A multi-institution performance assessment of a double-layer MLC.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Varian Halcyon and Ethos linear accelerators (linacs) feature a novel double-layer multi-leaf collimator (MLC).
• Understanding the performance characteristics of this new MLC technology is crucial for quality assurance in radiotherapy.

Purpose of the Study:

• To conduct a multi-institutional evaluation of the MLC performance for Varian Halcyon and Ethos linacs.
• To define the typical range of performance indices for these specific linac models.

Main Methods:

• Utilized plans delivered to a megavoltage (MV) imaging panel for reproducible testing across multiple centers.
• Employed automated image analysis to derive metrics for MLC performance characterization.
• Included tests such as picket fence, MLC leakage, sweeping gap, open field symmetry, output variation with gantry angle, and volumetric modulated arc therapy (VMAT) indices.

Main Results:

• Performance indices were measured across sixteen linacs from eleven institutions.
• Most performance metrics were found to be consistent with those of other linacs.
• An exception was noted regarding the proximal layer positional calibration.

Conclusions:

• Established typical performance index ranges for the multi-leaf collimators in Varian Halcyon and Ethos linacs.
• Provides a benchmark for quality assurance and performance assessment of these radiotherapy devices.