Image analysis – Applications – Biomedical applications
Reexamination Certificate
2001-02-06
2004-10-05
Patel, Jayanti K. (Department: 2625)
Image analysis
Applications
Biomedical applications
C600S431000, C356S342000
Reexamination Certificate
active
06801648
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 their properties in various physiological media. More particularly, the present invention relates to optical imaging systems and/or optical probes thereof including symmetrically arranged optical sensors such as wave sources and/or detectors. The present invention is applicable to any optical imaging systems and/or optical probes thereof whose operation is based on wave equations including 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 (“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 have generally been 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 and deoxygenated hemoglobins.
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 requires complicated image reconstruction algorithms to generate images of two-dimensional and/or three-dimensional distribution of the chromophores or their properties.
Accordingly, there exist needs for more efficient and reliable optical imaging systems and optical probes thereof for measuring absolute values of chromophores or their properties, for calibrating signals and images from such systems and probes while obviating the need for separate calibration procedure, and for constructing the images of the foregoing distribution of the chromophores or their properties on a substantially real time basis.
SUMMARY OF THE INVENTION
The present invention generally relates to optical imaging systems, optical probes thereof, and methods therefor (collectively referred to as “optical imaging system” or “optical probe” hereinafter) for providing two-dimensional or three-dimensional images of spatial or temporal distribution of chromophores or their properties in various physiological media. More particularly, the present invention relates to the optical imaging systems that are equipped with optical probes incorporating symmetrically arranged wave sources and wave detectors.
In one aspect of the invention, an optical imaging system is provided for generating images of a target area of a physiological medium, where the images represent two- and/or three-dimensional spatial and/or temporal distribution of the chromophores or their properties in the target area of the medium. Such an optical imaging system typically includes at least one wave source arranged to form optical coupling with the physiological medium and to irradiate electromagnetic waves into the medium and at least one wave detector arranged to detect electromagnetic waves from the medium and to generate output signal in response thereto. The optical imaging system then groups the wave sources and detectors such that each pair of one wave source and one wave detector forms a scanning element in which the wave source irradiates electromagnetic waves into the target area of the medium and in which the wave detector detects the electromagnetic waves irradiated by the wave source and generates the output signal in response thereto. The optical imaging system also groups the wave sources and detectors (or groups multiple scanning elements themselves) in order to define multiple symmetric scanning units each of which includes at least two wave sources and at least two wave detectors such as a first wave source, second wave source, first wave detector, and second wave detector. The first wave source may be disposed closer to the first wave detector than the second wave detector, while the second wave source is disposed closer to the second wave detector than the first wave detector. The wave sources and detectors are also arranged so that a first near-distance between the first wave source and first wave detector is identical or substantially similar to a second near-distance between the second wave source and second wave detector. In addition, a first far-distance between the first wave source and the second wave detector is identical or substantially similar to a second far-distance between the second wave source and the first wave detector. The near-distance is preferably about one half of the far-distance but may also be arranged to be longer or shorter than one half of the far-distance.
Embodiments of this aspect of the present invention includes one or more of the following features.
The symmetric scanning unit may include an axis of symmetry such that the first and second wave sources are disposed symmetric to such axis and the first and second wave detectors are also disposed symmetric thereto. Multiple symmetric scanning units may be arranged to include at least one common wave source and/or at least one common wave detector.
The wave sources and detectors of such scanning units may be substantially linearly disposed so that the wave sources (or detectors) are interposed between the wave detectors (or sources). Two or more symmetric scanning units may share the common axis of symmetry, e.g., where the first scanning unit has a first source-detector arrangement and where the second scanning unit is disposed below the first scanning unit and has the same first arrangement or, in the alternative, has a second source-detector arrangement which is different from or substantially reverse to the first source-detector arrangement. In one embodiment, four symmetric scanning units may be arranged to share the common axis of symmetry, e.g., where the first scanning unit has a first source-detector arrangement, where the second scanning unit is disposed below the first scanning unit and has a second source-detector arrangement substantially reverse to the fi
Azarian Seyed
Patel Jayanti K.
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