Sharif Digital Repository

Coronary artery diseaseaffects millions of persons and isone of the leading causes of morbidity and mortality worldwide. Invasive techniques such as coronary artery bypassgrafting are used to alleviate the lesion of arterial occlusion.Unfortunately, restenosis or occlusion of the graftedconduit occurs over a time frame of months to years with a gradual reduction in patency, especially in vein grafts. Theevents leading to intimal hyperplasia (IH) formation involve numerous cellular and molecular components. Variouscellular elements of the vessel wall are involved as are leucocyte–endothelial interactions that trigger the coagulationcascade leading to localized thrombus formation. Subsequent... 

Cardio Vascular Diseases (CVD) is currently the most important cause of mortality in the world. Coronary artery disease (CAD-with 3 major epicardial vessels) is one of the significant CVD. Coronary angiography remains the gold standard for identifying the presence and absence of stenosis due to CAD. It is performed by inserting a catheter into the coronary artery, directly injecting radiopaque contrast material there and recording radiographic images in different view of arteries. Images of this invasive way show severity and area of stenosis.
A sign of CAD is endothelial dysfunction (inner artery layer) in peripheral arteries like the brachial artery. Due to a significant correlation... 

Cardiovascular diseases are the leading cause of death all over the world, even more common than cancers. The first reason of mortality in Iran according to statistics is the occlusion of coronary arteries. Unfortunately almost one third of patients doesn’t have enough blood vessels to be used in the bypass surgery and need artificial vessels. These artificial blood vessels with small diameters (less than 6 mm) will fail quickly. As a result there is an increasing demand for tissue engineered blood vessels which are capable of enduring high blood pressures. An artificial blood vessel should mimic both structure and mechanical properties of the real one. Blood vessels have layered structures,... 

Atherosclerosis is one of the most important factors for mortality and morbidity in the world. Coronary artery bypass graft (CABG) is applied for treatment of this disease which in this surgery, the patient vessels, such as internal thoracic artery and saphenous vein, are harvested and grafted to the coronary arteries. The graft success and its performance in short and long-term are depended on the much factors e.g. the severity of stenosis in the coronary artery. It should be noted that the low level of stenosis in the coronary artery causes the creation of undesirable phenomenon of competitive flow in the grafts after the surgery which this phenomenon has been reported as a cause of graft... 

Cardiovascular diseases are the major cause of death worldwide. Atherosclerosis is one of the major types of cardiovascular diseases in which fibrous and fatty materials, called plaque, build up inside the artery and cause partial or total occlusion of the artery. Intravascular balloon angioplasty with or without stenting is the most common treatment of this disease. In 2010, approximately 954000 stent implantations were performed in the United States. The major issue associated with stenting is reclosure or renarrowing of the transverse section of the artery termed in-stent restenosis (ISR). Unfortunately, nearly one–third of the patients
who receive stent implantation require further... 

Heart disease is one of the major causes of death in all countries, especially developing countries. At the moment, using Image Processing methods as well as analysis of electrocardiographic signals, heart disease is diagnosed with the help of specialists. Applying artificial intelligence and machine learning methods, many studies attempted to provide models that are used to diagnose automatically the heart disease without the need for a specialist and only relying on the past data. But less is done on CTA images of the heart. Hence, in this thesis, a new method for image processing and a Multi Support Vector Machine (MSVM) classification for coronary artery disease detection based on CTA... 

Morphology and alignment of endothelial cells (ECs) have great influence on plaque formation. These alignments are based on the cyclic strains and wall shear stress (WSS) on the arterial wall. In the present study, cyclic strains and WSS are investigated to predict the secondary plaque locations downstream of the primary stenosis. Therefore, left coronary artery (LCA) with its branches to left anterior descending (LAD) and left circumflex (LCX) are 3D located on a virtual sphere to consider the cardiac motion. Stenoses are placed at the beginning of the bifurcation with varying degrees from 40% to 70% based on diameter reduction. Healthy coronary is also constructed to compare with those of... 

Atherosclerosis in coronary arteries is one of the most important topics due to its high prevalence and the importance of these arteries for supplying blood to the heart. The morphology of endothelial cells (ECs) is an independent index for determining the atheroprone sites. The ECs show a regular elongated and aligned configuration to the blood flow, at the atheroprotected regions; on the other hand, at the atheroprone regions, the cells have a polygonal, randomly oriented morphology. The thesis intended to propose a method for coronary artery simulation, which is able to determine the atheroprone sites regarding the ECs morphology. In addition, the attempts were made to investigate the... 

Obstruction of Left Anterior Descending artery (LAD) due to thrombosis or atherosclerotic plaques is the leading cause of death world–wide. Targeted delivery of drugs through micro- Nano-particles holds noteworthy promise which can make clot busting or the restenosis treatment with minimal toxicity possible. In this work, Fluid-Structure Interaction (FSI) simulations of blood flow through a patient-specific reconstructed geometry of LAD artery have been conducted using a non-Newtonian hematocrit (HCT) dependent model for blood. Based on physiological facts, 25, 45 and 65 percentages of HCT were assumed as acceptable representations of anemic, healthy and diabetic blood conditions,... 

In this study, three recent predictors of severity of coronary stenosis including fractional flow reserve (FFR), instantaneous wave free-ratio (iFR) and coronary flow reserve (CFR), are calculated for a number of patient-specific models of left coronary arteries. These patients are admitted to Tehran heart center. The main aim is presenting the optimum numerical and clinical detection technique to assess the severity of coronary stenosis. The effect of geometric features of stenosis is studied on the results of the FFR, iFR, and CFR in order to determine their accuracy. It is observed that CFR does not have a good estimate of the amount of disease. But, iFR, as a less risky test than FFR,... 

Cardiovascular diseases are major causes of morbidity and mortality in the world. In order to prevent or reduce these diseases, engineers and scientists are concerned to find solutions. In this way, it is important to know about the blood flow and its changes in various diseases. By using simulation methods, diagnosis can be very easier. In this study, a system of arterial tree consisting of 93 systemic arteries along with 7 pulmonary arteries is considered. In other words, this model contains 100 systemic and pulmonary arteries that encompass central and peripheral arteries. Other parts of this model are cerebral vasculature and coronary arteries. Cerebral arteries, also called circle of... 

In this thesis, hemodynamic parameters of flow and deposition of low density lipoproteins (LDL) on wall of coronary arteries with taking into account their curvature on the heart are studied. At first, numerical solution of the blood flow by assumption of blood as incompressible and Newtonian fluid for steady and pulsatile inlet is done. Then by assuming LDL particles as dilute solute in the blood, LDL transport from artery lumen into arterial wall is studied. LDL accumulation and penetration into the vessel wall cause thickening of the walls and eventually eclipse it and its known as the first stage of atherosclerosis disease. The results show that low shear region occurs on inner wall... 

Heart attack is considered as one of the most common reasons of morality all over the world. Coronary Atherosclerosis is known as the major causes of heart attack. The commence and proceed of this disease is related to cross of Low Density Lipoprotein. In this project, based on numerical simulation using ANSYS Fluent, hemodynamic variables and the rate of LDL particles penetration to porous wall of coronary artery is investgated. The geometry is the first bifurcation of Left Anterior Descending and is located on the supposed sphere that represents heart configuration. Sinsuidal variations of shere radii, simulates pulsating movement of heart. Heart diameter is supposed to remain constant... 

Due to increased atherosclerosis-caused mortality, identification of its genesis and development is of great importance. Although, key factors of the origin of the disease is still unknown, it is widely believed that cholesterol particle penetration and accumulation in arterial wall is mainly responsible for further wall thickening and decreased rate of blood flow during a gradual progression. To date, various effective components are recognized whose simultaneous consideration would lead to a more accurate approximation of Low Density Lipoprotein (LDL) distribution within the wall. In this research, a multilayer Fluid-Structure Interaction (FSI) model is studied to simulate the penetration... 

The Coronary artery bypass grafting surgery is one of the most complicated and invasive surgeries, in which the chest is cleaved up to 20 cm. Also, heart motion with 1-2Hz frequency bothers surgeons to perform on. This leads surgeons to get interested in minimally invasive robotic surgery methods. The idea is to synchronize the robot motion with heart, in order for surgeons to perceive it stationary. This needs 3 major stages: online taking of data, estimate the future heart motion, and control the robot. First studies employ visual seroving for control demand. Later studies, although differ in data collection methods, rely on classic error-based feedback controllers, such as PID. Fast... 

Cardiovascular disease is considered as the most important cause of death in the world. The coronary vessels, with three main arteries, has quite important. Coronary angiography is still the most common modality for physicians to assess the severity of vessel narrowing or stenosis during percutaneous coronary intervention procedure. For this procedure, a thin, flexible tube called a catheter is put into a blood vessel in your arm, groin (upper thigh), or neck. The tube is threaded into your coronary arteries, and the dye is released into your bloodstream. X-ray pictures are taken while the dye is flowing through the coronary arteries. Physicians evaluate angiographic images visually with... 

Cardiovascular diseases are very common nowadays and are one of the main reasons of death. Being among the major types of these diseases, correct and in time diagnosis of Coronary Artery Disease (CAD) is very important. The best and most accurate CAD diagnosis method by now is recognized as Angiography, which has many side effects and is costly. Thus researchers are seeking for inexpensive, though still accurate, methods. Existing studies have used several features in collecting data from patients, while applying different data mining algorithms to increase accuracy. In this thesis, a data set is introduced which utilizes several new and effective features for CAD diagnosis, as well as a... 

In this study, a practical approach for robotic beating heart surgery was proposed. This approach eliminates lateral movements of the heart and compensates for normal heart movement by using 1 DOF heart stabilizer and 1 DOF heart compensator simultaneously. It is a compromise between complete fixation of the heart, which damages the heart tissue, on one hand and complex and impractical compensation of the free heart movement on the other. One of the core components of the proposed system is the slave robot, which includes a 1 DOF compensator and a 4 DOF tool holder robot. Based on the selected laparoscopic tool, a modified agile-eye mechanism for activating the wrist was introduced,... 

Coronary arteries often experience tortuosity under internal blood pressure and longitude axial twisting. Arterial tortuosity can enhance the stress concentration on the artery walls. Now if the coronary arteries suffer from atherosclerosis (a common disease among adults) the stress concentration on the tortuous artery plaque will be enhanced as well. Increased stress on the plaque may result in plaque rupture and its consequent damages. This study aims to investigate the stress concentration on the plaques and blood flow patterns within the coronary arteries with plaque. Moreover, the plaque growth was predicted taking into account various geometrical parameters including fibrous cap... 

Atherosclerosis, due to the penetration of low-density lipoprotein particles (LDL) into the arterial wall, is one of the most common and death-leading diseases in today's world. Due to its importance, extensive research has been conducted on the factors that affect this disease. In this thesis, a numerical study of the effects of Wall Shear Stress (WSS), non-Newtonian behavior of blood, different hematocrit values, and blood pressure on LDL permeation through the artery wall layers are investigated in a 4-layer wall model of a coronary bifurcation. To obtain the velocity and concentration fields in the domain, momentum, Brinkman, and mass transport equations are solved in the lumen and wall...