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Showing 2 results for Mosfet
Dr. S. Barlaz Us, E. Kaya Pepele,
Volume 15, Issue 1 (1-2017)
Abstract
Background: The purpose of this study was to investigate the various gantry angle and SSD dependencies of TLD and MOSFET dosimeters. Materials and Methods: LiF (Mg) TLD and MOSFET were used in this study. Dosimeter systems were calibrated and then irradiated at various gantry angle and SSD by applying 6 MV photon energy. Results: Based on the results, MOSFET changes were found to be in 2% range between ±50º gantry angles and the rate of dose change was found to be increasing as gantry angle was at the extremes of graph. This increase was especially obvious in tail end of the asymmetric axes. Change in the gantry angle dependency of TLD was -2% till ± 60º gantry angle and -5% between 60º to 90º. Dependency of SSD was ±1% for TLD and MOSFET. Conclusion: Results indicate that properties of dosimeters must be well known by users for accurate determination of the entire doses on the patient. These observations may lead to better treatment quality and prevention of probable dose errors.
Ph.d., N.d. Kesen, C. Koksal,
Volume 18, Issue 4 (10-2020)
Abstract
Background: The accuracy and the reproducibility of radiotherapy can be provided by using immobilization devices such as thermoplastic masks. In head and neck cancer radiotherapy, the patients are mostly immobilized by using thermoplastic masks. In this study, the effect of the thermoplastic mask to the surface and buildup region doses was investigated by using Markus parallel plate ion chamber, Gafchromic EBT3 film and MOSFET detector for the same field size and different beam angles. Materials and Methods: The measurements were made in a water equivalent solid phantom at the surface and in the buildup region of the 6 MV photon beams at 100 cm source-detector distance for 10 × 10 cm2 field size and beam angles of 0°, 30°, 60° and 80° with and without thermoplastic mask. Results: The surface doses in 0.07 mm depth using 6MV photon beams without a thermoplastic mask for 10 × 10 cm2 field size were found 20.3%, 18.8%, and 41.5% for Markus chamber, EBT3 film, and MOSFET detector, respectively. The surface doses using 6 MV photon beams with a thermoplastic mask for 10 × 10 cm2 field size were found 38.4%, 51.7% and 50.2% for Markus chamber, EBT3 film, and MOSFET detector, respectively. Conclusion: The thermoplastic masks placed on the surface of the medium affect the surface and buildup region doses. The effect of thermoplastic masks to surface and buildup region doses should be determined before use clinically.
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