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ABSTRACT: Fundamentals of biological dosimetry are described in the International Atomic Energy Agency manual, but all over the world each laboratory is using its own protocol. To test the influence of protocol variations, some blood samples were exposed to 0.5 Gy of gamma radiation and mitotic index and dicentric rates were measured under different experimental conditions. The effect of seven parameters [bromodeoxyuridin (BrdU), phytohaemagglutinin and colcemid concentrations, blood and medium volumes, culture duration and incubation temperature] was tested using a Placket and Burman experimental design. The analysis reveals that the mitotic index was influenced by the concentration of BrdU, medium and blood volumes, the culture duration and the temperature. However, none of the factors has a significant impact on the yield of dicentrics. The dicentric assay is robust against reagent variations within the range tested. These results could be used by relevant laboratories as elements of their procedures robustness in any event requiring such demonstration.
Radiation Protection Dosimetry 02/2012; 151(1):135-43. · 0.82 Impact Factor
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S Roch-Lefèvre,
F Pouzoulet,
A L Giraudet,
Pa Voisin,
A Vaurijoux,
G Gruel,
E Grégoire,
V Buard,
M Delbos, Ph Voisin,
J Bourhis,
L Roy
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ABSTRACT: The purpose of this study was to evaluate the in vivo dose-response relation of chromosome aberration formation and distribution in a context of localised and fractionated radiotherapy. Cytogenetic analysis was applied to eight patients, all treated for the same tumour localisation; the same localisation was used to prevent the variability usually observed between patients treated with radiotherapy and to allow the corresponding roles of the size of irradiation field and of the dose rate to be studied. The yield of dicentrics, centric rings and fragments was measured in blood samples taken before treatment, during the course of radiotherapy and up to 6 months after. After the first fraction of radiotherapy, we observed that the whole-body dose estimated from the yield of dicentrics and rings was higher (0.35+/-0.2 Gy) than the calculated equivalent whole-body dose (0.07+/-0.04 Gy). By contrast, the partial-body dose derived from the Qdr (quotient of dicentrics and rings) model was estimated to be 2.2+/-0.3 Gy, which agreed quite well with the dose delivered to the tumour (2.1+/-0.1 Gy). We also found a correlation between the yield of induced chromosome aberrations and the target field size (p = 0.014). U-value analysis showed that the distribution of dicentrics and rings was overdispersed, despite the fractionation of the exposure, and a positive correlation between the U-value and the dose rate was observed (p = 0.017). Overall, these results suggest that the proportion of undamaged lymphocytes could increase with the dose rate.
The British journal of radiology 09/2010; 83(993):759-66. · 2.11 Impact Factor
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ABSTRACT: To compare translocation rate using either M-FISH or FISH-3 in two patients treated for head and neck cancer, with a view to retrospective dosimetry.
Translocation analysis was performed on peripheral blood lymphocyte cultures from blood samples taken at different times during the radiotherapy (0 Gy, 12 Gy and 50 Gy) and a few months after the end of the treatment (follow-up).
Estimated translocation yield varied according to the FISH technique used. At 50 Gy and follow-up points, the translocation yields were higher with FISH-3 than with M-FISH. This difference can be attributed to three events. First, an increase in complex aberrations was observed for 50 Gy and follow-up points compared with 0 Gy and 12 Gy points. Second, at the end of treatment for patient A, involvement of chromosomes 2, 4, 12 in translocations was less than expected according to the Lucas formula. Third, a clone bearing a translocation involving a FISH-3 painted chromosome was detected.
More translocations were detected with M-FISH than with FISH-3, and so M-FISH is expected to improve the accuracy of chromosome aberration analyses in some situations.
Journal of Radiation Research 10/2007; 48(5):425-34. · 1.68 Impact Factor
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ABSTRACT: The purpose of this study was to examine a new approach to retrospective biological dosimetry, by using a long-term animal model to determine the stability of translocation frequency after in vivo irradiation. While the frequency of dicentrics is known to decrease over time, the persistence of more stable chromosomal aberrations such as translocations could be useful if their stability were definitively proved.
Four monkeys (Macaca fascicularis) were exposed to two different doses of ionizing radiation: 2 Gy whole body irradiation for two and 4 Gy for two others. Blood samples were obtained at various times after irradiation. Both total and two-way translocations were detected by fluorescence in situ hybridization. Translocations were scored in stable cells, that is, those without dicentrics, rings or fragments. The course of translocation frequency was analysed at four time-points: one hour (H1), 2 months (M2), 10 months (M10) and 31 months (M31) after irradiation.
We observed two separate trends in translocation frequency: Total translocation frequency decreased slightly in animals irradiated with a dose of 2 Gy, while two-way translocation frequency was relatively stable in all irradiated animals.
We confirmed the long-term stability of translocations and found that it seems to depend on the type of the translocation recorded. Overall translocations were stable for up to 31 months regardless of dose, but two-way translocations were more stable than those that were non-reciprocal, especially in stable cells.
International Journal of Radiation Biology 08/2006; 82(7):493-502. · 2.28 Impact Factor
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ABSTRACT: In case of accidental overexposure to ionizing radiation, the scoring of dicentrics in lymphocytes from blood is the current reference method to estimate the dose received. When only few individuals are accidentally overexposed, at least 500 cells are scored to have a good estimation of the dose. But such a practice is too time consuming when many people are exposed such as in a radiological emergency. In order to reduce the time required to estimate a dose, specific strategies have been developed in the laboratory.Population triage based on the adaptation of the dicentrics assay: In order to reduce the analysis time it is possible to have a dose estimation based on only 50 cells analysed in an hour with a 95% confidence limit of 1 Gy.Population triage based on the use of image analysis systems: The metaphase finder increases the speed of the scoring by a factor of 2. It is also possible to detect automatically the dicentrics. The system proposes to the operator some candidate dicentrics which are then verified manually. In this case, 50% of the dicentrics are correctly detected with a 95% confidence limit of 0.4 Gy.Establishment of a network: Biological dosimetry laboratories are small, hence their capacity can be overloaded by a large number of suspected overexposed individuals. That is why international and national networks should be established, they should perform periodically intecomparisons and population triage exercises.Population triage based on micronuclei assay: As micronuclei are easier to score than dicentrics, in an hour 500 binucleated cells can be scored resulting in a 95% confidence limit of about 0.5 Gy versus 1 Gy with the dicentric assay. However, the micronuclei technique is not efficient to estimate accurately the dose because it lacks specificity.Use ofγ-H2AX for population triage: This assay is based on the scoring of double-strand breaks. Whereas with the other technique a cell culture is required, here it is possible to estimate a dose 3 h after receiving the sample in the laboratory with a sensitivity below 0.5 Gy. But one major limitation is the decrease of the signal with time. Therefore, this assay can only be used in case of population triage starting within minutes post-exposure.
Radiation Measurements.
