CAREER: Conformable Piezoelectrics for Soft Tissue Imaging

医学超声具有许多特性，使其适合作为成像工具和作为无处不在的生物传感技术广泛使用。然而，目前，用于疾病检测和监测的医学超声的广泛部署受到刚性传感器几何形状的限制。一方面，刚性传感器几何形状通常被认为是期望的，因为已知的几何形状有助于相干波束形成和图像重建。然而，另一方面，刚性传感器不适应身体表面曲率，需要在成像期间由熟练的操作者施加传感器压力。这种基于压缩的图像采集过程称为“超声检查”，需要相当高的技能，这反过来又增加了操作者的可变性。此外，需要操作者施加压力与可穿戴技术不兼容，极大地限制了医疗超声技术的范围和实用性。这项拟议研究的目的是解决上述核心未满足的需求，这是一种新型的顺应性超声系统的发展，这将使目前由于缺乏合适的仪器而无法洞察软组织生物学。该系统有可能通过提供组织表征数据来补充乳腺X线摄影成像，从而促进稀缺的乳腺癌护理资源的最佳利用。这项工作对发展中国家尤其重要，因为发展中国家缺乏合格的超声操作员和相关基础设施，极大地限制了获得医疗服务的机会。拟议的跨学科项目将与教育和推广活动相结合，包括开发新课程，旨在传播传统物理和材料科学社区之外的新微制造技术，以增加对STEAM领域的兴趣和参与，并在K-12，本科和研究生教育水平上推广压电系统的研究。在大面积的软表面上获得足够的接触（即，肩，胸）或小关节（即，指关节、腕关节）是不能实现的，这是由于超声换能器的刚性平面设计与身体部分的典型曲线形状的对比。人类乳房提出了特别的挑战，因为其几何形状和变形性不仅在受试者之间而且在给定受试者内的不同时间和年龄都是高度可变的。同时，乳腺癌是最常见的癌症，并且此类癌症通常位于超声检查的预期穿透深度内。因此，有机会开发用于乳腺病变纵向成像的技术，用于癌症诊断和早期检测目的，并且还用作乳腺肿瘤生物学行为的新的非侵入性窗口。拟议的研究的主要目标是通过引入一种新的系统设计和微制造策略，沿着一个框架和先进的算法来重建时空精确的图像，可以应用于任何人体部位，开发适合的相控阵超声贴片的软组织成像在大面积，曲线区域。在项目实施过程中将应对的挑战包括：1）开发大面积、适形的相控阵列换能器设计，2）从高度曲线的身体部位进行时空精确的3-D图像重建，3）在体外对模拟组织体模进行体内实时致动和感测，以及在有限的人体试验中进行体内实时致动和感测，和乳房病变的表征。拟议的工作将建立在PI的跨学科的专业知识和经验，压电，微加工生物医学设备和适应系统。拟议的系统将提供接口，实现下一代可穿戴技术的功能，例如对任何软组织进行准确、实时和自主的3D成像监测，以及机器学习策略，以客观的方式检测疾病进展。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Medical ultrasound has many properties that make it suitable for widespread use both as an imaging tool and as a ubiquitous biosensing technology. At present, however, wide deployment of medical ultrasound for disease detection and monitoring has been limited by rigid sensor geometries. On one hand, rigid sensor geometries are generally considered desirable, as known geometries facilitate coherent beamformation and image reconstruction. On the other hand, however, rigid sensors do not accommodate body surface curvature, necessitating the application of sensor pressure by a skilled operator during imaging. This compression-based process of image acquisition, termed “sonography,” requires considerable skill, in turn increasing interoperator variability. Moreover, the need to have an operator apply pressure is incompatible with wearable technology, greatly limiting the scope and utility of medical ultrasound technology. The aim of this proposed research is to address the core unmet need described above, which is the development of a novel class of conformable ultrasound systems that would enable insights into soft tissue biology presently not possible owing to a lack of suitable instrumentation. The system has the potential to complement mammographic imaging by providing tissue characterization data that would facilitate optimal use of scarce breast cancer care resources. This work will be particularly relevant to developing nations, where a shortage of qualified ultrasound operators and related infrastructure greatly limits access to care. The proposed interdisciplinary project will be integrated with educational and outreach activities, including development of new courses geared towards disseminating new microfabrication techniques outside of the traditional physics and material science communities to increase interest and engagement in STEAM fields and to proliferate the study of piezoelectric systems at the K-12, undergraduate, and graduate education levels. Obtaining sufficient contact over soft surfaces of large areas (i.e., shoulder, breast) or small joints (i.e., finger joints, wrist joints) is not achievable, due to the rigid planar design of the ultrasound transducer versus the typical curvilinear shape of body parts. The human breast presents a particular challenge, as its geometry and deformability are highly variable not only between subjects but also at different times and ages within a given subject. At the same time, breast cancer is the most common cancer and such cancers are typically located within the expected penetration depth of sonography. As a result, there is an opportunity to develop technology for longitudinal imaging of breast lesions both for cancer diagnostic and early detection purposes and also serve as a new non-invasive window into the biological behavior of breast tumors. The primary goal of the proposed research is to develop conformable phased array ultrasound patches for soft tissue imaging over large-area, curvilinear regions by introducing a novel system design and microfabrication strategy, along with a framework and advanced algorithms to reconstruct spatiotemporally-accurate images that could be applied to any human body parts. The challenges that will be addressed during the course of the project include: 1) Development of large-area, conformable phased array transducer design, 2) Spatiotemporally-accurate 3-D image reconstruction from highly curvilinear body parts, 3) In vivo, real-time actuation and sensing on both in vitro on mock tissue phantoms and in vivo in a limited human trial focused on the detection, localization, and characterization of breast lesions. The proposed work will build upon the PI's interdisciplinary expertise and experience in piezoelectric, microfabricated biomedical devices and conformable systems. The proposed system will provide interfaces that enable next-generation features of wearable technologies, such as accurate, real-time and autonomous monitoring of any soft tissue for 3-D imaging, and machine learning strategies to detect disease progression in an objective manner.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.