Echocardiographic definition of the left ventricular centroid. I. Analysis of methods for centroid calculation from a single tomogram

Abstract

Quantitation of myocardial contraction requires a frame of reference. Most investigators have sought a single reference frame per image, centered in some manner with respect to the mass of myocardium. Because there is no anatomic marker for the center of the heart, many different approaches have been pursued to identify a centroid of the left ventricle. The issue of whether the reference should be fixed throughout the cardiac cycle or float from image to image has been addressed in previous studies, but the more fundamental question of how a centroid can best be defined has not been answered. This study examines this basic issue by analysis of variance from observer to observer, cycle to cycle, animal to animal and method to method. Both endocardial and epicardial borders were digitized twice by each of two observers at 1/30 s intervals spanning the cardiac cycle for each of three cardiac cycles in six normal dogs. The left ventricular centroid was calculated by six methods: center of endocardial coordinates, center of epicardial coordinates, center of mid-myocardial (average) coordinates, center of endocardial area, center of epicardial area and center of mid-myocardial (average) area. The path of each centroid was correlated between observers and correlation coefficients were transformed for analysis of variance. This analysis indicates a best approach to centroid definition through distinct minimization of the variance: the best of the six methods proved to be center of endocardial area.

Quantitative Three-Dimensional Wall Motion Analysis Predicts Ischemic Region Size and Location

“…While ejection fraction is a valuable quantitative measure of global left ventricular (LV) function, standard echocardiographic assessment of regional LV function (wall motion analysis) remains qualitative, primarily because quantitative analysis of LV wall motion has been limited by technical issues such as the well-known problem of centroid definition 21, 31. The overall goal of our work is therefore to develop robust methods for quantification of LV wall motion.…”

“…Our novel technique takes advantage of the entire 3D geometry of the heart visible in RT3DE as opposed to individual slices through the image, allowing for continuous measurement of wall motion throughout the entire LV rather than at a few discrete locations. However, the most important advantage of RT3D for this work was the fact that the entire LV is visible in the image, enabling new solutions to the problem of defining a centroid as a reference system for wall motion analysis 21, 31. Using anatomical landmarks that are less affected by regional wall motion abnormalities than a centroid, such as the center of the mitral valve orifice, to register the position of the endocardial surface through time has been shown to be more reliable than selecting a centroid 4.…”

“…Visual analysis provides little quantitative information, is dependent on the level of experience of the observer23, 29, and is subject to high inter-observer variability8. Quantitative analysis of cardiac images provides a more objective and accurate approach to diagnosis 16; unfortunately, quantitative analysis of left ventricular wall motion has been limited by technical issues, particularly the well-known problem of centroid definition 21, 31.…”

Quantitative Assessment of Short Axis Wall Motion Using Myocardial Strain Rate Imaging

“…Two‐dimensional echocardiography provides tomographic views of the left ventricle and is used for assessing regional wall motion. Although there are many echocardiographic methods to assess wall motion, 8–11 the most widely used technique is a qualitative one based on the recommendations of the American Society of Echocardiography 7 . In this method, a numeric scoring system has been adopted based on the contractility of the individual segments (1 = normal; 2 = hypokinesis; 3 = akinesis; 4 = dyskinesis) and a global wall motion score index is derived by dividing the sum of wall motion scores by the number of visualized segments.…”

Parameterization of Left Ventricular Wall Motion for Detection of Regional Ischemia

“…15 Two primary barriers to successful quantitative wall motion analysis have been the need to manually trace the endocardial border 4 and difficulty in defining an appropriate centroid for 2D segmental wall motion analysis. 13,19 Recently, real-time three-dimensional (RT3D) ultrasound has been hailed for its ability to simultaneously reduce acquisition time and improve visualization of the left ventricle during stress echocardiography. 21 However, another advantage of this new technology has received less attention: the true 3D nature of the data will enable more robust solutions to the classic problems of segmentation and registration.…”