128层双源CT前瞻性心电门控序列扫描与大螺距扫描在小儿先天性心脏病诊断准确率、图像质量及辐射剂量的对比研究

Accuracy, image quality and radiation dose comparison of prospective ECG-gated sequential and high-pitch acquisition on 128-slice dual-source CT angiography in infants and children with congenital heart disease

目的：比较128层双源CT（DSCT）前瞻性心电门控序列扫描与大螺距扫描对于小儿先天性心脏病的诊断准确率、图像质量和辐射剂量。方法前瞻性纳入2011年10月至2013年2月先天性心脏病患儿92例，采用随机数字表法分为两组。46例行DSCT前瞻性心电门控序列扫描（序列扫描组），46例行DSCT前瞻性心电门控大螺距扫描（大螺距扫描组）。以手术/DSA结果作为参考标准，计算序列扫描组及大螺距扫描组对心内结构、心外大血管、冠状动脉异常的诊断准确率和敏感度，组间比较采用Fisher精确检验。以5分法评价心内结构、心外大血管和冠状动脉近中段的图像质量。Kappa检验评价2名医师对图像质量评分的一致性。Mann-Whitney U秩和检验比较两组图像质量评分。Student＇s t检验或Mann-Whitney U秩和检验比较两组患儿的年龄、体重、心率、升主动脉根部及主肺动脉的CT值、噪声、信噪比及辐射剂量。结果92例患儿均成功完成DSCT前门控序列扫描及大螺距扫描。大螺距扫描组和序列扫描组对心内结构异常诊断准确率分别为95.65%（88/92）、99.28%（274/276），差异有统计学意义（P〈0.05）；诊断灵敏度差异无统计学意义（P〉0.05）。两组对心外大血管异常诊断的准确率和敏感度差异均无统计学意义（P〉0.05）。两组对冠状动脉异常诊断准确率差异无统计学意义（P〉0.05）；两组对冠状动脉异常诊断灵敏度分别为50.00%（3/6）、100.00%（11/11），差异有统计学意义（P〈0.05）。2名医师对心内结构、心外大血管和冠状动脉近中段图像质量评分的一致性优（Kappa=0.81、0.85、0.85，P〈0.05）。大螺距扫描组和序列扫描组在大血管的图像质量评分中位数均为5.00分，差异无统计学意义（U=981.000，P〉0.05）。大螺距扫描组在心内结构和冠状动脉近中段的图像质量评分中位数分别为4.00、3.00分，序列扫描组对两者的图像质量评分中位数分别为5.00、4.00分，序列扫描组对心内结构（U=594.500，P〈0.05）和冠状动脉近中段（U=397.500，P〈0.05）的显示优于大螺距扫描组。两组升主动脉根部及主肺动脉的CT值、噪声及信噪比差异无统计学意义。大螺距扫描组和序列扫描组的平均有效辐射剂量分别为（0.27±0.11）、（0.39±0.17）mSv，差异有统计学意义（t=4.316，P〈0.05）。结论128层DSCT前瞻性心电门控序列扫描和大螺距扫描均能为小儿先天性心脏病的诊断提供诊断准确率较高的图像。与序列扫描相比，大螺距扫描虽然受心率的影响图像质量有所下降，但辐射剂量显著降低。

Objective To compare the accuracy, image quality and radiation dose between prospective ECG-gated sequential and high-pitch acquisition on 128-slice dual-source CT （DSCT） angiography in infants and children with congenital heart disease （CHD）. Methods Ninety-two children with CHD from October 2011 to February 2013 were prospectively enrolled and assigned into two groups according to random number table. Forty-six patients underwent DSCT angiography with sequential mode, and the other 46 patients were examined with high-pitch mode. With surgical and/or DSA results as the standard, the diagnostic accuracy and sensitivity of the two groups for the intracardiac structures, extracadiac and coronary artery anomalies were evaluated, and the comparison was analyzed by Fisher exact test. A 5-grade scoring system was used to interpret the image quality of intracardiac structures, great vessels and the proximal and middle segments of coronary arteries. Interobserver agreement on grades of image quality was assessed by Kappa statistics. The image quality scores were compared using the Mann-Whitney U test. The Student t test or the Mann-Whitney U test was used to analyze the differences between the two groups regarding to patients＇ age, weight , heat rate, CT attenuation, image noise and SNR in the ascending aorta and the pulmonary trunk as well as radiation dose. Results All 92 patients successfully underwent DSCT angiography. The diagnostic accuracies of intracardiac anomalies by high-pitch group and sequential group were 95.65%（88/92） and 99.28%（274/276）, showed significant difference between the two groups （P〈0.05）, but no significant difference in the sensitivity of intracardiac anomalies （P〉0.05） .There was no significant difference in the diagnostic accuracy and sensitivity of extracadiac anomalies between the two groups （P〉0.05）. The diagnostic accuracies of coronary artery anomalies by high-pitch group and sequential group were 93.48%（43/46） and 100.00%（46/46）, showed no significant difference between the two groups （P〉0.05）, but there was significant difference in the sensitivity of coronary artery anomalies （50.00%（3/6） , 100.00% （11/11）） （P〈0.05）. There was excellent agreement for image quality scoring of the intracardiac structures, great vessels and the proximal and middle coronary arteries between the two observers （Kappa=0.81, 0.85, 0.85, P〈0.05）. The median image quality scores of extracardiac great vessels were both 5.00 in high-pitch group and sequential group, and there was no significant difference between the two groups （U=981.000, P〉0.05）. The median image quality scores of intracardiac structures and proximal and middle segments of coronary arteries respectively by high-pitch group were 4.00 and 3.00, and 5.00 and 4.00 respectively by sequential group. The image quality of intracardiac structures （U=594.500, P〈0.05） and proximal and middle segments of coronary arteries （U=397.500, P〈0.05） was significantly better in the sequential group than that in the high-pitch group. There was no significant difference between the two groups in CT attenuation, noise and SNR of the ascending aorta and pulmonary trunk. The mean effective doses of the high-pitch group and the sequential group were（0.27±0.11）and（0.39±0.17）mSv, and showed significant difference between the two groups （t=4.316, P〈0.05）. Conclusions Both sequential and high-pitch mode of 128-slice DSCT angiography provide high accuracy for the assessment of CHD in infants and children, while the high-pitch mode, though with some image quality declined, shows further significantly lower radiation dose.