ULTRASONIC INSTRUMENTATION FOR CARDIOVASCULAR STUDIES

贝勒大学开发的高频心脏多普勒系统 多年来一直被用于研究小动物和病人。 然而，换能器的性能相对较差，并且可能 通过包括驱动器和接收器特性 设计过程中。 采用KLM模型对RF进行建模 贝勒多普勒系统的组件作为ABCD参数网络， 包括源和接收器阻抗、电缆长度和换能器 有源和无源组件。 研究了两种活性材料， 换能器组件、PZT 5A（Motorola 3195）和改良电极导线 钛酸酯（Edo EC-97）。 活动区域和电缆长度各不相同， 对RF电子设备进行了修改，以提供最佳的 多普勒传感器的操作点。 两种活性材料的优化导致面积与 灵敏度曲线，在电极导线中实现了整体最佳效果 钛酸盐;然而，由于低介电常数， 面积太大，无法进行心脏多普勒测量， 小鼠 采用Baylor组态系统进行了优化设计 直径为1.6mm的PZT 5A换能器。 一个330 pF的电容器 与RF板上的换能器串联插入， 现有跳线，将源和接收阻抗调谐到接近 真实的值，并重新优化设计。 使用这些修饰 源和接收器阻抗，整体最佳换能器设计 这仍然是实用的精细多普勒测量确定 直径为2.6mm的PZT 5A传感器，具有简单的环氧树脂匹配 层和轻质但结构刚性的导电背衬 微型气球 该项目的未来工作包括类似的程序， Baylor 20 MHz系统以及Resource PZFlex代码在 分析透镜对传感器性能和光束轮廓的影响。

The high frequency cardiac Doppler system developed at Baylor has been used for many years for studying small animals and patients. However, the performance of the transducers is relatively poor and can be further improved by including driver and receiver characteristics into the design process. The KLM model was employed to model the RF components of the Baylor Doppler system as an ABCD parameter network, include source and receiver impedances, cable lengths and transducer active and passive components. Two active materials were studied as transducer components, a PZT 5A (Motorola 3195) and a modified lead titanate (Edo EC-97). Active areas and cable lengths were varied, and modifications were made to the RF electronics to provide an optimum operation point for the Doppler transducers. Optimization of the two active materials lead to area versus sensitivity curves with an overall optimum achieved in the lead titanate; however because of the low dielectric constant, the optimal area was too large to be practical for cardiac Doppler measurements on mice. The optimum design using the Baylor configured system was found to be a 1.6mm diameter PZT5A transducer. A 330pF capacitor was inserted in series with the transducer on the RF board replacing an existing jumper, tuning the source and receive impedances to nearly real values and the designs were re-optimized. Using these modified source and receiver impedances, the overall optimum transducer design which remained practical for fine Doppler measurements was determined to be a 2.6mm diameter PZT5A transducer with a simple epoxy matching layer and a light, but structurally rigid backing of conductive micro-balloons. Future work on this project include a similar procedure with the Baylor 20 MHz system as well as application of Resource PZFlex code to analyze lens effects on transducer behavior and beam profiles.