rate of complications was higher (60%) in the group treated by hepatic artery embolization (P=0.028) by comparison with gastroduodenal artery stump selective embolisations or treatments by covered stent. A significant difference in mortality rate was found between patients with anatomical variations of celiac artery (36.4%) and those with normal anatomy (6.5%) (P=0.032). CONCLUSION: Percutaneous endovascular treatment is effective in patients presenting with LPPH. The presence of an anatomical variation of the celiac artery increases the rate of complications and mortality in patients with LPPH.

Factors influencing recurrence following initial hepatectomy for colorectal liver metastases.

BACKGROUND: Data on recurrence patterns following hepatectomy for colorectal liver metastases (CRLMs) and their impact on long-term outcomes are limited in the setting of modern multimodal management. This study sought to characterize the patterns of, factors associated with, and survival impact of recurrence following initial hepatectomy for CRLMs. METHODS: A retrospective cohort study of patients undergoing initial hepatectomy for CRLMs at 39 institutions (2006-2013) was conducted. Kaplan-Meier methods were used for survival analyses. Overall survival landmark analysis at 12 months after hepatectomy was performed to compare groups based on recurrence. Multivariable Cox and regression models were used to determine factors associated with recurrence. RESULTS: Among 2320 patients, tumours recurred in 47·4 per cent at median of 10·1 (range 0-88) months; 89·1 per cent of recurrences developed within 3 years. Recurrence was intrahepatic in 46·2 per cent, extrahepatic in 31·8 per cent and combined intra/extrahepatic in 22·0 per cent. The 5-year overall survival rate decreased from 74·3 (95 per cent c.i. 72·2 to 76·4) per cent without recurrence to 57·5 (55·0 to 60·0) per cent with recurrence (adjusted hazard ratio (HR) 3·08, 95 per cent c.i. 2·31 to 4·09). After adjusting for clinicopathological variables, prehepatectomy factors associated with increased risk of recurrence were node-positive primary tumour (HR 1·27, 1·09 to 1·49), more than three liver metastases (HR 1·27, 1·06 to 1·52) and largest metastasis greater than 4 cm (HR 1·19; 1·01 to 1·43). CONCLUSION: Recurrence after CRLM resection remains common. Although overall survival is inferior with recurrence, excellent survival rates can still be achieved.

Realising the European network of biodosimetry: RENEB-status quo.

Creating a sustainable network in biological and retrospective dosimetry that involves a large number of experienced laboratories throughout the European Union (EU) will significantly improve the accident and emergency response capabilities in case of a large-scale radiological emergency. A well-organised cooperative action involving EU laboratories will offer the best chance for fast and trustworthy dose assessments that are urgently needed in an emergency situation. To this end, the EC supports the establishment of a European network in biological dosimetry (RENEB). The RENEB project started in January 2012 involving cooperation of 23 organisations from 16 European countries. The purpose of RENEB is to increase the biodosimetry capacities in case of large-scale radiological emergency scenarios. The progress of the project since its inception is presented, comprising the consolidation process of the network with its operational platform, intercomparison exercises, training activities, proceedings in quality assurance and horizon scanning for new methods and partners. Additionally, the benefit of the network for the radiation research community as a whole is addressed.

Validation of semi-automatic scoring of dicentric chromosomes after simulation of three different irradiation scenarios.

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 6°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.

Minimal portal vein stenosis is a promising preconditioning in living donor liver transplantation in porcine model.

BACKGROUND & AIMS: The main hindrance in promoting living donor liver transplantation remains the morbi-mortality risk for the donor. Considering the opposed remodeling influence of portal and hepatic artery flows, our working hypothesis was to identify a lobar portal vein stenosis capable of inducing a contralateral liver mass compensatory enlargement, without the downstream ipsilateral atrophic response. METHODS: Twenty-four pigs entered this study. Six of them were used to establish hemodynamic changes following a progressive left portal vein (LPV) stenosis, in blood flow, pressure and vessel diameter of the LPV, main portal vein and hepatic artery. Sixteen pigs were divided into 4 groups: sham operated animals, 20% LPV stenosis, 50% LPV stenosis, and 100% LPV stenosis. Daily liver biopsies were collected until post-operative day 5 to investigate liver regeneration and atrophy (Ki67, STAT3, LC3, and activated caspase 3) according to the degree of LPV stenosis. Finally, changes in liver volumetry after 20% LPVS were investigated. RESULTS: A 20% LPV stenosis led to dilatation of the hepatic artery and a subsequent four-fold increase in hepatic arterial flow. Concomitantly, liver regeneration was triggered in the non-ligated lobe and the cell proliferation peak, 5 days after surgery, was comparable to that obtained after total LPV ligation. Moreover, 20% LPV stenosis preconditioning did not induce left liver atrophy contrary to 50 and 100% LPV stenosis. CONCLUSIONS: A 20% LPV stenosis seems to be the adequate preconditioning to get the remnant liver of living donor ready to take on graft harvesting without atrophy of the future graft.

Web-based scoring of the dicentric assay, a collaborative biodosimetric scoring strategy for population triage in large scale radiation accidents.

In the case of a large scale radiation accident high throughput methods of biological dosimetry for population triage are needed to identify individuals requiring clinical treatment. The dicentric assay performed in web-based scoring mode may be a very suitable technique. Within the MULTIBIODOSE EU FP7 project a network is being established of 8 laboratories with expertise in dose estimations based on the dicentric assay. Here, the manual dicentric assay was tested in a web-based scoring mode. More than 23,000 high resolution images of metaphase spreads (only first mitosis) were captured by four laboratories and established as image galleries on the internet (cloud). The galleries included images of a complete dose effect curve (0-5.0 Gy) and three types of irradiation scenarios simulating acute whole body, partial body and protracted exposure. The blood samples had been irradiated in vitro with gamma rays at the University of Ghent, Belgium. Two laboratories provided image galleries from Fluorescence plus Giemsa stained slides (3 h colcemid) and the image galleries from the other two laboratories contained images from Giemsa stained preparations (24 h colcemid). Each of the 8 participating laboratories analysed 3 dose points of the dose effect curve (scoring 100 cells for each point) and 3 unknown dose points (50 cells) for each of the 3 simulated irradiation scenarios. At first all analyses were performed in a QuickScan Mode without scoring individual chromosomes, followed by conventional scoring (only complete cells, 46 centromeres). The calibration curves obtained using these two scoring methods were very similar, with no significant difference in the linear-quadratic curve coefficients. Analysis of variance showed a significant effect of dose on the yield of dicentrics, but no significant effect of the laboratories, different methods of slide preparation or different incubation times used for colcemid. The results obtained to date within the MULTIBIODOSE project by a network of 8 collaborating laboratories throughout Europe are very promising. The dicentric assay in the web based scoring mode as a high throughput scoring strategy is a useful application for biodosimetry in the case of a large scale radiation accident.

Automatic scoring of dicentric chromosomes as a tool in large scale radiation accidents.

Mass casualty scenarios of radiation exposure require high throughput biological dosimetry techniques for population triage in order to rapidly identify individuals who require clinical treatment. The manual dicentric assay is a highly suitable technique, but it is also very time consuming and requires well trained scorers. In the framework of the MULTIBIODOSE EU FP7 project, semi-automated dicentric scoring has been established in six European biodosimetry laboratories. Whole blood was irradiated with a Co-60 gamma source resulting in 8 different doses between 0 and 4.5Gy and then shipped to the six participating laboratories. To investigate two different scoring strategies, cell cultures were set up with short term (2-3h) or long term (24h) colcemid treatment. Three classifiers for automatic dicentric detection were applied, two of which were developed specifically for these two different culture techniques. The automation procedure included metaphase finding, capture of cells at high resolution and detection of dicentric candidates. The automatically detected dicentric candidates were then evaluated by a trained human scorer, which led to the term 'semi-automated' being applied to the analysis. The six participating laboratories established at least one semi-automated calibration curve each, using the appropriate classifier for their colcemid treatment time. There was no significant difference between the calibration curves established, regardless of the classifier used. The ratio of false positive to true positive dicentric candidates was dose dependent. The total staff effort required for analysing 150 metaphases using the semi-automated approach was 2 min as opposed to 60 min for manual scoring of 50 metaphases. Semi-automated dicentric scoring is a useful tool in a large scale radiation accident as it enables high throughput screening of samples for fast triage of potentially exposed individuals. Furthermore, the results from the participating laboratories were comparable which supports networking between laboratories for this assay.

Biological dosimetry assessments of a serious radiation accident in Bulgaria in 2011.

In 2011, a serious radiation accident occurred in Stamboliyski, Bulgaria, in an industrial sterilisation facility using very-high-activity (60)Co sources. For the five persons accidentally exposed, biological dosimetry based on dicentric analysis was performed in Sofia and in Paris, where the patients were transferred for treatment. Before completing the chromosomal dose assessment, and for the most exposed person, a preliminary cytogenetic evaluation based on electronically transmitted metaphase images was made. The averaged acute whole-body dose estimates for the five patients ranged from 5.2 to 1.2 Gy, and good agreement was obtained between the two laboratories. The patients were also assessed by their prodromal responses and depressed blood cell counts over the first week. The cytogenetic dose estimates were in good accord with those derived from the blood counts, and both techniques indicated that, for the two most seriously exposed persons both techniques indicated that the initial prodromal reactions had suggested somewhat less severe exposure.