Optical sensors for ultrasound detection in photoacoustic imaging

光声（PA）是生物医学成像的一种形式，结合了超声和光学成像的优点。将高强度激光脉冲递送到生物组织中允许在组织内有效地产生超声，使得可以以传统光学装置无法达到的方式对其成像。 然而，目前在激光源和超声检测方面的技术限制限制了PA在实验室环境之外的使用。 该项目的目标包括（1）制造超灵敏的大带宽超声/PA传感器并将其纳入多传感器阵列，（2）创建可用于临床环境的紧凑PA光源，以及（3）使用这些阵列研究生物系统中的新现象。 Aim 1本身就是一项重大的技术进步。更低的可检测压力和更高的动态范围将使我们能够从生物组织内部更深处重建图像，更高的带宽将提高图像的分辨率。 与此同时，我们还将致力于这些微型超声波传感器的阵列，从而在硅光子铸造厂（如AIM（美国制造业协会）集成光子计划）的帮助下实现低成本的多元件阵列。 目标2将克服传统光声源的笨重和限制性特性，传统光声源是一种体积庞大的激光器，只能以低于100 Hz的重复率传递脉冲。 我们将开发具有紧凑型高功率激光二极管的便携式光声成像系统，利用正在进行的努力来增加用于无人驾驶汽车中的激光雷达系统的脉冲激光二极管的功率。提高传感器灵敏度将进一步使得能够使用更低成本、更低功率并且因此更安全的激光器来感应PA信号。 总之，我们的传感器开发和系统优化将减少PA成像的尺寸和成本，并将提供一种有用且足够便宜的工具，用于大规模药理学研究和全球许多实验室的临床前研究。 目标3将开发多模式深部组织PA成像的新技术，这将导致非侵入性床边成像方法。 该方法将同时提供真实的组织中代谢和血流变化的图。此外，多模态PA成像性能可以极大地受益于基于快速激光二极管的敏捷光源，正如我们在之前的全光学显微镜大脑研究中所示。 加拿大是开发先进医学成像技术的领导者，在多伦多设有中心，如Techna研究所，负责开发和利用成像技术改善健康。 超声和光声成像方面的知识用户，如FUJIFILM VisualSonics Inc.可以将我们的发现转化为全球药物开发和医学成像的新机会。

Photoacoustics (PA) is a form of biomedical imaging that combines the benefits of both ultrasound and optical imaging. The delivery of high intensity laser pulses into biological tissue allows for the efficient generation of ultrasound in-tissue so that it can be imaged in a way that would otherwise be inaccessible with conventional optical means. However, current technological restrictions, in both the laser source and ultrasound detection, limit the use of PA beyond the lab setting. The aims of this project include (1) the fabrication of an ultrasensitive large-bandwidth ultrasound/PA sensor and incorporating it into a multi-sensor array, (2) creating a compact PA optical source that can be used in the clinical setting, and (3) using these arrays to investigate new phenomena in biological systems. Aim 1 is a major technological advance in itself. The lower detectable pressures and improved dynamic range will allow us to reconstruct images from deeper inside biological tissue, and the higher bandwidth will improve the resolution of the images. In parallel, we will also be working on an array of these miniature ultrasound sensors, leading to a low-cost multi-element array with the help of a silicon photonics foundry such as the AIM (American Institute of Manufacturing) Integrated Photonics Initiative. Aim 2 will overcome the cumbersome and limiting properties of the conventional photoacoustic source a bulky laser that can only deliver pulses at repetition rates of less than 100 Hz. We will develop portable photo-acoustic imaging systems with compact high power laser diodes, leveraging ongoing efforts to increase power in pulsed laser diodes for LIDAR systems in driver-less cars. Improving sensor sensitivity will further enable the use of lower cost, lower power and, consequently, safer lasers for inducing the PA signal. Together, our sensor development and system optimization will reduce the size and cost of PA imaging and will provide a tool that is useful and inexpensive enough for use in large-scale pharmacological studies, and in many labs worldwide in preclinical studies. Aim 3 will develop new techniques in multi-modal deep tissue PA imaging that will lead to a non-invasive bedside imaging method. The method will provide simultaneously maps of metabolic and blood flow changes in the tissue in real time. Further, multi-modal PA imaging performance can greatly benefit from a fast laser diode-based agile light source as we showed in our previous all-optical microscopy studies of the brain. Canada is a leader in developing advanced medical imaging technologies, with centers in Toronto such as the Techna Institute responsible for the development and exploitation of imaging technology for improved health. Knowledge users in ultrasound and photoacoustic imaging such as FUJIFILM VisualSonics Inc. can translate our discoveries to new opportunities in drug development and medical imaging worldwide.