Application of voxel phantoms to study the influence of the heterogeneous distribution of actinides in lungs on in vivo counting using animal experiments

As part of the improvement of calibration techniques for in vivo counting, the Laboratory of Internal Dose Assessment of IRSN has developed a computer tool, “OEDIPE”, to model internal contamination in voxel phantoms, to simulate in vivo counting and to calculate internal dose. This software was used to model the real distribution of activity in the lungs of a baboon analyzed in the Laboratory of Radiotoxicology of CEA. This experiment provided the opportunity to study the influence of the heterogeneity of lung retention on the in vivo counting and to quantify its effect on the assessment of activity by comparison with a simulated homogeneous retention of the same total activity. The results show that the numerical simulation can be a relevant tool to reveal the heterogeneity of lung retention, allowing a determination of calibration factors adapted to heterogeneous contaminations that would be impossible by standard calibration with physical anthropomorphic phantoms.