OEDIPE: A Personalized Dosimetric Tool Associating Voxel-Based Models with MCNPX

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Abstract
A new tool, named OEDIPE (a French acronym that stands for "Tool for Personalized Internal Dose Assessment") was developed to carry out personalized internal dosimetry calculations for nuclear medicine (for both therapeutic and diagnostic procedures) and for radiation safety (in the case of internal contamination). It was developed under the PV-Wave visual data analysis system by the Institute of Radioprotection and Nuclear Safety (IRSN) in collaboration with the French Institute of Health and Medical Research (INSERM). This software creates anthropomorphic voxel-based phantoms from computed tomography (CT) and magnetic resonance imaging (MRI) patient images through the use of a friendly graphical user interface (GUI). Several tools have been built-in to allow for image segmentation. Source data, including VOI localization and cumulated activities, are assessed by single photon emission computed tomography (SPECT) images, and the source may be specified in any number of organs either as a point source or a homogeneously distributed source. It is also possible to choose the dosimetric parameters required for the study (mean organ dose or a dose distribution). Phantom, source, and dosimetric parameters are automatically written into a file. That file is then processed by the Monte Carlo code MCNPX (LANL) to perform the actual dose calculation. OEDIPE can compute either the absorbed dose in each organ (in a few minutes), or the absorbed dose in each voxel of the phantom (i.e. the spatial dose distribution at a tissue level) in a few hours or more. OEDIPE automatically reads the MCNPX output file and processes results to give a list of absorbed doses in each organ or a plot of isodose curves superimposed onto the phantom. Because of the long calculation times required to compute an absorbed dose within an entire whole-body phantom at a spatial resolution of a few millimeters, modifications were made to reduce computational times to reasonable values. To illustrate this tool, results of a dosimetric study of technetium-99m labeling of a bone-scanning agent are presented. OEDIPE is a tool that can be used for patient-specific dosimetry--for example, in targeted radiotherapy--by taking into account the individual patient anatomy, including tumors.