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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.

Background-Knowledge of the physical properties of atherosclerotic plaque is essential when evaluating its vulnerability in a clinical setting. Such knowledge, however, is still difficult to obtain with the various approaches developed to date. Methods and Results-This article describes a noninvasive method for evaluating the regional elasticity (the elastic modulus in the circumferential direction) of tissue surrounding atherosclerotic plaque in which a novel phased tracking method is applied to measure minute changes in thickness of each of the multiple layers of the arterial wall during one heartbeat. By comparing the pathological findings with the distribution of elasticity, average elasticity of lipid and that of a mixture of smooth muscle and collagen fiber can be determined. On the basis of these reference parameters, each point is statistically categorized as lipid, mixture, or other. Thus, the plaque is electronically stained using transcutaneous ultrasound. By applying the method to the common carotid arteries, the presence of thin collagen fiber was clarified along the arterial axis for normal subjects, whereas soft inclusion of lipid was found for every plaque in subjects with hyperlipidemia. Conclusion-This

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In basic experiments employing silicone rubber tubes with nonuniform wall thickness as arterial models, the elastic moduli of silicone rubber tubes were evaluated by measuring changes in wall thickness. These results confirm the value of the proposed method.