Characterization of a prototype MR-compatible Delta4 QA system in a 1.5 tesla MR-linac

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Quality assurance (QA) for Magnetic Resonance Linear Accelerators (MR-Linacs) requires specialized MR-compatible devices.
• The development of MR-compatible QA tools is crucial for ensuring treatment accuracy in advanced radiotherapy.

Purpose of the Study:

• To evaluate the performance and safety of a newly developed MR-compatible QA device, the MR-Delta4.
• To compare the characteristics of the MR-Delta4 with the established clinical Delta4-PT device.

Main Methods:

• Investigated detector response characteristics including reproducibility, linearity, field size, dose rate, dose-per-pulse, and angular dependency.
• Tested both the clinical Delta4-PT and the MR-Delta4 on a conventional linac.
• Further tested the MR-Delta4 on an Elekta MR-linac.

Main Results:

• No statistically significant differences were observed in short-term reproducibility, dose linearity, field size dependency, dose rate dependency, or angular dependency between the MR-Delta4 and Delta4-PT.
• A minor, clinically insignificant difference was noted in dose-per-pulse dependency.
• The MR-Delta4 demonstrated performance comparable to the non-MR-compatible Delta4-PT.

Conclusions:

• The MR-Delta4 phantom exhibits comparable characteristics to the clinically used Delta4-PT.
• The MR-compatible Delta4 prototype is safe and effective for QA in the 1.5 tesla magnetic field of an Elekta MR-linac.