Dose-averaged LET calculation for proton track segments using microdosimetric Monte Carlo simulations.

Area of Science:

• Medical Physics
• Radiation Biology
• Computational Science

Background:

• Proton therapy utilizes proton beams for cancer treatment, with Linear Energy Transfer (LET) being a critical factor in assessing biological effects.
• Accurate calculation of dose-averaged LET is essential for optimizing proton therapy protocols.
• Current microdosimetric Monte Carlo (MC) simulations face computational challenges with uniform sampling and potential inaccuracies with weighted sampling methods.

Purpose of the Study:

• To address limitations in weighted sampling methods for MC simulations of proton therapy.
• To propose and validate corrections for reliable dose-averaged LET calculations.
• To enhance the computational efficiency of microdosimetric simulations for proton therapy.

Main Methods:

• Simulated proton track structures using Geant4-DNA with both uniform and weighted sampling approaches.
• Developed and applied corrections to the weighted sampling method to achieve results comparable to uniform sampling.
• Introduced an additional MC approach to calculate the weighted mean of energy imparted per electronic collision for straggling distribution analysis.

Main Results:

• Found agreement in dose-averaged LET values below (0.15 ± 0.05) keV/μm between corrected weighted and uniform sampling methods.
• Demonstrated that corrected weighted sampling provides reliable dose-averaged LET calculations.
• Analysis was performed for spherical sites (1 and 10 μm) and proton beams (2-90 MeV).

Conclusions:

• A reliable and computationally efficient method for calculating track segment dose-averaged LET in proton therapy using MC simulations was established.
• The proposed corrections ensure accurate straggling distribution characteristics.
• The method is valid when proton stopping power remains constant along the track within the site.