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Normalized field autocorrelation function-based optical coherence tomography three-dimensional angiography.

ABSTRACT: Optical coherence tomography angiography (OCTA) has been widely used for en face visualization of the microvasculature, but is challenged for real three-dimensional (3-D) topologic imaging due to the "tail" artifacts that appear below large vessels. Further, OCTA is generally incapable of differentiating descending arterioles from ascending venules. We introduce a normalized field autocorrelation function-based OCTA (g1-OCTA), which minimizes the tail artifacts and is capable of distinguishing penetrating arterioles from venules in the 3-D image. g1 ( τ ) is calculated from repeated optical coherence tomography (OCT) acquisitions for each spatial location. The decay amplitude of g1 ( τ ) is retrieved to represent the dynamics for each voxel. To account for the small g1 ( τ ) decay in capillaries where red blood cells are flowing slowly and discontinuously, Intralipid is injected to enhance the OCT signal. We demonstrate that the proposed technique realizes 3-D OCTA with negligible tail projections and the penetrating arteries are readily identified. In addition, compared to regular OCTA, the proposed g1-OCTA largely increased the depth-of-field. This technique provides a more accurate rendering of the vascular 3-D anatomy and has the potential for more quantitative characterization of vascular networks.

SUBMITTER: Tang J

PROVIDER: S-EPMC6414735 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Normalized field autocorrelation function-based optical coherence tomography three-dimensional angiography.

Tang Jianbo J Erdener Sefik Evren SE Sunil Smrithi S Boas David A DA

Journal of biomedical optics 20190301 3

Optical coherence tomography angiography (OCTA) has been widely used for en face visualization of the microvasculature, but is challenged for real three-dimensional (3-D) topologic imaging due to the "tail" artifacts that appear below large vessels. Further, OCTA is generally incapable of differentiating descending arterioles from ascending venules. We introduce a normalized field autocorrelation function-based OCTA (g1-OCTA), which minimizes the tail artifacts and is capable of distinguishing p ...[more]

PMID: 30868803

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Project description:PurposeWe evaluated the repeatability of wide-field en face swept-source optical coherence tomography angiography (SS-OCTA) in healthy subjects.MethodsHealthy subjects underwent two imaging sessions, on average 8 days apart, with a 100 kHz SS-OCTA instrument. The imaging protocol included a central 3 × 3 and 12 × 12 mm scans of the four quadrants resulting in more than a 70° wide-field OCTA of the posterior pole. Quantitative analysis was performed using the inbuilt Macular Density Algorithm Version v0.6.1 and AngioTool software. Consistency for the foveal avascular zone (FAZ), vessel density, and perfusion density of the superficial and deep capillary plexus slabs and the wide-field OCTA superficial slab, and the number of artefacts on the wide-field images were assessed.ResultsA total of 21 healthy volunteers (seven men and 14 women; mean age 32 years; range, 18-61; standard deviation, 10.28 years) were included in this analysis. Internal consistency was highest for FAZ area with an intraclass correlation (ICC) = 0.998 (95% confidence interval [CI], 0.997-0.999), a FAZ perimeter with an ICC = 0.995 (95% CI, 0.990-0.997), a FAZ circularity with an ICC= 0.976 (95% CI, 0.956-0.987), followed by the vessel density of the inner ring in the superficial slab with an ICC = 0.834 (95% CI, 0.691-0.911), and a vessel density of the inner ring in the deep slab with an ICC = 0.523 (95% CI, 0.113-0.744).The reproducibility of the average vessels length of the wide-field OCTA cropped images was strong (ICC = 0.801; 95% CI, 0.624-0.895), followed by the reproducibility of total number of junctions (ICC = 0.795; 95% CI, 0.613-0.892) and the vessels percentage area (ICC = 0.662; 95% CI, 0.361-0.821).ConclusionsThe level of reproducibility for assessing the microvascular anatomy in wide-field OCTA is strong and can be used to quantify microvascular changes over time. Refinements in analysis strategies and a consensus of which parameters are most useful for quantitative assessment of wide-field OCTA images would be useful in the future.Translational relevanceThese findings bridge the gap between basic imaging research and clinical use for quantitative wide-field OCTA.

Project description:SignificanceLine-field confocal optical coherence tomography (LC-OCT) is a recently introduced high-resolution imaging modality based on a combination of low-coherence optical interferometry and reflectance confocal optical microscopy with line illumination and line detection. Capable of producing three-dimensional (3D) images of the skin with cellular resolution, in vivo, LC-OCT has been mainly applied in dermatology and dermo-cosmetology. The LC-OCT devices capable of acquiring 3D images reported so far are based on a Linnik interferometer using two identical microscope objectives. In this configuration, LC-OCT cannot be designed to be a very compact and light device, and the image acquisition speed is limited.AimThe objective of this work was to develop a more compact and lighter LC-OCT device that is capable of acquiring images faster without significant degradation of the resolution and with optimized detection sensitivity.ApproachWe developed an LC-OCT device based on a Mirau interferometer using a single objective. Dynamic adjustment of the camera frequency during the depth scan is implemented, using a faster camera and a more powerful light source. The reflectivity of the beam-splitter in the Mirau interferometer was optimized to maximize the detection sensitivity. A galvanometer scanner was incorporated into the device for scanning the illumination line laterally. A stack of adjacent B-scans, constituting a 3D image, can thus be acquired.ResultsThe device is able to acquire and display B-scans at 17 fps. 3D images with a quasi-isotropic resolution of ∼1.5 μm (1.3, 1.9, and 1.1 μm in the x , y, and z directions, respectively) over a field of 940 μm × 600 μm × 350 μm (x × y × z) can be obtained. 3D imaging of human skin at cellular resolution, in vivo, is reported.ConclusionsThe acquisition rate of the B-scans, at 17 fps, is unprecedented in LC-OCT. Compared with the conventional LC-OCT devices based on a Linnik interferometer, the reported Mirau-based LC-OCT device can acquire B-scans ∼2 times faster. With potential advantages in terms of compactness and weight, a Mirau-based device could easily be integrated into a smaller and lighter handheld probe for use by dermatologists in their daily medical practice.

Project description:ImportanceAlthough there is abundant evidence relating neuronal and vascular optical coherence tomography (OCT) and OCT angiography (OCTA) measures to retinal disease, data on the normative distribution of retinal features and their associations with visual function in a healthy, older, community-based population are sparse.ObjectivesTo characterize the normative OCT and OCTA measures in older adults and describe their associations with visual function.Design, setting, and participantsThis was a cross-sectional, observational study conducted from May 17, 2017, to May 31, 2019. The study included a community-based sample. Participants in the Atherosclerosis Risk in Communities study from Jackson, Mississippi (all self-reported Black participants), and Washington County, Maryland (all self-reported White participants), were recruited in the Eye Determinants of Cognition study (EyeDOC). Data analyses were conducted from June 14, 2020, to May 31, 2021.Main outcomes and measuresRetinal measurements, including retinal nerve fiber layer (RNFL) thickness, macular ganglion cell complex (GCC) thickness, macular vessel density (VD) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP), and foveal avascular zone (FAZ) area, were captured with spectral-domain OCT and OCTA. Visual function, including presenting distance vision, corrected distance vision, near visual acuity (VA), and contrast sensitivity (CS), was assessed.ResultsA total of 759 participants (mean [SD] age, 80 [4.2] years; 480 female participants [63%]; 352 Black participants [46%]) were included in the study. Mean (SD) GCC thickness (89.2 [9.3] μm vs 92.3 [8.5] μm) and mean (SD) FAZ (0.36 [0.16] mm2 vs 0.26 [0.12] mm2) differed between Jackson and Washington County participants, respectively. Mean (SD) RNFL thickness and mean (SD) VD in SCP and DCP were greater for participants 80 years or younger than for participants older than 80 years (RNFL: ≤80 years, 93.2 [10.5] μm; >80 years, 91.1 [11.6] μm; VD SCP, ≤80 years, 44.3% [3.5%]; >80 years, 43.5% [3.8%]; VD DCP, ≤80 years, 44.7% [4.9%]; >80 years, 43.7% [4.8%]). Linear regression showed each 10-μm increment in RNFL thickness and GCC thickness was positively associated with 0.016 higher logCS among all participants (RNFL: 95% CI, 0.005-0.027; P = .004; GCC: 95% CI, 0.003-0.029; P = .02), with stronger associations among Jackson participants. The associations of VA and structural measures were found only in Jackson participants, with coefficients per 10-μm increment of 0.012 logMAR VA (RNFL: 95% CI, 0.000-0.023; P = .049) and 0.020 logMAR VA (GCC: 95% CI, 0.004-0.034; P = .04).Conclusions and relevanceIn this cross-sectional study, better CS was associated with greater RNFL thickness and GCC thickness, but no visual measures were associated with angiographic features overall. These findings suggest that clinical application of normative references for OCT- and OCTA-based measures should consider demographic and community features.

Project description:BackgroundTo map and compare the three-dimensional choroidal vascularity index (3D-CVI) in eyes with unilateral central serous chorioretinopathy (CSC), fellow eyes and control eyes using ultra-widefield swept source optical coherence tomography (UWF SS-OCTA).MethodsIn this prospective observational study, the 3D-CVIs were measured in 9 subfields or 1 × 1 mm grids by the UWF SS-OCTA with a viewing angle of horizontal 24 × vertical 20 mm. The proportions of vortex vein anastomoses and their corresponding CVI in the central regions were compared among the CSC, fellow and control eyes. Correlations of CVI and vascular density of the large choroidal vessel layer/choriocapillaris layer/choroidal thickness (CT) were also assessed.ResultsThirty-two eyes in 32 patients with unilateral CSC and 32 normal eyes were included in the study. The mean CVI in the eyes with CSC was significantly greater than that in the fellow eyes of CSC and control eyes (41.99 ± 3.56% vs. 40.38 ± 3.855%, P = 0.003; 41.99 ± 3.56% vs. 38.93 ± 4.067%, P = 0.004, respectively). The CVIs in superotemporal, inferotemporal and inferonasal regions were significantly higher in CSC eyes than control eyes (P = 0.03, P = 0.02, P = 0.008). In CSC eyes, there was a linear positive correlation between 3D-CVI and vascular density of the large choroidal vessel layer and CT in all subfields. The proportion of vortex vein anastomoses in CSC was 25/32 (78.1%), and significantly higher in fellow and control eyes (P < 0.001). The average central CVI was significantly higher in CSC eyes with anastomoses than in CSC eyes without anastomoses (42.8 ± 5.1% vs. 38.4 ± 2.7%, P = 0.039). CVIs in superior, central, inferior, superonasal, nasal and inferonasal regions were significantly correlated with vortex vein anastomoses (P < 0.05), regardless of CSC, fellow or healthy eyes. In addition, whether there were vortex vein anastomoses, CVI in superotemporal region was significantly higher in eyes with CSC (P = 0.002) and fellow eyes (P = 0.014), compared to control eyes. No significant correlation was found between hypertension and CVIs in the three groups.ConclusionRemodeling of choroidal drainage routes by venous anastomosis between superior and inferior vortex veins may be common in CSC. The 3D-CVI could be a comprehensive parameter to evaluate the choroid vasculature and help understand the pathogenesis of pachychoroid spectrum disease.

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Normalized field autocorrelation function-based optical coherence tomography three-dimensional angiography.

Publications

Normalized field autocorrelation function-based optical coherence tomography three-dimensional angiography.

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