近年來，醫院內的診斷部門紛紛將X光攝影轉換成數位攝影，數位攝影的技術優點，例如寬廣的對比動態範圍、後處理功能、多重影像切看方式、電子傳送等等，但是數位攝影所用之數位偵檢器寬廣的動態範圍，會使它較難分別過度暴露或暴露不足的程度。放射診斷所要達到的最優化，在於尋求能到達到診斷疾病的目的亦能使病人得到較低的輻射劑量，也就是合理抑低(as low as reasonably achievable, ALARA)。
　　本研究之目的在於研究輻射劑量與影像品質的最優化條件，首先採討改變各項照射條件對同一台X光機所造成之影響，並找出其最優化條件；其次，比較不同X光機廠牌的最優化照射條件；最後，判斷各台X光機之自動暴露控制設定是否適當。
　　研究結果證明，在管電壓越高時，及在開啟自動暴露控制下，輻射劑量與影像品質都會降低；而增加附加濾片厚度後，劑量會明顯下降。比較不同機器，在使用Philips、Toshiba、Hologic三家X光機，以Philips之102 kVp搭配自動暴露控制為較合適之條件。最後在判斷X光機之自動暴露控制之實驗，以廠商建議之管電壓採用自動暴露控制以及與自動暴露控制鄰近之管電流作比較，自動暴露控制之管電流都能達到最優化的結果。

In recent years, medical diagnostic departments gradually changed their imaging modality to the digital radiography. Digital radiography has its advantages, for example, broad dynamic range of contrast, post-process functions, multiple ways of viewing images, electronic transferring data etc. The broad dynamic range made it more difficult to detect over-exposure or under-exposure. Therefore, optimization is important in radiological diagnosis in order to reach the lowest patient’s dose but yet to maintain the required image quality level. This is the principle of as low as reasonably achievable, ALARA.
The purpose of this study was to investigate the optimization techniques in terms of radiation dose and image quality. First, realize how the technical conditions to influence image quality for the same X-ray machine, and then seek the optimal condition. Secondly, compare the optimal condition of X-ray machines for different manufacturers. Judge if it is proper to use automatic exposure control (AEC) setup of each X-ray machine finally.
The results of this research prove that the higher tube voltage used under AEC, the lower radiation dose and image quality. After increasing the thickness of added filter, radiation doses obviously drop. For the comparisons between x-ray machines of three manufactures, Philips, Toshiba and Hologic, regard Philips’ machine using 102 kVp under AEC as more suitable condition. Finally, in the experiment of judging automatic exposure control, comparing automatic exposure control with neighboring tube currents, automatic exposure control will reach the optimal condition.

中文摘要
英文摘要
目錄 i
圖目錄 iv
表目錄 vi
第一章　緒論 1
1.1研究目的 1
1.2實驗架構 2
第二章　實驗器材 4
2.1數位放射攝影 4
2.1.1X光管 4
2.1.2直接與間接偵檢器系統 6
2.1.3自動暴露控制系統 8
2.2輻射劑量 9
2.2.1熱發光劑量計 9
2.2.2劑量面積乘積游離腔 11
2.3影像品質 11
2.3.1影像品質指標 12
2.3.2價值數值 12
2.3.3對比解析板 13
第三章　實驗步驟與方法 20
3.1熱發光劑量計 20
3.2使用不同照射條件之比較 23
3.3不同X光機之半值層實驗 24
3.4使用不同X光機之比較 25
3.5自動暴露控制與固定管電流之實驗 26
3.6影像觀看方式 26
第四章　結果與討論 30
4.1熱發光劑量計校正實驗 30
4.2改變照射條件之實驗 37
4.3使用不同X光機之比較 43
4.4自動暴露控制與固定管電流之比較 52
第五章　結論 58
參考文獻 60

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