Characteristics Analysis of High Energy External Radiotherapy Beams in Water

Abstract

High energy external radiotherapy beam is being used widely for cancer treatment. Biological effect of radiation is concerned with the evaluation of energy absorbed in the tissue. The study of photon and electron beam characteristics is necessary before calibration machine. The aim of this study was to analysis characteristics of depth dose of different energy beams in water to enhance the quality of the radiotherapy treatment planning. Beam is attenuated by the medium and the transmitted beam with less intensity causes lesser absorbed dose as the depth increases. Relative attenuation on certain points on the beam axis and certain percentage of doses on different depths for 4-15 MV photon beams and 4-18 MeV electron beams have been investigated. Depth dose characteristics of the beams do not show identical attributes as interaction of the beams with matters is mainly governed by beam quality. Attenuation and penetration parameters show variation with dosimetric parameters like field size due to scattering and source to surface distance due to inverse square law but the major parameter in interaction is energy. Detailed analysis of the beam characteristics helps to select appropriate beam for radiotherapy treatment when variety of beam energies available and hence to increase accuracy in radiotherapy treatment.