Compensation for Reflectance Variation in Vessel Density Quantification by Optical Coherence Tomography Angiography.
Ontology highlight
ABSTRACT: Purpose
To compensate for reflectance variation when quantifying vessel density by optical coherence tomography angiography (OCTA).Methods
Healthy 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.Results
The 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.Conclusions
Compensating for reflectance variation resulted in more reliable vessel density quantification in OCTA.
SUBMITTER: Gao SS
PROVIDER: S-EPMC5015963 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:PurposeTo assess the optical coherence tomography angiography (OCTA) retinal vessel density and foveal avascular zone (FAZ) in children with type 1 diabetes (T1D) and compare potential pathologic early changes in this population to healthy age-matched controls.MethodsThis study included 130 pubescent children: 94 with T1D (188 eyes) and 36 of their age-matched control group (60 eyes). OCTA was performed using AngioVue (Avanti, Optivue). FAZ area (mm2) in superficial plexus, whole superficial capillary vessel density (wsVD), fovea superficial vessel density (fsVD), parafovea superficial vessel density (psVD), whole deep vessel density (wdVD), fovea deep vessel density (fdVD), parafovea deep vessel density (pdVD), foveal thickness (FT) (?m) and parafoveal thickness (PFT) (?m) were taken into analysis. Among the studied patients with T1D there were assessed codependences regarding the investigated foveal and parafoveal parameters and selected potential predictors, i.e. patient's age (years), diabetes duration time (years), age of onset of the disease (years), mean level of glycated hemoglobin (HbA1C) (%), and concentration of serum creatinine (mg/dL).ResultsNone of the abovementioned OCT and OCTA parameters was statistically significantly different between the groups. The patient's age statistically significantly did not influent any of the OCT and OCTA parameters. Yet an elevated level of HbA1C tended to reduce the parafovea superficial vessel density (p = 0.039), and parafoveal thickness (p = 0.003) and an increased serum creatinine level correlated with the decreased whole deep vessel density (p < 0.001). The parafovea deep vessel density in the diabetic patients decreased when the serum creatinine level (p = 0.008), age of onset of the disease (p = 0.028), and diabetes duration time (p = 0.014) rose.ConclusionsVessel density, both in superficial and deep plexuses, and FAZ area are normal in pubescent children with T1D comparing to healthy subjects. An elevated level of HbA1C correlated with reduced psVD and PFT. Longitudinal observation of these young patients is needed to determine if any of these OCTA measurements are predictive of future DR severity.
| S-EPMC5650189 | biostudies-literature
Project description:BackgroundMany studies suggest the existence of an alteration of the retinal hemoperfusion in primary open-angle glaucoma. The OCT-A is a novel technique that allows to provide information on retinal microcirculation in a non-invasive way, thus it represents a possible imaging target for the early diagnosis and follow-up of glaucoma. The aim of our work is to evaluate the contribution of vascular parameters provided by OCT-A and their diagnostic abilities in the different stages of primary open-angle glaucoma.MethodThis is a prospective cross-sectional study involving 200 eyes of control subjects and 250 eyes of glaucomatous subjects divided into early glaucoma, moderate glaucoma and advanced glaucoma subgroups. They were assessed for MD, LV by visual field, RNFL and GCC thickness by SS-OCT papillary and macular vascular densities by SS-OCT A.ResultsOCT-A vessel densities determined in the optic nerve head, in the peripapillary and in the macular regions were significantly lower in glaucomatous eyes. Among the vascular parameters studied the whole image vascular density showed the best diagnostic ability in the discrimination between glaucomatous eyes and healthy eyes with an AUC of 0.949. Nevertheless, the diagnostic ability of vascular parameters remains lower than of the structural parameters RNFL (AUC: 0.981). A significant correlation was found between structural, functional and vascular parameters with r < 0.05. The quadratic non-linear model defines better the relationship between structural, vascular and functional damage in glaucoma.ConclusionThe OCT-A plays an important role in the early diagnosis and follow-up of PAOG. It also contributes to the understanding of some aspects of the vascular role in glaucoma.
| S-EPMC8361292 | biostudies-literature
Project description:PurposeTo compare the retinal vessel density and glaucomatous parameters in primary angle closure glaucoma (PACG), to evaluate the diagnostic and monitoring abilities of the peripapillary and macular vessel density in the progression of glaucoma.MethodsThis was a observational, prospective and cross-sectional study. According to Glaucoma Staging System, 218 eyes (116 participants) were divided into 5 groups: no glaucoma, early glaucoma, moderate glaucoma, advance glaucoma, severe glaucoma. All participants underwent a comprehensive ocular examination, which included corrected distance visual acuity measurement, slit-lamp biomicroscopy, intra ocular pressure (IOP), gonioscopy, fundus examination, stereoscopic optic disc photography, Humphrey visual field test(VF), peripapillary and macular optical coherence tomography angiography(OCTA) scan. SPSS software was used to calculate and compare retinal vessel density (peripapillary vessel density, PVD and macular vessel density, MVD) and glaucomatous parameters (mean deviation (MD),pattern standard deviation(PSD), retinal nerve fiber layer (RNFL), ganglion cell-inner plexiform layer(GCIPL),rim area, average cup/disc(C/D) ratio).ResultsThe GCIPL thickness, RNFL thickness, PVD and MVD are significantly reduced in PACG. There were significant differences in all measurements among the groups (P<0.01).Reduced peripapillary and macular vessel density in glaucoma were detected and a statistically significant correlation with glaucoma stages (P<0.01). In addition, the results of retinal vessel density, reduced RNFL thickness and GCIPL thickness were also statistically related to the stage of glaucoma. As expected, the rim area was significantly smaller with higher C/D area ratios in glaucomatous eyes corresponding to the severity of disease.ConclusionsThe changes of PVD and MVD had strongly positive correlation with GCIPL thickness and RNFL thickness, had negative correlation with the severity of glaucoma, which meant the more severe the glaucoma was, the lower PVD and MVD were. Compared to traditional glaucoma staging system judged by VF, the changes of PVD and MVD obtained by OCTA might be a new method to grade the stage of glaucoma. These findings theorize that the changes of PVD and MVD may be better facilitated for the observation and monitoring of glaucoma progression.
| S-EPMC7316331 | biostudies-literature
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.
| S-EPMC9315074 | biostudies-literature
Project description:Purpose:To compare papillary and macular vessel density (VD), as measured by optical coherence tomography angiography (OCTA), in eyes with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG) and exfoliation glaucoma (XFG). Methods:The papillary and macular VD of 40 eyes with POAG, 19 with NTG and 21 with XFG were examined using OCTA (AngioVue™). The VD was measured at two different layers of segmentation (optic nerve head: radial peripapillary capillary [RPC] and nerve head [NH]; macula: superficial [SL] and deep [DL] retinal vascular plexus) with a 4.5×4.5mm papillary and 6×6-mm macular scan. VD was calculated by an automated density measuring tool in the AngioVue™ software. Results:There were no significant differences in the total value of the papillary, peripapillary and macular VD. A significantly higher VD could be measured for NTG compared to POAG, as well as for XFG in the inferior nasal peripapillary sector at RPC-segmentation and at the NH-level between NDG and XFG. Conclusion:OCTA can detect a difference in VD in the nasal inferior peripapillary sector in NTG compared with POAG and XFG. These findings may help to improve the understanding of further pathophysiological mechanisms.
| S-EPMC6925548 | biostudies-literature
Project description:PURPOSE:To provide values of retinal vessel density (VD) in the three retinal capillary plexuses, foveal avascular zone (FAZ) area, and retinal layer thickness in a cohort of healthy subjects. METHODS:The optical coherence tomography angiography maps of 148 eyes of 84 healthy subjects, aged 22 to 76 years, were analyzed for measuring VD of the retinal capillary plexuses, using the Optovue device comprising a projection artifact removal algorithm. Foveal avascular zone metrics were measured, and the relationship between optical coherence tomography angiography findings and age, sex, and image quality was studied. RESULTS:The deep capillary plexus showed the lowest VD (31.6% ± 4.4%) in all macular areas and age groups compared with the superficial vascular plexus (47.8% ± 2.8%) and intermediate capillary plexus (45.4% ± 4.2%). The mean VD decreased by 0.06%, 0.06%, and 0.08% per year, respectively, in the superficial vascular plexus, intermediate capillary plexus, and deep capillary plexus. Mean FAZ area, FAZ acircularity index, and capillary density in a 300-µm area around the FAZ were 0.25 ± 0.1 mm, 1.1 ± 0.05, and 50.8 ± 3.4%, respectively. The yearly increase in FAZ area was 0.003 mm (P < 0.001). CONCLUSION:The deep capillary plexus, a single monoplanar capillary plexus located in the outer plexiform layer, has the lowest VD, a significant finding that might be used to evaluate retinal vascular diseases. Vascular density decreased with age in the three capillary plexuses.
| S-EPMC6358199 | biostudies-literature
Project description:PurposeTo investigate whether vessel density assessed by optical coherence tomography angiography (OCT-A) is reduced in glaucomatous eyes with focal lamina cribrosa (LC) defects.DesignCross-sectional, case-control study.ParticipantsA total of 82 patients with primary open-angle glaucoma (POAG) from the Diagnostic Innovations in Glaucoma Study (DIGS) with and without focal LC defects (41 eyes of 41 patients in each group) matched by severity of visual field (VF) damage.MethodsOptical coherence tomography (OCT) angiography-derived circumpapillary vessel density (cpVD) was calculated as the percentage area occupied by vessels in the measured region extracted from the retinal nerve fiber layer (RNFL) in a 750-μm-wide elliptical annulus around the disc. Focal LC defects were detected using swept-source OCT images.Main outcome measuresComparison of global and sectoral (eight 45-degree sectors) cpVDs and circumpapillary RNFL (cpRNFL) thicknesses in eyes with and without LC defects.ResultsAge, global, and sectoral cpRNFL thicknesses, VF mean deviation (MD) and pattern standard deviation, presence of optic disc hemorrhage, and mean ocular perfusion pressure did not differ between patients with and without LC defects (P > 0.05 for all comparisons). Mean cpVDs of eyes with LC defects were significantly lower than in eyes without a defect globally (52.9%±5.6% vs. 56.8%±7.7%; P = 0.013) and in the inferotemporal (IT) (49.5%±10.3% vs. 56.8%±12.2%; P = 0.004), superotemporal (ST) (54.3%±8.8% vs. 58.8%±9.6%; P = 0.030), and inferonasal (IN) (52.4%±9.0% vs. 57.6%±9.1%; P = 0.009) sectors. Eyes with LC defects in the IT sector (n = 33) had significantly lower cpVDs than eyes without a defect in the corresponding IT and IN sectors (P < 0.05 for all). Eyes with LC defects in the ST sector (n = 19) had lower cpVDs in the ST, IT, and IN sectors (P < 0.05 for all).ConclusionsIn eyes with similar severity of glaucoma, OCT-A-measured vessel density was significantly lower in POAG eyes with focal LC defects than in eyes without an LC defect. Moreover, reduction of vessel density was spatially correlated with the location of the LC defect.
| S-EPMC5360451 | biostudies-literature
Project description:PurposeTo compare macular and peripapillary vessel density values calculated on optical coherence tomography angiography (OCT-A) images with different algorithms, elaborate conversion formula, and compare the ability to discriminate healthy from affected eyes.MethodsCross-sectional study of healthy subjects, patients with diabetic retinopathy, and glaucoma patients (44 eyes in each group). Vessel density in the macular superficial capillary plexus (SCP), deep capillary plexus (DCP), and the peripapillary radial capillary plexus (RCP) were calculated with seven previously published algorithms. Systemic differences, diagnostic properties, reliability, and agreement of the methods were investigated.ResultsHealthy eyes exhibited higher vessel density values in all plexuses compared to diseased eyes regardless of the algorithm used (p<0.01). The estimated vessel densities were significantly different at all the plexuses (p<0.0001) as a function of method used. Inter-method reliability and agreement was mostly poor to moderate. A conversion formula was available for every method, except for the conversion between multilevel and fixed at the DCP. Substantial systemic, non-constant biases were evident between many algorithms. No algorithm outperformed the others for discrimination of patients from healthy subjects in all the retinal plexuses, but the best performing algorithm varied with the selected plexus.ConclusionsAbsolute vessel density values calculated with different algorithms are not directly interchangeable. Differences between healthy and affected eyes could be appreciated with all methods with different discriminatory abilities as a function of the plexus analyzed. Longitudinal monitoring of vessel density should be performed with the same algorithm. Studies adopting vessel density as an outcome measure should not rely on external normative databases.
| S-EPMC6193681 | biostudies-literature
Project description:PurposeTo evaluate retinal vascular changes in children who have recovered from coronavirus disease (COVID-19) using optical coherence tomography angiography (OCTA) and to compare the results with age-matched healthy children.MethodsIn this cross-sectional case-control study, children 6-18 years of age with laboratory-confirmed SARS-CoV-2 infection were compared with historic healthy controls. All participants underwent ophthalmological examination, including fundus photography and OCTA of the macular region and optic disk. COVID-19 children were examined 4-8 weeks after COVID-19 diagnoses. Demographic data, medical history, and COVID-19 symptoms were noted. OCTA parameters in the superficial capillary plexus (SCP) were analyzed according to ETDRS sectors and peripapillary quadrants.ResultsA total of 72 patients were included: 27 recovered COVID-19 children and 45 controls. Mean age for cases was 11.96 ± 3.8 years (18 females [66%]); for controls, 11.02 ± 2.0 years (29 females [64%]). Macular OCTA of the SCP showed a significant increase in retinal vessel density (VD) in recovered COVID-19 children compared with healthy controls in the inner ring (P = 0.001). Macular perfusion density (mPD) was also increased in the inner ring (P = 0.001). Peripapillary OCTA evidenced a significant higher flux index (FI) in all four quadrants (P < 0.001).ConclusionsRecovered COVID-19 children present increased retinal VD, mPD, and peripapillary FI shortly after recovery. Since the retinal vasculature is considered a unique window to assess microvascular changes, these findings may represent a potential in vivo biomarker of vascular abnormalities in COVID-19 children in other organs.
| S-EPMC8527103 | biostudies-literature
Project description:PurposeTo assess the superficial retinal vessel density (SRVD) and foveal avascular zone (FAZ) in myopic children using optical coherence tomography angiography (OCTA).Methods174 eyes of 89 subjects with myopia and 101 eyes of 54 age-matched, emmetropic volunteers (control group) were enrolled in this study. The mean age of the subjects and controls was 13.9 (SD ± 2.3) and 13.1 (SD ± 2.4), respectively. Myopia was defined as spherical equivalent <- 1.0 diopter. Emmetropic subjects were defined as having spherical equivalent from + 0.5 to - 0.5 diopter. The mean axial length (AL) in myopic patients was 24.58 mm (SD ± 1.22) and 22.88 mm (SD ± 0.65) in the controls. Every patient underwent a complete ophthalmological examination and OCTA, using AngioVue (Optovue). The FAZ area and superficial retinal vessel density, including whole SRVD, fovea SRVD and parafovea SRVD, were analyzed. Foveal thickness (FT) and parafoveal thickness (PFT) were also taken into consideration.ResultsWhole SRVD, parafovea SRVD and PFT were significantly higher in controls than in the myopic subjects (p < 0.001, p = 0.007, p < 0.01, respectively). The FAZ area was significantly larger in the myopic group compared to the controls (p = 0.010). Fovea SRVD and FT did not differ significantly between the groups (p = 0.740, p = 0.795 respectively). In overall subjects we found significant correlation between axial length and all the investigative parameters: age, FAZ area, whole SRVD, parafovea SRVD, fovea SRVD, PFT, FT (p < 0.001, p = 0.014, p = 0.008, p < 0.005, p = 0.014, p = 0.010, p = 0.024, respectively). Analyzing only myopic group we confirmed that AL was significantly correlated with age, whole SRVD and parafovea SRVD (p < 0.001, p = 0.014, p = 0.009, respectively). Similarly, in this group the spherical equivalent also correlated with age, whole SRVD and parafovea SRVD (p < 0.001, p = 0.007, p = 0.005, respectively). Such correlations were not confirmed in the non-myopic group.ConclusionsOur results suggest that superficial retinal vessel density is decreased and FAZ area is enlarged in the entire group of the myopic children compared to emmetropic subjects. Longitudinal observation of these young patients is needed to determine the relevance of the microvascular alterations in future.
| S-EPMC6639003 | biostudies-literature