臺灣博碩士論文加值系統

本論文針對數位化乳房X光攝影系統進行劑量評估，利用美國放射線醫學會之乳房攝影假體，測量不同照射條件下的輻射劑量，與影像品質的變化，推估出最適於4.5公分厚假體的攝影條件為30 kVp、47.7 mAs。在此攝影條件下之平均乳腺劑量為1.40 mGy，有效劑量為0.07 mSv，而此有效劑量並未高於大多數常見放射線檢查項目，且其值亦遠低於年平均天然游離輻射劑量(約為其1/34)，因此民眾可安心接受乳房攝影檢查。
臨床上執行乳房攝影之優先考慮因素為影像品質，本論文亦針對此進行實驗。實驗結果發現，與傳統乳房X光攝影系統相較之下，數位乳房X光攝影可以較低之平均乳腺劑量，而得到較佳的影像品質，因此其確實可達到降低病患輻射劑量的效果。
本論文使用游離腔、熱發光劑量計、以及照射發光玻璃劑量計做為輻射劑量測量工具，並比較各種劑量計之測量結果。使用照射發光玻璃劑量計測量時，由於其密度較大，故於影像上呈現高光密度，而有可能會擋住病灶，因此不適合放置於假體或乳房表面進行劑量測量。實驗結果發現，熱發光劑量計及照射發光玻璃劑量計的測量值除了24 kVp時有低估之現象外，於其他管電壓峰值時的測量結果皆與游離腔相當符合，熱發光劑量計之測量結果與游離腔之差異皆在6%以內，而照射發光玻璃劑量計之測量結果與游離腔之差異皆小於5%。

The purpose of this study was to estimate the radiation dose of the digital mammography system. The radiation dose and image quality of different exposure setting were estimated with the standard American College of Radiology (ACR) phantom. The results showed that the most suitable exposure setting was 30 kVp and 47.7 mAs. The mean glandular dose at 30 kVp and 47.7 mAs was 1.40 mGy, and the effective dose was 0.07 mSv. The effective dose of 0.07 mSv was about 1/34 of the natural background radiation exposure per year.
In this study, a comparison in mean glandular dose of digital mammography system to that of traditional mammography system was conducted. The results showed that the digital mammography system can provide better image quality with lower mean glandular dose.
Measurement of mean glandular dose in this study was proceed with ionization chamber, thermoluminescent dosimeters (TLDs), and radiophotoluminescent glass dosimeters (RPLGDs). Because of the high density of RPLGDs, the measurement of mean glandular dose with RPLGDs placed on the surface of the phantom was not adaptable. The experimental results indicated that the mean glandular dose measured by TLDs and RPLGDs was comparable to ionization chamber, expect for the tube voltage of 24 kVp. The difference between TLDs and ionization chamber was within 6%, and the difference between RPLGDs and ionization chamber was within 5%.

誌謝 I
摘要 II
ABSTRACT III
目錄 IV
圖目錄 VI
表目錄 VIII
第一章 序論 1
1.1 前言 1
1.2 目的 5
1.3 論文架構 6
第二章 理論基礎 7
2.1 輻射與物質的作用 7
2.1.1 光子與物質的作用 7
2.1.2 帶電粒子與物質的作用 11
2.2 劑量量測工具 14
2.2.1 游離腔 14
2.2.2 熱發光劑量計 14
2.2.3 照射發光玻璃劑量計 17
2.3 乳房X光攝影 22
2.3.1 乳房X光攝影簡介 22
2.3.2 數位化乳房X光攝影簡介 24
第三章 材料與方法 28
3.1 實驗設備 28
3.1.1 游離腔 28
3.1.2 熱發光劑量計與計讀系統 30
3.1.3 照射發光玻璃劑量計與計讀系統 32
3.1.4 乳房X光攝影系統 35
3.1.5 美國放射線醫學會乳房攝影假體 37
3.2 實驗方法 39
3.2.1 熱發光劑量計之篩選 39
3.2.2 照射發光玻璃劑量計之篩選 41
3.2.3 半值層測量 43
3.2.4 輻射劑量測量 46
第四章 結果與討論 53
4.1 劑量計篩選 53
4.2 半值層測量 58
4.3 輻射劑量測量 59
第五章 結論 76
參考文獻 78
附錄 80
附錄A. 回散射因子 80
附錄B. 熱發光劑量計測量值之修正 82
附錄C. 照射發光玻璃劑量計測量值之修正 83

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