Quantitative cardiac ultrasound

This thesis is about the various aspects of quantitative cardiac ultrasound. The first four chapters are mainly devoted to the reproducibility of echocardiographic measurements. These . are focussed on the variation of echocardiographic measurements within patients. An important issue, since this variation determines the distinction between a real change of the measurement in a single patient or a_ difference caused by chance. The problems of the estimation of the variation of measurements within patients and its clinical implications are elaborated more specifically for Doppler velocity measurements and for cardiac volume determinations using cross-sectional echocardiography. Next, there are two chapters about echocardiographically determined normal ranges of cardiac dimensions. These reference ranges provide for the quantitative distinction between sickness and health. The last two chapters of this thesis deal with the newest aspect of quantitative cardiac ultrasound: non-invasive cardiac tissue characterisation using integrated backscatter measurements. These chapters are focussed on the distinction between normal myocardial tissue and acute ischemic cardiac muscl

Characterization of Arterial Flow for Junctional Bleeding Control

This study investigated reducing volumetric flowrate under steady flow conditions by varying lengths of compression with constant cross-sectional area and varying cross-sectional area reduction with constant length in order to better understand how to control junctional hemorrhaging. The hypotheses of this study were that length reduction will have little effect on volumetric flowrate and that cross-sectional area reduction would need to be approximately 80 percent in order to obtain bleeding control. The study found that length reduction has little effect on changing the flowrate. However, in order to obtain at least 80 percent reduction in flow, the area needs to be occluded by at least 95 percent. These results may help inform better tourniquet designs by using collapsible tube science

Numerical analysis of the impact of flow rate, heart rate, vessel geometry, and degree of stenosis on coronary hemodynamic indices

Background: The stenosis of the coronary arteries is usually caused by atherosclerosis. Hemodynamic significance of patient-specific coronary stenoses and the risk of its progression may be assessed by comparing the hemodynamic effects induced by flow disorders. The present study shows how stenosis degree and variable flow conditions in coronary artery affect the oscillating shear index, residence time index, pressure drop coefficient and fractional flow reserve. We assume that changes in the hemodynamic indices in relation to variable flow conditions and geometries evaluated using the computational fluid dynamics may be an additional factor for a non-invasive assessment of the coronary stenosis detected on multi-slice computed tomography. Methods: The local-parametrised models of basic shapes of the vessels, such as straight section, bend, and bifurcation as well as the global-patient-specific models of left coronary artery were used for numerical simulation of flow in virtually reconstructed stenotic vessels. Calculations were carried out for vessels both without stenosis, and vessels of 10 to 95% stenosis. The flow rate varied within the range of 20 to 1000 ml/min, and heart rate frequency within the range of 30 to 210 cycles/min. The computational fluid dynamics based on the finite elements method verified by the experimental measurements of the velocity profiles was used to analyse blood flow in the coronary arteries. Results: The results confirm our preliminary assumptions. There is significant variation in the coronary hemodynamic indices value caused by disturbed flow through stenosis in relation to variable flow conditions and geometry of vessels. Conclusion: Variations of selected hemodynamic indexes induced by change of flow rate, heart rate and vessel geometry, obtained during a non-invasive study, may assist in evaluating the risk of stenosis progression and in carrying out the assessment of the hemodynamic significance of coronary stenosis. However, for a more accurate assessment of the variability of indices and coronary stenosis severity both local (near the narrowing) and global (in side branches) studies should be used

Investigation on the Deformation of Cutaneous Blood Vessel in Relation to Pressure Ulcer Formation by Computational Modelling

Pressure ulcer is a serious injury which affects the skin integrity of patients and is a financial burdens to healthcare providers worldwide. Pressure ulcers are usually caused either by excessive stress or ischemia which appears as deep tissue injury and superficial pressure ulcers respectively. Some of the pressure ulcers are known to be caused by the application of medical devices. These medical device related pressure ulcers are usually superficial and contribute to a significant numbers of the total number of pressure ulcers. The engineering community often focuses on the aetiology of excessive stress by developing computational models and investigating the in vivo conditions when a patient is subject to high loads. Limited attempts have been made on developing computational models for the aetiology of ischemia. Hence, it is the aim of the study to develop computational model to investigate the deformation of the cutaneous blood vessels in relation to the formation of superficial pressure ulcers. This study provides information on the magnitudes of interface pressure experienced by patients in clinical setting experimentally by using pressure mapping system on both static and dynamic mattresses. Computational models are developed to demonstrate the in vivo cutaneous conditions and the relationship of mechanical loadings and the deformation of cutaneous blood vessels is established. The computational results is further correlated to a set of physiological data acquired by using laser Doppler technique to enhance the clinical relevance. The computational models and the established correlation is applied in three situations including; evaluating the effect of oxygen facial delivery masks on patients’ skin; understanding the effect of same magnitude mechanical load on different skin conditions, and converting an external parameter, interface pressure from mattresses testing, into a physiological parameter. The overall study provides a novel tool for the medical device developers in evaluating the effects of their devices on patients’ skin in relation to the formation of superficial pressure ulcers. The computational models and the established correlation with the physiological data allows the clinicians to understanding the in vivo cutaneous conditions of patients rather than just evaluating an external parameter

Epidemiology of intracranial stenosis in asymptomatic Asian subjects.

Tang, Suk Yan Amy.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references (leaves [207]-[227]).Abstracts in English and Chinese.ACKNOWLEDGEMENTSABSTRACTSTABLE OF CONTENTS"LIST OF APPENDIX, TABLES & FIGURES"Chapter CHAPTER ONE --- INTRODUCTION --- p.1Chapter 1.1 --- Cerebrovascular disease --- p.1Chapter 1.1.1 --- Ischemic Stroke --- p.1Chapter 1.1.2 --- Hemorrhagic Stroke --- p.2Chapter 1.2 --- Laboratory diagnosis --- p.3Chapter 1.2.1 --- Transcranial Doppler ultrasonography --- p.4Chapter 1.2.1.1 --- Normal Brain --- p.4Chapter 1.2.1.2 --- Intracranial Large Artery Stenosis --- p.5Chapter 1.3 --- Asymptomatic Intracranial Stenosis --- p.6Chapter CHAPTER TWO --- LITERATURE REVIEW --- p.7Chapter 2.1 --- Global Stroke Facts --- p.7Chapter 2.2 --- Stroke Studies --- p.7Chapter 2.2.1 --- Risk profile of stroke --- p.7Chapter 2.2.2 --- Stroke epidemiological study --- p.8Chapter 2.2.2.1 --- Incidence --- p.8Chapter 2.2.2.2 --- Mortality --- p.10Chapter 2.2.2.3 --- Increased stroke rates with increased age --- p.12Chapter 2.2.2.4 --- Associated disease in stroke subjects --- p.12Chapter 2.2.3 --- Stroke risk factors --- p.13Chapter 2.3 --- Stroke Impact --- p.14Chapter 2.3.1 --- Stroke patients --- p.14Chapter 2.3.2 --- Medical burden --- p.15Chapter 2.3.3 --- Socioeconomic burden --- p.16Chapter 2.4 --- Stroke Prevention --- p.17Chapter 2.5 --- Stroke Facts in Hong Kong --- p.19Chapter 2.6 --- Stroke Facts in China --- p.21Chapter 2.7 --- Asymptomatic Intracranial Stenosis in Asian Subjects --- p.22Chapter 2.7.1 --- Asymptomatic individuals --- p.22Chapter 2.7.2 --- Intracranial occlusive disease --- p.23Chapter 2.8 --- Transcranial Doppler Sonography --- p.25Chapter CHAPTER THREE --- AIM & OBJECTIVES OF THE RESEARCH --- p.30Chapter 3.1 --- Aim of the research --- p.30Chapter 3.2 --- Objectives of this research --- p.30Chapter CHAPTER FOUR --- "CLINIC-BASED CROSS-SECTIONAL SCREENING IN AN URBAN CITY 226}0ؤ HONG KONG, THE PEOPLE'S REPUBLIC OF CHINA" --- p.31Chapter 4.1 --- Background & Purpose --- p.31Chapter 4.2 --- Methods --- p.34Chapter 4.2.1 --- Defining the population --- p.34Chapter 4.2.2 --- Procedures --- p.36Chapter 4.2.2.1 --- Standardized TCD Report Form --- p.39Chapter 4.2.2.2 --- Transcranial Doppler Screening --- p.39Chapter 4.2.2.3 --- Data collected --- p.40Chapter 4.2.3 --- Defining the Risk Factors --- p.43Chapter 4.3 --- Statistical Analyses --- p.45Chapter 4.3.1 --- Research Design --- p.46Chapter 4.3.2 --- Descriptive Summary --- p.46Chapter 4.3.2.1 --- Cross-tabulated between Gender --- p.46Chapter 4.3.2.2 --- Cross-tabulated between Normal & Abnormal MCA status --- p.47Chapter 4.3.3 --- Measures for Association --- p.48Chapter 4.3.3.1 --- Univariate analysis --- p.48Chapter 4.3.3.2 --- Multivariate analysis --- p.48Chapter 4.3.4 --- Modeling the Risks --- p.50Chapter 4.3.5 --- nfluence of the number of associated risk factors on the MCA status --- p.50Chapter 4.4 --- Result --- p.51Chapter 4.4.1 --- Baseline characteristics of all screened subjects by Gender --- p.51Chapter 4.4.1.1 --- Age by Gender --- p.53Chapter 4.4.1.2 --- "Medical History of HT, DM, Hyperlipidemia, IHD, Retinopathy and Albuminuria by Gender" --- p.55Chapter 4.4.1.3 --- Social habit in Smoking by Gender --- p.56Chapter 4.4.1.4 --- Body Mass Index and Waist-to-Hip Ratio by Gender --- p.57Chapter 4.4.2 --- Diseased Middle Cerebral Artery --- p.61Chapter 4.4.3 --- Characteristics between subjects with Normal TCD result and Abnormal TCD result in the MCA status --- p.62Chapter 4.4.3.1 --- Age --- p.64Chapter 4.4.3.2 --- Gender --- p.67Chapter 4.4.3.3 --- "Medical History of HT, DM, Hyperlipidemia, IHD, Retinopathy and Albuminuria" --- p.67Chapter 4.4.3.4 --- Social habit in cigarette smoking --- p.68Chapter 4.4.3.5 --- Body Mass Index and Waist-to-Hip Ratio --- p.71Chapter 4.4.3.6 --- "Other Measurements - on Blood Pressure, Fasting Plasma Glucose, HbAlc, Lipid profiles and Fibrinogen" --- p.79Chapter 4.4.4 --- Unadjusted Odds Ratio --- p.84Chapter 4.4.4.1 --- By contingency table method --- p.84Chapter 4.4.4.2 --- By logistic regression model --- p.86Chapter 4.4.5 --- Adjusted Odds Ratio --- p.92Chapter 4.4.5.1 --- Entering all explanatory variables: --- p.92Chapter 4.4.5.2 --- Using Forward and Backward Stepwise methods with the probability for entry of 0.05 and probability for removal of 0.10: --- p.95Chapter 4.4.5.3 --- Applying the Model-Building Strategy: --- p.100Chapter 4.4.6 --- Comparing the final fitted multiple logistic regression models made by the three approaches ： --- p.103Chapter 4.4.7 --- Probability and Odds derived from the logistic regression model --- p.110Chapter 4.4.8 --- Relationship between the diseased MCA and the number of significant risk indicators that the subjects associated with..… --- p.112Chapter 4.4.8.1 --- Logistic regression analysis on number of risk indicators associated with the MCA status --- p.115Chapter 4.5 --- Discussion --- p.118Chapter 4.5.1 --- Research Design --- p.118Chapter 4.5.1.1 --- Advantage --- p.118Chapter 4.5.1.2 --- Disadvantage --- p.118Chapter 4.5.2 --- Sampling --- p.119Chapter 4.5.3 --- Data collected and Outcome variable classified --- p.119Chapter 4.5.3.1 --- Medical Record - Patients Characteristics --- p.119Chapter 4.5.3.2 --- Transcranial Doppler - Middle Cerebral Artery status --- p.120Chapter 4.5.4 --- Statistical Analyses --- p.121Chapter 4.5.4.1 --- Odds Ratio --- p.121Chapter 4.5.4.2 --- Logistic Regression Model --- p.122Chapter 4.5.4.3 --- Sources of Error --- p.123Chapter 4.5.5 --- Result --- p.125Chapter 4.5.5.1 --- Prevalence --- p.125Chapter 4.5.5.2 --- Risk indicators --- p.126Chapter CHAPTER FIVE --- "POPULATION-BASED CROSS-SECTIONAL SURVEY IN A RURAL VILLAGE OF HENAN, PEOPLE'S REPUBLIC OF CHINA" --- p.134Chapter 5.1 --- Background & Purpose --- p.134Chapter 5.2 --- Methods --- p.135Chapter 5.2.1 --- Defining the Population --- p.135Chapter 5.2.2 --- Procedures --- p.135Chapter 5.2.2.1 --- Standardized Screening Form --- p.136Chapter 5.2.2.2 --- Transcranial Doppler Examination --- p.137Chapter 5.2.3 --- Defining the Risk Factors --- p.137Chapter 5.3 --- Statistical Analyses --- p.140Chapter 5.3.1 --- Research Design --- p.141Chapter 5.3.2 --- Descriptive Summary --- p.141Chapter 5.3.2.1 --- Cross-tabulated between Gender --- p.141Chapter 5.3.2.2 --- Cross-tabulated between With & Without intracranial large artery stenosis --- p.142Chapter 5.3.3 --- Measures for Association --- p.143Chapter 5.3.3.1 --- Univariate analysis --- p.143Chapter 5.3.3.2 --- Multivariate analysis --- p.143Chapter 5.3.4 --- Modeling the Risks --- p.144Chapter 5.3.5 --- Influence of the number of associated risk factors on the prevalence of intracranial large artery stenosis --- p.144Chapter 5.4 --- Result --- p.145Chapter 5.4.1 --- Baseline characteristics of all examined villagers by Gender --- p.145Chapter 5.4.1.1 --- Age by Gender --- p.147Chapter 5.4.1.2 --- "Medical History of HT, DM and Heart disease by Gender" --- p.149Chapter 5.4.1.3 --- Social habit in Cigarette smoking and Alcoholic drinking by Gender --- p.149Chapter 5.4.1.4 --- "Family History of HT, DM, Stroke and Heart disease by Gender" --- p.149Chapter 5.4.1.5 --- Body Mass Index and Waist-to-Hip Ratio by Gender --- p.150Chapter 5.4.2 --- Distribution of the Diseased intracranial artery --- p.154Chapter 5.4.3 --- Characteristics between subjects with and without intracranial large artery stenosis --- p.155Chapter 5.4.3.1 --- Age --- p.157Chapter 5.4.3.2 --- Gender --- p.158Chapter 5.4.3.3 --- "Medical History of HT, DM and Heart disease" --- p.158Chapter 5.4.3.4 --- Social habit in cigarette smoking and alcohol drinking --- p.158Chapter 5.4.3.5 --- "Family History of HT, DM, Stroke and Heart Disease" --- p.159Chapter 5.4.3.6 --- Body Mass Index and Waist-to-Hip Ratio --- p.160Chapter 5.4.3.7 --- Other Measurements - on BP and Urine Glucose --- p.163Chapter 5.4.4 --- Unadjusted Odds Ratio --- p.165Chapter 5.4.4.1 --- By contingency table method --- p.165Chapter 5.4.4.2 --- By logistic regression model --- p.166Chapter 5.4.5 --- Adjusted Odds Ratio --- p.172Chapter 5.4.5.1 --- Entering all explanatory variables: --- p.172Chapter 5.4.5.2 --- Using the Stepwise methods available with the probability for entry is 0.05 and 0.10 for removal: --- p.175Chapter 5.4.5.3 --- Applying the Model-Building Strategy: --- p.180Chapter 5.4.6 --- Comparing the final multiple logistic regression models by the three approaches： --- p.182Chapter 5.4.7 --- Probability and Odds derived from the logistic regression model --- p.189Chapter 5.4.8 --- Relationship between the transcranial Doppler result on Intracranial large artery and the number of significant risk indicators that the subjects associated with --- p.190Chapter 5.4.8.1 --- Logistic Regression Model --- p.192Chapter 5.5 --- Discussion --- p.196Chapter 5.5.1 --- Research Design --- p.196Chapter 5.5.1.1 --- Advantage --- p.196Chapter 5.5.1.2 --- Disadvantage --- p.196Chapter 5.5.2 --- Sampling --- p.197Chapter 5.5.3 --- Data collected and the Outcome variable classified --- p.197Chapter 5.5.3.1 --- Self-Reported - Subjects Characteristics --- p.197Chapter 5.5.3.2 --- Transcranial Doppler - Intracranial Large Artery status --- p.198Chapter 5.5.4 --- Statistical Methods --- p.199Chapter 5.5.4.1 --- Odds Ratio --- p.199Chapter 5.5.4.2 --- Logistic Regression --- p.199Chapter 5.5.4.3 --- Sources of Error --- p.199Chapter 5.5.5 --- Result --- p.200Chapter 5.5.5.1 --- Prevalence --- p.200Chapter 5.5.5.2 --- Risk Indicators --- p.201Chapter CHAPTER SIX --- CONCLUSION --- p.204Chapter 6.1 --- The Clinic-based study of diseased middle cerebral artery among asymptomatic hong kong chinese --- p.204Chapter 6.2 --- The Population-base study of intracranial large artery stenosis among mid-aged & above chinese in rural china --- p.205REFERENCESAPPENDIXAppendix I Neuroimaging - Transcranial Doppler UltrasonographyAppendix II Statistical Methods"Appendix III (a) Standardized TCD report form used in PWH, Hong Kong (b) Standardized Screening Form used In Yuzhou, China"Appendix IV The ICD 9th Revision - Disease of the Circulatory System"Appendix V Prospective Hospital-Based study in Asia, AASAP (a) Standardized Data Collection From used in AASAP"Appendix VI Contributed in published paper

Engineering handbook

1998 handbook for the faculty of Engineerin

Engineering handbook

1998 handbook for the faculty of Engineerin