Backscatter Dose Perturbation at High Atomic Number Interfaces in Megavoltage Photon Beams

Indra J. Das, Faiz M. Kahn

Research output: Contribution to journalArticlepeer-review

91 Scopus citations

Abstract

Most computer algorithms used clinically for photon beam treatment planning are unable to predict the effect of electron backscattering on dose distribution from high atomic number materials. It has been observed that there is a significant dose enhancement at such an interface. We define the dose enhancement in terms of backscatter dose factor (BSDF), which depends on the energy of the photon beam, thickness and width of the inhomogeneity, distance from the interface, and the atomic number of the inhomogeneity. For all energies studied, the dose fall-off is initially very rapid and disappears beyond a few millimeters upstream from the interface. Empirically derived equations are presented for dose calculation at the interfaces of various media, including bone and soft tissue, for photon energies in the range of Co-60 gamma rays to 24 MV x rays.

Original languageEnglish (US)
Pages (from-to)367-375
Number of pages9
JournalMedical physics
Volume16
Issue number3
DOIs
StatePublished - May 1989

Keywords

  • Backscatter
  • dose perturbation
  • high Z interface
  • treatment planning

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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