The Clinical Value Of Prospectively Electrocardiographically-Gated Transverse Dsct In The Dysplasia Of The Pediatric Pulmonary Artery

BACKGROUND:Pulmonary artery dysplasia which results from anomalies of original embryonic arcade is not a rare disease. In all sorts of congenital heart disease deformity, solitary or accompanied pulmonary artery malformations occur more frequently, and the ratio of complex congenital heart disease accompanied with pulmonary artety dysplasia is higher. Evaluating the pulmonary artery development conditions accurately enables to determine the operation time, and is helpful for postoperative rehabilitation and treatment of other complicated respiratory disease, even has an effect on the decision of surgery and the way of surgery. Transthoracic echocardiography (TTE) remains a primary imaging examination in patients with suspected CHD, and is superior in displaying intracardiac deformity and valve lesions, sometimes eliminating the need for cardiac catheterization. However, because of a small field of view,and interference of air and bone, it is difficult to demonstrate extracardiac vascular structures in their entirety. Ultrasound examination and pulmonary artery measurement which mostly depends on the individual experience is restricted. It is difficult to acquire accurate measurement values and more effective diagnosis of the pulmonary artery branches outside heart chamber.Cardioangiography(CAG) is an invasive modality which yields important hemodynamic data and defines anatomy clearly in vessels which are accessible to catheterization. However, CAG often gives only indirect information regarding venous connections and arterial anatomy distal to high-grade stenosis or atresia. It also produces high doses of ionizing radiation and is limited by the inherent risk of iodinated contrast material. Electron beam CT has high time resolution, but it failed to be widely used because the check cost is high. MRI takes a longer time and generates much noise in the examination, and it fails to obtain good imaging. A non-invasive method which can be more intuitive, accurate and credible for pulmonary arterial measurement in clinic setting is required. What's more, it will help to maste the surgical indications. With the advantages of higher scanning speed, larger scanning range, higher temporal resolution and spatial resolution and the noninvasive examination, MDCT (multi-slice, MSCT) has a wide perspective.However, how to reduce effective radiation dose is still a problem.The dual-source CT (DSCT) scanner is characterized by two x-ray tubes and two corresponding detectors mounted onto the rotating gantry with an angular offset of 90°. Its single sector imaging temporal resolution reached 83ms, so it reduced the artifact caused by breathing movement and obtained high quality image in the condition of high rate.Multiplanar reconstruction (MPR), maximum indensity projection (MIP) and volume rendering (VR) three-dimensionally represent intra and extra cardiac vascular structures. Such reconstruction methods have been initially used in congenital heart disease. Currently Retrospectively ECG-gated DSCT angiocardiography has been widely used, however, the use of a low pitch and overlapping spiral CT acquisition results in the relatively high radiation dose as a retrospective ECG-gated examination. Although the combined use of dose-saving methods including a body-size-adaptive CT protocol, low tube voltage and tube current modulation can reduce the CT dose to 3.6 mSv for the patients with CHD, high radiation is still the major inherent limitation for retrospective ECG-gated CT. Prospective ECG-triggering technique transverse scan is able to significantly reduce radiation dose, and has been successfully applied in adult coronary artery examnation, as well as the pediatric congenital heart disease examination which has been reported.OBJECTIVE:To explore the clinical value of low-dose prospective ECG-triggering dual-source CT angiography in the evaluation of the pediatric dysplastic pulmonary arteries.METHODS:Forty-three patients with suspected dysplastic pulmonary arteries underwent both prospectiveECG-gated DSCT angiography and Transthoracic echocardiography(TTE). All children (average age:18 months;male 23 cases, female 20 cases; the average weight 13kg). Real-time electrocardiogram (ECG- Pulsing adaptive dose control techniques) was performed. The tube voltage and tube current were reduced to achieve low effective radiation dosage. Body weight-based adjustments of tube voltage and tube current were performed:< 5kg of children,80kV and 40～59mAs; 5-10kg of children,80 kV and 60～79mAs;> 10kg of children,80 kV and 80～120mAs. Using the electric switch control technology, prospective heart date are collected between 40% R-R period.Other scanning parameters:alignment 2×32×0.6 mm, reconstruction thick layer of 0.75 mm, frame whirl time 0.33s. The details and statistics of the radiation dose and scanning parameters were recorded. All images were transferred to an external workstation Leonardo. Multiplanar reconstruction (MPR), maximum density projection (MIP) and volume rendering (VR) were performed to demonstrate cardiac abnormalities. Two radiologists with 5 years experience in the field of cardiovascular imaging diagnosis assessed the overall image quality respectively, discussed of the inconsistency and reached the consensus. The imaging diagnosis was compared with surgery and/or CAG results. Forty-three cases all underwent DSCT and TTE, thirteen patients underwent cardioangiography (CAG) simultaneously. Surgical confirmation was available in thirty-seven patients. Surgical and CAG findings were used as the reference standard and compared to the DSCT results. Descriptive statistics was used to compare efficacy.RESULTS:There were 48 deformities in the final accurate diagnoses of pulmonary artery dysplasia in the 43 patients with preoperative DSCT cardiovascular angiography, with pulmonary artery dilated(n=13), pulmonary stenosis(n=13), pulmonary atresia (n=6), pulmonary part absence (n=6), pulmonary anomalous origin or abnormal traffic(n=9), pulmonary arterial branch development variation (n=l). The main pulmonary artery branch after the forking distal widely stricture was missing. The diagnostic accuracy for DSCT is 98.0%, for TTE is 73.5%.There are statistical difference between them (χ2= 31.24, P<0.05). Preoperative DSCT angiography and image reconstruction of all 43 cases are satisfactory. Average score of subjective image quality is 4.2±0.8.The average effective scan dosage is about 0.38±0.08 mSv.CONCLUSION:The DSCT prospectively ECG-gated transverse vascular imaging has important clinical application value in the evaluation of the pediatric pulmonary artery dysplasia, with an obviously higher diagnostic accuracy than TTE.The DSCT prospectively ECG-gated transverse is an effective way to reduce radiation dosage and is the preferred recommendation for pediatric pulmonary artery dysplasia for preoperative diagnosis.