Segment-averaged LET concept and analytical calculation from microdosimetric quantities in proton radiation therapy

Area of Science:

• Medical Physics
• Radiation Biology
• Computational Science

Background:

• Proton therapy relies on understanding energy deposition, influenced by Linear Energy Transfer (LET).
• Traditional LET averaging methods may not fully capture proton track variations in biological tissues.
• Microdosimetry theory provides a framework for analyzing energy imparted to biological sites.

Purpose of the Study:

• Introduce segment-averaged LET as a novel approach for averaging proton beam LET distributions.
• Develop an analytical model based on microdosimetry and Monte Carlo simulations for fast and accurate LET calculations.
• Incorporate the effects of varying proton stopping power along microscopic biological structures.

Main Methods:

• Decomposed proton tracks into smaller segments with relatively constant LET.
• Calculated segment distributions and segment-averaged LET using Geant4-DNA microdosimetric simulations.
• Developed analytical functions fitted to simulation data for proton energies from 100 keV to 100 MeV and various site sizes.

Main Results:

• Analytical models showed minimal average differences (≤1.1 keV/μm) compared to Monte Carlo simulations for segment-averaged dose-averaged restricted LET.
• These differences were consistently below the standard deviation of the Monte Carlo calculations.
• The model accurately predicted LET distributions across different proton energies and biological site diameters (1, 5, 10 μm).

Conclusions:

• Segment-averaged LET offers a more refined method for analyzing proton beam characteristics.
• The developed analytical model provides a computationally efficient alternative to exhaustive Monte Carlo simulations for clinical applications.
• This approach enhances the accuracy of predicting radiation effects in proton therapy.