ULTRASONIC INSTRUMENTATION FOR CARDIOVASCULAR STUDIES

贝勒研发的高频心脏多普勒系统 多年来一直用于研究小动物和病人。 然而，换能器的性能相对较差，可以 通过包括驱动器和接收器特性进一步改进 融入到设计过程中。采用KLM模型对射频进行建模 作为ABCD参数网络的贝勒多普勒系统的组件， 包括源和接收器阻抗、电缆长度和换能器 有源和无源组件。研究了两种活性物质： 传感器组件、PZT 5A(摩托罗拉3195)和改进的导线 钛酸盐(江户EC-97)。活动区域和电缆长度各不相同，以及 对射频电子设备进行了修改，以提供最佳的 多普勒换能器的操作点。 两种活性物质的优化导致面积与 总体最优的灵敏度曲线领先 钛酸盐；然而，由于介电常数较低，最佳的 面积太大，不适用于心脏多普勒测量 老鼠。找到了使用贝勒配置系统的最优设计 为1.6 mm直径的PZT5A换能器。一个330pF的电容器 与射频板上的换能器串联插入以取代 现有跳线，调谐源和接收阻抗接近 实际价值和设计都进行了重新优化。使用这些修改后的 源和接收器阻抗，整体优化换能器设计 确定了对精细多普勒测量仍具有实用价值的 直径2.6 mm的PZT5A换能器与简单的环氧体匹配 层和轻质但结构坚硬的导电衬底 微型气球。 该项目的未来工作包括与 贝勒20 MHz系统及资源PZFlex码在系统中的应用 分析透镜对换能器行为和光束轮廓的影响。

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.