The interpretation of cardiovascular structures on cardiac CT scan studies is similar to that for echocardiography, however, it is not limited by the acoustic window or operator dependent like ultrasonography. In addition to the anatomic information, a cardiac CT scan provides hemodynamic information, including extracardiac and intra-cardiac shunts. It also enables the systematic evaluation of other thoracic structures like cardiovascular structures, the airways and the lungs by using maximum and minimum intensity projections to delineate the vascular and airway structures, respectively. Extra-cardiac great vessels can be evaluated along their length; thus augmenting the role of cardiac CT scans in children with congenital heart diseases .Inspite of the poorer temporal resolution of cardiac CTA compared to echocardiography, yet the combination of rapid acquisition time, increased anatomic coverage, high spatial resolution, multiplanar reformation and 3D capability combined with a flexible ECG synchronization have improved the image quality of cardiac CT scans and minimizing the patient risks. Multidetector computed tomography has greatly advanced the noninvasive diagnosis of these anomalies in pediatric patient, thus makes MDCT an ideal non- invasive method for evaluating pediatric patients .
Congenital heart diseases (CHDs) are considered as the most common congenital birth defects, comprising 1% of all live births . Echocardiography remains a first-line non-invasive imaging tool for establishing the diagnosis and follow-up in most patients .This method is operator dependent and limited by an acoustic window .~Traditional angiography is typically utilized as the gold standard modality for diagnosing CHD, but it is an invasive method and need general anseathsia with dose of radiation exposure .After recent developments in CT and MR technologies, cardiac catheterization is no longer necessary for diagnosis .