Design tools for proton therapy nozzles based on the double-scattering foil technique

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Modeling

Background:

• Proton therapy is a growing cancer treatment modality with increasing global facility development.
• Accurate modeling of proton therapy beamlines is crucial for precise dose delivery and patient safety.
• Understanding secondary neutron production is essential for minimizing risks associated with proton therapy.

Purpose of the Study:

• To develop and validate a computational model for a passively scattered proton therapy beamline.
• To assess the accuracy of the model in predicting three-dimensional dose distributions.
• To calculate and evaluate neutron dose equivalents at clinically relevant anatomical sites.

Main Methods:

• Combined analytical and Monte Carlo simulation tools to model the Harvard Cyclotron Laboratory's neurosurgery treatment beamline.
• Validated predicted dose distributions against experimental measurements for central-axis depth-dose curves and absorbed dose cross-field profiles.
• Calculated neutron dose equivalent per therapeutic absorbed dose (H/D) at various anatomical locations.

Main Results:

• Predicted dose distributions showed excellent agreement with measurements (within 0.1 mm for depth-dose and 2.1 mm for cross-field profiles).
• Calculated neutron dose equivalent ratios (predicted-to-measured) were 1.8 in the gonadal region and 3.4 in the thyroid region.
• A global predicted-to-measured H/D ratio of 2.6 was determined.

Conclusions:

• The combined analytical and Monte Carlo modeling approach accurately predicts dose distributions for passive proton therapy beamlines.
• The study quantifies neutron dose equivalents, highlighting potential risks in specific anatomical regions.
• These findings support the use of computational modeling for optimizing proton therapy treatments and ensuring patient safety.