Skin dose reduction by a clinically viable magnetic deflector

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• High-energy X-rays from linear accelerators can increase radiation skin dose.
• Reducing surface dose is crucial for patient safety and treatment efficacy.

Purpose of the Study:

• To evaluate the effectiveness of a variable magnetic deflector in reducing skin dose for 6MV X-ray beams.
• To assess the impact of field size and source-surface distance (SSD) on dose reduction.

Main Methods:

• A magnetic deflector constructed with Neodymium Iron Boron (NdFeB) rare earth magnets was attached to a linear accelerator treatment head.
• The deflector's adjustable gap allowed for optimized magnetic field strength (up to 0.55 Tesla) across various field sizes (up to 35 cm x 35 cm).
• Skin dose measurements were taken with and without the deflector at 100 cm SSD, considering a 10 mm perspex block tray.

Main Results:

• The magnetic deflector reduced surface dose by up to 65% for 6MV X-rays.
• Specific reductions observed were from 29% to 14% (20 cm x 20 cm field) and 59% to 37% (35 cm x 35 cm field).
• A minimum of 10 cm space between the deflector and the patient was found necessary for effective electron contaminant removal.

Conclusions:

• The variable magnetic deflector is an effective accessory for linear accelerators to significantly lower radiation skin dose.
• This technology offers a practical method for enhancing patient safety in radiation therapy by mitigating electron contamination.
• Proper spacing is essential for maximizing the skin dose reduction benefits of the magnetic deflector.