Evaluating the induced photon contamination by different breast IOERT shields using Monte Carlo simulation.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Breast intraoperative electron radiotherapy (IOERT) utilizes radioprotection disks to minimize healthy tissue over-exposure.
• Contaminant photons generated by shielding disks during IOERT are a concern for patient safety.

Purpose of the Study:

• To evaluate the photon contamination from commonly used double-layered shielding disks (PMMA+Cu, PTFE+steel, Al+Pb) during breast IOERT.
• To compare the contaminant dose beneath these disks using Monte Carlo simulations.

Main Methods:

• Monte Carlo (MC) simulations using MCNPX (version 2.6.0) were performed.
• Electron beams of 6, 8, 10, and 12 MeV were used to irradiate shielding disks within a water phantom.
• Energy spectra and contaminant doses at various disk surfaces and beneath the disks were determined.

Main Results:

• No significant photon contamination was observed for shielding disks at electron energies up to 10 MeV.
• At 12 MeV, contaminant photon dose beneath the disks exceeded levels seen without disks.
• The Al+Pb disk showed the best performance for dose reduction at 6-10 MeV, while PMMA+Cu was best at 12 MeV.

Conclusions:

• Shielding disks generally absorb, rather than produce, significant photon contamination from 6-10 MeV electron interactions.
• A minor increase in contaminant dose was noted at 12 MeV, but it remained below tolerance levels for healthy tissues.
• The studied disks are effective in managing radiation dose during breast IOERT within the evaluated energy range.