Radiotherapy treatment of mouse tumor and impact of beam energy on nearest organs: A Monte Carlo investigation

摘要

The aim of the present work was to investigate the absorbed dose in a target lung tumor, in its surrounding tissues and in neighboring organs not traversed by radiation beams during a small animal X-rays radiotherapy treatment by means of Monte Carlo simulations (MCS). A digital mouse phantom was irradiated by 7 X-ray spectral beams targeting the tumor with energies of 50, 100, 150, 200, 250, 350 and 450 kVp. Each energy beam was directed towards the tumor from 7 different angles to reduce energy deposit in normal tissue. To examine dose behavior, 10 volumes of interest (VOIs) were considered in the lung tumor and its surrounding tissues, in the lungs, the heart, the spinal bone and spinal cord. The results showed that by raising beam energy, the tumor as well as the other VOIs had similar absorbed dose behavior. The absorbed dose was high at 50 kVp and started decreasing until 150 kVp, then it uniformly increased until 450 kVp, except for the spinal cord where the absorbed dose was continuously decreasing from 50 to 450 kVp. The absorbed dose calculated here depended on the whole body of the mouse as the photons interacted in the heterogeneous body of the mouse before energy deposit in a VOI. In conclusion, MCS present a useful tool for small animal radiotherapy treatment planning allowing the optimization of the absorbed dose in the target and in the secondary organs as function of beam energy and of incident beam angles.