低劑量電腦斷層篩檢肺部小結節之影像分析及劑量評估

Evaluation of Image Quality and Radiation Dose in Low-Dose Computed Tomography for Diagnosis of Pulmonary Nodules

陳鏗鏘(Keng-Qiang Chen) ； 郭瓊文(Chiung-Wen Kuo) ； 黃俊肇(Jun-Zhao Huang) ； 陳淑敏(Shu-Min Chen) ； 鄭天榮(Tian-Rong Zheng) ； 劉秋霞(Qiu-Xia Liu) ； 陳素秋(Su-Chiu Chen) ； 楊斐適(Fei-Shih Yang)

《中華放射線技術學雜誌》 41卷3期 (2017/09) Pp. 131-138

摘要

低劑量電腦斷層（low-dose computed tomography, LDCT）早期肺癌篩檢檢查，可提高檢出率，及早發現肺部疾病。本研究目的為分析不同廠牌的電腦斷層掃描儀受檢者之影像，並針對其使用的參數與輻射劑量，進行探討。本研究以回溯方式，選取對象為2015 年1 月到3 月間，於馬偕紀念醫院三台不同廠牌電腦斷層掃描儀（A、B、C 三組）中，以隨機方式，各自選取50 位早期肺癌篩檢之健檢人員，共150 人。所有CT 檢查皆未注射顯影劑，而掃描參數設定管電壓固定為120 kVp 及管電流固定為20 mAs，實際管電流為自動曝光控制系統（automatic exposure control, AEC）依據受檢者體型調控。所有影像皆由2 位放射科主治醫師，以單純型毛玻璃霧狀病變結節進行影像品質分析。研究結果顯示A、B 和C 三組的容積電腦斷層掃描劑量指數（volume CT dose index, CTDI_(vol)）分別為1.31±0.22 mGy、1.7±0.29 mGy 及1.94±0.43 mGy (p＜0.05)。平均有效劑量（effective dose, E）分別為0.63±0.12 mSv、0.92±0.18 mSv 及0.95±0.23 mSv (p＜0.05)。而在主治醫師影像品質判讀結果，三組影像中可分辨出的最小結節直徑分別為1.6 mm、1.6 mm 及1.4 mm；判讀影像之準確性，不受身體質量指數和掃描參數所影響。另外，建議降低管電流與管電壓、增加螺距、快速旋轉時間、多排列數掃描儀、減少受檢者掃描長度和採用自動曝光控制系統，皆可以有效降低輻射劑量。

關鍵字

低劑量電腦斷層 ； 肺部小結節 ； 影像分析 ； 劑量評估

並列摘要

The use of low-dose computed tomography (LDCT) early lung cancer screening test can improve the detection rate and help early detection of lung disease. The purpose of this study is to measure the radiation dose of this exam, and to evaluate the use of parameters for image analysis. This study was a retrospective study with subject selection from January 2015 to March 2015. All subjects received LDCT in one of three computer tomography scanners (A, B, and C) at Mackay Memorial Hospital. For each scanner, 50 cases were randomly selected out from subjects referred from the Health Examination Center. The total case number was 150. All of the CT examinations were performed without contrast injection. The parameter setting was the following: fixed voltage of 120 kVp and 20 mAs with the actual tube current adjusted by the automatic exposure control system (AEC) according to the subject body size. The analysis of image quality was performed by two experienced radiologists and was based on the minimal size of the detected simple ground glass opacities in each exam. The results showed CT dose volume index (CTDI_(vol)) in A, B and, C groups were 1.31±0.22 mGy, 1.7±0.29 mGy, and 1.94±0.43 mGy (p＜0.05) and mean effective dose (effective dose, E) were 0.63±0.12 mSv, 0.92±0.18 mSv, and 0.95±0.23 mSv (p＜0.05). In the image quality evaluation based on radiologists' interpretation of the results, the minimal lesion sizes in the images from these three CT scanners were 1.6 mm, 1.6 mm, and 1.4 mm, suggesting indifference of the imaging quality among these three scanners. The imaging quality was not affected by body mass index and scanning parameters. In addition, in order to effectively reduce the radiation dose, it is recommended to reduce tube voltage and current, increase the pitch, fast rotation time, multi-array number scanner, reduce the length of the subject scan, and use automatic exposure control system.

並列關鍵字

low-dose computed tomography ； pulmonary nodules ； imaging analysis ； dose assessment