Optics: measuring and testing – By light interference
Reexamination Certificate
2001-04-06
2003-04-22
Lateef, Marvin M. (Department: 3737)
Optics: measuring and testing
By light interference
Reexamination Certificate
active
06552796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to an apparatus and method for selective data collection and/or utilization using optical coherence tomography. In particular, the invention is directed to an apparatus and method of collecting and/or utilizing, using optical coherence tomography, only that imaging information relevant to a particular medical diagnosis/assessment.
2. Background of the Related Art
Optical coherence tomography (OCT) is a relatively new imaging modality with the ability to perform high resolution, high-sensitivity, cross sectional imaging of microstructures. OCT has several significant advantages over ultrasound and other established imaging techniques. First, OCT can directly measure cross-sectional microstructure on a micron scale. Second, OCT can perform imaging of structures in situ and without contact. Third, imaging can be performed in real time, and fourth, because OCT technology is based on fiber optics, it can be interfaced with a wide range of medical, microscopic, and industrial instruments.
The operating principle of OCT is analogous to that of ultrasound B-mode imaging, except OCT uses light rather than sound and performs imaging by measuring the intensity of light backscattered from a sample being imaged. OCT produces two-, or three-dimensional images by directing an optical beam at an object, and measuring backscattered light as the beam is scanned across the object. An OCT image is a gray scale or false color two-dimensional representation of backscattered light intensity in a cross-sectional plane.
In medical imaging, the OCT image represents the differential backscattered contrast between different tissue types on a micron scale. Using infrared light, state-of-the-art OCT imaging systems can achieve resolutions approximately 5-25× higher than other imaging modalities used in clinical medicine.
There are a variety of interferometric embodiments of OCT systems. For example, one typical implementation uses a fiber optic coupler as the basis of a Michelson interferometer. One of the arms of the interferometer delivers and scans the optical beam on a sample, while the other arm functions as a reference arm with a high-speed longitudinal scanning mechanism. When the optical path-length to a reflection site within the sample matches the path-length in the reference arm, coherent optical interference occurs at the photodetector. The interference signal is detected, demodulated, processed, stored and/or displayed to yield the backscattered light intensity versus depth for a given transverse or angular position of the incident beam. Examples of OCT systems are taught in copending application Ser. No. 09/233,421 [Attorney Docket No. CDT-01] and U.S. Pat. Nos. 5,321,501, 5,459,570, and 6,111,645, which are hereby incorporated by reference.
OCT imaging can be performed non-invasively and in real time over approximately the same depth over which tissue is removed in a biopsy. Thus, OCT can be used in applications where conventional biopsies are impractical or impossible.
A tremendous amount of data is collected during OCT imaging because of the high resolution of the modality. The large amount of raw data that makes up the image or series of images in a cine-loop can cause a data storage problem, as well as a real-time scan conversion problem. In addition, the signal-to-noise ratio in a well designed OCT system is limited by the number of photons the imaging probe can collect for each pixel in the resultant image.
The references discussed within this disclosure are incorporated by reference where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
SUMMARY OF THE INVENTION
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Another object of the invention is to solve the above problems and/or disadvantages by improving the data efficiency of OCT systems. For a given light source, the number of photons collected in each image pixel can be increased by allowing more photon collection time per pixel. All other things being equal, this can be achieved by scanning fewer pixels in the image.
Another object of the invention is to increase the signal-to-noise ratio of OCT images.
A further object of the invention is to decrease the data processing and storage needs of an OCT system.
A still further object of the invention is to allow for higher frame rates given the same signal-to-noise ratio as conventional OCT systems.
Another object of the invention is to allow for higher line densities given the same signal-to-noise ratio as conventional OCT systems.
These and other advantages can be accomplished by methods and apparatuses for performing optical imaging on a system that continually adjusts the path-length of the reference arm in a manner that keeps the desired region of interest of an image within a restricted range of an OCT system. According to methods and apparatuses described herein, the path-length can be adjusted either manually by the operator or automatically according to a programmed algorithm.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
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Goodnow John W.
Magnin Paul
Petersen Christopher L.
Schmitt Joseph
Fleshner & Kim LLP
Lateef Marvin M.
LightLab Imaging, LLC
Sanders John R.
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