Characterization of the on-board megavoltage imager in a magnetic resonance-guided radiotherapy machine for beam output checks

Abstract

We characterized the on-board megavoltage imager (MVI) of a magnetic resonance-guided radiotherapy machine for beam output checks. Linearity and repeatability of its dose response were investigated. Alignment relative to the beam under clinical circumstances was evaluated for a year using daily measurements. Linearity and short-term repeatability were excellent. Long-term repeatability drifted 0.8 % per year, which can be overcome by monthly cross calibrations. Long-term alignment was stable. Thus, the MVI has suitable characteristics for beam output checks.

Keywords

• Radiotherapy
• Quality assurance
• MRI-Linac
• Unity
• Dosimetry
• MV imager