Feasibility of Coplanar VMAT for Brain Metastases Using Halcyon With Knowledge-based Planning from Non-coplanar Plan.

Area of Science:

• Radiation Oncology
• Medical Physics
• Neurosurgery

Background:

• Multiple brain metastases present a challenge for radiation therapy.
• Single-isocenter volumetric modulated arc therapy (SI-VMAT) offers potential benefits for treating multiple brain lesions.
• Knowledge-based planning (KBP) systems can optimize treatment plans.

Purpose of the Study:

• To evaluate the feasibility of coplanar SI-VMAT using a Halcyon system with a KBP model.
• To assess the accuracy of a KBP model for Halcyon-based SI-VMAT.
• To compare the dosimetric performance of Halcyon and TrueBeam systems for SI-VMAT.

Main Methods:

• A RapidPlan (RP) KBP model was developed using TrueBeam SI-VMAT plans.
• The RP model was validated for the Halcyon system using root-mean-square error (RSME) and dose-volume histogram (DVH) analysis.
• Dosimetric outcomes were compared between TrueBeam and Halcyon SI-VMAT plans for 10 patients.

Main Results:

• The RP model demonstrated good accuracy for Halcyon plan prediction, with minor deviations in the low-dose region.
• While statistically significant differences were observed in certain dosimetric parameters (gradient index, conformity index, normal brain dose), they were clinically negligible (<1% disparity).
• The Halcyon system achieved clinically acceptable dosimetric performance comparable to the TrueBeam system.

Conclusions:

• The developed RP model can accurately predict doses for Halcyon SI-VMAT, irrespective of beam configurations.
• Coplanar SI-VMAT with the Halcyon system is a feasible and effective treatment option for multiple brain metastases.
• The Halcyon system provides clinically comparable dosimetric results to the TrueBeam system for SI-VMAT.