Shear wave echocardiography

In this thesis we demonstrate that the assessment of the diastolic function of the left ventricle withclassical echocardiography remain

Characterising Shape Variation in the Human Right Ventricle Using Statistical Shape Analysis: Preliminary Outcomes and Potential for Predicting Hypertension in a Clinical Setting

Variations in the shape of the human right ventricle (RV) have previously been shown to be predictive of heart function and long term prognosis in Pulmonary Hypertension (PH), a deadly disease characterised by high blood pressure in the pulmonary arteries. The extent to which ventricular shape is also affected by non-pathological features such as sex, body mass index (BMI) and age is explored in this thesis. If fundamental differences in the shape of a structurally normal RV exist, these might also impact the success of a predictive model. This thesis evaluates the extent to which non-pathological features affect the shape of the RV and determines the best ways, in terms of procedure and analysis, to adapt the model to consistently predict PH. It also identifies areas where the statistical shape analysis procedure is robust, and considers the extent to which specific, non-pathological, characteristics impact the diagnostic potential of the statistical shape model. Finally, recommendations are made on next steps in the development of a classification procedure for PH. The dataset was composed of clinically-obtained, cardiovascular magnetic resonance images (CMR) from two independent sources; The University of Pittsburgh Medical Center and Newcastle University. Shape change is assessed using a 3D statistical shape analysis technique, which topologically maps heart meshes through an harmonic mapping approach to create a unique shape function for each shape. Proper Orthogonal Decomposition (POD) was applied to the complete set of shape functions in order to determine and rank a set of shape features (i.e. modes and corresponding coefficients from the decomposition). MRI scanning protocol produced the most significant difference in shape; a shape mode associated with detail at the RV apex and ventricular length from apex to base strongly correlated with the MRI sequence used to record each subject. Qualitatively, a protocol which skipped slices produced a shorter RV with less detail at the apex. Decomposition of sex, age and BMI also derives unique RV shape descriptors which correspond to anatomically meaningful features. The shape features are shown to be able to predict presence of PH. The predictive model can be improved by including BMI as a factor, but these improvements are mainly concentrated in identification of healthy subjects

Echocardiography

The book "Echocardiography - In Specific Diseases" brings together contributions from well- known researchers from around the world, some of them specialized in imaging science in their clinical orientation, but also representatives from academic medical centers. Each chapter is structured and written to be accessible to those with a basic knowledge of echocardiography but also to be stimulating and informative to experts and researchers in the field of echocardiography. This book is primarily aimed at cardiology fellows during their basic echocardiography rotation, fellows of internal medicine, radiology and emergency medicine, but also experts in echocardiography. During the past few decades technological advancements in echocardiography have been developing rapidly, leading to improved echocardiographic imaging using new techniques. The authors of this book tried to explain the role of echocardiography in several special pathologies, which the readers may find in different chapters of the book

Three-dimensional in-vivo intra-cardiac vortex flow from 4D Flow MRI : quantification, automatic identification and association with energy loss

Despite one might intuitively think that blood inflows inside the human heart in a straight path, direct imaging of cardiac blood flow showed that, actually, cardiac blood inflows in a swirling motion forming what is called vortex flow pattern. In fact, blood inflow forms a pair of counter-rotating vortices distal to the mitral valve inside the heart. In three-dimensions, this pair of vortices forms a ring-like vortex: a vortex ring. This thesis revealed the three-dimensional form and time evolution of such vortex ring flow in the human heart in health and disease. This was achieved using cutting-edge 4D Flow MRI in-vivo imaging technology and developments of novel advanced methods integrating image and applied fluid mechanics concepts enabling characterization, quantification and automatic identification of heart’s vortex flow. In this thesis, a novel framework was developed allowing for the first noninvasive assessment of intra-cardiac viscous energy loss. This thesis showed that alteration in cardiac vortex ring flow properties, due to heart disease, can result in 2-4 fold increase in viscous energy loss in the left ventricle. As such, heart’s vortex flow could be an efficient mechanism of energy loss minimization in healthy hearts and might act as a biomarker of cardiac health.This research is supported by the Dutch Technology Foundation STW, which is part of the Netherlands Organisation for Scientific Research (NWO) and partly funded by the Ministry of Economic Affairs (project number 11626).LUMC / Geneeskund

Takotsubo stress cardiomyopathy and different types of stress

Myocardial infarction with normal coronary angiography (MINCA) is an important subgroup of myocardial infarction for which the prevalence, underlying pathophysiology, prognosis and optimal management are still largely unknown. Interest in and awareness of MINCA has increased in recent years due to the frequent use of coronary angiography, the description of Takotsubo stress cardiomyopathy (TSC) and new sensitive troponin assays. The purpose of this thesis was to investigate the prevalence and clinical characteristics of MINCA using cardiovascular magnetic resonance (CMR) and particularly to investigate the effect of stress on TSC using Doppler tissue imaging (DTI), heart rate variability (HRV), salivary cortisol (SC) and non-invasive coronary flow reserve (CFR). In Study I, 176 patients with MINCA were screened at five coronary care units in the Stockholm Metropolitan Area. 152 of them were investigated using CMR which showed 67% of the patients as being normal, 19% having signs of myocardial necrosis and 7% the diagnosis was myocarditis in of the patients. The remaining patients were either diagnosed with hypertrophic cardiomyopathy or were undecided. Twenty-two percent of all MINCA with a normal CMR fulfilled the Mayo Clinic criteria for TSC. In Study II, we tested the hypothesis that compared to sex- and age-matched controls TSC patients have an increased vulnerability to stress even after the acute event. Using dobutamine stress echocardiography (DSE) and DTI we investigated the TSC patients approximately 20 months (619 ± 297 days) after the acute event. At rest left ventricular myocardial performance index (LV-MPI) was significantly higher for TSC patients (p=0.01). During stress, however, there were no significant differences between the groups. Study III was in many ways similar to Study II except that mental stress was used instead of dobutamine stress. The study was performed 28 months after the acute event. In addition to DTI, HRV and SC were also studied. During mental stress there were no significant differences between TSC patients and sex- and age-matched controls for DTI, HRV and SC. There was a trend towards less increase in SC after stress in TSC patients compared to controls. A self-estimated acute stress scale (Likert-type scale from 0–6) was 2.8 and 2.6 during mental stress for TSC patients and controls, respectively. During the acute event TSC patients retrospectively estimated their acute stress level at 4.4. In Study IV, dobutamine stress was used to investigate the effect of stress on non-invasive CFR. At low-dose dobutamine, CFR was significantly lower in TSC patients compared to controls (p=0.017). There were no differences in CFR at high-dose dobutamine between the groups. Conclusion: MINCA is more common than previously thought and is associated with a normal CMR. TSC constitutes a substantial part of MINCA. Studies II and III point to a slow recovery for TSC patients measured by DTI but no sign of vulnerability was revealed by dobutamine or mental stress measured by DTI, HRV or SC. We could not confirm that the catecholamine dobutamine induced microvascular dysfunction in TSC patients. However, we found a small but significant difference in CFR at low-dose dobutamine, which implies that the role of microvascular function in TSC needs to be further explored

Shape analysis in shape space

This study aims to classify different deformations based on the shape space concept. A shape space is a quotient space in which each point corresponds to a class of shapes. The shapes of each class are transformed to each other by a transformation group preserving a geometrical property in which we are interested. Therefore, each deformation is a curve on the high dimensional shape space manifold, and one can classify the deformations by comparison of their corresponding deformation curves in shape space. Towards this end, two classification methods are proposed. In the first method, a quasi conformal shape space is constructed based on a novel quasi-conformal metric, which preserves the curvature changes at each vertex during the deformation. Besides, a classification framework is introduced for deformation classification. The results on synthetic and real datasets show the effectiveness of the metric to estimate the intrinsic geometry of the shape space manifold, and its ability to classify and interpolate different deformations. In the second method, we introduce the medial surface shape space which classifies the deformations based on the medial surface and thickness of the shape. This shape space is based on the log map and uses two novel measures, average of the normal vectors and mean of the positions, to determine the distance between each pair of shapes on shape space. We applied these methods to classify the left ventricle deformations. The experimental results shows that the first method can remarkably classify the normal and abnormal subjects but this method cannot spot the location of the abnormality. In contrast, the second method can discriminate healthy subjects from patients with cardiomyopathy, and also can spot the abnormality on the left ventricle, which makes it a valuable assistant tool for diagnostic purposes

Computer-aided detection of wall motion abnormalities in cardiac MRI

With the increasing prevalence and hospitalization rate of ischaemic heart disease, an explosive growth of diagnostic imaging for ischaemia is ongoing. Clinical decision making on revascularization procedures requires reliable viability assessment to assure long-term patient survival and to elevate cost effectiveness of the therapy and treatment. As such, the demand is increasing for a computer-assisted diagnosis (CAD) method for ischaemic heart disease that supports clinicians with an objective analysis of infarct severity, a viability assessment or a prediction of potential functional improvement before performing revascularization. The goal of this thesis was to explore novel mechanisms that can be used for CAD in ischaemic heart disease, particularly through wall motion analysis from cardiac MR images. Existing diagnostic treatment of wall motion analysis from cardiac MR relies on visual wall motion scoring, which suffers from inter- and intra-observer variability. To minimize this variability, the automated method must contain essential knowledge on how the heart contracts normally. This enables automatic quantification of regional abnormal wall motion, detection of segments with contractile reserve and prediction of functional improvement in stress.1. Bontius Stichting inz. Doelfonds beeldverwerking, 2. Foundation Imago, 3. ASCI research school, and 4. Library of the University of Leiden.UBL - phd migration 201

Doctor of Philosophy

dissertationCongenital heart defects are classes of birth defects that affect the structure and function of the heart. These defects are attributed to the abnormal or incomplete development of a fetal heart during the first few weeks following conception. The overall detection rate of congenital heart defects during routine prenatal examination is low. This is attributed to the insufficient number of trained personnel in many local health centers where many cases of congenital heart defects go undetected. This dissertation presents a system to identify congenital heart defects to improve pregnancy outcomes and increase their detection rates. The system was developed and its performance assessed in identifying the presence of ventricular defects (congenital heart defects that affect the size of the ventricles) using four-dimensional fetal chocardiographic images. The designed system consists of three components: 1) a fetal heart location estimation component, 2) a fetal heart chamber segmentation component, and 3) a detection component that detects congenital heart defects from the segmented chambers. The location estimation component is used to isolate a fetal heart in any four-dimensional fetal echocardiographic image. It uses a hybrid region of interest extraction method that is robust to speckle noise degradation inherent in all ultrasound images. The location estimation method's performance was analyzed on 130 four-dimensional fetal echocardiographic images by comparison with manually identified fetal heart region of interest. The location estimation method showed good agreement with the manually identified standard using four quantitative indexes: Jaccard index, Sørenson-Dice index, Sensitivity index and Specificity index. The average values of these indexes were measured at 80.70%, 89.19%, 91.04%, and 99.17%, respectively. The fetal heart chamber segmentation component uses velocity vector field estimates computed on frames contained in a four-dimensional image to identify the fetal heart chambers. The velocity vector fields are computed using a histogram-based optical flow technique which is formulated on local image characteristics to reduces the effect of speckle noise and nonuniform echogenicity on the velocity vector field estimates. Features based on the velocity vector field estimates, voxel brightness/intensity values, and voxel Cartesian coordinate positions were extracted and used with kernel k-means algorithm to identify the individual chambers. The segmentation method's performance was evaluated on 130 images from 31 patients by comparing the segmentation results with manually identified fetal heart chambers. Evaluation was based on the Sørenson-Dice index, the absolute volume difference and the Hausdorff distance, with each resulting in per patient average values of 69.92%, 22.08%, and 2.82 mm, respectively. The detection component uses the volumes of the identified fetal heart chambers to flag the possible occurrence of hypoplastic left heart syndrome, a type of congenital heart defect. An empirical volume threshold defined on the relative ratio of adjacent fetal heart chamber volumes obtained manually is used in the detection process. The performance of the detection procedure was assessed by comparison with a set of images with confirmed diagnosis of hypoplastic left heart syndrome and a control group of normal fetal hearts. Of the 130 images considered 18 of 20 (90%) fetal hearts were correctly detected as having hypoplastic left heart syndrome and 84 of 110 (76.36%) fetal hearts were correctly detected as normal in the control group. The results show that the detection system performs better than the overall detection rate for congenital heart defect which is reported to be between 30% and 60%