Evaluation of back scattering dose in hand-made oral phantom by linear accelerator exposure

• Main Authors: Wei-Kai Liao, 廖韋凱
• Other Authors: Jih-Hung Chiu
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/58sj83

碩士 === 元培科技大學 === 放射技術研究所 === 99 === During the radiotherapy for head and neck tumors, the oral cavity and cheek area would be inevitably exposed to high-energy radiation, thus the material surface of the teeth, dental restorations with high atomic number, or alloy prosthodontics would generate backscatter electrons that cause the buccal mucosa adjacent to these materials to receive a localized high dose enhancement, which primarily leads to side effects or oral mucositis in patients. Based on the size of the adult oral cavity, this study aimed to use acrylic resin to make an oral prosthesis with two grooves on the left and right sides for placing three molars. Moreover, the distance between the inner cheek and the side surface of the teeth could be accurately adjusted every 1 mm from 0 mm to 5 mm. This enhanced the dose in the buccal mucosa during head and neck radiotherapy and made the distribution measurement of the radiation dose simple and feasible at different depths (0 mm ~ 5 mm). Meanwhile, the study employed the film type TLD (thermoluminescent dosimeter) with a thickness of 0.1 mm to measure the absorbed dose inside the buccal mucosa in order to reduce the dose interference from the x-ray treatment. The study fixed three real molars in a row located both left and right sides of the prosthesis, and employed 6 MV photons and IMRT (intensity modulated radiation therapy) to treat and simulate oral cancer, as well as measure the attenuation of the molar’s backscatter dose from 0 mm to 5 mm in an up-beam direction. The experiments showed that every 3 mm, the prosthesis had attenuated the enhancement of backscatter dose under 3%. The irradiation dose enhancement in a single direction was twice higher than through IMRT 7-field treatment; these measurement results were consistent with the results of previous studies.