effect of tissue composition on dose distribution in electron beam radiotherapy

objective: the aim of this study is to evaluate the effect of tissue composition on dose distribution in electron beam radiotherapy. methods : a siemens primus linear accelerator and a phantom were simulated using mcnpx monte carlo code. in a homogeneous cylindrical phantom, six types of soft tissue and three types of tissue-equivalent materials were investigated. the tissues included muscle (skeletal), adipose tissue, blood (whole), breast tissue, soft tissue ( 9-components ) and soft tissue (4-component). the tissue-equivalent materials were water, a-150 tissue-equivalent plastic and perspex. electron dose relative to dose in 9-component soft tissue at various depths on the beam’s central axis was determined for 8, 12, and 14 mev electron energies. results: the results of relative electron dose in various materials relative to dose in 9-component soft tissue were reported for 8, 12 and 14 mev electron beams as tabulated data. while differences were observed between dose distributions in various soft tissues and tissue-equivalent materials, which vary with the composition of material, electron energy and depth in phantom, they can be ignored due to the incorporated uncertainties in monte carlo calculations. conclusion : based on the calculations performed, differences in dose distributions in various soft tissues and tissue-equivalent materials are not significant. however, due to the difference in composition of various materials, further research in this field with lower uncertainties is recommended.