Cardiac Motion Analysis Based on Optical Flow on Real-Time Three-Dimensional Ultrasound Data

With relatively high frame rates and the ability to acquire volume data sets with a stationary transducer, 3D ultrasound systems, based on matrix phased array transducers, provide valuable three-dimensional information, from which quantitative measures of cardiac function can be extracted. Such analyses require segmentation and visual tracking of the left ventricular endocardial border. Due to the large size of the volumetric data sets, manual tracing of the endocardial border is tedious and impractical for clinical applications. Therefore the development of automatic methods for tracking three-dimensional endocardial motion is essential. In this study, we evaluate a four-dimensional optical flow motion tracking algorithm to determine its capability to follow the endocardial border in three dimensional ultrasound data through time. The four-dimensional optical flow method was implemented using three-dimensional correlation. We tested the algorithm on an experimental open-chest dog data set and a clinical data set acquired with a Philips' iE33 three-dimensional ultrasound machine. Initialized with left ventricular endocardial data points obtained from manual tracing at end-diastole, the algorithm automatically tracked these points frame by frame through the whole cardiac cycle. Finite element surfaces were fitted through the data points obtained by both optical flow tracking and manual tracing by an experienced observer for quantitative comparison of the results. Parameterization of the finite element surfaces was performed and maps displaying relative differences between the manual and semi-automatic methods were compared. The results showed good consistency with less than 10% difference between manual tracing and optical flow estimation on 73% of the entire surface. In addition, the optical flow motion tracking algorithm greatly reduced processing time (about 94% reduction compared to human involvement per cardiac cycle) for analyzing cardiac function in three-dimensional ultrasound data sets. A displacement field was computed from the optical flow output, and a framework for computation of dynamic cardiac information is introduced. The method was applied to a clinical data set from a heart transplant patient and dynamic measurements agreed with known physiology as well as experimental results

Perinatal changes in fetal ventricular geometry, myocardial performance and cardiac function in normal term pregnancies.

Background: The fetal heart at term is exposed to an increase in hemodynamic work as a consequence of fetal growth, increased circulating volume and alteration in loading patterns due to maturational changes in fetoplacental circulation. The extent to which these cardiovascular changes influence the human fetal and neonatal cardiac adaptation has not been fully elucidated. The aim of this study was to evaluate perinatal cardiovascular changes in ventricular geometry and myocardial performance in normal term fetuses. Methods: Prospective study of 108 uncomplicated pregnancies delivering at term. M-mode, twodimensional (2D) or B-mode, pulsed wave (PW) Doppler, PW tissue Doppler and 2D speckle tracking imaging were performed a few days before, and within 24 hours of birth. Results: Analysis of paired fetal and neonatal echoes demonstrated significant perinatal changes (p<0.0001 for all) in right ventricular (RV) and left ventricular (LV) geometry (RV/LV enddiastolic dimension ratio: 1.2 vs. 0.8, RV sphericity index: 0.53 vs. 0.40, LV sphericity index: 0.46 vs. 0.49). There were corresponding significant (p<0.001 for all) perinatal changes in global myocardial performance: LV myocardial performance index (MPI’): 0.60 vs. 0.47, RV MPI’: 0.61 vs. 0.42; systolic function: LV longitudinal systolic strain rate: -1.4 /s vs. -1.0 /s, RV longitudinal systolic strain rate: -1.5 /s vs. -1.0 /s; RV systolic annular peak velocity (S’): 5.3 cm/s vs. 6.5 cm/s; and diastolic function: LV diastolic annular peak velocity ratio (E’/A’): 0.8 vs.1.1. Conclusion: The findings support the concept that the perinatal period is associated with major changes in fetal ventricular geometry and cardiac function in response to significant alterations in loading conditions. Improved knowledge of perinatal cardiac changes in normal fetuses could facilitate better understanding of cardiac adaptation in normal and pathological pregnancies

Automated Analysis of 3D Stress Echocardiography

__Abstract__ The human circulatory system consists of the heart, blood, arteries, veins and capillaries. The heart is the muscular organ which pumps the blood through the human body (Fig. 1.1,1.2). Deoxygenated blood flows through the right atrium into the right ventricle, which pumps the blood into the pulmonary arteries. The blood is carried to the lungs, where it passes through a capillary network that enables the release of carbon dioxide and the uptake of oxygen. Oxygenated blood then returns to the heart via the pulmonary veins and flows from the left atrium into the left ventricle. The left ventricle then pumps the blood through the aorta, the major artery which supplies blood to the rest of the body [Drake et a!., 2005; Guyton and Halt 1996]. Therefore, it is vital that the cardiovascular system remains healthy. Disease of the cardiovascular system, if untreated, ultimately leads to the failure of other organs and death

Speckle Tracking as a tool for Assessing foetal Cardiac Ventricular Imbalance (STACVI)

Introduction: Speckle Tracking echocardiography (STE) plays an exciting new role in the assessment of cardiac function. It is now widely used in the adult and paediatric sectors to evaluate the percentage of myocardial deformation, or % strain, with which the contractility of the muscle can be determined. It has proven validity, feasibility, and reproducibility in adult cardiology whilst demonstrating a significant contribution to clinical management, but there is still doubt regarding the clinical use in foetal cardiology due to technical barriers and a vast variation in normative data. There are, however, clinical presentations in foetal cardiology where long-term outcomes need to be counselled with caution. At 20 weeks gestation the foetal heart can be assessed for structural and functional normality, but where this borders on abnormal, there needs to be some discussion about the potential for deterioration. With little diagnostic evidence to support these borderline normal presentations, a functional tool such as speckle tracking could prove useful in predicting outcomes where there is a level of suspicion. Methods: In this study 40 foetal echocardiograms, where there was a discernible size discrepancy between the left and the right ventricles of unknown aetiology, were analysed using Tomtec Cardiac Performance Analysis (CPA) v.1.2 to provide longitudinal strain of left and right ventricular myocardial deformation. In addition, 40 echocardiograms where this imbalance in size was clearly due to a congenital heart defect were also retrospectively analysed for strain quantification. A further 40 foetal echocardiograms of age-related normal anatomy, were also analysed to provide a control group. Results: In total, 118 foetal echocardiograms were successfully analysed using CPA to obtain ventricular size, volume, and functional parameters, including percentage strain, for both the left and right ventricles across 3 groups – 1) foetuses with a foetal cardiac size discrepancy between the ventricles, 2) foetuses with a congenital heart defect and an imbalance between the size of the ventricles and 3) foetuses with normal foetal cardiac presentation. The foetal echocardiograms were retrospectively collected from foetuses between 15-24weeks gestation and results show that there was no significant difference in strain values in a ventricular size imbalance despite significant differences in size and volume of the ventricles. There was, however, a significant difference between the CHD group and control indicating that strain was reduced in the presence of a cardiac heart defect. Discussion: The results of this study show that myocardial deformation is preserved in the foetal heart where there is a ventricular size disproportion at mid-pregnancy. Significantly lowered left ventricular strain values were demonstrated in the CHD group which suggests that myocardial deformation is reduced in the presence of a congenital heart defect. These results support the theory that Speckle Tracking Echo (STE) may be a useful functional assessment tool at mid-gestation, in the presence of a congenital heart defect but not when there is only a ventricular size discrepancy. Further research is required into variations in methods, technique, and reference values to reduce technical variations, and build confidence in using STE to assess foetal cardiac function in congenital heart disease

Spatio-Temporal Nonrigid Registration for Ultrasound Cardiac Motion Estimation

We propose a new spatio-temporal elastic registration algorithm for motion reconstruction from a series of images. The specific application is to estimate displacement fields from two-dimensional ultrasound sequences of the heart. The basic idea is to find a spatio-temporal deformation field that effectively compensates for the motion by minimizing a difference with respect to a reference frame. The key feature of our method is the use of a semi-local spatio-temporal parametric model for the deformation using splines, and the reformulation of the registration task as a global optimization problem. The scale of the spline model controls the smoothness of the displacement field. Our algorithm uses a multiresolution optimization strategy to obtain a higher speed and robustness. We evaluated the accuracy of our algorithm using a synthetic sequence generated with an ultrasound simulation package, together with a realistic cardiac motion model. We compared our new global multiframe approach with a previous method based on pairwise registration of consecutive frames to demonstrate the benefits of introducing temporal consistency. Finally, we applied the algorithm to the regional analysis of the left ventricle. Displacement and strain parameters were evaluated showing significant differences between the normal and pathological segments, thereby illustrating the clinical applicability of our method

Automated analysis of 3D echocardiography

In this thesis we aim at automating the analysis of 3D echocardiography, mainly targeting the functional analysis of the left ventricle. Manual analysis of these data is cumbersome, time-consuming and is associated with inter-observer and inter-institutional variability. Methods for reconstruction of 3D echocardiographic images from fast rotating ultrasound transducers is presented and methods for analysis of 3D echocardiography in general, using tracking, detection and model-based segmentation techniques to ultimately fully automatically segment the left ventricle for functional analysis. We show that reliable quantification of left ventricular volume and mitral valve displacement can be achieved using the presented techniques.SenterNovem (IOP Beeldverwerking, grant IBVC02003), Dutch Technology Foundation STW (grant 06666)UBL - phd migration 201

Echocardiography

The book "Echocardiography - New Techniques" brings worldwide contributions from highly acclaimed clinical and imaging science investigators, and representatives from academic medical centers. Each chapter is designed and written to be accessible to those with a basic knowledge of echocardiography. Additionally, the chapters are meant to be stimulating and educational to the experts and investigators in the field of echocardiography. This book is aimed primarily at cardiology fellows on their basic echocardiography rotation, fellows in general internal medicine, radiology and emergency medicine, and experts in the arena of echocardiography. Over the last few decades, the rate of technological advancements has developed dramatically, resulting in new techniques and improved echocardiographic imaging. The authors of this book focused on presenting the most advanced techniques useful in today's research and in daily clinical practice. These advanced techniques are utilized in the detection of different cardiac pathologies in patients, in contributing to their clinical decision, as well as follow-up and outcome predictions. In addition to the advanced techniques covered, this book expounds upon several special pathologies with respect to the functions of echocardiography

Use of advanced echocardiography imaging techniques in the critically ill

Background: Critical care echocardiography has become standard of care in the ICU. New technologies have been developed and have shown potential clinical utility to elucidate myocardial dysfunction not seen with conventional imaging. We sought to determine the feasibility and potential clinical benefit of these techniques in common situations seen in the ICU. Hypothesis: Advanced echo techniques would be feasible in the majority of critically ill patients and have prognostic significance, clinical utility and diagnose cardiac abnormalities, potentially in a more sensitive manner than conventional techniques. Results: (a) Speckle tracking echocardiography (STE) Left ventricle and RV analysis with STE was feasibly in ~80% of patients. More dysfunction was found using STE vs conventional analysis. RV dysfunction assessed by STE held significant prognostic relevance in those with septic shock and highlighted subtle dysfunction induced by mechanical ventilation, both in animal and human studies. (b) 3D transthoracic echocardiography (3D TTE) Despite finding 3D TTE feasible in mechanically ventilated ICU patients (LV 72% and RV 55%), it lacked necessary low variability and high precision vs standard measures. (c) Myocardial contrast perfusion echocardiography (MCPE) Assessing acute coronary artery occlusion in the ICU patient is challenging. Troponin elevation, acute ECG changes, regional wall motion analysis on echo and overall clinical acumen often lack diagnostic capabilities. MCPE was found to be feasible in the critically ill and had better association predicting acute coronary artery occlusion vs clinical acumen alone. Conclusions: STE, 3D TTE and MCPE are feasible in the majority of ICU patients. STE may show dysfunction not recognised by conventional imaging. 3D TTE for volumetric analysis is likely not suitable for clinical use at this stage. MCPE may help guide interventions in acute coronary artery occlusion

An optimisation-based iterative approach for speckle tracking echocardiography

Speckle tracking is the most prominent technique used to estimate the regional movement of the heart based on echocardiograms. In this study, we propose an optimised-based block matching algorithm to perform speckle tracking iteratively. The proposed technique was evaluated using a publicly available synthetic echocardiographic dataset with known ground-truth from several major vendors and for healthy/ischaemic cases. The results were compared with the results from the classic (standard) two-dimensional block matching. The proposed method presented an average displacement error of 0.57 pixels, while classic block matching provided an average error of 1.15 pixels. When estimating the segmental/regional longitudinal strain in healthy cases, the proposed method, with an average of 0.32 ± 0.53, outperformed the classic counterpart, with an average of 3.43 ± 2.84. A similar superior performance was observed in ischaemic cases. This method does not require any additional ad hoc filtering process. Therefore, it can potentially help to reduce the variability in the strain measurements caused by various post-processing techniques applied by different implementations of the speckle tracking