The Cut-Sort-Group algorithm for efficient delivery of collimated step-and-shoot proton arc therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Proton Therapy

Background:

• Proton arc therapy offers enhanced geometric flexibility for conformal treatments.
• Dynamic Collimation System (DCS) improves target conformity and reduces normal tissue dose.
• Dynamically collimated proton arc therapy (DC-PAT) requires efficient planning for clinical workflow.

Purpose of the Study:

• To develop and demonstrate a post-processing algorithm for improving DC-PAT delivery efficiency.
• To maintain or improve plan quality during DC-PAT efficiency enhancements.

Main Methods:

• Baseline DC-PAT plans were created using a genetic optimizer for three intracranial cases.
• The Cut-Sort-Group (CSG) algorithm was applied in post-processing to modify plans.
• CSG involved low-weight control point removal, novel energy layer sorting, and trimmer reconfiguration.

Main Results:

• CSG algorithm reduced beam delivery time (BDT) by over 64% (10-14 min).
• Plan quality was maintained, with comparable PTV dose coverage and minimal impact on non-target doses.
• PTV D2% remained under 10% of prescription, with a Homogeneity Index (HI) of 0.09-0.12.

Conclusions:

• The CSG algorithm offers a simple post-processing solution to increase DC-PAT efficiency.
• This method is independent of the treatment planning system or optimization algorithm used.
• Reduced BDT (just over 10 min) approaches levels suitable for clinical implementation.