Evaluation of the TrueBeam machine-performance-check (MPC): Collimator device check (CDC)

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Routine quality assurance (QA) is essential for maintaining the performance of medical linear accelerators (linacs).
• Accurate assessment of multileaf collimator (MLC) and jaw positioning is critical for precise radiation delivery.
• The Varian Machine Performance Check (MPC) Collimator Devices Check (CDC) is a tool designed to streamline linac QA procedures.

Purpose of the Study:

• To evaluate the Varian MPC CDC for routine testing of MLC and jaw positioning.
• To assess the performance of the CDC within an American Association of Physicists in Medicine (AAPM) compliant linac QA program.

Main Methods:

• The study assessed MLC positioning, MLC backlash, jaw positioning, and jaw parallelism using the CDC.
• Repeatability, concordance with conventional QA methods, and sensitivity were evaluated.
• Measurements were conducted on four linacs over five months, comparing CDC results to established tests like the picket fence and EPID-based methods.

Main Results:

• The CDC demonstrated high repeatability for MLC positioning (0.02 mm) and jaw parallelism (0.009°).
• Concordance with conventional methods was observed within acceptable limits for MLC and jaw parameters.
• The CDC showed good sensitivity in detecting introduced errors, with correlation coefficients for MLC backlash up to 0.9.

Conclusions:

• The Varian MPC CDC provides an acceptably equivalent assessment of MLC and jaw positioning compared to standard methods.
• The CDC can be effectively integrated into a linac QA program for routine testing.
• This tool contributes to efficient and reliable linac QA, ensuring patient safety and treatment accuracy.