Noninvasive evaluation of local myocardial thickening and its color-coded imaging

Abstract

For t h e noninvasive diagnosis of heart disease based on t h e acoustic characteristics of t h e h e a r t muscle, we have developed a new m e t h o d for accurately tracking t h e movement of t h e heart wall. By this method, a velocity signal of t h e h e a r t wall with a small amplitude of less t h a n 10 p m on t h e motion resulting from a h e a r t b e a t with large amplitude of 10 m m can be successfully detected with sufficient reproducibility in t h e frequency range up t o several hundred H e r t z continuously for periods of a b o u t 10 heartbeats. In this paper, t h e m e t h o d is applied t o multiple points preset in t h e left ventricular (LV) wall along t h e ultrasonic b e a m so t h a t t h e spatial ( d e p t h ) distributions of t h e velocity at these points are simultaneously obtained.T h e motion of t h e heart wall is divided into t h e following two components: parallel global motion of t h e heart wall a n d the change in myocardial layer thickening at each d e p t h across t h e LV wall during myocardial contraction/relaxation.T h e latter component is superimposed on t h e M (motion)mode image using a color code t o m a p contraction as red and expansion as blue. By preliminary human studies, t h e principle of t h e m e t h o d proposed in this paper is verified a n d t h e frequency band of t h e components generated by thickening a n d / o r thinning in t h e myocardium is identified. This new approach offers potential for research on noninvasive acoustical diagnosis of myocardial local motility, t h a t is, t h e myocardial layer function at each d e p t h in t h e ventricular wall.

Elasticity Imaging of Atheroma With Transcutaneous Ultrasound

“…14 Such a minute change in thickness cannot be measured by any other method. This method has already been applied to the in vivo detection of regional instantaneous displacement and change in thickness, with sufficient reproducibility, in the interventricular septum 12,13,15 and in the common carotid artery (CCA). 16 …”

“…12,13 The lowest value of the change in thickness was validated as being Ϸ0.5 m by expanding a rubber plate in a water tank. 14 Such a minute change in thickness cannot be measured by any other method.…”

“…., N m ) as being between two contiguous points, n and nϩ1, along each beam. For measurement of change in thickness of each of the N m layers, the instantaneous depth x m,n (t) of the nth point along the mth beam was simultaneously tracked by applying the phased tracking method 12,13 to the received ultrasound. The minute decrease of several tenths of a micrometer in wall thickness of the nth layer resulting from the arrival of the pressure wave at the beginning of the ejection period was determined by ⌬h m,n (t)ϭx m,nϩ1 (t)Ϫx m,n (t)Ϫh 0 .…”

Phase-Sensitive 2D Motion Estimators Using Frequency Spectra of Ultrasonic Echoes

“…Functional ultrasound imaging, such as vascular elastography [1][2][3][4][5] and myocardial contractility imaging [6][7][8][9], has shown to be useful for diagnosis of the cardiovascular system. Recently, high-frame-rate ultrasound has gained attention because it enhances such functional imaging by measurements of tissue dynamics at a very high frame rate of over one hundred Hz.…”

Viscoelasticity measurement of heart wall in in vivo

“…1A. For all of the multiple points preset at 75-µm intervals in the heart wall along 16 ultrasonic beams, the vibrations were simultaneously measured as a waveform with a sampling frequency of 450 Hz for the first time by the newly developed phased tracking method [23], [24]. Figure 1B shows a typical example of the vibrations on both sides-the right ventricular (RV) side and left ventricular (LV) side-of the interventricular septum (IVS) for the subject in Fig.…”