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Updated: Dec 9, 2025
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Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator
Published on: May 9, 2014
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Step-size effect on calculated photon and electron beam Cherenkov-to-dose conversion factors
Yana Zlateva1, Bryan R Muir2, Issam El Naqa3
1Medical Physics Unit, McGill University, Montreal, QC H4A 3J1, Canada; Department of Radiation Oncology, Duke University, Durham, NC 27710, USA.
Summary
Cherenkov emission (CE)-based radiotherapy dosimetry is step-size independent in Monte Carlo simulations. This physics update ensures accurate dose calculations for improved clinical applications.
Area of Science:
- Medical Physics
- Computational Physics
- Radiotherapy Dosimetry
Background:
- Cherenkov emission (CE)-based radiotherapy dosimetry has been previously validated.
- Condensed history Monte Carlo (MC) methods for CE-to-dose conversion may show step-size dependence.
- Understanding this dependence is crucial for accurate dosimetry.
Purpose of the Study:
- To investigate and present a physics update on step-size dependence in photon and electron beam CE-to-dose conversion using MC.
- To elucidate the underlying physics of Cherenkov emission generation.
- To guide future research in CE-based dosimetry.
Main Methods:
- Calculated CE-to-dose conversion (kCθ±δθ) for photon (6X, 15X) and electron (6E, 20E) beams in water.
- Evaluated relative deviation from single-scattering (SS) simulations across varying fractional electron step energy loss (ESTEPE).
- Implemented and assessed a simplified straight-step method for comparison.
Main Results:
- No significant step-size effect (>0.1%) was observed for dose and kCθ±δθ, except for specific surface dosimetry cases.
- Electron SS deviation uncertainties were generally <0.2%, improving with larger apertures.
- The simplified straight-step method showed greater deviation from SS, particularly superficially.
Conclusions:
- Demonstrated step-size independence of the newly implemented correction in EGSnrc directional Cherenkov calculations.
- This advancement supports clinical CE-based dosimetry.
- Findings are beneficial for the broader Monte Carlo simulation community.
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