Model-based estimation of arterial diameter from X-ray angiograms

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 122-124).by Raymond C. Chan.M.S

Role of computed tomography and magnetic resonance imaging in patients with cardiovascular disease

Background: Although there have been recent advances, cardiovascular disease remains the commonest cause of premature death in the United Kingdom. There is a need to develop safe non-invasive techniques to aid the diagnosis and treatment of patients with cardiovascular disease.Objectives: The aims of this thesis are: (i) to establish whether coronary artery calcification can be measured reproducibly by helical computed tomography; (ii) to establish the effect of lipid lowering therapy on the progression of coronary calcification; (iii) to determine whether multidetector computed tomography can predict graft patency in patients who have undergone coronary artery bypass grafting; and (iv), to investigate the role of magnetic resonance imaging to assess plaque characteristics following acute carotid plaque rupture.Methods: In 16 patients, coronary artery calcification was assessed twice within 4 weeks by helical computed tomography. As part of a randomised controlled trial, patients received atorvastatin 80 mg daily or matching placebo, and had coronary calcification assessed annually. Fifty patients with previous coronary artery bypass surgery who were listed for diagnostic coronary angiography underwent contrast enhanced computed tomography angiography using a 16-slice multidetector computed tomography scanner. Finally, 15 patients with recent symptoms and signs of an acute transient ischaemic attack, amaurosis fugax or stroke underwent magnetic resonance angiography of the carotid arteries using dedicated surface coils. Plaque volume, regional plaque densities and neovascularisation were determined before and after gadolinium enhancement.Results: Quantification of coronary artery calcification demonstrated good reproducibility in patients with scores > 100 AU. Despite reducing systemic inflammation and halving serum low-density lipoprotein cholesterol concentrations, atorvastatin therapy did not affect the rate of progression of coronary artery calcification. Computed tomography angiography was found to be highly specific for the detection of graft patency. Assessment of plaque characteristics by magnetic resonance scanning in patients with recent acute carotid plaque was feasible and reproducible.Conclusions: Coronary artery calcium scores can be determined in a reproducible manner. Although they correlate well with the presence of atherosclerosis and predict future coronary risk. there is little role for monitoring progression of coronary artery calcification in order to assess the response to lipid lowering therapy. Computed tomography can be used reliably to predict graft patency in patients who have undergone coronary artery bypass grafting, and is an acceptable non-invasive alternative to invasive coronary angiography. Magnetic resonance imaging techniques ' can be employed in a feasible, timely and reproducible manner to detect plaque characteristics associated with acute atherothrombotic disease

Cardiovascular Magnetic Resonance Imaging for the Investigation of Patients with Coronary Heart Disease

Objectives To evaluate the role of stress perfusion cardiovascular magnetic resonance (CMR) in the investigation of stable coronary artery disease (CAD). Background Coronary artery disease remains the biggest cause of morbidity and mortality. The multi-parametric CMR examination is established as an investigative strategy for the investigation of CAD. Methods Study 1 & 2: Patients with stable coronary artery disease underwent a multi-parametric CMR protocol assessing 4 components: i) left ventricular function; ii) myocardial perfusion; iii) viability (late gadolinium enhancement (LGE)) and iv) coronary magnetic resonance angiography (MRA). The diagnostic accuracy of the individual components were assessed. The ischaemic burden of stress CMR Vs. Single Photon Emission Computed Tomography (SPECT) was determined. Study 3: Volunteers and patients were scanned with perfusion sequence which adapts the spatial resolution to the available scanning time and field-of-view. Study 4: A multi-centre pragmatic randomised controlled trial of patients with stable angina comparing CMR guided-care Vs. SPECT guided-care Vs. National Institute of Health and Care Excellence guided-care. Results Study 1 demonstrated the stress perfusion component of the multi-parametric CMR exam was the single most important component for overall diagnostic accuracy. However, the full combined multi-parametric protocol was the optimal approach for disease rule-out, and the LGE component best for rule-in. Study 2 showed that there was reasonable agreement of the summed stress scores between CMR and SPECT (a well established investigation with significant amounts of prognostic data). In study 3, a perfusion pulse sequence which automatically adapts the acquisition sequence to the available scanning time results in spatial resolution improvement and reduction in dark rim artefact. Finally in study 4 in patients with suspected angina using CMR as an initial investigative strategy produced a significantly lower probability of unnecessary angiography compared to NICE guidance. There were similar rates of CAD detection were comparable suggesting no penalty for using functional imaging as a gatekeeper for angiography. Conclusion CMR has high diagnostic accuracy for the detection of coronary artery disease; with similar detection of ischaemic burden to established tests and can be used safely and effectively as a gate keeper to invasive coronary angiography

Computer integrated system: medical imaging & visualization

The intent of this book’s conception is to present research work using a user centered design approach. Due to space constraints, the story of the journey, included in this book is relatively brief. However we believe that it manages to adequately represent the story of the journey, from its humble beginnings in 2008 to the point where it visualizes future trends amongst both researchers and practitioners across the Computer Science and Medical disciplines. This book aims not only to present a representative sampling of real-world collaboration between said disciplines but also to provide insights into the different aspects related to the use of real-world Computer Assisted Medical applications. Readers and potential clients should find the information particularly useful in analyzing the benefits of collaboration between these two fields, the products in and of their institutions. The work discussed here is a compilation of the work of several PhD students under my supervision, who have since graduated and produced several publications either in journals or proceedings of conferences. As their work has been published, this book will be more focused on the research methodology based on medical technology used in their research. The research work presented in this book partially encompasses the work under the MOA for collaborative Research and Development in the field of Computer Assisted Surgery and Diagnostics pertaining to Thoracic and Cardiovascular Diseases between UPM, UKM and IJN, spanning five years beginning from 15 Feb 2013

Coronary Artery Segmentation and Motion Modelling

Conventional coronary artery bypass surgery requires invasive sternotomy and the use of a cardiopulmonary bypass, which leads to long recovery period and has high infectious potential. Totally endoscopic coronary artery bypass (TECAB) surgery based on image guided robotic surgical approaches have been developed to allow the clinicians to conduct the bypass surgery off-pump with only three pin holes incisions in the chest cavity, through which two robotic arms and one stereo endoscopic camera are inserted. However, the restricted field of view of the stereo endoscopic images leads to possible vessel misidentification and coronary artery mis-localization. This results in 20-30% conversion rates from TECAB surgery to the conventional approach. We have constructed patient-specific 3D + time coronary artery and left ventricle motion models from preoperative 4D Computed Tomography Angiography (CTA) scans. Through temporally and spatially aligning this model with the intraoperative endoscopic views of the patient's beating heart, this work assists the surgeon to identify and locate the correct coronaries during the TECAB precedures. Thus this work has the prospect of reducing the conversion rate from TECAB to conventional coronary bypass procedures. This thesis mainly focus on designing segmentation and motion tracking methods of the coronary arteries in order to build pre-operative patient-specific motion models. Various vessel centreline extraction and lumen segmentation algorithms are presented, including intensity based approaches, geometric model matching method and morphology-based method. A probabilistic atlas of the coronary arteries is formed from a group of subjects to facilitate the vascular segmentation and registration procedures. Non-rigid registration framework based on a free-form deformation model and multi-level multi-channel large deformation diffeomorphic metric mapping are proposed to track the coronary motion. The methods are applied to 4D CTA images acquired from various groups of patients and quantitatively evaluated

Automatic detection of the carotid artery boundary on cross-sectional MR image sequences using a circle model guided dynamic programming

Systematic aerobe training has positive effects on the compliance of dedicated arterial walls. The adaptations of the arterial structure and function are associated with the blood flow-induced changes of the wall shear stress which induced vascular remodelling via nitric oxide delivered from the endothelial cell. In order to assess functional changes of the common carotid artery over time in these processes, a precise measurement technique is necessary. Before this study, a reliable, precise, and quick method to perform this work is not present

Heart failure: re-evaluating causes and definitions and the value of routine cardiac magnetic resonance (CMR) imaging

Objective To differentiate the demographics and imaging characteristics of a heart failure population using a comprehensive echocardiographic protocol and routine CMR imaging, and to assess the clinical value of routine CMR in this population. Methods A novel comprehensive diagnostic pathway for heart failure was prospectively applied to 319 new patients attending the Darlington and Bishop Auckland heart failure clinic between May 2013 and July 2014. All had a full clinical assessment and an initial basic clinical transthoracic echo performed. Those patients given a diagnosis of heart failure went on to have routine CMR imaging as well as a more detailed echo scan incorporating a variety of systolic and diastolic measurements. Retrospectively, a cohort of 116 patients with left ventricular systolic impairment, that had both CMR and invasive coronary angiography, were analysed to determine the ability of late gadolinium enhancement (LGE) CMR to predict prognostic coronary artery disease. Main results 1. Heart failure with reduced ejection fraction (HFREF) accounted for the cause of heart failure in 73% of cases whereas heart failure with preserved ejection fraction (HFPEF) accounted for only 14% of cases. 2. Incorporating CMR into the routine assessment of newly diagnosed heart failure patients changed the diagnosis in 22% of cases (14% of cases for those who had an echo performed on the same day). 3. CMR left ventricular ejection fraction (LVEF) averages 3.9% units higher than Simpson’s Biplane LVEF with echo. 4. Regional wall motion score (RWMS) equations were inferior to a Simpson’s Biplane assessment of LVEF by echo and cannot be advocated for routine clinical use. 5. The presence of subendocardial LGE on CMR demonstrated infarcts in 42% of those with HFREF, 20% of those with HFPEF, and 40% of those with heart failure with no major structural disease (HFNMSD). 6. The absence of subendocardial LGE excluded prognostic coronary disease in 100% of cases. 7. LGE in a non subendocardial distribution was prevalent in both the HFREF and HFPEF community with a greater average burden in the HFPEF group. 8. E/e’ and left atrial volume index (LAVI) were the most helpful echo measures for a positive diagnosis of HFPEF and could be measured in over 90% of cases. 9. Systolic dysfunction out with reduced ejection fraction is present in 76% of the HFPEF cohort. Conclusion Heart failure with preserved ejection fraction (HFPEF) is not the epidemic previous literature would have us believe. It is over-diagnosed in current practice due to lax definitions and inappropriately low left ventricular ejection fraction (LVEF) cut-offs. CMR has a substantial impact on the diagnostic profile of the heart failure population. It revokes the diagnosis of HFREF to a greater extent than is accounted for by the temporal improvement in LVEF, even when taking into account method specific LVEF thresholds. CMR with LGE has additive value for identifying infarcts in a sizeable number of patients for whom there is no suspicion of ischaemic heart disease (IHD), and raising the novel concept that ischaemia may account for symptoms in many of those with HFNMSD. It also demonstrates an impressive ability to exclude prognostic coronary disease. Additionally, LGE in a non subendocardial distribution establishes aetiology including myocarditis and sarcoidosis that would not be detected with echo alone. The diagnosis of heart failure with preserved ejection fraction is not standardised and all current protocols are deficient. The cause and mechanism of this condition remains unclear and this study helped clarify the contribution of systolic versus diastolic dysfunction versus simply the presence of atrial fibrillation. Key diagnostic parameters were identified for routine clinical use and CMR LGE imaging demonstrating a greater average burden of non subendocardial LGE may support the postulated fibrotic infiltrative mechanism of pathology in this group

A Hybrid Energy Model for Region Based Curve Evolution - Application to CTA Coronary Segmentation

Background and Objective: State-of-the-art medical imaging techniques have enabled non-invasive imaging of the internal organs. However, high volumes of imaging data make manual interpretation and delineation of abnormalities cumbersome for clinicians. These challenges have driven intensive research into efficient medical image segmentation. In this work, we propose a hybrid region-based energy formulation for effective segmentation in computed tomography angiography (CTA) imagery. Methods: The proposed hybrid energy couples an intensity-based local term with an efficient discontinuity-based global model of the image for optimal segmentation. The segmentation is achieved using a level set formulation due to the computational robustness. After validating the statistical significance of the hybrid energy, we applied the proposed model to solve an important clinical problem of 3D coronary segmentation. An improved seed detection method is used to initialize the level set evolution. Moreover, we employed an auto-correction feature that captures the emerging peripheries during the curve evolution for completeness of the coronary tree. Results: We evaluated the segmentation accuracy of the proposed energy model against the existing techniques in two stages. Qualitative and quantitative results demonstrate the effectiveness of the proposed framework with a consistent mean sensitivity and specificity measures of 80% across the CTA data. Moreover, a high degree of agreement with respect to the inter-observer differences justifies the generalization of the proposed method. Conclusions: The proposed method is effective to segment the coronary tree from the CTA volume based on hybrid image based energy, which can improve the clinicians ability to detect arterial abnormalities

Coronary spiral CT

This dissertation describes the use and clinical potential of ECG gated multislice spiral computed tomography in patients with coronary artery disease. First the use of other non invasive cardiac imaging, i.e. the previously mentioned electron beam CT and magnetic resonance imaging is reviewed (chapter 2.1). Part 3 contains studies related to the characteristics of multislice spiral CT for the imaging of the heart and coronary arteries, and the diagnostic potential of ECG gated spiral CT coronary angiography to detect and visualize obstructive coronary artery disease in symptomatic patients, using conventional coronary angiography as the standard of reference. Part 4 is focussed on the feasibility and characteristics of coronary wall imaging by CT, including the assessment of non calcified atherosclerotic plaque material. The usefulness of contrast enhanced multislice spiral CT in symptomatic patients who previously underwent coronary artery bypass grafting and percutaneous coronary intervention with stent implantation is discussed in part 5. Finally, the first results with the latest generation 16 slice computed tomography scanners and patient preparation with ~ receptor blockers are described in part 6, including a review and future outlook on the continuing development and clinical use of non invasive coronary angiography with spiral computed tomography