Optimising electron beam 6 MeV radiotherapy: field-size-dependent dosimetric impact of perforated thermoplastic immobilisation masks.
4 affiliations
- 1LPPMOIA, Faculty of Sciences, Mohammed First University, Oujda, Morocco.
- 2Department of Radiation Oncology, Hassan II Oncology Centre, Mohammed VI University Hospital, Oujda, Morocco.
- 3National Institute of Particle Physics and its Application, Oujda, Morocco.
- 4LaRSA, National School of Applied Sciences, Mohammed First University, Oujda, Morocco.
Abstract
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. 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 cm2, 6 × 6 cm2, and 10 × 10 cm2 fields. Surface dose (D0), depth of maximum dose (R100), isodose depths (R90, R50), penumbra, flatness and gamma analysis (2%/2 mm and 3%/3 mm) were evaluated. Masks increased D0 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 Zmax for the 6 × 6 cm2 field using the 2 mm mask. Gamma pass rates were better for 4 mm masks, especially at shallow depths. 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.
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BibTeX
@article{rezzoug2026optimising,
title = {{Optimising electron beam 6 MeV radiotherapy: field-size-dependent dosimetric impact of perforated thermoplastic immobilisation masks.}},
author = {Mohammed Rezzoug and Yassine Oulhouq and Omar Hamzaoui and Mustapha Zerfaoui and Abdeslem Rrhioua and Dikra Bakari},
journal = {Reports of practical oncology and radiotherapy : journal of Greatpoland Cancer Center in Poznan and Polish Society of Radiation Oncology},
year = {2026},
month = nov,
doi = {10.5603/rpor.113327},
url = {https://europepmc.org/article/MED/42997874},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Optimising electron beam 6 MeV radiotherapy: field-size-dependent dosimetric impact of perforated thermoplastic immobilisation masks.
AU - Mohammed Rezzoug
AU - Yassine Oulhouq
AU - Omar Hamzaoui
AU - Mustapha Zerfaoui
AU - Abdeslem Rrhioua
AU - Dikra Bakari
PY - 2026
DA - 2026/11/01
JO - Reports of practical oncology and radiotherapy : journal of Greatpoland Cancer Center in Poznan and Polish Society of Radiation Oncology
DO - 10.5603/rpor.113327
UR - https://europepmc.org/article/MED/42997874
AB - 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. 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 cm2, 6 × 6 cm2, and 10 × 10 cm2 fields. Surface dose (D0), depth of maximum dose (R100), isodose depths (R90, R50), penumbra, flatness and gamma analysis (2%/2 mm and 3%/3 mm) were evaluated. Masks increased D0 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 Zmax for the 6 × 6 cm2 field using the 2 mm mask. Gamma pass rates were better for 4 mm masks, especially at shallow depths. 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.
SN - 1507-1367
SN - 2083-4640
ER -