JPH05115485A - Biological optical measurement device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an optical CT apparatus for performing function measurement of a living body using light and imaging the same, which efficiently measures from a plurality of detection sites of the living body in time. [Structure] Light from a light source unit 1 including a plurality of wavelengths illuminates an incident position of a subject 5 selected by a multi-input / multi-output optical switch 3. The light that has passed through the subject 5 is captured by the optical fibers from a plurality of parts, and again introduced into the detection unit 7 through the optical switch 3 by the optical fibers 6-1 to 6-m. At this time, a distribution is given to the optical path lengths of the optical fibers 6-1 to 6-m.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring information inside a living body using light.

[0002]

2. Description of the Related Art In recent years, several optical CT devices have been devised which measure and image a biological function using visible to near infrared light. Light in this wavelength range has relatively good biological permeability, and when these lights are used, the partial pressure of oxygen in the living body that reflects the biological function is obtained from the amount of light absorbed by hemoglobin in blood or cytochrome aa _{3 in} cells. It is possible. Such an apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-115232.
And JP-A-60-72542.

However, the light applied to the living body spreads spatially remarkably due to multiple scattering in the living body, so that the light detected after passing through the living body includes the light that has widely passed through the living body. Therefore, when image reproduction related to a biological function is performed using such detection light, it is difficult to obtain sufficient spatial resolution. Regarding this, irradiating a living body with pulsed light of tens of picoseconds, the optical path length in the living body increases due to multiple scattering, and the light incident position of the living body is detected from the light passing through the living body with a time delay. Japanese Patent Application Laid-Open No. 1-20932 discloses an apparatus for extracting only light that passes through a substantially linear position and has a small time delay using a nonlinear optical crystal.

On the other hand, even if the reduction of the spatial resolution due to the multiple scattering of light is prevented as described above, in order to reproduce as a CT image, the light incident on the living body is detected by detecting the light from a plurality of parts of the living body. It should be data for playback. Therefore, much data has to be captured. Therefore, some devices have been devised that efficiently detect light that has passed through a living body from a plurality of parts in a short time. For example, the apparatus described in Japanese Patent Laid-Open No. Sho 60-72542 is one in which the detection light from a plurality of parts is detected by one photodetector for each part by time division. Further, the apparatus described in JP-A-62-231625 detects the light passing through the living body from a plurality of parts by a plurality of photodetectors corresponding to the respective living body measurement parts.

[0005]

The light that has passed through the living body at a distance of several cm to ten and several cm is attenuated by about ten orders of magnitude with respect to the intensity of the incident light, so that the detected light becomes extremely weak light. In order to extract the amount of absorbed light such as hemoglobin or cytochrome aa ₃ relating to biological functions from such weak light and reproduce an accurate image, it is necessary to integrate the detected light extremely many times. Since the optical CT device detects light from a plurality of parts of a living body, it takes a long time to perform measurement for image reproduction, which is not preferable in terms of mental distress to a subject and measurement efficiency. ..

The device described in Japanese Patent Laid-Open No. 60-72542 cannot detect light from a plurality of parts of a living body at the same time, and thus there is a limit to the effect of shortening the measurement time. In addition, JP-A-62-1316
The device described in Japanese Patent Publication No. 25 can detect light from multiple parts of a living body at the same time, but since each photodetector corresponds to one photodetection part, the number of detectors required is the number of measurement parts. Becomes The weak light detector used in this case is usually expensive, and it is not economical to use a plurality of weak light detectors.

From the above, there is a demand for an apparatus that can detect light efficiently from a plurality of parts of a living body with a minimum number of detectors.

Therefore, as shown in FIG. 4, a photodetector 7 composed of one photodetector (here, a time-resolved photodetector is used) measures light from a plurality of parts of a living body. I have an idea. In FIG. 4, light passing through the living body from a plurality of parts of the living body with respect to light of tens of picoseconds applied to the living body is taken in by optical fibers 6-1 to 6-m, respectively, and the other end of these optical fibers is detected by the detection unit 7 It is shown arranged side by side. The living body passing light guided from the living body by the optical fibers 6-1 to 6-m is received by the light receiving surface 30 of the photodetector 7.
Are incident at an appropriate space interval. These lights emit photoelectrons on the light-receiving surface 30, and the electrons travel toward the fluorescent surface 32 due to the applied voltage. AC electric field generator 3
1 displaces the traveling direction of the above-mentioned electrons at high speed. As a result, a distribution image corresponding to the time change of the light emitted by the optical fibers 6-1 to 6-m is displayed on the fluorescent surface 32, and the time change of the light intensity is displayed by reading the distribution image with a TV camera or the like. It can measure at high speed.

FIG. 5 shows the time distribution formed on the fluorescent surface 32 by the detection light from a plurality of parts of the living body. Of this distribution, the Y-axis direction is time and the X-axis direction is the optical fiber 6-1.
Detection intensity time distributions 22-1 to 2 corresponding to 6 to 6-m
The detection position of 2-m is shown. The light incident on a living body having a time width of several tens of picoseconds is detected while the time width of the detection light is expanded from several hundreds of picoseconds to several nanoseconds by passing through the living body which is a light scatterer while undergoing multiple scattering.

In the method shown in FIG. 4, it is possible to detect light from a plurality of parts at a time, and at the same time, the light is scattered in the living body to be spatially spread and the optical path length is increased. Time-resolved light measurements can also be performed where the light is removed by a suitable time gate.

However, in such an apparatus, if the number of optical fibers 6-1 to 6-m, that is, the number of m is increased in order to measure the light from more parts of the living body at a time, the number in FIG. The optical fiber density on the light receiving surface 30 increases. As a result, due to the spatial spread of the light emitted by the optical fibers 6-1 to 6-m or the spatial fluctuations of the photoelectrons emitted from the light receiving surface 30, the measurement signal between the adjacent optical fibers is changed to the fluorescent surface 32. Will cross at. This phenomenon is called crosstalk, which makes it difficult to accurately measure the light detection position of each living body. Therefore, this device limits the number of photodetection sites from the living body that can be captured at one time.

Therefore, the time-resolved light measurement is performed in which light delayed in time as a result of spatially expanding the optical path length due to scattering of light in the living body is removed by an appropriate time gate, and at the same time, this crosstalk It is a problem to be solved by the present invention to reduce the influence as much as possible and detect light from a larger number of living body parts in a timely and efficient manner.

[0013]

[Means for Solving the Problems] Therefore, the fluorescent surface 3 of FIG.
This problem is solved by effectively using the time axis in 2.
This time axis is set to an appropriate length that can accommodate a plurality of detection pulse lights that have spread in time as the incident pulse lights pass through the living body, and the optical path lengths of the optical fibers 6-1 to 6-m are set. Make each one different.

[0014]

For example, by changing the optical path lengths of the optical fibers 6-1 to 6-m adjacent to each other in FIG. 4 alternately, the light emitted from the adjacent optical fibers is illuminated by the fluorescent surface 32.
And appear in different places in time. Therefore, it is possible to easily separate the signal from the adjacent fiber from the signal from the optical fiber that exactly corresponds to the original position of the fluorescent surface 32 and the crosstalk.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a biological optical measurement device showing an embodiment of the present invention. The light source unit 1 is from 500 nm to 15
It is composed of a plurality of laser light sources with a wavelength of 00 nm, and emits ultrashort pulsed light with a pulse width of several tens of picoseconds in order. The light emitted from this is introduced into the multi-input / multi-output optical switch 3 by the optical fiber 2. This light is connected to any one of the optical fibers 4-1 to 4-n arranged in a plurality of parts around the subject 5. Here, it is assumed to be the optical fiber 4-1. The subject 5 is irradiated with light by the optical fiber 4-1.

The light that has spread and passed through the subject 5 is detected by the optical fibers 4-2 to 4-n and introduced into the optical switch 3 again. These optical fibers 4-2 to 4-n are connected to the optical fibers 6-1 to 6-m inside the optical switch 3 in a one-to-one correspondence. At this time, the optical path lengths in the optical fibers 4-1 to 4-n and the optical switch 3 are set to be the same for all the optical paths, but the optical fibers 6-1 to 6-m are set to the respective optical fiber lengths. Make them different. Optical fiber 6
-1, 6-3, 6-5 ... Have a length a, while the optical fiber 6-
The lengths 2, 6-4, 6-6 ... Have a length of a + α. Even if the lengths of the optical fibers 6-1 to 6-m are different, the other ends of the optical fibers are arranged in a row to be arranged in front of the light detecting portion 7, for example, the light receiving surface 30 in FIG. A time-resolved light measuring device is used as the light detecting unit 7 here.

At this time, the light emitted to the light receiving surface 30 of FIG. 4 by the optical fibers 6-1 to 6-m is converted into the intensity distribution with respect to the temporal / spatial change of the light on the fluorescent surface 32. It is shown in FIG. Detection intensity time distribution 20-1 to 2 in FIG.
0-m corresponds to the light emitted by the optical fibers 6-1 to 6-m, respectively. Here, for example, in FIG.
Regarding the detection intensity time distribution 20-1 of _{No. 2} , the detection intensity from time t ₀ to t ₁ is the light emitted from the optical fiber 6-1 and the detection intensity after time t ₁ is the optical fiber 6-2.
Shows crosstalk from. This also applies to the time distribution 20-2 of the detected light intensity.
Since the optical path length -2 is longer than the optical fiber 6-1, the light from the optical fiber 6-2 is detected later in time at time t ₁ later. In the case of this detection intensity time distribution 20-2,
The detection intensity from the time t ₀ to the time t ₁ is the optical fiber 6-
Crosstalk from 1 and 6-3.

Crosstalk and signal light could not be separated by the conventional method in which the optical path length difference is not provided in the detection optical fiber, but in this method, both can be easily separated. These detected intensity time distributions are stored in the data storage unit 8 in FIG. 1, and these data are processed by the computer 9. Here, the difference in the detection time due to the removal of the crosstalk and the optical path length provided by the optical fibers 6-1 to 6-m is corrected by the computer 9 and is on a substantially straight line connecting the light incident position and the detection position. Signals which have passed through and are detected earlier in time are extracted by an appropriate time gate. When this series of measurements is completed with light of one wavelength, the computer 9 controls the light source unit 1 to change the measurement wavelength.

When the similar measurement is completed for all wavelengths, the optical switch 3 is then controlled by the computer 9 so that the optical fiber 2 introduced from the light source unit 1 into the optical switch 3, for example, the optical fiber By connecting to 4-2, the subject 5 is irradiated with light from a position different from the previous time. At this time, the light passing through the subject 5 is captured by the optical fiber 4-1 and the optical fibers 4-3 to 4-n, and the optical switches 3 controlled by the computer 9 respectively detect the optical fibers 6-1 to 6-. One-to-one connection with m. In this way, the light irradiation position on the subject 5 is sequentially changed to repeat the measurement, and finally the computer 9 performs image processing,
The image is displayed on the display unit 10 as an image relating to the biological function.

Next, FIG. 2 shows a second embodiment of the present invention. Here, the light propagating through the optical fibers 6-1 to 6-m is introduced into the optical path length varying device 11 in which the respective optical path lengths can be arbitrarily set. In this optical path length variable device 11, the light beams from the optical fibers 6-1 to 6-m are made into parallel light beams by the collimator lenses 12-1 to 12-m, respectively, and further reflected by the reflecting mirror 13 to be reflected by the prisms 14-1 to 14-.
m. The light reflected twice in each prism is reflected by the reflecting mirror 13 again, and the condenser lens 15
Optical fibers 18-1 to 18-by -1 to 15-m
m is introduced to the photodetector 7. Here, by continuously changing the position of the prism in the optical path length varying device 11, it is possible to arbitrarily change the continuous optical path length. Therefore, even when the setting of t ₁ in FIG. 6 needs to be changed due to a change in the size of the subject, it is not necessary to replace the optical fibers 6-1 to 6-m for each measurement, and It is possible to arbitrarily set the optimum optical path length difference while taking into consideration the change in the time width of the detection light caused by the difference in size 5. By controlling the optical path length varying device 11 with the computer 9, effective measurement can be performed.

Further, FIG. 3 shows a third embodiment of the present invention. Here, there is shown an apparatus in which the optical fiber interval arranged on the light receiving surface 30 of the photodetecting section 7 shown in FIG. 4 is set to such an extent that crosstalk does not occur, and yet the measurement can be performed efficiently in time.

In FIG. 3, optical fibers 6-1 having different optical path lengths are used.
And 6-2 are input to the optical multiplexer 16-1, and the optical fiber 17
Output to -1. Similarly, the optical fibers 6-3 and 6-4 are input to the optical multiplexer 16-2 and output to the optical fiber 17-2. The same operation is performed up to the optical fibers 6- (m-1) and 6-m. Then, the optical fibers 17-1 to 17-p are connected to the light receiving surface 3 shown in FIG. 4 at intervals such that crosstalk does not occur.
Place it at 0. The fiber arrangement density on the light receiving surface 30 is shown in FIG.
Although smaller than the above, these optical fibers contain information for two fibers separated in time. By time-resolving this transmitted light,
It becomes possible to separate and extract these. In this case,
FIG. 7 shows the detection intensity time distribution on the fluorescent surface 32 shown in FIG.
Shown in. Here, each detected intensity time distribution 21-1
To 21-p are optical fibers 17-1 to 17-, respectively.
Corresponds to p. In the detection time distribution 21-1, the detection intensity from time t ₀ to t ₁ is the light passing through the optical fiber 6-1 and the detection intensity after the time t ₁ is the light passing through the optical fiber 6-2. These lights are separated and corrected by the computer 9. In the arrangement of such fibers, for example, in this embodiment, two fibers are combined as one group and are combined, but this is combined with three or four fibers and an arbitrary plurality of fibers as a group, and By using such a multiple optical fiber optical multiplexer, it can be included in one fiber. In this way, it is possible to increase the number of optical fibers that can be taken in per measurement, that is, the measurement site of the subject 5.

[0023]

As described above, in the optical CT apparatus that measures the function of a living body by using light and visualizes it, it is possible to efficiently measure from a plurality of parts of the living body in time.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a biological optical measurement device according to the present invention.

FIG. 2 is a system diagram showing a second embodiment of the biological optical measurement device according to the present invention.

FIG. 3 is a system diagram showing a third embodiment of the biological optical measurement device according to the present invention.

FIG. 4 is an explanatory view showing the arrangement of optical fibers in the photodetector and the operation of the photodetector.

FIG. 5 is an explanatory diagram showing a waveform of a measurement signal.

6 is an explanatory diagram showing waveforms of measurement signals for the embodiment of FIG.

7 is an explanatory diagram showing waveforms of measurement signals for the embodiment of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source part, 2 ... Optical fiber, 3 ... Multi-input / multi-output optical switch, 4-1 to 4-n ... Optical fiber, 5 ... Subject, 6
-1 to 6-m ... Optical fiber, 7 ... Photodetector, 8 ... Data storage, 9 ... Computer, 10 ... Display.

Claims (6)

[Claims] 1. A living body is irradiated with light having a plurality of wavelengths in a visible to near-infrared wavelength range, light passing through the living body is detected from a plurality of parts of the living body, and the detected light is used to detect the inside of the living body. In the apparatus for measuring the form or function of the living body, the optical path length distribution is provided in the space from the light measurement position of each part of the living body to the light detection unit for converting light into an electric signal. apparatus. 2. The light source section for radiating light of a plurality of wavelengths according to claim 1, wherein the living body is irradiated with light by an optical fiber, and the light passing through the living body is distributed in length from a plurality of portions of the living body. A living body optical measurement device that is captured by an optical fiber that it has and that introduces the optical fiber into a light detection unit. 3. The living body optical measurement system according to claim 2, including a single photodetector capable of independently detecting the intensities of light captured from a plurality of parts of the living body, as a photodetecting section. 4. The living body light measuring device according to claim 3, wherein a light detecting unit for repeatedly emitting ultrashort pulsed light from the light source unit and detecting light passing through the living body has a time-resolving function. 5. The biological optical measurement according to claim 4, wherein an optical path length varying device that changes the optical path length by an arbitrary length is provided between a plurality of optical fibers that capture the light that has passed through the living body and a light detection unit. apparatus. 6. The optical fiber bundle according to claim 4, wherein a plurality of optical fiber bundles having different optical path lengths among a plurality of optical fibers for capturing light passing through the living body are set, and these optical fiber bundles are combined by an optical multiplexer. A living body optical measurement device that is introduced into one optical fiber and is provided with a plurality of such optical fiber bundles.