Yamamura J, Wildberger J E, Nagel H-D, Dichtl D, Adam G, Wedegärtner U
Klinik und Poliklinik für Diagnostische und Interventionelle Radiologie, Universitätsklinikum Hamburg-Eppendorf.
Rofo. 2009 Jun;181(6):549-55. doi: 10.1055/s-0028-1109190. Epub 2009 Mar 20.
The purpose of this study was to optimize high-resolution MSCT chest protocols for the evaluation of symptomatic immunosuppressed patients with suspected pneumonia using a dose-simulating program.
Using the MSCT (Siemens, Erlangen, Germany), 30 immunosuppressed patients with suspected pneumonia were examined with a low-dose HRCT of the chest (120 kV, 100 eff.mAs and collimation of 4 x 1 mm). A dose-simulating program was used to reconstruct the raw data at four different dose levels (70, 50, 35 und 25 mAs). For dose simulation for each mAs product, the correspondent noise level was added to the data. Images were generated with a slice thickness of 1 mm and 5 mm in the lung window. The images were then evaluated independently by two radiologists and graded on a scale of 1 to 3 points: 1 = no pneumonia, 2 = unclear, 3 = pneumonia. A receiver operating curve (ROC) analysis was performed to calculate the area under the curve (AUC). The actual dosage in mSv was calculated. The sensitivity and specificity were evaluated.
Out of 30 patients, 7 had a normal chest finding and 23 had pneumonia. The area under the ROC curve (AUC) was 1.0 for every dosage and slice thickness. Infiltrates were detected correctly for all dosage levels. The sensitivity was 100 % for all dose levels and slice thicknesses. There was one false positive finding at 35 mAs and 1 mm slice thickness. At this dose level the specificity was reduced to 93 %. A reduction to 25 mAs had no influence on the detection of pneumonia. Thus, MSCT examinations of the chest can be performed with 25 mAs without missing the right diagnosis, resulting in an effective dose of 1.15 mSv (men), 1.5 mSv (women) and a CTDIvol of 2.5 mGy.
For the evaluation of pneumonia in immunocompromised patients, MSCT examination of the chest can be performed with 25 mAs. Thus, radiation exposure was reduced to a quarter compared to the standard protocol.
本研究的目的是使用剂量模拟程序优化高分辨率胸部MSCT协议，以评估有症状的疑似肺炎免疫抑制患者。
使用MSCT（西门子，德国埃尔朗根），对30例疑似肺炎的免疫抑制患者进行胸部低剂量HRCT检查（120 kV，100等效毫安秒，准直为4×1毫米）。使用剂量模拟程序在四个不同剂量水平（70、50、35和25毫安秒）重建原始数据。对于每个毫安秒乘积的剂量模拟，将相应的噪声水平添加到数据中。在肺窗中以1毫米和5毫米的层厚生成图像。然后由两名放射科医生独立评估图像，并按1至3分进行评分：1 = 无肺炎，2 = 不明确，3 = 肺炎。进行受试者操作曲线（ROC）分析以计算曲线下面积（AUC）。计算实际剂量（以毫希沃特为单位）。评估敏感性和特异性。
30例患者中，7例胸部检查结果正常，23例患有肺炎。每个剂量和层厚的ROC曲线下面积（AUC）均为1.0。在所有剂量水平均正确检测到浸润影。所有剂量水平和层厚的敏感性均为100%。在35毫安秒和1毫米层厚时有1例假阳性结果。在此剂量水平下，特异性降至93%。降至25毫安秒对肺炎的检测没有影响。因此，胸部MSCT检查可以使用25毫安秒进行，而不会漏诊，有效剂量为男性1.15毫希沃特、女性1.5毫希沃特，容积CT剂量指数（CTDIvol）为2.5毫戈瑞。
对于评估免疫功能低下患者的肺炎，胸部MSCT检查可以使用25毫安秒进行。因此，与标准协议相比，辐射暴露减少到了四分之一。
