Department of Structural Biology, Stanford University School of Medicine, Stanford, California, 94305, USA.
Biophysics Program at Stanford, Stanford, California, 94305, USA.
Sci Rep. 2020 Feb 5;10(1):1893. doi: 10.1038/s41598-020-58454-0.
Optical coherence tomography (OCT) suffers from speckle noise due to the high spatial coherence of the utilized light source, leading to significant reductions in image quality and diagnostic capabilities. In the past, angular compounding techniques have been applied to suppress speckle noise. However, existing image registration methods usually guarantee pure angular compounding only within a relatively small field of view in the focal region, but produce spatial averaging in the other regions, resulting in resolution loss and image blur. This work develops an image registration model to correctly localize the real-space location of every pixel in an OCT image, for all depths. The registered images captured at different angles are fused into a speckle-reduced composite image. Digital focusing, based on the convolution of the complex OCT images and the conjugate of the point spread function (PSF), is studied to further enhance lateral resolution and contrast. As demonstrated by experiments, angular compounding with our improved image registration techniques and digital focusing, can effectively suppress speckle noise, enhance resolution and contrast, and reveal fine structures in ex-vivo imaged tissue.
光学相干断层扫描（OCT）由于所用光源的空间相干性高而存在散斑噪声，导致图像质量和诊断能力显著降低。过去，已经应用了角度复合同化技术来抑制散斑噪声。然而，现有的图像配准方法通常仅在焦区的相对较小视场范围内保证纯角度复合同化，而在其他区域产生空间平均化，导致分辨率损失和图像模糊。这项工作开发了一种图像配准模型，以正确定位 OCT 图像中每个像素的真实空间位置，适用于所有深度。从不同角度捕获的配准图像被融合成一幅散斑减少的复合图像。基于复 OCT 图像与点扩散函数（PSF）的共轭卷积的数字聚焦被研究用于进一步提高横向分辨率和对比度。实验表明，采用我们改进的图像配准技术和数字聚焦的角度复合同化可以有效地抑制散斑噪声，提高分辨率和对比度，并揭示离体成像组织中的精细结构。
