Intra-arc binary collimation with dynamic axes trajectory optimization for the SRS treatment of multiple metastases...

Area of Science:

• Radiation Oncology
• Medical Physics
• Neurosurgery

Background:

• Stereotactic radiosurgery/radiotherapy (SRS/SRT) is crucial for treating multiple brain metastases.
• Optimizing treatment plans to minimize dose to organs at risk (OARs) while maintaining target coverage is a significant challenge.

Purpose of the Study:

• To introduce and evaluate a novel treatment planning technique, Combined Optimization of Dynamic Axes with intra-arc binary collimation (CODA-iABC), for multi-metastases cranial SRS/SRT.
• To compare the dosimetric and plan quality metrics of CODA-iABC against conventional Volumetric Modulated Arc Therapy (VMAT).

Main Methods:

• A 3D cost space (CODA cube) was generated based on target-OAR overlap and inter-target blocking.
• Dynamic couch, collimator, and gantry trajectories were optimized using gradient descent and simulated annealing for collimation patterns and monitor units.
• Two CODA-iABC plans (1-arc and 3-arc) were compared against seven existing VMAT plans.

Main Results:

• The 1-arc CODA-iABC plan showed higher doses to the brainstem compared to VMAT.
• The 3-arc CODA-iABC plan demonstrated significant reductions in OAR maximum (48%) and mean (50%) doses and used 24% fewer monitor units (MUs) than VMAT.
• Target conformity was reduced in both CODA-iABC plans compared to VMAT, but the 3-arc technique was more effective in reducing low-dose regions in normal brain tissue.

Conclusions:

• CODA-iABC is a feasible novel technique for automated, patient-specific multi-axis trajectory planning in cranial SRS/SRT.
• The 1-arc CODA-iABC technique is dosimetrically inferior to VMAT.
• The 3-arc CODA-iABC technique offers improved OAR dose sparing and MU efficiency at the expense of target conformity compared to VMAT.