Multi-Frequency Synthesis and Orientation Control in SFDI

描述(申请人提供)：空间频域成像(SFDI)是一种基于模型的、广域、非接触的方法，用于测量生物组织的吸收、散射和荧光特性。通过测量以不同空间频率和相位投射到样品上的正弦模式的光的衰减(或荧光)，同时确定每个像素的光学属性。通过处理样品的3个相移视图来解调图像。在给定波长下的平均询问深度由投影的空间频率控制，并且路径长度的频率依赖差被用来使用计算模型来计算组织光学特性。因为每个投影频率需要3个特定的相位，所以必须注意对所有投影和相机触发器进行完美的排序。虽然这些过程中的每一个都相当快，但它们加在一起可以将采集速度减慢到相机帧速率的一小部分。为了克服这一限制，促进实时SFDI，我们将开发使用“频率合成”的新方法-将多个频率合成到定制的投影图案中。这些图案将针对速度和频率相关的信息内容进行优化，以促进快速准确的光学特性测量、探测埋藏物体和执行层析成像。如果选择得当，频率合成投影可能会将最小采集时间降低到相机的帧速率，从而实现实时SFDI和SFD断层成像。投影自定义图案的能力不仅允许我们生成多频率分量，还增加了更改其方向的能力。这允许我们探索一种新的对比度模式，该模式基于探测与投影图案的方向对齐的组织结构。这是因为许多组织类型，包括大脑中的骨、肌肉、皮肤和白质，都对内部结构进行了定位，使得光学散射的程度取决于光的传播方向。这些定向组织的散射方向由其微观结构决定，并服从扩散方程。我们将在空间频率域中得到各向异性扩散方程的精确解。在有序介质中，正弦模式的衰减取决于空间频率模式和散射体方向的相对方向。因此，通过在不同方向上投射多个空间频率并测量衰减，我们将能够在大范围内成像空间变化的散射方向 视野。我们期望空间频率合成和定向控制的结合将导致在厚组织中进行定量、实时成像和层析成像的新方法，以及基于光学扩散张量的令人兴奋的新的对比机制的表征。 与公共健康相关：这些研究将使我们能够获得足够的数据，以开发和验证一种新的光学技术，用于基于相对简单、成本效益高的成像相机和图案化光投影技术对组织进行实时、定量成像和深度切片。这项技术有可能取代传统的基于相机的成像方法，因为它允许定量查看表面下的功能组织属性，疾病通常是在表面下开始的。我们的方法有望带来新的床边医学成像方法，用于检测疾病、监测治疗反应和指导外科手术。

DESCRIPTION (provided by applicant): Spatial Frequency Domain Imaging (SFDI) is a model-based, wide-field, non-contact method for measuring the absorption, scattering, and fluorescence properties of biological tissue. Optical properties are determined in each pixel simultaneously, by measuring the attenuation (or fluorescence) of sinusoidal patterns of light projected onto the sample at varying spatial frequencies and phases. Images are demodulated by processing 3 phase-shifted views of the sample. The mean interrogation depth at a given wavelength is controlled by the spatial frequency of projection, and frequency-dependent differences in path length are used to calculate tissue optical properties using computational models. Because 3 specific phases are required for each projected frequency, care must be taken to perfectly sequence all projections and camera triggers. While each of these processes is fairly rapid, together they can slow the acquisition to a fraction of the camera frame rate. In order to overcome this limitation and facilitate real-time SFDI, we will develop new methods using "frequency synthesis" - multiple frequencies synthesized into customized projection patterns. These patterns will be optimized for speed and frequency-dependent information content in order to facilitate rapid and accurate optical property measurements, probe buried objects, and perform tomography. When properly selected, frequency synthesized projections can potentially decrease the minimum acquisition time to the frame rate of the camera, allowing real-time SFDI and SFD tomography. The ability to project custom patterns not only allows us to generate multi-frequency components, it also adds the ability to change their orientation. This allows us to explore a new mode of contrast based on probing tissue structures that are aligned with the direction of the projected pattern. This is due to the fact that many tissue types, including bone, muscle, skin, and white matter in the brain, have orientated internal structures such that the degree of optical scattering depends on the direction of light propagation. The scattering direction of these oriented tissues is determined by their microscopic structure and obeys a diffusion equation. We will derive accurate solutions to the anisotropic diffusion equation in the spatial frequency domain. In an ordered medium, the attenuation of sinusoidal patterns depends on the relative orientation of the spatial frequency pattern and scatterer direction. Thus, by projecting multiple spatial frequencies in different directions and measuring the attenuation, we will be able to image the spatially varying scattering orientation over a large field of view. We expect that the combination of spatial frequency synthesis and orientation control will lead to new methods for quantitative, real-time imaging and tomography in thick tissues, as well as the characterization of exciting new contrast mechanisms based on an optical diffusion tensor. PUBLIC HEALTH RELEVANCE: These studies will allow us to acquire sufficient data to develop and validate a new optical technology for real-time, quantitative imaging and depth sectioning of tissues based on relatively simple, cost-effective imaging cameras and patterned light projection techniques. The technology has potential to replace conventional camera-based imaging methods by allowing quantitative viewing of functional tissue attributes beneath the surface, where disease typically begins. Our approach is expected to lead to new, bedside medical imaging methods for detecting disease, monitoring therapy response, and guiding surgical procedures.