Monte Carlo Simulation of Dose Absorption of Nano-Particles-Labeled Tissues Used in X-Ray Microbeam Radiation Therapy

One of the most important measures of therapeutic quality in Microbeam Radiation Therapy (MRT) is the Peak to Valley Dose Ratio (PVDR). This parameter is a criterion to evaluate ablation of cancerous cells and sparing of normal cells in tumor and in its surrounding region. The aim of this work is to study the influence of using gold and gadolinium nano-particles as contrast agents on dose distribution and PVDR when a phantom is irradiated by a typical micro-planar X-ray beam of European Synchrotron Radiation Facility (ESRF3). Using Geant4 computer code, a model has been designed to simulate depth dose in an intact phantom made of PMMA4 and dose distribution in a phantom containing assumed tumors in therapeutic techniques of MIMRT5 and BIMRT6. Comparison of simulated results in the intact phantom with the measured values of depth dose reveals the validity of our simulation with the designed model. To improve the efficiency of MRT, enhancement of absorbed dose in tumor tissues and sparing of normal tissues due to presence of contrast agents have been studied. The obtained results show that the enhancement is more noticeable for Au at the peak region and for Gd in the valley region. This approach of introducing contrast agents in MRT could hopefully prepare new treatment planning and improves the efficiency of tumor therapy.