Dosimetry for the MRI accelerator: the impact of a magnetic field on the response of a Farmer NE2571 ionization chamber

I Meijsing, B.W. Raaymakers, A.J.E. Raaijmakers, J W. Kok, L Hogeweg, B. Liu, J.J.W. Lagendijk

Research output: Contribution to journalArticleAcademicpeer-review

88 Citations (Scopus)

Abstract

The UMC Utrecht is constructing a 1.5 T MRI scanner integrated with a linear accelerator (Lagendijk et al 2008 Radiother. Oncol. 86 25-9). The goal of this device is to facilitate soft-tissue contrast based image-guided radiotherapy, in order to escalate the dose to the tumour while sparing surrounding normal tissues. Dosimetry for the MRI accelerator has to be performed in the presence of a magnetic field. This paper investigates the feasibility of using a Farmer NE2571 ionization chamber for absolute dosimetry. The impact of the mcagnetic field on the response of this ionization chamber has been measured and simulated using GEANT4 Monte Carlo simulations. Two orientations of the ionization chamber with respect to the incident beam and the magnetic field which are feasible in the MRI accelerator configuration are taken into account. Measurements are performed using a laboratory magnet ranging from 0 to 1.2 T. In the simulations a range from 0 to 2 T is used. For both orientations, the measurements and simulations agreed within the uncertainty of the measurements and simulations. In conclusion, the response of the ionization chamber as a function of the magnetic field is understood and can be simulated using GEANT4 Monte Carlo simulations.

Original languageEnglish
Pages (from-to)2993-3002
Number of pages10
JournalPhysics in Medicine and Biology
Volume54
Issue number10
DOIs
Publication statusPublished - 21 May 2009
Externally publishedYes

Keywords

  • Artifacts
  • Computer-Aided Design
  • Equipment Design
  • Equipment Failure Analysis
  • Magnetic Resonance Imaging
  • Particle Accelerators
  • Radiometry
  • Radiotherapy Dosage
  • Radiotherapy, Conformal
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Evaluation Studies
  • Journal Article

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