Dosimetric effect of beam angle on the unflattened and flattened photon beams: A monte carlo study

James C.L. Chow, Amir M. Owrangi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

This study compared the variations of depth and surface dose on beam angle between the unflattened and flattened photon beams. Monte Carlo simulation based on the EGSnrc code was used in dose calculation. Phase-space files of the 6 MV photon beams (field size = 10 × 10 cm2) were generated with and without the flattening filter based on a Varian TrueBeam Linac. Depth and surface doses were calculated in a water phantom with angles of the photon beams turning from 0° to 15°, 30°, 45°, 60°, 75° and 90°. Our results showed that compared to the flattened photon beam, the unflattened beam had a higher dose in the build-up region but lower dose beyond the depth of maximum dose. With the Monte Carlo beams cross-calibrated to the machine monitor unit in simulations, dose ratios of the unflattened to flattened beams were in the range of 1.6 – 2.6 with beam angles varying from 0° to 90° in water. In addition, higher surface doses of about 2.5 times were found with beam angles equal to 0o and 15o. However, surface dose deviation between the unflattened and flattened beam became smaller with an increase of beam angle. Using the photon fluence incorporated to the monitor unit, variations of depth and surface dose on the beam angle were investigated and compared. For the unflattened and flattened photon beams, the surface dose and range of depth dose ratios (unflattened to flattened beam) decreased with an increase of beam angle.

Original languageEnglish (US)
Title of host publicationWorld Congress on Medical Physics and Biomedical Engineering, 2015
PublisherSpringer Verlag
Pages637-640
Number of pages4
Volume51
ISBN (Print)9783319193878
DOIs
StatePublished - Jan 1 2015
EventWorld Congress on Medical Physics and Biomedical Engineering, 2015 - Toronto, Canada
Duration: Jun 7 2015Jun 12 2015

Other

OtherWorld Congress on Medical Physics and Biomedical Engineering, 2015
CountryCanada
CityToronto
Period6/7/156/12/15

Keywords

  • Beam obliquity
  • Dose calculation
  • Flattening filter
  • Monte Carlo simulation
  • Skin dose
  • Unflattened photon beam

ASJC Scopus subject areas

  • Bioengineering
  • Biomedical Engineering

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  • Cite this

    Chow, J. C. L., & Owrangi, A. M. (2015). Dosimetric effect of beam angle on the unflattened and flattened photon beams: A monte carlo study. In World Congress on Medical Physics and Biomedical Engineering, 2015 (Vol. 51, pp. 637-640). Springer Verlag. https://doi.org/10.1007/978-3-319-19387-8_155