Analytical linear energy transfer calculations for proton therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Physics

Background:

• Proton therapy's effectiveness relies on accurate relative biological effectiveness (RBE) calculations.
• RBE is dependent on linear energy transfer (LET), necessitating precise LET computation.
• Current methods for LET calculation can be complex, hindering proton therapy optimization.

Purpose of the Study:

• To develop a simplified analytical model for calculating the LET of proton beams in water.
• To enable optimization of proton therapy by providing accurate LET predictions.
• To apply the model to broad proton beams and spread-out Bragg peaks.

Main Methods:

• An analytical model was developed for LET calculation on the central axis of proton beams.
• The model defines LET as a local mean of proton stopping power, weighted by the energy spectrum.
• Coulomb interactions were considered, while nonelastic nuclear interactions were neglected.

Main Results:

• Analytical expressions for track-averaged and dose-averaged LET were derived, incorporating range straggling and initial energy spectrum width.
• The model was validated against GEANT 3.21 Monte Carlo simulations for clinical proton energies (70-250 MeV).
• Excellent agreement was observed between the analytical model and simulations, with deviations under 0.5 keV/µm.

Conclusions:

• The developed analytical model provides a simple yet accurate method for LET calculation in proton therapy.
• The model's accuracy supports its use in optimizing treatment planning for proton therapy.
• The findings validate the model's assumptions and its applicability to clinical scenarios.