Mechanical Characterization and Validation of the Dynamic Collimation System Prototype for Proton Radiotherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Pencil beam scanning (PBS) proton therapy offers precise tumor targeting.
• Beam cross-sectional size limits PBS accuracy, potentially causing dose spread to healthy tissue.
• Collimators can shape the proton beam, but a dynamic system is needed for real-time adaptation.

Purpose of the Study:

• Establish dosimetric and mechanical acceptance criteria for a dynamic collimation system (DCS).
• Characterize the mechanical accuracy of a DCS prototype.
• Validate the DCS performance against established criteria for improved proton therapy.

Main Methods:

• Monte Carlo simulations to determine required trimmer positioning accuracy.
• Mechanical characterization of trimmer positioners and rotational accuracy using a FARO ScanArm.
• Evaluation of time penalties associated with DCS implementation in proton therapy.

Main Results:

• DCS requires trimmers positioned within ±0.5 mm and ±1.0° for acceptable dose distributions (gamma analysis).
• Prototype trimmer positioners demonstrated accuracy within 50 μm at high jerk values (up to 400 m/s³).
• Rotational trimmer accuracy was validated to ±0.5°, with treatment time increasing by 25-52 seconds per field.

Conclusions:

• The dynamic collimation system (DCS) meets rigorous mechanical and dosimetric standards for pencil beam scanning (PBS) proton therapy.
• The DCS prototype exhibits high accuracy, crucial for minimizing off-target radiation dose.
• While adding treatment time, the DCS offers a viable solution for enhancing PBS precision in cancer treatment.