A practical approach to prevent gantry-couch collision for linac-based radiosurgery

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Gantry-couch collisions pose a significant risk in linear accelerator (linac)-based stereotactic radiosurgery (SRS) treatment planning.
• Current collision detection methods in commercial software are often limited, necessitating backup plans and discarding potentially useful beam angles.
• Developing a robust and user-friendly collision detection system is crucial for safe and efficient SRS delivery.

Purpose of the Study:

• To develop a simple, accurate, and computationally inexpensive analytical method for detecting gantry-couch collisions in SRS.
• To implement and validate this method on a specific linac and micro-multileaf collimator (MLC) system.
• To demonstrate the method's utility in preserving treatment planning options and avoiding the need for backup plans.

Main Methods:

• Developed an analytical method mathematically solving collision detection by determining facet intersection in 3D space.
• Implemented a computer code using quick, machine-specific measurements of gantry and couch geometry relative to the linac isocenter.
• Tested the method on a Varian Clinac 600C with a BrainLab micro-MLC, verifying predictions on the machine.

Main Results:

• The analytical method accurately confirmed clearance for 54 retrospective SRS plans (76 isocenters).
• The system correctly predicted collisions in all ten artificially created collision cases.
• The method proved accurate, easy to implement, and computationally inexpensive.

Conclusions:

• An effective analytical method for SRS gantry-couch collision detection has been developed.
• This method is accurate, user-friendly, and computationally efficient, enhancing treatment planning safety.
• The approach minimizes the need for backup plans and optimizes beam angle selection in SRS.