Showing papers on "Optical coherence tomography published in 2009"

Enhanced Depth Imaging Optical Coherence Tomography of the Choroid in Normal Eyes

Abstract: PURPOSE To measure macular choroidal thickness in normal eyes at different points using enhanced depth imaging (EDI) optical coherence tomography (OCT) and to evaluate the association of choroidal thickness and age. DESIGN Retrospective, observational case series. METHODS EDI OCT images were obtained in patients without significant retinal or choroidal pathologic features. The images were obtained by positioning a spectral-domain OCT device close enough to the eye to acquire an inverted image. Seven sections were obtained within a 5 x 30-degree area centered at the fovea, with 100 scans averaged for each section. The choroid was measured from the outer border of the retinal pigment epithelium to the inner scleral border at 500-microm intervals of a horizontal section from 3 mm temporal to the fovea to 3 mm nasal to the fovea. Statistical analysis was performed to evaluate variations of choroidal thickness at each location and to correlate choroidal thickness and patient age. RESULTS The mean age of the 30 patients (54 eyes) was 50.4 years (range, 19 to 85 years), and 14 patients (46.7%) were female. The choroid was thickest underneath the fovea (mean, 287 microm; standard deviation, +/- 76 microm). Choroidal thickness decreased rapidly in the nasal direction and averaged 145 microm (+/- 57 microm) at 3 mm nasal to the fovea. Increasing age was correlated significantly with decreasing choroidal thickness at all points measured. Regression analysis suggested that the subfoveal choroidal thickness decreased by 15.6 microm for each decade of life. CONCLUSIONS Choroidal thickness seems to vary topographically within the posterior pole. The thickness of the choroid showed a negative correlation with age. The decrease in the thickness of the choroid may play a role in the pathophysiologic features of various age-related ocular conditions.

Enhanced depth imaging optical coherence tomography of the choroid in central serous chorioretinopathy.

Abstract: PURPOSE The purpose of the study was to evaluate the choroidal thickness in patients with central serous chorioretinopathy, a disease attributed to increased choroidal vascular hyperpermeability. METHODS Patients with central serous chorioretinopathy underwent enhanced depth imaging spectral-domain optical coherence tomography, which was obtained by positioning a spectral-domain optical coherence tomography device close enough to the eye to acquire an inverted image. Seven sections, each comprising 100 averaged scans, were obtained within a 5 degrees x 30 degrees rectangle to encompass the macula. The subfoveal choroidal thickness was measured from the outer border of the retinal pigment epithelium to the inner scleral border. RESULTS The mean age of subjects undergoing enhanced depth imaging spectral-domain optical coherence tomography was 59.3 years (standard deviation, 15.8 years). Seventeen of 19 patients (89.5%) were men, and 12 (63.2%) patients had bilateral clinical disease. The choroidal thickness measured in 28 eligible eyes of the 19 patients was 505 microm (standard deviation, 124 microm), which was significantly greater than the choroidal thickness in normal eyes (P < or = 0.001). CONCLUSION Enhanced depth imaging spectral-domain optical coherence tomography demonstrated a very thick choroid in patients with central serous chorioretinopathy. This finding provides additional evidence that central serous chorioretinopathy may be caused by increased hydrostatic pressure in the choroid.

Intracoronary Optical Coherence Tomography: A Comprehensive Review: Clinical and Research Applications

Abstract: Cardiovascular optical coherence tomography (OCT) is a catheter-based invasive imaging system. Using light rather than ultrasound, OCT produces high-resolution in vivo images of coronary arteries and deployed stents. This comprehensive review will assist practicing interventional cardiologists in understanding the technical aspects of OCT based upon the physics of light and will also highlight the emerging research and clinical applications of OCT. Semi-automated imaging analyses of OCT systems permit accurate measurements of luminal architecture and provide insights regarding stent apposition, overlap, neointimal thickening, and, in the case of bioabsorbable stents, information regarding the time course of stent dissolution. The advantages and limitations of this new imaging modality will be discussed with emphasis on key physical and technical aspects of intracoronary image acquisition, current applications, definitions, pitfalls, and future directions.

Automated 3-D Intraretinal Layer Segmentation of Macular Spectral-Domain Optical Coherence Tomography Images

Abstract: With the introduction of spectral-domain optical coherence tomography (OCT), much larger image datasets are routinely acquired compared to what was possible using the previous generation of time-domain OCT. Thus, the need for 3-D segmentation methods for processing such data is becoming increasingly important. We report a graph-theoretic segmentation method for the simultaneous segmentation of multiple 3-D surfaces that is guaranteed to be optimal with respect to the cost function and that is directly applicable to the segmentation of 3-D spectral OCT image data. We present two extensions to the general layered graph segmentation method: the ability to incorporate varying feasibility constraints and the ability to incorporate true regional information. Appropriate feasibility constraints and cost functions were learned from a training set of 13 spectral-domain OCT images from 13 subjects. After training, our approach was tested on a test set of 28 images from 14 subjects. An overall mean unsigned border positioning error of 5.69 plusmn 2.41 mum was achieved when segmenting seven surfaces (six layers) and using the average of the manual tracings of two ophthalmologists as the reference standard. This result is very comparable to the measured interobserver variability of 5.71 plusmn 1.98 mum.

Macular thickness measurements in healthy eyes using six different optical coherence tomography instruments.

Abstract: To compare central retinal thickness (CRT) measurements in healthy eyes by different commercially available OCT instruments and to compare the intersession reproducibility of such measurements.

Automated Diagnosis of Glaucoma Using Digital Fundus Images

Abstract: Glaucoma is a disease of the optic nerve caused by the increase in the intraocular pressure of the eye. Glaucoma mainly affects the optic disc by increasing the cup size. It can lead to the blindness if it is not detected and treated in proper time. The detection of glaucoma through Optical Coherence Tomography (OCT) and Heidelberg Retinal Tomography (HRT) is very expensive. This paper presents a novel method for glaucoma detection using digital fundus images. Digital image processing techniques, such as preprocessing, morphological operations and thresholding, are widely used for the automatic detection of optic disc, blood vessels and computation of the features. We have extracted features such as cup to disc (c/d) ratio, ratio of the distance between optic disc center and optic nerve head to diameter of the optic disc, and the ratio of blood vessels area in inferior-superior side to area of blood vessel in the nasal-temporal side. These features are validated by classifying the normal and glaucoma images using neural network classifier. The results presented in this paper indicate that the features are clinically significant in the detection of glaucoma. Our system is able to classify the glaucoma automatically with a sensitivity and specificity of 100% and 80% respectively.

Nanoparticles for photoacoustic imaging

Abstract: Nanoparticles have been designed and applied as contrast enhancers in various optical imaging techniques, such as optical coherence tomography, fluorescence imaging, and optical reflectance microscopy. As an emerging hybrid imaging modality, photoacoustic imaging (PAI) has also benefited from the application of these nanoparticle-based contrast agents. We review this rapidly growing field and describe the applications of nanoparticles in PAI. Particular focus is given to nanoparticles whose absorption mechanism is based on surface plasmon resonance, including gold nanoshells, nanorods, and nanocages. Dye-embedded nanoparticles are also reviewed. Specifically, the design and application of each nanoparticle-based contrast agent in relation to the field of PAI are detailed.

Introduction to Optical Microscopy

Abstract: This fully updated, self-contained textbook covering modern optical microscopy equips students with a solid understanding of the theory underlying a range of advanced techniques. Two new chapters cover pump-probe techniques, and imaging in scattering media, and additional material throughout covers light-sheet microscopy, image scanning microscopy, and much more. An array of practical techniques are discussed, from classical phase contrast and confocal microscopy, to holographic, structured illumination, multi-photon, and coherent Raman microscopy, and optical coherence tomography. Fundamental topics are also covered, including Fourier optics, partial coherence, 3D imaging theory, statistical optics, and the physics of scattering and fluorescence. With a wealth of end-of-chapter problems, and a solutions manual for instructors available online, this is an invaluable book for electrical engineering, biomedical engineering, and physics students taking graduate courses on optical microscopy, as well as advanced undergraduates, professionals, and researchers looking for an accessible introduction to the field.

Clinical and research applications of anterior segment optical coherence tomography – a review

Abstract: Optical coherence tomography (OCT) is being employed more and more often to image pathologies and surgical anatomy within the anterior segment, specifically in anterior chamber biometry, corneal pachymetric mapping, angle evaluation and high-resolution cross-sectional imaging The cross-sectional imaging capability of OCT is similar to ultrasound, but its higher resolution allows OCT to measure and visualize very fine anatomic structures No contact is required In this review, we describe the utility and limitations of anterior segment OCT

Intra-retinal layer segmentation in optical coherence tomography images

Abstract: Retinal layer thickness, evaluated as a function of spatial position from optical coherence tomography (OCT) images is an important diagnostics marker for many retinal diseases. However, due to factors such as speckle noise, low image contrast, irregularly shaped morphological features such as retinal detachments, macular holes, and drusen, accurate segmentation of individual retinal layers is difficult. To address this issue, a computer method for retinal layer segmentation from OCT images is presented. An efficient two-step kernel-based optimization scheme is employed to first identify the approximate locations of the individual layers, which are then refined to obtain accurate segmentation results for the individual layers. The performance of the algorithm was tested on a set of retinal images acquired in-vivo from healthy and diseased rodent models with a high speed, high resolution OCT system. Experimental results show that the proposed approach provides accurate segmentation for OCT images affected by speckle noise, even in sub-optimal conditions of low image contrast and presence of irregularly shaped structural features in the OCT images.

Doppler optical micro-angiography for volumetric imaging of vascular perfusion in vivo

Abstract: We propose a Doppler optical micro-angiography (DOMAG) method to image flow velocities of the blood flowing in functional vessels within microcirculatory tissue beds in vivo. The method takes the advantages of recently developed optical micro-angiography (OMAG) technology, in which the endogenous optical signals backscattered from the moving blood cells are isolated from those originated from the tissue background, i.e., the tissue microstructures. The phase difference between adjacent A scans of OMAG flow signals is used to evaluate the flow velocity, similar to phase-resolved Doppler optical coherence tomography (PRDOCT). To meet the requirement of correlation between adjacent A scans in using the phase resolved technique to evaluate flow velocity, an ideal tissue-sample background (i.e., optically homogeneous tissue sample) is digitally reconstructed to replace the signals that represent the heterogeneous features of the static sample that are rejected in the OMAG flow images. Because of the ideal optical-homogeneous sample, DOMAG is free from the characteristic texture pattern noise due to the heterogeneous property of sample, leading to dramatic improvement of the imaging performance. A series of phantom flow experiments are performed to evaluate quantitatively the improved imaging performance. We then conduct in vivo experiments on a mouse brain to demonstrate that DOMAG is capable of quantifying the flow velocities within cerebrovascular network, down to capillary level resolution. Finally, we compare the in vivo imaging performance of DOMAG with that of PRDOCT, and show that DOMAG delivers at least 15-fold increase over the PRDOCT method in terms of the lower limit of flow velocity that can be detected.

Optical Imaging and Spectroscopy

Abstract: Preface. Acknowledgments. 1. Past, present and future. 1.1 Three revolutions. 1.2 Computational imaging. 1.3 Overview. 1.4 The fourth revolution. Problems. 2. Geometric imaging. 2.1 Visibility. 2.2 Optical elements. 2.3 Focal imaging. 2.4 Imaging systems. 2.5 Pinhole and coded aperture imaging. 2.6 Projection tomography. 2.7 Reference structure tomography. Problems. 3. Analysis. 3.1 Analytical tools. 3.2 Fields and transformations. 3.3 Fourier analysis. 3.4 Transfer functions and filters. 3.5 The Fresnel transformation. 3.6 The Whittaker-Shannon sampling theorem. 3.7 Discrete analysis of linear transformations. 3.8 Multiscale sampling. 3.9 B-splines. 3.10 Wavelets. Problems. 4. Wave imaging. 4.1 Waves and fields. 4.2 Wave model for optical fields. 4.3 Wave propagation. 4.4 Diffraction. 4.5 Wave analysis of optical elements. 4.6 Wave propagation through thin lenses. 4.7 Fourier analysis of wave imaging. 4.8 Holography. Problems. 5. Detection. 5.1 The Optoelectronic interface. 5.2 Quantum mechanics of optical detection. 5.3 Optoelectronic detectors. 5.3.1 Photoconductive detectors. 5.3.2 Photodiodes. 5.4 Physical characteristics of optical detectors. 5.5 Noise. 5.6 Charge coupled devices. 5.7 Active pixel sensors. 5.8 Infrared focal plane arrays. Problems. 6. Coherence imaging. 6.1 Coherence and spectral fields. 6.2 Coherence propagation. 6.3 Measuring coherence. 6.4 Fourier analysis of coherence imaging. 6.5 Optical coherence tomography. 6.6 Modal analysis. 6.7 Radiometry. Problems. 7. Sampling. 7.1 Samples and pixels. 7.2 Image plane sampling on electronic detector arrays. 7.3 Color imaging. 7.4 Practical sampling models. 7.5 Generalized sampling. Problems. 8. Coding and inverse problems. 8.1 Coding taxonomy. 8.2 Pixel coding. 8.3 Convolutional coding. 8.4 Implicit coding. 8.5 Inverse problems. Problems. 9. Spectroscopy. 9.1 Spectral measurements. 9.2 Spatially dispersive spectroscopy. 9.3 Coded aperture spectroscopy. 9.4 Interferometric Spectroscopy. 9.5 Resonant spectroscopy. 9.6 Spectroscopic filters. 9.7 Tunable filters. 9.8 2D spectroscopy. Problems. 10. Computational imaging. 10.1 Imaging systems. 10.2 Depth of field. 10.3 Resolution. 10.4 Multiple aperture imaging. 10.5 Generalized sampling revisited. 10.6 Spectral imaging. Problems. References.

Optical coherence tomography- based ophthalmic testing methods, devices and systems

Abstract: In accordance with one aspect of the present invention, an optical coherence tomography-based ophthalmic testing center system includes an optical coherence tomography instrument comprising an eyepiece for receiving at least one eye of a user or subject; a light source that outputs light that is directed through the eyepiece into the user's or subject's eye, an interferometer configured to produce optical interference using light reflected from the user's/subject's eye, an optical detector disposed so as to detect said optical interference; and a processing unit coupled to the detector. The ophthalmic testing center system can be configured to perform a multitude of self-administered functional and/or structural ophthalmic tests and output the test data

Optical coherence tomography of the retina and optic nerve - a review

Abstract: Optical coherence tomography (OCT) is a rapid non-contact method that allows in vivo imaging of the retina, optic nerve head and retinal nerve fibre layer (RNFL). Since its introduction in Ophthalmology approximately a decade ago, the use of this technology has disseminated into the clinical practice. OCT has proven to be a useful ancillary tool for assessing retinal diseases because of its capability to provide cross-sectional images of the retina, and also to perform quantitative analysis of retinal morphology. In glaucoma, the OCT represents one of the methods capable of documenting and analysing optic disc and RNFL morphology in attempt to diagnose and monitor glaucomatous optic neuropathy. Recently, the spectral domain OCT became available, a new technique that allowed major improvements particularly regarding image acquisition speed and image resolution. Future studies will address how these major technological advances will impact the use of the OCT in research and clinical practice.

Ultra high-speed swept source OCT imaging of the anterior segment of human eye at 200 kHz with adjustable imaging range

Abstract: We present an application of in vivo anterior segment imaging of the human eye with an ultrahigh speed swept source OCT instrument. For this purpose, a dedicated OCT system was designed and constructed. This instrument enables axial zooming by automatic reconfiguration of spectral sweep range; an enhanced imaging range mode enables imaging of the entire anterior segment while a high axial resolution mode provides detailed morphological information of the chamber angle and the cornea. The speed of 200,000 lines/s enables high sampling density in three-dimensional imaging of the entire cornea in 250 ms promising future applications of OCT for optical corneal topography, pachymetry and elevation maps. The results of a preliminary quantitative corneal analysis based on OCT data free form motion artifacts are presented. Additionally, a volumetric and real time reconstruction of dynamic processes, like pupillary reaction to light stimulus or blink-induced contact lens movements are demonstrated.

Laser-scanning optical-resolution photoacoustic microscopy.

Abstract: We have developed a laser-scanning optical-resolution photoacoustic microscopy method that can potentially fuse with existing optical microscopic imaging modalities. To acquire an image, the ultrasonic transducer is kept stationary during data acquisition, and only the laser light is raster scanned by an x-y galvanometer scanner. A lateral resolution of 7.8 microm and a circular field of view with a diameter of 6 mm were achieved in an optically clear medium. Using a laser system working at a pulse repetition rate of 1,024 Hz, the data acquisition time for an image consisting of 256 x 256 pixels was less than 2 min.

Detection of Glaucoma Progression with Stratus OCT Retinal Nerve Fiber Layer, Optic Nerve Head, and Macular Thickness Measurements

Abstract: Purpose To evaluate and compare the ability of optical coherence tomography (OCT) retinal nerve fiber layer (RNFL), optic nerve head, and macular thickness parameters to detect progressive structural damage in glaucoma.

Anterior segment imaging with Spectral OCT system using a high-speed CMOS camera.

Abstract: We describe a new ultrahigh speed Spectral OCT instrument making use of a CMOS camera and demonstrate high quality in vivo imaging of the anterior segment of the human eye. The high flexibility of the designed imaging system allows a wide range of imaging protocols. Two- and three-dimensional high quality OCT images of the cornea, the anterior chamber and the crystalline lens are presented. A high acquisition rate, up to 135,000 A-scans/second enables three-dimensional reconstruction of the anterior segment during lenticular accommodation, blinking and pupillary reaction to light stimulus. We demonstrate OCT tomographic real time imaging of the lens dynamics during accommodation and high quality OCT cross-sectional images of the entire anterior segment of the eye from the cornea up to posterior part of the crystalline lens.

Flowometry in optical coherence tomography for analyte level estimation

Abstract: Optical coherence tomography (herein “OCT”) based analyte monitoring systems are disclosed. In one aspect, techniques are disclosed that can identify fluid flow in vivo (e.g., blood flow), which can act as a metric for gauging the extent of blood perfusion in tissue. For instance, if OCT is to be used to estimate the level of an analyte (e.g., glucose) in tissue, a measure of the extent of blood flow can potentially indicate the presence of an analyte correlating region, which would be suitable for analyte level estimation with OCT. Another aspect is related to systems and methods for scanning multiple regions. An optical beam is moved across the surface of the tissue in two distinct manners. The first can be a coarse scan, moving the beam to provide distinct scanning positions on the skin. The second can be a fine scan where the beam is applied for more detailed analysis.

Volumetric microvascular imaging of human retina using optical coherence tomography with a novel motion contrast technique

Abstract: Phase variance-based motion contrast imaging is demonstrated using a spectral domain optical coherence tomography system for the in vivo human retina. This contrast technique spatially identifies locations of motion within the retina primarily associated with vasculature. Histogram-based noise analysis of the motion contrast images was used to reduce the motion noise created by transverse eye motion. En face summation images created from the 3D motion contrast data are presented with segmentation of selected retinal layers to provide non-invasive vascular visualization comparable to currently used invasive angiographic imaging. This motion contrast technique has demonstrated the ability to visualize resolution-limited vasculature independent of vessel orientation and flow velocity.

Optical coherence tomography device, method, and system

Abstract: In accordance with one aspect of the present invention, an optical coherence tomography instrument comprises an eyepiece for receiving at least one eye of a user is provided; a light source that outputs light that is directed through the eyepiece into the user's eye; an interferometer configured to produce optical interference using light reflected from the user's eye; an optical detector disposed so as to detect said optical interference; and electronics coupled to the detector. The electronics can be configured to perform a risk assessment analysis based on optical coherence tomography measurements obtained using the interferometer. An output device can be electrically coupled to the electronics, and may be configured to output the risk assessment to the user through the output device. The optical coherence tomography instrument can be self-administered, and the eyepiece can be a monocular system or a binocular system.

Review of biomedical optical imaging—a powerful, non-invasive, non-ionizing technology for improving in vivo diagnosis

Abstract: This paper reviews the recent developments in the field of biomedical optical imaging, emphasizing technologies that have been moved from 'bench top to bedside'. Important new developments in this field allow for unprecedented visualization of the tissue microstructure and enable quantitative mapping of disease-specific endogenous and exogenous substances. With these advances, optical imaging technologies are becoming powerful clinical tools for non-invasive and objective diagnosis, guided treatment and monitoring therapies. Recent developments in visible and infrared diffuse spectroscopy and imaging, spectral imaging, optical coherence tomography, confocal imaging, molecular imaging and dynamic spectral imaging are presented together with their derivative medical devices. Their perspectives and challenges are discussed.

Myopia Affects Retinal Nerve Fiber Layer Measurements as Determined by Optical Coherence Tomography

Abstract: PurposeTo determine whether increasing myopia is associated with thinner peripapillary retinal nerve fiber layer (RNFL) when measured by Stratus optical coherence tomography (OCT).DesignObservational cross-sectional study.MethodsNormal subjects with myopia underwent refractometry, axial length measu

Optical Coherence Tomography in Mouse Models of Retinal Degeneration

Abstract: PURPOSE Spectral domain optical coherence tomography (SD-OCT) allows cross-sectional visualization of retinal structures in vivo. Here, the authors report the efficacy of a commercially available SD-OCT device to study mouse models of retinal degeneration. METHODS C57BL/6 and BALB/c wild-type mice and three different mouse models of hereditary retinal degeneration (Rho(-/-), rd1, RPE65(-/-)) were investigated using confocal scanning laser ophthalmoscopy (cSLO) for en face visualization and SD-OCT for cross-sectional imaging of retinal structures. Histology was performed to correlate structural findings in SD-OCT with light microscopic data. RESULTS In C57BL/6 and BALB/c mice, cSLO and SD-OCT imaging provided structural details of frequently used control animals (central retinal thickness, CRT(C57BL/6) = 237 +/- 2 microm and CRT(BALB/c) = 211 +/- 10 microm). RPE65(-/-) mice at 11 months of age showed a significant reduction of retinal thickness (CRT(RPE65) = 193 +/- 2 microm) with thinning of the outer nuclear layer. Rho(-/-) mice at P28 demonstrated degenerative changes mainly in the outer retinal layers (CRT(Rho) = 193 +/- 2 microm). Examining rd1 animals before and after the onset of retinal degeneration allowed monitoring of disease progression (CRT(rd1 P11) = 246 +/- 4 microm, CRT(rd1 P28) = 143 +/- 4 microm). Correlation of CRT assessed by histology and SD-OCT was high (r(2) = 0.897). CONCLUSIONS The authors demonstrated cross-sectional visualization of retinal structures in wild-type mice and mouse models for retinal degeneration in vivo using a commercially available SD-OCT device. This method will help to reduce numbers of animals needed per study by allowing longitudinal study designs and will facilitate characterization of disease dynamics and evaluation of putative therapeutic effects after experimental interventions.