Adapting VMAT plans optimized for an HD120 MLC for delivery with a Millennium MLC

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Linac downtime disrupts patient treatment schedules, necessitating plan transfers between machines.
• Transferring Volumetric Modulated Arc Therapy (VMAT) plans from standard-definition to high-definition multi-leaf collimators (MLCs) is routine.
• Adapting VMAT plans from high-definition MLCs to standard-definition MLCs poses a significant challenge due to differing aperture capabilities.

Purpose of the Study:

• To develop and validate an efficient method for adapting VMAT plans designed for high-definition MLCs for delivery on standard-definition MLCs.
• To assess the dosimetric accuracy and feasibility of using adapted VMAT plans for various cancer sites.

Main Methods:

• Developed a novel computational method to modify VMAT plan aperture shapes from high-definition to standard-definition MLC geometry.
• Applied the adaptation method to VMAT plans for head-and-neck, brain, lung, and prostate cancer treatments.
• Verified the dosimetric accuracy of the adapted plans through phantom measurements and delivery checks.

Main Results:

• The developed method successfully adapted VMAT plans for delivery on standard-definition MLCs.
• Dosimetric analysis confirmed the clinical viability of the adapted plans across diverse treatment sites.
• Phantom measurements validated the accurate delivery of adapted VMAT plans.

Conclusions:

• The efficient adaptation method overcomes the challenge of transferring VMAT plans between different MLC definitions.
• This approach facilitates seamless treatment delivery continuity, even with linac downtime or differing equipment.
• The validated method supports clinical workflows requiring VMAT plan adaptation for standard-definition MLCs.