Dosimetric study of density variation with Isogray TPS

Introduction: Dosimetry in external radiotherapy is based on the use of images from computed tomography (CT), previously calibrated, by assuming that the electronic density is comparable to the mass density. However, the magnetic resonance imaging (MRI), in particular diffusion tensor imaging, shows significant heterogeneity reflecting variations in density within the tumor, for example in a glioblastoma [ [1] Ken S. Franceries X. Lotterie J.A. Lubrano V. Catalaa I. Cassol E. et al. Integration of processed 3D magnetic resonance spectroscopy maps into the treatment planning system for radiotherapy target volume delineation of glioblastoma. Radiat Oncol. 2015; (in press) Google Scholar ]. The purpose of this study was to evaluate the influence of fine variations of mass density within the tumor and/or identifiable structures [ [2] Papanikolaou N. Battista J. Boyer A. Kappas C. Klein E. Mackie T. et al. Tissue inhomogeneity corrections for megavoltage photon beams. 2004 Google Scholar ] in diffusion MRI dosimetry study, by quantifying the impact it could have on changes to the 3D distribution of the absorbed dose.