Is a weekly qualitative picket fence test sufficient? A proposed alternate EPID-based weekly MLC QA program

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Multileaf collimator (MLC) quality assurance (QA) is crucial for accurate external-beam radiation therapy.
• Routine QA ensures the reliability and safety of radiation treatment delivery systems.

Purpose of the Study:

• To evaluate the clinical necessity of a comprehensive weekly (C-Weekly) MLC QA program.
• To compare the effectiveness of C-Weekly MLC QA against the American Association of Physics in Medicine-recommended weekly picket fence test (PF-Weekly).

Main Methods:

• A 7-year dataset of weekly MLC QA from 11 linacs across 5 clinical sites was analyzed.
• The C-Weekly program included 5 tests: absolute leaf position, interdigitation, static gantry picket fence, minimum leaf-gap, and VMAT delivery.
• Failure mode and effects analysis (FMEA) was used to calculate risk probability numbers (RPNs) for both QA programs.

Main Results:

• Out of 16,855 tests, 143 failures (0.9%) were recorded.
• VMAT delivery (55.9%) and absolute MLC leaf position (27.3%) were the most common failure modes.
• RPN scores for PF-Weekly QA ranged from 60 to 192, while C-Weekly QA scores ranged from 48 to 96.

Conclusions:

• Comprehensive weekly MLC QA is imperative for reducing RPNs to below 125.
• The PF-Weekly program resulted in higher RPNs (>125), indicating a greater risk.
• The findings support the clinical necessity of implementing a comprehensive weekly MLC QA program for enhanced treatment accuracy and safety.