Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2001-02-06
2003-02-04
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S310000, C600S473000, C600S476000, C250S252100
Reexamination Certificate
active
06516209
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to optical imaging systems, optical probes thereof, and methods thereof for providing images of spatial or temporal distribution of chromophores or properties thereof in a physiological medium. In particular, the present invention relates to a self-calibrating optical imaging system. The present invention is applicable to optical imaging systems whose operation is based on wave equations such as the Beer-Lambert equation, modified Beer-Lambert equation, photon diffusion equation, and their equivalents.
BACKGROUND OF THE INVENTION
Near-infrared spectroscopy has been used to measure various physiological properties in animal and human subjects. The basic principle underlying the near-infrared spectroscopy is that a physiological medium such as tissues and cells includes a variety of light-absorbing and light-scattering chromophores which can interact with electromagnetic waves transmitted thereto and traveling therethrough. For example, human tissues include numerous chromophores among which deoxygenated and oxygenated hemoglobins are the most dominant chromophores in the spectrum range of 600 nm to 900 nm. Therefore, the near-infrared spectroscope has been applied to measure oxygen levels in the physiological medium in terms of tissue hemoglobin oxygen saturation (or simply “oxygen saturation” hereinafter). Technical background for the near-infrared spectroscopy and diffuse optical imaging has been discussed in, e.g., Neuman, M. R., “Pulse Oximetry: Physical Principles, Technical Realization and Present Limitations,”
Adv. Exp. Med. Biol
., vol. 220, p.135-144, 1987, and Severinghaus, J. W., “History and Recent Developments in Pulse Oximetry,”
Scan. J. Clin. and Lab. Investigations
, vol. 53, p.105-111, 1993.
Various techniques have been developed for the near-infrared spectroscopy, including time-resolved spectroscopy (TRS), phase modulation spectroscopy (PMS), and continuous wave spectroscopy (CWS). In a homogeneous, semi-infinite model, the TRS and PMS are generally used to solve the photon diffusion equation, to obtain the spectra of absorption coefficients and reduced scattering coefficients of the physiological medium, and to estimate concentrations of the oxygenated and deoxygenated hemoglobins and oxygen saturation. The CWS has generally been used to solve the modified Beer-Lambert equation and to calculate changes in the concentrations of the oxygenated as well as deoxygenated hemoglobin.
Despite their capability of providing hemoglobin concentrations as well as the oxygen saturation, the major disadvantage of the TRS and PMS is that the equipment has to be bulky and, therefore, expensive. The CWS may be manufactured at a lower cost but is generally limited in its utility, for it can estimate only the changes in the hemoglobin concentrations but not the absolute values thereof Accordingly, the CWS cannot provide the oxygen saturation. The prior art technology also requires a priori calibration of optical probes before their clinical application by, e.g., measuring a baseline in a reference medium or in a homogeneous portion of the medium. Furthermore, all prior art technology employs complicated image reconstruction algorithms to generate images of two-dimensional and/or three-dimensional distribution of the chromophore properties.
Therefore, there exist needs for an efficient, compact, and relatively cheap optical imaging system which self-calibrates itself without relying on external measurement or data and which provides two- and/or three-dimensional images on a substantially real time basis.
SUMMARY OF THE INVENTION
The present invention generally relates to optical imaging systems, optical probes, signal and/or image processing algorithms, and methods thereof for providing two- or three-dimensional images of spatial or temporal distribution of chromophores or their properties in a physiological medium. More particularly, the present invention relates to novel self-calibrating optical imaging systems and methods thereof.
In one aspect of the present invention, an optical imaging system is provided to generate images of distribution of chromophores or their properties in target areas of various physiological media. The optical imaging system includes at least one wave source arranged to irradiate electromagnetic waves into the target areas of the medium and at least one wave detector arranged to detect electromagnetic waves from the target areas and to generate output signal in response thereto. The optical imaging system further includes an optical probe, a signal analyzer, and a signal processor. The optical probe typically includes the wave source and wave detector. The signal analyzer receives, from the wave detector, a first output signal which is representative of the distribution of the chromophores or their properties in a first target area of the medium. The signal analyzer analyzes an amplitude of each point of the first output signal and selects one or more points or portions of the first output signal having substantially similar first amplitudes. The signal processor calculates a first baseline from the first output signal, where the first baseline generally corresponds to a representative amplitude of the first amplitudes of the foregoing points or portions, and provides a self-calibrated first output signal by manipulating the first output signal and first baseline thereof. Therefore, the optical imaging system provides the self-calibrated output signal representing a spatial distribution and/or temporal variation of the chromophores or their properties in the first target area.
The foregoing optical imaging systems, probes, algorithms, and methods (collectively referred to as “optical imaging system” or “optical probe” hereinafter) of the present invention provide numerous advantages. Contrary to the prior art optical imaging devices that require a priori measurement and estimation of an output signal baseline in a reference medium (or area) before their clinical applications, the optical imaging system of the present invention allows a user to directly scan a target area, to obtain the output signal, and to simultaneously obtain the baseline of the output signal. Accordingly, the optical imaging system of the present invention obviates the need for a prior estimation of the baseline in other reference media (or areas). In addition, because the foregoing optical imaging system can estimate the baseline and the output signals from the same target area, it does not suffer from noises or errors attributed to different optical characteristics between the reference and target areas. Furthermore, due to simpler algorithms for estimating the baseline, the optical imaging system of the present invention allows real-time calibration of the output signals and, therefore, contributes to the real-time construction of images of the distribution of the chromophore or its properties.
Embodiments of this aspect of the present invention includes one or more of the following features.
The optical probe includes a scanning area which is almost equal to or as large as at least a substantial portion of the first target area of the medium. Multiple wave sources and detectors are disposed in the scanning area so that the chromophore properties in the first target area can be measured by a single measurement in the first target area. In the alternative, the optical probe may include a scanning area which may be only a small region of the first target area. In this embodiment, the optical imaging system includes an actuator member arranged to move at least one of the wave source and wave detector so that at least a substantial portion of the first target area can be scanned thereby. Accordingly, the wave detector can generate multiple first output signals while the optical probe or its main housing is positioned and maintained stationary in the first target area. This embodiment allows construction of compact optical probes with a minimal number of the wave sources and/or detectors implemented thereto. In addit
Cheng Xuefeng
Hu Guobao
Li Feng
Wang Lai
Wang Ming
Pennie & Edmonds LLP
Photonify Technologies, Inc.
Winakur Eric F.
LandOfFree
Self-calibrating optical imaging system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Self-calibrating optical imaging system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Self-calibrating optical imaging system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3176155