JIN Haoª²Yu, ZHOU Lingª²Hong, CHEN Guangª²Jie, CHEN Chaoª²Min

    School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China

    ¡¾Abstract¡¿ AIM: To develop a photon virtual source model for simulating arbitrary, external beam, and calculating intensity distributions using Monte Carlo method. METHODS: The source model consisted of a photon fluence grid composed of a matrix of square elements, located 20ª²cm downstream from the linear accelerator target. The fluence map was reconstructed from fluence and energy spectra acquired by modeling components of the linear accelerator treatment head using the Monte Carlo code BEAMnrc. RESULTS: Depth dose and profile source calculations for 6ª²MV photon beams, for 3 standard square field sizes, were in good agreement with measurement. Irregular field calculations compared with film measurement showed that good agreement was observed in the 90%, and 50% isodose regions, however, differences were noted in the 10% region. CONCLUSION: The photon virtual source model is suitable of accurately simulating arbitrary, external beam, and calculating intensity distributions. ......