Radiosurgery treatment planning using conformal arc informed volumetric modulated arc therapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiosurgery Planning

Background:

• Volumetric Modulated Arc Therapy (VMAT) is standard for linac-based radiosurgery of multiple metastases due to its conformality.
• Increasing target numbers in VMAT can lead to suboptimal Multi-Leaf Collimator (MLC) trajectories, causing unnecessary irradiation of healthy tissue.
• A need exists for planning techniques that improve tissue sparing and plan complexity for multiple metastases.

Purpose of the Study:

• To introduce and evaluate Conformal Arc Informed VMAT (CAVMAT), a novel treatment planning technique.
• To assess CAVMAT's ability to reduce healthy tissue dose and improve plan conformity for multiple brain metastases.
• To compare CAVMAT against standard VMAT and other planning strategies.

Main Methods:

• CAVMAT is a hybrid technique combining dynamic conformal arcs with inverse optimization.
• Key steps include target subgrouping for MLC blocking, arc weight optimization, and inverse optimization refinement.
• Twenty multifocal VMAT cases were replanned using CAVMAT, with comparisons based on dose-volume metrics, conformity index, and treatment time.

Main Results:

• CAVMAT significantly reduced irradiated healthy tissue volumes (e.g., V2.5Gy by 25.25%, V6Gy by 13.68%).
• Conformity improved by 3.81% with CAVMAT, while maintaining target dose coverage.
• CAVMAT plans demonstrated reduced complexity and met stringent plan challenge criteria, despite a slight increase in treatment time (2 minutes) and Monitor Units (MU).

Conclusions:

• CAVMAT effectively minimizes dose to healthy tissue and enhances plan conformity for multiple brain metastases.
• The technique addresses limitations of standard VMAT in blocking between numerous targets.
• CAVMAT represents a promising advancement in radiosurgery planning, offering improved tissue sparing and plan quality.