Depth scaling of solid phantom for intensity modulated radiotherapy beams

Yukio Fujita, Naoki Tohyama, Atsushi Myojoyama, Hidetoshi Saitoh

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


To reduce the uncertainty of absorbed dose for high energy photon beams, water has been chosen as a reference material by the dosimetry protocols. However, solid phantoms are used as media for absolute dose verification of intensity modulated radiotherapy (IMRT). For the absorbed dose measurement, the fluence scaling factor is used for converting an ionization chamber reading in a solid phantom to absorbed dose to water. Furthermore the depth scaling factor is indispensable in determining the fluence scaling factor. For IMRT beams, a photon energy spectrum is varied by transmitting through a multileaf collimator and attenuating in media. However, the effects of spectral variations on depth scaling have not been clarified yet. In this study, variations of photon energy spectra were determined using the EGS Monte Carlo simulation. The depth scaling factors for commercially available solid phantoms were determined from effective mass attenuation coefficients using photon energy spectra. The results clarified the effect of spectral variation on the depth scaling and produced an accurate scaling method for IMRT beams.

Original languageEnglish
Pages (from-to)707-713
Number of pages7
JournalJournal of radiation research
Issue number6
Publication statusPublished - 2010 Nov
Externally publishedYes


  • Beam hardening effect
  • Depth scaling
  • Intensity modulated radiotherapy
  • Multileaf collimator
  • Solid phantom

ASJC Scopus subject areas

  • Radiation
  • Radiology Nuclear Medicine and imaging
  • Health, Toxicology and Mutagenesis


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