BACKGROUND One of the important causes of morbidity and mortality in paediatric population is Congenital Heart Disease (CHD). Genetic, environmental and cultural factors may lead to variability in prevalence and incidence. (1) There are many modalities for the diagnosis of CHD, in our armamentarium. Echocardiogram is the first in cases suspicious of CHD. However quite often, it is difficult to access and evaluate great arteries, pulmonary veins, coronary arteries and intracardiac anomalies in detail. In seriously ill or uncooperative patients, magnetic resonance imaging (MRI) is often of limited use. MRI examination also takes longer duration, causes claustrophobia and electronic devices such as pacemakers are a contraindication. (2) METHODS In this retrospective observational study 21 cases of clinically diagnosed Tetralogy of Fallot's (TOF) referred to Sodani Diagnostic Centre, Indore and matching our inclusion and exclusion criteria, were included in this study. Out of 21 subjects, 9 were female and 12 were male. Youngest was 9 months old and eldest was 30 years old. Most of the study subjects were sent investigation of the morphology of heart and great vessels using cardiac CT, as echocardiography was not enough. All studies were performed on 128 Slice GE Optima after taking consent. RESULTS In our study, a 128 slice multidetector CT scanner GE Optima was used, to scan 21 patients with TOF. Defect in ventricular septum (VSD) was noted in all cases (n =21). Overriding of aorta was noted in nineteen patients (90%). Right ventricle was mildly hypertrophied (RVH) in 10 patients (47%). 8 patients (33%) were showing major aorto-pulmonary collateral circulation (collateral diameters ranged from 1 to 3.5 mm) and narrowing of pulmonic infundibulum was seen in 7 patients (28%), aortic arch was right sided in 5 cases (23%). Complex pulmonary artery morphology was seen in most of the patients. Pulmonary trunk and bilateral pulmonary arteries were significantly narrowed in 3 cases (14%). Stenosis of main trunk and left pulmonary artery were noted in 2 cases (9%). Right pulmonary artery and main trunk narrowing was seen in 4% (n=1). CONCLUSIONS Important additional information is obtained by using technically advanced Multidetector CT. Newer advances have significantly increased the speed of CT machines, so we can complete the procedure of pulmonary CTA with ease of peripheral venous access and markedly reduced sedation time. No correlation was found between size of pulmonary trunk and collaterals, which suggests that every patient has different chance of detecting collaterals. However as age increases, chances of getting collaterals also increases.

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