A comprehensive procedure for characterizing arbitrary azimuthally symmetric photon beams

Ahad Ollah Ezzati, Mostafa Sohrabpour, Seied Rabi Mahdavi, Ivan Buzurovic, Matthew T. Studenski

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Purpose: A new Monte Carlo (MC) source model (SM) has been developed for azimuthally symmetric photon beams. Methods: The MC simulation tallied phase space file (PSF) is divided into two categories depending on the relationship of the particle track line to the beam central axis: multiple point source (MPS) and spatial mesh based surface source (SMBSS). To validate this SM, MCNPX2.6 was used to generate two PSFs for a 6MV photon beam from a Varian 2100C/D linear accelerator. Results: PDDs and profiles were calculated using the SM and original PSF for different field sizes from 5×5 to 40×40cm2. Agreement was within 2% of the maximum dose at 100cm SSD and 2.5% of the maximum dose at 200cm SSD for beam profiles at depths of 3.5cm and 15cm with respect to the original PSF. Differences between the source model and the PSF in the out-of-field regions were less than 0.5% of the profile maximum value at 100cm SSD. Differences between measured and calculated points were less than 2% of the maximum dose or 2mm distance to agreement (DTA) at 100cm SSD. Conclusions: This SM is unique in that it accounts for a higher level of energy dependence on the particle's direction and it is independent from accelerator components, unlike other published SMs. The model can be applied to any arbitrary azimuthally symmetric beam and has source biasing capabilities that significantly increase the simulation speed up to 3300 for certain field sizes.

Original languageEnglish (US)
Pages (from-to)191-201
Number of pages11
JournalPhysica Medica
Issue number2
StatePublished - Mar 2014
Externally publishedYes


  • Monte Carlo
  • Phase space file
  • Radiotherapy
  • Source model

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy(all)


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