Helene Houle

Characterization and Quantification of Vortex Flow in the Human Left Ventricle by Contrast Echocardiography Using Vector Particle Image Velocimetry

OBJECTIVES The aims of this study were to: 1) assess the feasibility of left ventricular (LV) vortex flow analysis using contrast echocardiography (CE); and 2) characterize and quantify LV vortex flow in normal subjects and patients with LV systolic dysfunction. BACKGROUND Vortices that form during LV filling have specific geometry and anatomical locations that are critical determinants of directed blood flow during ejection. Therefore, it is clinically relevant to assess the vortex flow patterns to better understand the LV function. METHODS Twenty-five patients (10 normal and 15 patients with abnormal LV systolic function) underwent CE with intravenous contrast agent, Definity (Bristol-Myers Squibb Medical Imaging, Inc., North Billerica, Massachusetts). The velocity vector and vorticity were estimated by particle image velocimetry. Average vortex parameters including vortex depth, transverse position, length, width, and sphericity index were measured. Vortex pulsatility parameters including relative strength, vortex relative strength, and vortex pulsation correlation were also estimated. RESULTS Vortex depth and vortex length were significantly lower in the abnormal LV function group (0.443 +/- 0.04 vs. 0.482 +/- 0.06, p < 0.05; 0.366 +/- 0.06 vs. 0.467 +/- 0.05, p < 0.01, respectively). Vortex width was greater (0.209 +/- 0.05 vs. 0.128 +/- 0.06, p < 0.01) and sphericity index was lower (1.86 +/- 0.5 vs. 3.66 +/- 0.6, p < 0.001) in the abnormal LV function group. Relative strength (1.13 +/- 0.4 vs. 2.10 +/- 0.8, p < 0.001), vortex relative strength (0.57 +/- 0.2 vs. 1.19 +/- 0.5, p < 0.001), and vortex pulsation correlation (0.63 +/- 0.2 vs. 1.31 +/- 0.5, p < 0.001) were significantly lower in the abnormal LV function group. CONCLUSIONS It was feasible to quantify LV vorticity arrangement by CE using particle image velocimetry in normal subjects and those with LV systolic dysfunction, and the vorticity imaging by CE may serve as a novel approach to depict vortex, the principal quantity to assess the flow structure.

Definitions for a common standard for 2D speckle tracking echocardiography: consensus document of the EACVI/ASE/Industry Task Force to standardize deformation imaging.

Recognizing the critical need for standardization in strain imaging, in 2010, the European Association of Echocardiography (now the European Association of Cardiovascular Imaging, EACVI) and the American Society of Echocardiography (ASE) invited technical representatives from all interested vendors to participate in a concerted effort to reduce intervendor variability of strain measurement. As an initial product of the work of the EACVI/ASE/Industry initiative to standardize deformation imaging, we prepared this technical document which is intended to provide definitions, names, abbreviations, formulas, and procedures for calculation of physical quantities derived from speckle tracking echocardiography and thus create a common standard.

Patient-Specific Modeling and Quantification of the Aortic and Mitral Valves From 4-D Cardiac CT and TEE

As decisions in cardiology increasingly rely on noninvasive methods, fast and precise image processing tools have become a crucial component of the analysis workflow. To the best of our knowledge, we propose the first automatic system for patient-specific modeling and quantification of the left heart valves, which operates on cardiac computed tomography (CT) and transesophageal echocardiogram (TEE) data. Robust algorithms, based on recent advances in discriminative learning, are used to estimate patient-specific parameters from sequences of volumes covering an entire cardiac cycle. A novel physiological model of the aortic and mitral valves is introduced, which captures complex morphologic, dynamic, and pathologic variations. This holistic representation is hierarchically defined on three abstraction levels: global location and rigid motion model, nonrigid landmark motion model, and comprehensive aortic-mitral model. First we compute the rough location and cardiac motion applying marginal space learning. The rapid and complex motion of the valves, represented by anatomical landmarks, is estimated using a novel trajectory spectrum learning algorithm. The obtained landmark model guides the fitting of the full physiological valve model, which is locally refined through learned boundary detectors. Measurements efficiently computed from the aortic-mitral representation support an effective morphological and functional clinical evaluation. Extensive experiments on a heterogeneous data set, cumulated to 1516 TEE volumes from 65 4-D TEE sequences and 690 cardiac CT volumes from 69 4-D CT sequences, demonstrated a speed of 4.8 seconds per volume and average accuracy of 1.45 mm with respect to expert defined ground-truth. Additional clinical validations prove the quantification precision to be in the range of inter-user variability. To the best of our knowledge this is the first time a patient-specific model of the aortic and mitral valves is automatically estimated from volumetric sequences.

Two‐ and Three‐Dimensional Speckle Tracking Echocardiography: Clinical Applications and Future Directions

Two‐dimensional speckle tracking echocardiography (2D STE) is a novel technique of cardiac imaging for quantifying complex cardiac motion based on frame‐to‐frame tracking of ultrasonic speckles in gray scale 2D images. Two‐dimensional STE is a relatively angle independent technology that can measure global and regional strain, strain rate, displacement, and velocity in longitudinal, radial, and circumferential directions. It can also quantify rotational movements such as rotation, twist, and torsion of the myocardium. Two‐dimensional STE has been validated against hemodynamics, tissue Doppler, tagged magnetic resonance imaging, and sonomicrometry studies. Two‐dimensional STE has been found clinically useful in the assessment of cardiac systolic and diastolic function as well as providing new insights in deciphering cardiac physiology and mechanics in cardiomyopathies, and identifying early subclinical changes in various pathologies. A large number of studies have evaluated the role of 2D STE in predicting response to cardiac resynchronization therapy in patients with severe heart failure. However, the clinical utility of 2D STE in the above mentioned conditions remains controversial because of conflicting reports from different studies. Emerging areas of application include prediction of rejection in heart transplant patients, early detection of cardiotoxicity in patients receiving chemotherapy for cancer, and effect of intracoronary injection of bone marrow stem cells on left ventricular function in patients with acute myocardial infarction. The emerging technique of three‐dimensional STE may further extend its clinical usefulness.

Echocardiographic particle image velocimetry: a novel technique for quantification of left ventricular blood vorticity pattern.

BACKGROUND In this study, the functionality of echocardiographic particle imaging velocimetry (E-PIV) was compared with that of digital particle imaging velocimetry (D-PIV) in an in vitro model. In addition, its capability was assessed in the clinical in vivo setting to obtain the ventricular flow pattern in normal subjects, in patients with dilated cardiomyopathy, and in patients with mechanical and bioprosthetic mitral valves. METHODS A silicon sac simulating the human left ventricle in combination with prosthetic heart valves, controlled by a pulsed-flow duplicator, was used as the in vitro model. Particle-seeded flow images were acquired (1) using a high-speed camera from the mid plane of the sac, illuminated by a laser sheet for D-PIV, and (2) using a Siemens Sequoia system at a frame rate of 60 Hz for E-PIV. Data analysis was performed with PIVview software for D-PIV and Omega Flow software for E-PIV. E-PIV processing was then applied to contrast echocardiographic image sets obtained during left ventricular cavity opacification with a lipid-shelled microbubble agent to assess spatial patterns of intracavitary flow in the clinical setting. RESULTS The velocity vectors obtained using both the E-PIV and the D-PIV methods compared well for the direction of flow. The streamlines were also found to be similar in the data obtained using both methods. However, because of the superior spatial resolution of D-PIV, some smaller scale details were not revealed by E-PIV. The application of E-PIV to the human heart resulted in reproducible flow patterns in echocardiographic images taken within different time frames or by independent examiners. CONCLUSIONS The E-PIV technique appears to be capable of evaluating the major flow features in the ventricles. However, the bounded spatial resolution of ultrasound imaging limits the small-scale features of ventricular flow to be revealed.

Effect of cardiac resynchronization therapy on longitudinal and circumferential left ventricular mechanics by velocity vector imaging: description and initial clinical application of a novel method using high-frame rate B-mode echocardiographic images.

Cardiac resynchronization therapy (CRT) has emerged as an important method to treat patient with symptomatic heart failure with evidence of intraventricular dyssynchrony. Tissue Doppler imaging by echocardiography has been shown to be an excellent tool for the assessment of mechanical left ventricular dyssynchrony and the selection of patients for CRT. However, there are some patients who do not show symptomatic improvement following CRT. One possible explanation for this is the need to optimize not only longitudinal synchrony, but also improve the circumferential and radial dynamics of the left ventricle. Doppler imaging does not allow reliable assessment of the latter because of the angle‐dependency of the technique. Velocity Vector Imaging (VVI) is a newer technique which is angle‐independent and thus provides an avenue to evaluate short‐axis mechanics of the left ventricle. We describe a case in which VVI was used to assess the left ventricular dynamics in a patient with heart failure who did not respond to CRT. (ECHOCARDIOGRAPHY, Volume 22, November 2005)

Automated quantitative 3-dimensional modeling of the aortic valve and root by 3-dimensional transesophageal echocardiography in normals, aortic regurgitation, and aortic stenosis: comparison to computed tomography in normals and clinical implications.

Background—We tested the ability of a novel automated 3-dimensional (3D) algorithm to model and quantify the aortic root from 3D transesophageal echocardiography (TEE) and computed tomographic (CT) data. Methods and Results—We compared the quantitative parameters obtained by automated modeling from 3D TEE (n=20) and CT data (n=20) to those made by 2D TEE and targeted 2D from 3D TEE and CT in patients without valve disease (normals). We also compared the automated 3D TEE measurements in severe aortic stenosis (n=14), dilated root without aortic regurgitation (n=15), and dilated root with aortic regurgitation (n=20). The automated 3D TEE sagittal annular diameter was significantly greater than the 2D TEE measurements (P=0.004). This was also true for the 3D TEE and CT coronal annular diameters (P<0.01). The average 3D TEE and CT annular diameter was greater than both their respective 2D and 3D sagittal diameters (P<0.001). There was no significant difference in 2D and 3D measurements of the sinotubular junction and sinus of valsalva diameters (P>0.05) in normals, but these were significantly different (P<0.05) in abnormals. The 3 automated intercommissural distance and leaflet length and height did not show significant differences in the normals (P>0.05), but all 3 were significantly different compared with the abnormal group (P<0.05). The automated 3D annulus commissure coronary ostia distances in normals showed significant difference between 3D TEE and CT (P<0.05); also, these parameters by automated 3D TEE were significantly different in abnormal (P<0.05). Finally, the automated 3D measurements showed excellent reproducibility for all parameters. Conclusions—Automated quantitative 3D modeling of the aortic root from 3D TEE or CT data is technically feasible and provides unique data that may aid surgical and transcatheter interventions.

A Suggested Roadmap for Cardiovascular Ultrasound Research for the Future

Sanjiv Kaul, MD, FASE,* James G. Miller, PhD,* Paul A. Grayburn, MD, Shinichi Hashimoto,Mark Hibberd, MD, PhD, Mark R. Holland, PhD, FASE, Helene C. Houle, BA, RDMS, RDCS, RVT, FASE,Allan L. Klein, MD, FASE, Peg Knoll, RDCS, FASE, Roberto M. Lang, MD, FASE,Jonathan R. Lindner, MD, FASE, Marti L. McCulloch, RDCS, FASE, Stephen Metz, PhD,Victor Mor-Avi, PhD, FASE, Alan S. Pearlman, MD, FASE, Patricia A. Pellikka, MD, FASE, Nancy DeMarsPlambeck,BS,RDMS,RDCS,RVT,DavidPrater,MS, ThomasR.Porter,MD,FASE,DavidJ.Sahn,MD,FASE,James D. Thomas, MD, FASE, Kai E. Thomenius, PhD, and Neil J. Weissman, MD, FASEINTRODUCTIONThe leadership at the American Society of Echocardiography (ASE)decided on a proactive role in defining selected areas of researchnecessary in this decade that will meet our future clinical needs.Consequently, ASE sponsored a Technology and ResearchSummit in the fall of 2010 in conjunction with the AmericanHeart Association Scientific Sessions in Chicago. In addition to theASE executive committee, in attendance were the editor, deputyeditor, and one of the associate editors of the Journal of theAmerican Society of Echocardiography. Also invited were physician-scientists active in the field of cardiovascular ultrasound, respectedultrasound physicists, and senior engineers from the various ultra-sound companies.The agenda for the full-day meeting covered a selected range ofsubjects including the assessment of global and regional left ventricu-lar function, regional myocardialperfusion, molecular imaging, thera-peutic ultrasound, and peripheral vascular imaging. Also addressedwere research necessary to determine the broad clinical utility ofhand held ultrasound devices and the impact of future technologicaldevelopments on the field of cardiovascular imaging.Because of time constraints, other important and worthy areas ofresearch were not discussed. There was an hour devoted to the dis-cussion of each subject that was initiated by the chairs and panelistsassigned to each of the topics. The discussion was robust, and at theend, the chairs and panelists for each topic were requested to sub-mit in writing a short synopsis of the discussion. These have beencompiled into a document that we believe will serve as a roadmapfor cardiovascular ultrasound research for this decade. At the endof each section a short list of references for selected reading isprovided.Although we have defined the areas that are ripe for future re-search, we also strongly believe that we havetotrain the future scien-tists who will implement this research agenda. ASE has historicallyawarded one or two fellowship training grants a year and also anaward for researchtraining of a sonographer. At some institutions fel-lowshavealsoreceivedtraininggrantsfromthelocalAmericanHeartAssociation, and very occasionally a training grant (F32) from theNational Institutes of Health. However, this is not enough. We needmore institutional training grants from the National Institutes ofHealth in order to train an adequate number of MD and PhD scien-tists in cardiovascular imaging. To our knowledge there are currentlyonlyahandfulofsuchtraininggrantsinthecountry,whichiswoefullyinadequate. We believe that we need at least 20–25 such traininggrants devoted to the general field of cardiovascular imaging so thatwithin a decade there will be enough physicians trained in scientificmethods and clinical research to address the subjects that havebeen discussed in this report.The field of cardiovascular ultrasound is very broad, ranging fromclinical validation of new technology to studies requiring knowledgeof physics, mathematics, organic chemistry, physiology, pharmacol-ogy, molecular and vascular biology, genetics, clinical trials, and out-come research. Cross-training of individuals in one or more of thesefields is essential for cardiovascular ultrasound to thrive and succeed.Ourhopeisthatthisreportwillencourageyoungpeopletorealizethescope of cardiac ultrasound research and make a career in this dy-namic field.Selected Reading

Two-dimensional speckle tracking echocardiography: Standardization efforts based on synthetic ultrasound data

AIMS 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). METHODS AND RESULTS 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%. CONCLUSION 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 deformation imaging. This study was an important first step in the development of generally accepted tools for QA of speckle tracking echocardiography.

Right ventricle three-dimensional echography in corrected tetralogy of fallot: accuracy and variability

AIMS To evaluate right ventricular (RV) volume and ejection fraction (EF) in adult normal subjects and repaired tetralogy of Fallot (ToF) with 3D trans-thoracic echocardiography (3DE) and a semi-automatic border detection algorithm. METHODS AND RESULTS Fourteen healthy volunteers and 20 patients with repaired ToF (mean age 31 +/- 14) underwent 3DE and MRI within the same day. Right ventricular end-systolic volume (ESV) and end-diastolic volume (EDV) and EF were measured by two observers using 3DE and compared with MRI measurements. Intra- and interobserver variability of 3DE and agreement between both methods were evaluated using Bland-Altman analysis. Over or underestimation of 3DE in comparison to MRI was assessed using paired t-test. Intra- and interobserver variability of 3DE was excellent with intraclass coefficient of correlation (ICC) ranging from 0.85 to 0.99 and from 0.85 to 0.98, respectively. Three-dimensional echocardiography underestimated ESV and EDV (P < 0.001) but agreement between 3DE and MRI was excellent (ICC = 0.88 and 0.87, respectively). Ejection fraction was 47.7 +/- 7.8 with 3DE and 47.9 +/- 6.7 with MRI, agreement between both methods was good (ICC = 0.72). CONCLUSION Three-dimensional echocardiography combined to semi-automated quantification software shows fair agreement with MRI for RV volumes and EF measurement in patients with repaired ToF and adequate intra- and interobserver variability. These results suggest applicability for serial follow-up of patients with right heart congenital disease. However, the accuracy of 3DE echo diminishes with larger RV volumes, in part due to current difficulty to include the entire RV in the imaged sector. Technical progress in transducers beam geometry is likely to address this issue.