Optical system for measuring metabolism in a body and imaging method

• US 6,128,517 A
• Filed: 09/08/1998
• Issued: 10/03/2000
• 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): WINAKUR, ERIC FRANK
• Application Number:
  US09/149,155
• Time in Patent Office: 756 Days
• Field of Search: 600/310, 600/322, 600/323, 600/324, 600/335, 600/336, 600/407, 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 of the living body. After completion of the measurement or during the measurement, changes in concentration values of absorbers in the living body are determined from the living body transmitting light intensity levels of the plurality of wavelengths detected at the respective detection points and a measuring point is set on a perpendicular extending through an intermediate point between the incident point and each detection point so as to image a function of the living body. In living body optical measurement system and method, the measuring time is shortened by estimating fluctuation attributable to the living body, 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, and a local change in hemodynamic movement can be measured by detecting light rays transmitting through the interior of the living body by means of two means for light detection disposed at different two 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 method for measuring a living body transmitting light intensity with respect to a living body which experiences both load-induced-fluctuation and non-load-induced-fluctuation comprising:

irradiating light on the living body while alternately setting a loading time during which a load is applied to the living body and an unloading time during which the load is not applied to the living body, wherein a relaxation time following the loading time is set, and a signal corresponding to a fluctuation attributable to the non-load-induced fluctuation of the living body and contained in a measured signal is estimated from a signal obtained during the unloading time exclusive of the relaxation time.

2. A living body optical measurement method according to claim 1, wherein a load preceding estimation time which immediately precedes each loading time is set, a load succeeding estimation time which immediately succeeds each relaxation time is set, and the signal corresponding to the fluctuation attributable to the living body and contained in the measured signal is estimated for each loading time from a measured signal obtained during the load preceding estimation time and a measured signal obtained during the load succeeding estimation time.

3. A living body optical measurement method according to claim 1, or 2, wherein an arbitrary function having a single or a plurality of indefinite coefficients is set, said indefinite coefficients are determined through a method of least squares such that said arbitrary function is optimally adaptive to a measured signal obtained during the unloading time exclusive of the relaxation time, and a thus determined optimal adaptive function is made to be a signal corresponding to the fluctuation attributable to the living body.

4. A living body optical measurement method according to claim 1, or 2, wherein a difference between the measured signal and the signal corresponding to the fluctuation attributable to the living body is calculated.

5. A living body optical measurement method according to claim 1, wherein by using a ratio between the estimated signal corresponding to the fluctuation attributable to the living body and the measured signal, a extinction coefficient to a light source wavelength of hemoglobin oxide and a extinction coefficient to a light source wavelength of reduced hemoglobin, a relative change amount of a sum of concentration values of hemoglobin oxide and reduced hemoglobin in the living body, a relative change amount of concentration of hemoglobin oxide, a relative change amount of concentration of reduced hemoglobin, a time-variable change in each of the relative change amounts, an integral relative change amount obtained by integrating each of the relative change amounts over a predetermined interval of time, or an averaged relative change amount over a predetermined interval of time, is calculated.

6. A signal display method in a living body optical measurement system in which a living body transmitting light intensity is measured with respect to a living body which experiences both load-induced-fluctuation and non-load-induced-fluctuation comprising:

irradiating light on a living body, and a measured signal or a signal resulting from calculation of the measured signal is displayed on a display unit, wherein a signal corresponding to fluctuation attributable to the non-load-induced-fluctuation over time of the living body and contained in the measured signal is estimated and the estimated signal is displayed together with the measured signal.

13. A signal display method in a living body optical measurement system according to any one of claims 6 to 9, wherein different signals or different calculation results are displayed using different colors or different kinds of lines.

16. A signal display method in a living body optical measurement system according to any one of claims 6 to 9, wherein a plurality of signals at a plurality of measuring positions are displayed together with a figure illustrative of a measuring portion of the living body, a figure illustrative of measuring positions, and a figure designating a correspondence between the measuring positions and the signals.

7. A signal display method in a living body optical measurement system in which a living body transmitting light intensity is measured with respect to a living body which experiences both load-induced-fluctuation and non-load-induced-fluctuation, comprising:

irradiating light on a living body while alternately setting a loading time during which a load is applied on the living body and an unloading time during which the load is not applied to the living body, and a measured signal or a signal calculated from the measured signal is displayed on a display unit, wherein a signal corresponding to fluctuation attributable to the non-load-induced-fluctuation of the living body and contained in the measured signal is estimated from a signal obtained during the unloading time, and the estimated signal, together with the measured signal, is displayed as an estimation non-load signal.

10. A signal display method in a living body optical measurement system according to claim 7, 8, or 9, wherein an arbitrary function having a single or a plurality of indefinite coefficients is set, said indefinite coefficients are determined through a method of least squares such that said arbitrary function is optimally adaptive to a measured signal obtained during the unloading time exclusive of the relaxation time, and a thus determined optimal adaptive function is made to be a signal corresponding to fluctuation attributable to the living body.

11. A signal display method in a living body optical measurement system according to any one of claims 7 to 9, wherein the difference between a measured signal and the estimation non-load signal is calculated and a result of calculation is displayed.

12. A signal display method in a living body optical measurement system according to any one of claims 7 to 9, wherein by using a ratio between the estimation non-load signal and the measured signal, an extinction coefficient to a light source wavelength of hemoglobin oxide and an extinction coefficient to the light source wavelength of reduced hemoglobin, a relative change amount of a sum of concentration values of hemoglobin oxide and reduced hemoglobin in the living body, a relative change amount of concentration of hemoglobin oxide, a relative change amount of concentration of reduced hemoglobin, a time-variable change in each of the relative change amounts, an integral relative change amount obtained by integrating each of the relative change amounts over a predetermined interval of time, or an averaged relative change amount over a predetermined interval of time, is calculated.

14. A signal display method in a living body optical measurement system according to any one of claims 7 to 9, wherein concurrent display of figures illustrative of start and end times of the loading time is effected.

15. A signal display method in a living body optical measurement system according to any one of claims 7 to 9, wherein the measured signal is displayed concurrently with any measurement on a real time basis, and the estimation non-load signal is displayed until a time point exceeding the time for measurement is displayed.

17. A signal display method in a living body optical measurement system according to any one of claims 7 to 9, wherein an image taken by an image diagnostic system is used as a figure illustrative of measuring positions.

8. A signal display method in a living body optical measurement system in which a living body transmitting light intensity is measured with respect to a living body which experiences both load-induced-fluctuation and non-load-induced-fluctuation, comprising:

irradiating light on a living body while alternately setting a loading time during which a load is applied to the living body and an unloading time during which the load is not applied to the living body, and a measured signal or a signal calculated from the measured signal is displayed on a display unit, wherein a relaxation time following the loading time is set, a signal corresponding to fluctuation attributable to the non-load-induced-fluctuation of the living body and contained in the measured signal is estimated from a signal obtained during the unloading time exclusive of the relaxation time, and the estimated signal, together with the measured signal, is displayed as an estimation non-load signal.

9. A signal display method in a living body optical measurement system according to claim 8, wherein a load preceding estimation time which immediately precedes each loading time is set, a load succeeding estimation time which immediately succeeds each relaxation time is set, and an estimation non-load signal is determined for each loading time from a loading-preceding signal obtained during the loading preceding estimation time and a loading-succeeding signal obtained during the loading succeeding estimation time.

18. A living body optical measurement method for measuring a living body transmitting light intensity with respect to a living body which experiences both load-induced-fluctuation and non-load-induced-fluctuation, comprising:

irradiating light on the living body while alternately setting a loading time during which a load is applied to the living body and an unloading time during which the load is not applied to the living body, wherein a relaxation time following the loading time is set, and wherein the irradiating of light occurs over a plurality of periods of the loading time, unloading time and relaxation time, and a signal corresponding to a fluctuation attributable to the non-load-induced fluctuation of the living body and contained in a measured signal is estimated from a signal obtained over the plurality of periods but during the unloading time exclusive of the relaxation time.