Development of a Monte Carlo multiple source model for inclusion in a dose calculation auditing tool.

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• The Imaging and Radiation Oncology Core Houston (IROC-H) has noted variability in anthropomorphic phantom audit agreements.
• Inaccurate dose calculation algorithms and heterogeneity corrections are potential sources of this disagreement.

Purpose of the Study:

• To develop an independent dose calculation tool for auditing the radiotherapy treatment process.
• To create accurate Monte Carlo multiple source models for Elekta 6 MV and 10 MV therapeutic x-ray beams.

Main Methods:

• Commissioned Monte Carlo models using central axis depth dose and dose profile measurements.
• Validated models against open-field measurements for various field sizes.
• Benchmarked models against measurements in IROC-H's anthropomorphic head and neck and lung phantoms.

Main Results:

• Depth dose data passed a ±2% Van Dyk criterion for 97.9% (6 MV) and 96.8% (10 MV) of measurements.
• Dose profile comparisons showed average agreement of 98.0% (6 MV) and 99.0% (10 MV) using a ±2%/2 mm criterion.
• Phantom plan comparisons achieved passing rates of 87.4% (6 MV) and 89.9% (10 MV) using a ±3%/2 mm gamma criterion.

Conclusions:

• Accurate Monte Carlo multiple source models for Elekta 6 MV and 10 MV x-ray beams have been successfully developed.
• These models are suitable for integration into an independent dose calculation tool.
• The tool will aid in clinical trial audits by improving dose calculation accuracy.