Determination of mass attenuation coefficient by numerical absorption calibration with Monte-Carlo simulations at 59.54 keV

International audienceThis study presents a numerical method in order to determine the mass attenuation coefficient of a sample with an unknown chemical composition at low energy. It is compared with two experimental methods : a graphic method and a transmission method. The method proposes to realise a numerical absorption calibration curve to process experimental results. Demineralised water with known mass attenuation coefficient (0.2066 cm 2 .g −1 at 59.54 keV) is chosen to confirm the method. 0.1964 ± 0.0350 cm 2 .g −1 is the average value determined by the numerical method, that is to say less than 5% relative deviation compared to more than 47% for the experimental methods

Determination of plutonium in nitric acid solutions using energy dispersive L X-ray fluorescence with a low power X-ray generator

International audienceThis work presents the development of an in-line energy dispersive L X-ray fluorescence spectrometer setup , with a low power X-ray generator and a secondary target, for the determination of plutonium concentration in nitric acid solutions. The intensity of the L X-rays from the internal conversion and gamma rays emitted by the daughter nuclei from plutonium are minimized and corrected, in order to eliminate the interferences with the L X-ray fluorescence spectrum. The matrix effects are then corrected by the Compton peak method. A calibration plot for plutonium solutions within the range 0.1-20 g.L −1 is given

Well GeHP detector calibration for environmental measurements using reference materials

International audienceA well-type detector installed in the Modane underground Laboratory (LSM) can combine both low background and high detection efficiency and it is well suited for the analysis of small amounts of environmental samples. Reference materials such as IAEA-447 (moss-soil), IAEA-RG-Th1 and IAEA-RG-U1 were used for the detector calibration, owing to a chemical composition close to those of the environmental samples. Nevertheless , the matrix effects and the true coincidence summing effects must be corrected from the full energy peak efficiency (FEPE). The FEPE was performed for a wide range of energy by a semi-empirical method using Monte Carlo simulation (MCNP6), intended for environmental measurements such as lake sediments dating. In the well geometry, the true coincidence summing effects could be very important and correction factors have been computed in three different ways

Mesures de spectrométrie et de dosimétrie neutron aux postes de travail pour l'étalonnage de dosimètres individuels PGP-DIN

International audience(ManuAcrit r e p le 3 juillet 2002, accepté le 29 septembre 2002) Dans le cadre de la mise en application des recommandations décrites dans la publication 60 de la CIPR, des mesures de spectrométrie neutron ont été réalisées à plusieurs postes de travail au CEA de Valduc. Le but de ces mesures était la détermination de nouveaux coefficients d'étalonnage h affecter aux dosimètres individuels neutron PGP-DIN afin de restituer correctement les doses reçues par les opérateurs séjournant h ces postes. Ces mesures ont été effectuées au cours de deux campagnes successives. La tluence neutronique et le débit d'équivalent de dose amhiantH*(IO) ont été mesurés en fonction de l'énergie avec le spectromètre ROSPEC et un système de sphères de BONNER. Les champs de radiations étant toutefois mixtes, c'est-à-dire présentant une composante neutronique et photonique, des mesures de débits d'équivalent de dose ambiant photon aux postes de travail considérés ont également été réalisées à l'aide de débitmètres d'ambiance. Les dosimètres individuels PGP-DIN ont été positionnés sur un fantôme (ISO) d'eau. Des calculs effectués h l'aide du code MCNP ont été comparés aux résultats expérimentaux. Neutron spectrometry and dosimetry measurement at workplaces for calibration of individual PGP-DIN dosimeters. Measurements to determine new coefficients for individual neutron dosimeters PGP-DIN complying with the ICRP 60 recommendations were performed at two workplaces at the CEA of Valduc: a storage r w m and a plutonium reprocessing plant. Two spectrometry campaigns were performed allowing a better assessment of doses received by operators worki.ng at these workplaces. Neutron energy fluence and ambient dose equivalent rate H*(10) distributions were measured as function of neutron energy by using the ROSPEC device and BONNER spheres spectrometer. The radiation field being mixed neutron and gamma, the gamma component was also evaluated: neutron and photon dose-rate meters were nsed to evaluate the ambient dose rate equivalent. Individual dosemeters were positioned on an ISO water slab phantom. In addition, calculations were performed using the MCNP simulation code for different configurations. ' Insiitui de radioprotection ct de sûre16 nucléaire, DPHD, B.P. 17. 92262 Fontcnay-aux-Roses Cedcx, France

Trastuzumab-associated cardiac adverse effects in the Herceptin adjuvant trial.

PURPOSE: The purpose of this analysis was to investigate trastuzumab-associated cardiac adverse effects in breast cancer patients after completion of (neo)adjuvant chemotherapy with or without radiotherapy. PATIENTS AND METHODS: The Herceptin Adjuvant (HERA) trial is a three-group, multicenter, open-label randomized trial that compared 1 or 2 years of trastuzumab given once every 3 weeks with observation in patients with HER-2-positive breast cancer. Only patients who after completion of (neo)adjuvant chemotherapy with or without radiotherapy had normal left ventricular ejection fraction (LVEF > or = 55%) were eligible. A repeat LVEF assessment was performed in case of cardiac dysfunction. RESULTS: Data were available for 1,693 patients randomly assigned to 1 year trastuzumab and 1,693 patients randomly assigned to observation. The incidence of trastuzumab discontinuation due to cardiac disorders was low (4.3%). The incidence of cardiac end points was higher in the trastuzumab group compared with observation (severe congestive heart failure [CHF], 0.60% v 0.00%; symptomatic CHF, 2.15% v 0.12%; confirmed significant LVEF drops, 3.04% v 0.53%). Most patients with cardiac dysfunction recovered in fewer than 6 months. Patients with trastuzumab-associated cardiac dysfunction were treated with higher cumulative doses of doxorubicin (287 mg/m(2) v 257 mg/m(2)) or epirubicin (480 mg/m(2) v 422 mg/m(2)) and had a lower screening LVEF and a higher body mass index. CONCLUSION: Given the clear benefit in disease-free survival, the low incidence of cardiac adverse events, and the suggestion that cardiac dysfunction might be reversible, adjuvant trastuzumab should be considered for treatment of breast cancer patients who fulfill the HERA trial eligibility criteri

Simulation of a Microdosimetry Problem: Behavior of a Pseudorandom Series at a Low Probability

The carcinogenic effects for low dose irradiations are not very well known. Estimations usually are made based on the effects observed at high doses that are then extrapolated to low doses. To estimate low dose effects, the ICRP (International Commission on Radiological Protection) uses a linear extrapolation matched with a dose-rate reduction factor equal to two. This proportionality of the effect and dose, even for the lowest doses and dose-rates, leads to two assumptions which must be questioned : 1. the efficiency of DNA repair in cells does not vary with the dose and the dose-rate, 2. when one single particle crosses one single cell, a carcinogenic transformation may occur. Low doses are frequently generated by fast electrons at low fluence. We must consider the irradiated medium as an assembly of targets and the cross section as a representation of the probable interaction between the incident particle and the target. Biologically, cells contain internal structures which are the sensitive elements. Physically, a hit is interpreted as a registered event caused by a particle passing through the sensitive site. The Poisson law describes the statistic behavior of this event: P(x) = (e–m/x!) mx (1) where P(x) is the realization probability of the event x and m represents the average hits per target (ratio of the number of hits per number of targets). For example, consider that a flux of exactly 106 particles/cm2 reaches a cell population whose sensitive elements have a geometric cross section of 100 μm2. The average number of particles per cell will be one, but according to the Poisson statistics, about 37% of the cells will survive (0 hits), about 37% of the cells will be hit only once and 26% will be hit twice or more. This problem can be extended to the response of many radiation detectors—one-hit or multi-hits detectors

Annual effective dose and excess life time cancer risk assessment from tobacco plants

International audienceCigarette smoking is one of the pathways that might cause radiation exposure due to the presence of radioactive elements in tobacco leaves used in the manufacture of cigarettes. From the health point of view, the knowledge of radioactivity content of the various radionuclides in tobacco leaves and their derivative products is important to assess the radiological effects associated with tobacco smoking for smokers. In this work, naturally occurring radionuclides 226 Ra, 232 Th and 40 K and man-made 137 Cs were measured in tobacco using gamma-ray spectrometry. Results show that the average concentrations of 226 Ra, 232 Th and 40 K vary from 4.30 ± 0.2 to 11.85 ± 0.7 (average 8.17), 1.35 ± 0.1 to 16.12 ± 0.9 (average 6.08), and 565.6 ± 15.5 to 1235.81 ± 35 (average 908.09) Bq kg −1 , respectively. 137 Cs activity concentrations were ranged from 0.15 ± 0.01 to 0.67 ± 0.9 (average 0.44) Bq kg −1. The most important radiological parameters, including radium equivalent (Ra eq), total annual effective dose (AED) and excess lifetime cancer risk (ELCR) were calculated. For smokers, the total AED resulting from activity concentrations of 226 Ra, 232 Th and 40 K in tobacco samples ranged from 0.44 to 2.29 (average 1.39) mSv y −1 , while of 137 Cs varied from 0.01 to 0.04 (average 0.025) Sv y −1 and so very little is contributing to the total dose due to inhalation to smokers. ELCR was higher than the world's average of 1.45 × 10 −3 for tobacco and coal samples. The excess lifetime cancer risk ranged from 1.55 × 10 −3 to 8.01 × 10 −3 with an average value of 4.88 × 10 −3 for all tobacco samples under investigation

Evaluation of radionuclide concentrations and external gamma radiation levels in phosphate ores and fertilizers commonly used in Algeria

International audienc

Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam

International audienceWe report the design of a millimeter-sized parallel plate free-air ionization chamber 10 (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors nec-essary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy 15 for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL and FLUKA). Measure-ments of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte-Carlo calculations. We show that the developed ionization chamber makes it 20 possible to determine accurate photon fluence rates in routine work and will consti-tute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays