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Show moreField of the invention: The present invention is directed to a real-time imaging system and method that is particularly useful in the medical field, and more particularly, to a system and method for imaging and analysis of tissue and other samples using optical coherence tomography.Background of the invention: A variety of imaging techniques are used for the medical diagnosis and treatment of patients. Ultrasound imaging represents a prevalent technique. Ultrasound uses sound waves to obtain a cross-sectional image of an object. These waves are radiated by a transducer, directed into the tissues of a patient, and reflected from the tissues. The transducer also operates as a receiver to receive the reflected waves and electronically process them for ultimate display. Another imaging technique is referred to as Optical Coherence Tomography (OCT). OCT uses light to obtain a cross-sectional image of tissue. The use of light allows for faster scanning times than occurs in ultrasound technology. The depth of tissue scan in OCT is based on low coherence interferometry. Low coherence interferometry involves splitting a light beam from a low coherence light source into two beams, a sampling beam and a reference beam. These two beams are then used to form an interferometer. The sampling beam hits and penetrates the tissue, or other object, under measurement. The sampling or measurement beam is reflected or scattered from the tissue, carrying information about the reflecting points from the surface and the depth of tissue. The reference beam hits a reference reflector. For example, a mirror or a diffraction grating, and reflects from the reference reflector. The reference reflector either moves or is designed such that the reflection occurs at different distances from the beam splitting point and returns at a different point in time or in space, which actually represents the depth of scan. The time for the reference beam to return represents the desirable depth of penetration of tissue by the sampling beam. When the reflected beams meet, intensities from respective points with equal time delay form interference. A photodetector detects this interference and converts it into electrical signals. The signals are electronically processed and ultimately displayed, for example, on a computer screen or other monitor.Optical coherence tomography (OCT) is a relatively new, non-invasive optical imaging technique. OCT is analogous in principle to pulse-echo ultrasound imaging, but near-infrared light waves instead of acoustic waves are employed to probe the sample specimen. OCT has been primarily applied to imaging of biological tissues, providing micron-scale resolution in three dimensions to a depth of a few millimeters without contacting the tissue. We here disclose a number of advanced designs and techniques that extend the utility of OCT and/or are based on OCT. A number of papers and other references are cited below.
http://www.google.com/patents?vid=USPAT7061622
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Show moreBackgrounf of the invention: Optical Coherence Tomography (OCT) is a novel imaging technique which allows for noninvasive cross-sectional imaging in scattering or cloudy media with high spatial resolution and high dynamic range. OCT is a two-dimensional extension of Optical Coherence-Domain Reflectometry (OCDR) which is also commonly referred to as Optical Low Coherence Reflectometry (OLCR), in which a low temporal coherence light source is employed to obtain precise localization of reflections internal to a probed structure along the optic axis. The one-dimensional ranging technique of OCDR/OLCR has previously been utilized for characterization of bulk-, integrated-, and fiber-optic structures, as well as biological tissues. In OCT, this technique is extended to provide for scanning of the probe beam in a direction perpendicular to the optic axis, building up a two-dimensional data set comprising a cross-sectional image of internal tissue backscatter. Ophthalmic Applications of OCTOCT has previously been applied to imaging of biological tissues in vivo and in vitro, although the majority of initial biomedical imaging studies concentrated on transparent structures such as the eye. Initial ophthalmic imaging studies demonstrated significant potential for OCT imaging in routine examination of normal and abnormal ocular structures, including imaging of the cornea, iris, and other structures of the anterior eye; the lens and lens capsule; and numerous structures in the posterior eye, including the neurosensory retina, retinal nerve fiber layer, retinal pigment epithelium, and choroid. In OCT examination of the retina, initial in vivo clinical studies have demonstrated its utility in aiding diagnosis in a variety of vitreoretinal diseases, including macular hole, macular degeneration, detached retina, and glaucoma. Clinical trials of OCT imaging for ophthalmic applications are currently under way at several centers, and a commercial ophthalmic OCT scanner is available from Humphrey Systems of Dublin, Calif. OCT Imaging in Highly Scattering MediaSeveral recent publications have demonstrated the potential applications of OCT in highly scattering media for the measurement of tissue optical properties and imaging. Optical imaging in scattering media such as biological tissue is in general a very difficult problem, particularly for techniques such as OCT which depend primarily upon unscattered or singly-scattered light for image formation. It has been observed in preliminary studies and theoretical treatments that this singly-scattered gating requirement practically limits OCT imaging to a useful penetration depth of a few millimeters at best in nontransparent human tissues. Nonetheless, several authors have identified diagnostic scenarios in which a technique for improved, non-invasive 10–20-micron scale optical imaging near tissue surfaces has significant potential for clinical utility.
http://www.google.com/patents?vid=USPAT7102756
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Show moreTechnical field: The present invention relates generally to the field of optical coherence tomography and, more particularly, to a method and system for quantitative image correction of optical coherence tomography images of layered media. Background: Optical coherence tomography (OCT) is a technology that allows for non-invasive micron-scale resolution imaging in living biological tissues. Recent OCT research has focused on developing instrumentation appropriate for imaging in clinical settings (e.g., in ophthalmology, dermatology and gastroenterology), on resolution improvements, real-time imaging, and on functional imaging, such as in color Doppler OCT. Current-generation real-time OCT systems typically employ depth-priority scanning, with the axial scan implemented using a rapid-scan optical delay (RSOD) in the reference arm. The rapid axial scan is readily implemented using resonant scanners. However, the resulting sinusoidally varying delay axially distorts the resulting OCT imagines. In addition, the use of non-telecentric scan patterns is often necessitated by non-planar sample configurations (e.g., imagining the convex surface of the cornea or the concave surface of a hollow organ or tract). One major impediment to the use of OCT for quantitative morphological imaging is image distortions that may occur due to several mechanisms, including nonlinearities in the reference or sample scan mechanisms, non-telecentric (diverging or converging) scan geometries, and the refraction of probe light in the sample. Non-contact imaging, one of the primary advantages of OCT, also leads to significant image distortions due to refraction of the probe beam at the interface between air and smooth surfaces, such as the cornea, or liquid accumulations in internal organs. Image distortions due to refraction may also occur at internal smooth tissue index boundaries, such as the cornea-aqueous interface in the eye. Accordingly, a need exists for an improved method and system for quantitative imagine correction of OCT images, which overcome the above-referenced problems and others. Summary of the invention: According to one aspect of the invention, the invention is directed to a method of correcting optical coherence tomography (OCT) data obtained from a layered media having at least one interface. The method can include identifying the at least one interface from the obtained OCT data and correcting the OCT data for distortion at the at least one interface. According to another aspect of the invention, the invention is directed to a quantitative image correction method for optical coherence tomography (OCT). The method can include correcting for external distortions caused by scan geometry and correcting for intrinsic distortions within a sample. According to another aspect of the invention, the invention is directed to a non-invasive system for imaging an anterior portion of an eye.
http://www.google.com/patents?vid=USPAT7072047
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Show moreTechnical field: The invention relates to optical coherence tomography and, more particularly, to optical coherence tomography with molecular contrast capability. Background: Optical coherence tomography (OCT) is an emerging tool for real time in-situ tissue imaging with micrometer-scale resolution. Real-time OCT systems have been integrated into clinical medical diagnostic instruments, and functional extensions such as polarization-sensitive, Doppler, and spectroscopic OCT have recently been introduced. These functional enhancements add the ability to discern contrast due to stress, motion, and to some extent absorber concentration in samples such as biological tissues. However OCT remains a relatively contrast-starved imaging modality due to the low contrast in scattering coefficient between biological tissue types.
http://www.google.com/patents?vid=USPAT7075658
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Show moreTechnical field: The present invention relates generally to the field of optical coherence tomography and, more particularly, to a method and device for phase-referenced doppler optical coherence tomography. Background: Optical coherence tomography (OCT) is a technology that allows for non-invasive, cross-sectional optical imaging of biological media with high spatial resolution and high sensitivity. OCT is an extension of low-coherence or white-light interferometry, in which a low temporal coherence light source is utilized to obtain precise localization of reflections internal to a probed structure along an optic axis. In OCT, this technique is extended to enable scanning of the probe beam in the direction perpendicular to the optic axis, building up a two-dimensional reflectivity data set, used to create a cross-sectional gray-scale or false-color image of internal tissue backscatter. OCT has been applied to imaging of biological tissue in vitro and in vivo, as well as high resolution imaging of transparent tissues, such as ocular tissues. U.S. Pat. No. 5,944,690 provides a system and method for substantially increasing the resolution of OCT and also for increasing the information content of OCT images through coherent signal processing of the OCT interferogram data. Doppler OCT or Doppler OCT flow imaging is a functional extension of OCT. Doppler OCT (also referred to as Color Doppler OCT) employs low-coherence interferometry to achieve depth-resolved imaging of reflectivity and flow in biological tissues and other turbid media. In Doppler OCT, a scanning optical delay line (ODL) and optical heterodyne detection yield an interferogram with fringe visibility proportional to the electric field amplitude of the light returning from the sample and fringe frequency proportional to the differential phase delay velocity between the interferometer arms. For flow imaging, a variety of processing techniques have been employed to generate estimates of instantaneous fringe frequency. Deviation of fringe frequency from the expected Doppler shift imposed by the ODL can be taken as flow in the sample. Color Doppler OCT systems continue to improve in sensitivity. Some systems have been developed, which are sensitive enough to flow velocity, such that jitter due to instability of the interferometer components and/or motion of the sample with respect to the OCT interferometer becomes a limiting source of phase noise. In such a case, Doppler shifts of the OCT probe light due to motion of the sample with respect to the OCT interferometer are indistinguishable from Doppler shifts arising from blood flow. In some real-time medical OCT imaging applications, such as retinal imaging, in which the sample is living, sample motion is unavoidable and physical stabilization of the eye, for example, with respect to the interferometer is not practical.
http://www.google.com/patents?vid=USPAT7006232
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