A Monte Carlo pencil beam scanning model for proton treatment plan simulation using GATE/GEANT4

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Biology

Background:

• Accurate modeling of scanned ion beam delivery is crucial for precise radiation therapy.
• Current methods often require complex nozzle simulations, increasing computational cost.
• Beam Data Library (BDL) measurements are essential for treatment planning systems (TPS).

Purpose of the Study:

• To propose and validate a generic method for modeling scanned ion beam delivery systems.
• To implement new tools within the Gate Monte Carlo platform for treatment plan simulation.
• To reduce reliance on detailed nozzle simulations by using only BDL measurements.

Main Methods:

• Developed a generic modeling method based exclusively on BDL measurements.
• Implemented new simulation tools in the Gate Monte Carlo platform (V6.1).
• Applied the method to an IBA proton pencil beam scanning delivery system, using 27 therapeutic energies for parameter modeling and validation.

Main Results:

• Pristine Bragg peaks accurately reproduced with 0.7 mm range and 0.2 mm spot size accuracy.
• Spread-out Bragg peaks (32 cm range, 10 cm modulation) achieved 0.8 mm range accuracy and <2% dose difference.
• A 2D test pattern passed 2%/2 mm gamma index comparison for 97% of points, demonstrating clinical performance.

Conclusions:

• The proposed generic modeling method is applicable to IBA proton therapy systems.
• The method's key advantage is its reliance solely on BDL measurements.
• The validated beam model shows clinical performance, supporting TPS benchmarking and potential application to other ion therapy systems.