| Coronary artery disease is a kind of disease that jeopardizes human being's health, especially the attack rate of coronary atherosclerotic heart disease and coronary variation and malformation is increasing year by year in recent years, so diagnosing this kind of disease in earlier period has important clinical meaning. At present, the methods to checking this kind of disease have multi-slice spiral CT (MSCT), magnetic resonance imaging (MRI), electro-beam CT (EBCT), coronary angiography (CAG), et al. Diagnosing this kind of disease takes CAG as standard, but CAG can only show the degree and scope of lumens stenosis and to diagnose coronary variation and malformation is limited as well. EBCT has one image in a scan period. Because of physiological diversity of heart and anisorhythmia, signal-to-noise ratio of image is low and spatial resolution of image in Z axle is not high. The factors above are limited the application of EBCT. MRI scan time is very long, the patients of metallo- frame and pacemaker can't use MRI scan. Furthermore the time and spatial resolution of present MRI equipments can't satisfy diagnosis of coronary artery disease completely due to the bad image quality.The low contrast degree and movement constructed defect are also limited the application of MRI. The main dominance of MSCT is as follow, (1) Spatial resolution of image is high and sensitivity and specificity are also high; (2) The image can revolve and watch at any angle, we can find coronary variation and malformation. (3)The image can show calcification in vessel wall and the relation to lumens. (4)We can measure diameter and area at narrow part directly and length. (5) Scan time is short and the expense is little. (6) No trauma and safety. MSCT is gradually becoming the main screen and diagnosis method. But diagnosis need high quality images. So this study mainly approaches the application of multi- restitution method of MSCT and the factors of influencing image quality. We use 16 layer spiral CT to analysis 42 patients who have coronary disease or are suspected coronary disease. (including 2 patients who are implanted frame and 1 patient who has suffered coronary artery bypass); and also 10 men of medical examination. Among the total, 34 male, 18 female, age range from 35 to 73 years, average 54 years. When heart rate is infra-65, we start scan. The scan numerical data was reconstructed such as volume rendering technique (VRT), multi-planar reformation (MPR), curved planar reformat (CPR), maximum intensity projection (MIP), CT virtual endoscopy (CTVE).Result: among 42 patients, 2 cases who have frame: 1 case has no abnormality, 1 case occur stenosis close to frame. 1 case who has 3 bypass artery occur 1 artery stenosis. Among the rest, there are 23 cases abnormality, and 13 cases no stenosis and abnormality; 3 cases can't diagnose because of bad images. Among 10 men of medical examination, 2 cases have stenosis, 2 cases have parietal coronary artery, 6 cases have no stenosis and abnormality. We divided all into 3 groups according to the heart rate in scan (1) <60 times/ min (2)60-70 times/ min (3)>70 times/ min; 2 groups according to the heart rate range in scan (1) <10 times (2)≥10 times . On the original picture and the reconstruction picture, the image quality of the blood vessel is divided into 3 classes to analyze respectively the influence of the heart rate and the heart rate range. The speed of heart rate is the most important to the image. The image quality of heart rate≤60 times/ min surpasses 61-70 times/ min, both are better than>70 times/ min. The heart rate fluctuation is not neglected, either. The fluctuation range <10 times/ min obviously surpass≥10 times/ min. We also analyze the influence of breathholding in scan, bad breathholding influence the main artery and branch ones which occur constructed defect such as breaking and shifting. The volume dose and injecting velocity of constrast medium and delay time are also very important. Our study analyze that the amount of constrast medium is 100ml, injecting velocity is 4-4.5ml/ml, the delay time is generally 18-28min according to prepared small amount experiment to calculate the result. The images are best according to the conditions all above. Various kinds of reconstruction technique, VRT can help localization; CPR and CTVE can judge narrow degree more accurately; MIP is the most accurately to evaluate calcification of vessel wall. So we should select suitable reconstruction technique due to different cases combining axial view and have a comprehensive analyze.The clinical application worth of MSCT: (1) MSCT can display anatomy structure of coronary artery; can be used for discover various coronary variation and malformation and can clearly show the appearance and position, the relation to the other blood vessels and each cardiac atrium or ventricle. (2) MSCT can show location and degree of stenosis and can show the information of vessel wall and out-of wall; we can directly watch and measure diameter of coronary utilizing various reconstruction techniques and judge degree, character and morphous of stenosis. (3) MSCTCA has high sensitivity to different degree calcification in coronary, we can analyze atheromatous plaque according to different CT value and acquire plaque classification according to plaque density. (4) MSCTCA can evaluate the coronary artery after bypass and implanting frame. MSCTCA has special superiority to the artery stenosis above and has advantage of no trauma and observing by various visual angle. (5) MSCTCA can value other coronary diseases. It can discover other coronary diseases such as coronary aneurysm. In addition, one MSCTCA scan, we can gain many heart images, so we can value cardiac function and myocardium thickness, as well as find pathological changes of chambers heart and pneumoangiogram.Along with improving of time and space resolution, MSCT will be applied more and more extensively in coronary diseases and the foreground more and more widely. The detector of more layers and smaller volume and quicker velocity reduce movement constructed defect obviously and lower the volume of constrast medium. The smaller blood vessel can show which can improve image quality of coronary and quantitative analysis of coronary arteriosclerosis is more and more accurate. MSCT can't completely replace CAG in a short time, but it's superiority of function can undoubtedly offer more information to clinic diagnosis in coronary diseases and provide more scientific reference to clinic treatment. We are sure that MSCT can invariably overcome the technical difficulty and replace CAG in diagnosis in the near future. |
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