Convex hull-based microdosimetry in Geant4-DNA: linking electron track structures to radiobiological effectiveness

Area of Science:

• Medical Physics
• Computational Biology
• Radiation Dosimetry

Background:

• Accurate geometrical modeling is crucial for nanometric scale microdosimetry.
• Understanding electron track structures is key to predicting radiobiological effectiveness.
• Existing methods require enhancement for efficient simulation of nanoscale radiation interactions.

Purpose of the Study:

• To incorporate a novel Convex Hull (CH) microdosimetric technique into Geant4-DNA.
• To establish a direct link between electron track structures and radiobiological outcomes.
• To improve computational efficiency in modeling micro- and nanodosimetric quantities.

Main Methods:

• Simulated track structures in liquid water using monoenergetic electrons (0.1 keV–1000 keV) and clinical electron beams (6 MeV–18 MeV).
• Implemented the Jarvis-March gift wrapping algorithm (CH technique) within Geant4-DNA for geometric encapsulation.
• Calculated dose mean lineal energy and frequency mean lineal energy, utilizing the Microdosimetric Kinetic Model for radiobiological parameter estimation.

Main Results:

• The CH technique achieved <5% accuracy for micrometer scales, with larger differences at the nanometer scale due to track volume definitions.
• The alpha parameter increased with incident particle energy, influencing the relative biological effectiveness (RBE).
• RBE for clinical electron beams was energy-independent, approximately 0.85 when normalized to X-ray results.

Conclusions:

• The CH-based approach offers an efficient computational method for micro- and nanodosimetric calculations.
• This technique enables model-based RBE calculation and radiation quality assessment at the nanometric scale.
• The study highlights the impact of ionization clustering on radiobiological effectiveness.