| BACKGROUND:Congenital heart disease (CHD) with a rate of0.7%-0.8%in live births is common for children with heart diseases. It is important for patients with CHD to make accurate diagnosis and evaluation before surgery. Cardiac angiography is considered as the golden standard for the diagnosis of CHD, but it is invasive, complicated and with high radiation. Transthoracic echocardiography (TTE) is the first choice for CHD due to its noninvasiveness, no radiation and low expense. However, TTE is unable to detect the vascular deformities completely because it is confined by acoustic window, and the experience of operators has a great influence on the diagnosis. Multi-slice spiral computed tomography (MSCT) and Dual-source CT(DSCT)make good diagnosis for CHD but have a high radiation with retrospective ECG-gated technique. Although the radiation is decreased to3-6mSv by means of low tube voltage and current, it is still unacceptable for children (the rate of malignant tumors of infants is ten times higher than that of adults after the exposure of X-ray). Prospective ECG-triggering technique which has been applied to the examination of adult coronary angiography obtains diagnosable pictures and low radiation, so there will be a great clinic value if the technique is used in the examination of children with CHD.OBJECTIVE:To find whether low-dose prospective ECG-triggering DSCT angiography is suitable for the diagnosis of children with CHD.METHODS: Thirty-seven patients (mean age:0.89years, range:22days to4years and3months; male22; mean weight:7.85kg) underwent low-dose prospective ECG-triggering DSCT angiography. With the fixed triggering technique, the scan was started manually two seconds later once four chambers were filled with contrast at the same time. The tube voltage was80kV and the tube current was modulated according to the weight of the patients. The exposure window was32%～48%R-R interval with a center of40%. The scan was completed with a collimation of2x64x0.6mm, a gantry rotation time of0.33second per circle. The scan time was4.61～10.19s. Iopromide,350mg I/ml, was used as contrast medium and2ml/kg of contrast medium plus the saline flush with half contrast volume at the same rate were injected. The CT dose index volume (CTDIvol) and dose length product (DLP) were recorded in order to calculate effective dose (ED). The images of best reconstructional phase were transmitted to workplace and recombination techniques such as multi-planar reformation (MPR), maximum intensity projection (MIP) and volume rendering (VR) were applied to the analysis of images. Two experienced radiologists made diagnosis and assessed the overall image quality by a five-point scale independently. The degree of their agreement was determined by Kappa statistics. All patients underwent TTE. Surgeries were performed in29patients, and cardiac angiography (CAG) was performed in8patients. The sensitivity, specificity, positive and negative predictive values of DSCT angiography and TTE were calculated based on the surgical and/or CAG findings. The degree of correspondence between DSCT angiography and TTE was determined by Chi-square statistics, and the significance was accepted when p value was lower than0.05.RESULTS:The mean ED was (0.39±0.14) mSv with a range of0.195mSv to0.594mSv. The average subjective image quality score was4.3±0.6. All images were diagnosable. The surgical and/or CAG findings were atrial septal defect (n=14), ventricular septal defect (n=16), single ventricle (n=1), tricuspid atresia (n=2), right ventricle of outlet stenosis (n=5), double outlet of right ventricle (n=2), abnormal connection between atrium and ventricle (n=1), pulmonary valve stenosis (n=1), pulmonary atresia(n=3), pulmonary stenosis (n=8), patent ductus arteriosus (n=9), pulmonary dilation (n=8), aortic overriding (n=6), coarctation of aorta (n=7), transposition of the great arteries (n=2), aberrant right subclavicular artery (n=1), persistent left superior vena cava (n=2) and abnormal origin of coronary artery (n=3) and a total of91abnormalities and deformities. DSCT angiography missed atrial septal defect (n=2), ventricular septal defect (n=1) and abnormal connection between atrium and ventricle(n=1), and misdiagnosed atrial septal defect (n=1). TTE missed pulmonary stenosis (n=2), aberrant right subclavicular artery (n=1) and abnormal origin of coronary artery (n=3), and misdiagnosed coarctation of aorta (n=1). The accuracy of DSCT angiography and TTE was99.2%and98.9%, respectively, and there was no statistic significance (x2=0.335, P>0.05). The sensitivity, specificity, positive and negative predictive values of DSCT angiography were95.6%,99.8%,98.9%and99.3%, while those of TTE were93.4%,99.8%,98.8%and99.0%.CONCLUSION:There is a very low radiation dose accompanied with low-dose prospective ECG-triggering DSCT angiography with the precise diagnosis of CHD, so it owns much clinic value in the examination of children with CHD. |
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