Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-09-15
2001-08-07
Casler, Brian L. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S473000, C600S476000
Reexamination Certificate
active
06272367
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 &lgr;-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.
Recently, certain approaches to NIR imaging have been suggested. 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 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 situations.
In summary, there continues to be a need for an improved imaging system which utilizes visible or IR radiation of wavelengths sensitive to endogenous or exogenous pigments.
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 of the invention, a spectroscopic system includes at least one light source adapted to introduce, at multiple input ports, electromagnetic non-ionizing radiation of a known time-varying pattern of photon density and of a wavelength selected to be scattered and absorbed while migrating in the subject, the input ports being placed at selected locations on the subject to probe a selected quality of the subject; and radiation pattern control means adapted to achieve selected a time relationship of the introduced patterns to form resulting radiation that possesses a substantial gradient in photon density as a result of the interaction of the introduced patterns emanating from the input ports, the radiation being scattered and absorbed in migration paths in the subject. The gradient in photon density may be achieved by encoding the introduced radiation patterns with a selected difference in their relative amplitude, relative phase, relative frequency or relative time. The system also includes a detector adapted to detect over time, at a detection port placed at a selected location on the subject, the radiation that has migrated in the subject; processing means adapted to process signals of the detected radiation in relation to the introduced radiation to create processed data indicative of the influence of the subject upon the gradient of photon density; and evaluation means adapted to examine the subject by correlating the processed data with the locations of the input and output ports.
Preferred embodiments of this aspect of the invention include displacement means adapted to move synchronously all the optical input ports or move the detection ports to another location on a predetermined geometric pattern; at this location the examination of the subject is performed.
According to another aspect of the invention, a spectroscopic system includes at least one light source adapted to introduce, at multiple input ports, electromagnetic non-ionizing radiation of a known time-varying pattern of photon density and of a wavelength selected to be scattered and absorbed while migrating in the subject, the input ports being placed at selected locations on the subject to probe a selected quality of the subject; radiation pattern control means adapted to achieve a selected time relationship of the introduced patterns to form resulting radiation that possesses a substantial gradient in photon density as a result of the interaction of the introduced patterns emanating from the input ports, the radiation being scattered and absorbed in migration paths in the subject. The system also includes a detector adapted to detect over time, at a detection port placed at a selected location on the subject, the radiation that has migrated in the subject; displacement means adapted to move the detection port to various locations on a predetermined geometric pattern, the various locations being used to detect over time radiation that has migrated in the subject; processing means adapted to process signals of the detected radiation in relation to the introduced radiation to create processed data indicative of the influence of the subject upon the gradient of photon density; and evaluation means adapted to examine the subject by correlating the processed data with the locations of the input and output ports.
According to another aspect of the invention, a spectroscopic system includes at least one light source adapted to introduce, at multiple input ports, electromagnetic non-ionizing radiation of a known time-varying pattern of photon density and of a wavelength selected to be scattered and absorbed while migrating in the subject, the input ports being placed at selected locations on the subject to probe a selected quality of the subject; radiation pattern control means adapted to achieve a selected time relationship of the introduced patterns to form resulting radiation that possesses a substantial gradient in photon density as a result of the interaction of the introduced patterns emanating from the input ports, the radiation being scattered and absorbed in migration paths in the subject. The system also includes at least one detector adapted to detect over time, at multiple detection ports placed at selected locations on the subject, the radiation that has migrated in the subject; processing means adapted to process signals of the detected radiation in relation to the introduced radiation to create processed data indicative of the influence of the subject upon the gradient of photon density, and evaluation means adapted to examine the subject by correlating the processed data with the locations of the input and output ports.
Preferred embodiments of this aspect of the invention inclu
Casler Brian L.
Fish & Richardson P.C.
Non-Invasive Technology Inc.
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