Non-invasive, high-resolution, 3D imaging and sensing through highly scattering materials

该项目探索和开发技术，以实现高保真成像和光聚焦内部和通过混浊介质，如生物组织。所研究的方法是非侵入性的，结合了光学和声学。最先进的高分辨率三维光学显微镜技术已经在生物和生物医学应用中产生了强大的影响。目前的商业模式包括成熟的技术，如共聚焦显微镜、双光子显微镜和光学相干断层扫描。不幸的是，一个共同的缺点是对生物组织的渗透有限，超过1毫米的一小部分，这是本提案的核心问题。组织中的高分辨率深度成像将使许多生物医学研究和诊断工具成为可能，例如血液氧合成像或改进光动力疗法。这项研究将为本科生和研究生创造机会，让他们参与与本提案相关的跨学科合作项目。该项目还将使生物医学光学成像方面的广泛教育活动成为可能。自适应波前整形的最新进展使得通过散射环境成像成为可能。通过对光波前进行预补偿，可以控制光在散射材料中的传播。然而，大多数现有技术都受限于它们需要从散射介质后面或内部产生反馈信号，并直接侵入，这在大多数生物医学成像场景中是不可能的。该项目强调解决深度、高分辨率成像和聚焦需求的基础发展，以解决新兴应用。光声效应，即声波响应于光场而产生，为波前优化提供了一种新的反馈机制，因为声波在组织中传播时几乎没有散射。因此，通过探测散射介质表面的声波，获得有效的无创反馈信号来指导波前补偿。此外，声换能器的空间非均匀灵敏度可用于将光引导到实质上小于声焦点区域的点。然而，由于血液流动和生理运动引起的斑点场变化速度很快，而且生物组织深处的斑点大小在一个波长量级，因此，通过真实生物材料和在真实生物材料内部进行光学聚焦和成像仍然是一个挑战。在本项目中，将探讨散射介质中聚焦的基础和实验限制，优化波前补偿算法以提高聚焦速度和通量，并研究以足以克服生物介质中散斑去相关的速度实现波前补偿的硬件开发。

This project explores and develops techniques to enable high-fidelity imaging and light focusing inside and through turbid media such as biological tissue. The methods investigated are non-invasive and combine optics and acoustics. State-of-the-art high-resolution three-dimensional optical microscopy techniques have already generated a strong impact in biological and biomedical applications. Current commercial modalities include mature technologies such as confocal microscopy, two-photon microscopy, and optical coherence tomography. Unfortunately, a common shortcoming is the limited penetration into biological tissue beyond a fraction of 1 mm, the problem at the core of this proposal. High-resolution deep imaging in tissue would enable numerous biomedical research and diagnosis tools such as imaging of blood oxygenation or improving photodynamic therapy. The research will create opportunities for undergraduate and graduate students to join in collaborative interdisciplinary projects associated with this proposal. The project will also enable broad educational activities in biomedical optical imaging.Recent advances in adaptive wavefront shaping have made imaging through scattering environments a possibility. By pre-compensating the optical wavefront, light propagation can be controlled through and beyond scattering materials. Most existing techniques, however, are limited by their need to generate a feedback signal from behind or inside the scattering media with direct invasive access, something not possible in the majority of biomedical imaging scenarios. This project emphasizes fundamental developments that address the need for deep, high-resolution imaging and focusing to tackle emerging applications. The photoacoustic effect, where acoustic waves are generated in response to an optical field, offers a new feedback mechanism for wavefront optimization because acoustic waves propagate in tissue with little scattering. Hence by detecting the acoustic waves at the surface of the scattering media, an effective and noninvasive feedback signal is obtained to guide wavefront compensation. Furthermore, the spatially nonuniform sensitivity of the acoustic transducer can be used to guide the light to a point that is substantially smaller than the acoustic focal region. Nevertheless, optical focusing and imaging through and within real biological materials remains a challenge due to the fast rate of change of the speckle field from blood flow and physiological motion and the fact that the speckle size deep in biological tissue is on the order of a wavelength. In this project, fundamental and experimental limitations on focusing in scattering media will be explored, algorithms for wavefront compensation will be optimized for focusing speed and fluence enhancement, and hardware developments for implementing wavefront compensation at speeds sufficient to overcome speckle decorrelation in biological media will be investigated.