SU-E-T-745: The Use of Electron Dense Materials for Quality Assurance Testing in a Magnetic Field

Journal Article · Mon Jun 15 04:00:00 EDT 2015 · Medical Physics

DOI:https://doi.org/10.1118/1.4925109· OSTI ID:22555113

Zijp, H van; Asselen, B van; Vries, W de; Ishakoglu, K; Beld, E; Kok, J; Wolthaus, J; Lagendijk, J; Raaymakers, B ^[1]

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1. University Medical Center Utrecht, Utrecht (Netherlands)

Purpose: Due to the effect of the magnetic field on the dose deposition (skewing the beam), machine quality assurance (QA) tests for the MR-linac (MRI combined with a linear accelerator) need to be redesigned. In this work we focus on the redesign of QA tests that address geometrical accuracy of the system. Methods: Using electron dense materials (e.g. copper in our experiment) the dose kernel is minimized and thereby the effect of the magnetic field on the dose distribution. This approach is supported by Monte-Carlo simulations and can be used in practice with film measurements. Two examples of QA tests are presented: beam profile and star-shot measurements. Results: The novel method was verified by performing both measurements on a conventional linac and the MR-linac with a film that was sandwiched between copper layers. Measurements were compared with a reference setup which was similar to setup used in clinical practice. On a conventional linac the experimental outcome showed good agreement between the reference and the new setup for both QA tests. The results from the MR-linac showed that the symmetry of the beam profile was restored in presence of the copper layers in the setup and that the isocenter size can be determined accurately with the introduced star-shot setup (see supporting material). Conclusion: The use of electron dense materials for QA tests was shown to be a simple and effective method to remove the effects on the dose distribution enabling assessment of geometrical accuracy of a MR-linac system. The use of high dense materials is not limited to the presented QA tests only, but has a broad applicability for beam specific QA tests in presence of a magnetic field.

• OSTI ID: 22555113
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 6 Vol. 42; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
60 APPLIED LIFE SCIENCES
ACCURACY
BEAM PROFILES
BEAMS
COMPUTERIZED SIMULATION
COPPER
LINEAR ACCELERATORS
MAGNETIC FIELDS
MONTE CARLO METHOD
NMR IMAGING
QUALITY ASSURANCE
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES