Peter Lysyansky - Academia.edu (original) (raw)
Papers by Peter Lysyansky
European Journal of Echocardiography, 2003
European Journal of Echocardiography, 2003
We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quant... more We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quantitative echocardiographic assessment of myocardial function. Methods: Conventional and a novel non-Dopplerbased echocardiography technique for advanced wall-motion analysis were performed in 20 patients with myocardial infarction and 10 healthy volunteers from the apical views. Two-dimensional strain is on the basis of the estimation that a discrete set of tissue velocities are present per each of many small elements on the ultrasound image. This software permits real-time assessment of myocardial velocities, strain, and strain rate. These parameters were also compared with Doppler tissue imaging measurements in 10 additional patients.
European Journal of Echocardiography, 2006
Accurate assessment of left ventricular ejection fraction is part of a comprehensive echocardiogr... more Accurate assessment of left ventricular ejection fraction is part of a comprehensive echocardiographic examination and is a routine daily clinical problem. Traditionally, LVEF has been calculated based on the biplane Simpson's rule algorithm. This method requires high image quality and is entirely operator-dependent. Since second harmonic imaging has been introduced, several different echocardiographic techniques have been suggested for calculating EF: automatic border detection, contrast echocardiog-raphy, and three-dimensional echocardiography. These methods are either time consuming, or require an experienced operator, good image quality and special and often expensive equipment.
JACC: Cardiovascular Imaging, 2015
This study aimed to investigate to what extent timing definitions influence strain measurements a... more This study aimed to investigate to what extent timing definitions influence strain measurements and which surrogates are reliable and feasible to define end-diastole (ED) and end-systole (ES) during speckle-tracking (STI) analysis. Current STI-based strain measurements are highly automated. It remains unclear when a particular analysis software defines the zero baseline and the systolic strain measurement position. A total of 60 subjects (20 healthy volunteers, 20 patients with coronary artery disease, and 20 patients with typical left bundle-branch block) underwent a complete echocardiographic examination. In one-half of them, a real M-mode through the mitral valve was acquired for each electrocardiographic (ECG) lead of the echo machine. Timing of peak R and automatic ECG trigger were compared with mitral valve closure for every electrode. Mitral and aortic valve closure, as observed in the apical 3-chamber view, served as reference for ED and ES. With the use of these references, end-systolic global longitudinal strain (ES-GLS) and end-systolic segmental longitudinal strain (ES-SLS) longitudinal end-systolic strain were measured at baseline and after changing the definition of either ED or ES by ±4 frames. Furthermore, strain and volume curves derived from the same tracking, as well as the Doppler interrogation of the valves, were compared with the references. Depending on the selected lead, timing of the ECG-derived time markers changed considerably compared with mitral valve closure. Changing the definition of ED and ES resulted in significantly different ES-GLS and ES-SLS values in all subjects. ES-SLS in dyssynchronous hearts showed the highest sensitivity to timing definition. From all methods, spectral Doppler was the most reliable time marker in all subjects (p > 0.05). Exact temporal definition of ED and ES has a major impact on the accuracy of strain measurements. After direct observation of the valves, Doppler evaluation is the best means for characterizing ED and ES for STI analysis.
Journal of the American Society of Echocardiography, 2004
We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quant... more We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quantitative echocardiographic assessment of myocardial function. Methods: Conventional and a novel non-Dopplerbased echocardiography technique for advanced wall-motion analysis were performed in 20 patients with myocardial infarction and 10 healthy volunteers from the apical views. Two-dimensional strain is on the basis of the estimation that a discrete set of tissue velocities are present per each of many small elements on the ultrasound image. This software permits real-time assessment of myocardial velocities, strain, and strain rate. These parameters were also compared with Doppler tissue imaging measurements in 10 additional patients.
Journal of the American College of Cardiology, 2003
and aim: echocardiographic estimation of left ventricular global and segmental function is subjec... more and aim: echocardiographic estimation of left ventricular global and segmental function is subjective and prone to considerable intra and interobserver variability.
European heart journal cardiovascular Imaging, Jan 18, 2015
Speckle tracking echocardiography has already demonstrated its clinical potential. However, its u... more Speckle tracking echocardiography has already demonstrated its clinical potential. However, its use in routine practice is jeopardized by recent reports on high inter-vendor variability of the measurements. As such, the European Association of CardioVascular Imaging (EACVI) and the American Society of Echocardiography (ASE) set up a standardization task force, which was joined by all manufacturers of echocardiographic equipment as well as by companies offering software solutions only, with the ambition to tackle this problem by standardization and quality assurance (QA). In this study, a first step towards QA of all commercially available tracking solutions based on computer-generated ultrasound images is presented. The accuracy of the products was acceptable with relative errors below 10% and intra-vendor reproducibility within 5%. Whether these results can be extrapolated to the clinical setting is the topic of an ongoing study of the EACVI/ASE/Industry Task Force to standardize d...
Computers in Cardiology, 2004, 2004
Quantification of cardiac local contraction across the entire ventricle wall is essential for bet... more Quantification of cardiac local contraction across the entire ventricle wall is essential for better diagnosis and therapeutic planning. A new ultrasound B-mode image analysis technique was developed that identifies and tracks real reflectors in successive frames. This study tests the ability the technique to identify the mechanical propagation sequence. Cardiac function was monitored (sheep open chest studies, n=7) by pressure transducers, sonocrystals, and aortic flow meter, concurrent with ultrasound image acquisition. Epicardial electrodes mapped electrical propagation, and allowed different LV pacings. Normal SA node derived activity was compared with abnormal LV contractions. Mechanical indices derived from US images correlated well with the sonocrystals measurements, and the sequence of mechanical contraction with the measured electrical activation. Image analysis allows precise reconstruction of myocardial activation with 16msec time resolution.
Computers in Cardiology, 2005, 2005
Non-invasive estimation of the mechanical activation sequence provides valuable diagnostic inform... more Non-invasive estimation of the mechanical activation sequence provides valuable diagnostic information on myocardial function. Here, an attempt is made to retrieve it from longitudinal strains calculated from B-mode echo-cardiographic loops in 3 sheep, paced at 2 sites - lateral and septal, and compare it to normal sequences. B-mode LV basal short-axis images were acquired followed by off-line analysis of speckle tracking imaging by 2D Strain, a customized software application that calculates regional strains. Mechanical activation times were assessed as onset times of circumferential shortening measured from strain profiles, and quantified by the segmental propagation vector (SDV). The time of 90% activation within the ROI of the LV was ~60plusmn5 ms for lateral pacing, ~65plusmn5 ms for septal pacing vs. ~40plusmn5 ms for no-pacing, showing degradation of synchrony. The directivity of the propagation pattern was significantly higher (lower variance) of the SDV in the paced modes
European heart journal cardiovascular Imaging, 2012
Assessing the quality of wall motion (WM) on echocardiograms remains a challenge. Previously, we ... more Assessing the quality of wall motion (WM) on echocardiograms remains a challenge. Previously, we validated an automated application used by experienced echocardiographers for WM classification based on longitudinal two-dimensional (2D) strain. The aim of this study was to show that the use of this automatic application was independent of the user's experience. We compared the WM classifications obtained by the application when used by 12 highly experienced readers (Exp-R) vs. 11 inexperienced readers (InExp-R). Both classifications were compared with expert consensus classifications using the standard visual method. Digitized clips of cardiac cycles from three apical views in 105 patients were used for these analyses. Reproducibility of both groups was high (overall intra-class correlation coefficient: InExp-R = 0.89, Exp-R = 0.83); the lowest was noted for hypokinetic segments (InExp-R = 0.79, Exp-R = 0.72). InExp-R scores were concordant with Exp-R mode scores in 88.8% of segm...
The Israel Medical Association journal : IMAJ, 2007
Echocardiographic assessment of left ventricular function includes calculation of ejection fracti... more Echocardiographic assessment of left ventricular function includes calculation of ejection fraction and regional wall motion analysis. Recently, speckle imaging was introduced for quantification of left ventricular function. To assess LVEF by speckle imaging and compare it with Simpson's method, and to assess the regional LV strain obtained by speckle imaging in relation to conventional echocardiographic scores. Thirty consecutive patients, 28 with regional LV dysfunction, underwent standard echocardiographic evaluation. LV end-diastolic volume, LV end-systolic volume and EF were calculated independently by speckle imaging and Simpson's rule. The regional peak systolic strain presented by speckle imaging as a bull's-eye map was compared with the conventional visual estimate of echo score. Average EDV obtained by speckle imaging and by Simpson's method was 85.1 vs. 92.7 ml (P = 0.38), average ESV was 49.4 vs. 48.8 ml (P = 0.94), calculated EF was 43.9 vs. 50.5% (P = 0...
European Journal of Echocardiography, 2006
Background: Two-dimensional strain echocardiography (2D-SE) calculates tissue velocities via fram... more Background: Two-dimensional strain echocardiography (2D-SE) calculates tissue velocities via frame-to-frame tracking of unique acoustic markers within the image and provides strain parameters in two dimensions. Novel 2D-SE software allows semi-automated strain measurements and increased averaging capabilities optimizing signalenoise ratio. Aim: We tested whether 2D-SE and the currently used and well-validated tissue Doppler derived strain echocardiography (TD-SE) yield similar information in the clinical setting. Methods and results: We performed 2D-SE and TD-SE on 17 patients with amyloid cardiomyopathy and 10 age-matched healthy volunteers. Single walls from standard apical views (2-and 4-chamber) were acquired at high frame rates (w200 fps). Offline analysis was performed by observers blinded to clinical data using the EchoPAC program with custom 2D-SE software. Longitudinal strain rate and strain from the basal, mid and apical segments of the septal and lateral walls were determined by each method (TD-SE and 2D-SE). Ejection fraction was O0.55 in healthy volunteers and ranged from 0.30 to 0.80 in cardiomyopathy group. A total of 54 walls (162 segments) were examined. Acceptable quality strain data was available in 92% and 85% segments by 2D-SE and TD-SE, respectively. Twodimensional strain echocardiography values correlated closely with TD-SE values (r Z 0.94 and 0.96 for strain rate and strain, respectively).
Ultrasound in Obstetrics and Gynecology, 1998
The use of Doppler indices of tumor vascularity as markers for malignancy has been a subject of d... more The use of Doppler indices of tumor vascularity as markers for malignancy has been a subject of debate, with inconsistencies in specificity and sensitivity as well as in the diagnostic cut-off values. Part of the discrepancy might be explained by the limited number of vessels selected within the tumor for Doppler evaluation. A typical sample of three or four vessels may not be sufficiently large for correct representation of the vasculature of the tumor, which may contain many vessels. The existing conventional Doppler (color and spectral) techniques clearly have limitations. We present here a novel Doppler modality, namely two-dimensional spectral Doppler imaging (SDI), which allows the acquisition of many Doppler spectra within a few seconds. The operator selects a region of interest within a color Doppler image. The Doppler sequence is initiated and the entire selected region is automatically scanned for about 20 s until all spectral Doppler data have been acquired and processed. The system computer generates a color-coded map of the desired Doppler indices overlaid on the gray-scale image. The system also displays a cumulative histogram or a table of the requested Doppler index from all the sections in the tissue. The whole process is automatically performed by the system computer, without any need for operator intervention. The system provides the examiner with a 'fishing net' for Doppler indices, instead of the 'fishing hook' used in current techniques.
Ultrasound in Medicine & Biology, 2006
To date, established ultrasonic methods for myocardial regional deformation recovery are based on... more To date, established ultrasonic methods for myocardial regional deformation recovery are based on the Doppler effect, which has inherent limitations restricting its accuracy and use. The reported time domain methods show in vivo insufficient accuracy. A novel approach is elaborated mimicking the human observer who reaches robust diagnosis upon the B-mode data. In a region-of-interest (ROI), acoustic markers stable for tracking are selected. A weighting index presenting the quality of tracking of each marker is used for spatial polynomial fitting. For the feasibility study, a simple straight ROI was selected, which matches the septum. A thorough proof of concept is provided by comparing with a gold standard method and by applying the method to clinical datasets. The peak systolic longitudinal strains of 12 normals were -15% ؉ -2.3% and, of 12 patients with a light-to-mild dysfunction of the apical-septal segment, they were -9% ؉ -0.8% (p < 0.05). Enhancements of the method using spline fitting are introduced. (E-mail: dan@biomed.technion.ac.il )
Ultrasound in Medicine & Biology, 2007
Asynchronous cardiac activation leads to decreased pumping efficiency. Quantifying the activation... more Asynchronous cardiac activation leads to decreased pumping efficiency. Quantifying the activation sequence may optimize both the selection of patients for cardiac resynchronization therapy (CRT) and its efficacy. The feasibility of assessing the directivity and the degree of synchronous activation with ultrasound was examined. A tissue tracking method (CEB, GE-Ultrasound, AFI, GE Healthcare Inc., Wauwatosa, WI, USA) provided the regional strain profiles. The first maxima in systole of the regional circumferential strains were considered as the activation times. An integrative vector (SDV) describes the activation synchrony and directivity. In six open-chest sheep, activation maps and SDV were calculated in short-axis planes of the left ventricle for normal activation and induced pacings from the anterior and lateral free walls. Both magnitude and angle of the SDV were statistically different (p < 0.05) for the different pacings. Localization of the pacing site was 3°؎ 18°from true position. Conclusions were that motion analysis in echocardiograms provides insightful information regarding the activation process and may enhance procedures such as CRT. (E-mail: Dan@bm.technion.ac.il)
Ultrasonics, 2004
Cardiac elastography is a useful diagnostic technique for detection of heart function abnormaliti... more Cardiac elastography is a useful diagnostic technique for detection of heart function abnormalities, based on analysis of echocardiograms. The analysis of the regional heart motion allows assessing the extent of myocardial ischemia and infarction. In this paper, a new two-stage algorithm for cardiac motion estimation is proposed, where the data is taken from a sequence of 2D echocardiograms. The method combines the advantages of block-matching and optical flow techniques. The first stage employs a standard block-matching algorithm (sum of absolute differences) to provide a displacement estimate with accuracy of up to one pixel. At the second stage, this estimate is corrected by estimating the parameters of a local image transform within a test window. The parameters of the image transform are estimated in the least-square sense. In order to account for typical heart motions, like contraction/expansion, translation and rotation, a local affine model is assumed within the test window. The accuracy of the new algorithm is evaluated using a sequence of 500 grayscale B-mode images, which are generated as distorted, but known copies of an original ROI, taken from a real echocardiogram. The accuracy of the motion estimation is expressed in terms of errors: maximum absolute error, root-mean-square error, average error and standard deviation. The errors of the proposed algorithm are compared with these of the known block-matching technique with cross-correlation and interpolation in the sub-pixel space. Statistical analysis of the errors shows that the proposed algorithm provides more accurate estimates of the heart motion than the crosscorrelation technique with interpolation in the sub-pixel space.
Ultrasonics, 2004
Recently, a spatial compounding ultrasound imaging method was presented that utilizes a conventio... more Recently, a spatial compounding ultrasound imaging method was presented that utilizes a conventional 64-element phased array transducer with two unfocused pistons, each placed at one of the sides of the phased array transducer. This method is augmented here by inclusion of nonlinear filtering of the compounded images. The combined effects of the specific spatial compounding and nonlinear filtering on speckle reduction in the generated ultrasound images are studied and evaluated in two stages: First, the image quality is studied when nonlinear filtering is used as part of the spatial compounding. The study is performed by simulations using the Field II program, by processing several B-mode images of a kidney. The second stage compares the results obtained by the simulations to those obtained by in vitro laboratory experiments. Five different compounding strategies and two nonlinear filters, Gaussian and anisotropic diffusion, are investigated and evaluated in terms of image quality parameters-contrast and signal-to-noise ratio. It is shown that the combination of ''averaging + nonlinear Gaussian filtering'' produces the greatest improvement of image quality. When compared to a conventional phased array imaging system, the spatial compounding method that includes the conventional 64-element phased array transducer with two unfocused pistons, and employs the ''averaging + nonlinear Gaussian filtering'' strategy, obtains improvement in SNR that has reached 334%. Thus, though this method necessitates a somewhat wider probe, it produces significantly improved images.
Medical & Biological Engineering & Computing, 2008
The objective of this study was to validate a recently developed tissue tracking (TT) method for ... more The objective of this study was to validate a recently developed tissue tracking (TT) method for cardiac motion, by comparing it with precise invasive measurements of motion and to prove its capability to reflect moderate hemodynamic changes induced by asynchronous activation. In four open-chest sheep, sono-crystals measured the left ventricle(LV) equator's diameters simultaneously with 2D ultrasound acquisition. The LV was paced either from the posterior or from the lateral wall, just prior to the normal LV activation. Global functional indices were calculated based on the regional motions extracted by the TT method. The correlation coefficient between the shortening of the diameters and the global circumferential strain (GCS) was 0.99 ± 0.004. The peak GCS differentiated between the pacing modes (paired t test, P \ 0.05). The GCS, a measurement closely based on the TT method, followed the precise sono-crystals measurements and reflected moderate hemodynamic changes, thus providing a substantial proof of the TT method's accuracy and clinical value.
Journal of the American Society of Echocardiography, 2004
European Journal of Echocardiography, 2003
European Journal of Echocardiography, 2003
We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quant... more We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quantitative echocardiographic assessment of myocardial function. Methods: Conventional and a novel non-Dopplerbased echocardiography technique for advanced wall-motion analysis were performed in 20 patients with myocardial infarction and 10 healthy volunteers from the apical views. Two-dimensional strain is on the basis of the estimation that a discrete set of tissue velocities are present per each of many small elements on the ultrasound image. This software permits real-time assessment of myocardial velocities, strain, and strain rate. These parameters were also compared with Doppler tissue imaging measurements in 10 additional patients.
European Journal of Echocardiography, 2006
Accurate assessment of left ventricular ejection fraction is part of a comprehensive echocardiogr... more Accurate assessment of left ventricular ejection fraction is part of a comprehensive echocardiographic examination and is a routine daily clinical problem. Traditionally, LVEF has been calculated based on the biplane Simpson's rule algorithm. This method requires high image quality and is entirely operator-dependent. Since second harmonic imaging has been introduced, several different echocardiographic techniques have been suggested for calculating EF: automatic border detection, contrast echocardiog-raphy, and three-dimensional echocardiography. These methods are either time consuming, or require an experienced operator, good image quality and special and often expensive equipment.
JACC: Cardiovascular Imaging, 2015
This study aimed to investigate to what extent timing definitions influence strain measurements a... more This study aimed to investigate to what extent timing definitions influence strain measurements and which surrogates are reliable and feasible to define end-diastole (ED) and end-systole (ES) during speckle-tracking (STI) analysis. Current STI-based strain measurements are highly automated. It remains unclear when a particular analysis software defines the zero baseline and the systolic strain measurement position. A total of 60 subjects (20 healthy volunteers, 20 patients with coronary artery disease, and 20 patients with typical left bundle-branch block) underwent a complete echocardiographic examination. In one-half of them, a real M-mode through the mitral valve was acquired for each electrocardiographic (ECG) lead of the echo machine. Timing of peak R and automatic ECG trigger were compared with mitral valve closure for every electrode. Mitral and aortic valve closure, as observed in the apical 3-chamber view, served as reference for ED and ES. With the use of these references, end-systolic global longitudinal strain (ES-GLS) and end-systolic segmental longitudinal strain (ES-SLS) longitudinal end-systolic strain were measured at baseline and after changing the definition of either ED or ES by ±4 frames. Furthermore, strain and volume curves derived from the same tracking, as well as the Doppler interrogation of the valves, were compared with the references. Depending on the selected lead, timing of the ECG-derived time markers changed considerably compared with mitral valve closure. Changing the definition of ED and ES resulted in significantly different ES-GLS and ES-SLS values in all subjects. ES-SLS in dyssynchronous hearts showed the highest sensitivity to timing definition. From all methods, spectral Doppler was the most reliable time marker in all subjects (p &amp;amp;amp;amp;amp;amp;amp;gt; 0.05). Exact temporal definition of ED and ES has a major impact on the accuracy of strain measurements. After direct observation of the valves, Doppler evaluation is the best means for characterizing ED and ES for STI analysis.
Journal of the American Society of Echocardiography, 2004
We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quant... more We sought to assess the feasibility of 2-dimensional strain, a novel software for real-time quantitative echocardiographic assessment of myocardial function. Methods: Conventional and a novel non-Dopplerbased echocardiography technique for advanced wall-motion analysis were performed in 20 patients with myocardial infarction and 10 healthy volunteers from the apical views. Two-dimensional strain is on the basis of the estimation that a discrete set of tissue velocities are present per each of many small elements on the ultrasound image. This software permits real-time assessment of myocardial velocities, strain, and strain rate. These parameters were also compared with Doppler tissue imaging measurements in 10 additional patients.
Journal of the American College of Cardiology, 2003
and aim: echocardiographic estimation of left ventricular global and segmental function is subjec... more and aim: echocardiographic estimation of left ventricular global and segmental function is subjective and prone to considerable intra and interobserver variability.
European heart journal cardiovascular Imaging, Jan 18, 2015
Speckle tracking echocardiography has already demonstrated its clinical potential. However, its u... more Speckle tracking echocardiography has already demonstrated its clinical potential. However, its use in routine practice is jeopardized by recent reports on high inter-vendor variability of the measurements. As such, the European Association of CardioVascular Imaging (EACVI) and the American Society of Echocardiography (ASE) set up a standardization task force, which was joined by all manufacturers of echocardiographic equipment as well as by companies offering software solutions only, with the ambition to tackle this problem by standardization and quality assurance (QA). In this study, a first step towards QA of all commercially available tracking solutions based on computer-generated ultrasound images is presented. The accuracy of the products was acceptable with relative errors below 10% and intra-vendor reproducibility within 5%. Whether these results can be extrapolated to the clinical setting is the topic of an ongoing study of the EACVI/ASE/Industry Task Force to standardize d...
Computers in Cardiology, 2004, 2004
Quantification of cardiac local contraction across the entire ventricle wall is essential for bet... more Quantification of cardiac local contraction across the entire ventricle wall is essential for better diagnosis and therapeutic planning. A new ultrasound B-mode image analysis technique was developed that identifies and tracks real reflectors in successive frames. This study tests the ability the technique to identify the mechanical propagation sequence. Cardiac function was monitored (sheep open chest studies, n=7) by pressure transducers, sonocrystals, and aortic flow meter, concurrent with ultrasound image acquisition. Epicardial electrodes mapped electrical propagation, and allowed different LV pacings. Normal SA node derived activity was compared with abnormal LV contractions. Mechanical indices derived from US images correlated well with the sonocrystals measurements, and the sequence of mechanical contraction with the measured electrical activation. Image analysis allows precise reconstruction of myocardial activation with 16msec time resolution.
Computers in Cardiology, 2005, 2005
Non-invasive estimation of the mechanical activation sequence provides valuable diagnostic inform... more Non-invasive estimation of the mechanical activation sequence provides valuable diagnostic information on myocardial function. Here, an attempt is made to retrieve it from longitudinal strains calculated from B-mode echo-cardiographic loops in 3 sheep, paced at 2 sites - lateral and septal, and compare it to normal sequences. B-mode LV basal short-axis images were acquired followed by off-line analysis of speckle tracking imaging by 2D Strain, a customized software application that calculates regional strains. Mechanical activation times were assessed as onset times of circumferential shortening measured from strain profiles, and quantified by the segmental propagation vector (SDV). The time of 90% activation within the ROI of the LV was ~60plusmn5 ms for lateral pacing, ~65plusmn5 ms for septal pacing vs. ~40plusmn5 ms for no-pacing, showing degradation of synchrony. The directivity of the propagation pattern was significantly higher (lower variance) of the SDV in the paced modes
European heart journal cardiovascular Imaging, 2012
Assessing the quality of wall motion (WM) on echocardiograms remains a challenge. Previously, we ... more Assessing the quality of wall motion (WM) on echocardiograms remains a challenge. Previously, we validated an automated application used by experienced echocardiographers for WM classification based on longitudinal two-dimensional (2D) strain. The aim of this study was to show that the use of this automatic application was independent of the user's experience. We compared the WM classifications obtained by the application when used by 12 highly experienced readers (Exp-R) vs. 11 inexperienced readers (InExp-R). Both classifications were compared with expert consensus classifications using the standard visual method. Digitized clips of cardiac cycles from three apical views in 105 patients were used for these analyses. Reproducibility of both groups was high (overall intra-class correlation coefficient: InExp-R = 0.89, Exp-R = 0.83); the lowest was noted for hypokinetic segments (InExp-R = 0.79, Exp-R = 0.72). InExp-R scores were concordant with Exp-R mode scores in 88.8% of segm...
The Israel Medical Association journal : IMAJ, 2007
Echocardiographic assessment of left ventricular function includes calculation of ejection fracti... more Echocardiographic assessment of left ventricular function includes calculation of ejection fraction and regional wall motion analysis. Recently, speckle imaging was introduced for quantification of left ventricular function. To assess LVEF by speckle imaging and compare it with Simpson's method, and to assess the regional LV strain obtained by speckle imaging in relation to conventional echocardiographic scores. Thirty consecutive patients, 28 with regional LV dysfunction, underwent standard echocardiographic evaluation. LV end-diastolic volume, LV end-systolic volume and EF were calculated independently by speckle imaging and Simpson's rule. The regional peak systolic strain presented by speckle imaging as a bull's-eye map was compared with the conventional visual estimate of echo score. Average EDV obtained by speckle imaging and by Simpson's method was 85.1 vs. 92.7 ml (P = 0.38), average ESV was 49.4 vs. 48.8 ml (P = 0.94), calculated EF was 43.9 vs. 50.5% (P = 0...
European Journal of Echocardiography, 2006
Background: Two-dimensional strain echocardiography (2D-SE) calculates tissue velocities via fram... more Background: Two-dimensional strain echocardiography (2D-SE) calculates tissue velocities via frame-to-frame tracking of unique acoustic markers within the image and provides strain parameters in two dimensions. Novel 2D-SE software allows semi-automated strain measurements and increased averaging capabilities optimizing signalenoise ratio. Aim: We tested whether 2D-SE and the currently used and well-validated tissue Doppler derived strain echocardiography (TD-SE) yield similar information in the clinical setting. Methods and results: We performed 2D-SE and TD-SE on 17 patients with amyloid cardiomyopathy and 10 age-matched healthy volunteers. Single walls from standard apical views (2-and 4-chamber) were acquired at high frame rates (w200 fps). Offline analysis was performed by observers blinded to clinical data using the EchoPAC program with custom 2D-SE software. Longitudinal strain rate and strain from the basal, mid and apical segments of the septal and lateral walls were determined by each method (TD-SE and 2D-SE). Ejection fraction was O0.55 in healthy volunteers and ranged from 0.30 to 0.80 in cardiomyopathy group. A total of 54 walls (162 segments) were examined. Acceptable quality strain data was available in 92% and 85% segments by 2D-SE and TD-SE, respectively. Twodimensional strain echocardiography values correlated closely with TD-SE values (r Z 0.94 and 0.96 for strain rate and strain, respectively).
Ultrasound in Obstetrics and Gynecology, 1998
The use of Doppler indices of tumor vascularity as markers for malignancy has been a subject of d... more The use of Doppler indices of tumor vascularity as markers for malignancy has been a subject of debate, with inconsistencies in specificity and sensitivity as well as in the diagnostic cut-off values. Part of the discrepancy might be explained by the limited number of vessels selected within the tumor for Doppler evaluation. A typical sample of three or four vessels may not be sufficiently large for correct representation of the vasculature of the tumor, which may contain many vessels. The existing conventional Doppler (color and spectral) techniques clearly have limitations. We present here a novel Doppler modality, namely two-dimensional spectral Doppler imaging (SDI), which allows the acquisition of many Doppler spectra within a few seconds. The operator selects a region of interest within a color Doppler image. The Doppler sequence is initiated and the entire selected region is automatically scanned for about 20 s until all spectral Doppler data have been acquired and processed. The system computer generates a color-coded map of the desired Doppler indices overlaid on the gray-scale image. The system also displays a cumulative histogram or a table of the requested Doppler index from all the sections in the tissue. The whole process is automatically performed by the system computer, without any need for operator intervention. The system provides the examiner with a 'fishing net' for Doppler indices, instead of the 'fishing hook' used in current techniques.
Ultrasound in Medicine & Biology, 2006
To date, established ultrasonic methods for myocardial regional deformation recovery are based on... more To date, established ultrasonic methods for myocardial regional deformation recovery are based on the Doppler effect, which has inherent limitations restricting its accuracy and use. The reported time domain methods show in vivo insufficient accuracy. A novel approach is elaborated mimicking the human observer who reaches robust diagnosis upon the B-mode data. In a region-of-interest (ROI), acoustic markers stable for tracking are selected. A weighting index presenting the quality of tracking of each marker is used for spatial polynomial fitting. For the feasibility study, a simple straight ROI was selected, which matches the septum. A thorough proof of concept is provided by comparing with a gold standard method and by applying the method to clinical datasets. The peak systolic longitudinal strains of 12 normals were -15% ؉ -2.3% and, of 12 patients with a light-to-mild dysfunction of the apical-septal segment, they were -9% ؉ -0.8% (p < 0.05). Enhancements of the method using spline fitting are introduced. (E-mail: dan@biomed.technion.ac.il )
Ultrasound in Medicine & Biology, 2007
Asynchronous cardiac activation leads to decreased pumping efficiency. Quantifying the activation... more Asynchronous cardiac activation leads to decreased pumping efficiency. Quantifying the activation sequence may optimize both the selection of patients for cardiac resynchronization therapy (CRT) and its efficacy. The feasibility of assessing the directivity and the degree of synchronous activation with ultrasound was examined. A tissue tracking method (CEB, GE-Ultrasound, AFI, GE Healthcare Inc., Wauwatosa, WI, USA) provided the regional strain profiles. The first maxima in systole of the regional circumferential strains were considered as the activation times. An integrative vector (SDV) describes the activation synchrony and directivity. In six open-chest sheep, activation maps and SDV were calculated in short-axis planes of the left ventricle for normal activation and induced pacings from the anterior and lateral free walls. Both magnitude and angle of the SDV were statistically different (p < 0.05) for the different pacings. Localization of the pacing site was 3°؎ 18°from true position. Conclusions were that motion analysis in echocardiograms provides insightful information regarding the activation process and may enhance procedures such as CRT. (E-mail: Dan@bm.technion.ac.il)
Ultrasonics, 2004
Cardiac elastography is a useful diagnostic technique for detection of heart function abnormaliti... more Cardiac elastography is a useful diagnostic technique for detection of heart function abnormalities, based on analysis of echocardiograms. The analysis of the regional heart motion allows assessing the extent of myocardial ischemia and infarction. In this paper, a new two-stage algorithm for cardiac motion estimation is proposed, where the data is taken from a sequence of 2D echocardiograms. The method combines the advantages of block-matching and optical flow techniques. The first stage employs a standard block-matching algorithm (sum of absolute differences) to provide a displacement estimate with accuracy of up to one pixel. At the second stage, this estimate is corrected by estimating the parameters of a local image transform within a test window. The parameters of the image transform are estimated in the least-square sense. In order to account for typical heart motions, like contraction/expansion, translation and rotation, a local affine model is assumed within the test window. The accuracy of the new algorithm is evaluated using a sequence of 500 grayscale B-mode images, which are generated as distorted, but known copies of an original ROI, taken from a real echocardiogram. The accuracy of the motion estimation is expressed in terms of errors: maximum absolute error, root-mean-square error, average error and standard deviation. The errors of the proposed algorithm are compared with these of the known block-matching technique with cross-correlation and interpolation in the sub-pixel space. Statistical analysis of the errors shows that the proposed algorithm provides more accurate estimates of the heart motion than the crosscorrelation technique with interpolation in the sub-pixel space.
Ultrasonics, 2004
Recently, a spatial compounding ultrasound imaging method was presented that utilizes a conventio... more Recently, a spatial compounding ultrasound imaging method was presented that utilizes a conventional 64-element phased array transducer with two unfocused pistons, each placed at one of the sides of the phased array transducer. This method is augmented here by inclusion of nonlinear filtering of the compounded images. The combined effects of the specific spatial compounding and nonlinear filtering on speckle reduction in the generated ultrasound images are studied and evaluated in two stages: First, the image quality is studied when nonlinear filtering is used as part of the spatial compounding. The study is performed by simulations using the Field II program, by processing several B-mode images of a kidney. The second stage compares the results obtained by the simulations to those obtained by in vitro laboratory experiments. Five different compounding strategies and two nonlinear filters, Gaussian and anisotropic diffusion, are investigated and evaluated in terms of image quality parameters-contrast and signal-to-noise ratio. It is shown that the combination of ''averaging + nonlinear Gaussian filtering'' produces the greatest improvement of image quality. When compared to a conventional phased array imaging system, the spatial compounding method that includes the conventional 64-element phased array transducer with two unfocused pistons, and employs the ''averaging + nonlinear Gaussian filtering'' strategy, obtains improvement in SNR that has reached 334%. Thus, though this method necessitates a somewhat wider probe, it produces significantly improved images.
Medical & Biological Engineering & Computing, 2008
The objective of this study was to validate a recently developed tissue tracking (TT) method for ... more The objective of this study was to validate a recently developed tissue tracking (TT) method for cardiac motion, by comparing it with precise invasive measurements of motion and to prove its capability to reflect moderate hemodynamic changes induced by asynchronous activation. In four open-chest sheep, sono-crystals measured the left ventricle(LV) equator's diameters simultaneously with 2D ultrasound acquisition. The LV was paced either from the posterior or from the lateral wall, just prior to the normal LV activation. Global functional indices were calculated based on the regional motions extracted by the TT method. The correlation coefficient between the shortening of the diameters and the global circumferential strain (GCS) was 0.99 ± 0.004. The peak GCS differentiated between the pacing modes (paired t test, P \ 0.05). The GCS, a measurement closely based on the TT method, followed the precise sono-crystals measurements and reflected moderate hemodynamic changes, thus providing a substantial proof of the TT method's accuracy and clinical value.
Journal of the American Society of Echocardiography, 2004