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

Flow pattern analysis for magnetic resonance velocity imaging

Blood flow in the heart is highly complex. Although blood flow patterns have been investigated by both computational modelling and invasive/non-invasive imaging techniques, their evolution and intrinsic connection with cardiovascular disease has yet to be explored. Magnetic resonance (MR) velocity imaging provides a comprehensive distribution of multi-directional in vivo flow distribution so that detailed quantitative analysis of flow patterns is now possible. However, direct visualisation or quantification of vector fields is of little clinical use, especially for inter-subject or serial comparison of changes in flow patterns due to the progression of the disease or in response to therapeutic measures. In order to achieve a comprehensive and integrated description of flow in health and disease, it is necessary to characterise and model both normal and abnormal flows and their effects. To accommodate the diversity of flow patterns in relation to morphological and functional changes, we have described in this thesis an approach of detecting salient topological features prior to analytical assessment of dynamical indices of the flow patterns. To improve the accuracy of quantitative analysis of the evolution of topological flow features, it is essential to restore the original flow fields so that critical points associated with salient flow features can be more reliably detected. We propose a novel framework for the restoration, abstraction, extraction and tracking of flow features such that their dynamic indices can be accurately tracked and quantified. The restoration method is formulated as a constrained optimisation problem to remove the effects of noise and to improve the consistency of the MR velocity data. A computational scheme is derived from the First Order Lagrangian Method for solving the optimisation problem. After restoration, flow abstraction is applied to partition the entire flow field into clusters, each of which is represented by a local linear expansion of its velocity components. This process not only greatly reduces the amount of data required to encode the velocity distribution but also permits an analytical representation of the flow field from which critical points associated with salient flow features can be accurately extracted. After the critical points are extracted, phase portrait theory can be applied to separate them into attracting/repelling focuses, attracting/repelling nodes, planar vortex, or saddle. In this thesis, we have focused on vortical flow features formed in diastole. To track the movement of the vortices within a cardiac cycle, a tracking algorithm based on relaxation labelling is employed. The constraints and parameters used in the tracking algorithm are designed using the characteristics of the vortices. The proposed framework is validated with both simulated and in vivo data acquired from patients with sequential MR examination following myocardial infarction. The main contribution of the thesis is in the new vector field restoration and flow feature abstraction method proposed. They allow the accurate tracking and quantification of dynamic indices associated with salient features so that inter- and intra-subject comparisons can be more easily made. This provides further insight into the evolution of blood flow patterns and permits the establishment of links between blood flow patterns and localised genesis and progression of cardiovascular disease.Open acces

Clinical applications of non-invasive imaging techniques in suspected coronary artery disease and in acute myocardial infarction

Non-invasive cardiac imaging modalities play a crucial role in the diagnostic process and clinical management of patients without known coronary artery disease and patients with acute myocardial infarction. The first part of the thesis discusses the use of non-invasive imaging modalities (including coronary artery calcium scoring, multi-slice computed tomography coronary angiography, conventional two-dimensional echocardiography and speckle-tracking echocardiography) for the diagnosis and risk stratification of patients with suspected coronary artery disease. The second part of the thesis discusses the diagnostic and prognostic value of novel echocardiographic techniques (including contrast echocardiography, myocardial deformation imaging, and three-dimensional echocardiography) in patients admitted with acute myocardial infarction.UBL - phd migration 201

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

Multislice computed tomography coronary angiography

__Abstract__ Computed Tomography (CT) imaging is also known as "CAT scanning" (Computed Axia

Utility value of tissue doppler imaging during dobutamine stress in differentiating ischemic from nonischemic dilated cardiomyopathy.

Differentiating ischemic from nonischemic cardiomyopathy poses a particular problem, but this is important prognostically and therapeutically. Patients with ischemic cardiomyopathy have worse prognosis than the patients with idiopathic dilated cardiomyopathy. Joseph et al, in 1983 have demonstrated that in patients with severe chronic left ventricular failure, mortality rate in patients with coronary artery was 46% and 69% at 1 and 2 years, respectively compared with 23% and 48% at 1 and 2 years in those with idiopathic dilated cardiomyopathy. In 1997, Bradley and colleagues also have shown ischemic etiology is a significant independent predictor of mortality in patients with cardiomyopahy. Therapeutically also it is important to distinguish between ischemic and nonischemic cardiomyopathy because the diagnosis influences the management. Antiplatelets and lipid lowering therapy are important in management of patients with cardiomyopathy of ischemic etiology. Revascularisation in patients with low ejection fraction and significant coronary artery disease is strongly associated with improved survival and should be considered in all patients with ischemic cardiomyopathy and proven hibernation. Moreover ischemic cardiomyopathy may not respond to medical therapy as favorably as patients with nonischemic cardiomyopathy. Differentiating ischemic from nonischemic cardiomyopathy clinically is not always easy. Although ischemic cardiomyopthy is generally a late consequence of clinically established coronary artery disease, sometimes the clinical course is really occult and indistinguishable from idiopathic cardiomyopathy. An ischemic cause is probable in patients with history of definite or documented prior myocardial infarction or left ventricular aneurysm in echocardiogram. However, some patients with ischemic cardiomyopathy have neither history nor electrocardiographic evidence of myocardial infarction, never complaint of chest pain and shows diffuse rather than regional hypocontractility. Conversely many patients with idiopathic dilated cardiomyopathy report frequent episodes of chestpain and have electrocardiographic evidence of myocardial infarction. CONCLUSIONS : (1) Tissue Doppler Imaging during dobutamine stress is a simple, and effective non-invasive modality in differentiating ischemic from nonischemic dilated cardiomyopathy. (2) Blunted response to dobutamine identifies ischemic cardiomyopathy. (3) Tissue Doppler Imaging was especially useful in patients with left bundle branch block and dilated cardiomyopathy. (4) Tissue Doppler Imaging findings correlate well with coronary angiogram

Characterization of 3-D coronary tree motion from MSCT angiography.

International audienceThis paper describes a method for the characterization of coronary artery motion using multislice computed tomography (MSCT) volume sequences. Coronary trees are first extracted by a spatial vessel tracking method in each volume of MSCT sequence. A point-based matching algorithm, with feature landmarks constraint, is then applied to match the 3-D extracted centerlines between two consecutive instants over a complete cardiac cycle. The transformation functions and correspondence matrices are estimated simultaneously, and allow deformable fitting of the vessels over the volume series. Either point-based or branch-based motion features can be derived. Experiments have been conducted in order to evaluate the performance of the method with a matching error analysis

Utility value of tissue doppler imaging during dobutamine stress in differentiating ischemic from nonischemic dilated cardiomyopathy.

Differentiating ischemic from nonischemic cardiomyopathy poses a particular problem, but this is important prognostically and therapeutically. Patients with ischemic cardiomyopathy have worse prognosis than the patients with idiopathic dilated cardiomyopathy. Joseph et al, in 1983 have demonstrated that in patients with severe chronic left ventricular failure, mortality rate in patients with coronary artery was 46% and 69% at 1 and 2 years, respectively compared with 23% and 48% at 1 and 2 years in those with idiopathic dilated cardiomyopathy. In 1997, Bradley and colleagues also have shown ischemic etiology is a significant independent predictor of mortality in patients with cardiomyopahy. Therapeutically also it is important to distinguish between ischemic and nonischemic cardiomyopathy because the diagnosis influences the management. Antiplatelets and lipid lowering therapy are important in management of patients with cardiomyopathy of ischemic etiology. Revascularisation in patients with low ejection fraction and significant coronary artery disease is strongly associated with improved survival and should be considered in all patients with ischemic cardiomyopathy and proven hibernation. Moreover ischemic cardiomyopathy may not respond to medical therapy as favorably as patients with nonischemic cardiomyopathy. Differentiating ischemic from nonischemic cardiomyopathy clinically is not always easy. Although ischemic cardiomyopthy is generally a late consequence of clinically established coronary artery disease, sometimes the clinical course is really occult and indistinguishable from idiopathic cardiomyopathy. An ischemic cause is probable in patients with history of definite or documented prior myocardial infarction or left ventricular aneurysm in echocardiogram. However, some patients with ischemic cardiomyopathy have neither history nor electrocardiographic evidence of myocardial infarction, never complaint of chest pain and shows diffuse rather than regional hypocontractility. Conversely many patients with idiopathic dilated cardiomyopathy report frequent episodes of chestpain and have electrocardiographic evidence of myocardial infarction. CONCLUSIONS : (1) Tissue Doppler Imaging during dobutamine stress is a simple, and effective non-invasive modality in differentiating ischemic from nonischemic dilated cardiomyopathy. (2) Blunted response to dobutamine identifies ischemic cardiomyopathy. (3) Tissue Doppler Imaging was especially useful in patients with left bundle branch block and dilated cardiomyopathy. (4) Tissue Doppler Imaging findings correlate well with coronary angiogram