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Development of a Monte Carlo model for the Brainlab microMLC
Jason Belec1, Horacio Patrocinio, Frank Verhaegen
1Medical Physics Department, McGill University Health Centre, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Québec, H3G1A4, Canada.
Physics in Medicine and Biology
|March 31, 2005
Summary
Monte Carlo simulations accurately verify dose distributions for stereotactic radiosurgery using a micro multileaf collimator (microMLC). This method provides reliable treatment plan verification for brain lesions.
Area of Science:
- Medical Physics
- Radiotherapy Physics
- Computational Dosimetry
Background:
- Stereotactic radiosurgery (SRS) utilizes static conformal beams shaped by micro multileaf collimators (microMLC) for treating small, irregular brain lesions.
- Accurate dose calculation is crucial for effective SRS treatment planning and patient safety.
Purpose of the Study:
- To develop and validate a Monte Carlo (MC) simulation tool for verifying dose distributions in SRS brain treatments.
- To assess the accuracy of MC calculations using a dedicated microMLC component module in the BEAMnrc code.
Main Methods:
- Developed a microMLC component module for the BEAMnrc code, modeling a Varian CL2300 linear accelerator 6 MV photon beam.
- Validated the microMLC geometry and leaf leakage profiles against physical measurements (film, solid water phantom).
- Compared MC-calculated dose distributions with diode and film measurements for various field shapes in water phantoms.
Main Results:
- MC calculations showed agreement with measured dose distributions within 2% and/or 1 mm for most field sizes.
- Agreement was within 5% for field sizes smaller than 1.2 cm diameter, attributed to output factor measurement uncertainties.
- The developed MC model demonstrated its capability as a verification tool for SRS treatment plans.
Conclusions:
- The validated Monte Carlo simulation tool provides accurate dose distribution verification for stereotactic radiosurgery using microMLC.
- This computational approach enhances the reliability of treatment planning for small, irregularly shaped brain lesions.
- The study confirms the utility of MC methods in radiotherapy physics for quality assurance.