高灵敏度探测器结合迭代重建在低管电压冠状动脉CT血管成像的价值

Radiation dose reduction of coronary CT angiography at low tube voltage on an integrated circuit detector with iterative reconstruction

目的 评估应用第二代双源CT新型探测器对患者进行低管电压（80 kV）冠状动脉CTA的应用价值.方法 将103例临床怀疑或已知冠心病的患者采用简单随机分组。分别以第二代双源CT普通探测器（A组）和新型探测器（B组）进行前瞻性心电触发序列扫描,A组管电压为100 kV,对原始数据进行滤波反投影（FBP）重建,B组管电压为80 kV,对原始数据进行FBP（B1组）和迭代（B2组）重建。各组CT图像的辐射剂量[CT剂量容积指数（CTDIvol）和有效剂量（ED）]以及背景噪声绝对值、主动脉根部CT值、图像信噪比（SNR）、冠状动脉近段的对比噪声比（CNR）进行系统测量.由2名放射科医师采用双盲法对每例患者冠状动脉的图像质量进行4分法评估.应用独立样本t检验比较2组患者辐射剂量（CTDIvol和ED）。应用ANOVA单因素方差分析比较A、B1和B2组主动脉根部CT值、图像噪声、SNR和冠状动脉近段CNR。应用卡方检验比较3组冠状动脉平均分可评价节段数百分比。用Kappa分析评价不同观察者冠状动脉图像质量评分的一致性。结果A组52例、B组51例患者,B组CTDIvol和ED显著低于A组,2组CTDIvol分别为（8.93 ＆#177;2.55）和（13.87 ＆#177;4.62） mGy（t =6.71,P＜0.01）,ED分别为（1.77±0.51）和（2.65±0.89）mSv（t =6.09,P＜0.01）.B1组图像噪声显著高于A组和B2组（A、B1和B2组分别为：30.52＆#177;4.45、41.17＆#177;7.68和30.91 ＆#177;6.04；F=48.75,P＜0.01）.B2组图像SNR（A、B1和B2组分别为：17.50±3.40、17.13±4.51和22.85±5.79,F=24.12）及冠状动脉近段CNR[A、B1和B2组分别为：（左主干）23.35±6.20、27.78±6.90、38.49±12.48,F=38.70；（右冠状动脉）23.61±6.18、28.83±6.54、39.81±11.65,F=48.77]显著高于A和B1组（P值均＜0.01）。图像质量评分：A组（1.29±0.23）分,B1组（1.34±0.29）分,B2组（1.33±0.31）分；3组可评价血管段的百分比[96.9％ （813/839）、96.2％（789/820）、96.5％ （791/820）],差异无统计学意义（X^2=1.81,P ＞0.05）。结论 在装备新型整合回路探测器的第二代双源CT上应用80 kV低管电压结合迭代重建进行冠状动脉CTA检查可以显著降低放射剂量,并获得可供临床评价的图像质量。

Objective To investigate the value of low tube voltage （80 kV） for coronary computed tomography angiography （CCTA） in patients with normal body mass index （BMI） on 128-slice dual-source CT with novel high sensitive integrated circuit （IC） detector.Methods One hundred and three consecutive patients were scanned using prospectively ECG-triggered sequential CCTA protocol.All patients were randomly divided into group A and B.Group A was examined on a conventional 128-slice dual-source CT,while group B on a 128-slice dual-source CT with high sensitive integrated circuit detector.The tube voltage of group A was 100 kV and raw data was reconstructed with filtered back projection （FBP）,while tube voltage of group B was 80 kV and raw data was reconstructed with both FBP （Subgroup B1） and sonogramaffirmed iterative reconstruction （SAFIRE） （Subgroup B2）.The differences in background noise,signal-tonoise ratio （SNR）,contrast-to-noise ratio （CNR）,CT dose index volume （CTDIvol）,effective dose （ED）,and image quality between the groups were compared by using t test,ANOVA and x2 test.Results There were no significant differences in age,BMI or heart rate between the two groups （Group A,n =52 vs.Group B,n =51）.Radiation exposure （CTDIvol and ED） of group B was significantly lower than that of group A [（8.93 ±2.55） vs.（13.87±4.62） mGy and （1.77 ±0.51）vs.（2.65 ±0.89） mSv,t =6.71,6.09,all P 〈 0.01].SNR and CNR of proximal coronary arteries in group B2 were significantly higher than group A and B1,and there was no significant difference between the latter two.In group A,mean score of total 839 coronary artery segments was 1.29± 0.23,and the number of evaluable segments was 813 （96.9%）.In group B1,mean score of total 820 coronary artery segments was 1.34 ± 0.29,and the number of evaluable segments was 789 （96.2%）.In group B2,mean score of total 820 coronary artery segments was 1.33 ± 0.31,and the number of was 791 （96.5%）.There were no significant differences in both mean score and percentage of evaluable segments between three groups （X^2 =1.81,P 〉 0.05）.Conclusion Using 80 kV tube voltage on 128-slice dual-source CT equipped with novel integrated circuit detector and combining iterative reconstruction is feasible in patients with normal BMI,with the benefits of significantly reduced radiation dose and adequate image quality.