Comparing stochastic proton interactions simulated using TOPAS-nBio to experimental data from fluorescent nuclear...

Area of Science:

• Medical Physics
• Radiation Biology
• Computational Science

Background:

• Monte Carlo (MC) simulations are crucial for modeling proton energy deposition in radiotherapy.
• Microscopic validation of MC simulations and experimental metrology for individual proton tracks are currently lacking.
• Fluorescent nuclear track detectors (FNTDs) offer potential for studying individual proton tracks.

Purpose of the Study:

• To compare microscopic proton interaction simulations with experimental data from FNTDs.
• To validate the TOPAS-nBio MC platform at the sub-cellular level.
• To explore the potential of FNTDs for experimental microdosimetry of proton tracks.

Main Methods:

• Proton irradiation of Al2O3:C,Mg FNTDs within a water phantom at various depths along a Bragg peak.
• MC simulations using TOPAS and TOPAS-nBio with Geant4-DNA physics to model proton interactions.
• Analysis of FNTD track integrated brightness (IB) and comparison with simulated linear energy transfer (LET) and lineal energy (y).

Main Results:

• A strong correlation was observed between measured FNTD track IB and simulated voxelized track-averaged LET and microdosimetric lineal energy (y).
• Histograms of FNTD track IB closely matched TOPAS-nBio simulations of terminal electrons per proton.
• Experimental trends in FNTD track IB replicated those seen in MC simulations across different exposure depths.

Conclusions:

• This study provides the first experimental validation of MC simulations at the sub-cellular scale using FNTDs.
• FNTDs show promise for enabling experimental studies of individual proton track microdosimetric properties.
• The results support the use of TOPAS-nBio for accurate simulation of proton interactions relevant to radiobiology.