Abstract
Optical coherence tomography (OCT)-based optical microangiography (OMAG) is a high-resolution, noninvasive imaging technique capable of providing three-dimensional in vivo blood flow visualization within microcirculatory tissue beds in the eye. Although the technique has demonstrated early clinical utility by imaging diseased eyes, its limited field of view (FOV) and the sensitivity to eye motion remain the two biggest challenges for the widespread clinical use of the technology. Here, we report the results of retinal OMAG imaging obtained from a Zeiss Cirrus 5000 spectral domain OCT system with motion tracking capability achieved by a line scan ophthalmoscope (LSO). The tracking LSO is able to guide the OCT scanning, which minimizes the effect of eye motion in the final results. We show that the tracking can effectively correct the motion artifacts and remove the discontinuities and distortions of vascular appearance due to microsaccade, leading to almost motion-free OMAG angiograms with good repeatability and reliability. Due to the robustness of the tracking LSO, we also show the montage scan protocol to provide unprecedented wide field retinal OMAG angiograms. We experimentally demonstrate a 12 x 16 mm² retinal OMAG angiogram acquired from a volunteer, which is the widest FOV retinal vasculature imaging up to now in the community.
Highlights
Ophthalmic imaging has emerged as one of the most successful applications for optical coherence tomography (OCT) since its invention in the early 1990s.1 The capability of OCT to provide noninvasive, noncontact, high-resolution, high-sensitive, and depth-resolved imaging of microstructures in the retina and eye has been a key factor for its success.[2]
This illustrated the distortions and artifacts caused by microsaccades and drift, and their effective corrections by motion tracking in final retinal optical microangiography (OMAG) angiograms
We showed that the tracking feature in the OCT system enabled the ultrawide view imaging of retinal vasculature, ∼67 degrees of view, which is the widest field of view (FOV) functional imaging capability demonstrated in the OCT community
Summary
Ophthalmic imaging has emerged as one of the most successful applications for optical coherence tomography (OCT) since its invention in the early 1990s.1 The capability of OCT to provide noninvasive, noncontact, high-resolution, high-sensitive, and depth-resolved imaging of microstructures in the retina and eye has been a key factor for its success.[2]. The human eye is in constant motion that is caused by involuntary fixational eye movements, e.g., microsaccades and drift.[13] This eye motion currently remains a major challenge for OMAG to provide the images of functional retinal microvasculature with high fidelity, because the motion would inevitably result in motion artifacts in the final results To mitigate this eye motion problem, one obvious approach is to increase the imaging speed of the OCT systems. B-scans were repeated four times in the current study for extracting the flow signal because this number has been tested to provide a reasonable imaging performance for OMAG in terms of acceptable imaging time and image quality.[10,34] The time difference between two successive B-scans was ∼4.5 ms, roughly corresponding to a frame rate of 224 fps Based on this scan protocol and system speed, the total time for a single volume acquisition was about 3.6 s, not including the adjustment time before the data collection.
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