• Saeed Ahmad Buzdar
  • Muhammad Afzal Rao
  • Aalia Nazir


Background: Photon beam is most widely being used for radiation therapy. Biological effect ofradiation is concerned with the evaluation of energy absorbed in the tissues. It was aimed to analysethe depth dose characteristics of x-ray beams of diverse energies to enhance the quality ofradiotherapy treatment planning. Methods: Depth dose characteristics of different energy photonbeams in water have been analysed. Photon beam is attenuated by the medium and the transmittedbeam with less intensity causes lesser absorbed dose as depth increases. Relative attenuation oncertain points on the beam axis and certain percentage of doses on different depths for availableenergies has been investigated. Results: Photon beam depth dose characteristics do not showidentical attributes as interaction of x-ray with matter is mainly governed by beam quality.Attenuation and penetration parameters of photon show variation with dosimetric parameters likefield size due to scattering and Source to Surface Distance due to inverse square law, but the majorparameter in photon interactions is its energy. Conclusion: Detailed analysis of photon Depth Dosecharacteristics helps to select appropriate beam for radiotherapy treatment when variety of beamenergies available. Evaluation of this type of characteristics will help to establish theoreticalrelationships between dosimetric parameters to confirm measured values of dosimetric quantities,and hence to increase accuracy in radiotherapy treatment.Keywords: Radiotherapy, Treatment Planning, Photon beam, Absorbed Dose


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