Development of beam-offset optical coherence tomography

项目摘要 对于深层组织的细胞成像，自适应光学OCT(AO-OCT)已经由以下方面得到了大力发展 对照明光束的波前进行整形以将光束聚焦到衍射限制的点扩散 目标区域中的功能(PSF)。由于其复杂性、成本和尺寸，基于波前传感器的AO-OCT 将其转化为诊所是一项挑战。不太复杂的无传感器AO-OCT(SAO-OCT)优化了 PSF使用图像度量，但不能确保全局最优，并且容易受到运动伪影的影响 因为在优化迭代过程中，图像度量必须是强大和稳定的。训练有素的人工神经元 网络(ANN)可以立即优化波前，比传统的波前优化效率高得多 通过多次迭代进行优化。然而，使用图像度量训练ANN会限制 神经网络的概括性。我们认为，SAO-OCT的最佳衡量标准应该是PSF或其 频域等效调制传递函数(MTF)，因为它们是优化的目标 并且与成像对象和系统光学无关。然而，接入技术 在含有OCT的散射介质中的PSF/MTF还没有被提出。OCT图像来源于 由于组织中的折射率变化而产生的反向散射光子。新对比度，与组织属性相关 光衰减系数(OAC)，已被广泛研究，以提高诊断 OCT的能力然而，OAC的推导主要是基于单次散射模型，忽略了这一点 与传统的OCT一样，MSP不能区分LSP和MSP。此外，单次散射模型 依赖于至少三个相互依赖的参数。需要先验知识来确保派生OAC 成功，但在临床环境中获得它是不现实的。这些限制已经禁止了OAC 测量从被转换到诊所。在这里，我们提出了重建背向散射光子 波束偏移OCT(BO-OCT)散射介质中的分布(BPD)解决上述问题 挑战。在传统的OCT中，照明光束和检测光束共享相同的光路。在……里面 BO-OCT，检测光束在距照明光束的偏移位置处获取图像。BPD可以 然后用偏移图像进行重建。我们的理论预测和初步数据表明， LSP的分布相当于深度分辨的MTF，表明SAO-OCT是可以实现的 使用MTF作为衡量标准。使用BPD，我们还展示了分离LSP和MSP是可行的，允许 为了通过仅使用LSP来拟合单次散射模型来准确地反演OAC。实时访问 通过BPD的焦深和瑞利范围允许将这些参数的变化合并到 建模，提出了一种不受运动伪影影响的新方法。

Project Summary For cellular imaging in deep tissue, adaptive optics OCT (AO-OCT) has been intensively developed by reshaping the wavefront of the illumination beam to focus the beam to diffraction-limited point spread function (PSF) in a targeted region. Due to its complexity, cost, and size, wavefront sensor-based AO-OCT is challenging to be translated into clinics. Less complicated sensorless AO-OCT(SAO-OCT) optimizes the PSF using image metrics, but cannot ensure global optimization and is susceptible to motion artifacts because image metrics must be strong and steady during the optimizing iteration. A trained Artificial neuron network (ANNs) can optimize the wavefront immediately, much more efficiently than the conventional optimization through multiple iterations. However, training ANNs with the image metric limits the generality of the ANN. We believe that the best metric for SAO-OCT should be either the PSF or its frequency domain equivalent, modulated transfer function (MTF), as they are the goals for optimization and are independent of the imaged subjects and system optics. However, the technology of accessing PSF/MTF in a scattering medium with OCT has not been proposed.OCT images originate from backscattered photons due to refractive index variation in tissue. New contrast, tissue property-related optical attenuation coefficient (OAC), has been extensively investigated to improve the diagnostic capability of OCT. However, deriving OAC is mainly based on the single-scattering model, which ignores MSPs, as conventional OCT cannot distinguish LSPs and MSPs. In addition, the single-scattering model relies on at least three interdependent parameters. Prior knowledge is needed to ensure deriving OAC successfully, but obtaining it in a clinical setting is not practical. These limitations have prohibited OAC measuring from being translated into clinics. Here, we propose reconstructing backscattered photon distribution(BPD) in a scattering medium with beam-offset OCT (BO-OCT) to resolve the above challenges. In conventional OCT, the illumination and detection beams share the same optical paths. In BO-OCT, the detection beam acquires images at offset positions from the illumination beam. The BPD can then be reconstructed with the offset images. Our theoretical prediction and preliminary data show that the distribution of LSPs is equivalent to the depth-resolved MTF, suggesting SAO-OCT can be implemented using the MTF as the metric. With the BPD, we also show it is feasible to separate LSPs and MSPs, allowing for accurately retrieving OAC by using just the LSPs to fit the single-scattering model. Real-time accessing focal depth and Rayleigh range through the BPD allow incorporating the variation of these parameters into modeling, suggesting a new method immune from motion artifacts.