CR影像板之使用次數對影像品質的影響

自1980年開始發展數位化X光儀器以來，目前幾乎所有的放射診斷部門傳統使用的X光片攝影系統皆已被數位X光系統所取代，而電腦放射攝影系統(computed radiography, CR)則是其中一個被廣泛使用的取代技術，然而目前所使用的CR系統其使用壽命依照原廠的建議值為15,000次或7年，但並無相關文獻資料可供佐證，本研究的目的為確認影像板重覆使用後，其照射次數及使用時間對影像品質所產生的影響。。本研究採用假體來模擬人體胸部之結構，並使用Philips optimus 50搭配AGFA CR片匣(MD4.0,14×17 inch)，依照胸部X光攝影條件(70 kVp,1.6 mAs及60 kVp,1.0 mAs)，針對影像板分別執行15,000次照射，取得CR之影像後進行調制傳遞函數(modulation transfer function, MTF)分析。藉由實驗結果得知，經照射15,000次後之影像板，其MTF值的衰退範圍介於4.7%～6.4%之間，而使用時間超過7年之影像板，其MTF值的衰退範圍則介於14.43%～ 21.08%之間，顯示影像板會隨著照射次數的增加而產生衰退的情況，且使用時間亦會對影像板的衰退造成影響，而且當影像板產生衰退後，增加劑量亦無法對衰退後的MTF值產生補償的作用。藉由本研究的結果，針對臨床上影像板的使用，建議應建立詳細的影像板資料，且在使用時間達到原廠所建議的7年之後，則不論照射次數之多寡，皆應進行汰換該影像板，以免因影像品質衰退幅度過大影響臨床之醫療診斷，而針對使用次數超過15,000次之影像板，則建議應以客觀方法測量其影像品質衰退程度，以確保影像品質。

關鍵字

電腦放射攝影系統；影像板；調制傳遞函數

並列摘要

There is little research to indicate the life of the IP. The manufacture suggest a best quality by using IP is 15000 times or 7-years. No evidence is provided by researchers to date. The study conducted serial experiments to answer this question by means of phantom study. All images in this study have been made with the Philips optimus 50 roentgen system. AGFA ADC Compact Plus CR reader with MD4.0(14x17 inch) plates are used in this study. An ACR phantom simulated a relevant density to a real human body and was taken over 15,000 times. Each image was recorded and analyzed by MTF(modulation transfer function) to evaluate the image quality by frequent using it. The image plate after exposed for 15,000 times, its MTF value''s decline range is between 4.7%~6.4%. Image plate of the service time of over 7 years, its MTF value’s decline range is between 14.43%~21.08%. The result reveals that increases expose the number of times will make the image plate degradation, and service time will cause the image plate to degrade. It is unable to form the compensation to the image plate degrading to increase the dose. Propose setting up the detailed information of using with image plate used on clinic via results. So long as use for over 7 years no matter how many times of image plates is used should be changed, because the image plate degrading will influence clinical diagnosis. Exposing more than 15000 times image plate should measure the intensity of degrading of image quality in order to prevent image quality from influencing clinical diagnosis.

並列關鍵字

MTF ； computed radiography ； image plate

參考文獻

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國際替代計量

CR影像板之使用次數對影像品質的影響

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