Investigation of photon beam output factors for conformal radiation therapy - Monte Carlo simulations and measurements

F. Haryanto, M. Fippel, Wolfram Laub, O. Dohm, F. Nüsslin

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

The purpose of this study was to investigate beam output factors (OFs) for conformal radiation therapy and to compare the OFs measured with different detectors with those simulated with Monte Carlo methods. Four different detectors (diode, diamond, pinpoint and ionization chamber) were used to measure photon beam OFs in a water phantom at a depth of 10 cm with a source-surface distance (SSD) of 100 cm. Square fields with widths ranging from 1 cm to 15 cm were observed; the OF for the different field sizes was normalized to that measured at a 5 cm × 5 cm field size at a depth of 10 cm. The BEAM/EGS4 program was used to simulate the exact geometry of a 6 MV photon beam generated by the linear accelerator, and the DOSXYZ-code was implemented to calculate the OFs for all field sizes. Two resolutions (0.1 cm and 0.5 cm voxel size) were chosen here. In addition, to model the detector four kinds of material, water, air, graphite or silicon, were placed in the corresponding voxels. Profiles and depth dose distributions resulting from the simulation show good agreement with the measurements. Deviations of less than 2% can be observed. The OF measured with different detectors in water vary by more than 35% for 1 cm × 1 cm fields. This result can also be found for the simulated OF with different voxel sizes and materials. For field sizes of at least 2 cm × 2 cm the deviations between all measurements and simulations are below 3%. This demonstrates that very small fields have a bad effect on dosimetric accuracy and precision. Finally, Monte Carlo methods can be significant in determining the OF for small fields.

Original languageEnglish (US)
JournalPhysics in Medicine and Biology
Volume47
Issue number11
DOIs
StatePublished - Jun 7 2002
Externally publishedYes

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photon beams
Radiotherapy
Photons
Monte Carlo Method
radiation therapy
Detectors
Water
output
Particle Accelerators
Diamond
Monte Carlo methods
Graphite
simulation
Silicon
Ionization chambers
Linear accelerators
chambers
detectors
Air
Monte Carlo method

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physics and Astronomy (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology

Cite this

Investigation of photon beam output factors for conformal radiation therapy - Monte Carlo simulations and measurements. / Haryanto, F.; Fippel, M.; Laub, Wolfram; Dohm, O.; Nüsslin, F.

In: Physics in Medicine and Biology, Vol. 47, No. 11, 07.06.2002.

Research output: Contribution to journalArticle

Haryanto, F. ; Fippel, M. ; Laub, Wolfram ; Dohm, O. ; Nüsslin, F. / Investigation of photon beam output factors for conformal radiation therapy - Monte Carlo simulations and measurements. In: Physics in Medicine and Biology. 2002 ; Vol. 47, No. 11.
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