Abstract
In breast cancer, radiotherapy represents the most effective adjunct to surgery to prevent locoregional recurrences. Serious side-effects following breast cancer radiotherapy are dermatosis and pulmonary. An underdosage as a result of a gap can contribute to tumor recurrence. How to avoid excess dose is a topic of tumor treatment. We probe into the dose distribution of electron and electron-photon irradiation of breast for clinical treatment.Simulation in this study is carried out by the OMEGA/BEAMnrc code. It is used to simulate the linear accelerator to make phase space files. We use the results of simulation to compare with the experiment. The phantom is included by acrylic, bone-like tissue and air. Siemens PRIMUS accelerator radiates 6 MV photon and 6 MeV electron to phantom with CEA TVS negative for dose distribution study. Simulation of dose distribution is calculated by DOSXYZnrc with phase space files.Results show a good agreement between measurement and simulation. The dose of bone was about 37% more than tissue by 6 MeV electron beam, 20x20 cm2 filed size, and 2.0 cm depth. The overdose is 45%, 40% and 0% on overlap in 1 cm, 0.5 cm and 0 cm by 6 MeV electron beam, 10x10 cm2 filed size and 0.5 cm depth and 6 MV photon beam, 10x10 cm2 filed size and 0.5 cm depth in electron-photon interface. The underdose is 20% and 54% on gap in 0.5 cm and 1 cm by 6 MeV electron beam, 10x10 cm2 filed size and 0.5 cm depth and 6 MV photon beam, 10x10 cm2 filed size and 0.5 cm depth in electron-photon interface. An acceptable error occurs on air edge of phantom. The air gap between each acrylic square is the cause of error.We can study the characteristics of beam in phase space file for the good agreement between measurement and simulation. Measurement of electron or photon contamination in photon beam or electron beam is possible. All of the dose distribution in phantom is measurable, too. Monte Carlo is used to study what is difficult to measure. Monte Carlo simulation is going to be used clinically due to the advance of computer technology.