Optimising electron beam 6 MeV radiotherapy: field-size-dependent dosimetric impact of perforated thermoplastic immobilisation masks
Year: 2026
Type: article
Abstract: Background. Thermoplastic immobilisation masks are widely used in head and neck radiotherapy to ensure patient stability and reproducible positioning during treatment. Because these masks are placed directly in the beam path and consist of perforated polymer materials, they may influence electron dose distributions through additional attenuation and scattering effects, particularly for low-energy electron beams. This study quantifies the dosimetric effects of perforated thermoplastic masks, considering different hole diameters and electron field sizes. Materials and methods. Monte Carlo simulations using GATE modelled 6 MeV electron beams passing through thermoplastic masks with 2 mm and 4 mm hole diameters across 3 × 3 cm 2 , 6 × 6 cm 2 , and 10 × 10 cm 2 fields. Surface dose (D 0 ), depth of maximum dose (R 100 ), isodose depths (R90, R50), penumbra, flatness and gamma analysis (2%/2 mm and 3%/3 mm) were evaluated. Results. Masks increased D 0 up to +5.9% for 2 mm holes and +4.18% for 4 mm holes. R100 showed up to –21.43% reduction for 2 mm masks, with lesser shifts using 4 mm holes. Penumbra widening was also detected, with a maximum relative increase of +4.40% at Z max for the 6 × 6 cm 2 field using the 2 mm mask. Gamma pass rates were better for 4 mm masks, especially at shallow depths. Conclusions. Masks with 4 mm perforations consistently outperformed 2 mm variants in dosimetric accuracy while maintaining effective immobilisation. Tailored mask selection based on field size improves clinical outcomes in electron beam radiotherapy.
DOI: 10.5603/rpor.113327
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,713
OpenAlex ID: W7168238992