Haemodynamics analysis of carotid artery stenosis and carotid artery stenting

Carotid stenosis is a local narrowing of the carotid artery, and is usually found in the internal carotid artery. The presence of a high-degree stenosis in a carotid artery may provoke transition from laminar to turbulent flow during part of the cardiac cycle. Turbulence in blood flow can influence haemodynamic parameters such as velocity profiles, shear stress and pressure, which are important in wall remodelling. Patients with severe stenosis could be treated with a minimally invasive clinical procedure, carotid artery stenting (CAS). Although CAS has been widely adopted in clinical practice, the complication of in-stent restenosis (ISR) has been reported after CAS. The incidence of ISR is influenced by stent characteristics and vessel geometry, and correlates strongly with regions of neointimal hyperplasia (NH). Therefore, the main purpose of this study is to provide more insights into the haemodynamics in stenosed carotid artery and in post-CAS geometries via computational simulation. The first part of the thesis presents a computational study on flow features in a stenotic carotid artery bifurcation using two computational approaches, large eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) incorporating the Shear Stress Transport model with the γ-Reθ transition (SST-Tran) models. The computed flow patterns are compared with those measured with particle image velocimetry (PIV). The results show that both SST-Tran and LES can predict the PIV results reasonably well, but LES is more accurate especially at locations distal to the stenosis where flow is highly disturbed. The second part of the thesis is to determine how stent strut design may influence the development of ISR at the carotid artery bifurcation following CAS. Key parameters that can be indicative of ISR are obtained for different stent designs and compared; these include low and oscillating wall shear stress (WSS), high residence time, and wall stress. A computationally efficient methodology is employed to reproduce stent strut geometry. This method facilitates the accurate reconstruction of actual stent geometry and details of strut configuration and its inclusion in the fluid domain. Computational simulations for flow patterns and low-density lipoprotein (LDL) transport are carried out in order to investigate spatial and temporal variations of WSS and LDL accumulation in the stented carotid geometries. Furthermore, finite element (FE) analysis is performed to evaluate the wall stress distribution with different stent designs. The results reveal that the closed-cell stent design is more likely to create atheroprone and procoagulant flow conditions, causing larger area to be exposed to low wall shear stress (WSS), elevated oscillatory shear index, as well as to induce higher wall stress compared to the open-cell stent design. This study also demonstrates the suitability of SST-Tran and LES models in capturing the presence of complex flow patterns in post-stenotic region.Open Acces

Effects of stent design on LDL accumulation at the carotid artery bifurcation

Restenosis typically occurs in regions of low and oscillating wall shear stress which also favours the accumulation of atherogenic macromolecules such as low-density lipoprotein (LDL). This study aims to determine how stent strut design may affect in-stent restenosis at the carotid artery bifurcation following carotid artery stenting (CAS) by means of computational simulation. LDL concentrations were compared for post-stent carotid and the contralateral models reconstructed from patient-specific images. Our results show that closed-cell stent designs are more likely to create atheroprone and procoagulant flow conditions than open-cell designs due to larger area exposed to high LDL concentration

Modeling the effect of different locations of carotid atherosclerosis on hemodynamics parameters

Carotid atherosclerosis is a potentially fatal diseases caused by plaques buildup in arteries that deliver blood to the brain. Over the years, this pathological condition particularly the stenosis size severity has been studied, and computational fluid dynamics has played an essential role in investigating the blood flow behavior. However, the study on the effect of stenosis location especially at the area of bifurcation is still lacking. This study aims to investigate which stenosis location would cause higher risk factor and high flow disturbance to the blood flow. The area susceptible for atherosclerosis is usually at the carotid bifurcation where common carotid artery (CCA) is bifurcated into internal carotid artery (ICA) and external carotid artery (ECA). The computational simulations were performed using idealized geometry of carotid artery with different locations of stenoses. Type I, II and III stenoses were grouped according to the most common type and location stenosis. The results show that the Type I geometry with stenosis extended toward the ICA had higher possibility for the atherosclerosis plaque to grow. Velocity profiles and low wall shear stress contours predicted more complex helical and recirculation blood flow at post-stenotic region of Type I as compared to the other two. The findings indicate that atherosclerosis plaque in the ICA could provide higher risk to the patient and immediate medical treatment shall be required

Brief review on recent technology in particle image velocimetry studies on hemodynamics in carotid artery

Cardiovascular disease is number one causes of morbidity and mortality in global. In-vitro studies are widely applied in the investigation of blood flow under pathological conditions to diagnose atherosclerosis in carotid arteries. In this manuscript, a brief review on the latest published articles was con ducted according to Preferred Reporting Items for Systematic Reviews and Me ta-Analyses on the particle image velocimetry (PIV) studies of blood flow in carotid artery geometries. Fourteen (14) recent articles on PIV from 2016 to 2020 in Scopus, PubMed and ScienceDirect databases were included. The data of the published articles were focused on the technical aspects of PIV flow measurement and were organized in two categories i.e. carotid phantom geometries constructions and the blood mimicking flow circuits. This systematic re view paper summarises the updated methodology in the PIV and identify potential areas to elucidate the accuracy and limitations of each method

The kicking performance by different boots material

Introduction: The purpose of this study was to investigate the kinematics of kicking by experimental and simulation techniques analysis. The differences of material stiffness will affected to the ball velocities. Experimental setup by high speed video camera with 250 frames per second was performed in order to obtain the foot and ball velocities during the kicking process. There are 10 male football players from majlis sukan negeri terengganu (MSNT) were selected as subjects. Instep kicking with right foot was choosing due to the highest ball velocities can be produced by this technique. Simulation analysis by finite element analysis (FEA) then used to validate the results from experimental work done. Polyethylene material and 2.0mm thickness from boot c was considered as the best boot design compared to the others. It gives the highest maximum stress and the highest force to produce the highest ball velocity. The other variables related to the ball velocity such as coefficient of restitution (COR) and contact time. This study is useful to design the suitable material for each region of boots. It also can help the athletes to identify the characteristics of boot selection for different position on the field

Comparative analysis on raster, spiral, hilbert, and peano mapping pattern of fragile watermarking to address the authentication issue in healthcare system

Healthcare service is one of the focus areas in supporting the existence of smart city. Nowadays, many procedures are done paperless and fully in digital. Medical scanning is also stored in digital modalities format and transmitted through a hospital management system. An authentication system is needed during the transmission, thus the need of watermarking. Some interesting research directions in watermarking include the embedding pattern of watermark data in the early process of watermarking. The objective of this research is to investigate the best pattern to determine the bit locations for watermark embedding for copyright protection. This paper applies four types of embedding patterns on medical images, which the quality of watermarked images would depend on how the mapping pattern is. It compares the difference of having a straight forward pattern mapping as a raster pattern and a unique pattern mapping like spiral, Hilbert, and Peano patterns. After mapping, all would have the same stages of a watermarking scheme which are embedding, detection and recovery stage. The comparison factors include the peaksignal-noise-ratio, mean-squared-error values of embedded images, and the computational time. From the result, the significant difference is the computational time; the taken time by the unique pattern is significantly longer than raster. When it comes to handling superabundant data, it is very crucial to produce a user-friendly system. However, as a whole, the results from Peano pattern embedding scheme shows it has a unique pattern which hard to be tracked, yet, its computational time to watermark is acceptable

Head injury evaluation strategy for sepak takraw ball heading: a systematic review

Since Sepak Takraw was introduced in 1965 in South East Asian Peninsular (SEAP) Games, the players have intensively trained the heading ball as the main movement during the game. The impacts of repetitive Takraw ball heading, however, can lead to brain traumatic injuries such as concussion, internal bleeding and dizziness. This article set out the current trend and research gap on head impact injury during sepak takraw ball heading. Guided review method using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) Statement has identified 26 related studies from Scopus, Web of Science, and PubMed databases. This review from 2014 to 2021 resulted in only one article has been carried out on sepak takraw ball heading head injury and 25 articles on soccer and lacrosse. Six main themes have resulted from further review of the articles in measurement strategy, type of head impact, measurement tool, output data, subject category, and head protector in sepak takraw to study the ball heading head impacts. A total of 26 sub-themes further has been produced by the six themes.Several recommendations are proposed to conduct laboratory experimental studies considering ball-to-head heading only and studying headband for concussion reduction considering both linear and angular kinematics as the head injury predictors

Modeling of soft tissue deformation using mass spring method with nonlinear volume force

Soft tissues displayed two phases of deformation, linear behavior during small deformation and nonlinear behavior during large deformation. Mass Spring Method (MSM) is one of the preferred methods for simulating soft tissue deformations. MSM-based models provide simpler calculations that allow realtime interaction. However, only a small number of MSM models are capable of simulating two phases of soft tissue deformation. This study introduces a new approach to modeling the deformation. The conventional MSM model, which is governed by Hooke’s law, is coupled with the nonlinear volume force defined using the conical spring methodology. The nonlinear volume force is triggered by a change in volume in the structure of the MSM model. With the implementation, at small deformation where volume change is also small, only the Hooke’s law equation is activated resulting in linear deformation. Whereas, during large deformation, nonlinear deformation occurs as a result of a large change in the MSM volume. Analyzes conducted show that the proposed model can simulate the two phases of deformation. The proposed model can also control each phase independently, which shows that it has a high degree of flexibility on modeling various of soft tissue deformation

Covid-19 Embedded with Aerosol Particles Travel Simulation Inside a Mosque

When an infected person coughs, thousands of micro-size aerosol particles will transmit to the surrounding, especially in a closed space. Mosque is one of the confined areas that Muslims regularly go to pray together. Multiple standards of procedures have been proposed to prevent the virus transmission, however, the cases involving people praying in mosque are still reported. This study aims to simulate the virus transmission in mosque by modelling the aerosol particles generated by the worshipper coughing. A geometry of praying area in mosque was created mimicking the actual praying space. Realistic boundary conditions involving coughing, airflow at the inlet and outlet diffusers were specified. The simulation result confirms that the SARS-COV-2 virus in a closed space praying room is not uniform and it is strongly influenced by the location of the coughing source and the air conditioning layout. The study also recorded Ma’mums are at the higher chance to get infected if one of the Ma’mum is the COVID-19 carrier due to the nature of normal congregational praying arrangement. The outcomes of this study may help the scientist and the authorities to understand how dramatic COVID-19 virus may spread in the confined praying area, hence, may enforce a better standard of procedure in a mosque

A Study on the Wear Resistance and Lubrication Properties of Mixed Engine Oils

Engine oils have traditionally served as the principal lubrication for combustion engines. With so many engine oils on the market, each has its unique set of ingredients and qualities that set it apart from the others. Customers are often influenced by the variety to switch between different types of engine oil. The wear resistance and lubrication properties of a few mixtures of different engine oil brands are investigated in this study. Three brands of engine oil were chosen and mixed in a 1:1 weight ratio. The viscosity, coefficient of friction (COF), and wear scar diameter (WSD) of the mixtures were determined using the Four-ball tribotester and viscosity testing equipment at three testing periods. The results demonstrate that the mixtures act differently than pure oil. Even though the mixing yielded more viscous lubricants, which is preferred, the data reveal that the COF and WSD also increased. The mixing might cause chemical interactions between additives, causing the oil's structure to change. According to this study, using pure oil is superior for extending the life of a combustion engine