Abstract
A method allows the extraction of the recovery factor that maximizes the image contrast of OCT (optical coherence tomography) and/or OCTA (OCT angiography) of a living subject is proposed in this study. Due to the finite depth of focus in imaging optics, the volume OCT imaging suffers from blurriness in the lateral resolution. By utilizing the digital hologram method or angular spectrum method, the blurred image can be refocused. However, for in vivo OCT imaging, evaluation of the image focus is not easy, owing to the cloudy structure of the brain. In the proposed method, the blood flow signals were used as a guiding star to find the recovery factor. The propagation distance to a focal plane was automatically determined by evaluating the contrast of a cross-sectional OCTA image. The performance was examined though in vivo mouse brain OCT/OCTA imaging. The image singularity of the blood flow in OCTA was very effective at evaluating the contrast of the image.
Highlights
Optical coherence tomography (OCT) can provide a three-dimensional (3D) structural image of a biological sample [1]
OCT has axial and lateral resolutions of several tens of microns that are independently determined by different factors
We propose and present a specific method that can be applied for automatic digital refocusing of in vivo brain OCT images
Summary
Optical coherence tomography (OCT) can provide a three-dimensional (3D) structural image of a biological sample [1]. The in vivo, noninvasive, high-resolution image capability of OCT can be useful for early diagnosis or observing the progress of various diseases. OCT has axial and lateral resolutions of several tens of microns that are independently determined by different factors. The axial resolution is proportional to the spectral bandwidth of the light source and the characteristics of the detector. The lateral resolution is determined mainly by the beam diameter and the focal length of the focusing lens, as in light microscopy. OCT has a trade-off relationship between the transverse resolution and the depth of field (DOF), which might hinder acquisition of high-resolution 3D data for a thick sample. The transverse resolution of OCT images obtained outside the DOF decreases
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