We describe a novel functional imaging approach for quantitative analysis of right ventricular (RV) blood flow patterns in specific experimental animals (or humans) using real-time, three-dimensional (3-D) echocardiography (RT3D). The method is independent of the digital imaging modality used. It comprises three parts. First, a semiautomated segmentation aided by intraluminal contrast medium locates the RV endocardial surface. Second, a geometric scheme for dynamic RV chamber reconstruction applies a time interpolation procedure to the RT3D data to quantify wall geometry and motion at 400 Hz. A volumetric prism method validated the dynamic geometric reconstruction against simultaneous sonomicrometric canine measurements. Finally, the RV endocardial border motion information is used for mesh generation on a computational fluid dynamics solver to simulate development of the early RV diastolic inflow field. Boundary conditions (tessellated endocardial surface nodal velocities) for the solver are directly derived from the endocardial geometry and motion information. The new functional imaging approach may yield important kinematic information on the distribution of instantaneous velocities in the RV diastolic flow field of specific normal or diseased hearts. cardiac image analysis; ventricular function; cardiac fluid dynamics; right ventricle; heart chamber volume QUANTITATIVE ANALYSIS of three-dimensional (3-D) digital cardiac images has become increasingly important given the recent advances in the digital cardiac imaging techniques of 3-D echocardiography, magnetic resonance imaging, computed tomography, and digital fluoroscopy (1,24,26). The growth of these digital imaging techniques is accompanied by an increasing usage of image manipulation tools, providing more elaborate image analysis and measurement and quantitative evaluation and leading to more refined diagnostic accuracy than visual interpretation alone. Moreover, complex mathematical procedures are being used to localize and highlight important changes in cardiac function that cannot be visually detected directly from the original images. With the concurrent development of high-performance computers and analytical software, a functional sort of imaging can now evolve, geared toward the creation of physiological images that are the result of a mathematical simulation derived from a set of images. Such functional imaging will allow visualization and understanding of the evolution of any dynamic process of interest (filling, ejection) within the heart. Accordingly, it should allow better insights into cardiac physiology and pathophysiology and may possibly detect warning signs of diseases not yet overt.This study developed innovative dynamic geometric chamber reconstruction models for use in functional imaging analyses of right ventricular (RV) filling dynamics and physiology. With the use of a new volumetric "prism method," it is first shown that the geometric chamber reconstructions provide accurate and reliable dynamic instantaneous RV chamber geometry ...

Piezoelectric micromachined ultrasound transducers (pMUTs) are a new approach for the construction of 2-D arrays for forward-looking 3-D intravascular (IVUS) and intracardiac (ICE) imaging. Two-dimensional pMUT test arrays containing 25 elements (5 x 5 arrays) were bulk micromachined in silicon substrates. The devices consisted of lead zirconate titanate (PZT) thin film membranes formed by deep reactive ion etching of the silicon substrate. Element widths ranged from 50 to 200 microm with pitch from 100 to 300 mum. Acoustic transmit properties were measured in de-ionized water with a calibrated hydrophone placed at a range of 20 mm. Measured transmit frequencies for the pMUT elements ranged from 4 to 13 MHz, and mode of vibration differed for the various element sizes. Element capacitance varied from 30 to over 400 pF depending on element size and PZT thickness. Smaller element sizes generally produced higher acoustic transmit output as well as higher frequency than larger elements. Thicker PZT layers also produced higher transmit output per unit electric field applied. Due to flexure mode operation above the PZT coercive voltage, transmit output increased nonlinearly with increased drive voltage. The pMUT arrays were attached directly to the Duke University T5 Phased Array Scanner to produce real-time pulse-echo B-mode images with the 2-D pMUT arrays.

The purpose of this article is to review new approaches to three-dimensional acquisition and presentation of echocardiographic data. New three-dimensional phased -array devices hold great promise for the development and application of new descriptors for left ventricular performance, myocardial perfusion, and other important indices of cardiac function. (ECHOCARDIOGRAPHY, Volume 8, January 1991) cardiac ultrasound, echocardiographyIt has long been desirable to acquire as much spatial anatomical data about the heart as possible. Two-dimensional echocardiography offered considerable advantages over M-mode echocardiography because of the ability to provide real-time tomographic images of the heart and it extended the ability of practitioners to make complex diagnostic decisions. In the beginning, there were questions by some whether two-dimensional approaches were worth the time and expense. Continued experience with these methods provided a n opportunity for clinicians to ask new questions. Similarly, threedimensional echocardiography appears to be a desirable goal as it would likely provide a method for deriving new anatomical, functional, and flow indices of the human heart. Two-Dimensional LimitationsDespite the obvious advantages of two-dimensional echocardiography methods over Mmode, serious limitations remain. Cardiac structures are spatially complex and a mental picture of the heart must be acquired from a