DEVELOPMENT OF WIDEBAND TRANSDUCERS FOR MEDICAL IMAGING

本研究的主要目标是设计、构建和测试一种新的 一类宽带、非共振、高效超声压电 基于现代材料的传感器。根据初步结果， 所提出的设计能够在1到10的频率范围内工作 MHZ仅使用一个扫描头。传感器将设计用于 临床上有用的频率，并将适合与 市售的超声波机器。相比于常规 压电陶瓷或复合换能器设计，其中， 带宽由有源元件的厚度谐振频率控制 元件，本设计将采用非谐振换能器结构。这将 通过使用PVDF聚合物作为活性压电材料来实现。 这种材料非常适合制造新型超声换能器 其带宽至少是用常规方法获得的带宽的两倍 （带宽有限）由压电陶瓷制成的探头。特别是， 所提出的设计利用多层方法， 带宽由最薄的有源PVDF膜和 灵敏度与活性聚合物层的数量成比例。在 在这种方法中，换能器将在低于其谐振的情况下工作 频率，并将进行优化，以涵盖相关的临床成像 频率带宽从1到10 MHz。这样的设计将允许带宽 同时，它还将提供一个整体的敏感性。 与传统压电材料的性能相当。这 带宽增强提供了改善的图像信噪比 分析，例如基于分裂频谱处理方法的分析， 以及具有光谱冗余的组织散射体分析。此外，广 带宽换能器将允许改进的超声组织 利用基于倒谱的去卷积进行表征。此外，本发明还提供了一种方法， 增加的带宽将减少频率复合中的斑点噪声 成像方法。宽带的另一个立即有用的方面 换能器是允许频率变化的传统窄 频带操作而不改变换能器。这种能力在 并且对于临床便利性是期望的， probes.宽带脉冲回波技术发展的最终目标 聚合物传感器是接口，它与现代超声诊断 并且具有能够改善组织表征的组件 仅使用一个扫描头在临床相关频率下。

The primary goals of this research are to design, construct and test a new class of wide-band, non-resonant, high efficiency ultrasound piezoelectric transducers based on modern materials. Based on the preliminary results, the design proposed is capable of operating in the frequency range 1 to 10 MHZ using one scan head only. The transducers will be designed for clinically useful frequencies and will be suited to interface with commercially available ultrasound machines. In contrast to conventional piezoelectric ceramic or composite transducer design in which the bandwidth is controlled by the thickness resonance frequency of the active element, this design will use non-resonant transducer structure. This will be achieved by using PVDF polymer as an active piezoelectric material. This material is well suited to fabricate novel ultrasound transducers with at least twice the bandwidth as that obtained with conventional (bandwidth limited) probes made of piezoelectric ceramics. In particular, the proposed design makes use of a multi-layer approach in which the bandwidth is determined by the thinnest active PVDF film and the sensitivity is proportional to the number of active polymer layers. In such an approach, the transducer will operate well below its resonance frequency and will be optimized to cover the relevant clinical imaging frequency bandwidth from 1 to 10 MHz. Such design will allow bandwidth enhancement and, at the same time, will provide overall sensitivity on a par with that available with conventional piezoelectric materials. This bandwidth enhancement provides improve signal-to-noise ration in image analyses, such as those based on the Split Spectrum Processing Approach, and tissue scatterer analysis with spectral redundancy. Furthermore, wide bandwidth transducers will allow improved ultrasound tissue characterization utilizing cepstrum based deconvolution. In addition, increased bandwidth will reduce speckle noise in the frequency compounding method of imaging. Another immediately useful aspect of wide bandwidth transducers is the allowance of frequency changes for conventional narrow band operation without changing the transducer. This ability is needed in intracavitary probes and is desirable for clinical convenience with all probes. The ultimate goal of the development of the wide-band pulse-echo polymer transducer is to interface it with modern ultrasound diagnostic machines and have an assembly capable of improve tissue characterization at clinically relevant frequencies using only one scanhead.