双源CT冠脉成像安全辐射剂量与图像质量研究

摘要

目的:利用回顾性研究分析西门子第二代双源CT的冠状动脉图像,比较三种冠状动脉CT血管造影扫描方法的图像质量及辐射剂量.方法:分析407例利用西门子第二代双源 CT 回顾性螺旋扫描(RES-SPIRAL)、前瞻性序列扫描(SEQ)、前瞻性大螺距螺旋扫描方法(Flash)行CCTA检查患者的影像资料.患者的有效辐射剂量由剂量长度乘积×0.014转化系数获得.图像质量主观评价方法采用美国心脏协会冠脉15段分法,分别进行5等级评分;客观方法采用将主动脉根部的CT值的标准差设为图像噪声,然后分别评价左主干近端及右冠状动脉近端的对比噪声比、信噪比.分别采用Kruskal-Wallis检验或单样本方差分析比较3种扫描方法图像质量及辐射剂量的差异,利用Logistic回归分析扫描方法、管电压、管电流对辐射剂量的影响.结果:3种扫描方法客观图像质量的评价中,RES-SPIRAL扫描方法的图像质量最好,且三者间的比较差异有统计学意义(P<0.001).3种扫描方法主观图像质量评分之间比较差异无统计学意义.在辐射剂量的比较中发现,SEQ [DLP=(64.87 ± 16.66) mGy,ED=(0.91 ± 0.23) smv]、Flash[DLP=(64.87 ± 16.66) mGy,ED=(0.91 ± 0.23) smv]扫描方法的辐射剂量均较RES-SPIRAL扫描方法明显降低[DLP=(951.78 ± 197.92) mGy,ED=(13.33 ± 2.77) smv],差异具有统计学意义(P<0.001),其中Flash扫描方法剂量最低.Logistic回归分析辐射剂量控制在DLP<364 mGy·cm的较强预测因子为管电压(OR=1.336)及扫描方法(OR=0.006).结论:CCTA检查的辐射安全问题意义重大,第二代双源CT的Flash扫描方法扫描速度快,并可以明显降低患者的辐射剂量,同时提供较好的图像质量,为CCTA检查安全推荐剂量修订做出了一定的贡献.%Objective:To retrospectively analyze the diagnostic image quality and estimated radiation dose of the three coronary computed tomographic angiography (CCTA) acquisition protocols in a recently introduced second generation dual-source computed tomography.Methods:A total of 407 subjects underwent dual-source CCTA by using high-pitch spiral,sequential and retrospective spi-ral protocols.Effective radiation dose,expressed was calculated as the product of the dose-length product times a conversion factor of 0.014.The scores of imaging quality was evaluated on a per-segment basis,with a five-point scale.Quantitative image quality parame-ters,including image noise,attenuation,CNR and SNR,the CT density in a region of interest placed in the aortic root,LM and RCA were measured.Kruskal-Wallis tast or ANOVA were used to evaluate CNR,SNR,CTDIvol,DLP,ED were compared among the three protocols.Logistic regression analysis was performed and odds ratios (ORs) were computed to evaluate the effects of scan protocols, tube voltage and tube current on CT dose.Results:Sequence Scan[DLP=(64.87 ± 16.66),ED=(0.91 ± 0.23) mSv] and Flash-spiral method[DLP=(64.87 ± 16.66),ED=(0.91 ± 0.23) mSv]had different degree of reduced in the value of radiation dose,SD, CNR and SNR than Retrospective spiral scan method[DLP=(951.78 ± 197.92),ED=(13.33 ± 2.77) mSv].CT dose of the Flash-spiral method was significantly lowest(P<0.001) than the other two.Logistical regression analysis showed the CT dose of OR of tube voltage(OR=1.336)and scan protocol(OR=0.006)were significantly high.Conclusion:Coronary computed tomographic angiography radiation safety problem is of great significance,dual-source CCTA using Flashspiral method considerably lowers radiation exposure and maintains good image quality with fast speed.These findings may contribute to new target dose recommendations in societal guidelines.