Validation by experimental measurement of OEDIPE, tool for patient-specific dosimetry

Dose assessment is needed for each patient treated by targeted radiotherapy as well as for subject contaminated by inhalation, wound or ingestion. To reach the precision required in such cases, a dosimetric method based on the MCNPX Monte-Carlo particles transport code was developed. The anatomy of each patient or contaminated subject is taking into account as a voxelized geometry created from computed tomography (CT) images or magnetic resonance images (MRI). This tool, called OEDIPE (French acronym standing for tool for personalized internal dose assessment) allows to realize dosimetric studies at both the organ and voxel scales. The validation of such a tool is complex because of the numerous sources of the dose calculation variations: calculation methods, definitions and representativeness of the geometry. The study presented here is aimed at validating the OEDIPE tool by comparison of its results with experimental data obtained with thermoluminescent dosimeters (TLD) threads. Comparison between the calculated and experimental mean dose values is satisfying. Nevertheless, the spatial dose distributions calculated and measured along the TLD threads, while delivering comparable schemes, show significant differences. Those are due to the fact that it is impossible to exactly associate a thread portion with a given voxel. (authors)