Effect of CT Image-Based Voxel Size On Monte Carlo Dose Calculation.

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Conventional dose calculation algorithms in radiation therapy planning systems have limitations in accuracy.
• These algorithms often fail to account for lateral radiation transport and electronic disequilibrium at tissue interfaces.
• Monte Carlo methods offer high precision but are hindered by long computation times for clinical use.

Purpose of the Study:

• To evaluate the impact of different voxel sizes on the accuracy of dose distributions and computational time using the EGSnrc Monte Carlo code.
• To determine optimal voxel size for accurate and efficient Monte Carlo-based dose calculations in radiation therapy.

Main Methods:

• The EGSnrc Monte Carlo code system was employed for dose calculations.
• Simulations were performed using a head and neck patient CT dataset.
• The effect of varying voxel sizes on dose distribution accuracy and CPU time was investigated.

Main Results:

• Smaller voxel sizes, specifically less than 4mm, were found to enhance the accuracy of dose distributions.
• Utilizing smaller voxels also led to improved image resolution.
• A reduction in computation time was observed with the use of optimized voxel sizes.

Conclusions:

• Voxel sizes smaller than 4mm are recommended for Monte Carlo dose calculations to achieve superior accuracy.
• This approach balances high-fidelity dose distribution with acceptable computational efficiency for clinical applications.
• Optimizing voxel size is key to leveraging the benefits of Monte Carlo simulations in radiation treatment planning.