E-Brachy: New dosimetry package for electronic brachytherapy sources

Area of Science:

• Medical Physics
• Radiotherapy
• Computational Dosimetry

Background:

• Variability in Xoft electronic high dose rate brachytherapy sources leads to discrepancies in output due to manual manufacturing.
• This inter-source variability impacts the accuracy of radiation delivery in brachytherapy treatments.

Purpose of the Study:

• To develop a dosimetry software tool, E-Brachy, for characterizing Xoft sources.
• To quantify discrepancies in photon spectrum and dosimetric properties of Xoft brachytherapy sources.

Main Methods:

• Utilized Geant4 Monte Carlo toolkit and GUIMesh Python tool to model Xoft source geometry and materials.
• Simulated X-ray generation from electrons and employed variance reduction techniques for efficiency.
• Validated simulated photon energy spectra against National Institute of Standards and Technology (NIST) measurements.

Main Results:

• Selected material composition yielded a simulated spectrum highly correlated (Pearson's r=0.99) with NIST measurements.
• Identified tungsten, yttrium, and silver in source components through spectral analysis.
• Observed dose rate differences exceeding 20% between S7500 and S700 models at specific angles and distances.

Conclusions:

• Successfully developed E-Brachy software for characterizing Xoft electronic brachytherapy sources.
• E-Brachy can identify inter- and intra-source variability when combined with spectral measurements.
• Significant deviations in TG-43 parameters between S700 and S7500 models exceed established recommendations.