This paper reports on a new utility for development of computational phantoms for Monte Carlo calculations and data analysis for in vivo measurements of radionuclides deposited in tissues. The individual parameters of each worker can be acquired for an exact geometric representation of his or her anatomy, which is particularly important for low-energy gamma ray emitting sources such as thorium, uranium, plutonium and other actinides. The software discussed here enables automatic creation of an MCNP input data file based on computed tomography (CT) scanning data. The utility was first tested for low- and medium-energy actinide emitters on Livermore phantoms, the mannequins generally used for lung counting, in order to compare the results of simulation and measurement. From these results, the utility's ability to study uncertainties in in vivo calibration were investigated. Calculations and comparison with the experimental data are presented and discussed in this paper.

The aim of this paper is to describe the dosimetric evaluation of a point contamination that occurred in a laboratory during the examination of an irradiated sample. The incident led to point contamination of the operator's finger due to the presence of mainly 106Ru, with its progeny, 106Rh. The paper reports on the activity and dose assessment, performed using several methods. The measured activity was obtained using a conventional device based on a germanium detector and confirmed using software developed at IRSN, based on reconstruction of voxel phantom associated with the Monte Carlo N-Particle code (MCNP) for in vivo measurement. Two dose assessment calculations were performed using both analytical and Monte Carlo methods, applying the same approach as for activity assessment based on the personal computational phantom of the finger. The results are compared, followed by a discussion on the suitability of the tools described in this study.

Although great efforts had been made to improve the physical phantoms used for calibrating in vivo measurement systems, for technical reasons they can oniy provide a rough representation of human tissue. Substantial corrections m w t therefore be made to calibration factors obtained with such caiibration phantoms for extrapolation to a given individuai. These corrections are particularly crucial and delicate in low-energy in vivo measurement when absorption in tissue is significant. To improve caiibration for such special conditions, the posîibility has been raised of using voxelised numerical phantoms associated with Monte Carlo computing techniques. In the method described below, a mathematical phantom, consisting of a voxelised representation derived from scanner images is used, with a specially-designed interface making it possible to not only reconstruct widely-differing contamination confgurations and specify associated tissue compositions, but also automatically create an MCNP4b input file. After validation of the different sources and geometries, the complete procedure of reconstruction of the phantom and simulation of "'Am lung measurement was carried out using a tissue equivalent calibration phantom of the type commoniy used for lung calibration for actinides. The purpose of this work was to extend the use of this principle to the reconstruction of numerical phantoms on the basis of physiological data of individuak obtained from maguetic resonance and scanner images. The resulîs obtained and the current limitations of this approach in the context are discussed. Développement de fantômes numériques voxélisés associé au code Monte Carlo MCNP : application à la mesure anthroporadiamétrique.