الفهرس 
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Abstract
The high incidence of catastrophic cerebrovascular disease and the wide spread prevalence of surgically accessible atherosclerotic lesions in the carotid vessels in such patients have made the carotid bifurcation the most extensively studied arterial segment in the peripheral circulation. Atherosclerosis is the most common cause of carotid artery disease as accumulation of the atheromatous plaques will eventually lead to stenosis and even occlusion of the carotid vessels. Accidentally, the atherosclerotic plaques may be complicated by intraplaque subintimal hemorrhage and necrosis. In advanced cases massive calcification, fissuring and ulceration may take place. Hemorrhage in to a plaque may result from loss of endothelial integrity (early ulceration) leading to ballooning of the plaque and even rupture of the carotid vessels. This study was conducted to detect the role of non-invasive imaging modalities in the diagnosis of carotid artery diseases in ischemic cerebrovascular lesions. Non invasive imaging techniques (namely Doppler US, CTA, and MRA) are the current methods used for evaluating carotid artery diseases. These techniques were done for 25 cases referred to US from neurology and vascular surgery departments, Mansoura University Hospital. Yet, these non-invasive techniques show different degrees of specificity and sensitivity regarding: (1) the estimation of the degree of stenosis, (2) the depiction of areterial wall calcification, intimal thickening, ulcer and plaque and (3) Surgical planning and even post operative evaluation. From our study, we conclude the following:- ” CFD, as first screening technique in carotid system imaging, is an accurate and reproducible test providing not merely morphological but also functional information. Its accuracy mainly in carotid stenosis less than 50% diameter reduction. ” However if equivocal results are obtained by CFD especially in cases of highly critical stenosis, we should proceed to another imaging non invasive modalities. ” MRA is non invasive and does not exhaust much time or effort, it does not expose the patient to radiation, iodinated contrast injection, and also has the capacity to provide multiple projections of abnormal vascular anatomy with a single data acquisition. ” 2D TOF MRA is more sensitive to the slow flow in cases of nearly occluded carotid system. ” Although MRA found to be an extremely poor predictor of ulceration or the length of stenosis. And the most significant disadvantage is that it may overestimate the degree of stenosis in cases of critical stenosis >90%. ” CT angiography, as a new technique, yielded higher sensitivity, specificity and accuracy than did CCDI and MRA when assessing carotid stenosis that required surgery and correlated better with CEA. ” Calcification and ulceration are best evaluated by 3D CTA, and also the anatomical relationships between the site of stenosis and the IJV and bony structures (required for pre and post operative evaluation) is best demonstrated by CTA using the SSD reconstruction method. ” The most significant point regarding CTA of carotid system is that it is a real image that detect any residual arterial lumen, specially in highly critical stenosis. ” CTA is a speed imaging and because the intravascular data reflect volume of contrast and relatively independent of flow, belical CTA is the non invasive study of choice for extreme stenosis, tortuous vessels, and stenosis with very slow intravascular flow.