Abstract
Current optical coherence tomography (OCT) based micro-angiography is prone to a projection (or tailing) effect due to the high scattering property of blood within overlying patent vessels, creating artifacts that interfere with the interpretation of retinal angiographic results. In this work, the projection effect in OCT micro-angiography is examined and its causality is explained by strong light scattering and photon propagation within blood. A simple practical approach is then introduced to minimize these artifacts presented in the outer retinal avascular space, especially useful for examining clinical cases with choroidal neovascularization (CNV). Demonstrated through in-vivo human posterior eye imaging of healthy and CNV subjects, the proposed method is shown effective to eliminate the projection artifacts in outer retinal space of OCT micro-angiography, resulting in better visualization of the pathological neovascularization when compared with the current common approaches. In addition, it is also shown that the proposed method is applicable to minimize the projection artifacts appearing in deep retinal layers.
Highlights
Choroidal neovascularization (CNV) involves the growth of abnormal new blood vessels that originate from choroid, breaking through Bruch’s membrane (BM) and extending into the retinal pigment epithelium (RPE) and outer retinal space
In the current normal practice to get away from this artifact, it is to parallel-shift the segmentation line of RPE up to above the IS/OS line (as shown in Fig. 4(a)), and produce the projection results from outer plexiform layer (OPL) to this shifted line to exclude the projection artifacts appeared in the IS/OS and RPE layers
Projection artifacts are obvious in optical coherence tomography (OCT) based angiography, which can interfere with the clinical interpretation of the final angiographic results
Summary
Choroidal neovascularization (CNV) involves the growth of abnormal new blood vessels that originate from choroid, breaking through Bruch’s membrane (BM) and extending into the retinal pigment epithelium (RPE) and outer retinal space. Fluorescein angiography (FA) and indocyanine green angiography (ICGA) have been de facto the golden standard for detecting neovascularization within retina and choroid in ophthalmic clinic. Both FA and ICGA have proven their clinical usefulness for patients with CNV [3]. None of these methods is depth resolved; they have to rely on clinician’s judgement to differentiate the neovascularization characterized by CNV. Both FA and ICGA require intravenous dye injection, which might result in nausea and other side effects [4, 5], and more importantly cannot be used repeatedly on patients over time
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