Room scatter effects in Total Skin Electron Irradiation: Monte Carlo simulation study

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Total Skin Electron Irradiation (TSEI) is a radiotherapy technique using large electron fields.
• Scattered electrons from the treatment room floor are a potential source of dose, but their contribution is not well-understood.
• Monte Carlo (MC) simulations are a powerful tool for studying radiation transport phenomena.

Purpose of the Study:

• To investigate the contribution of floor-scattered electrons to skin dose in TSEI treatments.
• To analyze the influence of beam energy, dual-field angle, and floor material on floor scatter.
• To characterize the energy spectrum of scattered electrons.

Main Methods:

• Monte Carlo (MC) simulations using the EGSnrc code.
• Investigated parameters included beam energy, dual-field angle, and floor material.
• Verified MC calculations with dose profile measurements.

Main Results:

• Floor scatter contribution varied significantly with floor material (e.g., 21% for iron, 12% for water at 20 cm).
• No dependence of floor scatter on beam energy or dual-field angle was observed.
• The scattered electron spectrum was relatively uniform from a few hundred keV to 4 MeV.

Conclusions:

• Dose from floor-scattered electrons can be clinically significant in TSEI.
• This dose contribution should be considered during treatment planning and commissioning.
• MC simulations are a suitable method for evaluating floor scatter effects.