الفهرس 
Anatomy of the Coronary ArteriesOnly 14 pages are availabe for public view
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Abstract
In recent decades, multi-slice coronary CT angiography has become one of the hot spots in cardiovascular imaging technology. This method has been applied for evaluating coronary artery stenosis, and was proposed as a potential alternative procedure for invasive coronary angiography. Coronary CT angiography is unique in its ability to noninvasively diagnose coronary artery disease and to accurately detect significant stenosis plus it is a quick, relatively simple and quick procedure that can be performed within 10 to 20 minutes. The degree of coronary luminal narrowing is commonly used to guide diagnosis and therapeutic interventions in clinical cardiology. However, coronary artery stenosis detection has some drawbacks in diagnosis of CAD; acute coronary thrombosis has been identified as the main cause of myocardial infarction and increased lipid content and positive remodeling are typical pathology features of vulnerable atherosclerotic plaques. In addition, Coronary calcification continues to be limit diagnostic accuracy and limits positive predictive value of coronary CT angiography. Recently, modern CT scanners allow not only the visualization of the coronary lumen as invasive coronary angiography, but also the vessel wall, granting non-invasive analysis of atherosclerosis itself. The excellent image quality of recent CT scanner enables quantification and characterization of coronary plaques which open new ways in cardiovascular risk stratification. The aim of the study was to characterize atherosclerotic plaques as regard plaque burden and composition to assess its added value to avoid acute coronary syndrome later on. We enrolled 60 patients in this study: 38 were males and 22 were females with age ranged from 26 to 70 years with a mean of 53.7 years. We obtained heterogonous sample in which 24 patients were with unstable coronary artery disease and 36 patients with stable coronary artery disease. The enrolled patients with stable coronary artery disease met these criteria; Asymptomatic patient with high risk of coronary artery disease as patients with positive family history of coronary artery disease, patients with atypical chest pain and class I and II angial pain were included as candidates for stable coronary artery disease. The enrolled patients with unstable coronary artery disease met these criteria; class III and IV angina as well as patients who had experienced major cardiac event that relieved medically were included as candidates for unstable patient group. All included patients in this study were evaluated by: • History taking: personal history, risk factors (family history, hypertension, D.M and dyslipidemia). • Clinical examination: as measuring blood pressure and heart rate before and after CT examination. • Echocardiography: for checking ejection fraction and segmental wall motion abnormalities. • Renal function test to ensure that the patient fit for contrast material injection. • Lastly, 320-row multi-detector coronary CT angiography. The objective of the coronary artery evaluation is to convey clinically meaningful, consistent information about the presence, location, characterization and degree of atherosclerosis as well as to report on any coronary stenoses that are present. Coronary artery segments were evaluated using a Society of Cardiovascular Computed Tomography model. Coronary plaques were defined as structure of at least 1mm2 area within and/or adjacent to artery lumen, clearly distinguishable from the vessel lumen and surrounded by pericardial tissue. Coronary atherosclerotic plaques were stratified as regard degree of stenosis as minimal < 10%, Mild ≤ 49%, Moderate 50-69%, severe ≥70%, subtotal > 90% and total occlusion per coronary segment (AHA-modified- 17 segment classification). Quantitative CTA lesion analysis was performed on all plaques > 25% by automated soft ware that automatically segments vessel margins, separate different plaque components by using attenuation thresholds (-30-60 for lipid plaque, 61-149 for fibrous plaque and 150-1300 for calcium) and provide color map of plaque compositions. All plaques > 25 % stenoses were analyzed for morphologic features, Parameters analyzed include: • Plaque burden of the whole plaque and at area of maximal narrowing = (Lesion plaque area- lesion lumen area /lesion plaque area). • Low attenuation plaque (LAP): CT density was recorded with quantitative CTA analysis and area of ROI (LAP is defined as hypoattenuation with CT density < 150 HU). • Napkin ring sign (NRS): was defined as an outer high density rim with inner hypodense area not adjacent to calcification and present on minimum of two adjacent axial 1mm slices. • Remodeling index (R.I) was calculated as the ratio of maximal cross sectional vessel diameter, including the plaque and the lumen and its closest proximal (or distal in ostial lesion) normal reference vessel diameter. • Spotty calcification was defined as calcification < 3mm. • Features of plaque disruption included ulceration defined as disruption of the interface between plaque and the lumen with contrast penetration directly from the lumen into the plaque but contiguous with the lumen.