Interobserver Agreement in Detecting Spectral-Domain Optical Coherence Tomography Features of Diabetic Macular Edema

PurposeTo evaluate interobserver agreement for the detection of spectral-domain optical coherence tomography (SDOCT) features of diabetic macular edema (DME).MethodCross-sectional study in which 2 retinal specialists evaluated SDOCT scans from eyes receiving treatment for DME. Scans from 50 eyes with DME of 39 patients were graded for features of DME including intra-retinal fluid (IRF), diffuse retinal oedema (DRE), hyper-reflective foci (HRF), subretinal fluid (SRF), macular fluid and vitreomacular traction (VMT). Features were graded as present or absent at zones involving the fovea, 1mm from the fovea and the whole scan of 49 line scans. Analysis was performed using cross-tabulations for percentage concordance and kappa values (κ).ResultsIn the 2950 line scans analysed, there was an increase in percentage concordance for DRE and HRF when moving from a foveal line scan, 1mm zone and then to a whole scan analysis (88% vs 94% vs 96%) and (88% vs 94% vs 94%) respectively with κ ranging from substantial to almost perfect. Percentage concordance for SRF was 96% at all 3 regions analysed, whilst IRF was 96% at fovea and 98% at higher number of line-scans analysed. Concordance for MF was 100% at fovea and 98% at 1mm zone and whole scan with almost perfect and substantial κ respectively. κ agreement was substantial for VMT at all regions analysed.ConclusionWe report a high level of interobserver agreement in the detection of SDOCT features of DME. This finding is important as detection of macular fluid is used to guide retreatment with anti-angiogenic agents.     

Age-Related Vitamin D Deficiency Is Associated with Reduced Macular Ganglion Cell Complex: A Cross-Sectional High-Definition Optical Coherence Tomography Study

Background

Vitamin D deficiency is associated with smaller volume of optic chiasm in older adults, indicating a possible loss of the visual axons and their cellular bodies. Our objective was to determine whether vitamin D deficiency in older adults is associated with reduced thickness of the ganglion cell complex(GCC) and of the retinal nerve fibre layer(RNFL), as measured with high-definition optical coherence tomography(HD-OCT).

Methods

Eighty-five French older community-dwellers without open-angle glaucoma and patent age-related macular degeneration(mean, 71.1±4.7years; 45.9%female) from the GAIT study were separated into 2 groups according to serum 25OHD level(i.e., deficient≤25nmol/L or sufficient>25nmol/L). Measurements of GCC and RNFL thickness were performed using HD-OCT. Age, gender, body mass index, number of comorbidities, dementia, functional autonomy, intracranial volume, visual acuity, serum calcium concentration and season of testing were considered as potential confounders.

Results

Mean serum 25OHD concentration was 58.4±26.8nmol/L. Mean logMAR visual acuity was 0.03±0.06. Mean visual field mean deviation was -1.25±2.29dB. Patients with vitamin D deficiency(n=11) had a reduced mean GCC thickness compared to those without vitamin D deficiency(72.1±7.4μm versus 77.5±7.5μm, P=0.028). There was no difference of the mean RNFL thickness in these two groups(P=0.133). After adjustment for potential confounders, vitamin D deficiency was associated with reduced GCC thickness(ß=-5.12, P=0.048) but not RNFL thickness(ß=-9.98, P=0.061). Specifically, vitamin D deficiency correlated with the superior medial GCC area(P=0.017) and superior temporal GCC area(P=0.010).

Conclusions

Vitamin D deficiency in older patients is associated with reduced mean GCC thickness, which can represent an early stage of optic nerve damage, prior to RNFL loss.     

Diagnostic Ability of Macular Ganglion Cell Inner Plexiform Layer Measurements in Glaucoma Using Swept Source and Spectral Domain Optical Coherence Tomography

PurposeTo evaluate the diagnostic ability of macular ganglion cell and inner plexiform layer measurements in glaucoma, obtained using swept source (SS) and spectral domain (SD) optical coherence tomography (OCT) and to compare to circumpapillary retinal nerve fiber layer (cpRNFL) thickness measurements.MethodsThe study included 106 glaucomatous eyes of 80 subjects and 41 eyes of 22 healthy subjects from the Diagnostic Innovations in Glaucoma Study. Macular ganglion cell and inner plexiform layer (mGCIPL), macular ganglion cell complex (mGCC) and cpRNFL thickness were assessed using SS-OCT and SD-OCT, and area under the receiver operating characteristic curves (AUCs) were calculated to determine ability to differentiate glaucomatous and healthy eyes and between early glaucomatous and healthy eyes.ResultsMean (± standard deviation) mGCIPL and mGCC thickness were thinner in both healthy and glaucomatous eyes using SS-OCT compared to using SD-OCT. Fixed and proportional biases were detected between SS-OCT and SD-OCT measures. Diagnostic accuracy (AUCs) for differentiating between healthy and glaucomatous eyes for average and sectoral mGCIPL was similar in SS-OCT (0.65 to 0.81) and SD-OCT (0.63 to 0.83). AUCs for average cpRNFL acquired using SS-OCT and SD-OCT tended to be higher (0.83 and 0.85, respectively) than for average mGCC (0.82 and 0.78, respectively), and mGCIPL (0.73 and 0.75, respectively) but these differences did not consistently reach statistical significance. Minimum SD-OCT mGCIPL and mGCC thickness (unavailable in SS-OCT) had the highest AUC (0.86) among macular measurements.ConclusionAssessment of mGCIPL thickness using SS-OCT or SD-OCT is useful for detecting glaucomatous damage, but measurements are not interchangeable for patient management decisions. Diagnostic accuracies of mGCIPL and mGCC from both SS-OCT and SD-OCT were similar to that of cpRNFL for glaucoma detection.     

基于谱域相干的细胞动态检测技术

将谱域光学相干层析技术（Spectral-domain Optical Coherence Tomography,SD-OCT）应用于细胞膜厚的动态检测,引入了光谱干涉测量方法,通过对干涉光谱信号进行离散傅里叶变换得到表示物体深度位置信息的光程差信号。搭建了一套SD-OCT测量系统并设计了专门用于细胞检测的样品平台,检测精度达到μm量级,信噪比达70 db,是一种快速、实时、非接触的细胞分子膜厚动态检测技术。     

Real-Time Automatic Segmentation of Optical Coherence Tomography Volume Data of the Macular Region

Optical coherence tomography (OCT) is a high speed, high resolution and non-invasive imaging modality that enables the capturing of the 3D structure of the retina. The fast and automatic analysis of 3D volume OCT data is crucial taking into account the increased amount of patient-specific 3D imaging data. In this work, we have developed an automatic algorithm, OCTRIMA 3D (OCT Retinal IMage Analysis 3D), that could segment OCT volume data in the macular region fast and accurately. The proposed method is implemented using the shortest-path based graph search, which detects the retinal boundaries by searching the shortest-path between two end nodes using Dijkstra’s algorithm. Additional techniques, such as inter-frame flattening, inter-frame search region refinement, masking and biasing were introduced to exploit the spatial dependency between adjacent frames for the reduction of the processing time. Our segmentation algorithm was evaluated by comparing with the manual labelings and three state of the art graph-based segmentation methods. The processing time for the whole OCT volume of 496×644×51 voxels (captured by Spectralis SD-OCT) was 26.15 seconds which is at least a 2-8-fold increase in speed compared to other, similar reference algorithms used in the comparisons. The average unsigned error was about 1 pixel (∼ 4 microns), which was also lower compared to the reference algorithms. We believe that OCTRIMA 3D is a leap forward towards achieving reliable, real-time analysis of 3D OCT retinal data.     

Non-Invasive Detection of Early Retinal Neuronal Degeneration by Ultrahigh Resolution Optical Coherence Tomography

Optical coherence tomography (OCT) has revolutionises the diagnosis of retinal disease based on the detection of microscopic rather than subcellular changes in retinal anatomy. However, currently the technique is limited to the detection of microscopic rather than subcellular changes in retinal anatomy. However, coherence based imaging is extremely sensitive to both changes in optical contrast and cellular events at the micrometer scale, and can generate subtle changes in the spectral content of the OCT image. Here we test the hypothesis that OCT image speckle (image texture) contains information regarding otherwise unresolvable features such as organelle changes arising in the early stages of neuronal degeneration. Using ultrahigh resolution (UHR) OCT imaging at 800 nm (spectral width 140 nm) we developed a robust method of OCT image analyses, based on spatial wavelet and texture-based parameterisation of the image speckle pattern. For the first time we show that this approach allows the non-invasive detection and quantification of early apoptotic changes in neurons within 30 min of neuronal trauma sufficient to result in apoptosis. We show a positive correlation between immunofluorescent labelling of mitochondria (a potential source of changes in cellular optical contrast) with changes in the texture of the OCT images of cultured neurons. Moreover, similar changes in optical contrast were also seen in the retinal ganglion cell- inner plexiform layer in retinal explants following optic nerve transection. The optical clarity of the explants was maintained throughout in the absence of histologically detectable change. Our data suggest that UHR OCT can be used for the non-invasive quantitative assessment of neuronal health, with a particular application to the assessment of early retinal disease.     

Visualization of Plant Tissues by Optical Coherence Tomography

The internal structure of plant tissues was visualized with optical coherence tomography (OCT). This noninvasive method is suitable for examining intact plants; it produces two-dimensional images of plant tissues at a penetration depth of 1–2 mm from the surface. The potential use of OCT was assessed on Tradescantia blossfeldiana Mild. Plant tissue images measuring 1.5 × 2 mm were obtained in vivo with a spatial resolution of 15 m. The radiation power incident on a sample was 0.5 mW. The acquisition of a two-dimensional image consisting of 200 × 200 pixels required 1–3 s. The OCT method can be used to visualize not only plant tissues and tissue boundaries but also the structure of individual cells.     

Keratometric Index Obtained by Fourier-Domain Optical Coherence Tomography

Purpose

To determine the keratometric indices calculated based on parameters obtained by Fourier-domain optical coherence tomography (FD-OCT).

Methods

The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes. The total corneal powers were calculated using different keratometric indices: K_cal based on the mean calculated keratometric index, K_1.3315 calculated by the keratometric index of 1.3315, and K_1.3375 calculated by the keratometric index of 1.3375. In addition, the total corneal powers based on Gaussian optics formula (K_actual) were calculated.

Results

The means for Ratio in untreated controls, post-LASIK/PRK group and keratoconus group were 1.176 ± 0.022 (95% confidence interval (CI), 1.172–1.179), 1.314 ± 0.042 (95%CI, 1.303–1.325) and 1.229 ± 0.118 (95%CI, 1.191–1.267), respectively. And the mean calculated keratometric index in untreated controls, post-LASIK/PRK group and keratoconus group were 1.3299 ± 0.00085 (95%CI, 1.3272–1.3308), 1.3242 ± 0.00171 (95%CI, 1.3238–1.3246) and 1.3277 ± 0.0046 (95%CI, 1.3263–1.3292), respectively. All the parameters were normally distributed. The differences between K_cal and K_actual, K_1.3315 and K_actual, and K_1.3375 and K_actual were 0.00 ± 0.11 D, 0.21 ± 0.11 D and 0.99 ± 0.12 D, respectively, in untreated controls; -0.01 ± 0.20 D, 0.85 ± 0.18 D and 1.56 ± 0.16 D, respectively, in post-LASIK/PRK group; and 0.03 ± 0.67 D, 0.56 ± 0.70 D and 1.40 ± 0.76 D, respectively, in keratoconus group.

Conclusion

The calculated keratometric index is negatively related to the ratio of anterior corneal curvature to posterior corneal curvature in untreated, post-LASIK/PRK, and keratoconus eyes, respectively. Using the calculated keratometric index may improve the prediction accuracies of total corneal powers in untreated controls, but not in post-LASIK/PRK and keratoconus eyes.     

Vitreous Hyper-Reflective Dots in Optical Coherence Tomography and Cystoid Macular Edema after Uneventful Phacoemulsification Surgery

Purpose

To report the observation of hyper-reflective dots in the vitreous cavity using spectral domain optical coherence tomography (SD-OCT) after uneventful phacoemulsification cataract surgery and to investigate their association with cystoid macular edema (CME).

Materials and Methods

Medical records of consecutive Asian patients who had no preoperative retinopathy and underwent uneventful phacoemulsification cataract surgery from March 2012 through February 2013 were reviewed. SD-OCTs were performed before, 1 week, and 1 month after surgery. The number of vitreous hyper-reflective dots (VHDs) was counted in 5 OCT images of high-definition 5-line raster scans. The development of CME was assessed using postoperative 1-month OCT.

Results

In 74 eyes of 74 patients, all of three SD-OCTs with a signal to noise ratio of 0.6 or more were available and were analyzed in this study. In preoperative OCT, the VHD was observed in 2 (2.7%) of 74 eyes; one eye had 1 VHD and the other eye had 2 VHDs. In 72 eyes with no preoperative VHD, VHDs were observed in 40 (55.6%) eyes at 1 week after the surgery. In the multivariate analysis, the number of VHDs measured at 1 week after the surgery was significantly associated with CME development at 1 month after the surgery (odds ratio = 1.93, 95% confidence interval = 1.15 to 3.24, P = 0.012).

Conclusions

VHDs were frequently observed in OCT after uneventful phacoemulsification cataract surgery. VHDs observed at 1 week after the surgery may be a risk factor for the development of pseudophakic CME. Further studies are needed to identify the source of the VHDs.     

OCT于大鼠脱水组织中光散射特性的分析研究

目的:探讨活体组织液体含量的改变对OCT成像的影响,以期提高OCT在诊断组织病理性质方面的能力。方法:实验中复制脱水大鼠病理模型,应用光学相干层析成像设备,进行大鼠舌浅表组织在体显微成像检测,并对图像中组织的信号衰减特性进行量化分析。结果:正常对照组大鼠体重明显增加,病理模型组显著下降,病理模型组于脱水3天和5天后组织的平均OCT信号衰减系数明显高于正常对照组(P<0.01),且5天较3天的病理模型组组织的信号衰减系数变化尤其显著(P<0.01)。结论:改变组织含液量,可显著改变OCT成像效果,且通过对OCT图像中信号的衰减系数分析,可获得组织细微的散射变化,从而有望提高OCT技术在组织性质方面的诊断能力。     

Tissue-Specific Optical Mapping Models of Swine Atria Informed by Optical Coherence Tomography

Computational models and experimental optical mapping of cardiac electrophysiology serve as powerful tools to investigate the underlying mechanisms of arrhythmias. Modeling can also aid the interpretation of optical mapping signals, which may have different characteristics with respect to the underlying electrophysiological signals they represent. However, despite the prevalence of atrial arrhythmias such as atrial fibrillation, models of optical electrical mapping incorporating realistic structure of the atria are lacking. Therefore, we developed image-based models of atrial tissue using structural information extracted from optical coherence tomography (OCT), which can provide volumetric tissue characteristics in high resolution. OCT volumetric data of four swine atrial tissue samples were used to develop models incorporating tissue geometry, tissue-specific myofiber orientation, and ablation lesion regions. We demonstrated the use of these models through electrophysiology and photon scattering simulations. Changes in transmural electrical conduction were observed with the inclusion of OCT-derived, depth-resolved fiber orientation. Additionally, the amplitude of optical mapping signals were not found to correspond with lesion transmurality because of lesion geometry and electrical propagation occurring beyond excitation light penetration. This work established a framework for the development of tissue-specific models of atrial tissue derived from OCT imaging data, which can be useful in future investigations of electrophysiology and optical mapping signals with respect to realistic atrial tissue structure.     

Optical Coherence Tomography for live imaging of mammalian development

Understanding the nature and mechanism of congenital defects of the different organ systems in humans has heavily relied on the analysis of the corresponding mutant phenotypes in rodent models. Optical Coherence Tomography (OCT) has recently emerged as a powerful tool to study early embryonic development. This non-invasive optical methodology does not require labeling and allows visualization of embryonic tissues with single cell resolution. Here, we will discuss how OCT can be applied for structural imaging of early mouse and rat embryos in static culture, cardiodynamic and blood flow analysis, and in utero embryonic imaging at later stages of gestation, demonstrating how OCT can be used to assess structural and functional birth defects in mammalian models.     

Growth Kinetics of Concave Nanocubes Studied by Optical Coherence Tomography

This work presents the analysis of the growth kinetics of two syntheses of concave gold nanocubes with a mean size of 72 and 108 nm followed by the optical coherence tomography (OCT) technique by acquiring B-scan images each 5 s. In addition, ultra violet-visible (UV-Vis) spectra and mean size from dynamic light scattering (DLS) were acquired during nanoparticle growth to generate kinetic plots in order to corroborate the OCT results. Kinetic plots from OCT images were obtained by plotting contrast enhancement of B-scan images as function of time. Fitting parameters values given by using the classical Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation show that the growth rate parameter k is higher for small cubes than for large ones, and that the Avrami exponent n associated to the growth kinetics of concave nanocubes is close to 2 for both syntheses. The results of UV-Vis spectroscopy and DLS confirm that OCT is a viable technique to provide information about nanoparticle growth kinetics. Moreover, to our knowledge, this is the first time that OCT technique is used to follow nanoparticle growth kinetics.

     

Study of the Morphological and Functional State of Higher Plant Tissues by Optical Coherence Microscopy and Optical Coherence Tomography

Comparative analysis of two optical methods—optical coherence tomography (OCT) and optical coherence microscopy (OCM)—was made for vital visualization of plant tissues in tomato (Lycopersicon esculentum Mill), spiderwort (Tradescantia pallida (Rose) D. Hunt), orach (Atriplex sp.), and leaves and seeds of medium starwort (Stellaria media L.). The obtained OCT- and OCM-images allowed the morphological and functional state of plant tissues to be assessed in vivo. A higher spatial resolution of the OCM method, as compared to OCT method, allowed plant morphological structures to be identified with greater confidence. The morphological and functional state of tissues can be monitored with a time resolution of 1–4 s in intact plants, without removing them from the habitat.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 628–634.Original Russian Text Copyright © 2005 by Kutis, Sapozhnikova, Kuranov, Kamenskii.     

Thinned-skull Cortical Window Technique for In Vivo Optical Coherence Tomography Imaging

Optical coherence tomography (OCT) is a biomedical imaging technique with high spatial-temporal resolution. With its minimally invasive approach OCT has been used extensively in ophthalmology, dermatology, and gastroenterology^1-3. Using a thinned-skull cortical window (TSCW), we employ spectral-domain OCT (SD-OCT) modality as a tool to image the cortex in vivo. Commonly, an opened-skull has been used for neuro-imaging as it provides more versatility, however, a TSCW approach is less invasive and is an effective mean for long term imaging in neuropathology studies. Here, we present a method of creating a TSCW in a mouse model for in vivo OCT imaging of the cerebral cortex.     

光学相干层析成像技术用于裸鼠皮肤霉菌感染研究

利用中心波长为850 nm的宽带光源SLD实现了纵向分辨率为8μm的光学相干层析成像系统。系统采用傅里叶域光学延迟线实现了深度扫描速度为160 mm/s,成像深度为3 mm。获得了裸鼠皮肤霉菌感染部位和健康皮肤的光学相干层析(optical coherence tom ography,OCT)图像,皮肤病变前后的内部结构信息清晰可见。     

传统光学相干断层成像:软骨双折射特性的研究

传统光学相干断层成像可实现无损伤在体检测,具有较高的分辨率和灵敏度。获取生物组织的双折射信息可望是其应用之一。本文用传统光学相干断层成像系统以动物模型对关节软骨进行了研究,对软骨组织的传统光学相干断层图像的层结构随脱水和机械作用的变化进行了分析。结果表明,传统光学相干断层成像系统在一定程度上可用于监测由其胶原质纤维排列决定的软骨组织的双折射和密度。     

基于谱域光学相干层析系统中光谱涨落的指纹获取

指纹因其特异性和稳定性等特点而被称为"证据之首",在案件侦破中起着极其重要的作用。多种物理学、化学和光学技术都可以用于获取现场遗留的指纹,然而这些方法存在一些缺点,如会对指纹造成破坏、潜在的毒副作用、在现场留有痕迹等。利用谱域光学相干层析(spectral domain optical coherence tomography,简记为SD-OCT)技术进行指纹探测具有非接触、对指纹无损伤和高灵敏度的优势,利用OCT系统的相位敏感性我们可以在低对比条件下再现遗留在物体表面的指纹,但处理结果受指纹所在表面高低起伏影响,使得指纹信息对比度降低,难以被分离和提取。本文提出了一种基于干涉光谱涨落的指纹获取方法,只需对OCT系统得到的干涉光谱的涨落进行处理分析,即可得到遗留在物体表面的指纹图案,不需进行相位和表面轮廓高度的求取,算法简单、处理速度快,处理结果不受样品表面高低起伏的影响。实验结果表明,在起伏表面上,使用该方法也能较好地显现遗留在物体表面的指纹图案。     

光学相干层析术高分辨率活体成像泼尼松龙诱导的骨质疏松斑马鱼模型

本研究利用光学相干层析术OCT对泼尼松龙诱导的斑马鱼骨质疏松模型进行活体成像,并结合电镜能谱技术定量分析斑马鱼模型骨质的钙磷元素含量及分布情况,共同探讨OCT方法在基于斑马鱼模型开展的骨质疏松研究中的使用价值。选取40条3月龄野生型斑马鱼暴露于50μmol/L泼尼松龙溶液和含0. 5%DMSO的溶液中(对照组),28. 5℃下培养,分别于第5、10、20天取出浸药组和对照组进行OCT活体成像,比较两者光散射特征。在每个时间点的成像之后,将浸药组的5条斑马鱼处死,然后取颅骨进行元素含量电镜扫描能谱分析。本研究利用50μmol/L泼尼松龙溶液培养斑马鱼至第20天,成功构建了斑马鱼骨质疏松模型。与对照组相比,模型组活体OCT成像显示骨组织光散射减弱,光子量明显减少,呈不均匀分布。能谱元素检查结果说明颅骨内所含钙、磷比例明显下降,证实骨质疏松发生,骨量减少。OCT成像方法在对斑马鱼骨质疏松模型进行活体、实时、无创等研究方面具有重要价值,本试验也为骨质疏松疾病的研究和药物筛选等方面提供了新的有效的方法。