The separate contributions of all source regions to organ doses from 131I and 123I administered to the bodywere calculated using voxelized reference phantoms. The photon and electron components oforgan doses were also evaluated for each source region. The MCNPX Monte Carlo particletransport code was utilized for dose calculations. All organs and tissues of male andfemale phantoms were taken into account as source regions with their correspondingcumulated activities. The results showed that cumulated activities assigned to sourceregions and inter-organ distances were two factors that strongly affected the contributionof each source to the organ dose. The major contribution of the dose to the main sourceregions arose from self-irradiation of electrons, while for nearby organs it was due tophotons emitted by the main source organs. In addition, self-irradiation plays animportant role in the dose delivered to most target organs for lower thyroid uptakes.

In case of accidental exposure to radiation, it is necessary to establish as soon aspossible a dosimetry report for each victim. In most cases, this report is based onmedical images of the victim, enabling the construction of a personalized realisticnumerical model, also called a voxel phantom. Unfortunately it is not always possible toperform the medical imaging of the victim since the technology may be unavailable or toavoid additional exposure to radiation. In such cases, the commonly used method is torepresent the victim with a numerical model like the “Reference Man”, a voxelized phantomrepresentative of the average male individual. The treatment accuracy depends on thediagnosis precision and, consequently, on the similarity of the phantom and/to the victim.A precise dosimetry evaluation requires a personalised and realistic phantom whosebiometric characteristics match the victim; such model is often unavailable. TheCase-Based Reasoning (CBR) is a problem solving method for the conception of intelligentsystems. It imitates the analysis, understanding and reconstruction of the humanintelligence. The ReEPh project (Research of Equivalent Phantom) proposes to use the CBRprinciples to retrieve from a set of phantoms, the most adapted one to the irradiatedvictim. For this study, the ReEPh platform retrieves, stores and compares existingphantoms to a victim. A graphic interface enables the user to compare victim’scharacteristics to the ones of the most similar phantoms available in the database. Thisdefines a similarity index presenting the equivalence between the victim and the suggestedphantom. Moreover, a confidence index is also assessed to define the uncertainty impliedby the RaPC choice procedure.

Dans le cadre de l’amélioration des techniques d’étalonnage en anthroporadiamétrie, le Laboratoire d’Évaluation de la Dose Interne de l’IRSN a développé un outil numérique, « OEDIPE », pour modéliser la contamination interne dans des fantômes numériques voxélisés, simuler la mesure anthroporadiamétrique et estimer la dose interne. Si la précédente version d’OEDIPE permettait de bien modéliser des géométries de source comprenant un seul radionucléide localisé dans un organe particulier, elle était cependant limitée pour la modélisation d’une contamination formée d’un mélange de radionucléides dont la localisation évolue à partir de l’incorporation pour se distribuer dans plusieurs organes. Cet article a pour but de décrire les nouveaux modules développés pour permettre la définition de sources hétérogènes en composition et en répartition ainsi que l’importation automatique de distributions d’activité dérivées du calcul biocinétique. Ces nouveaux outils vont permettre d’étudier des cas de contamination plus complexes et l’influence de la biocinétique en mesure in vivo, afin de mieux estimer les coefficients d’étalonnage et les incertitudes correspondantes.