Optical system for measuring metabolism in a body and imaging method

• US 7,286,870 B2
• Filed: 07/09/2001
• Issued: 10/23/2007
• Est. Priority Date: 10/06/1994
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ito, Yoshitoshi, Yamashita, Yuichi, Maki, Atsushi, Koizumi, Hideaki, Kawaguchi, Fumio
• Primary Examiner(s): MANTIS MERCADER, ELENI M
• Application Number:
  US09/900,144
• Publication Number:
  US 20010047131A1
• Time in Patent Office: 2,297 Days
• Field of Search: 600/310, 600/473, 600475-477, 600/407, 382/128, 356340-342
• US Class Current: 600/476
• 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

In an optical measurement system and imaging method adapted to measure in vivo information in a living body without harming the living body, 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 of the living body. Light is utilized to image the results of the measurements, in which the measuring time is shortened by estimating fluctuation attributable to the living body, and the presence or absence of a change in measured signal can be decided easily by displaying an estimation signal and a measured signal at a time.

Claims

1. A living body optical measurement system comprising:

light irradiation means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal, wherein for the atleast two sets of combination of light irradiation and light detection positions, the distance between the light irradiation and light detection positions being equal for each set.

2. A living body optical measurement system according to claim 1 comprising a light detection probe unit for fixing an optical fiber end of said light irradiation means and an optical fiber end of said light detection means, and an optical measuring unit including an electric signal processing circuit comprised of a light source of said light irradiation means and a photodetector of said light receiving means.

3. A living body optical measurement system according to claim 1, comprising a logarithmic amplifier and a differential amplifier, wherein a light detection signal is logarithmically amplified and then a logarithmic difference signal is generated by the differential amplifier.

4. A living body optical measurement system according to claim 1, wherein said light irradiation means includes an optical fiber for connecting a light source and the light irradiation position, and said light detection means includes an optical fiber for connecting a photodetector and the light detection position.

5. A living body optical measurement system according to claim 1, wherein a light irradiation position, a first detection position, a second detection position, a third detection position set on a half line extending from its origin at the light irradiation position to pass through the first detection position, and a fourth detection position set on a half line extending from its origin at the light irradiation position to pass through the second detection position, wherein a first logarithmic difference signal between light detection signals detected at said first and third detection positions and a second logarithmic difference signal between transmitting light intensity levels detected at said second and fourth detection positions are measured, and a difference signal between said first and second logarithmic difference signals is measured.

6. A living body optical measurement system according to claim 1, comprising:

the light irradiation means including

first light irradiation means for irradiating light on the surface of the living body;

first irradiation light intensity detection means for detecting the irradiation light intensity from said first light irradiation means;

second light irradiation means for irradiating light on the surface of the living body;

second irradiation light intensity detection means for detecting the irradiation light intensity from said second light irradiation means;

light detection means for detecting the intensity of light attributable to said first light irradiation means or said second light irradiation means and transmitting through the interior of the living body so as to go out of the surface of the living body;

means for generating a first logarithmic difference signal between an output of said first irradiation light intensity detection means and an output of said light detection means attibutable to said first light irradiation means;

means for generating a second logarithmic differences signal between an output of said second irradiation light detection means attributable to said second light irradiation means; and

means for measuring a difference signal between said first and second logarithmic difference signals.

7. A living body optical measurement system according to claim 1, wherein irradiation light from said light irradiation means is modulated in intensity, and only a frequency component of the detection signal from said light detection means which equals a frequency for the intensity modulation is extracted for use by a lock-in amplifier or through a Fourier transform processing.

8. A living body optical measurement system according to claim 1, wherein a number m of wavelengths of irradiation light equals a number n of light irradiation positions, and n×

m kinds of intensity modulation frequencies for the light source are used.

9. A living body optical measurement method using the living body optical measurement system as recited in claim 1, wherein measurement is carried out by setting the light irradiation position and the light detection positions on the surface of the living such that a signal from a region where extinction characteristics changes locally on the basis of a change in hemodynamic movement in the living body is contained in a light intensity signal detected at at least one light detection position but is not contained in a light intensity signal detected at at least another light detection position.

10. A living body optical measurement system according to claim 1, wherein after a logarithmic difference signal between different sites of detection position is so adjusted as to be zero under the condition that the change does not occur at the region where extinction characteristics changes locally in the living body, measurement is started and a displacement value of the difference signal is used as the measured signal.

11. A living body optical measurement system comprising:

light irradiating means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least sets of combination of light irradiation and light detection positions are provided, and

a logarithmic amplifier and a differential amplifier, wherein a light detection signal is logarithmically amplified and then a logarithmic difference signal is generated by the differential amplifier, and wherein the logarithmic difference signal between detection signals for the respective sets is used as a measured signal.

12. A living body optical measurement system comprising:

light irradiation means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal, wherein said light irradiation means includes an optical fiber for connecting a light source and the light irradiation position, and said light detection means includes an optical fiber for connecting a photodetector and the light detection position.

13. A living body optical measurement system comprising:

light irradiation meand for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal,

wherein a light irradiation position, a first detection position, a second detection position, a third detection position set on a half line extending from its origin at the light irradiation position to passs through the first detection position, and a fourth detection position set on a half line extending from its origin at the light irradiation position to pass through the second detection position, wherein a first logarithmic difference signal between light detection signals detected at said first and third detection positions and a second logarithmic difference signal between transmitting light intensity levels detected at said second and fourth detection positions are measured, and a difference signal between said first and second logarithmic difference signals is measured.

14. A living body optical measurement system comprising:

light irradiation means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal, the light irradiation means including;

first light irradiation means for irradiating light on the surface of the living body;

first irradiation light intensity detection means for detecting the irradiation light intensity from said first light irradiation means;

second light irradiation means for irradiating light on the surface of the living body;

second irradiation light intensity detection means for detecting the irradiation light intensity from said second light irradiation means;

light detection means for detecting the intensity of light attributable to said first light irradiation means or said second light irradiation means and transmitting through the interior of the living body so as to go out of the surface of the living body;

means for generating a first logarithmic difference signal between an output of said first irradiation light intensity detection means and an output of said light detection means attributable to said first light irradiation means;

means for generating a second logarithmic differences signal between an output of said second irradiation light intensity detection means and an output of said light detection means attributable to said second light irradiation means; and

means for measuring a difference signal between said first and second logarithmic difference signals.

15. A living body optical measurement system comprising:

light irradiation means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of the combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal;

wherein irradiation light from said light irradiation means is modulated in intensity, and only a frequency component of the detection signal from said light detection means which equals a frequency for the intensity modulation is extracted for use by a lock-in amplifier or through a Fourier transform processing.

16. A living body optical measurement system comprising:

light irradiation means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal;

wherein a number m of wavelengths of irradiation light equals a number n of light irradiation positions, and n×

m kinds of intensity modulation frequencies for the light source are used.

17. A living body optical measurement method using the living body optical measurement system comprising:

light irradiation means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal;

wherein measurement is carried out by setting the light irradiation position and the light detection positions on the surface of the living body such that a signal from a region where extinction characteristics changes locally on the basis of a change in hemodynamic movement in the living body is contained in a light intensity signal is detected at at least one light detection position but is not contained in a light intensity signal detected at at least another light detection position.

18. A living body optical measurement system comprising:

light irradiation means for irradiating light on the surface of a living body and light detecting means for detecting the intensity of light transmitting through the interior of the living body and going out of the surface of the living body, wherein at least two sets of combination of light irradiation and light detection positions are provided, and a logarithmic difference signal between detection signals for the respective sets is used as a measured signal;

wherein after a logarithmic difference signal between different sites of detection position is so adjusted as to be zero under the condition that the change does not occur at the region where extinction characteristics changes locally in the living body, measurements is started and a displacement value of the difference signal us used as the measured signal.