双源CT低剂量扫描在胸部普通检查中的应用价值

Application of Dual-source Low-dose Computed Tomography in Common Chest Inspection

目的探讨双源CT低剂量扫描技术在胸部普通检查中的应用价值。方法将2011年8月-2012年12月收治的875例患者依次分为7组,分别采用常规管电流量110 mAs和低管电流量105、100、95、90、85、80 mAs测量,计算并评估7组患者纵隔窗图像的胸骨前空气CT值标准差(SD空气)、肺动脉分叉平面肺动脉信噪比、降主动脉信噪比、肺动脉-竖脊肌对比噪声比、降主动脉-竖脊肌对比噪声比;纵隔窗图像和肺窗图像主观质量评分以及射线剂量指标:CT剂量指数(CTDI)、剂量长度乘积(DLP)、有效剂量(ED)。结果 7组患者纵隔窗图像肺动脉信噪比、降主动脉信噪比、图像主观质量评分和射线剂量CTDI、DLP、ED之间差异均有统计学意义(P<0.05);肺动脉-竖脊肌对比噪声比、降主动脉-竖脊肌对比噪声比之间差异无统计学意义(P>0.05);其中第7组图像信噪比、射线剂量和主观质量评分均为最低,部分图像肩背部出现横条状伪影,影响肺尖部病变的显示,难以提供足够的诊断信息。结论胸部普通CT检查,通过阶段性降低管电流量使诊断医生逐渐适应低剂量图像质量,从而普及现有设备的低剂量扫描的方法是可行的。双源CT采用85 mAs的参考管电流量,既能获得满足临床诊断的合格图像,又能明显降低患者群体接受的辐射剂量。

Objective To discuss the application of dual-source low-dose computed tomography in common chest inspection. Methods A total of 875 consecutive patients treated in our hospital betwwen Auguest 2011 and December 2012 were orderly divided into seven groups. From group one to group seven, the tube current of each group was ordinal 110, 105, 100, 95, 90, 85, and 80 mAs. The standard deviation of mediastinal window image before sternum air, signal to noise ratio of pulmonary artery branch plane pulmonary artery, signal to noise ratio of aorta descendens, noise ratio contrast between pulmonary artery and erector spinae, noise ratio contrast between aorta descendens and erector spinae, score of mediastinal window image and pulmonary window image subjective diagnosis and the indexes of radiation dose, including CT dose index （CTDI）, dose length product （DLP）, and effective dose （ED） were measured, calculated and assessed respectively on CT images of mediastinal window and lung window in all the seven groups. Results The standard deviation of mediastinal window images, signal to noise ratio of pulmonary artery branch plane pulmonary artery, signal to noise ratio of aorta descendens, score of subjective diagnosis and the indexes of radiation dose, including CTDI, DLP, and ED of CT images were significantly different from each other among the seven groups （P 〈 0.05）, while noise ratio contrast between pulmonary artery and erector spinae and between aorta descendens and erector spinae were not statistically significant （P 〉 0.05）. The signal to noise ratio, radiation dose and score of subjective diagnosis of group seven were the lowest of all groups, and transverse stripe artifacts appeared on the humeral back in part of the images, which disturbed apex of lung lesions and made it difficult to provide enough diagnostic information. Conclusions The method of decreasing tube current gradually in common chest CT inspection can ensure that radiologists are able to adapt to low-dose image bit by bit, and this method can be popularized to all kinds of CT facilities we own currently. The images with 85 mAs as tube current in common chest inspection with dual-source CT can fulfill the need of diagnosis, and the radiation dose of patients is apparently lower than the conventional scan.