Range shift and dose perturbation with high-density materials in proton beam therapy

D. Nichiporov, V. Moskvin, L. Fanelli, I. J. Das

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Radiotherapy with proton beams requires accurate knowledge of the proton range. When materials with high atomic numbers (Z) and densities (e.g. prostheses or implants) are present in the patient, they give rise to pronounced uncertainties in computed tomography data and to large errors in proton range and dose calculations. A modified analytical expression is proposed for the observed range shift in water in the presence of a high-density material of known thickness and density. The expression was verified experimentally in a clinical beam with various thicknesses and materials in a water phantom, at several beam ranges and at different depths. Measurements were also made behind the medium-to-water interface to evaluate dose perturbation using a thin window parallel plate ion chamber. Primary particle fluence variations due to the range shift were studied in a separate experiment. The measured range shift was in good agreement (±0.3 mm) with the analytical expression for most of the materials studied. A small, but consistent dependence of range shift on the energy of impinging protons was found. Dose perturbation factor in water downstream of the material is less than +5% for thicknesses up to 8 g/cm 2. The proposed analytical expression can be used in clinical situations to determine the range shift in patient caused by an implanted material. Dose perturbation in the presence of an implant is due to the changes in primary particle fluence resulting from several physical processes.

Original languageEnglish (US)
Pages (from-to)2685-2692
Number of pages8
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume269
Issue number22
DOIs
StatePublished - Nov 15 2011

Keywords

  • Dose perturbation
  • Proton beam
  • Range shift

ASJC Scopus subject areas

  • Instrumentation
  • Nuclear and High Energy Physics

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