Ultrasonic noninvasive measurement of elastic properties of arterial wall in atherosclerosis

1. 测量动脉壁厚我们提出了三种超声回波信号处理方法来获得动脉壁厚度，从而利用超声测量动脉的弹性特性。通过计算机模拟和体外实验验证了方法的准确性。当超声频率为5 MHz时，回波光谱分析测厚精度优于5微米，最小可测厚度约为0.3 mm。血管内超声换能器的研制研制了一种用于测量主动脉区域弹性的血管内超声换能器。传感器由PZT元件、定位元件的Ni-Ti软丝和测量血压的导管组成，可同时获得动脉杨氏模量的四个参数；即动脉直径、脉宽变化、动脉壁厚度和脉压。在狗的体内实验中发现，主动脉的杨氏模量随着与外周距离的增加而逐渐增加。动脉弹性的临床测量对70例健康人、31例冠心病患者和36例高血压患者进行了腹主动脉压力应变弹性模量的无创测量。在患者组中发现弹性模量的显著增加表明该技术有望早期检测动脉粥样硬化。本项目未来发展方向一是临床应用血管内超声换能器对动脉粥样硬化进行准确检查，二是早期无创检测与年龄相关的动脉粥样硬化改变。

1. Measurement of arterial wall thicknessWe proposed three kinds of signal processings on an ultrasonic echo for obtaining arterial wall thickness to measure elastic properties of the artery using ultrasound.Accuracy of methods was examined by computer simlation and by in vitro experiments. The thickness measurement by spectral analysis of the echo attained the accuracy of better than 5 micron and minimum detectable thickness of about 0.3 mm, when ultrasound of 5 MHz was used.2. Development of intravascular ultrasonic transducerAn intravascular ultrasonic transducer for measuring regional elasticity along the aorta was developed. The transducer consists of PZT element, a flexible Ni-Ti wire for positioning the element and a catheter for blood pressure measurement, so as to obtain simultaneously four parameters concerning Young's modulus of the artery; i.e., diameter of the artery, pulsatile diameter change, artyerial wall thickness and pulse pressure. The progressive increase in Young's modulus of the aorta with distance to peripherals was found in in vivo experiments performed on dogs.3. Clinical measurement of arterial elasticityPressure strain elastic modulus of the abdominal aorta was noninvasively measured in 70 healthy subjects, 31 patients with coronary artery disease, and 36 patients with hypertension. Significant increase of the elastic modulus found in the patient groups shows promise of early detection of atherosclerosis by this technique.4. Future progress of this projectOne future development of this project is clinical application of the intravascular ultrasonic transducer for an accurate examination of atherosclerosis, and the other is nonivasive detection ofage-related atherosclerotic change of the artery at an early stage.