Large-Scale Optical Ultrasound Transducer Arrays for High-Speed and High-Resolution 3D Acoustic Tomography

超声成像在临床上对许多疾病的早期发现、诊断和预后是必不可少的。它提供实时成像速度，没有有害的电离辐射，而且成本低。然而，目前的超声成像系统主要产生可能不准确和/或难以解释的二维平面图像。因此，三维(3D)成像能力对于可视化、导航和研究自然是3D的患者解剖和病理是必不可少的。为了及时生成3D图像，超声成像系统必须能够捕获成像目标(如肿瘤)发出的整个声波波场。这需要大量的超声波传感器或换能器，大量的电缆，以及复杂而昂贵的数据采集电子设备。遗憾的是，由于系统的复杂性和成本，三维超声成像在性能和可用性方面仍然非常有限。在这个项目中，将开发一种新的光学技术来探测不可见的声波波场，并将其转换为可见的光学光场，从而很容易被相机记录下来。这种“看得见声音”的方法有望解决性能和成本问题，并为3D超声成像的许多应用打开大门。该项目还将为学生和公众提供独特的多学科学习和培训机会，涉及微系统、光学、声学和医学成像。该项目旨在实现大规模光学超声换能器(OUT)阵列，以实现高速和高分辨率的3D声学层析成像。与电信号不同的是，OUT通过光机械调制将超声波转换为光信号。这使得即使在小元件尺寸的情况下也可以保持高灵敏度。更重要的是，超声信号可以在没有物理互连的情况下，通过光学手段以无线方式读出。然而，现有OUT的一个根本挑战是其光学均匀性较差。从多个单元读出超声信号需要连续的光学调谐，这是一个繁琐的过程，严重限制了数据采集的速度。该项目旨在通过探索新的光学探测器的设计、制造和读出方法来解决当前OUT中的根本瓶颈问题。特别是，新的机械/光学联合设计和建模将与精密微加工和调谐工艺相结合，以实现具有可控和均匀光学和声学特性的大规模阵列。此外，还将开发一种新的基于脉冲照明和摄像机捕获的并行方法来实现超声数据的快速采集。凭借无线光学读数和对电磁干扰的自然免疫力，Out阵列可以实现以前无法实现的新的声成像功能，从无绳系留、可穿戴或远程成像到与其他主流成像模式的无缝融合。此外，Out阵列的高光学透明度可以极大地促进混合光学和声学成像的集成。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Ultrasound imaging is essential in the clinic for early detection, diagnosis, and prognosis of many diseases. It provides real-time imaging speed, has no harmful ionizing radiation, and is low cost. However, current ultrasound imaging systems mainly produce two-dimensional planar images that may be inaccurate and/or difficult to interpret. Therefore, a three-dimensional (3D) imaging capability is essential for visualizing, navigating, and investigating patient anatomy and pathologies that are naturally 3D. To produce 3D images in a timely manner, an ultrasound imaging system must be able to capture the whole acoustic wave field emitted by the imaging target, such as a tumor. This requires a large array of ultrasound sensors or transducers, massive electrical cables, and sophisticated and expensive data acquisition electronics. Unfortunately, because of high system complexity and cost, 3D ultrasound imaging is still very limited in terms of performance and availability. In this project, a new optical technology will be developed to detect and convert the invisible acoustic wave field into a visible optical light field, which can be readily recorded by a camera. This “seeing the sound” approach is expected to address the performance and cost issues and open the door for many applications of 3D ultrasound imaging. This project will also provide unique multidisciplinary learning and training opportunities in microsystems, optics, acoustics and medical imaging for students and the general public. This project aims to achieve large-scale optical ultrasound transducer (OUT) arrays for enabling high-speed and high-resolution 3D acoustic tomography. Different from their electrical counterparts, OUTs convert ultrasound waves into optical signals through optomechanical modulation. This makes it possible to maintain high sensitivity even with a small element size. What’s more, ultrasound signals can be read out “wirelessly” via optical means without physical interconnects. However, one of the fundamental challenges in existing OUTs are their poor optical uniformity. Reading out ultrasound signals from multiple elements requires continual optical tuning, which is a tedious process and seriously limits the data acquisition speed. This project aims to address the fundamental bottleneck issues in current OUTs by exploring novel optical detector design, fabrication, and readout methods. Particularly, new mechanical/optical co-design and modeling will be combined with precision micromachining and tuning processes for achieving large-scale OUT arrays with controllable and uniform optical and acoustic properties. In addition, a new parallel approach based on pulsed illumination and camera capturing will be developed for fast ultrasound data acquisition. With wireless optical readout and natural immunity to electromagnetic interference, the OUT array could enable new acoustic imaging capabilities not possible before from tetherless, wearable, or remote imaging to seamless fusion with other mainstream imaging modalities. In addition, the high optical transparency of the OUT array can greatly facilitate the integration of hybrid optical and acoustic imaging.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.