Open AccessSurface and the Build-up Dose Distribution Due to Applying Thermoplastic Masks in External Radiotherapy
Author(s) -
Tayyeb Allahverdi Pourfallah,
Masoud Pirzadeh,
Danial Seifi Makrani,
Ehsan Mihandoust,
Saeed Davodian
Publication year - 2021
Publication title -
frontiers in biomedical technologies
Language(s) - English
Resource type - Journals
eISSN - 2345-5837
pISSN - 2345-5829
DOI - 10.18502/fbt.v7i4.5319
Subject(s) - materials science , imaging phantom , thermoplastic , dosimetry , linear particle accelerator , irradiation , reproducibility , nuclear medicine , optics , biomedical engineering , composite material , physics , mathematics , medicine , beam (structure) , nuclear physics , statistics
Background: Thermoplastic immobilization devices are used to position the patient on the table in order to correctly reposition the patient during treatment courses.
Objective: The Purpose of this work is investigating the degradation of surface dose and the dose distribution in the build-up region for photon beams associated with immobilization devices using Gafchromic films.
Materials and Methods: After heating, these masks are stretched and fitted over the considered location of body before treatment simulation for insuring the reproducibility of patient position during treatment fractions. In this research, dosimetry was carried out using Gafchromic EBT3 film and three kinds of thermoplastic masks (Orfit with thickness 2.2mm, holes diameter 2.5mm, Orfit with thickness 2mm, holes diameter 1mm, and Klarity mask, thickness 2mm, holes diameter 3mm). Measurements were made with and without the mask materials on the surface of the Perspex phantom for 6 and 15 MV X-ray beams of a LINAC machine.
Results: The results showed that surface dose increases 2.1 to 6.7 times and 2 to 3.9 times than the surface dose in the open field for 15 MV and 6 MV photons, respectively. According to the obtained results from the Analyses of Variances (ANOVA) test , it is defined that there is a significant difference in surface dose among three kind of thermoplastic masks (χ2=49.78 and df=3 and P 0.05).
Conclusion: According to the results, Klarity mask is more acceptable immobilization device when compared with other masks in the test.