Showing papers by "Ruikang K. Wang published in 2020"
TL;DR: The automated choroid segmentations were validated against manual segmentations, and MCT measurements were shown to be in good agreement, and choroidal vessel volume and CSV showed significant correlations with MCT (all P < 0.0001).
64 citations
TL;DR: It is recommended that the proper use of the Phansalkar method should include the selection of the window radius that is related to the expected ICD in normal eyes, especially the local window radius of 1-15 pixels.
60 citations
TL;DR: CC perfusion in the macula is decreased in diabetic patients without retinopathy as compared to age-matched normal controls, which may be an early indicator of otherwise clinically undetectable diabetic vasculopathy.
Abstract: Purpose To investigate the microvascular changes in macular retina and choriocapillaris (CC) in diabetic eyes without retinopathy using swept-source optical coherence tomography angiography (SS-OCTA). Methods A commercial SS-OCTA system was used to collect 6 × 6-mm macular scans from patients. Three depth-resolved retinal slabs and a CC slab were segmented by a validated semiautomated algorithm. Retinal vessel area density, vessel skeleton density, and nonperfusion area were calculated on segmented retinal slabs. Foveal avascular zone was automatically measured based on en face image of the whole retinal layer. For CC quantification, the percentage of flow deficits (FD%) and the flow deficit (FD) sizes were measured. Results Sixteen eyes from 16 diabetic patients without clinically detectable retinopathy and 16 eyes from 16 age-matched nondiabetic controls were included. There was no significant difference between the two groups in all retinal vessel quantitative parameters (all P > 0.05). However, the mean FD% and mean FD sizes were significantly increased in CC in the central 1.0-mm disk (P = 0.011 and P = 0.017, respectively), the central 1.5-mm rim (P = 0.003 and P = 0.009, respectively), the central 2.5-mm rim (P = 0.018 and P = 0.020, respectively), and the entire 5.0-mm disk (P = 0.009 and P = 0.008, respectively) in diabetic eyes compared with controls. Conclusions CC perfusion in the macula is decreased in diabetic patients without retinopathy as compared to age-matched normal controls. Decreased CC perfusion in the macula may be an early indicator of otherwise clinically undetectable diabetic vasculopathy.
44 citations
TL;DR: In this article, a nearly-incompressible transversely isotropic (NITI) model depicting corneal biomechanics was proposed, showing that the cornea must be described by at least two shear moduli, contrary to current single-modulus models.
Abstract: The cornea provides the largest refractive power for the human visual system. Its stiffness, along with intraocular pressure (IOP), are linked to several pathologies, including keratoconus and glaucoma. Although mechanical tests can quantify corneal elasticity ex vivo, they cannot be used clinically. Dynamic optical coherence elastography (OCE), which launches and tracks shear waves to estimate stiffness, provides an attractive non-contact probe of corneal elasticity. To date, however, OCE studies report corneal moduli around tens of kPa, orders-of-magnitude less than those (few MPa) obtained by tensile/inflation testing. This large discrepancy impedes OCE’s clinical adoption. Based on corneal microstructure, we introduce and fully characterize a nearly-incompressible transversely isotropic (NITI) model depicting corneal biomechanics. We show that the cornea must be described by at least two shear moduli, contrary to current single-modulus models, decoupling tensile and shear responses. We measure both as a function of IOP in ex vivo porcine cornea, obtaining values consistent with both tensile and shear tests. At pressures above 30 mmHg, the model begins to fail, consistent with non-linear changes in cornea at high IOP.
40 citations
TL;DR: A novel method and system that utilizes a popular smartphone to realize hyperspectral imaging for analyzing skin morphological features and monitoring hemodynamics, and applies Wiener estimation to transform the acquired RGB-mode images into "pseudo"-hyperspectral images with 16 wavebands.
Abstract: We propose a novel method and system that utilizes a popular smartphone to realize hyperspectral imaging for analyzing skin morphological features and monitoring hemodynamics. The imaging system works based on a built-in RGB camera and flashlight on the smartphone. We apply Wiener estimation to transform the acquired RGB-mode images into “pseudo”-hyperspectral images with 16 wavebands, covering a visible range from 470nm to 620nm. The processing method uses weighted subtractions between wavebands to extract absorption information caused by specific chromophores within skin tissue, mainly including hemoglobin and melanin. Based on the extracted absorption information of hemoglobin, we conduct real-time monitoring experiments in the skin to measure heart rate and to observe skin activities during a vascular occlusion event. Compared with expensive hyperspectral imaging systems, the smartphone-based system delivers similar results but with very-high imaging resolution. Besides, it is easy to operate, very cost-effective and has a wider customer base. The use of an unmodified smartphone to realize hyperspectral imaging promises a possibility to bring a hyperspectral analysis of skin out from laboratory and clinical wards to daily life, which may also impact on healthcare in low resource settings and rural areas.
39 citations
TL;DR: In this article, the authors investigated the impact of a deep learning algorithm on the quantification of coronary artery calcium score (CACS) and the stratification of cardiac risk and found no significant differences were found between the manually derived and deep-learning Agatston, mass, and volume scores.
30 citations
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TL;DR: This work introduces and fully characterize a nearly-incompressible transversely isotropic (NITI) model depicting corneal biomechanics, and shows that the cornea must be described by at least two shear moduli, contrary to current single-modulus models, decoupling tensile and shear responses.
Abstract: The cornea provides the largest refractive power for the human visual system Its stiffness, along with intraocular pressure (IOP), are linked to several pathologies, including keratoconus and glaucoma Although mechanical tests can quantify corneal elasticity ex vivo, they cannot be used clinically Optical coherence elastography (OCE), which launches and tracks shear waves to estimate stiffness, provides an attractive non-contact probe of corneal elasticity To date, however, OCE studies report corneal moduli around tens of kPa, orders-of-magnitude less than those (few MPa) obtained by tensile/inflation testing This large discrepancy impedes OCE's clinical adoption Based on corneal microstructure, we introduce and fully characterize a nearly-incompressible transversally isotropic (NITI) model depicting corneal biomechanics We show that the cornea must be described by two shear moduli, contrary to current single-modulus models, decoupling tensile and shear responses We measure both as a function of IOP in ex vivo porcine cornea, obtaining values consistent with both tensile and shear tests At pressures above 30 mmHg, the model begins to fail, consistent with non-linear changes in cornea at high IOP
25 citations
TL;DR: The most peripheral sector of the widefield OCTA (FOV 50°-100°) showed on average higher RNP and showed more diagnostic usefulness in determining DR severity compared with more central sectors and the FOV 100 image as a whole.
23 citations
TL;DR: Peripapillary OCTA vessel parameters had greater intrasession repeatability compared to intersession reproducibility in both non-glaucomatous and glaucom atous eyes.
Abstract: Objective To compare intrasession repeatability versus intersession reproducibility of the peripapillary vessel parameters using optical microangiography–based optical coherence tomography angiography (OCTA) in non-glaucomatous and glaucomatous eyes. Methods In an observational, longitudinal study, peripapillary OCTA scans were collected to evaluate intrasession repeatability and intersession reproducibility using within-eye coefficient of variation (CVW) and intraclass correlation coefficient (ICC). Images were quantified using a custom research–oriented quantification software calculating vessel area density (VAD) and flux and a commercially developed, clinic-oriented quantification software (Cirrus 11.0, Carl Zeiss Meditec) calculating perfusion density (PD) and flux index (FI). Effect of signal strength on the reliability of OCTA parameters was also evaluated. Results Among 120 non-glaucomatous eyes, intrasession CVW were 4.2% for VAD, 5.3% for flux, 1.5% for PD and 2.0% for FI. The intersession CVW were 6.5% for VAD, 8.0% for flux, 2.0% for PD and 3.2% for FI. The intrasession ICC ranged from 0.928 to 0.945, and intersession ICC ranged from 0.811 to 0.866. From 118 glaucomatous eyes, intrasession CVW was 9.0% for VAD, 10.3% for flux, 1.7% for PD and 2.3% for FI. The intersession CVW was 12.1% for VAD, 14.2% for flux, 2.3% for PD and 3.5% for FI. The intrasession ICC ranged from 0.904 to 0.972, and intersession ICC ranged from 0.855 to 0.955. Signal strength was significantly positively associated with OCTA vessel parameters (p Conclusion Peripapillary OCTA vessel parameters had greater intrasession repeatability compared to intersession reproducibility in both non-glaucomatous and glaucomatous eyes. The built-in commercially developed quantification software demonstrated greater agreement than the custom research–oriented quantification software.
22 citations
TL;DR: Automated quantification of CC can identify pathological FDs and provide quantitative metrics describing such lesions in patients with uveitis, and Posterior Uveitis patients have significantly larger CC FDs than patients with other forms of uveita.
20 citations
TL;DR: Excellent correlations between FDa and FD% in regions from 3x3 mm and 6x6 mm scans are found when measuring CC FDs, and further studies are needed to determine if one parameter is more useful when studying diseased eyes.
TL;DR: Ocular magnification significantly affects the results of retinal and CC blood flow quantification with OCTA in myopic eyes, and for accurate determination of the OCTA derived parameters in myopia, magnification correction should be taken into consideration.
Abstract: Background To evaluate the impact of ocular magnification on retinal and choriocapillaris (CC) blood flow quantification in myopic eyes using swept-source optical coherence tomography angiography (SS-OCTA). Methods Subjects with myopia were recruited for comprehensive ophthalmic examination and SS-OCTA imaging with 6×6 mm2 scanning protocol. Retinal vessel area density (RVAD), retinal vessel skeleton density (RVSD), and percentage of CC flow deficits (CC FD%) were quantified within a 5-mm-diameter circle centered on the fovea before and after magnification correction using the Littman and the modified Bennett formulae. Results Images from 28 myopic eyes were qualified for quantitative analyses including 12 eyes with non-high myopia (43%) and 16 eyes with high myopia (57%). The mean spherical equivalent (SE) refractive error was -8.18±4.58 diopters (D) and the mean axial length was 27.9±2.5 mm. The mean corrected RVAD was significantly lower than the uncorrected RVAD in all myopic eyes (0.51±0.02 vs. 0.52±0.02, P<0.001). The mean corrected RVSD was also significantly lower than the uncorrected RVSD in myopic eyes (0.13±0.01 vs. 0.15±0.00, P<0.001). In highly myopic eyes, the mean corrected CC FD% was significantly higher than the uncorrected CC FD% (14.9%±4.9% vs. 14.2%±4.5%, P=0.009). In non-highly myopic eyes, no statistically significant difference was observed between the corrected and uncorrected CC FD% measurements (11.7%±5.8% vs. 11.5%±5.8%, P=0.133). Conclusions Ocular magnification significantly affects the results of retinal and CC blood flow quantification with OCTA in myopic eyes. For accurate determination of the OCTA derived parameters in myopia, magnification correction should be taken into consideration.
TL;DR: Pulsatile TM motion was reduced in patients with POAG compared to healthy subjects, suggesting the underlying mechanism may be due to the altered tissue stiffness or other biomechanical properties of the TM in POAG eyes.
Abstract: Purpose The purpose of this study was to investigate the difference in pulsatile trabecular meshwork (TM) motion between normal and eyes with POAG using phase-sensitive optical coherence tomography (PhS-OCT). Methods In this cross-sectional study, eight healthy subjects (16 eyes) and nine patients with POAG (18 eyes) were enrolled. A laboratory-based prototype PhS-OCT system was used to measure pulsatile TM motion. PhS-OCT images were analyzed to obtain parameters of pulsatile TM motion (i.e. maximum velocity [MV] and cumulative displacement [CDisp]). Outflow facility and ocular pulse amplitude were measured using pneumotonography. Detection sensitivity was compared among various parameters by calculating the area under the receiver operating characteristic curves (AUCs). Results A pulsatile TM motion waveform synchronous with digital pulse was observed using PhS-OCT in both healthy and POAG eyes. The mean MV in eyes with glaucoma was significantly lower than healthy eyes (P < 0.001). The mean CDisp in POAG eyes was also significantly lower than healthy eyes (P < 0.001). CDisp showed a significant correlation (r = 0.46; P = 0.0088) with ocular pulse amplitude in the study. Compared with the outflow facility, both the MV and CDisp were found to have a better discrimination of glaucoma (P < 0.001 and P = 0.0074, respectively). Conclusions Pulsatile TM motion was reduced in patients with POAG compared to healthy subjects. The underlying mechanism may be due to the altered tissue stiffness or other biomechanical properties of the TM in POAG eyes. Our evidence suggests that the measurement of pulsatile TM motion with PhS-OCT may help in characterizing outflow pathway abnormalities.
TL;DR: In the macular region, both CC FD% and CC FD size are increased in eyes with DR, and SS-OCTA provides new insights for the investigations of CC perfusion status in diabetes in vivo.
Abstract: Purpose
To quantitatively assess choriocapillaris (CC) flow deficits in eyes with diabetic retinopathy (DR) using swept-source optical coherence tomography angiography (SS-OCTA).
Methods
Diabetic subjects with different stages of DR and age-matched healthy subjects were recruited and imaged with SS-OCTA. The en face CC blood flow images were generated using previously published and validated algorithms. The percentage of CC flow deficits (FD%) and the mean CC flow deficit size were calculated in a 5-mm-diameter circle centered on the fovea from the 6×6-mm scans.
Results
Forty-five diabetic subjects and 27 control subjects were included in the study. The CC FD% in diabetic eyes was on average 1.4-fold greater than in control eyes (12.34±4.14% vs 8.82±2.61%, P < 0.001). The mean CC FD size in diabetic eyes was on average 1.4-fold larger than in control eyes (2151.3± 650.8μm2 vs 1574.4±255.0 μm2, P < 0.001). No significant difference in CC FD% or mean CC FD size was observed between eyes with nonproliferative DR and eyes with proliferative DR (P = 1.000 and P = 1.000, respectively).
Conclusions
CC perfusion in DR can be objectively and quantitatively assessed with FD% and FD size. In the macular region, both CC FD% and CC FD size are increased in eyes with DR. SS-OCTA provides new insights for the investigations of CC perfusion status in diabetes in vivo.
TL;DR: Correlation between CC thickness and choroid thickness suggests that the CC thins with the overall thinning of the choroids, and metrics should be useful to reveal more morphological details of RPE-BM-CC complex.
Abstract: We report the development of an automated method to measure morphological features of the retinal pigment epithelium (RPE), Bruch’s membrane (BM) and choriocapillaris (CC) using a commercially available swept source OCT (SS-OCT) system. The locations of the inner segment/outer segment (IS/OS), RPE and CC were determined by optical coherence tomography (OCT) and OCT angiography (OCTA) A-scan intensity profiles, which were used to calculate the mean IS/OS-to-RPE distance, mean RPE-to-CC distance, mean RPE-to-CC outer boundary distance, mean RPE thickness and mean CC thickness across the entire scan volume. The automated method was tested on two groups of normal subjects: younger age group (n=20, 30.3 ± 5.72 years, axial length = 24.2 ± 0.96 mm) and older age group (n=20, 80.8 ± 4.12 years, axial length = 23.5 ± 0.93 mm). The 6×6 mm macular scans were acquired from one eye of each subject. Repeatability of the measurements showed a coefficient of variance < 5% for all the cases. CC locations were confirmed qualitatively with pixel-by-pixel moving of the en face OCT/OCTA images. Relative distance and thickness maps of the RPE-BM-CC complex were generated for visualization of regional changes. We observed thinner CC, thinner RPE and increased RPE-to-CC distance in the older age group. Correlation between CC thickness and choroid thickness suggests that the CC thins with the overall thinning of the choroid. These metrics should be useful to reveal more morphological details of RPE-BM-CC complex, provide a better understanding of the CC in three dimensions, and further investigate potential functional relationships between RPE, BM and CC, and their involvement in age-related ocular diseases.
TL;DR: The proposed 3D registration and averaging method is effective in reducing speckle noises and suppressing motion artifacts, thereby improving SNR, PSNR and NCC metrics for final averaged images.
Abstract: Background In the clinical applications of optical coherence tomography angiography (OCTA), the repeated scanning and averaging method can provide better contrast with reduced speckle noises in the final results, which are useful for visualizing and quantifying vascular components with high accuracy, reproducibility, and reliability. However, the inevitable patient motion presents a challenge to this method. The objective of this study is to meet this challenge by introducing a 3D registration method to register optical coherence tomography (OCT)/OCTA scans for precise volume averaging of multiple scans to improve the signal-to-noise ratio (SNR) and increase quantification accuracy. Methods The proposed method utilized both rigid affine transformation and non-rigid B-spline transformation in which their parameters were optimized and calculated by the average stochastic gradient descent on OCT structural images. In addition, we also introduced a multi-level resolution approach to further improve the robustness and computational speed of our proposed method. The imaging performance was tested on in vivo imaging of human skin and eye and assessed by SNR, peak signal-to-noise ratio (PSNR) and normalized correlation coefficient (NCC). Results Five subjects were enrolled in this study for obtaining in vivo images of skin and retina. The proposed registration and averaging method provided substantial improvements of the imaging performance in terms of vessel connectivity and signal to noise ratio. The increase of repeated volume numbers in the averaging improves all the metrics assessed, i.e., SNR, PSNR and NCC. An improvement of the SNR from 10 to 40 dB after 10 repeated volumetric averaging was achieved. Conclusions The proposed 3D registration and averaging method is effective in reducing speckle noises and suppressing motion artifacts, thereby improving SNR, PSNR and NCC metrics for final averaged images. It is expected that the proposed algorithm would be practically useful in better visualization and more reliable quantification of in vivo OCT and OCTA data, which would be beneficial to OCT clinical applications.
TL;DR: The data suggest that increased macular flow may be an early biomarker of visual field loss in ODD, while decreased peripapillary vessel density and RNFL thickness are late biomarkers of visual Field Loss in O DD.
TL;DR: Investigation of layer specific retinal vascular reactivity in capillaries of diabetic subjects without DR or with only mild non-proliferative diabetic retinopathy found impairments in RVR seem to occur early in the disease and to be driven primarily at the capillary level.
Abstract: Purpose
To investigate layer specific retinal vascular reactivity (RVR) in capillaries of diabetic subjects without DR or with only mild non-proliferative diabetic retinopathy (NPDR).
Methods
A previously described nonrebreathing apparatus was used to deliver room air, 5% CO2, or 100% O2 to 41 controls and 22 diabetic subjects (with mild or no NPDR) while simultaneously acquiring fovea-centered 3x3mm2 Swept-Source Optical Coherence Tomography Angiography (SS-OCTA) images. Vessel skeleton density (VSD) and vessel diameter index (VDI) were calculated for each gas condition for the superficial retinal layer (SRL) and deep retinal layer (DRL). The superficial layer analysis excluded arterioles and venules. Data analysis was performed using mixed factorial analysis of covariance stratified by diabetic status. All models were adjusted for age, gender, and hypertension, and statistical significance for multiple comparisons from posthoc comparisons were defined at p<0.017.
Results
Among controls, there was a significant difference in capillary VSD between all gas conditions (p<0.001). This difference was present in both the SRL and DRL. Among diabetics, there was no significant difference in response to CO2 conditions in the SRL (p = 0.072), and a blunted response to both CO2 (p = 0.9) and O2 in the DRL (p = 0.019). A significant gas effect was detected in the capillary VDI in the SRL of controls (p = 0.001), which was driven by higher VDI in the oxygen condition compared to that of carbon dioxide.
Conclusions
Impairment in RVR in diabetic subjects is characterized by a paradoxical response to CO2 in both the SRL and DRL as well as an attenuated response to O2 in the DRL. These layer and gas specific impairments in diabetics seem to occur early in the disease and to be driven primarily at the capillary level.
TL;DR: A method to detect relative flow velocity in human retina using a 67.5 kHz spectral-domain OCTA device is reported, adapting the selection of A-scan time-intervals within a single OCTA acquisition and combining the resulting OCTA images to expand the detectable velocity range.
Abstract: Optical coherence tomography angiography (OCTA) imaging is a valuable tool for the visualization of retinal vasculature at an unprecedented level of details. However, due to relatively long time-interval between repeated scans in the conventional OCTA scanning protocol, the OCTA flow signal suffers from low dynamic range and loss of velocity-intensity correlation. The ability to distinguish fast and slow flow in the retina may provide a powerful tool for the assessment of early-stage retinal diseases such as vein occlusion. Here, we report a method to detect relative flow velocity in human retina using a 67.5 kHz spectral-domain OCTA device. By adapting the selection of A-scan time-intervals within a single OCTA acquisition and combining the resulting OCTA images, we expand the detectable velocity range. After a quantitative validation of this method performing microchannel flow experiments with varying flow velocities, we demonstrate this approach on human eyes using CIRRUS HD-OCT 5000 with AngioPlex (ZEISS, Dublin, CA) through a prototype scanning pattern.
TL;DR: In this naturally occurring experiment in which drusen collapsed without evidence of disease progression, the CC parameters were similar once the compensation strategy was applied both before and after thedrusen resolved.
TL;DR: P polarization-sensitive optical coherence tomography (PS-OCT) is demonstrated to image microvascular information within a living sample without polarization induced artifacts in OCTA vascular imaging.
Abstract: When imaging birefringent samples using optical coherence tomography angiography (OCTA), the phase retardation may appear opposite to the phase change due to the blood flow in the orthogonal signals, for which a cancellation effect can occur when deriving OCTA signals. This effect can diminish the ability of OCTA to detect vascular information, leading to an erroneous interpretation of the final OCTA images. To mitigate this issue, we demonstrate polarization-sensitive optical coherence tomography (PS-OCT) to image microvascular information within a living sample without polarization induced artifacts. The system is furnished with a swept source OCT (SS-OCT) that incorporates two imaging modes: OCTA imaging and polarization-sensitive imaging. PS-OCT is used to provide birefringent contrast where the color-encoded Stokes parameters are used to obtain high contrast polarization-state images. OCTA is used to acquire high-resolution images of functional microvascular networks permeating the scanned tissue volume. Taking the advantages of the dual-channel PS-OCT configuration, the polarization induced artifacts are eliminated from OCTA vascular imaging. The proposed PS-OCTA system is employed to visualize the birefringent components and the vascular networks of the human skin in vivo. It is expected that the proposed system setup would have useful and practical applications in the investigations of the vasculature in the birefringent tissue samples both pre-clinically and clinically.
TL;DR: The method presented here will facilitate optical recording in the awake, active mice and open the door to many projects that can bridge the hemodynamics in neurovascular units to naturalistic behavior.
Abstract: We describe a method and procedure that allows for the optical coherence tomography angiography (OCTA) and intrinsic optical signal imaging (IOSI) of cerebral blood flow and hemodynamics in fully awake mice. We detail the procedure of chronic cranial window preparation, the use of an air-lift mobile homecage to achieve stable optical recording in the head-restrained awake mouse, and the imaging methods to achieve multiparametric hemodynamic measurements. The results show that by using a collection of OCTA algorithms, the high-resolution cerebral vasculature can be reliably mapped at a fully awake state, including flow velocity measurements in penetrating arterioles and capillary bed. Lastly, we demonstrate how the awake imaging paradigm is used to study cortical hemodynamics in the mouse barrel cortex during whisker stimulation. The method presented here will facilitate optical recording in the awake, active mice and open the door to many projects that can bridge the hemodynamics in neurovascular units to naturalistic behavior.
TL;DR: GA expansion rate and CC FV density throughout the macular region and surrounding the GA margin were significantly correlated, and the regional magnitude of FV immediately surrounding GA was associated with GA growth into that region.
Abstract: Author(s): Nattagh, Khashayar; Zhou, Hao; Rinella, Nicholas; Zhang, Qinqin; Dai, Yining; Foote, Katharina G; Keiner, Cathrine; Deiner, Michael; Duncan, Jacque L; Porco, Travis C; Wang, Ruikang K; Schwartz, Daniel M | Abstract: PurposeTo investigate the relationship between choriocapillaris (CC) flow void (FV) percentage and geographic atrophy (GA) growth rate, and study how variations in FV percentage surrounding GA predict regional GA growth.MethodsThis prospective, longitudinal study enrolled subjects with GA secondary to nonexudative age-related macular degeneration. Optical coherence tomography angiography imaged the CC and FV percentage was evaluated using a validated algorithm. GA growth rate was measured as the difference in the square root of GA area divided by the months between baseline and follow-up imaging.ResultsTwelve eyes from 7 subjects with a mean age of 80 ± 5 years (range 74-86) were studied once at baseline and 7 to 16 months later. GA expansion rate was positively correlated with increased CC FV percentage (Spearman rank correlation coefficient r = 0.69 [P = 0.038] and 0.76 [P = 0.013]) within the 6 x 6 mm scanned macular region and the 2° margin surrounding each GA lesion, respectively. Regions with CC FV at baseline located within 480 µm from the GA margin showed 33% greater chance of becoming atrophic compared with regions within 480 µm from the GA margin that did not show CC FV at baseline.ConclusionsGA expansion rate and CC FV density throughout the macular region and surrounding the GA margin were significantly correlated. The regional magnitude of FV immediately surrounding GA was associated with GA growth into that region.Translational relevanceCC FV analysis may facilitate prediction of GA growth over time for patients with advanced nonneovascular age-related macular degeneration.
13 Aug 2020
TL;DR: OCTA can quantify and monitor EPB-induced retinopathy and can detect vascular abnormalities even without clinically observable retinopathies, and may be useful in investigating treatment interventions aiming to delay EP B-induced radiation Retinopathy.
Abstract: Purpose:This work assesses longitudinal microvascular changes in eyes treated with iodine-125 episcleral plaque brachytherapy (EPB).Methods:High-resolution optical coherence tomography angiograms (...
TL;DR: Large- and small-vessel parameters were associated with prematurity and ROP severity, respectively and handheld SS-OCTA achieved adequate signal-to-noise ratio in nonsedated infants for quantitative retinal vascular parameter analysis.
Abstract: Purpose To compare retinal vascular parameters acquired by handheld swept-source optical coherence tomography angiography (SS-OCTA) between nonsedated preterm and full-term infants. Methods Preterm and full-term infants at the University of Washington Medical Center were enrolled. Retinal angiograms (nominal size ∼7 × 7 mm2) were obtained at each routine retinopathy of prematurity (ROP) screening session for preterms and once during the first 72 hours of life for full-terms. Macular vessel area density and nonperfusion area were evaluated on the binarized vasculature map in both small (1.5 × 1.5 mm) and large (3 × 3 mm) quadrants. Average vessel diameter and tortuosity values were obtained from each large vessel branch (length >200 µm). All vascular analyses used previously published algorithms. Results Handheld SS-OCTA captured 31 of 55 (56%) high-quality volumes on 8 awake preterm infants (gestational age 28 ± 4 weeks, birth weight 891 ± 314 g, postmenstrual age at first imaging session 37 ± 2 weeks) and 48 of 54 (89%) volumes on 12 awake full-term infants (gestational age 39 ± 1 weeks, birth weight 3405 ± 329 g). Signal-to-noise ratio was 5.08 ± 1.52 dB in preterm and 4.90 ± 1.12 dB in full-term infants. Preterm infants had higher mean large vessel tortuosity compared to full-term infants (P = 0.004). The large nasal quadrant vessel area density of infants with stage 3 and/or pre-plus or worse ROP was higher than other preterm infants (P = 0.007). Conclusions Although inadequate image quality limited usable imaging sessions, handheld SS-OCTA achieved adequate signal-to-noise ratio in nonsedated infants for quantitative retinal vascular parameter analysis. Translational relevance Large- and small-vessel parameters were associated with prematurity and ROP severity, respectively.
TL;DR: An image processing technique based on mean subtraction of the depth profile can effectively reduce these tails to better reveal small hidden vessels compared to the current tail removal approach and can provide better visualization of three-dimensional vascular network topology for quantitative cerebrovascular studies.
Abstract: When imaging brain vasculature with optical coherence tomography angiography (OCTA), volumetric analysis of cortical vascular networks in OCTA datasets is frequently challenging due to the presence of artifacts, which appear as multiple-scattering tails beneath superficial large vessels in OCTA images. These tails shadow underlying small vessels, making the assessment of vascular morphology in the deep cortex difficult. In this work, we introduce an image processing technique based on mean subtraction of the depth profile that can effectively reduce these tails to better reveal small hidden vessels compared to the current tail removal approach. With the improved vascular image quality, we demonstrate that this simple method can provide better visualization of three-dimensional vascular network topology for quantitative cerebrovascular studies.
TL;DR: It is suggested that the extent of native leptomeningeal collaterals affects downstream hemodynamics with a long lasting impact in the microvascular bed after cortical stroke with a slight improvement of cortical perfusion seven days after MCAO.
Abstract: The leptomeningeal collateral status is an independent predictor of stroke outcome. By means of optical coherent tomography angiography to compare two mouse strains with different extent of native ...
TL;DR: A semi-automated registration and segmentation method for micrometer resolution measurement of gingival-tissue volume is proposed for 3D optical coherence tomography (OCT) imaging.
Abstract: The change in gingival tissue volume may be used to indicate changes in gingival inflammation, which may be useful for the clinical assessment of gingival health. Properly quantifying gingival tissue volume requires a robust technique for accurate registration and segmentation of longitudinally captured 3-dimensional (3D) images. In this paper, a semi-automated registration and segmentation method for micrometer resolution measurement of gingival-tissue volume is proposed for 3D optical coherence tomography (OCT) imaging. For quantification, relative changes in gingiva tissue volume are measured based on changes in the gingiva surface height using the tooth surface as a reference. This report conducted repeatability tests on this method drawn from repeated scans in one patient, indicating an error of the point cloud registration method for oral OCT imaging is 63.08 ± 4.52µm (1σ), and the measurement error of the gingival tissue average thickness is -3.40 ± 21.85µm (1σ).
TL;DR: The activated region revealed in the cross-sectional OCT image is consistent with that identified by the IOSI imaging, indicating the phase change in the OCT signals may associate with the changes in the corresponding hemodynamics.
Abstract: We describe a method to measure tissue dynamics in mouse barrel cortex during functional activation via phase-sensitive optical coherence tomography (PhS-OCT). The method measures the phase changes in OCT signals, which are induced by the tissue volume change, upon which to localize the activated tissue region. Phase unwrapping, compensation and normalization are applied to increase the dynamic range of the OCT phase detection. To guide the OCT scanning, intrinsic optical signal imaging (IOSI) system equipped with a green light laser source (532 nm) is integrated with the PhS-OCT system to provide a full field time-lapsed images of the reflectance that is used to identify the transversal 2D localized tissue response in the mouse brain. The OCT results show a localized decrease in the OCT phase signal in the activated region of the mouse brain tissue. The decrease in the phase signal may be originated from the brain tissue compression caused by the vasodilatation in the activated region. The activated region revealed in the cross-sectional OCT image is consistent with that identified by the IOSI imaging, indicating the phase change in the OCT signals may associate with the changes in the corresponding hemodynamics. In vivo localized tissue dynamics in the barrel cortex at depth during whisker stimulation is observed and monitored in this study.
TL;DR: The newly designed OCT‐LIAF system maintained the ability to detect differences between healthy and hypomineralized teeth, identify dental biofilm and visualize the microvasculature of gingival tissue.
Abstract: We report the development of an integrated multifunctional imaging system capable of providing anatomical (optical coherence tomography, OCT), functional (OCT angiography, OCTA) and molecular imaging (light-induced autofluorescence, LIAF) for in vivo dental applications. Blue excitation light (405 nm) was used for LIAF imaging, while the OCT was powered by a 1310 nm swept laser source. A red-green-blue digital camera, with a 450 nm cut-on broadband optical filter, was used for LIAF detection. The exciting light source and camera were integrated directly with the OCT scanning probe. The integrated system used two noninvasive imaging modalities to improve the speed of in vivo OCT data collection and to better target the regions of interest. The newly designed system maintained the ability to detect differences between healthy and hypomineralized teeth, identify dental biofilm and visualize the microvasculature of gingival tissue. The development of the integrated OCT-LIAF system provides an opportunity to conduct clinical studies more efficiently, examining changes in oral conditions over time.