TITLE:
Dosimetric Effects of Thermoplastic Immobilizing Devices on Surface Dose
AUTHORS:
Olivia Adu-Poku, Eric Kotei Addison, Cyril Schandorf, Francis Hasford, Stephen Inkoom, Joseph Adom, Akosah Kingsley, Eunice Arthur, Linus Owusu-Agyapong
KEYWORDS:
Thermoplastic Mask, Percentage Depth Dose, Equivalent Thickness of Water, Skin Dose
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.11 No.1,
January
24,
2022
ABSTRACT: Thermoplastic immobilizing masks have dosimetric effects on the patient’s skin dose. The thermoplastic percentage depth dose
(PDD), equivalent thickness of water for the masks and surface doses
were determined. The surface dose factors due to the thermoplastic
mask was found to be 1.7949, 1.9456, 2.0563, 2.1967, 2.3827, 2.5459 and
2.6565 for field sizes of 5 × 5, 8 × 8,
10 × 10, 12 × 12, 15
× 15, 18 × 18 and 20 × 20 cm2 respectively which shifted the percentage depth dose curve to lower
values. The physical thermoplastic thickness was measured to be between 2.30 and 1.80 mm, and the equivalent thicknesses of water, de, were determined to be between 1.2 and 1.00 mm. This meant that, as the mask thickness decreased, its water equivalent
thickness also decreased. The presence of the mask material increased the skin
dose to a factor of 1%. The thermoplastic mask factor was also found to be 0.99.