Abstract
The field of view of optical coherence tomography angiography (OCTA) images of the retina can be increased by montaging consecutive scans acquired at different retinal regions. Given the dramatic variation in aberrations throughout the entire posterior pole region, it is challenging to achieve seamless merging with apparent capillary continuity across the boundaries between adjacent angiograms. For this purpose, we propose herein a method that performs automated registration of contiguous OCTA images based on invariant features and uses a novel montage algorithm. The invariant features were used to register the overlapping areas between adjacently located scans by estimating the affine transformation matrix needed to accurately stitch them. Then, the flow signal was compensated to homogenize the angiograms with different brightness and the joints were blended to generate a seamless, montaged wide-field angiogram. We evaluated the algorithm on normal and diabetic retinopathy eyes. The proposed method could montage the angiograms seamlessly and provided a wide-field of view of retinal vasculature.
Highlights
Since the first time-domain optical coherence tomography (OCT) [1] article was published in 1991, OCT technology has developed rapidly
We developed an algorithm to montage separate Optical coherence tomography angiography (OCTA) images in order to achieve a wide field of view
In this study, we developed an invariant features-based automated registration and montage algorithm for wide-field OCT angiography, composed of four main steps: (1) detect the invariant features including points of interest and their feature descriptors using the Speed-Up Robust-Features (SURF) algorithm; (2) match the detected points of interest of the target image with the moving image using their feature descriptors; (3) filter the inaccurate matches and apply the Random Sampling Consensus (RANSAC) algorithm; (4) estimate the affine matrix to stitch the moving image on the target image
Summary
Since the first time-domain optical coherence tomography (OCT) [1] article was published in 1991, OCT technology has developed rapidly. With faster scanning using Fourier-domain modalities, current OCT devices allow acquisition of three-dimensional data representing the retinal layered structure rapidly. Optical coherence tomography angiography (OCTA) detects the variation of OCT signal reflectance over scans repeated at the same location in order to evaluate the microcirculation flow in vivo; allowing sensitive, fast (< 3 seconds), and high resolution volumetric imaging of the retinal flow [2]. This technique has demonstrated utility in key ophthalmic diseases such as diabetic retinopathy, age-related macular degeneration, and glaucoma, allowing visualization of vascular details. Previous studies have shown that wide-field OCTA can reveal more clinically useful information [4,5]
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