Technical Note: Using experimentally determined proton spot scanning timing parameters to accurately model beam...

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Proton therapy utilizes spot scanning for precise dose delivery.
• Accurate modeling of beam delivery time (BDT) is crucial for optimizing treatment efficiency and managing interplay effects.

Purpose of the Study:

• To develop and validate a model for predicting BDT in synchrotron-based proton spot scanning systems.
• To utilize experimentally determined beam parameters for enhanced BDT prediction accuracy.

Main Methods:

• A simulation model was constructed to calculate BDT by summing layer switch, spot switch, and spot delivery times.
• Key beam parameters (layer switch time, magnet preparation/verification time, scanning speeds, spill rate, charge/extraction time) were experimentally quantified.
• The model was validated by comparing predicted BDTs with recorded BDTs from 602 clinical proton beam deliveries.

Main Results:

• Experimentally determined parameters included an average layer switch time of 1.91 s, magnet preparation/verification time of 1.93 ms, scanning speeds of 5.9 m/s (x) and 19.3 m/s (y), and a proton spill rate of 8.7 MU/s.
• Calculated BDTs using experimental parameters showed high accuracy (∆t = -0.49 ± 1.44 s) compared to recorded times.
• Predictions using nominal vendor parameters were significantly less accurate (∆t = -7.48 ± 6.97 s).

Conclusions:

• An accurate BDT prediction model was achieved using experimentally determined proton beam therapy delivery parameters.
• This model can aid in simulating interplay effects, optimizing patient throughput, and identifying machine performance degradation.
• The validated model offers a tool for improving efficiency and quality assurance in proton therapy delivery.