High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Quality Assurance

Background:

• High-precision radiosurgery requires robust delivery quality assurance (DQA).
• Current DQA methods may have limitations in detecting subtle delivery errors.
• Robotic radiosurgery systems necessitate advanced DQA techniques.

Purpose of the Study:

• To investigate and validate the use of a liquid-filled ion chamber array for robotic radiosurgery DQA.
• To assess the array's performance across various test scenarios and clinical patient plans.
• To establish the suitability of this technology for ensuring treatment accuracy.

Main Methods:

• Preliminary evaluation included beam profile validation and response analysis to source-detector distance and incidence angle.
• DQA analysis involved array-to-plan registration, Gamma Index evaluation (2%/2mm), dose profile alignment, and final assessment with a 1mm distance-to-agreement criterion.
• Tested with phantom misalignments, dose miscalibrations, undelivered Monitor Units, and 55 clinical plans.

Main Results:

• The liquid-filled ion chamber array demonstrated agreement with a microDiamond detector for profile measurements.
• Response variations were within 1% for clinically relevant source-detector distances and beam incidence angles up to 80°.
• The 1mm distance-to-agreement criterion successfully detected small errors missed by the 2mm criterion; all clinical plans met tight tolerances.

Conclusions:

• A high-resolution liquid-filled ion chamber array is suitable for robotic radiosurgery DQA.
• Tight distance-to-agreement criteria (1mm) are effective in detecting small delivery errors.
• Future enhancements may involve beam-specific corrections for incidence angle and source-detector distance response.