Abstract
We propose an innovative registration method to correct motion artifacts for wide-field optical coherence tomography angiography (OCTA) acquired by ultrahigh-speed swept-source OCT (>200 kHz A-scan rate). Considering that the number of A-scans along the fast axis is much higher than the number of positions along slow axis in the wide-field OCTA scan, a non-orthogonal scheme is introduced. Two en face angiograms in the vertical priority (2 y-fast) are divided into microsaccade-free parallel strips. A gross registration based on large vessels and a fine registration based on small vessels are sequentially applied to register parallel strips into a composite image. This technique is extended to automatically montage individual registered, motion-free angiograms into an ultrawide-field view.
Highlights
Optical coherence tomography angiography (OCTA) uses blood flow induced signal variation as an intrinsic contrast mechanism to differentiate vasculature from static tissues [1,2,3,4,5,6,7,8,9,10,11]
OCTA images can be presented en face to replicate the view of traditional dye-based angiography [12,13]
On Fig. 9(A) and 9(B), it can be observed that the flow signal at the lower and upper left corners of en face image is poor, resulting in the capillaries having low contrast
Summary
Optical coherence tomography angiography (OCTA) uses blood flow induced signal variation as an intrinsic contrast mechanism to differentiate vasculature from static tissues [1,2,3,4,5,6,7,8,9,10,11]. Small motions such as eye drift, tremor, or mechanical instabilities of the OCT apparatus can shift the intensity distribution within MB-scans at each position This type of motion results in increased decorrelation signal in static tissue. Large and rapid motions of the eye such as microsaccades introduce motion artifacts that are clearly visible on en face OCTA projections as horizontal or vertical white lines These large motions artifacts saturates the decorrelation scale and overwhelm flow signal and cannot be corrected by subtraction or registration – these B-frames must be removed. This introduces loss of lines in the en face OCTA images that disrupt the continuity of vascular networks. These lines must be replaced with rescanning or by combining redundant data from multiple scans
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