Biomedical subjects

I Clairand

Publications and source records attributed to I Clairand.

11 recordsLinked to original sources

PubMed2006

ESR investigation of joint use of dentin and tooth enamel to estimate photon and neutron dose components of a mixed field.

In the case of mixed photon and neutron field, estimation of photon and neutron dose components from the ESR signal of tooth enamel alone is impossible. To differentiate neutron and photon components using the method described in ICRU 26 for twin chambers, enamel and dentin sensitivities to photon and to neutron were investigated. Enamel and dentin relative sensitivities were, respectively, estimated at 0.03 +/- 0.02 and 0.14 +/- 0.10 for fission neutrons. Basing on this result, calculation of neutron and photon doses was performed in realistic case of criticality accident. Estimation of neutron and photon dose components was found in good agreement with reference dosimetry.

Artifacts↗

PubMed2006

Study of materials for mixed field dosimetry by EPR spectroscopy.

EPR dose reconstruction after accidental photon exposure based on materials irradiated in the vicinity of the victim (sucrose, medicine tablets, etc.) was used successfully in several cases referenced in the literature. However, accidental exposure may also occur with a neutron component such as in the Tokai-Mura criticality accident. The aim of this work is to investigate the potentiality of EPR dosimetry for mixed photon and neutron field exposure with different organic materials already used for photon exposure (sucrose) or with potential dosimetric properties (ascorbic acid, sorbitol, glucose, galactose, fructose, lactose and mannose). To assess the neutron sensitivity, the materials were exposed to a mixed radiation field of an experimental reactor with different neutron to photon ratios. The relative neutron sensitivity was found to range from 12 to 43% according to the materials. The potentiality of these materials for mixed field EPR dosimetry is discussed.

Carbohydrates↗

PubMed2005

Dosimetric comparison of Monte Carlo codes (EGS4, MCNP, MCNPX) considering external and internal exposures of the Zubal phantom to electron and photon sources.

This paper aims at comparing dosimetric assessments performed with three Monte Carlo codes: EGS4, MCNP4c2 and MCNPX2.5e, using a realistic voxel phantom, namely the Zubal phantom, in two configurations of exposure. The first one deals with an external irradiation corresponding to the example of a radiological accident. The results are obtained using the EGS4 and the MCNP4c2 codes and expressed in terms of the mean absorbed dose (in Gy per source particle) for brain, lungs, liver and spleen. The second one deals with an internal exposure corresponding to the treatment of a medullary thyroid cancer by 131I-labelled radiopharmaceutical. The results are obtained by EGS4 and MCNPX2.5e and compared in terms of S-values (expressed in mGy per kBq and per hour) for liver, kidney, whole body and thyroid. The results of these two studies are presented and differences between the codes are analysed and discussed.

Computer Simulation↗

PubMed2005

Current developments at IRSN on computational tools dedicated to assessing doses for both internal and external exposure.

The paper presents the OEDIPE (French acronym that stands for tool for personalised internal dose assessment) and SESAME (for simulation of external source accident with medical images) computational tools, dedicated to internal and external dose assessment, respectively, and currently being developed at the Institute for Radiological Protection and Nuclear Safety. The originality of OEDIPE and SESAME, by using voxel phantoms in association with Monte Carlo codes, lies in their ability to construct personalised voxel phantoms from medical images and automatically generate the Monte Carlo input file and visualise the expected results. OEDIPE simulates in vivo measurements to improve their calibration, and calculates the dose distribution taking both internal contamination and internal radiotherapy cases into account. SESAME enables radiological overexposure doses to be reconstructed, as also victim, source and accident environment modelling. The paper presents the principles on which these tools function and an overview of specificities and results linked to their fields of application.

Academies and Institutes↗

PubMed2004

Exposure of aircraft crew to cosmic radiation: on-board intercomparison of various dosemeters.

Owing to their professional activity, flight crews may receive a dose of some millisieverts within a year; airline passengers may also be concerned. The effective dose is to be estimated using various experimental and calculation tools. The European project DOSMAX (Dosimetry of Aircrew Exposure during Solar Maximum) was initiated in 2000 extending to 2004 to complete studies over the current solar cycle during the solar maximum phase. To compare various dosemeters in real conditions simultaneously in the same radiation field, an intercomparison was organised aboard a Paris-Tokyo round-trip flight. Both passive and active detectors were used. Good agreement was observed for instruments determining the different components of the radiation field; the mean ambient dose equivalent for the round trip was 129 +/- 10 microSv. The agreement of values obtained for the total dose obtained by measurements and by calculations is very satisfying.

Aircraft↗

PubMed2004

Criticality accident dosimetry systems: an international intercomparison at the SILENE reactor in 2002.

In criticality accident dosimetry and more generally for high dose measurements, special techniques are used to measure separately the gamma ray and neutron components of the dose. To improve these techniques and to check their dosimetry systems (physical and/or biological), a total of 60 laboratories from 29 countries (America, Europe, Asia) participated in an international intercomparaison, which took place in France from 9 to 21 June 2002, at the SILENE reactor in Valduc and at a pure gamma source in Fontenay-aux-Roses. This intercomparison was jointly organised by the IRSN and the CEA with the help of the NEA/OCDE and was partly supported by the European Communities. This paper describes the aim of this intercomparison, the techniques used by the participants and the two radiation sources and their characteristics. The experimental arrangements of the dosemeters for the irradiations in free air or on phantoms are given. Then the dosimetric quantities measured and reported by the participants are summarised, analysed and compared with the reference values. The present paper concerns only the physical dosimetry and essentially experiments performed on the SILENE facility. The results obtained with the biological dosimetry are published in two other papers of this issue.

Body Burden↗

PubMed2004

A computational tool based on voxel geometry for dose reconstruction of a radiological accident due to external exposure.

In the case of overexposure to ionising radiation, estimation of the absorbed dose in the organism is an important indicator for evaluating the biological consequences of this exposure. The physical dosimetry approach is based either on real reconstruction of the accident, using physical phantoms, or on calculation techniques. Tools using Monte Carlo simulations associated with geometric models are very powerful since they offer the possibility to simulate faithfully the victim and the environment for dose calculations in various accidental situations. Their work presents a new computational tool, called SESAME, dedicated to dose reconstruction of radiological accidents based on anthropomorphic voxel phantoms built from real medical images of the victim in association with the MCNP Monte Carlo code. The utility was, as a first step, validated for neutrons by experimental means using a physical tissue-equivalent phantom.

Algorithms↗

PubMed2004

PCC-FISH in skin fibroblasts for local dose assessment: biodosimetric analysis of a victim of the Georgian radiological accident.

We propose a new method of biodosimetry that could be applied in cases of localized irradiation. The approach is based on excess chromosome segments determination by the PCC-FISH technique in fibroblasts isolated from skin biopsy. Typically, 0 to 10 Gy ex vivo gamma-irradiated human skin biopsies were dissociated and fibroblasts were isolated and grown for several days. Cells next underwent PCC-FISH painting of whole chromosome 4, and the number of excess chromosome segments per metaphase was determined. An ex vivo reference curve correlating the number of excess chromosome segments per metaphase to the radiation dose was established and used to assess the dose delivered to the skin of one of the victims of the radiological accident that occurred at Lia in Georgia in December 2001. Specifically, the victim suffering from moist desquamation underwent skin excision in Hospital Percy (France). Measurement of excess chromosome segments per metaphase was done in fibroblasts isolated and grown from removed wounded skin and subsequent conversion to radiation doses was performed. The radiation dose map obtained was shown to be in accordance with clinical data and physical dosimetry as well as with conventional biodosimetry. These results demonstrated that PCC-FISH painting applied to skin fibroblasts may be a suitable technique for dose estimation. To assess its worth, this approach needs to be extended to future accidents involving localized radiation exposure.

Apoptosis↗

PubMed2001

Organ weight in 684 adult autopsies: new tables for a Caucasoid population.

The weights of normal organs were retrospectively culled for the years 1987-1991 from 684 forensic autopsy cases. All the subjects were Caucasoid adults who died of external causes and showed no pathological changes. The weights of the following organs were available: the heart, the right and the left lung, the liver, the spleen, the pancreas, the right and the left kidney and the thyroid gland. The external parameters used for statistical correlation were the age, the height, the body weight and the body mass index (BMI) of the deceased. The weight of all the organs was shown to correlate with at least one external parameter, with the exception of thyroids in females. Organ weights decreased with age except for the heart and the thyroid, and increased in relation to body height and/or BMI. Except for the heart, the organ weight showed a better statistical correlation with the body height than the BMI. These updated tables of organ weight were compared with the data collected in previous studies. Such tables have to be regularly updated by pathologists in order to keep organ weight as a good criterion to be used in post-mortem diagnosis.

Adult↗

PubMed2000

Improvement of internal dose calculations using mathematical models of different adult heights.

In internal dosimetry for both nuclear medicine and radiation protection, the adult morphology is represented by a limited number of anthropomorphic models that may not be suitable for all patients. To develop more patient-specific dosimetry, we derived six mathematical models for adults of different height. Three male models (160 cm, 170 cm and 180 cm) and three female models (150 cm, 160 cm and 170 cm), based on the MIRD model design, were developed from the statistical analysis of anthropometric data gathered from autopsies. Monte Carlo calculations were used to provide an example of estimations of S value for these new models for iodine 131 uniformly distributed successively in the stomach or in the urinary bladder. On average, for both male and female models, an increase in the model height of 10 cm leads to a mean reduction in the S value for iodine-131 by 20% and 29% when the stomach and the urinary bladder respectively are selected as source regions. Similarly, when the model height increases by 20 cm, the S values decrease on average by 35% and 48%. This study presents the use of anthropometric data to develop new mathematical models for adults of different height, and shows the significant influence of the morphology on dosimetric parameters.

Adult↗

PubMed1999

DOSE3D: EGS4 Monte Carlo code-based software for internal radionuclide dosimetry.

UNLABELLED: MIRDOSE3 software is currently the main tool available in clinical practice to evaluate absorbed dose in nuclear medicine. Because MIRDOSE3 provides dosimetric parameters for specific anatomic models that cannot be modified by the user, it cannot be used to obtain information concerning metastases or to consider patients whose anatomy differs significantly from that of the standard models. METHODS: To address some of these inconveniences, we developed an original program based on the EGS4 Monte Carlo code, DOSE3D, which calculates dosimetric parameters for anthropomorphic phantoms defined with combinatorial geometry. DOSE3D allows the user to add spheres within the phantom for simulating tumors, to change the shape of one or more organs and, for organs defined by pair, to calculate individual dosimetric parameters for each organ. The program was validated for 131I and 99mTc by calculating S values for the Medical Internal Radiation Dose (MIRD) adult male phantom and comparing these results with data provided by MIRDOSE3. Moreover, two studies were performed to illustrate DOSE3D features. The first one concerned the evaluation of the individual influence of two bone metastases (located in the pelvis and in the lower spine and containing 131I) on testes in terms of S values compared with the influence on testes of other source organs (kidneys, liver, lungs, spleen, thyroid gland and urinary bladder contents). The second study determined the differences of S values between right and left lungs and right and left kidneys when 131I is contained in the liver. RESULTS: The DOSE3D S values were on average within 20% of the MIRDOSE3 results for both radionuclides. Regarding the bone metastases study, S(testes<--metastases) and S(testes<--any source organs) were of the same order of magnitude. In the second study, the S values ratio between right and left organs was 7.7 for the lungs and 5.2 for the kidneys. CONCLUSION: The agreement between DOSE3D and MIRDOSE3 results for most organs shows the validity of DOSE3D. The presented examples of calculation show that DOSE3D could provide additional data to dosimetric parameters given by MIRDOSE3 for a more patient-specific dosimetric approach.

Adult↗