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hemodynamics
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2-D Modeling of Blood Flow in Mitral Valve During its Closing and Opening
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Saeedi, Mohammad Saeed (Co-Supervisor)
Abstract
Problems with the mitral valve can make the heart less efficient at pumping blood around the body. Severe problems can lead to heart failure if the valve is not surgically repaired or replaced. A simple approximation of the heart geometry is used and the valve dimensions are based on reported measurements. The primary objective for this study is to design and simulate the opening and closing behavior of the mitral valve using 2D fluid-structure interaction (FSI) model using ADINA software in order to evaluate and investigate the hemodynamic performance and problems of mitral valve, in which the blood is described as a viscous incompressible fluid, and the mitral valve is described as an...
Design and Implementation of an Optical Intrinsic Signal Imaging System for Brain by Using Intensity Magnification Algorithm
, M.Sc. Thesis Sharif University of Technology ; Fardmanesh, Mahdi (Supervisor) ; Ghazizadeh Ehsaee, Ali (Supervisor)
Abstract
In many neuroscience studies, the aim is to investigate the functional role of a population of neurons in response to a certain stimulus. Electrophysiology methods usually can only record from a small population of neurons and this is not sufficient for studying functional properties of the cortex. An alternative is to use functional neuroimaging methods. However, some of these methods are expensive and also they do not offer suitable spatial and temporal resolutions. Optical imaging systems can solve these problems because they are low-cost, easy to design, and also have good temporal and spatial resolutions. These systems can generate functional maps from the brain. In this study, a...
Design of the Coronary Stent Device to Improve Fluid Flow in Coagulated Vascular Regions
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor)
Abstract
The application of computational fluid dynamics (CFD) has been growing rapidly in biomedical engineering. The altered hemodynamics inside the blood vessels plays a key role in the development of the arterial disease called atherosclerosis, which is the major cause of human death worldwide. Atherosclerosis is often treated with the stenting procedure to restore the normal blood flow. A stent is a tubular, flexible structure, usually made of metals, which is driven and expanded in the blocked arteries. The presence of non-biological device in the artery causes inflammation or re-growth of atherosclerotic lesions in the treated vessels. Several factors including the design of stents and type of...
Simulation of LAD-LCX Bifurcation Hemodynamics of Coronary Artery Disease to Design an Effective Bypass Graft
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor) ; Pakravan, Hossein Ali (Co-Supervisor)
Abstract
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,...
Simulation of the Blood Flow in a Stenotic Left Coronary Bifurcation to Study the Effects on the Endothelial Cells
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor)
Abstract
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...
Towards obtaining more information from gas chromatography-mass spectrometric data of essential oils: An overview of mean field independent component analysis
, Article Journal of Chromatography A ; Volume 1217, Issue 29 , 2010 , Pages 4850-4861 ; 00219673 (ISSN) ; Parastar, H ; Sereshti, H ; Sharif University of Technology
2010
Abstract
Mean field independent component analysis (MF-ICA) along with other chemometric techniques was proposed for obtaining more information from multi-component gas chromatographic-mass spectrometric (GC-MS) signals of essential oils (mandarin and lemon as examples). Using these techniques, some fundamental problems during the GC-MS analysis of essential oils such as varying baseline, presence of different types of noise and co-elution have been solved. The parameters affecting MF-ICA algorithm were screened using a 25 factorial design. The optimum conditions for MF-ICA algorithm were followed by deconvolution of complex GC-MS peak clusters. The number of independent components (ICs) (chemical...
Time-dependent analysis of leaflets in mechanical aortic bileaflet heart valves in closing phase using the finite strip method
, Article Medical Engineering and Physics ; Volume 28, Issue 2 , 2006 , Pages 122-133 ; 13504533 (ISSN) ; Ahmadian, M. T ; Wan, W. K ; Sharif University of Technology
2006
Abstract
Background and aims of the study: Mechanical heart valves (MHV) are widely used to replace dysfunctional and failed heart valves. The bileaflet MHV design is very popular due to its superior hemodynamics. Since their introduction in 1977, the hemodynamics of bileaflet prostheses has been extensively studied. In this study the dynamic behaviour during the closing phase of a bileaflet MHV under normal physiological conditions has been investigated. Methods: Fluid analysis is based on the control volume with moving boundaries in the vicinity of the occluder. Unsteady continuity equation, unsteady momentum equation on the control volume and unsteady Bernoulli's equation have been used to...
The pulsatile flow of Oldroyd-B fluid in a multi-stenosis artery with a time-dependent wall
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 4 , 2010 , Pages 915-923 ; 09544062 (ISSN) ; Fakhimghanbarzadeh, B ; Sharif University of Technology
Abstract
In this study, the fundamental problem of unsteady blood flow in a tube with multi-stenosis is studied. An appropriate shape of the time-dependent multi-stenosis which is overlapping in the realm of formation of arterial narrowing is constructed mathematically. Blood is considered as a viscoelastic fluid characterized by the Oldroyd-B model. For the numerical solution of the problem, which is described by a coupled, non-linear system of partial differential equations (PDEs), with appropriate boundary conditions, the finite difference scheme is adopted. The solution is obtained by the development of an efficient numerical methodology based on the predictor-corrector method. The effects of...
The importance of fluid-structure interaction simulation for determining the mechanical stimuli of endothelial cells and atheroprone regions in a coronary bifurcation
, Article Scientia Iranica ; Volume 23, Issue 1 , 2016 , Pages 228-237 ; 10263098 (ISSN) ; Saidi, M. S ; Firoozabadi, B ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
The function and morphology of Endothelial Cells (ECs) play a key role in atherosclerosis. The mechanical stimuli of ECs, such as Wall Shear Stress (WSS) and arterial wall strain, greatly inuence the function and morphology of these cells. The present article deals with computations of these stimuli for a 3D model of a healthy coronary artery bifurcation. The focus of the study is to propose an accurate method for computations of WSS and strains. Two approaches are considered: Coupled simultaneous simulation of arterial wall and blood flow, called fluid-Structure Interaction (FSI) simulation, and decoupled, which simulates each domain (fluid and solid domain) separately. The study...
The effect of hematocrit and nanoparticles diameter on hemodynamic parameters and drug delivery in abdominal aortic aneurysm with consideration of blood pulsatile flow
, Article Computer Methods and Programs in Biomedicine ; Volume 195 , October , 2020 ; Nasiri Sadr, A ; Kaffash, E ; Goudarzi, S ; Golab, E ; Karimipour, A ; Sharif University of Technology
Elsevier Ireland Ltd
2020
Abstract
Background and Objective: The present article has simulated to investigate the efficient hemodynamic parameters, the drug persistence, and drug distribution on an abdominal aortic aneurysm. Methods: Blood as a non-Newtonian fluid enters the artery acting as a real pulse waveform; its behavior is dependent on hematocrit and strain rate. In this simulation of computational fluid dynamic, magnetic nanoparticles of iron oxide which were in advance coated with the drug, are injected into the artery during a cardiac cycle. A two-phase model was applied to investigate the distribution of these carriers. Results: The results are presented for different hematocrits and the nanoparticle diameter. It...
Targeted drug delivery of magnetic microbubble for abdominal aortic aneurysm: an in silico study
, Article Biomechanics and Modeling in Mechanobiology ; Volume 21, Issue 2 , 2022 , Pages 735-753 ; 16177959 (ISSN) ; Ebrahimi, S ; Ghorbani, G ; Alishiri, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Targeted drug delivery (TDD) to abdominal aortic aneurysm (AAA) using a controlled and efficient approach has recently been a significant challenge. In this study, by using magnetic microbubbles (MMBs) under a magnetic field, we investigated the MMBs performance in TDD to AAA based on the amount of surface density of MMBs (SDMM) adhered to the AAA lumen. The results showed that among the types of MMBs studied in the presence of the magnetic field, micromarkers are the best type of microbubble with a −50 % increase in SDMM adhered to the critical area of AAA. The results show that applying a magnetic field causes the amount of SDMM adhered to the whole area of AAA to increase −1.54 times...
Stress analysis of internal carotid artery with low stenosis level: the effect of material model and plaque geometry
, Article Journal of Mechanics in Medicine and Biology ; Volume 17, Issue 6 , 2017 ; 02195194 (ISSN) ; Ghorbannia Hassankiadeh, A ; Sharif University of Technology
Abstract
Stress concentration in carotid stenosis has been proven to assist plaque morphology in disease diagnosis and vulnerability. This work focuses on numerical analysis of stress and strain distribution in the cross-section of internal carotid artery using a 2D structure-only method. The influence of four different idealized plaque geometries (circle, ellipse, oval and wedge) is investigated. Numerical simulations are implemented utilizing linear elastic model along with four hyperelastic constitutive laws named neo-Hookean, Ogden, Yeoh and Mooney-Rivlin. Each case is compared to the real geometry. Results show significant strength of oval and wedged geometries in predicting stress and strain...
Simulation of red blood cell motion in microvessels using modified moving particle semi-implicit method
, Article Scientia Iranica ; Volume 19, Issue 1 , 2012 , Pages 113-118 ; 10263098 (ISSN) ; Firoozbakhsh, K ; Hasanian, M ; Sharif University of Technology
Abstract
Red Blood Cells (RBCs) are the main cells in human blood, with a main role in the mechanical properties of blood as a fluid. Several methods have been improved to simulate the mechanical behavior of RBC in micro-capillaries. Since, in microscopic scales, using discrete models is more preferred than continuum methods, the Moving Particle Semi-Implicit method (MPS), which is a recent innovative particle based method, can simulate micro-fluidic flows based on NavierStokes equations. Although, by recent developments, the MPS method has turned into a considerable tool for modeling blood flow in micro meter dimensions, some problems, such as a commitment to use small time step sizes, still...
Pulsatile flow of viscous and viscoelastic fluids in constricted tubes
, Article Journal of Mechanical Science and Technology ; Volume 23, Issue 9 , 2009 , Pages 2456-2467 ; 1738494X (ISSN) ; Esmaeili, M ; Majidi, S ; Fakhimghanbarzadeh, B ; Sharif University of Technology
2009
Abstract
The unsteady flow of blood through stenosed artery, driven by an oscillatory pressure gradient, is studied. An appropriate shape of the time-dependent stenoses which are overlapped in the realm of the formation of arterial narrowing is constructed mathematically. A msathematical model is developed by treating blood as a non-Newtonian fluid characterized by the Oldroyd-B and Cross models. A numerical scheme has been used to solve the unsteady nonlinear Navier-stokes equations in cylindrical coordinate system governing flow, assuming axial symmetry under laminar flow condition so that the problem effectively becomes two-dimensional. Finite difference technique was used to investigate the...
Pulsatile blood flow in total cavopulmonary connection: a comparison between Y-shaped and T-shaped geometry
, Article Medical and Biological Engineering and Computing ; Volume 55, Issue 2 , 2017 , Pages 213-224 ; 01400118 (ISSN) ; Firoozabadi, B ; Saidi, M. S ; Monjezi, M ; Navabi Shirazi, M. A ; Malakan Rad, E ; Sharif University of Technology
Springer Verlag
2017
Abstract
Single-ventricle anomaly is a hereditary heart disease that is characterized by anatomical malformations. The main consequence of this malformation is desaturated blood flow, which without proper treatment increases the risk of death. The classical treatment is based on a three-stage palliative procedure which should begin from the first few days of patient’s life. The final stage is known as Fontan procedure, in which inferior vena cava is directly connected to pulmonary arteries without going through the ventricle. This connection is called total cavopulmonary connection (TCPC). After surgery, the single ventricle supplies adequate and saturated systemic blood flow to the body; however,...
Prediction of acute hypotension episodes using Logistic Regression model and Support Vector Machine: A comparative study
, Article 2011 19th Iranian Conference on Electrical Engineering, ICEE 2011, 17 May 2011 through 19 May 2011 ; May , 2011 , Page(s): 1 - 4 ; ISSN :21647054 ; 9789644634284 (ISBN) ; Arasteh, A ; Moradi, M. H ; Sharif University of Technology
2011
Abstract
Acute hypotension episodes are one of the hemodynamic instabilities with high mortality rate that is frequent among many groups of patients. Prediction of acute hypotension episodes can help clinicians to diagnose the cause of this physiological disorder and select proper treatment based on this diagnosis. In this study new physiological time series are generated based on heart rate, systolic blood pressure, diastolic blood pressure and mean blood pressure time series. Statistical features of these time series are extracted and patients whom are exposed to acute hypotension episodes in future 1 hour time interval and whom are not, are classified based on these features and with the aid of...
Plaque structure affects mechanical stress distribution within blood vessels
, Article Proceedings of the IASTED International Conference on Biomedical Engineering, BioMed 2014 ; 2014 , pp. 239-243 ; Mehboudi, N ; Abdollahi, M ; Shamloo, A ; Naghdabadi, R ; Sharif University of Technology
Abstract
The main goal of this study is to investigate the effects of plaque structure on its stress distribution. Rupture of plaque causes cerebrovascular diseases which lead to high mortality rates all over the world. Computers are powerful tools to understand the mechanism of plaque rupture. In this study, 3D fluid structure interaction simulation is constructed in ABAQUS 6.13 to clarify the relation between stress distribution of plaque and its structure. A model of common carotid artery with distributed stenosis was chosen for the simulation. To investigate the effects of plaque structure on stress distribution, thickness of fibrous cap and lipid core size were varied in the stenosis....
Personalised deposition maps for micro- and nanoparticles targeting an atherosclerotic plaque: attributions to the receptor-mediated adsorption on the inflamed endothelial cells
, Article Biomechanics and Modeling in Mechanobiology ; Volume 18, Issue 3 , 2019 , Pages 813-828 ; 16177959 (ISSN) ; Forouzandehmehr, M ; Sharif University of Technology
Springer Verlag
2019
Abstract
Endothelial inflammation as a prominent precursor to atherosclerosis elicits a distinct pathological surface expression of particular vascular proteins. To exhibit a site-specific behaviour, micro- and nanoparticles, as carriers of therapeutics or imaging agents, can distinguish and use these proteins as targeted docking sites. Here, a computational patient-specific model capturing the exclusive luminal qualities has been developed to study the transport and adsorption of particles decorated with proper antibodies over an atherosclerotic plaque located in the LAD artery of the patient. Particles, in nano- and micron sizes, have been decorated with Sialyl Lewisx (sLex), P-selectin aptamer...
Patient-specific fluid–structure interaction simulation of the LAD-ITA bypass graft for moderate and severe stenosis: A doubt on the fractional flow reserve-based decision
, Article Biocybernetics and Biomedical Engineering ; Volume 42, Issue 1 , 2022 , Pages 143-157 ; 02085216 (ISSN) ; Firoozabadi, B ; Pakravan, H. A ; Ahmadi Tafti, S. H ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Fractional flow reserve (FFR)-based decision improves the outcomes of percutaneous coronary intervention (PCI) for some patients, while its effectiveness in improving the results of coronary artery bypass graft (CABG) is unclear, in particular for moderate stenosis. It may be due to the fact that FFR cannot take into account the impacts of competitive flow (CF), intimal hyperplasia (IH), as well as compliance mismatch (CMM). As a result, two questions arise 1) whether FFR is a sufficient factor to decide to perform the CABG for patients with moderate to severe stenosis or not and 2) whether post-operative FFR shows the effectiveness of a graft. To shed light on this matter, two...
Numerical study of the effect of vascular bed on heat transfer during high intensity focused ultrasound (HIFU) ablation of the liver tumor
, Article Journal of Thermal Biology ; Volume 86 , 2019 ; 03064565 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this study, the influence of vascular bed comprising terminal arterial branches on heat transfer in a liver tumor exposed to high intensity focused ultrasound (HIFU) is studied numerically. Also, the effect of vascular density on temperature distribution is investigated. A coupled set of acoustics, thermal, and fluid models is used to calculate the temperature distribution in the liver. The numerical model is established based on the Westervelt and bioheat equations along with the Navier-Stokes equations. Moreover, the acoustic streaming effect is included with Newtonian and non-Newtonian flow assumptions. It is found that in a vascular bed comprising terminal arterial branches, the...