Layer-specific assessment of left ventricular function by utilizing wavelet de-noising: a validation study

Abstract

Regional myocardial function assessment is essential for diagnosis and evaluation of heart disease. The purpose of this study was to enhance the spatial resolution of a speckle tracking echocardiography approach and enable layer-specific analysis of the myocardium. Following validation with software-implemented and mechanical phantoms versus imposed values, short-axis cines were obtained from 50 rats. The cines were post-processed by a speckle tracking commercial program, and the myocardial velocities were processed by a three-dimensional wavelet de-noising program, instead of the built-in smoothing process of the commercial program. Software-implemented phantom measurements yielded rotation errors of 7.5%, 2.9%, and 3.4%, for inner, middle, and outer layers, respectively. Analysis of a shrinking/expanding mechanical phantom yielded strain errors of 3%, 5%, and 7% for the three layers. Bland-Altman analysis showed agreement between the commercial and enhanced programs. Thus, layer-specific analysis is feasible while using echocardiography even on small animals such as rats.

Layer-specific strain analysis: investigation of regional deformations in a rat model of acute versus chronic myocardial infarction

“…Scans were postprocessed by the LS-STE program, which measures LV function at three myocardial layers and six segments: inferior septum, anterior septum, anterior wall, lateral wall, posterior wall, and inferior wall (4,5). The program uses a commercial STE program (EchoPAC Dimension '08, GE Healthcare) that requests the user to mark the endocardial border and to choose the width of the myocardium.…”

“…It imposes a grid of points in the assigned region and tracks the speckles near the points and evaluates their velocities at each frame (34). The measured velocities were not processed by the built-in smoothing of the commercial program but were denoised by a three-dimensional wavelet representation (MATLAB software, MathWorks), thereby increasing the spatial resolution of the myocardial velocities to three myocardial layers (5). This algorithm denotes the myocardial velocities that have low-and high-frequency components.…”

“…The LS-STE program is able to calculate myocardial deformations at three myocardial layers owing to the usage of wavelet denoising (5), and thus this method may turn out to be favorable in the diagnosis of MI over the traditional STE method. The LS-STE method was validated against computerized and mechanical phantoms (5), and its advantage has been demonstrated in chronic ischemic patients, in whom endocardial strain was found to be a reliable detector of nontransmural MI and epicardial strain as a reliable detector of transmural MI (6). However, no study has tested layer-specific strains at acute and chronic stages of MI versus histological analysis.…”

Assessment of Regional Longitudinal Stain by Using Speckle Tracking Echocardiography – A Validation Study

“…The wavelet shrinkage method was applied to the myocardial velocities as described by Bachner-Hinenzon et al (2010). At first, low tracking quality data points are replaced by a weighted average of their neighboring data points.…”

“…Following the wavelet decomposition, the Detail coefficients are thresholded by hard and soft threshold. For the first level, the Detail coefficients are removed completely (hard threshold) and for the second and third levels a soft universal threshold was used (Bachner-Hinenzon et al 2010). Finally, to obtain the smoothed signal, the inverse of 3D discrete wavelet transform is computed using reconstruction filters in an iterated process.…”