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The Clinical Value of DSCT in the Diagnosis of Congenital Heart Disease

Author: ChengZhaoPing
Tutor: WuLeBin；WangXiMing
School: Shandong University
Course: Medical Imaging and Nuclear Medicine
Keywords: Heart Defects, Congenital Dual-source CT Echocardiography Cardioangiography
CLC: R816.2
Type: Master's thesis
Year: 2008
Downloads: 123
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Abstract

BACKGROUND:Congenital heart disease（CHD）is a common condition with a varying incidence of 4-6 cases per 1,000 live births for complex forms.Transthoracic echocardiography（TTE） remains a first-line imaging examination in patients with suspected CHD.This test has been considered the clinical gold standard,often eliminating the need for cardiac catheterization.However,it is limited by a small field of view,a variable acoustic window,inability to penetrate air and bone,and difficulty in delineating extracardiac vascular structures in their entirety.Angiography is an invasive modality that yields important hemodynamic data while clearly defining anatomy in vessels that are accessible to catheterization.However,angiography often gives only indirect information regarding venous connections and arterial anatomy distal to high-grade stenosis or atresia.It also uses high doses of ionizing radiation and is limited by the risks inherent to iodinated contrast material.Non-invasive coronary angiography using multi-slice computed tomography（CT）has recently emerged as an clinical tool for the accurate assessment of congental heart disease（CHD）.The recently introduced 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°.Regarding cardiac imaging capabilities,the new scanner system offers a high temporal resolution of 83 ms in a mono-segment reconstruction mode. Temporal resolution is independent of the heart rate,which is a major difference from single-source CT systems that rely on multi-segment reconstruction techniques.The first feasibility studies have shown promising results with DSCT coronary angiography regarding image quality of coronary arteries,cardiac valves,and left ventricular myocardium independent of the actual heart rate of the patient.OBJECTIVE:To explore the clinical value of low-dose ECG-gated dual-source CT（DSCT） angiography in the diagnosis of congenital heart disease.METHODS:Fifty-one patients with suspected congenital heart disease underwent both ECG-gated DSCT angiography and Transthoracic echocardiography（TTE）.Twenty-four patients were imaged with cardioangiography（CAG）simultaneously.Surgical confirmation was available in thirty-two patients.Surgical and CAG findings was used the reference standard.Individual scan parameters were used:For infants younger than 1 year,tube voltage and tube current were 80kV and 50～60mAs respectively;For children aged 2～6 years,100kV and 60～70mAs;For children aged 7～12 years,120kV and 60～80mAs;For children aged 13～18 years,120kV and 80～100mAs.ECG-triggered tube current modulation and full current at 70%of the cardiac cycle for heart rates below 70 beats per minute or full current between 30%and 80%for higher and arrhythmic heart rates.The pitch was adapted to the heart rate（mean 105 beats per minute）,ranging from 0.25 to 0.59.Volume and flow rate of contrast material（Ultravist 370）were adapted to the patient’s body weight.Three-dimensional reconstruction were performed in all cases with multiplanar reformation（MPR）、maximum intensity projection（MIP）,volume rendering（VR）.The two radiologists and one pediatric cardiologist that interpreted the DSCT images and CAG,respectively,were blinded to each other’s results.Surgical and CAG findings were compared to the DSCT results.Descriptive statistics were used to compare efficacy.RESULTS:Main coronary artery branches and partial sub-branches were visualized in all patients.12 patients were showed abnormal coronary artery.1 case was showed coronary artery-right and left ventricle fistula.1 case was showed coronary artery-left and fight atrium fistula.1 case was showed entirely right-sided coronary arterial system. 1 case was showed entirely left-sided coronary arterial system.2 case was showed LCA coming from pulmonary artery trunk.2 cases were showed left anterior descending （LAD）and right coronary artery（RCA）all coming of right aortic sinus.2 cases were showed RCA and circumflex（CX）coming of right aortic sinus.1 case was showed LAD and CX coming of left aortic sinus respectively.1 case was showed all coronary artery branches circuitous and dilated.A total of 182 cardiac deformities confirmed by operations and several image methods were studied.The sensitivity,specificity,and accuracy of DSCT in detecting cardiac deformities 100%,97.25%,and 97.25%respectively.There were 63 incardiac deformities.The definit of diagonosis of DSCT and TTE were 93.65%、98.41%,respectively.DSCT was as accurate as TTE in revealing incardiac deformities（x²=1.87,P＞0.10）.There were 119 extrocardiac deformities.The definit of diagonosis of DSCT and TTE were respectively 99.16%and 67.23%.DSCT was superior to TTE in the identification of extrocardiac deformities（x²=43.40,P＜0.005）. DSCT combined with TTE could increased the definite diagonosis rate to 99.45%.Estimation of radiation dose:For infants＜1 year mean CTDI_volwas1.96±0.19mGy;For children aged 2～6 years mean CTDI_volwas5.01±0.71mGy;For children aged 7～12 years mean CTDI_volwas9.87±0.89mGy;For children aged 13～18 years mean CTDI_volwas 12.11±1.56mGy.CONCLUSION:ECG-gated DSCT angiography is superior to TTE in congenital heart disease diagnosis,especially in the diagnodsis of extrocardiac deformities.The combination of DSCT and TTE can raise the diagnosis accuracy rate of various kinds of congenital heart disease.ECG-gated DSCT angiography improves coronary visualization in babies, even when the heart rate is very high.It is essential to use radiation dose reduction tools whenever possible. ECG-dependent dose modulation and individual adaptation are complementary and have an addictive effect on dose reduction.

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