Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-05-02
2003-04-01
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S476000
Reexamination Certificate
active
06542772
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to examination and imaging of biological tissue using visible or infra-red radiation.
Traditionally, potentially harmful ionizing radiation (for example, X-ray or &ggr;-ray) has been used to image biological tissue. This radiation propagates in the tissue on straight, ballistic tracks, i.e., scattering of the radiation is negligible. Thus, imaging is based on evaluation of the absorption levels of different tissue types. For example, in roentgenography the X-ray film contains darker and lighter spots. In more complicated systems, such as computerized tomography (CT), a cross-sectional picture of human organs is created by transmitting X-ray radiation through a section of the human body at different angles and by electronically detecting the variation in X-ray transmission. The detected intensity information is digitally stored in a computer which reconstructs the X-ray absorption of the tissue at a multiplicity of points located in one cross-sectional plane.
Near infra-red radiation (NIR) has been used to study non-invasively the oxygen metabolism in tissue (for example, the brain, finger, or ear lobe). Using visible, NIR and infra-red (IR) radiation for medical imaging could bring several advantages. In the NIR or IR range the contrast factor between a tumor and a tissue is much larger than in the X-ray range. In addition, the visible to IR radiation is preferred over the X-ray radiation since it is non-ionizing; thus, it potentially causes fewer side effects. However, with lower energy radiation, such as visible or infra-red radiation, the radiation is strongly scattered and absorbed in biological tissue, and the migration path cannot be approximated by a straight line, making inapplicable certain aspects of cross-sectional imaging techniques.
Several different approaches to NIR imaging have been suggested in the past. One approach undertaken by Oda et al. in “Non-Invasive Hemoglobin Oxygenation Monitor and Computerized Tomography of NIR Spectrometry,” SPIE Vol. 1431, p. 284, 1991, utilizes NIR radiation in an analogous way to the use of X-ray radiation in an X-ray CT. In this device, the X-ray source is replaced by three laser diodes emitting light in the NIR range. The NIR-CT uses a set of photomultipliers to detect the light of the three laser diodes transmitted through the imaged tissue. The detected data are manipulated by a computer of the original X-ray CT scanner system in the same way as the detected X-ray data would be.
Different approaches were also suggested by S. R. Arriadge et al. in “Reconstruction Methods for Infra-red Absorption Imaging,” SPIE Vol. 1431, p. 204, 1991; F. A. Grünbaum et al. in “Diffuse Tomography,” SPIE Vol. 1431, p. 232, 1991; B. Chance et al., SPIE Vol. 1431 (1991), p. 84, p. 180, and p. 264; and others who recognized the scattering aspect of the non-ionizing radiation and its importance in imaging. None of those techniques have fully satisfied all needs in tissue examination.
In summary, there continues to be a need for an improved system which utilizes visible or IR radiation of wavelengths sensitive to endogenous or exogenous pigments to examine or image biological tissue.
SUMMARY OF THE INVENTION
The invention relates to systems and methods for spectroscopic examination of a subject positioned between input and detection ports of the spectroscopic system applied to the subject.
According to one aspect, the invention features a spectroscopic system for examination of tissue of a subject, including: at least one light source of electromagnetic radiation of a visible or infrared wavelength selected to be scattered and absorbed while migrating in the tissue; at least two input ports, optically coupled to the light source, constructed to introduce at selected input locations of the examined tissue the radiation of known intensities that define a null plane in the tissue; a detection port located at a selected detection location of the examined tissue relative to the null plane; a detector, optically coupled to the detection port, constructed to detect during operation the radiation that has migrated in the examined tissue; a detector circuit connected to and receiving detection signal from the detector; the detector circuit including a sample-and-hold circuit and a subtraction circuit, both connected to the detector circuit, constructed to subtract detection signals corresponding to radiation that has migrated from a first input port to the detection port and from a second input port to the detection port, respectively, to obtain processed data; and a processor, connected to and receiving the processed data from the subtraction circuit, adapted to evaluate the examined tissue.
According to another aspect, the invention features a spectroscopic system for examination of tissue of a subject, including: a source of electromagnetic radiation of a visible or infrared wavelength; an input port, optically coupled to the light source, constructed to introduce at a selected input location of the examined tissue the radiation; a detector optically coupled to at least two detection ports located at selected detection locations defining a null plane in the examined tissue, the detector constructed to detect radiation that has migrated in the examined tissue-to the detection ports; a detector circuit connected to and receiving detection signal from the detector, the detector circuit including a sample-and-hold circuit and a subtraction circuit; the detector circuit constructed to correlate emission of the radiation from the input port with detection of radiation scattered and absorbed while migrating in the tissue at the first detection port, the detected radiation being stored as a first detection signal; the detector circuit further constructed to correlate emission of the radiation from the input port with detection of radiation scattered and absorbed while migrating in the tissue at the second detection port, the detected radiation being stored as a second detection signal; the subtraction circuit constructed to subtract the detection signals; and a processor, connected to and receiving the processed data from the subtraction circuit, constructed to evaluate the examined tissue.
Embodiments of the invention may include one or more of the following additional features.
The spectroscopic system may include intensity control means constructed to regulate intensities of radiation emitted from the first and second input ports. The intensity control means may be constructed to regulate the intensities in a manner that sweeps the null plane over at least a portion of the volume of the examined tissue.
The spectroscopic system may preferably include positioning means constructed to displace the detection port to detection locations corresponding to the null plane or positioning means constructed to displace the input ports to selected locations.
The spectroscopic system may preferably include detector controller means constructed to changes the relative sensitivity of detection at the first and second detection port in order to sweep the null plane over at least a portion of the volume of the examined tissue.
Preferably, the subtraction circuit includes an analog to digital converter, connected to the sample-and-hold circuit, constructed to digitize the detection signal to produce digital detection signal, the subtraction circuit subtracting the digital detection signals corresponding to radiation that ha s migrated from a first input port to the detection port and from a second input port to the detection port, respectively, to obtain the processed data. The processor may preferably be further adapted to locate, in the tissue volume, a tissue region exhibiting different scattering or absorptive properties than the rest of the examined tissue volume.
The input or detection ports may be preferably arranged in a linear array. The input or detection ports may be preferably arranged a two dimensional array. The spectroscopic may preferably further include an image processor, connected to and receiving the proce
Fish & Richardson P.C.
Non-Invasive Technology Inc.
Winakur Eric F.
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