Repeatability of binarization thresholding methods for optical coherence tomography angiography image quantification.
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ABSTRACT:
SUBMITTER: Mehta N
PROVIDER: S-EPMC7505834 | biostudies-literature | 2020 Sep
REPOSITORIES: biostudies-literature
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Repeatability of binarization thresholding methods for optical coherence tomography angiography image quantification.
Mehta Nihaal N Braun Phillip X PX Gendelman Isaac I Alibhai A Yasin AY Arya Malvika M Duker Jay S JS Waheed Nadia K NK
Scientific reports 20200921 1
Binarization is a critical step in analysis of retinal optical coherence tomography angiography (OCTA) images, but the repeatability of metrics produced from various binarization methods has not been fully assessed. This study set out to examine the repeatability of OCTA quantification metrics produced using different binarization thresholding methods, all of which have been applied in previous studies, across multiple devices and plexuses. Successive 3 × 3 mm foveal OCTA images of 13 healthy ey ...[more]
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Project description:PurposeTo determine the impact of image binarization and the best thresholding method for conjunctival optical coherence tomography angiography (OCTA).MethodsVessel density (VD) of 14 OCTA conjunctival images (nine nasal and five temporal conjunctivas, and eight right and six left eyes) from normal subjects was analyzed. The binarization of gold-standard images, created by removing pixels that do not represent vessels on ImageJ software, was assessed by three masked graders to determine consistency of VD for images. Various thresholding methods on ImageJ, including manual, 1-, 2- and 3-step processes, were performed on unprocessed images for comparison. Interclass correlation coefficient (ICC) ≥0.750 were classified as good reliability and selected for calculation of the performance of the pixel location in the binarized images of each method.ResultsAnalysis of the gold-standard threshold method achieved an ICC of 0.816 with excellent agreement (R2 = 0.965, P < 0.001). From a total 28 different methods and variations performed, only nine methods performed with good reliability, including two 1-step thresholds, six 2-step thresholds, and one 3-step threshold method. Overall, 2-step threshold methods were more reliable than 3-step threshold methods. The 2-step method of Bandpass filter + Phansalkar local threshold (LT) showed the best performance with mean pixel accuracy of 86.9% ± 6.8%, area under the curve of 0.826, sensitivity of 79.0%, and specificity 86.1%.ConclusionsBandpass filter + Phansalkar LT was the best method for VD measurement in conjunctival OCTA. Most commonly reported threshold methods showed unsatisfactory agreement. There is a need in the OCTA field for a standardized method to allow comparison between different studies.Translational relevanceThe proposed threshold method using a widely accessible and commonly used software provides an accurate VD measurement for future OCTA studies.
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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.
| S-EPMC6502067 | biostudies-literature
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| S-EPMC6347178 | biostudies-literature
Project description:ImportanceImaging of the choriocapillaris in vivo is challenging with existing technology. Optical coherence tomography angiography (OCTA), if optimized, could make the imaging less challenging.ObjectiveTo investigate multiple en face image averaging on OCTA images of the choriocapillaris.Design, setting, and participantsObservational, cross-sectional case series at a referral institutional practice in Los Angeles, California. From the original cohort of 21 healthy individuals, 17 normal eyes of 17 participants were included in the study. The study dates were August to September 2016.ExposuresAll participants underwent OCTA imaging of the macula covering a 3 × 3-mm area using OCTA software (Cirrus 5000 with AngioPlex; Carl Zeiss Meditec). One eye per participant was repeatedly imaged to obtain 9 OCTA cube scan sets. Registration was first performed using superficial capillary plexus images, and this transformation was then applied to the choriocapillaris images. The 9 registered choriocapillaris images were then averaged. Quantitative parameters were measured on binarized OCTA images and compared with the unaveraged OCTA images.Main outcome and measureVessel caliber measurement.ResultsSeventeen eyes of 17 participants (mean [SD] age, 35.1 [6.0] years; 9 [53%] female; and 9 [53%] of white race/ethnicity) with sufficient image quality were included in this analysis. The single unaveraged images demonstrated a granular appearance, and the vascular pattern was difficult to discern. After averaging, en face choriocapillaris images showed a meshwork appearance. The mean (SD) diameter of the vessels was 22.8 (5.8) µm (range, 9.6-40.2 µm). Compared with the single unaveraged images, the averaged images showed more flow voids (1423 flow voids [95% CI, 967-1909] vs 1254 flow voids [95% CI, 825-1683], P < .001), smaller average size of the flow voids (911 [95% CI, 301-1521] µm2 vs 1364 [95% CI, 645-2083] µm2, P < .001), and greater vessel density (70.7% [95% CI, 61.9%-79.5%] vs 61.9% [95% CI, 56.0%-67.8%], P < .001). The distribution of the number vs sizes of the flow voids was skewed in both unaveraged and averaged images. A linear log-log plot of the distribution showed a more homogeneous distribution in the averaged images compared with the unaveraged images.Conclusions and relevanceMultiple en face averaging can improve visualization of the choriocapillaris on OCTA images, transforming the images from a granular appearance to a level where the intervascular spaces can be resolved in healthy volunteers.
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Project description:The aim of this study was to compare the repeatability of optical coherence tomography angiography (OCT-A) measurements of macular vessel density using four OCT-A systems, including Heidelberg Spectralis HRA, Optovue RTVue XR, Zeiss Cirrus HD-OCT 5000, and Topcon DRI OCT Triton. A cross-sectional design was used for this study. The vascular density and vascular length density of the superficial and deep retinal capillary plexuses were imaged with OCT-A using 3?mm and 6?mm scan patterns and were calculated using ImageJ. Comparisons of intraclass correlation coefficients (ICC) were conducted. We found that the OCT-A systems had various levels of repeatability. Zeiss had better repeatability for vessel density than the other systems (overall ICC?=?0.936). Optovue had better repeatability for vessel length density when the 6?mm scan pattern was used (ICC?=?0.680 and 0.700 for retinal superficial and deep capillary plexus, respectively). We concluded that repeatability varied when different scan patterns of various OCT-A systems were used for imaging the superficial retinal and deep capillary plexuses. Results should be seen as valid only for a given method. The repeatability of various OCT-A systems should be considered in clinical practice and in clinical trials that use OCT-A metrics as outcome measures.
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Project description:PurposeTo compare spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) for imaging retinal capillary hemangioblastomas (RCHs) in von Hippel-Lindau disease (VHLD).MethodsProspective single-center cross-sectional study. Tumor size (TS) of perfused RCHs was assessed clinically in relation to the optic disc size. For both technologies, SD-OCTA and SS-OCTA, corresponding images with a scan size of 3 × 3 mm2 and 6 × 6 mm2, respectively, were overlaid according to the set of marker positions to determine the TS.ResultsFrom 200 patients with VHLD, 48 patients showed 84 RCHs. SD-OCTA images of 39 RCHs (46.4%) and SS-OCTA images of 48 RCHs (57.2%) were suitable for analysis. The average in OCTA-measured TS of 1.60 ± 2.58 mm2 (range, 0.01-10.43) was congruent to the clinically assessed TS in 81.3% of cases (r = 0.86, P < 0.0001). TS measured in SD-OCTA compared to SS-OCTA showed similar values and a high correlation (all P < 0.0001). Nevertheless, despite the similarities, a slight trend in SS-OCTA was observed whereby with increasing TS, an elevated TS was detected compared to SD-OCTA (3 × 3-mm2 scans: mean difference of 0.03 ± 0.04 mm2, 6 × 6-mm2 scans: 0.08 ± 0.19 mm2). However, within the same imaging technology method, TS values almost did not differ (SD-OCTA: mean difference of 0.01 ± 0.02 mm2, SS-OCTA: 0.001 ± 0.01 mm2).ConclusionsOCTA may serve as an additional tool for diagnosis and monitoring of RCHs. Nevertheless, due to the differences between the technologies, the values cannot be used interchangeably.Translational relevanceSD-OCTA and SS-OCTA are suitable to detect and monitor RCHs and provide a more detailed assessment about the TS than this is clinically possible.
| S-EPMC7422766 | biostudies-literature
Project description:PurposeTo evaluate the mutual effect of widening the field of view and multiple en face image averaging on the quality of optical coherence tomography angiography (OCTA) images.MethodsThis prospective, observational, cross-sectional case series included 20 eyes of 20 healthy volunteers with no history of ocular or systemic disease. OCTA imaging of a 3 × 3-mm, 6 × 6-mm, and 12 × 12-mm area centered on the fovea was performed nine times using the PLEX Elite 9000. We acquired averaged OCTA images generated from nine en face OCTA images. The corresponding areas in the three scan sizes were evaluated for the original single-scanned OCTA images and averaged OCTA images both qualitatively and quantitatively. Quantitative measurements included vessel density (VD), vessel length density (VLD), fractal dimension (FD), and contrast-to-noise ratio (CNR).ResultsSignificant differences in VD, VLD, FD, and CNR (P < 0.001) were observed due to the mutual effect of averaging and differences in scan size. Both qualitative and quantitative evaluations indicated that the quality of 6 × 6-mm averaged images was equal to or better than that of 3 × 3-mm single-scanned images. However, the quality of 12 × 12-mm averaged images did not reach that of 3 × 3-mm single-scanned images.ConclusionsTo some extent, multiple en face OCTA image averaging can compensate for the deterioration in image quality caused by widening the field of view.Translational relevanceMultiple en face OCTA image averaging can be a technique for acquiring wider field OCTA images with good quality.
| S-EPMC8590158 | biostudies-literature
Project description:Macular ischemia is a key feature of diabetic retinopathy (DR). Quantification of macular ischemia has potential as a biomarker for DR.To assess the feasibility of automated quantification of capillary nonperfusion as a potential sign of macular ischemia using optical coherence tomography (OCT) angiography.An observational study conducted in a tertiary, subspecialty, academic practice evaluated macular nonperfusion with 6?×?6-mm OCT angiography obtained with commercially available 70-kHz OCT and fluorescein angiography (FA). The study was conducted from January 22 to September 18, 2014. Data analysis was performed from October 1, 2014, to April 7, 2015. Participants included 12 individuals with normal vision serving as controls and 12 patients with various levels of DR.Preplanned primary measures were parafoveal and perifoveal vessel density, total avascular area, and foveal avascular zone as detected with 6?×?6-mm OCT angiography and analyzed using an automated algorithm. Secondary measures included the agreement of the avascular area between the OCT angiogram and FA.Compared with the 12 healthy controls (11 women; mean [SD] age, 54.2 [14.2] years), the 12 participants with DR (4 women; mean [SD] age, 55.1 [12.1] years) had reduced parafoveal and perifoveal vessel density by 12.6% (95% CI, 7.7%-17.5%; P?<?.001) and 10.4% (95% CI, 6.8%-14.1%; P?<?.001), respectively. Total avascular area and foveal avascular zone area were greater in eyes with DR by 0.82 mm2 (95% CI, 0.65-0.99 mm2; P?=?.02) and 0.16 mm2 (95% CI, 0.05-0.28 mm2; P?<?.001). The agreement between the vascular areas in the OCT angiogram and FA had a ? value of 0.45 (95% CI, 0.21-0.70; P?<?.001). Total avascular area in the central 5.5-mm-diameter area distinguished eyes with DR from control eyes with 100% sensitivity and specificity.Avascular area analysis with an automated algorithm using OCT angiography, although not equivalent to FA, detected DR reliably in this small pilot study. Further study is necessary to determine the usefulness of the automated quantification in clinical practice.
| S-EPMC4978127 | biostudies-literature
Project description:PurposeTo compensate for reflectance variation when quantifying vessel density by optical coherence tomography angiography (OCTA).MethodsHealthy participants received 6×6-mm macular and 4.5×4.5-mm optic nerve head (ONH) angiography scans on a 70-kHz spectral-domain optical coherence tomography system. The split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to compute the OCTA signal. Mean reflectance projection and maximum decorrelation projection were used to create en face OCT and OCTA images. Background OCTA noise in static tissue was evaluated in the foveal avascular zone (FAZ). Vessel density was calculated from en face retinal OCTA that was binarized according to a decorrelation threshold.ResultsThe average retinal decorrelation noise in the FAZ was linearly related to the average logarithmic-scale OCT reflectance signal. Based on this relationship, a reflectance-adjusted decorrelation threshold equation was developed to filter out 97.5% of background OCTA noise. A fixed threshold was also used for comparison. The superficial vascular complex vessel density in the macula and ONH were significantly correlated with reflectance signal strength index (SSI) using the fixed threshold. This correlation was removed by using the reflectance-adjusted threshold. Reflectance compensation reduced population variation in 25 healthy eyes from 8.5% to 4.8% (coefficient of variation) in the macula and from 6.7% to 5.4% in the peripapillary region. Within-visit repeatability also improved from 4.4% to 1.8% in the macula and from 3% to 1.7% in the peripapillary region.ConclusionsCompensating for reflectance variation resulted in more reliable vessel density quantification in OCTA.
| S-EPMC5015963 | biostudies-literature