Advanced Micromachined Ultrasonic Transducers for High Performance Medical Imaging Systems

乳腺癌是女性死亡的主要原因，往往未被发现和诊断不足，导致超过21%的女性癌症死亡[加拿大癌症协会统计2017]。在所有诊断技术中，磁共振成像提供了对肿瘤大小的更准确的估计。然而，它的成本、可及性差以及一些植入医疗器械的患者不适用的性质限制了它的使用。因此，迫切需要开发一种准确、安全和低成本的系统，使世界各地更多的妇女能够更频繁地获得检查程序。*先进的超声成像系统由于其非电离和非侵入性以及较低的成本，正在成为常规临床实践中必不可少的实用工具。这些超声系统的关键部件是超声换能器，而电容式微机械超声换能器(CMUT)是一种很有前途的超声成像技术。*这些换能器将先进的微电子机械系统(MEMS)制造技术引入超声成像领域，克服了许多块状压电换能器的制造局限性。它们提供批量生产，从而降低了成本、严格的参数规格、较宽的带宽和可实现的CMOS集成。然而，它们在输出声压、发射和接收模式之间的性能折衷以及对高偏置电压的要求方面尤其不足。*与传统的MEMS换能器不同，本研究计划的重点是一种创新的微机械换能器配置，其中在CMUT单元结构中使用了多个可偏转板。统一的主题是利用两个或更多振动膜在发射和接收超声波信号方面所提供的独特机会。为了实现这一目标，将开发全面的分析和数值模型；将优化多个振动板的物理性能；将评估各种制造技术以及封装；将制造原型器件；将探索阵列配置并将分析这些换能器的电学和声学特性。这项研究计划旨在解决传统CMUT的许多独特问题，包括提供不同模式之间的动态切换、增强输出压力和降低驱动电压。*该计划的广泛应用提供了许多有吸引力的应用，包括为加拿大人提供增强医疗保健的诊断成像和治疗应用。培训具有多种技能的高素质人员是这项研究提案的基本组成部分，它将使加拿大的私营和公共部门受益。

Breast cancer is a leading cause of death in women that is often undetected and underdiagnosed, contributing to the significant death rate of more than 21% of all female cancer deaths [Canadian Cancer Society Statistics 2017]. Amongst all diagnostic techniques, magnetic resonance imaging provides a more accurate estimate of tumor size. However, its cost, poor accessibility and inapplicable nature for patients with some implanted medical devices restrain its usage. Therefore, there is a momentous need to develop an accurate, safe and low-cost system that makes the examination procedure more frequently available to a larger portion of women across the world. ***Advance ultrasound imaging systems are emerging as essential and practical tools in routine clinical practices due to their nonionizing and noninvasive nature and lower cost. The crucial component of these ultrasound systems is the ultrasonic transducer and a promising candidate technology to advance state-of-the-art ultrasound imaging is capacitive micromachined ultrasonic transducer, CMUT. ***These transducers bring advanced microelectromechanical system (MEMS) fabrication technology to the field of ultrasound imaging and overcome the fabrication limitations of many bulk piezoelectric transducers. They offer batch production, which reduces the cost, tight parameter specification, wide bandwidth and achievable CMOS integration. However, they fall short particularly with output acoustic pressure, performance compromise between transmitting and receiving modes and their demand for high bias voltage. ***In this research program and in contrast with traditional MEMS transducers, the focus is on an innovative micromachined transducer configuration where more than one deflectable plate is employed in the CMUT cell structure. The unifying theme is to exploit the unique opportunity given by contribution of two or more vibrating membranes in transmitting and receiving ultrasonic signals. To reach this goal comprehensive analytical and numerical model will be developed; physical properties of multiple vibrating plates will be optimized; various fabricating techniques as well as packaging will be assessed; prototype devices will be fabricated; array configurations will be probed and electrical and acoustic properties of these transducers will be analyzed. This research program is designed to address many of unique concerns of conventional CMUTs including providing dynamic switching between different modes, enhancing output pressure and lowering the driving voltage.***The wide implication of this program offers many attractive applications including diagnostic imaging and therapeutic applications that provide enhanced health care to Canadian. Training of highly qualified personnel with a diverse set of skills is the essential component of this research proposal that will benefit Canadian private and public sectors.