陳拓榮Tou-Rong Chen張宜儒Yi-Ru Chang生物醫學科學學系碩士班2026-03-189999-12-312015https://handle.ncl.edu.tw/11296/qgnd4thttps://scholars.csmu.edu.tw/handle/123456789/5891研究目的：本實驗的目的是應用雙能量電腦斷層儀掃描結石，探討可辨識尿酸結石的分析方法，藉由參考管電流時間積(Ref. mAs)的設定，探討造成受檢者有效劑量抑低的操作設定與分析方法的準確性。 材料與方法：本實驗一共收集132顆尿路結石。結石被放置於直徑分別16及32公分的壓克力圓柱假體和有效體寬分為25及38公分的類橢圓聚乙烯假體，以模擬結石於人體中。使用Siemens雙源雙能(100/Sn 140 kVp)的電腦斷層進行掃描，以Siemens後處理分析系統之kidney stone運算法重組成腎結石影像，區分尿酸及非尿酸結石。另外，實驗影像也以FBP重組，可得兩組能量影像，經由CT工作站圈選ROI，得到兩組對應的CT值，使用DE ratio和象限法這二種方法來辨識是否為尿酸結石。研究也探討由雙能量重組單能量影像的特性，評估尿酸結石與非尿酸結石的差異，分析計算其準確性、靈敏度和特異性。以上方法均搭配三到四種不同參考劑量掃描水平。結果： 尿酸結石相較於其它種類結石，在高低管電壓下的CT值接近，DE ratio小於1.13。使用kidney stone運算法來重組影像，將兩組能量(100/Sn 140 kVp)的Ref. mAs設定在53/41 mAs，仍有98%的準確性。而使用象限法來辨識尿酸結石，可發現ROI之CT值分布於第三象限，即Sn 140 kVp影像CT值小於648 HU、100 kVp影像CT值小於737 HU，且當Ref. mAs設定在27/21 mAs仍有90%的準確性。在重建單能量影像方法探討，本文發現在60 keV~80 keV這個區段，尿酸結石與非尿酸結石斜率二者存在最大的差異，本研究利用此區段尿酸結石斜率近於零(範圍在-3.3~-7.2 HU/keV)的特性辨識尿酸結石，其準確性達92%、靈敏度為100%、特異性也達92%，且經ROC curve和AUC分析，可發現在降低劑量後，使用700~800 HU為閾值的尿酸結石辨識力並無差別。結論：使用雙源雙能電腦斷層後處理辨識尿酸結石之準確率為98%，較人為圈選佳。結石的大小厚薄，可能左右影像CT值。將象限法的中心點設定為(648, 737)，使用第三象限判斷尿酸結石，可降低有效劑量並保持相當的準確度。模擬得之單能量60-80 keV區段，以其斜率判斷，有著最佳尿酸結石辨識率，且尿酸結石與非尿酸結石在50 keV時有著最大的差異，值得進一步研究探討與廠商軟體的開發。藉由縮短掃描長度與抑低Ref. mAs，可將有效劑量抑低至IVP或KUB的等級。PurposeThe purpose of this study is using dual-energy computed tomography (DECT) to evaluate different analysis methods of identification for uric acid stones. By adjustment of the reference tube current time product (Ref. mAs), the effective dose reduction of patient and the identified accuracy of methods were assessed.Material & MethodA total of 132 urinary stones were collected in the study. Stones are placed in the CTDI acrylic phantoms with 16 and 32 cm diameter and in the 25 and 38 cm elliptic-like polyethylene phantoms to simulate stones in the human body. Phantoms were scanned by Siemens dual-source dual-energy, 100 / Sn 140 kVp, and the images reconstructed automatically by the program, a built-in analysis software in CT workstation, that can distinguish uric acid stone by a color-coded method. In addition, the images were reconstructed by the filtered back projection method. ROIs of two energy images for 100 and Sn140 kVp were manual selected directly on CT monitor of workspace and their corresponding CT numbers were recorded. The CT number ratio (DR ratio) and quadrant methods were used to identify uric acid stones from the images produced by three to four reference dose levels. The monoenergetic images also reconstructed to assess stones. The analysis items include accuracy, sensitivity and specificity.ResultThe CT numbers of uric acid stones are similar compared to other kinds of stones in two tube voltages. The DE ratio is less than 1.13 and it agrees with other studies. Using the Ref. mAs of 53/41 mAs(100 / Sn 140 kVp) to scan and the kidney stone program to reconstruct the image and the accuracy is 98%. The quadrant method that are the CT no. less than 648 HU for Sn 140 kVp and 737 HU for 100 kVp, with the scan of the Ref. mAs setting at 27/21 mAs still had 90% accuracy. In monoenergetic images, the range of 60 to 80 keV is optimized to distinguish the uric acid stones and non-uric acid stones. In the monoenergetic method, the slope of uric acid stone was in the range of -3.3 ~ -7.2 HU / keV. The accuracy was more than 92%, sensitivity was 100%, and the specificity was more than 92% of identification of uric acid stones. By analysis of ROC curve and AUC can be found there are undifferentiated by using lower scanning dose parameters setting to identify uric acid or non- uric acid when the threshold set at 700 ~ 800 HU value .ConclusionUsing the analysis by the Siemens DECT kidney stone program, the accuracy of uric acid stone is 98% and is better than that identified by personal judgment. Stone size and its thickness could affect the CT number of voxel. The quadrant method, setting the center at (648, 737) and using the third quadrant to identify uric acid stones, can reduce the effective dose and maintain a considerable accuracy. The range of 60 to 80 keV of monoenergetic images presented the best accuracy of uric acid stones by analyzing the slope. Uric acid and non-uric acid stones have the largest difference at 50 keV images. The monoenergetic method may be an innovative method that is worthy to study and develop application software by manufacturers. By the strategy of reducing scan length and Ref. mAs, the effective dose can be decreased to the dose level of KUB or IVP examination.雙能量電腦斷層尿酸結石假體有效劑量dual energycomputed tomographyurinary stonephantomeffective dosethesis