2D+T acoustic boundary detection in echocardiography.

Time to onset of regional relaxation: feasibility, variability and utility of a novel index of regional myocardial function by strain rate imaging.

Objective—To determine left ventricular free wall (LVFW) radial and longitudinal myocardial contraction velocities in healthy dogs via quantitative 2-dimensional color tissue Doppler imaging (TDI). Animals—100 dogs. Procedure—TDI was used by a single trained observer to measure radial and longitudinal myocardial movement in the LVFW. Radial myocardial velocities were recorded in segments in the endocardial and epicardial layers of the LVFW, and longitudinal velocities were recorded in segments at 3 levels (basal, middle, apical) of the LVFW. Results—LVFW velocities were higher in the endocardial layers than in the epicardial layers. Left ventricular free wall velocities were higher in the basal segments than in the middle and apical segments. Radial myocardial velocity gradients, defined as the difference between endocardial and epicardial velocities, were (mean ± SD) 2.5 ± 0.8 cm/s, 3.8 ± 1.5 cm/s, and 2.3 ± 0.9 cm/s in systole, early diastole, and late diastole, respectively. Longitudinal myocardial vel...

Use of quantitative two-dimensional color tissue Doppler imaging for assessment of left ventricular radial and longitudinal myocardial velocities in dogs.

Tissue Doppler echocardiography is a variation of conventional Doppler flow imaging. This modality allows quantification of the Doppler shift within the range of myocardial tissue motion. The velocity at a variety of myocardial sites can be determined and distinguished very rapidly by using Doppler techniques. The velocity of moving tissue can be studied with pulsed wave tissue Doppler sampling, which displays the velocity of a selected myocardial region against time, with high temporal resolution. In addition, the velocities can be calculated with time-velocity maps and displayed as color-encoded velocity maps in either an M-mode or 2-dimensional format. This review will focus on the technical aspects and the different methods of tissue Doppler echocardiography for the analysis of regional systolic and diastolic left ventricular function. Whereas pulsed wave tissue Doppler echocardiography allows measurements of velocities of a selected myocardial region, color tissue Doppler gives the best overview of cardiac dynamics because the entire scanned color data are displayed simultaneously. However, there is an increasing need for objective evaluation of tissue Doppler information. Digital images and postprocessing of the data allow for quantitative off-line analysis, and the different approaches and parameters proposed from different centers are discussed.

New insights into regional systolic and diastolic left ventricular function with tissue Doppler echocardiography: from qualitative analysis to a quantitative approach.

In this paper we address the problem of spatio-temporal acoustic boundary detection in echocardiography. We propose a phase-based feature detection method to be used as the front end to higher-level 2D+T/3D+T reconstruction algorithms. We develop a 2D+T version of this algorithm and illustrate its performance on some typical echocar-diogram sequences. We show how our temporal-based algorithm helps to reduce the number of spurious feature responses due to speckle and provides feature velocity estimates. Further, our approach is intensity-amplitude invariant. This makes it particularly attractive for echocardiographic segmentation, where choosing a single global intensity-based edge threshold is problematic.

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J. Azevedo

Papers

Doppler Tissue Imaging: Echocardiography