Showing papers on "Optical coherence tomography published in 1994"

Micrometer-Scale Resolution Imaging of the Anterior Eye In Vivo With Optical Coherence Tomography

Abstract: Objective: To demonstrate a new diagnostic technique, optical coherence tomography, for highresolution cross-sectional imaging of structures in the anterior segment of the human eye in vivo. Optical coherence tomography is a new, noninvasive, noncontact optical imaging modality that has spatial resolution superior to that of conventional clinical ultrasonography ( 90 dB). Design: Survey of intraocular structure and dimension measurements. Setting: Laboratory. Patients: Convenience sample. Main Outcome Measures: Correlation with range of accepted normal intraocular structure profiles and dimensions. Results: Direct in vivo measurements with micrometer-scale resolution were performed of corneal thickness and surface profile (including visualization of the corneal epithelium), anterior chamber depth and angle, and iris thickness and surface profile. Dense nuclear cataracts were successfully imaged through their full thickness in a cold cataract model in calf eyes in vitro. Conclusions: Optical coherence tomography has potential as a diagnostic tool for applications in noncontact biometry, anterior chamber angle assessment, identification and monitoring of intraocular masses and tumors, and elucidation of abnormalities of the cornea, iris, and crystalline lens.

Optical coherence microscopy in scattering media.

Abstract: We describe a novel technique, based on optical coherence tomography, for enhanced optical sectioning in confocal microscopy. Confocal imaging deep into highly scattering media is demonstrated and compared with the predictions of a single-backscatter theory.

Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering.

Abstract: Addresses fundamental issues that underlie the interpretation of images acquired from turbid tissues by optical-coherence tomography (OCT). The attenuation and backscattering properties of freshly excised rat arteries and their dependence on the focusing and collection optics of the OCT system were measured at two wavelengths in the near infrared (830 nm and 1300 nm). Determined from the ratio of the magnitudes of the reflections from glass plates placed on both sides of the arteries, the mean attenuation coefficient of the arterial wall was found to be in the range 14< mu t<22 mm-1 at 830 nm and 11< mu t<20 mm-1 at 1300 nm. The measured values of mu t were lowest for the longer source wavelength and for probe beams with the smallest average diameters. The observed dependence of mu t on beam size indicates that relatively large-scale variations in the index of refraction of the tissue contributed to degradation of the transverse spatial coherence of the beam. The authors introduce a framework for understanding and quantifying beam-size effects by way of the mutual-coherence function. The fact that spatial variations in backscattering and attenuation (which includes spatial-coherence losses) have similar effects on OCT signals makes the origin of the signals difficult to determine. Evidence is given that suggests that, in spite of this difficulty, certain features of microstructures embedded several hundred micrometres deep in a turbid tissue can still be detected and characterized.

Optical coherence tomography assisted ophthalmologic surgical microscope

Abstract: Ophthalmologic surgical microscope which is combined internally with an optical coherence tomography ("OCT") apparatus wherein auto-focusing is provided by driving a motorized internal focusing lens of the ophthalmologic surgical microscope with a signal output from the OCT apparatus. An embodiment of the inventive ophthalmologic surgical microscope includes: (a) an optical coherence tomography ("OCT") apparatus; (b) a beamcombiner for internally coupling output from the OCT apparatus into the ophthalmologic surgical microscope; and (c) a motor for moving an internal focusing lens of the ophthalmologic surgical microscope in response to a signal from the OCT apparatus, whereby the ophthalmologic surgical microscope is auto-focused.

In-vivo dual-beam optical coherence tomography

Abstract: Laser interferometry can be used to synthesize in vivo optical tomograms of the ocular tissue noninvasively. As a first example an in vivo partial coherence tomogram obtained from the optical nerve head of a human being is presented. The inherent high precision and sensitivity can make this technique into a very powerful diagnostic tool in ophthalmology.

Optical coherence microscopy

Abstract: We report a new method for improved optical sectioning in confocal microscopy. Optical coherence microscopy (OCM) uses low-coherence interferometry to improve image contrast in highly scattering media. OCM is an adaptation of optical coherence tomography (OCT), a new method for non-invasive cross-sectional imaging of tissue microstructure.1 The extension of this technique to confocal microscopy offers the potential for micron-resolution imaging without the need for biopsy in highly scattering media such as skin and endoscopically accessible tissues.

In vivo optical coherence tomography of human skin microstructure

Abstract: A compact effective optical coherence tomography (OCT) system is presented. It contains approximately equals 0.3 mW superluminescent diode with spectral width 30 nm FWHM (providing approximately equals 15 micrometers longitudinal resolution) and fiber interferometer with integrated longitudinal scanning. The dynamic range 60 dB allows to observe structure of human skin in vivo up to 1.5 mm in depth. A comparison of obtained tomographs with data of histologic analysis of the same samples of the skin have been carried out to identify the observed structures and determine their optical properties. This technique allows one to perform noncontact, noninvasive diagnostic of early stages of different pathological state of the skin, to measure the burn depth and to observe the process of the recovery. Unlike scanning confocal microscopy, OCT is more suitable for an endoscopic investigation of the mucous membranes of hollow organs. Possible diagnostic applications include dermatology, gastroenterology, gynecology, urology, oncology, othorinolaryngology, transplantology. The most promising features are the potential possibility of differential diagnosis of precancer and various types of cancer, estimation of the invasion depth, differential diagnosis of inflammation and dystrophic processes, control of radical operative treatment.

Biomedical imaging using optical coherent tomography

Abstract: Optical Coherence Tomography (OCT) is a new optical technique for performing non-contact, micron resolution, cross sectional tomography imaging in biological systems. The authors discuss applications of OCT to ophthalmology, general medicine, and microscopy.

Method and apparatus for optical coherence tomographic fundus imaging

Abstract: Apparatus for illuminating the fundus of an eye with a scanned sample beam of radiation, the scanned sample beam emerging from a beam scanner which is exposed to a sample beam, which apparatus is for use in optical coherence tomography. An embodiment of the apparatus includes: a scanner lens and a beamsplitter for transferring radiation from the scanned sample beam, including chief rays of the sample beam which emerge from a point of final deflection of the beam scanner, and (b) lens focusing the transferred radiation so that the scanned sample beam is focused onto the fundus by the eye. In accordance with the invention the scanner lens is fixed with respect to the beam scanner so that the point of final deflection is located substantially in the back focal plane of the scanner lens and the scanner lens is movable.

Biological imaging using optical coherence tomography and microscopy

Abstract: rected by Fresnel factors) at those hydrophobic/water interfaces. The broad spectral features between 3000 a-' and 3600 cm-' are due to hydrogen-bonded OH stretches. A peak at 3200 cm-' indicates a bond ordering (or ice-like structure) in water molecules arrangement as observed for quartdice spectrum (Fig. 1D). A similar structure is also observed for the quartz/OTS/water interfaces. This indicates that this rigid hydrophobic wall is instrumental in forcing the surface water molecules to be more orderly arranged into the ice-like structure because of the physical restriction in packing molecules against the wall. Structure and properties of water molecules at partially wettable water/quartz interace are also presented. *Department of Physics, University of Californin and Materials Sciences Division, lawence Berkeley laboratory, Berkeley, California 94720