MR-guided capacitive micromachined ultrasonic transducer for liver tumor ablation

描述(申请人提供)：间歇性结直肠癌(CRC)是美国男性和女性癌症死亡的第三大原因。未经治疗的转移性结直肠癌只有8%的5年生存率，而治疗将这一生存率提高到30%-35%(美国癌症协会统计2004年)。然而，只有20%的结直肠癌肝转移患者适合切除。这推动了治疗性非侵入性治疗选择的发展。在这个项目中，我们将开发一种用于治疗上腹部器官恶性肿瘤的高强度聚焦超声(HIFU)探头。虽然传统上用于治疗探头的是压电换能器，但这项技术在制造、可靠性和过热方面往往存在困难。我们建议将电容式微机械超声换能器(CMUT)用于HIFU。CMUT不仅易于使用标准硅加工技术制造，提供了一种经济高效的替代方案，而且还具有制造灵活性和与电子设备直接集成等优势。这些优点使治疗阵列能够更灵活和可重新配置，以通过组织层进行复杂的波束成形。此外，由于CMUT不是谐振结构，因此它们具有优异的带宽和效率。虽然成像CMUT表现出了优异的性能，但专门为HIFU设计的CMUT还没有被设计出来。本项目旨在设计和开发一种CMUT HIFU探头原型，该探头设计用于MR引导下的肝肾癌热疗。更具体地说，我们的目标是：(1)设计和制造专门用于HIFU的测试CMUTS换能器；这些测试换能器将使我们能够修改我们的设计并改进我们的有限元模型，以提高换能器的性能和可靠性。(2)设计、制造和封装用于磁共振扫描仪的环形CMUT HIFU探头和电子系统；该探头的束流分布和可靠性将根据需要进行测量和改进。(3)制作最终的CMUT探头，包装后用于磁共振扫描仪。这种探头将被集成在MR制导系统中，并与传统的压电器件进行比较。完成后，该项目将开发出一种CMUT HIFU探头，能够在磁共振引导下治疗癌症，并将准备好进行体内测试。该项目的成功将大大增加80%的结直肠癌和上腹部癌患者的治疗选择，这些患者不适合切除，从而降低发病率和死亡率。

DESCRIPTION (provided by applicant): Mestastic colorectal cancer (CRC) is the third leading cause of cancer deaths among men and women in the US. Untreated metastic CRC only has a 8% 5 year survival, while treatment increases this survival rate to 30-35% (American Cancer Society Statistics 2004). However, only 20% of patients with CRC liver metastases are suitable for resection. This motivates the development of curative non-invasive treatment option. In this project, we will develop a high intensity focused ultrasound (HIFU) probe for treatment of malignancies in the upper abdomen organs. Though piezoelectric transducers have been traditionally used for therapeutic probes, this technology often suffers from difficulty in fabrication, reliability, and overheating. We propose using capacitive micromachined ultrasonic transducers (CMUTs) for HIFU. Not only are CMUTs easily fabricated using standard silicon processing techniques, which provide a cost-effective alternative, they also offer advantages like fabrication flexibility and direct integration with electronics. These advantages enable more flexible and reconfigurable therapeutic arrays for complex beamforming through layers of tissue. Furthermore, since CMUTs are not resonance structures, they have excellent bandwidth and efficiency. While imaging CMUTs have demonstrated excellent performance, a CMUT designed specifically for HIFU has not yet been designed. This project seeks to design and develop a prototype CMUT HIFU probe designed for MR-guided thermal therapy of liver and renal cancer. More specifically, we aim to: (1) Design and fabricate test CMUTs transducers specifically for HIFU; these test transducers will allow us to modify our designs and refine our finite element models to improve transducer performance and reliability. (2) Design, fabricate, and package an annular ring CMUT HIFU probe and electronics system for use in the MR scanner; the beam profile and reliability of this probe will be measured and refined as needed. (3) Fabricate a final CMUT probe packaged for use within a MR scanner. This probe will be integrated in the MR-guidance system and compared to conventional piezoelectric devices. Upon completion, the project will have developed a CMUT HIFU probe capable for MR-guided treatment of cancer that will be ready for in vivo testing. The success of this project will greatly increase the treatment options for the 80% of CRC and upper abdomenal cancer patients who are not suitable for resection, thereby reducing morbidity and mortality.