• Saeed Ahmad Buzdar
  • M. Afzal
  • Andrew Todd- Pokropek


Background: In radiotherapy treatment, the calculation of radiation dose distribution in target volumelead to an optimum set of planning parameters. This worked has been aimed to compare two photonbeam dose calculation algorithms in the Oncentra Treatment Planning system for Varian LinearAccelerator, to assure the quality of treatment planning. Methods: Monitor Units to be delivered onnormalization depth in patient has been calculated using the pencil beam and collapsed cone algorithmsfor two photon energies 6 and 10 MV. The percentage depth dose and beam profiles for 21 treatmentfields, for both the calculation systems have been compared for both photon energies. Results: Thepercentage depth doses and beam profiles for both calculation systems are comparable in large fieldsizes as well as central axis field settings. The doses at normalization depth deviate for some fieldsettings, but in central axis large field sizes the difference in within tolerance limits. Conclusion: Bothcalculation algorithms are in close agreement in most of the field settings (mainly in central axis fields),within tolerance level. The difference is relatively greater in small field sizes and off-axis field settings.Keywords: Radiotherapy, treatment planning, dose distribution, pencil beam, collapsed cone


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