Majallah-i Dānishgāh-i ’Ulūm-i Pizishkī-i Shahīd Ṣadūqī Yazd (Nov 2016)
Study of Dose Distribution 103Pd Source Brachytherapy in Treatment of Cancer Adjacent to Fat and Muscle Tissues by the Monte Carlo method using MCNP4C code
Abstract
Introduction: The dosimetry of the brachytherapy sources is performed in the water source medium according to protocol TG-43U1. To achieve a resonable results on treatment, the use of the water material for all body tissues can be one of the faulty sources in delivering the correct dose to the tumor. Thus, we have focused on the dosimetry parameters in fat density 0.95 gr/cm3 and the muscle with density 1.05 gr/cm3 in the present study. The results are compared with the results of the water phantom to show the accurate accessment via the differences of the results. Methods: Dissymmetry simulations for determining the parameters of the radial dose function and the anisotropy function in fat tissues, muscle and water phantom distances and different angles has been using MCNP4C code. Results: The greatest relative differences of the phantom radial dose function of the fat tissue at distances below 1cm approximately reached 13%; and this rate increased, when the distance from the source increased; whereas at the distance of 5cm from the source, it approximately reached 167%. In the muscle tissue, the relative difference of these parameters was about 3% at the distance of 0.5cm, while at the distance of 5cm from the source, it approximately increased 16%. The maximum relative difference of the anisotropy parameter of the fat and muscle tissue phantom compared with the water were observed more than 2% and 3%, respectively. Conclusion: In the clinical application of the 103Pd brachytherapy source, which is contracted in the treatment of the adjacent malignant tumors to the fat and muscle tissues, the correct decisions must be applied on the tissue dosimetry parameters in the treatment planings according to the tables of 3, 4, 5 and 6 in this study.
