STUDY ON REAL-TIME MEASUREMENT OF CARDIAC MUSCLE VISCOELASTICITY USING AN ULTRASONIC TACTILE MICROSENSOR CATHETER

该项目的目的是开发一种直径为1.5 mm的触觉传感器导管，配备200 kHz超声微尖，可以实时检测跳动心肌的粘弹性变化。通过改变装载有5 - 100 g各种尺寸的铅片的尖端重量，研究了尖端对物体的接触压力的影响，所述物体是具有40 - 90%的各种硅含量的硅橡胶盘。超声共振频率偏移（Δ f）取决于尖端负载。确定5 g载荷适合于测量软组织，在较软的材料中，负Δ f变得更大。对麻醉犬的肝、肾、脾和肌肉等在体器官的粘弹性测量表明，肌肉的Δ f小于其他组织。骨骼肌、肾脏、肝脏和脾脏的柔软度依次为：通过颈动脉插入导管获得了与左室壁运动相关的动态变化，但是，不能区分源于心室肌粘弹性变化的信号和源于收缩期尖端与室壁碰撞的信号。为此目的，应改进导管。

Aim of the project is to develop a tactile sensor catheter having 1.5 mm in diameter equipped with the 200 kHz ultrasonic microtip that can detect in real-time viscoelasticity change of beating heart muscle. Influence of contact pressure of the tip on the objects which are silicone rubber discs having various silicone contents from 40 to"90 % was studied by varying tip weight loaded with various sizes of lead chips from 5 to 100 g. Ultrasonic resonant frequency shift (DELTAf) depended on the tip load. Five gram load was decided appropriate for measuring soft tissues.The negative DELTAf became bigger in softer material. Viscoelasticity measurements of in vivo organs including liver, kidney, spleen and muscles in anesthetized dogs revealed the DELTAf of muscle was smaller than other tissues. Skeletal muscle, kidney, liver and spleen were softer in order. Dynamic changes associated with the left ventricular wall motion was obtained by the catheter inserted via carotid artery However, the signals originating from viscoelasticity changes of the ventricular muscle and from the tip collision against the ventricular wall in systole cannot be discriminated. Improvement of the catheter should be necessary for this purpose.