Toward Quantitative Optical Coherence Tomography Angiography

Ploner, Stefan B.; Moult, Eric M.; Choi, WooJhon; Waheed, Nadia K.; Lee, ByungKun; Novais, Eduardo Amorim; Cole, Emily; Potsaid, Benjamin; Husvogt, Lennart; Schottenhamml, Julia; Maier, Andreas; Rosenfeld, Philip J.; Duker, Jay S.; Hornegger, Joachim; Fujimoto, James G.

doi:10.1097/iae.0000000000001328

Cited by 117 publications

(59 citation statements)

References 41 publications

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“…Also, shorter wavelengths are more prone to scattering and attenuation; thus, they penetrate into tissue less than the longer wavelengths used in the SS-OCT devices. SS-OCT devices typically use wavelengths above 1000-nm and operate at speeds equal to or greater than 100-kHz (Drexler and Fujimoto 2008, Ploner, Moult et al 2016). …”

Section: Principles Of Optical Coherence Tomography Angiographymentioning

confidence: 99%

“…A variable interscan time analysis (VISTA) method was proposed to investigate the effect of different interscan times on vascular changes in the choriocapillaris of patients with nonexudative AMD and geographic atrophy. The VISTA method calculated the flow signals between sequential OCT B-scans (1 and 2, 2 and 3, 3 and 4, and 4 and 5, where interscan time was approximately 1.5-ms) and between every two B-scans (1 and 3, 2 and 4, and 3 and 5, where interscan time was approximately 3-ms) respectively (Ploner, Moult et al 2016). Their results demonstrated that VISTA was able to shift the range of the detectable flow speeds.…”

Section: Principles Of Optical Coherence Tomography Angiographymentioning

confidence: 99%

“…OCTA may allow us to revisit the relevance of microaneurysms in diabetic macular edema with additional studies, but it is likely that additional improvements on OCTA hardware and software will be necessary for this. For example, using variable interscan intervals (VISTA) during the acquisition for OCTA images allows measurement of a relative blood flow in DR (Ploner, Moult et al 2016) and AMD (Choi, Moult et al 2015). At this time, VISTA is only possible with the very high scan speeds (400-KHz) of a prototype SS-OCT instrument using a vertical cavity surface emitting laser (VCSEL).…”

Section: Octa Fluorescein Angiography (Fa) and Indocyanine Green mentioning

confidence: 99%

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Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

Kashani

Chen

Gahm

et al. 2017

Progress in Retinal and Eye Research

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561

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OCT has revolutionized the practice of ophthalmology over the past 10 to 20 years. Advances in OCT technology have allowed for the creation of novel OCT-based methods. OCT-Angiography (OCTA) is one such method that has rapidly gained clinical acceptance since it was approved by the FDA in late 2016. OCTA images are based on the variable backscattering of light from the vascular and neurosensory tissue in the retina. Since the intensity and phase of backscattered light from retinal tissue varies based on the intrinsic movement of the tissue (e.g. red blood cells are moving, but neurosensory tissue is static), OCTA images are essentially motion-contrast images. This motion-contrast imaging provides reliable, high resolution, and non-invasive images of the retinal vasculature in an efficient manner. In many cases, these images are approaching histology level resolution. This unprecedented resolution coupled with the simple, fast and non-invasive imaging platform have allowed a host of basic and clinical research applications. OCTA has been shown to demonstrate many important clinical findings including areas of macular telangiectasia, impaired perfusion, microaneurysms, capillary remodeling, some types of intraretinal fluid, and neovascularization among many others. More importantly, OCTA provides depth-resolved information that has never before been available. Correspondingly, OCTA has been used to evaluate a spectrum of retinal vascular diseases including diabetic retinopathy (DR), retinal venous occlusion (RVO), uveitis, retinal arterial occlusion, and age-related macular degeneration among others. In this review, we will discuss the methods used to create OCTA images, the practical applications of OCTA in light of invasive dye-imaging studies (e.g. fluorescein angiography) and review clinical studies demonstrating the utility of OCTA for research and clinical practice.

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Section: Principles Of Optical Coherence Tomography Angiographymentioning

confidence: 99%

Section: Principles Of Optical Coherence Tomography Angiographymentioning

confidence: 99%

Section: Octa Fluorescein Angiography (Fa) and Indocyanine Green mentioning

confidence: 99%

See 1 more Smart Citation

Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

Kashani

Chen

Gahm

et al. 2017

Progress in Retinal and Eye Research

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750

561

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“…Nevertheless, to describe the functional state of the microcirculation, it would be essential to determine the blood flow velocity in OCTA images of the sublingual microcirculation (as a measure of convective flow) 26 , which was not possible with the device used. However, recent experimental and clinical studies describe an automatic measurement of blood flow velocity in OCTA images of the retina [42][43][44] . Third, in OCTA images of the retina and choroid, single layers are automatically identified and flow density for the respective layer calculated.…”

mentioning

confidence: 99%

Optical coherence tomography angiography as a novel approach to contactless evaluation of sublingual microcirculation: A proof of principle study

Heßler

Nelis

Ertmer

et al. 2020

Sci Rep

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Microcirculatory disorders are crucial in pathophysiology of organ dysfunction in critical illness. Evaluation of sublingual microcirculation is not routinely conducted in daily practice due to timeconsuming analysis and susceptibility to artifacts. We investigated the suitability of optical coherence tomography angiography (octA) for contactless evaluation of sublingual microcirculation. Sublingual microcirculation was imaged in 10 healthy volunteers, using an OCTA device and an incident dark field (IDF) illumination microscopy (current gold standard). OCTA images were analyzed with regard to flow density and perfused vessel density (PVD byoctA). IDF videos were analyzed following current recommendations. Flow density was automatically extracted from OCTA images (whole en face 48.9% [43.2; 54.5]; central ring 52.6% [43.6; 60.6]). PVD byoctA did not differ from the PVD calculated from IDF videos (PVD byoctA 18.6 mm/mm² [18.0; 21.7]) vs. PVD byIDF 21.0 mm/mm² [17.5; 22.9]; p = 0.430). Analysis according to Bland-Altman revealed a mean bias of 0.95 mm/mm² (95% Confidence interval −1.34 to 3.25) between PVD byoctA and PVD byIDF with limits of agreement of −5.34 to 7.24 mm/mm². This study is the first to demonstrate the suitability of OCTA for evaluating sublingual microcirculation. comparison of the perfused vessel density between methods showed a plausible level of agreement. In recent years, research has highlighted the importance of the microcirculation (vessels smaller than 100 μm) in the pathophysiology of diseases and organ dysfunction in critical illness. It is known that blood flow in the microcirculation is often impaired in critically ill patients and altered blood flow in the microcirculation is associated with outcome 1-6. A decoupling of macro-and microcirculation ("loss of hemodynamic coherence"), as can occur, for example, in advanced stages of septic shock is of particular interest here 7. In such conditions, macrohemodynamic parameters such as cardiac output and perfusion pressure are no longer indicative of perfusion in the microcirculation. The aim of hemodynamic therapy should therefore be restoration not only of the macrocirculation but also the microcirculation 7. Hence the demand for bedside methods to monitor the microcirculation. Bedside analysis of the microcirculation became possible with the introduction of modern handheld video microscopes using sidestream dark field (SDF) imaging or incident dark field (IDF) illumination technology 8-10. Unfortunately, the analysis of the microcirculation has not yet become established in routine clinical practice, as video microscopy of capillary blood flow has so far been limited by artifacts (e.g.

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“…To obtain flow signal, OCTA algorithms [1,3,[18][19][20] rely on mathematical operations that quantify variations in the amplitude and/or the phase of optical coherence tomography (OCT) signal between at least two consecutive B-scans acquired at the same raster position. However, since the interscan time cannot be extremely small without affecting sensitivity to slow-speed blood flow [21,22], OCTA of the retina is sensitive to involuntary eye motion between B-scans.…”

Section: Introductionmentioning

confidence: 99%

Regression-based algorithm for bulk motion subtraction in optical coherence tomography angiography

Camino¹,

Jia²,

Liu³

et al. 2017

Biomed. Opt. Express

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Abstract:We developed an algorithm to remove decorrelation noise due to bulk motion in optical coherence tomography angiography (OCTA) of the posterior eye. In this algorithm, OCTA B-frames were divided into segments within which the bulk motion velocity could be assumed to be constant. This velocity was recovered using linear regression of decorrelation versus the logarithm of reflectance in axial lines (A-lines) identified as bulk tissue by percentile analysis. The fitting parameters were used to calculate a reflectance-adjusted upper bound threshold for bulk motion decorrelation. Below this threshold, voxels are identified as non-flow tissue, their flow values are set to zeros. Above this threshold, the voxels are identified as flow voxels and bulk motion velocity is subtracted from each using a nonlinear decorrelation-velocity relationship previously established in laboratory flow phantoms. Compared to the simpler median-subtraction method, the regression-based bulk motion subtraction improved angiogram signal-to-noise ratio, contrast, vessel density repeatability, and bulk motion noise cleanup in the foveal avascular zone, while preserving the connectivity of the vascular networks in the angiogram.

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Toward Quantitative Optical Coherence Tomography Angiography

Cited by 117 publications

References 41 publications

Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

Optical coherence tomography angiography as a novel approach to contactless evaluation of sublingual microcirculation: A proof of principle study

Regression-based algorithm for bulk motion subtraction in optical coherence tomography angiography

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