An MCNP-based model of a linear accelerator x-ray beam.

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Physics

Background:

• Accurate simulation of radiation beams is crucial for radiotherapy quality assurance.
• Linear accelerators (LINACs) require precise modeling of beam-generating components.
• The Monte Carlo N-Particle (MCNP) code is a powerful tool for radiation transport simulations.

Purpose of the Study:

• To develop a simplified MCNP model of a LINAC radiation head.
• To calculate X-ray beam energy spectra and angular distributions.
• To assess the feasibility of using this model for LINAC quality control and treatment planning.

Main Methods:

• Utilized MCNP code on a personal computer to model LINAC head components.
• Simulated electron target, collimators, flattening filter, and wedge filter.
• Calculated depth dose distributions and dose profiles at 4 MV.

Main Results:

• Successfully modeled the X-ray beam's energy spectra and angular distributions.
• Calculated depth dose and dose profiles were within acceptable clinical limits.
• The model demonstrated accuracy for a Philips SL 75/5 LINAC at 4 MV.

Conclusions:

• The MCNP modeling technique is effective for simulating LINAC X-ray beams.
• This method can be adapted for various LINACs by inputting component specifications.
• The developed model can serve as a valuable quality control tool for LINACs and treatment planning.