Biomedical subjects

I Thierry-Chef

Publications and source records attributed to I Thierry-Chef.

5 recordsLinked to original sources

PubMed2006

External dose estimation for nuclear worker studies.

Epidemiological studies of nuclear workers are an important source of direct information on the health effects of exposure to radiation at low doses and low dose rates. These studies have the important advantage of doses that have been measured objectively through the use of personal dosimeters. However, to make valid comparisons of worker-based estimates with those obtained from data on A-bomb survivors or persons exposed for medical reasons, attention must be given to potential biases and uncertainties in dose estimates. This paper discusses sources of error in worker dose estimates and describes efforts that have been made to quantify these errors. Of particular importance is the extensive study of errors in dosimetry that was conducted as part of a large collaborative study of nuclear workers in 15 countries being coordinated by the International Agency for Research on Cancer. The study, which focused on workers whose dose was primarily from penetrating gamma radiation in the range 100 keV to 3 MeV, included (1) obtaining information on dosimetry practices and radiation characteristics through the use of questionnaires; (2) two detailed studies of exposure conditions, one of nuclear power plants and the other of mixed activity facilities; and (3) a study of dosimeter response characteristics that included laboratory testing of 10 dosimeter designs commonly used historically. Based on these efforts, facility- and calendar year-specific adjustment factors have been developed, which will allow risks to be expressed as functions of organ doses with reasonable confidence.

Artifacts↗

PubMed2005

Risk of cancer after low doses of ionising radiation: retrospective cohort study in 15 countries.

OBJECTIVES: To provide direct estimates of risk of cancer after protracted low doses of ionising radiation and to strengthen the scientific basis of radiation protection standards for environmental, occupational, and medical diagnostic exposures. DESIGN: Multinational retrospective cohort study of cancer mortality. SETTING: Cohorts of workers in the nuclear industry in 15 countries. PARTICIPANTS: 407 391 workers individually monitored for external radiation with a total follow-up of 5.2 million person years. MAIN OUTCOME MEASUREMENTS: Estimates of excess relative risks per sievert (Sv) of radiation dose for mortality from cancers other than leukaemia and from leukaemia excluding chronic lymphocytic leukaemia, the main causes of death considered by radiation protection authorities. RESULTS: The excess relative risk for cancers other than leukaemia was 0.97 per Sv, 95% confidence interval 0.14 to 1.97. Analyses of causes of death related or unrelated to smoking indicate that, although confounding by smoking may be present, it is unlikely to explain all of this increased risk. The excess relative risk for leukaemia excluding chronic lymphocytic leukaemia was 1.93 per Sv (< 0 to 8.47). On the basis of these estimates, 1-2% of deaths from cancer among workers in this cohort may be attributable to radiation. CONCLUSIONS: These estimates, from the largest study of nuclear workers ever conducted, are higher than, but statistically compatible with, the risk estimates used for current radiation protection standards. The results suggest that there is a small excess risk of cancer, even at the low doses and dose rates typically received by nuclear workers in this study.

Dose-Response Relationship, Drug↗

PubMed2005

[Radiation doses received by premature babies in the neonatal intensive care unit].

PURPOSE: Because of frequent radiological investigations performed in neonatal intensive care unit, a dosimetry study was carried out to assess the level of doses received by premature babies. MATERIALS AND METHODS: In vivo measurements were performed and effective doses were evaluated for single radiographs. Individual cumulative doses received over the period of stay were then estimated, for each premature baby entering the intensive care unit in 2002, taking into account the number of radiographs they underwent. RESULTS: On average, babies stayed for a week and more than one radiograph was taken per day. Results showed that, even if average doses per radiograph were relatively low (25 microSV), cumulative doses strongly depended on the length of stay, and can reach a few mSv. CONCLUSION: Even if doses per radiograph are in agreement with European recommendations, optimisation of doses is particularly important because premature babies are more sensitive to radiation than adults and because they usually undergo further radiological examinations in other services. On the basis of the results of this dosimetry study, the implementation of a larger study is being discussed.

Age Factors↗

PubMed2002

Study of a selection of 10 historical types of dosemeter: variation of the response to Hp(10) with photon energy and geometry of exposure.

An international collaborative study of cancer risk among workers in the nuclear industry is tinder way to estimate direetly the cancer risk following protracted low-dose exposure to ionising radiation. An essential aspect of this study is the characterisation and quantification of errors in available dose estimates. One major source of errors is dosemeter response in workplace exposure conditions. Little information is available on energy and geometry response for most of the 124 different dosemeters used historically in participating facilities. Experiments were therefore set up to assess this. using 10 dosemeter types representative of those used over time. Results show that the largest errors were associated with the response of early dosemeters to low-energy photon radiation. Good response was found with modern dosemeters. even at low energy. These results are being used to estimate errors in the response for each dosemeter type, used in the participating facilities, so that these can be taken into account in the estimates of cancer risk.

Calibration↗

PubMed2001

A method to assess predominant energies of exposure in a nuclear research centre--Saclay (France).

A study of dosimetric errors is under way within an international collaborative study of cancer risk among workers in the nuclear industry. The objective is to quantify errors in the estimated photon doses to individual organs used for cancer risk estimation. One source of errors is the response of old dosemeters in workplace exposure conditions. As these conditions are not well known, the International Study must rely on expert estimations. This paper describes a method to assess the proportion of the dose from photons in three energy ranges (< 100, 100-300, > or = 300 keV) using the responses under filters of a multi-element dosemeter. The method was tested on experimental and simulated data and provides a good estimate of the proportion of dose from photons below 100 keV, the most critical for dosemeter response. It was applied to personnel readings in one facility, confirming the experts' estimation. Beyond the International Study, the method has implication for the monitoring and protection of workers.

Female↗