Frontiers of Photoacoustic Imaging

我们提出的研究的长期目标是开发光声成像技术，推动生物医学成像的新前沿。光声成像是一种新兴的生物医学成像方式，它使用脉冲激光激发组织。当光被吸收时，声波被创建并用于形成体内光学特性的图像。我们已经取得了相当大的进展，但是，我们认为PA成像需要进一步发展的一些领域：（1）除了血液和黑色素色素，直到最近很少有人探索体内其他自然发生的对比机制。我们提出了一些技术来成像到组织中，以获得有关特定化学键的信息，而不需要造影剂。所提出的方法还将提供关于化学物质在被激光脉冲询问后处于激发态的时间的信息。(2)光声成像中的定量一直是个难题。理想情况下，我们希望创建光学吸收，散射系数（重要的是，因为细胞核通常在癌症和癌前病变中扩大，影响散射）和发色团浓度的定量图像。已经提出了大量的方法来算法解决这个非平凡的反问题，但是，每个都有自己的一组问题。需要做更多的工作来开发一种有用的和鲁棒的方法来改进定量，我们提出了关键的算法和方法来做到这一点。(3)需要改进的超声换能器技术。光声信号可能很弱，灵敏度和频率响应应该最大化。超宽带和超灵敏换能器被提出来改善光声成像的质量、分辨率和穿透深度。我们提出的研究旨在解决目前的局限性，使PA成像到新的前沿。

The long-term objective of our proposed research is to develop photoacoustic imaging technologies that push new frontiers of biomedical imaging. Photoacoustic imaging is an emerging biomedical imaging modality that uses pulsed lasers to excite tissues. When light is absorbed, sound waves are created and used to form images of the optical properties inside the body. We have made considerable progress photoacoustic imaging, however, we perceive some areas where PA imaging needs further development: (1) Aside from blood & melanin-based pigment, until recently little has been done to explore other naturally-occuring contrast mechanisms in the body. We propose a number of techniques to image into tissues to attain information about specific chemical bonds without the need for contrast agents. The proposed methods will also provide information about the time chemical species are in an excited state after being interrogated by a laser pulse. (2) Quantitation has been difficult in photoacoustic imaging. Ideally we would like to create quantitative images of optical absorption, scattering coefficients (important because cell nuclei are often enlarged in cancers and pre-cancers, affecting scattering), and concentrations of chromophores. A large number of methods have been proposed to algorithmically solve this non-trivial inverse problem, however, each has its own set of problems. More work is needed to develop a useful & robust method for improved quantitation and we propose key algorithms and methods to do this. (3) Improved ultrasound transducer technology is needed. Photoacoustic signals can be weak & sensitivity and frequency response should be maximized. Ultrabroadband & ultrasensitive transducers are proposed to improve the quality, resolution, and penetration depth of photoacoustic imaging. Our proposed research aims to address present limitations to bring PA imaging to new frontiers.