A method of simulating dynamic multileaf collimators using Monte Carlo techniques for intensity-modulated radiation...

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Biology

Background:

• Intensity-modulated radiation therapy (IMRT) relies on precise radiation delivery.
• Accurate modeling of dynamic multileaf collimators (MLCs) is crucial for IMRT quality assurance.
• Existing simulation methods may lack efficiency or fidelity for dynamic MLC (DMLC) motion.

Purpose of the Study:

• To develop and implement an efficient Monte Carlo simulation method for dynamic MLC motion.
• To accurately model DMLC trajectories during IMRT beam delivery.
• To validate the simulation method against experimental measurements.

Main Methods:

• Developed a Monte Carlo simulation approach randomizing leaf positions proportionally to monitor units (MUs).
• Integrated the method into the EGS4 Monte Carlo code for simulating Varian DMLCs.
• Utilized a cumulative probability distribution function (CPDF) derived from MU index for leaf position sampling.
• Simulated both step-shoot and sweeping-leaf DMLC motions.

Main Results:

• The DMLC simulation method was successfully implemented and evaluated.
• Dose intensity maps for IMRT fields were computed with verified accuracy via film measurements.
• The simulation approach demonstrated improved operational efficiency by avoiding individual segment simulations.
• The leaf-position sampling technique allowed for more faithful simulation of dynamic leaf motion.

Conclusions:

• The developed Monte Carlo method provides an efficient and accurate approach for simulating DMLC motion in IMRT.
• This technique enhances the fidelity of radiation therapy simulations, improving treatment planning and verification.
• The method offers a valuable tool for quality assurance and research in advanced radiation therapy techniques.