Evaluation of a Dynamic Collimation System to Improve IMPT Dose Distributions and Maintain Treatment Efficiency

Area of Science:

• Medical Physics
• Radiation Oncology
• Proton Therapy

Background:

• Previous dynamic collimator system (DCS) developments covered hardware, dose calculation, quality assurance, and treatment planning optimization.
• Clinical implementation requires efficient delivery and integrated tools, necessitating time-minimization algorithms.

Purpose of the Study:

• To develop and evaluate a novel algorithm for minimizing treatment time in DCS-based proton therapy.
• To assess the dosimetric accuracy and delivery efficiency of DCS-IMPT compared to conventional methods.

Main Methods:

• Ten brain patient treatment plans were replanned using DCS with a modified treatment planning system on an IBA Proteus Plus system.
• An optimization algorithm minimized delivery time by sequencing spot positions and collimator settings.
• Plan quality and delivery accuracy were evaluated using DVH metrics, patient-specific QA, and log file analysis.

Main Results:

• DCS reduced dose gradient index by 26.4% and mean dose to adjacent healthy tissue by 19.3%.
• Mean dose reductions for optic nerves and brainstem were 50% and 63.9%, respectively.
• DCS treatments added only ~49 seconds per field with high accuracy (PSQA pass rates >99.7%).

Conclusions:

• DCS-collimated intensity modulated proton therapy (IMPT) offers significant dosimetric advantages over uncollimated treatments.
• Highly collimated DCS treatments are clinically deliverable with sufficient accuracy and minimal time penalty.