64排螺旋CT颈部血管成像低电压扫描初步研究

Study of 64 slice detector carotid CT angiography with low tube voltage

目的探讨低管电压(100kV)扫描在颈部CT血管成像(CTA)的临床应用可行性。方法将55名临床需要做颈部CTA检查的患者(其中男37例,女18例,平均54岁)按随机分配原则编入A、B两组(A组27例,B组28例),分别采用管电压100及120kV,管电流均采用150mAs。比较两组的CT图像质量(包括动脉平均强化CT值(SI)、信噪比(SNR)及对比噪声比(CNR))及辐射剂量。使用SPSS 13.0统计分析软件分别对所得的各组数据进行两个独立样本非参数秩和检验,P<0.05时认为差异有统计学意义。结果 A组图像噪声(14.4HU)稍高于B组(11.5HU),且A组信噪比(SNR)略低于B组。A、B两者之间的血管强化值及对比噪声比(CNR)差异没有统计学意义(SI:303.6HU比301.7HU,P=0.873;CNR:17.8比22.0,P=0.142)。两组图像质量均能满足诊断要求,两组图像的主客观评分差异没有统计学意义。A组的容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP)及有效剂量(ED)较B组分别降低33%、38%及37%。结论 64排螺旋CT颈部血管成像采用低管电压(100kV)可降低辐射剂量的同时获得符合临床诊断要求的图像。

Objective To evaluate the clinical application of carotid CT angiography using a low tube voltage （100kV）. Methods 55 patients requiring carotid CT angiography were randomly assigned to one of the two protocol groups： protocol A（27/55, scanning with 100kV and 150mAs）; protocol B （28/55, scanning with 120kV and 150mAs）. CT image quality including the signal intensity （SI）, signal-to-noise ratio （SNR）, contrast-to-noise ratio （CNR） and the radiation doses （CTDIvol and DLP） were compared between two groups. Kruskal-Wallis test was used for statistical analysis. Results The mean image noise value with protocol A （14.4 HU） was slightly higher （P 〈 0.0001） than that with protocol B （11.5 HU）. The SNR with protocol A was slightly lower than that with protocol B. The mean SI and CNR revealed no significant difference between the two groups （SI： 303.6HU vs 301.7HU,P= 0.873; CNR： 17.8 vs 22.0,P= 0.142）. Image qualitative analysis revealed no significant difference between the two groups. Compared with protocol B, the CTDIvol, DLP and ED of protocol A reduced by 33% （14 mGy vs 22 mGy）, 38% （417mGy-cm vs 669 mGy-cm）, 37% （2.25mSv vs 3.61 mSv） respectively. Conclusion Carotid CT angiography with 100kV in 64 Multi-detector CT can reduce radiation dose and get a good image quality.