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领域。光声成像是一种新兴的生物医学成像方式，它使用脉冲激光来激发组织。当光被吸收时，就会产生声波，用来在体内形成光学特性的图像。我们已经在光声成像方面取得了相当大的进展，然而，我们认为PA成像还需要进一步发展的一些领域：(1)除了血液和基于黑色素的色素外，直到最近还很少探索身体中其他自然发生的对比机制。我们提出了一些技术成像到组织，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有关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)光声成像的定量一直是难点。理想情况下，我们希望创建光学吸收、散射系数（很重要，因为在癌症和癌症前期，细胞核通常会扩大，影响散射）和发色团浓度的定量图像。人们已经提出了大量的算法来求解这一非平凡逆问题，然而，每种方法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稳健的方法来改进定量，我们提出了关键的算法和方法来做到这一点。(3)超声换能器技术有待改进。光声信号可能很弱，灵敏度和频率响应应最大化。为了提高光声成像的质量、分辨率和穿透深度，提出了超宽带和超灵敏换能器。我们提出的研究旨在解决目前的限制，将PA成像带到新的领域。

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.