The use of Monte Carlo method in patient dose calculation of prostate brachytherapy

The purpose of this study is to determine whether there is a significant difference between the radiation dose calculations performed in the water medium and real prostate cancer-diagnosed patient through using BrachyDose Monte Carlo code. The radiation dose calculations in this study were made through Monte Carlo particle simulation in three-dimensional phantom geometry obtained from CT images of a patient diagnosed with prostate cancer. The minimum D90 values of prostate tissue and water medium are calculated as 10.4%, 13.8% and 8.4% for 125I, 103Pd ve 131Cs brachytherapy seed sources respectively. Since dose distribution around multiple sources placed on the tissue will be different for each patient, it was foreseen that there may be difference between the dose amount given to the patient and the dose values calculated by using TG-43 formalism at the time of treatment planning. Consequently, it was concluded that it is necessary to reorganize TG-43 based dose calculations in treatment planning systems by taking into account organ and tissue materials, or that Monte Carlo based dose calculations programs which take into account this effects should be applied in treatment planning systems for accurate and sensitive dose calculations.