Victor Mor-Avi

The Role of Echocardiographic Harmonic Imaging and Contrast Enhancement for Improvement of Endocardial Border Delineation

Despite advances in imaging technology, many myocardial segments remain poorly visualized with echocardiography; however, both contrast enhancement and harmonic imaging have shown promise for improving endocardial definition. Fifty subjects with technically limited echocardiograms were studied with fundamental and harmonic imaging as well as during echocardiographic contrast injection. Overall endocardial visualization scores improved with both techniques compared with fundamental imaging. Harmonic imaging improved endocardial visualization in 43% of all segments and in 57% of segments nonvisualized with fundamental imaging. The benefit of harmonic imaging was seen in all segments. Contrast echocardiography had similar overall improvements in visualization (42% of all segments, 67% of segments nonvisualized with fundamental imaging) but was not helpful in all regions. Harmonic imaging outperformed contrast in 9 of 22 segments, whereas contrast was superior in 4 of 22. In a subgroup of patients with very poor images, contrast enhancement was superior, with a greater increase in overall score and a higher salvage rate than harmonic (68% vs 40%).

Quantitative analysis of myocardial perfusion and regional left ventricular function from contrast-enhanced power modulation images

Our goal was to test the feasibility of using power modulation, a new echocardiographic imaging technique, for combined quantitative assessment of myocardial perfusion and regional LV function. Coronary balloon occlusions were performed in 18 anesthetized pigs. Images were obtained during iv contrast infusion at baseline, during coronary occlusion and reperfusion, and analyzed using custom software. At each phase, regional myocardial perfusion was assessed by calculating mean pixel intensity and the rate of contrast replenishment following high-power ultrasound impulses. LV function was assessed by calculating regional fractional area change. All ischemic episodes caused delectable and reversible changes in perfusion and function. Perfusion defects were visualized in real time and confirmed by a significant decrease in pixel intensity in the LAD territory following balloon inflation and reduced rate of contrast replenishment. Fractional area change significantly decreased in ischemic segments, and was restored with reperfusion. Power modulation allows simultaneous on-line assessment of myocardial perfusion and regional LV wall motion.

Clinical Applications of Color Kinesis: Facts Versus Hopes

Color Kinesis is a new echocardiographic technique based on acoustic quantification that tracks endocardial motion by color-encoding pixel transitions between blood and myocardial tissue in real time. Color Kinesis generates an integrated display of magnitude and timing of endocardial motion in a single end-systolic or end-diastolic frame, which provides the basis for objective evaluation of regional myocardial performance. In the previous chapter we described the principles of operation of this new technology and the technical guidelines for data acquisition. We also reviewed the methods of segmental analysis of Color Kinesis images which have been developed to allow the quantification of both the magnitude and timing of left ventricular endocardial motion during both systolic ejection and diastolic filling.

Semi-automatic detection and tracking of mitral and aortic annuli from real-time 3D transesophageal echocardiographic images

The recently developed echocardiographic matrix array transesophageal (mTEE) transducer provides real-time 3D images of high spatial and temporal resolution that may be suitable for detailed simultaneous study of functional anatomy of the mitral and aortic valves. We developed software that detects and tracks throughout the cardiac cycle mitral and aortic annuli (MA and AoA) and tested it in 15 patients with normal valves. Following manual initialization of each annulus in 15 planes rotated around the valvepsilas axis, the position of each annulus was tracked using a two-step 3D feature tracking algorithm based on maximum likelihood and Lucas-Kanade optical flow techniques and parameters of valve geometry were automatically measured throughout the cardiac cycle. Frame-by-frame detection and tracking of MA and AoA was possible in all patients. This approach allowed for the first time non-invasive quantitative measurements of the 3D dynamic geometry of normal MA and AoA and their coupling from mTEE data.

Real-time three-dimensional echocardiographic quantification of left ventricular mass: comparison with magnetic resonance imaging

The accuracy of M-mode and 2D echocardiographic measurements of LV mass is limited. We hypothesized that real-time three-dimensional (RT3D) imaging may allow more accurate measurements. LV mass was calculated from 2D and RT3D images obtained in 21 consecutive patients. The RT3D data resulted in LV mass that correlated with cardiac magnetic resonance measurements better (r=0.90) than 2D (r=0.79). The 2D technique underestimated LV mass (bias 39%). RT3D showed only minimal bias (3%), and reduced the interobserver (37% to 7%) and intraobserver (19% to 8%) variability. RT3D imaging provides the basis for accurate and reliable measurement of LV mass.

Color Kinesis: One Step Beyond Acoustic Quantification

Two-dimensional echocardiography is currently the most widely used 1 noninvasive imaging modality for the evaluation of left ventricular function due to its ability to depict myocardial wall motion in real time. Conventional clinical assessment of regional wall motion abnormalities is based on visual interpretation of the magnitude of systolic endocardial excursion and wall thickening. However, this method is highly subjective and skill-dependent, particularly during the interpretation of stress echocardiographic studies. Consequently, variety of quantitative techniques for objective analysis of left ventricular endocardial motion have been developed [1-10]. Prior to the development of acoustic quantification [11-15], these techniques were mostly based on manual off-line frame-by-frame tracing of the myocardial boundaries. Since it is often difficult to accurately define the endocardial and epicardial borders, these time-consuming methods remain subjective and impractical for routine clinical use., Accordingly, a variety of computerized methods of edge detection have been recently developed [8,16-20]. Although automated to a greater extent, these methods still require off-line processing. The development of acoustic quantification provided a partial solution to these difficulties, since it allowed automated detection of the endocardial border, thereby eliminating the need for manual tracing of multiple frames. This method allows real time acquisition of continuous signals reflecting left ventricular cross-sectional area or volume throughout the cardiac cycle [12,13,21]. However, these signals reflect global rather than regional left ventricular performance. The ability to easily assess regional systolic and diastolic function could provide useful information in a variety of clinical states, including coronary artery disease.

Echocardiography and cardiovascular function : tools for the next decade

Preface. 1. The Fundamentals of Acoustic Quantification and Color Kinesis Technology D. Prater. 2. How to Perform an Acoustic Quantification Study: Technical Factors Influencing Study Quality and Pitfalls to Avoid J.E. Bednarz, et al. 3. Comparative and Validation Studies of Echocardiographic On-Line Quantification of Ventricular Dimensions and Systolic Function J.E. Perez. 4. Automated Assessment of Left Ventricular Function With Acoustic Quantification: Signal Averaging Revisited V. Mor-Avi, et al. 5. Evaluation of Left Ventricular Diastolic Function Using Acoustic Quantification S. Gan, R. Popp. 6. Noninvasive Evaluation of Aortic Elastic Properties S.G. Shroff, R.M. Lang. 7. Left Atrial Function: Indirect Hemodynamic Assessment Using Acoustic Quantification A. Waggoner, J. Perez. 8. On-Line Quantification of Cardiovascular Function in Children T. Kimball. 9. Quantitative Intraoperative Echocardiographic Assessment of Ventricular Function J. Gorcsan III. 10. Color Kinesis: One Step Beyond Acoustic Quantification V. Mor-Avi, R.M. Lang. 11. Clinical Applications of Color Kinesis: Facts Versus Hopes V. Mor-Avi, et al. 12. Doppler Myocardial Imaging G.R. Sutherland, et al. Index.

Real-time 3D echocardiographic quantification of left ventricular volumes: Multicenter study for validation with magnetic resonance imaging

Left ventricular (LV) volumes obtained from RT3DE datasets are underestimated compared to cardiac magnetic resonance (CMR). We sought to study the accuracy and reproducibility of this technique in a multicenter setting, the inter-institutional differences in these variables in relationship with investigatorspsila experience, and the potential sources of underestimation. 92 patients underwent CMR and RT3DE imaging at 4 different institutions. End-systolic and end-diastolic LV volumes correlated highly with CMR values (EDV: r=0.91; ESV: r=0.93), but were 29 and 26% lower. This finding was consistent across participating institutions, with the magnitude of bias being related to experience. Exclusion of trabeculae and mitral valve plane from the CMR reference essentially eliminated the inter-modality bias. In conclusion, LV volumes are underestimated in most patients because RT3DE imaging cannot differentiate between the myocardium and trabeculae.

Quantitative assessment of myocardial perfusion using real-time three-dimensional echocardiographic imaging

The new real-time three-dimensional (RT3D) echocardiographic technology offers an opportunity for myocardial perfusion imaging in the entire heart without the need for reconstruction from multiple slices and repeated contrast maneuvers. Our aims were to develop and validate a technique for quantitative volumetric assessment of myocardial perfusion. Studies were conducted in 5 isolated rabbit hearts and in 5 patients with ischemic heart disease. In rabbits, RT3D datasets were acquired over 30 sec, during which infusion of contrast agent definity was initiated and reached steady-state myocardial enhancement. Data were obtained at 3 different levels of coronary flow. At each level, myocardial videointensity (MVI) was measured over time in 3 LV short-axis slices of fixed thickness and peak contrast inflow rate (PCIR) was calculated. Administration of contrast resulted in clearly visible and measurable dynamic changes in MVI. PCIR followed the changes in coronary flow (p<0.0I). Feasibility in humans was tested by imaging the interventricular septum during initiation of infusion of definity at rest and during adenosine infusion. Dynamic changes in MVI were visible and suitable for quantitative analysis. In 2 patients, adenosine resulted in dark regions, reflecting lack of myocardial filling in stenosis-related territories. RT3D imaging and quantification of myocardial perfusion using our algorithm are feasible. This approach can potentially allow more accurate assessment of the extent of perfusion defects than 2D myocardial contrast echocardiography.

Semi-automated quantification of left ventricular volumes and mass from cardiac magnetic resonance images by level set models

Cardiac magnetic resonance imaging (CMRI) is the standard for estimates of LV volumes, ejection fraction and mass. These computations are based on extensive manual tracing of endocardial and epicardial borders and are subjective and time-consuming. We developed a new technique for semi-automated suface detection for the measurement of LV end-systolic and end-diastolic volumes, ejection fraction and mass from CMRI data. This procedure is performed in the 3D domain, and does not rely on geometrical approximations. Twenty-two consecutive patients referred for CMRI were studied. Measurements were compared with the values derived by manual tracing using linear regression and Bland-Altman analyses. For both volumes, ejection fraction and mass, the analysis resulted in high correlation coeflcienrs and depicted no signijkant biases and narrow limits of agreement. The proposed technique is fast and objective and provides accurate measurements of LV volumes, ejection fraction and mass.