| Summary: | 碩士 === 中臺科技大學 === 放射科學研究所 === 96 === Since Computed Tomography was invented in 1970s, it has turned to be a landmark in medical images of radiological diagnosis. As medical technology evolves, more and more high-speed scanners and extensive application mechanisms are generated. Nowadays, Computed Tomography is an invaluable tool in the department of radiology.
The purpose of this study is to evaluate the radiation dose of head and neck in dental CT: i-CAT and ASAHI-PSR9000NT, compared with 64/4 multi slice CT: TOSHIBA-Aquillion 64 slice and GE-LightSpeed 4 slice. The experiments to get the radiation dose in anthropomorphic Alderson-Rando phantom were performed by changing parameters of FOV, kVp, and mAs. Thermoluminescent dosimeters (TLD-100: thin type) were used in this study. TLDs were inserted or pasted on the Rando phantom, and the doses were estimated in critical organs or tissue of head and neck, then the effective dose could be calculated according to ion chamber with electrometer measurement, and summarized the equivalent dose with tissue weighted factor of ICRP60 report.
In this study, the doses of head and neck contributed by dental CT is 0.025~0.384 mSv, and the dose contributed from 64/4 multi slice CT is 0.278~2.248 mSv. For dental CT, the effective dose descends about 52.34% when the FOV is smaller. The one descends 73.46% when mAs is cut down, and the one descends at most 25.23% when kVp adjusted lower. Besides, doses could descend over seven times as mAs is cut down in 64/4 multi slice CT. Moreover, dose undulated in skin and neck could add shielding to protect it.
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