Backscatter dose perturbation in kilovoltage photon beams at high atomic number interfaces

I. J. Das, K. L. Chopra

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

Dose perturbations at tissue interfaces have been of significant concern since the beginning of this century. However, comprehensive studies related to the backscatter perturbation in kilovoltage beams are still limited. The dose perturbation depends on various parameters, including beam energy, field size, and the thickness, width, position, and atomic number, Z, of the inhomogeneity creating the interface with soft tissue. Using a thin window parallel plate ion chamber having relatively flat response at low energies, the dose perturbation was measured as backscatter dose perturbation factor, BSDF, at various interfaces in kilovoltage x-ray beams. The BSDF is defined as the ratio of doses with and without an interface for identical setup conditions. Results indicate that the BSDF is strongly dependent on beam energy, like the backscatter factor. Contrary to its behavior in megavoltage beams, BSDF in kilovoltage beams does depend on the field size, suggesting a contribution from scattered photons and fluorescent radiation, originating in the high-Z material. The thickness of the high-Z medium is not critical, since a fraction of a millimeter is sufficient to provide full backscatter. The interface effect with wide inhomogeneity has two distinct regions: the high dose region (BSDF>1.0), which is very localized and disappears within a fraction of a millimeter, and the low dose region (BSDF

Original languageEnglish (US)
Pages (from-to)767-773
Number of pages7
JournalMedical Physics
Volume22
Issue number6
DOIs
StatePublished - 1995
Externally publishedYes

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Photons
X-Rays
Ions
Radiation

Keywords

  • backscatter dose perturbation
  • high- Z interface
  • interface effect
  • kilovoltage x rays

ASJC Scopus subject areas

  • Biophysics

Cite this

Backscatter dose perturbation in kilovoltage photon beams at high atomic number interfaces. / Das, I. J.; Chopra, K. L.

In: Medical Physics, Vol. 22, No. 6, 1995, p. 767-773.

Research output: Contribution to journalArticle

Das, I. J. ; Chopra, K. L. / Backscatter dose perturbation in kilovoltage photon beams at high atomic number interfaces. In: Medical Physics. 1995 ; Vol. 22, No. 6. pp. 767-773.
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