Showing papers on "Optical coherence tomography published in 2016"
TL;DR: Although clinical manifestations of pachychoroid spectrum disorders vary considerably, these entities share morphologic findings in the choroid, including increased thickness and dilated outer choroidal vessels, which localizes these changes to disease foci and shows additional findings that may unify the understanding of disease pathogenesis.
Abstract: Purpose:To correlate clinical manifestations with choroidal morphology in pachychoroid disorders, including central serous chorioretinopathy, pachychoroid pigment epitheliopathy, pachychoroid neovasculopathy, and polypoidal choroidal vasculopathy, using en face swept-source optical coherence tomogra
321 citations
TL;DR: It is demonstrated that PR OCT-A cleanly removes flow projection from the normally avascular outer retinal slab while preserving the density and continuity of the intermediate and deep retinal capillary plexuses.
Abstract: Shadowgraphic projection artifacts from superficial vasculature interfere with the visualization of deeper vascular networks in optical coherence tomography angiography (OCT-A). We developed a novel algorithm to remove this artifact by resolving the ambiguity between in situ and projected flow signals. The algorithm identifies voxels with in situ flow as those where intensity-normalized decorrelation values are higher than all shallower voxels in the same axial scan line. This “projection-resolved” (PR) algorithm effectively suppressed the projection artifact on both en face and cross-sectional angiograms and enhanced depth resolution of vascular networks. In the human macula, the enhanced angiograms show three distinct vascular plexuses in the inner retina and no vessels in the outer retina. We demonstrate that PR OCT-A cleanly removes flow projection from the normally avascular outer retinal slab while preserving the density and continuity of the intermediate and deep retinal capillary plexuses.
274 citations
TL;DR: The substantial reduction of light scattering multiplicity at tissue optical clearing that leads to a lesser influence of scattering on the measured intrinsic polarization properties of the tissue and allows for more precise quantification of these properties is demonstrated.
Abstract: This tutorial-review introduces the fundamentals of polarized light interaction with biological tissues and presents some of the recent key polarization optical methods that have made possible the quantitative studies essential for biomedical diagnostics. Tissue structures and the corresponding models showing linear and circular birefringence, dichroism, and chirality are analyzed. As the basis for a quantitative description of the interaction of polarized light with tissues, the theory of polarization transfer in a random medium is used. This theory employs the modified transfer equation for Stokes parameters to predict the polarization properties of single- and multiple-scattered optical fields. The near-order of scatterers in tissues is accounted for to provide an adequate description of tissue polarization properties. Biomedical diagnostic techniques based on polarized light detection, including polarization imaging and spectroscopy, amplitude and intensity light scattering matrix measurements, and polarization-sensitive optical coherence tomography are described. Examples of biomedical applications of these techniques for early diagnostics of cataracts, detection of precancer, and prediction of skin disease are presented. The substantial reduction of light scattering multiplicity at tissue optical clearing that leads to a lesser influence of scattering on the measured intrinsic polarization properties of the tissue and allows for more precise quantification of these properties is demonstrated.
231 citations
TL;DR: A five-index quantitative analysis of OCT angiograms in an attempt to detect and assess vascular abnormalities from multiple perspectives and demonstrates the usefulness of the proposed indices with five illustrative cases.
Abstract: Optical coherence tomography angiography (OCTA) is clinically useful for the qualitative assessment of the macular microvasculature However, there is a need for comprehensive quantitative tools to help objectively analyze the OCT angiograms Few studies have reported the use of a single quantitative index to describe vessel density in OCT angiograms In this study, we introduce a five-index quantitative analysis of OCT angiograms in an attempt to detect and assess vascular abnormalities from multiple perspectives The indices include vessel area density, vessel skeleton density, vessel diameter index, vessel perimeter index, and vessel complexity index We show the usefulness of the proposed indices with five illustrative cases Repeatability is tested on both a healthy case and a stable diseased case, giving interclass coefficients smaller than 0031 The results demonstrate that our proposed quantitative analysis may be useful as a complement to conventional OCTA for the diagnosis of disease and monitoring of treatment
210 citations
20 Aug 2016
TL;DR: Unlike competing methods, this technique quantitatively measures the volumetric refractive index of primarily transparent and contiguous sample features without the need for interferometry or any moving parts.
Abstract: This paper presents a technique to image the complex index of refraction of a sample across three dimensions. The only required hardware is a standard microscope and an array of LEDs. The method, termed Fourier ptychographic tomography (FPT), first captures a sequence of intensity-only images of a sample under angularly varying illumination. Then, using principles from ptychography and diffraction tomography, it computationally solves for the sample structure in three dimensions. The experimental microscope demonstrates a lateral spatial resolution of 0.39 μm and an axial resolution of 3.7 μm at the Nyquist–Shannon sampling limit (0.54 and 5.0 μm at the Sparrow limit, respectively) across a total imaging depth of 110 μm. Unlike competing methods, this technique quantitatively measures the volumetric refractive index of primarily transparent and contiguous sample features without the need for interferometry or any moving parts. Wide field-of-view reconstructions of thick biological specimens suggest potential applications in pathology and developmental biology.
202 citations
TL;DR: OCT angiographic imaging on the CIRRUS™ HD-OCT platform was made possible by increasing the scanning rate to 68,000 A-scans per second and introducing improved tracking software known as FastTrac™ retinal-tracking technology.
Abstract: ZEISS Angioplex™ optical coherence tomography (OCT) angiography generates high-resolution three-dimensional maps of the retinal and choroidal microvasculature while retaining all of the capabilities of the existing CIRRUS™ HD-OCT Model 5000 instrument. Angioplex™ OCT angiographic imaging on the CIRRUS™ HD-OCT platform was made possible by increasing the scanning rate to 68,000 A-scans per second and introducing improved tracking software known as FastTrac™ retinal-tracking technology. The generation of en face microvascular flow images with Angioplex™ OCT uses an algorithm known as OCT microangiography-complex, which incorporates differences in both the phase and intensity information contained within sequential B-scans performed at the same position. Current scanning patterns for en face angiographic visualization include a 3 × 3 and a 6 × 6 mm scan pattern on the retina. A volumetric dataset showing erythrocyte flow information can then be displayed as a color-coded retinal depth map in which the microvasculature of the superficial, deep, and avascular layers of the retina are displayed together with the colors red, representing the superficial microvasculature; green, representing the deep retinal vasculature; and blue, representing any vessels present in the normally avascular outer retina. Each retinal layer can be viewed separately, and the microvascular layers representing the choriocapillaris and the remaining choroid can be viewed separately as well. In addition, readjusting the contours of the slabs to target different layers of interest can generate custom en face flow images. Moreover, each en face flow image is accompanied by an en face intensity image to help with the interpretation of the flow results. Current clinical experience with this technology would suggest that OCT angiography should replace fluorescein angiography for retinovascular diseases involving any area of the retina that can be currently scanned with the CIRRUS™ HD-OCT instrument and may replace fluorescein angiography and indocyanine green angiography for some choroidal vascular diseases.
192 citations
TL;DR: In patients with non–ST-segment elevation acute coronary syndromes, OCT-guided PCI is associated with higher postprocedure fractional flow reserve than PCI guided by angiography alone and did not increase periprocedural complications, type 4a myocardial infarction, or acute kidney injury.
Abstract: Background:No randomized study has investigated the value of optical coherence tomography (OCT) in optimizing the results of percutaneous coronary intervention (PCI) for non–ST-segment elevation ac...
190 citations
TL;DR: By combining a matrix discrimination of ballistic waves and iterative time reversal, this work shows an extension of the imaging-depth limit by at least a factor of 2 compared to optical coherence tomography.
Abstract: Multiple scattering of waves in disordered media is a nightmare whether it is for detection or imaging purposes. So far, the best approach to get rid of multiple scattering is optical coherence tomography. This basically combines confocal microscopy and coherence time gating to discriminate ballistic photons from a predominant multiple scattering background. Nevertheless, the imaging-depth range remains limited to 1 mm at best in human soft tissues because of aberrations and multiple scattering. We propose a matrix approach of optical imaging to push back this fundamental limit. By combining a matrix discrimination of ballistic waves and iterative time reversal, we show, both theoretically and experimentally, an extension of the imaging-depth limit by at least a factor of 2 compared to optical coherence tomography. In particular, the reported experiment demonstrates imaging through a strongly scattering layer from which only 1 reflected photon out of 1000 billion is ballistic. This approach opens a new route toward ultra-deep tissue imaging.
164 citations
TL;DR: The noninvasive detection of optical path length changes shows neuronal photoreceptor activity of single cones in living human retina, and therefore, it may provide diagnostic options in ophthalmology and neurology and could provide insights into visual phototransduction in humans.
Abstract: Noninvasive functional imaging of molecular and cellular processes of vision may have immense impact on research and clinical diagnostics Although suitable intrinsic optical signals (IOSs) have been observed ex vivo and in immobilized animals in vivo, detecting IOSs of photoreceptor activity in living humans was cumbersome and time consuming Here, we observed clear spatially and temporally resolved changes in the optical path length of the photoreceptor outer segment as a response to an optical stimulus in the living human eye To witness these changes, we evaluated phase data obtained with a parallelized and computationally aberration-corrected optical coherence tomography system The noninvasive detection of optical path length changes shows neuronal photoreceptor activity of single cones in living human retina, and therefore, it may provide diagnostic options in ophthalmology and neurology and could provide insights into visual phototransduction in humans
163 citations
TL;DR: Dynamic OCT (D-OCT) based on speckle variance OCT is of special interest as it allows the in vivo evaluation of blood vessels and their distribution within specific lesions, providing additional functional information and consequently greater density of data.
Abstract: Optical coherence tomography (OCT) represents a non-invasive imaging technology, which may be applied to the diagnosis of non-melanoma skin cancer and which has recently been shown to improve the diagnostic accuracy of basal cell carcinoma. Technical developments of OCT continue to expand the applicability of OCT for different neoplastic and inflammatory skin diseases. Of these, dynamic OCT (D-OCT) based on speckle variance OCT is of special interest as it allows the in vivo evaluation of blood vessels and their distribution within specific lesions, providing additional functional information and consequently greater density of data. In an effort to assess the potential of D-OCT for future scientific and clinical studies, we have therefore reviewed the literature and preliminary unpublished data on the visualization of the microvasculature using D-OCT. Information on D-OCT in skin cancers including melanoma, as well as in a variety of other skin diseases, is presented in an atlas. Possible diagnostic features are suggested, although these require additional validation.
160 citations
TL;DR: The findings show that NIRAF is associated with a high-risk morphological plaque phenotype, and suggests that this endogenous imaging biomarker may provide complementary information to that obtained by structural imaging alone.
Abstract: Objectives The authors present the clinical imaging of human coronary arteries in vivo using a multimodality optical coherence tomography (OCT) and near-infrared autofluorescence (NIRAF) intravascular imaging system and catheter. Background Although intravascular OCT is capable of providing microstructural images of coronary atherosclerotic lesions, it is limited in its capability to ascertain the compositional/molecular features of plaque. A recent study in cadaver coronary plaque showed that endogenous NIRAF is elevated in necrotic core lesions. The combination of these 2 technologies in 1 device may therefore provide synergistic data to aid in the diagnosis of coronary pathology in vivo. Methods We developed a dual-modality intravascular imaging system and 2.6-F catheter that can simultaneously acquire OCT and NIRAF data from the same location on the artery wall. This technology was used to obtain volumetric OCT-NIRAF images from 12 patients with coronary artery disease undergoing percutaneous coronary intervention. Images were acquired during a brief, nonocclusive 3- to 4-ml/s contrast purge at a speed of 100 frames/s and a pullback rate of 20 or 40 mm/s. OCT-NIRAF data were analyzed to determine the distribution of the NIRAF signal with respect to OCT-delineated plaque morphological features. Results High-quality intracoronary OCT and NIRAF image data (>50-mm pullback length) were successfully acquired without complication in all patients (17 coronary arteries). The maximum NIRAF signal intensity of each plaque was compared with OCT-defined type, showing a statistically significant difference between plaque types (1-way analysis of variance, p Conclusions This OCT-NIRAF study demonstrates that dual-modality microstructural and fluorescence intracoronary imaging can be safely and effectively conducted in human patients. Our findings show that NIRAF is associated with a high-risk morphological plaque phenotype. The focal distribution of NIRAF in these lesions furthermore suggests that this endogenous imaging biomarker may provide complementary information to that obtained by structural imaging alone.
TL;DR: Reviewing work done over the last 15 years to combine the microscopic transverse resolution of AO with the microscopic axial resolution of OCT, building AO-OCT systems with the highest three-dimensional resolution of any existing retinal imaging modality.
Abstract: Special Issue A Review of Adaptive Optics Optical Coherence Tomography: Technical Advances, Scientific Applications, and the Future Ravi S. Jonnal, 1 Omer P. Kocaoglu, 2 Robert J. Zawadzki, 1 Zhuolin Liu, 2 Donald T. Miller, 2 and John S. Werner 1 1 Vision Science and Advanced Retinal Imaging Laboratory, University of California-Davis, Sacramento, California, United States School of Optometry, Indiana University, Bloomington, Indiana, United States Correspondence: Ravi S. Jonnal, 4860 Y Street, Suite 2400, Sacra- mento, CA 95817, USA; rsjonnal@ucdavis.edu. Submitted: January 8, 2016 Accepted: May 29, 2016 Citation: Jonnal RS, Kocaoglu OP, Zawadzki RJ, Liu Z, Miller DT, Werner JS. A review of adaptive optics optical coherence tomography: technical ad- vances, scientific applications, and the future. Invest Ophthalmol Vis Sci. 2016;57:OCT51–OCT68. DOI:10.1167/iovs.16-19103 P URPOSE . Optical coherence tomography (OCT) has enabled ‘‘virtual biopsy’’ of the living human retina, revolutionizing both basic retina research and clinical practice over the past 25 years. For most of those years, in parallel, adaptive optics (AO) has been used to improve the transverse resolution of ophthalmoscopes to foster in vivo study of the retina at the microscopic level. Here, we review work done over the last 15 years to combine the microscopic transverse resolution of AO with the microscopic axial resolution of OCT, building AO-OCT systems with the highest three-dimensional resolution of any existing retinal imaging modality. M ETHODS . We surveyed the literature to identify the most influential antecedent work, important milestones in the development of AO-OCT technology, its applications that have yielded new knowledge, research areas into which it may productively expand, and nascent applications that have the potential to grow. R ESULTS . Initial efforts focused on demonstrating three-dimensional resolution. Since then, many improvements have been made in resolution and speed, as well as other enhancements of acquisition and postprocessing techniques. Progress on these fronts has produced numerous discoveries about the anatomy, function, and optical properties of the retina. C ONCLUSIONS . Adaptive optics OCT continues to evolve technically and to contribute to our basic and clinical knowledge of the retina. Due to its capacity to reveal cellular and microscopic detail invisible to clinical OCT systems, it is an ideal companion to those instruments and has the demonstrable potential to produce images that can guide the interpretation of clinical findings. Keywords: adaptive optics, optical coherence tomography, retinal imaging T he 25 years since the advent of optical coherence tomography (OCT) 1 have brought countless improvements in its axial resolution, speed, and sensitivity. The main effort to improve OCT’s transverse (or lateral) resolution has been to combine it with adaptive optics (AO), a union that has been investigated in just a few labs. Nevertheless, AO-OCT now plays important roles in the production of knowledge about the retina and its diseases. Chief among these is its potential to resolve ambiguities present in clinical and research-grade conventional (non-AO) OCT systems. Because AO-OCT reveals the microstructure that makes up clinically observable features, it is indispensable as a scientific companion to conventional OCT. Understanding the differences between the OCT image and the AO-OCT image requires that we describe some of the technical details of AO-OCT imaging and image processing, and how these are motivated by the fundamental biological and physical properties of the living human retina. the retina’s laminar structure. Because retinal diseases often impact this laminar structure, OCT has been used extensively to detect and assess disease and monitor therapeutic efficacy, to such an extent that it has become a standard of ophthalmic care. Each retinal layer contains structural and functional subunits such as cells, organelles, and capillaries, most of which are too small to be resolved by conventional OCT systems such as the commercial systems employed in the clinic (Fig. 1). While cellular imaging is presently of limited interest to clinicians, it is of great interest to basic science researchers, who stand to learn much about these structures and their functions by imaging them in situ. Moreover, an understanding of the gross structural changes observed in clinical OCT images of disease and recovery depends crucially on knowing their microscopic constituents. Cellular imaging of the retina will continue to expand our understanding of retinal disease, and is therefore of great translational significance. The Spatial Scale of Retinal Features Optical Factors Affecting Transverse Resolution The human retina consists of approximately a dozen layers of mostly transparent tissue, together less than half a millimeter thick. The axial resolution afforded by OCT lends itself to imaging The point-spread function (PSF) is a measure of the quality of an imaging system, describing how light originating from a point in tissue manifests in the image of that tissue. The PSF has both iovs.arvojournals.org j ISSN: 1552-5783 This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/Journals/IOVS/935468/ on 11/08/2016 OCT51
TL;DR: A new endogenous approach to reveal subcellular metabolic contrast in fresh ex vivo tissues taking advantage of the time dependence of the full field optical coherence tomography interferometric signals to identify different dynamics at the millisecond scale on a wide range of organs in normal or pathological conditions.
Abstract: We developed a new endogenous approach to reveal subcellular metabolic contrast in fresh ex vivo tissues taking advantage of the time dependence of the full field optical coherence tomography interferometric signals. This method reveals signals linked with local activity of the endogenous scattering elements which can reveal cells where other OCT-based techniques fail or need exogenous contrast agents. We benefit from the micrometric transverse resolution of full field OCT to image intracellular features. We used this time dependence to identify different dynamics at the millisecond scale on a wide range of organs in normal or pathological conditions.
TL;DR: It is demonstrated that implementation of intensity-based OCT imaging and OCT angiography methods allows for visualization of retinal and choroidal vascular layers known from anatomic studies in retinal preparations.
Abstract: We compared the performance of three OCT angiography (OCTA) methods: speckle variance, amplitude decorrelation and phase variance for imaging of the human retina and choroid. Two averaging methods, split spectrum and volume averaging, were compared to assess the quality of the OCTA vascular images. All data were acquired using a swept-source OCT system at 1040 nm central wavelength, operating at 100,000 A-scans/s. We performed a quantitative comparison using a contrast-to-noise (CNR) metric to assess the capability of the three methods to visualize the choriocapillaris layer. For evaluation of the static tissue noise suppression in OCTA images we proposed to calculate CNR between the photoreceptor/RPE complex and the choriocapillaris layer. Finally, we demonstrated that implementation of intensity-based OCT imaging and OCT angiography methods allows for visualization of retinal and choroidal vascular layers known from anatomic studies in retinal preparations. OCT projection imaging of data flattened to selected retinal layers was implemented to visualize retinal and choroidal vasculature. User guided vessel tracing was applied to segment the retinal vasculature. The results were visualized in a form of a skeletonized 3D model.
TL;DR: Optovue AngioVue system technology allows quantitative analysis and provides numerical data about flow area and non-flow area and can also generate a flow density map, which may serve as biomarkers in diagnosis and for tracking disease progression or treatment response.
Abstract: Optovue AngioVue system technology for optical coherence tomography (OCT) angiography is based on the AngioVue Imaging System (Optovue, Inc., Freemont, CA), using split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. This algorithm was developed to minimize scanning time. It detects motion in blood vessel lumen by measuring the variation in reflected OCT signal amplitude between consecutive cross-sectional scans. The novelty of SSADA lies in how the OCT signal is processed to enhance flow detection and reject axial bulk motion noise. Specifically, the algorithm splits the OCT image into different spectral bands, thus increasing the number of usable image frames. Each new frame has a lower axial resolution that is less susceptible to axial eye motion caused by blood pulsation. Optovue AngioVue system technology allows quantitative analysis. It provides numerical data about flow area and non-flow area. It can also generate a flow density map. These metrics may serve as biomarkers in diagnosis and for tracking disease progression or treatment response. Flow area: the software will calculate the drawn area and vessel area in mm(2). It allows for comparison of all measurements for a given participant. Non-flow area: the software shows the non-perfused areas by mouse click selection. Ischemic areas will be shown in yellow. These areas may be saved and matched with others in the study. Flow density tool is able to measure the percentage of vascular areas on en face angiograms. This analysis is based on an ETDRS grid centered on the macula as with the thickness map. This tool works both on inner and outer vascular plexus.
TL;DR: This chapter describes the implementation of OCTARA with swept-source OCT technology, the technical specifications of acquisition, the algorithm's function and principles for analysis of B-scan data to achieve angiographic visualization, and examples of OCTA scans performed using the OCTARA algorithm.
Abstract: Optical coherence tomography (OCT) angiography (OCTA) is a novel, noninvasive, three-dimensional imaging technique that allows for the visualization of intravascular flow in the microvasculature. Swept-source OCT technology utilizes longer-wavelength infrared light than conventional spectral-domain OCT. This enables improved penetration into tissue and imaging through optical opacities and is invisible to the subject. Topcon has recently developed an innovative OCTA algorithm, OCTARA (OCTA Ratio Analysis), which benefits from being paired with swept-source OCT. OCTARA aims to provide improved detection sensitivity of low blood flow and reduced motion artifacts without compromising axial resolution. In this chapter, we describe the implementation of OCTARA with swept-source OCT technology, the technical specifications of acquisition (e.g. the number of scans, area of examination field, etc.) along with the algorithm's function and principles for analysis of B-scan data to achieve angiographic visualization. Examples of OCTA scans performed using the OCTARA algorithm and a comparison of these scans with images obtained using other technologies are also presented.
TL;DR: An algorithm to detect AA in OCTA separated into three individual plexuses using a projection-resolved algorithm accurately distinguishes mild NPDR from control eyes and is highly repeatable.
Abstract: Purpose
The purpose of this study was to evaluate an automated algorithm for detecting avascular area (AA) in optical coherence tomography angiograms (OCTAs) separated into three individual plexuses using a projection-resolved technique.
TL;DR: A computer-aided diagnosis (CAD) model to discriminate age-related macular degeneration, diabetic macular edema and healthy macula is proposed and the best model based on the sequential minimal optimization (SMO) algorithm achieved 99.3% in the overall accuracy.
Abstract: Non-lethal macular diseases greatly impact patients’ life quality, and will cause vision loss at the late stages. Visual inspection of the optical coherence tomography (OCT) images by the experienced clinicians is the main diagnosis technique. We proposed a computer-aided diagnosis (CAD) model to discriminate age-related macular degeneration (AMD), diabetic macular edema (DME) and healthy macula. The linear configuration pattern (LCP) based features of the OCT images were screened by the Correlation-based Feature Subset (CFS) selection algorithm. And the best model based on the sequential minimal optimization (SMO) algorithm achieved 99.3% in the overall accuracy for the three classes of samples.
TL;DR: In this paper, the authors performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts.
Abstract: Identifying tumour margins during breast-conserving surgeries is a persistent challenge. We have previously developed miniature needle probes that could enable intraoperative volume imaging with optical coherence tomography. In many situations, however, scattering contrast alone is insufficient to clearly identify and delineate malignant regions. Additional polarization-sensitive measurements provide the means to assess birefringence, which is elevated in oriented collagen fibres and may offer an intrinsic biomarker to differentiate tumour from benign tissue. Here, we performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts. First ex vivo imaging of breast tumour samples revealed excellent contrast between lowly birefringent malignant regions, and stromal tissue, which is rich in oriented collagen and exhibits higher birefringence, as confirmed with co-located histology. The ability to clearly differentiate between tumour and uninvolved stroma based on intrinsic contrast could prove decisive for the intraoperative assessment of tumour margins.
TL;DR: Vascular changes at the optic disc as measured by optical microangiography based optical coherence tomography (OCT) angiography technique may provide useful information for diagnosis and monitoring of glaucoma.
Abstract: Purpose
To investigate optic disc perfusion differences in normal, primary open-angle glaucoma (POAG), and normal tension glaucoma (NTG) eyes using optical microangiography (OMAG) based optical coherence tomography (OCT) angiography technique.
20 Dec 2016
TL;DR: 3D OCT over cubic meter volumes is reported using a long coherence length, 1310 nm vertical-cavity surface-emitting laser and silicon photonic integrated circuit dual-quadrature receiver technology combined with enhanced signal processing.
Abstract: Optical coherence tomography (OCT) is a powerful three-dimensional (3D) imaging modality with micrometer-scale axial resolution and up to multi-GigaVoxel/s imaging speed. However, the imaging range of high-speed OCT has been limited. Here, we report 3D OCT over cubic meter volumes using a long coherence length, 1310 nm vertical-cavity surface-emitting laser and silicon photonic integrated circuit dual-quadrature receiver technology combined with enhanced signal processing. We achieved 15 µm depth resolution for tomographic imaging at a 100 kHz axial scan rate over a 1.5 m range. We show 3D macroscopic imaging examples of a human mannequin, bicycle, machine shop gauge blocks, and a human skull/brain model. High-bandwidth, meter-range OCT demonstrates new capabilities that promise to enable a wide range of biomedical, scientific, industrial, and research applications.
TL;DR: OCTA with motion tracking through an auxiliary real-time line scan ophthalmoscope is reported that is clinically feasible to image functional retinal vasculature in patients, with a coverage of more than 60 degrees of retina while still maintaining high definition and resolution.
Abstract: Optical coherence tomography angiography (OCTA) allows for the evaluation of functional retinal vascular networks without a need for contrast dyes. For sophisticated monitoring and diagnosis of retinal diseases, OCTA capable of providing wide-field and high definition images of retinal vasculature in a single image is desirable. We report OCTA with motion tracking through an auxiliary real-time line scan ophthalmoscope that is clinically feasible to image functional retinal vasculature in patients, with a coverage of more than 60 degrees of retina while still maintaining high definition and resolution. We demonstrate six illustrative cases with unprecedented details of vascular involvement in retinal diseases. In each case, OCTA yields images of the normal and diseased microvasculature at all levels of the retina, with higher resolution than observed with fluorescein angiography. Wide-field OCTA technology will be an important next step in augmenting the utility of OCT technology in clinical practice.
TL;DR: The extent to which the 24-2 visual field (VF) misses macular damage confirmed with both 10-2 VF and optical coherence tomography (OCT) tests was determined and the patterns of damage missed were evaluated.
Abstract: Purpose
To determine the extent to which the 24-2 visual field (VF) misses macular damage confirmed with both 10-2 VF and optical coherence tomography (OCT) tests and to evaluate the patterns of damage missed.
TL;DR: An algorithm that recognizes five different types of motion artifacts and used it to evaluate the performance of three motion removal technologies demonstrated higher performance than tracking or MCT alone in healthy and diabetic eyes.
Abstract: Artifacts introduced by eye motion in optical coherence tomography angiography (OCTA) affect the interpretation of images and the quantification of parameters with clinical value. Eradication of such artifacts in OCTA remains a technical challenge. We developed an algorithm that recognizes five different types of motion artifacts and used it to evaluate the performance of three motion removal technologies. On en face maximum projection of flow images, the summed flow signal in each row and column and the correlation between neighboring rows and columns were calculated. Bright line artifacts were recognized by large summed flow signal. Drifts, distorted lines, and stretch artifacts exhibited abnormal correlation values. Residual lines were simultaneously a local maximum of summed flow and a local minimum of correlation. Tracking-assisted scanning integrated with motion correction technology (MCT) demonstrated higher performance than tracking or MCT alone in healthy and diabetic eyes.
TL;DR: By combining multimodal imaging, the authors propose that multiple evanescent white dot syndrome is primarily the result of inflammation at the outer photoreceptor level leading to a "photoreceptoritis" and causing loss of the inner and outer segments.
Abstract: Purpose:To localize the various levels of abnormalities in multiple evanescent white dot syndrome by comparing “en face” optical coherence tomography (OCT) and OCT angiography with various conventional imaging modalities.Methods:In this retrospective case series, multimodal imaging was performed in
TL;DR: A fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping is presented, called acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force.
Abstract: Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force. Combining it with high-speed, four-dimensional (three space dimensions plus time) phase-sensitive optical coherence tomography creates a non-contact tool for high-resolution and quantitative dynamic elastography of soft tissue at near real-time imaging rates. The overall approach is demonstrated in ex-vivo porcine cornea.
TL;DR: The method was found useful, in a small case series, for visualizing blood flow speeds in a variety of ocular diseases and serves as a step toward quantitative optical coherence tomography angiography.
Abstract: PURPOSE Currently available optical coherence tomography angiography systems provide information about blood flux but only limited information about blood flow speed. The authors develop a method for mapping the previously proposed variable interscan time analysis (VISTA) algorithm into a color display that encodes relative blood flow speed. METHODS Optical coherence tomography angiography was performed with a 1,050 nm, 400 kHz A-scan rate, swept source optical coherence tomography system using a 5 repeated B-scan protocol. Variable interscan time analysis was used to compute the optical coherence tomography angiography signal from B-scan pairs having 1.5 millisecond and 3.0 milliseconds interscan times. The resulting VISTA data were then mapped to a color space for display. RESULTS The authors evaluated the VISTA visualization algorithm in normal eyes (n = 2), nonproliferative diabetic retinopathy eyes (n = 6), proliferative diabetic retinopathy eyes (n = 3), geographic atrophy eyes (n = 4), and exudative age-related macular degeneration eyes (n = 2). All eyes showed blood flow speed variations, and all eyes with pathology showed abnormal blood flow speeds compared with controls. CONCLUSION The authors developed a novel method for mapping VISTA into a color display, allowing visualization of relative blood flow speeds. The method was found useful, in a small case series, for visualizing blood flow speeds in a variety of ocular diseases and serves as a step toward quantitative optical coherence tomography angiography.
TL;DR: A surgical imaging system employing four-dimensional microscope-integrated optical coherence tomography capable of imaging at up to 10 volumes per second to visualize human microsurgery and achieves surgeon-interactive 4D visualization of live surgery which could expand the surgeon’s capabilities is introduced.
Abstract: Minimally-invasive microsurgery has resulted in improved outcomes for patients. However, operating through a microscope limits depth perception and fixes the visual perspective, which result in a steep learning curve to achieve microsurgical proficiency. We introduce a surgical imaging system employing four-dimensional (live volumetric imaging through time) microscope-integrated optical coherence tomography (4D MIOCT) capable of imaging at up to 10 volumes per second to visualize human microsurgery. A custom stereoscopic heads-up display provides real-time interactive volumetric feedback to the surgeon. We report that 4D MIOCT enhanced suturing accuracy and control of instrument positioning in mock surgical trials involving 17 ophthalmic surgeons. Additionally, 4D MIOCT imaging was performed in 48 human eye surgeries and was demonstrated to successfully visualize the pathology of interest in concordance with preoperative diagnosis in 93% of retinal surgeries and the surgical site of interest in 100% of anterior segment surgeries. In vivo 4D MIOCT imaging revealed sub-surface pathologic structures and instrument-induced lesions that were invisible through the operating microscope during standard surgical maneuvers. In select cases, 4D MIOCT guidance was necessary to resolve such lesions and prevent post-operative complications. Our novel surgical visualization platform achieves surgeon-interactive 4D visualization of live surgery which could expand the surgeon’s capabilities.
TL;DR: Optical coherence tomography angiography provides high-resolution, noninvasive visualization of the microvasculature of the optic nerve head and peripapillary region and may prove useful in better characterization of optic neuropathies.
Abstract: Purpose:To evaluate the optic nerve head microvasculature in eyes with acute and chronic optic neuropathies using swept-source optical coherence tomography angiography.Methods:In this cross-sectional, observational study, optical coherence tomography angiography images were obtained from the optic n
TL;DR: Multimodal imaging analysis of the retina in patients with multiple evanescent white dot syndrome shows additional features that may help in the diagnosis of the disease and in further understanding its etiology.
Abstract: PURPOSE:
To evaluate and characterize multiple evanescent white dot syndrome abnormalities with modern multimodal imaging modalities.
METHODS:
This retrospective cohort study evaluated fundus photography, fluorescein angiography, indocyanine green angiography, optical coherence tomography, enhanced depth imaging optical coherence tomography, short-wavelength autofluorescence, and near-infrared autofluorescence.
RESULTS:
Thirty-four multiple evanescent white dot syndrome patients with mean age of 28.7 years were studied (range, 14-49 years). Twenty-six patients were women, and eight were men. Initial mean visual acuity was 0.41 logMAR. Final mean visual acuity was 0.03 logMAR. Fluorescein angiography shows a variable number of mid retinal early fluorescent dots distributed in a wreathlike pattern, which correlate to fundus photography, fundus autofluorescence, and indocyanine green angiography. Indocyanine green angiography imaging shows the dots and also hypofluorescent, deeper, and larger spots, which are occasionally confluent, demonstrating a large plaque of deep retinal hypofluorescence. Optical coherence tomography imaging shows multifocal debris centered at and around the ellipsoid layer, corresponding to the location of spots seen with photography, indocyanine green angiography, and fluorescein angiography. Protrusions of the hyperreflectant material from the ellipsoid layer toward the outer nuclear layer correspond to the location of dots seen with photography, indocyanine green angiography, and fluorescein angiography.
CONCLUSION:
Multimodal imaging analysis of the retina in patients with multiple evanescent white dot syndrome shows additional features that may help in the diagnosis of the disease and in further understanding its etiology. Multiple evanescent white dot syndrome is predominantly a disease of the outer retina, centered at the ellipsoid zone, but also involving the interdigitation zone and the outer nuclear layer.