Optical sensors for ultrasound detection in photoacoustic imaging

点击翻译按钮获取中文摘要

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.