Majallah-i Dānishgāh-i ’Ulūm-i Pizishkī-i Īlām (May 2018)
Increasing The Absorbed Dose in Photon Activation Therapy in the Labeled Tissue by Gold and Lutetium
Abstract
Introduction: The Increase in cancer tissues dose while protecting the surrounding healthy tissues is regarded a great challenge in radiotherapy. Photon Activation Therapy (PAT), by introducing high-Z elements to tumor, can enhance the delivered dose in tumor tissues while reducing the dose deposited in adjacent normal tissues. In this study, the effects of various parameters such as X-ray energy, type and concentration of the activation agents in the dose distribution have been investigated to improve the quality of treatment by Geant4 simulation code. Materials & Methods: In this study, the effects of introducing Au and Lu in targeted tissues irradiated by X-ray beam have been investigated by Geant4 code. In the designed model, the x-ray source was considered in the shape of a circular plate with the radius of 0/5cm and the phantom in cubic shape with the side of 15cm. Rectangular cubic shape detector dimensions are 3×3×7.5 cm3 and the assumed tumor in cubic shape with the side of 1cm are located inside it. Findings:: The simulation results were obtained with different voltages of X-ray generator in labeled tumor by Au and Lu (with two concentrations of 5 and 10 wt. %). Optimum voltage of x-ray generator in order to maximum Dose Enhancement Factor (DEF) by Au was 100kV, while it was observed at 100kV and 160kV for Lutetium. Increasing the absorbed dose for tumor region could reveal the effective role of contrast agents. Furthermore, when the concentration of contrast agents was doubled, average of DEF at the optimum voltage of X-ray generator and in the tumor region, was 1.68 & 1.76 for Au and Lu, respectively. Discussion & Conclusions: Based on the results, the absorbed dose in tumor region after introduction of contrast agents with specifying the optimum concentration and photon energy can be increased selectively. This approach of introducing contrast agents could improve the efficiency in the cancerous cells therapy.
