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Comparison of amplitude-decorrelation, speckle-variance and phase-variance OCT angiography methods for imaging the human retina and choroid.

ABSTRACT: We compared the performance of three OCT angiography (OCTA) methods: speckle variance, amplitude decorrelation and phase variance for imaging of the human retina and choroid. Two averaging methods, split spectrum and volume averaging, were compared to assess the quality of the OCTA vascular images. All data were acquired using a swept-source OCT system at 1040 nm central wavelength, operating at 100,000 A-scans/s. We performed a quantitative comparison using a contrast-to-noise (CNR) metric to assess the capability of the three methods to visualize the choriocapillaris layer. For evaluation of the static tissue noise suppression in OCTA images we proposed to calculate CNR between the photoreceptor/RPE complex and the choriocapillaris layer. Finally, we demonstrated that implementation of intensity-based OCT imaging and OCT angiography methods allows for visualization of retinal and choroidal vascular layers known from anatomic studies in retinal preparations. OCT projection imaging of data flattened to selected retinal layers was implemented to visualize retinal and choroidal vasculature. User guided vessel tracing was applied to segment the retinal vasculature. The results were visualized in a form of a skeletonized 3D model.

SUBMITTER: Gorczynska I

PROVIDER: S-EPMC4866465 | biostudies-other | 2016 Mar

REPOSITORIES: biostudies-other

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Project description:PurposeWe measured reproducibility of speckle-noise freed fluid and tissue compartmentalization of the choroid (choroidal angiography and tissue characterization).MethodsThis study included 26 eyes of 13 healthy females: 13 were used for repeated measurements and 13 were used for side comparison. A semiautomated algorithm removed speckle-noise with structure preservation.ResultsIntraclass correlation (ICC), with respect to reproducibility of the method, showed an ICC for choroidal fluid inner space analysis (FISA) of 95.15% (90.01-98.24). The ICC of tissue inner space analysis (TISA) was 99.75% (99.47-99.91). The total choroid ratio (TCR), calculated from volumes of tissue to vessels, showed an ICC of 88.84% (78.28-95.82). Comparison of eyes (left to right) showed a difference for FISA of 0.033 (95% confidence interval [CI] -0.0018-0.0680, P = 0.063), TISA -0.118 (CI -0.2373-0.0023, P = 0.055), and TCR -0.590 (CI -0.9047 to -0.2754, P = 0.004). The ICC for FISA and TISA showed a trend in the difference comparing left and right eyes; however, TCR showed a significant difference between the eyes in the measured area (P < 0.001). Mean overall FISA was 0.58 mm3 (range, 0.25-0.98 mm3, SD = 0.14). Mean TISA was 3.45 mm3 (range, 2.38-5.0 mm3, SD 0.072). Mean TCR was 6.13 (overall range, 3.93-10.2, SD = 1.34).ConclusionsDifferences in choroidal layers between subjects were found mainly due to alterations in choroidal tissue. Reproducibility of speckle-noise freed choroidal angiography appeared excellent.Translational relevanceSpeckle noise is a granular "noise" that appears in a wide range of medical imaging methods as ultrasonography, magnetic resonance, computer tomography, or optical coherence tomography (OCT). Findings from basic science about speckle noise were translated into a novel, medical image postprocessing application that can separate signal from speckle noise with structure preservation with high reproducibility and enhance medical imaging.

Project description:Purpose:To compare review strategies for optical coherence tomography angiography (OCT-A) for multiple disease features found in common diseases of the choroid and retina. Design:Prospective, observational study. Participants:Patients with macular disease undergoing routine spectral-domain optical coherence tomography (SDOCT). Methods:Eyes were imaged with the Avanti RTVue XR HD (Optovue, Fremont, CA), and the split-spectrum amplitude decorrelation angiography (SSADA) algorithm software was utilized for OCT-A performance. Scans were reviewed by 2 masked expert reviewers. A third masked reviewer was utilized in cases of reviewer disagreement. A single report using automated segmentation within the Avanti software to represent the superficial retina capillary plexus, deep retina capillary plexus, outer retina, and choroid capillary layer was generated. A continuous slab descent video export was also reviewed for each OCT-A scan. This video consisted of a continuous (e.g., line-by-line) review of the en face OCT- data. Each dataset was reviewed for the presence of three pathologic features: choroidal neovascularization, microaneurysms, and macular ischemia. Main Outcome Measures:Comparison of identification rates of retinal and choroidal microvascular abnormalities using different review strategies. Results:Four hundred twenty-one eyes were included in the study. Of those, 350 eyes had reports that were deemed sufficient quality for interpretation and analysis by both reviewers. Identification rates of choroidal neovascularization, microaneurysms, and macular ischemia on the report were 90.5%, 84.5%, and 95.4% respectively compared to the overall presence. Likewise, rates of identification in the continuous slab descent review video were 88.1%, 96.4%, and 95.4% for choroidal neovascularization, microaneurysms, and macular ischemia respectively compared to the overall presence. Cohen's kappa values ranged from 0.80 to 0.96, corresponding to very good agreement between the report and continuous slab descent review for each variable. Conclusions:Defining an optimal reporting strategy for OCT-A is important for diagnostic accuracy and optimizing workflow in retina clinics. In this study, OCT-A report using automated segmentation was comparable to continuous slab descent review for identifying microvascular abnormalities of the retina and choroid.

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Comparison of amplitude-decorrelation, speckle-variance and phase-variance OCT angiography methods for imaging the human retina and choroid.

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