Quantifying effects of lead shielding in electron beams: a Monte Carlo study

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Patient shielding with lead is common in electron beam radiotherapy.
• Current treatment planning systems may not accurately assess lead shielding's impact on dose distribution.
• Accurate dose calculation is crucial for effective radiotherapy outcomes.

Purpose of the Study:

• To quantify the perturbation of dose distributions caused by lead shielding in electron beam radiotherapy.
• To investigate the influence of varying lead thicknesses and field sizes on dose perturbation.
• To demonstrate the utility of Monte Carlo methods for incorporating shielding effects into treatment planning.

Main Methods:

• Monte Carlo dose calculations were performed using a realistic electron linear accelerator model.
• Simulations were conducted in a half-blocked water phantom with lead shielding.
• Electron beam energies (6-20 MeV), lead thicknesses (1-7 mm), and field sizes (10x10 cm², 5x5 cm²) were varied.
• The impact of oblique electron beams on dose perturbation was also analyzed.

Main Results:

• Lead shielding significantly perturbs particle fluence and dose distributions in water.
• The degree of perturbation is dependent on lead thickness, electron beam energy, and field size.
• Oblique electron beams exacerbate the dose perturbation effects.
• Monte Carlo simulations provide a method to accurately assess these shielding-induced changes.

Conclusions:

• Lead shielding introduces significant perturbations in dose distributions during electron beam radiotherapy.
• Accurate quantification of these effects is essential for precise dose delivery.
• Monte Carlo-based treatment planning algorithms can effectively incorporate lead shielding, enhancing treatment accuracy and patient safety.