Semi-automated quantification of left ventricular volumes and ejection fraction by real-time three-dimensional echocardiography.

Background: Recent studies have shown that real-time three-dimensional (3D) echocardiography (RT3DE) gives more accurate and reproducible left ventricular (LV) volume and ejection fraction (EF) measurements than traditional two-dimensional methods. A new semi-automated tool (4DLVQ) for volume measurements in RT3DE has been developed. We sought to evaluate the accuracy and repeatability of this method compared to a 3D echo standard.

Real-time tracking of the left ventricle in 3D echocardiography using a state estimation approach.

In this paper we present a framework for real-time tracking of deformable contours in volumetric datasets. The framework supports composite deformation models, controlled by parameters for contour shape in addition to global pose. Tracking is performed in a sequential state estimation fashion, using an extended Kalman filter, with measurement processing in information space to effectively predict and update contour deformations in real-time.

Constrained active appearance models for segmentation of triplane echocardiograms.

This paper presents multiview and multiframe active appearance models (AAMs) for left ventricular segmentation in triplane echocardiograms. We describe a general way of integrating local edge detector based segmentation algorithms into the AAM framework. The feasibility of this approach is evaluated by comparing an AAM constrained by a dynamic programming (DP) based snake with an unconstrained AAM, and an AAM constrained by manually defined landmarks.

Volume stitching in three-dimensional echocardiography: distortion analysis and extension to real time.

Three-dimensional (3D) echocardiography is challenging due to limitation of the data acquisition rate caused by the speed of sound. ECG-gated stitching of data from several cardiac cycles is a possible technique to achieve higher resolution. The aim of this work is two-fold: it is, firstly, to provide a method for real-time presentation of stitched echocardiographic images acquired over several cardiac cycles and, secondly, to demonstrate that the geometrical distortion of the images is decreased when stitching is applied to 3D ultrasonic data of the left ventricle (LV).

Myocardial strain analysis in acute coronary occlusion: a tool to assess myocardial viability and reperfusion.

Background: This study proposes 2 new echocardiographic indices with potential application in acute coronary artery occlusion to differentiate between viable and necrotic myocardium and to identify reperfusion. We investigated whether the ratio between systolic lengthening and combined late and postsystolic shortening (L-S ratio) could identify viable myocardium and whether systolic myocardial compliance, calculated as systolic lengthening divided by systolic pressure rise, could identify necrotic myocardium.

Methods And Results: In anesthetized dogs, we measured left ventricular (LV) pressure and long-axis strain by Doppler echocardiography (SDE) and sonomicrometry.

Myocardial acceleration during isovolumic contraction: relationship to contractility.

Background: Acceleration of the mitral ring during isovolumic contraction has been proposed as a load-independent index of global left ventricular (LV) contractility. This study investigates whether myocardial isovolumic acceleration (IVA) reflects regional contractility.

Methods And Results: In acutely instrumented, anesthetized dogs, we measured LV pressure, myocardial long-axis velocities, and IVA by tissue Doppler imaging (TDI) and sonomicrometry at different levels of global LV contractility and preload and during regional myocardial ischemia (reduced flow in the left anterior descending coronary artery).

Regional myocardial work by strain Doppler echocardiography and LV pressure: a new method for quantifying myocardial function.

There is a need for better methods to quantify regional myocardial function. In the present study, we investigated the feasibility of quantifying regional function in terms of a segmental myocardial work index as derived from strain Doppler echocardiography (SDE) and invasive pressure. In 10 anesthetized dogs, we measured left ventricular (LV) pressure by micromanometer and myocardial longitudinal strains by SDE and sonomicrometry.

An ultrasound-based method for determining pulse wave velocity in superficial arteries.

In this paper, we present a method for estimating local pulse wave velocity (PWV) solely from ultrasound measurements: the area-flow (QA) method. With the QA method, PWV is estimated as the ratio between change in flow and change in cross-sectional area (PWV = dQ/dA) during the reflection-free period of the cardiac cycle. In four anaesthetized dogs and 21 human subjects (age 23-74) we measured the carotid flow and cross-sectional area non-invasively by ultrasound.

Functional analysis of the common carotid artery: relative distension differences over the vessel wall measured in vivo.

Objectives: Absolute (DeltaD) and relative (DeltaD/D) arterial diameter distension, parameters related to the elasticity of the vessel, can be measured in superficial arteries using ultrasound-based vessel "wall tracking" techniques. Currently available systems (e.g.

Development of an in vivo method for determining material properties of passive myocardium.

Calculation of mechanical stresses and strains in the left ventricular (LV) myocardium by the finite element (FE) method relies on adequate knowledge of the material properties of myocardial tissue. In this paper, we present a model-based estimation procedure to characterize the stress-strain relationship in passive LV myocardium. A 3D FE model of the LV myocardium was used, which included morphological fiber and sheet structure and a nonlinear orthotropic constitutive law with different stiffness in the fiber, sheet, and sheet-normal directions.

Postsystolic shortening in ischemic myocardium: active contraction or passive recoil?

Background: Postsystolic shortening in ischemic myocardium has been proposed as a marker of tissue viability. Our objectives were to determine if postsystolic shortening represents active fiber shortening or passive recoil and if postsystolic shortening may be quantified by strain Doppler echocardiography (SDE).

Methods And Results: In 15 anesthetized dogs, we measured left ventricular (LV) pressure, myocardial long-axis strains by SDE, and segment lengths by sonomicrometry before and during LAD stenosis and occlusion.

Ultrasound-based vessel wall tracking: an auto-correlation technique with RF center frequency estimation.

Vessel diameter is related to the distending blood pressure, and is used in estimations of vessel stiffness parameters. The vessel walls can be tracked by integrating wall velocities estimated by ultrasound (US) Doppler techniques. The purpose of this work was to evaluate the performance of the modified autocorrelation estimator when applied on vessel wall motion.

Quantification of left ventricular diastolic pressure-volume relations during routine cardiac catheterization by two-dimensional digital echo quantification and left ventricular micromanometer.

Background: Currently there is no simple clinical method for quantifying the left ventricular (LV) diastolic pressure-volume relation. Echocardiographic-automated endocardial border detection, however, may be combined with LV micromanometer to construct LV pressure-volume loops. We investigated the feasibility of on-line display and sampling of LV pressure-volume loops by such an approach.