Optical system for measuring metabolism in a body and imaging method

• US 5,803,909 A
• Filed: 10/06/1995
• Issued: 09/08/1998
• Est. Priority Date: 10/06/1994
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ito, Yoshitoshi, Yamashita, Yuichi, Maki, Atsushi, Koizumi, Hideaki, Kawaguchi, Fumio
• Primary Examiner(s): Bahr, Jennifer
• Assistant Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US08/539,871
• Time in Patent Office: 1,068 Days
• Field of Search: 128/633, 128/664, 128/665, 356/41, 600/310, 600/311, 600/314, 600/315, 600/316, 600/322, 600/323, 600/326, 600/327, 600/473, 600/476
• US Class Current: 600/310
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/0042 for the brain
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/18 for vehicle drivers or machine operators
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C
• CPC Class Codes: A61B 6/03 Computed tomography [CT] echo-tomography A61B8/14
• CPC Class Codes: A61B 6/507 for determination of haemodynamic parameters, e.g. perfusion CT

Abstract

Light rays of a plurality of wavelengths which are modulated in intensity with a plurality of different frequencies are irradiated on a plurality of irradiation positions on the surface of a living body, and time-variable changes in living body transmitting light intensity levels corresponding to the respective wavelengths and the respective irradiation positions are measured at different positions on the surface Changes in concentration values of absorbers are determined from the living body transmitting light intensity levels and a measuring point is set on a perpendicular extending through an intermediate point between the incident point and each detection point to image a function of the living body. The measuring time is shortened by estimating fluctuation attributable to the living body, and a local change in hemodynamic movement can be measured by detecting light rays transmitting through the interior of the living body by light detection at two different sites (equidistant from the light incident point) on a subject and by separating only the local change in hemodynamic movement from an overall change in hemodynamic movement in the living body in accordance with a logarithmic difference between the two detection signals.

Claims

1. A living body optical measurement system comprising:

a plurality of light irradiation means for irradiating light rays having the wavelength range of 600 nm to 1400 nm at a plurality of light irradiation positions on a subject;

a plurality of light receiving means for detecting light rays irradiated from said plurality of light irradiation means and transmitted through an interior of said subject to a plurality of light detecting positions to thereby generate light intensity signals representing intensities of light rays transmitted through said subject, wherein distances between each said light irradiation position and associated said light detecting positions means are substantially equidistant;

memory means for storing, in time sequence, the light intensity signals detected by said plurality of light receiving means at every wavelength light, irradiation position and light detecting position of the irradiated light ray;

arithmetic means for performing conversion into signals of the object to be measured at every set of light irradiation position and light detecting position by using the light intensity signals stored in said memory means; and

image preparation and display means for obtaining signals of presumptive measuring points determined from the light irradiation positions and the light detecting positions on a basis of the signals of the object to be measured output from said arithmetic means, for selecting ones of signals of the presumptive measuring points on a basis of sets of light irradiation positions and light detecting positions which are considered to be substantially same, and for estimating distribution of signal values within a plane including the selected signals of presumptive measuring points and displaying the estimated inhomogeneous distribution as an image.

2. An imaging system according to claim 1, wherein different light frequencies are allocated to each said light irradiation position to facilitate calculating multi-channel signals simultaneously.

3. A living body optical measurement system comprising:

a plurality of light irradiation means for irradiating light rays having the wavelength range of 600 nm to 1400 nm at a plurality of light irradiation positions on a subject;

a plurality of light receiving means for detecting light rays irradiated from said plurality of light irradiation means and transmitted through an interior of said subject to a plurality of light detecting positions to thereby generate light intensity signals representing intensities of light rays transmitted through said subject, wherein distances between each said light irradiation position and associated said light detecting positions means are substantially equidistant;

memory means for storing, in time sequence, the light intensity signals detected by said plurality of light receiving means at every wavelength, light irradiation position and light detecting position of the irradiated light ray;

arithmetic means for performing conversion into signals of the object to be measured at every set of light irradiation position and light detecting position by using the light intensity signals stored in said memory means;

image preparation and display means for obtaining signals of presumptive measuring points determined from the light irradiation positions and the light detecting positions on a basis of the signals of the object to be measured output from said arithmetic means, for selecting ones of signals of the presumptive measuring points on a basis of sets of light irradiation positions and light detecting positions which are considered to be substantially same, and for estimating distribution of signal values within a plane including the selected signals of presumptive measuring points and displaying the estimated distribution as an image; and

wherein each of said plurality of light irradiation means includes a plurality of light sources having different wavelengths, modulators for modulating the light rays of said plurality of light sources with different frequencies and wave guide means for guiding a plurality of modulated light rays to the light irradiation positions, and each of said plurality of light receiving means includes separation means for separating the light intensity signals at every frequency of said modulator to thereby separate independently the light intensity signals at every wavelength, light irradiation position and light detecting position of the irradiated light rays.

4. A living body optical measurement system according to claim 3, wherein said separation means is comprised of lock-in amplifiers driven by modulation signals of said modulators.

5. A living body optical measurement system comprising:

a plurality of light irradiation means for irradiating light rays having the wavelength range of 600 nm to 1400 nm at a plurality of light irradiation positions on a subject;

a plurality of light receiving means for detecting light rays irradiated from said plurality of light irradiation means and transmitted through an interior of said subject to a plurality of light detecting positions to thereby generate light intensity signals representing intensities of light rays transmitted through said subject, wherein distances between each said light irradiation position and associated said light detecting positions means are substantially equidistant;

memory means for storing, in time sequence, the light intensity signals detected by said plurality of light receiving means at every wavelength, light irradiation position and light detecting position of the irradiated light ray;

arithmetic means for performing conversion into signals of the object to be measured at every set of light irradiation position and light detecting position by using the light intensity signals stored in said memory means;

image preparation and display means for obtaining signals of presumptive measuring points determined from the light irradiation positions and the light detecting positions on a basis of the signals of the object to be measured output from said arithmetic means, for selecting ones of signals of the presumptive measuring points on a basis of sets of light irradiation positions and light detecting positions which are considered to be substantially same, and for estimating distribution of signal values within a plane including the selected signals of presumptive measuring points and displaying the estimated distribution as an image; and

wherein a number of said plurality of light sources having different wavelengths equals a number of kinds of light absorbers to be measured.

6. An imaging method comprising the steps of:

irradiating light rays having a wavelength range of 600 nm to 1400 nm at a plurality of light irradiation positions of a subject;

detecting light rays transmitted through an interior of said subject at at least one light detection point associated with each of said plurality of light irradiation positions to thereby generate light intensity signals representing intensities of light rays transmitted through said subject, wherein distances between each light irradiation position and associated light detecting positions are substantially equidistant;

calculating signals at a plurality of presumptive measuring points from said plurality of light irradiation positions;

determining inhomogeneous concentration values of light absorbers included in the interior of said subject; and

displaying said concentration values of light absorbers at the plurality of presumptive measuring points obtained in the above step as a two-dimensional plane image representative of said subject.

7. An imaging system according to claim 6, wherein in said irradiating step, different light frequencies are allocated to each said light irradiation position to facilitate calculating multi-channel signals simultaneously.

8. An imaging method 6, comprising the steps of:

irradiating light rays having a wavelength range of 600 nm to 1400 nm at a plurality of light irradiation positions of a subject;

detecting light rays transmitted through an interior of said subject at at least one light detection point associated with each of said plurality of light irradiation positions to thereby generate light intensity signals representing intensities of light rays transmitted through said subject, wherein distances between each light irradiation position and associated light detecting positions are substantially equidistant;

calculating signals at a plurality of presumptive measuring points from said plurality of light irradiation positions;

determining concentration values of light absorbers included in the interior of said subject;

displaying said concentration values of light absorbers at the plurality of presumptive measuring points obtained in the above step as a two-dimensional plane image representative of said subject; and

wherein each presumptive measuring point is an arbitrary position on a perpendicular vertical axis extending to a surface of said subject and extending to the interior of said subject from an intermediate point between a light irradiation position and light detection position, and light absorber concentration values obtained at said plurality of presumptive measuring points and interpolated light absorber concentration values obtained by interpolating the light absorber concentration values obtained at said plurality of presumptive measuring points between the respective presumptive measuring points are displayed as a topography image.

9. An imaging method according to claim 8, wherein an image is obtained by using as said light absorber concentration value a light absorber concentration value at a desired time point or a value obtained by averaging amounts of changes in light absorber concentration values over a predetermined interval of time.

10. An imaging method according to claim 8, wherein light absorber concentration values or amounts of changes in light absorber concentration values are determined at desired intervals of time to obtain a time-variable image which is continuous over respective intervals of time.

11. An imaging method according to claim 8, wherein an image representing form information about the interior of a subject measured using magnetic resonance and X-rays is displayed together with information about said light absorber concentration values while being superimposed upon said topography image on a same screen.

12. An imaging method according to claim 11, wherein the image representing form information is a cerebral surface image.

13. An imaging method according to claim 8, wherein light absorber concentration values or amounts of changes in light absorber concentration values are determined at desired intervals of time, a time-variable change in said change amounts measured at one desired measuring point is used as a reference to determine a correlation of a time-variable change in said change amounts at another measuring point to the reference, thereby obtaining a time-varying image of a correlation function which is continuous over a respective intervals of time.

14. An imaging system comprising:

means for irradiating light rays onto a subject at a plurality of light irradiation positions;

means for detecting light rays transmitted through an interior of said subject at a plurality of light detecting positions, wherein distances between each light irradiation position and associated light detecting positions are substantially equidistant;

means for calculating signals based upon light rays detected by said means for detecting light rays; and

image preparation and display means for obtaining signals of measuring points determined from the light irradiation positions and the light detecting positions on a basis of the signals and displaying an estimated inhomogeneous signal distribution as an image.

15. An imaging system according to claim 14, wherein said means for irradiating light rays irradiate light rays having a wavelength range of 600 nm to 1400 nm on a plurality of light irradiation positions of a subject, said means for detecting light rays detect light rays transmitting through the interior of said subject at at least one light detection point associated with each of said plurality of light irradiation positions, and said means for calculating signals calculates signals at a plurality of presumptive measuring points from said plurality of light irradiation positions.

16. An imaging system according to claim 15, further comprising determining means for determining concentration values of light absorbers included in the interior of said subject, and means for displaying concentration values of light absorbers at the plurality of presumptive measuring points obtained by said determining means as a two-dimensional plane image representative of said subject.

17. An imaging system according to claim 16, wherein said subject is a living body and said imaging system is an optical measurement system.

18. An imaging system 14, comprising:

means for irradiating light rays onto a subject at a plurality of light irradiation positions;

means for detecting light rays transmitted through an interior of said subject at a plurality of light detecting positions, wherein distances between each light irradiation position and associated light detecting positions are substantially equidistant;

means for calculating signals based upon light rays detected by said means for detecting light rays; and

wherein different light frequencies are allocated to each said light irradiation position to facilitate calculating multi-channel signals simultaneously.