JP2000088742A - Light-measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the interaction between ultrasonic waves and light in performing the metabolic measurement and the like of the inside of an organism. SOLUTION: A light-scattering medium 10 is a living body or the like, and a laser beam with a constant polarization angle is applied by a light application part 12. In the light-scattering medium 10, the laser beam generates multiple scattering. An ultrasonic beam B is formed by an ultrasonic vibrator 16 and light is polarized when passing through it. The polarization component is detected by a light reception part 14, thus labeling an observation site T with ultrasonic waves by utilizing polarization due to birefringence caused by the ultrasonic waves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical measurement device,
In particular, the present invention relates to an optical measurement device that measures a light scattering medium (for example, a living body) using ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, optical measuring devices have been used in various fields. In the field of biological measurement, an optical CT (Computed Tomography) device, a blood analyzer, and the like are known as optical measurement devices. In these devices, for example, light (near-infrared light or the like) is applied to the living body from outside the body, and light transmitted through the living body is detected. Then, based on the detection signal, tomographic imaging, collection of metabolic information (for example, quantitative determination of hemoglobin), and the like are performed.

[0003] By the way, living tissue is a light scattering medium,
Light that has entered the living body is multiple-scattered. Therefore, it is extremely difficult to discriminate only metabolic information at a specific observation site in a living body by simply observing light from outside the body. For this reason, various proposals have been made, and among them, the "method using ultrasonic waves" is considered promising (for example, LVWang and X. Zhao: Applied Optics as related technologies)
36 (1997) 7277 and M. Kemple, M. Larionov, D. Zaslavsky, a
nd AZGenack: J. Opt. Soc. Am. A 14 (1997) 1151).

In this method, an ultrasonic wave is applied to a light scattering medium from, for example, a direction orthogonal to a light beam. Ultrasound can be locally concentrated at an observation site in a living body, as seen in an existing ultrasonic diagnostic apparatus. In a state where ultrasonic waves are applied to the inside of a living body, elastic waves form a refractive index distribution with respect to light in the living body. That is, it is considered that a dense and dense state of the tissue is formed. In that case, when the light travels through the observation site, the density of the tissue acts on the light, and the light is modulated in some way. Therefore, if only the modulation component is extracted from the received light signal, the metabolic information at the observation site can be discriminated.

[0005]

As described above, optical measurement using ultrasonic waves has been conventionally proposed. However, an ultrasonic-based type that can observe the interaction between ultrasonic waves and light more faithfully is proposed. There is a need for an optical measurement device.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an apparatus capable of accurately measuring the interaction between an ultrasonic wave and light in measuring a light scattering medium. .

[0007]

(1) In order to achieve the above object, the present invention provides a light irradiating means for irradiating a light scattering medium with a light beam having a first polarization angle; For an observation site in the medium, ultrasonic irradiation means for irradiating an ultrasonic beam, and among the scattered light emitted from the light scattering medium, receive a light component polarized by the action of the ultrasonic wave, Light receiving means for outputting a light receiving signal.

According to the above configuration, the light scattering medium such as a living body is irradiated with the light beam, and simultaneously with the ultrasonic beam. Light entering the light scattering medium undergoes multiple scattering, while ultrasonic waves are locally applied to the observation site. When a part of the scattered light passes through the observation site, it is polarized at the time of the passage. That is, it is presumed that the ultrasonic wave causes a structural change in the tissue at the observation site, thereby causing light to be birefringent. Therefore, if the polarization component is detected,
Tissue information (metabolism information, etc.) about the observation site can be obtained without other influences. That is, the interaction between light and ultrasonic waves can be detected with high fidelity and high accuracy. According to experiments performed by the present inventors, it has been confirmed that information on an observation site can be acquired with better accuracy than the conventional method. As described above, the present invention realizes local labeling in a light scattering medium when measuring light.

The ultrasonic wave irradiating means may be one having a single vibrator or an array vibrator, and for example, may be combined with an acoustic lens or an electronic focus. The light receiving means may be provided on an extension of the light beam axis, but is not limited thereto. That is, since light scattering occurs in the light scattering medium, the light receiving means can be arranged at a desired position.

The present invention is preferably applied to two-dimensional imaging, three-dimensional imaging in a living body, and measurement of a specific part in a living body. However, the present invention is also applicable to optical CT, blood flow analysis, and the like. It is. In this case, each of the ultrasonic wave irradiating means, the light irradiating means, and the light receiving means may be arranged outside the body, but a part or all of them may be arranged inside the body. Further, the present invention is not limited to living organisms, and various applications can be considered.

(2) Preferably, the light receiving means receives a light component having a second polarization angle that is orthogonal to the first polarization angle. In this case, for example, a pair of polarizers that are orthogonal to each other are used.

Preferably, the light irradiating means includes a laser light source, and a first polarizer that transmits only light having the first polarization angle out of the light from the laser light source.
A laser light source capable of emitting near-infrared light can be used.

Preferably, the light receiving means includes a second polarizer for passing only a light component having the second polarization angle out of the light emitted from the light scattering medium, and a light passing through the second polarizer. A light detector for receiving the light component. Here, the angle of the second polarizer is set to an angle different from that of the first polarizer by 90 degrees when it is arranged on the light beam axis. On the other hand, when the second polarizer is arranged other than on the light beam axis, the angle may be an angle rotated by 90 degrees from the angle at which the amount of received light is maximized without irradiating ultrasonic waves.

Preferably, an ultrasonic modulating means for modulating the ultrasonic wave transmitted by the ultrasonic irradiating means,
Detecting means for detecting an output signal from the light receiving means. As the detection means, for example, a known lock-in amplifier or the like may be used.

(3) An optical measurement probe according to the present invention
Light irradiation means for irradiating the light scattering medium with a light beam,
Ultrasound irradiating means for irradiating an ultrasonic beam to an observation site in the light scattering medium, and receives a light component affected by the ultrasonic wave in scattered light emitted from the light scattering medium. And a light receiving means for outputting a light receiving signal.

(4) An optical measurement probe according to the present invention
A light irradiating means for irradiating a light beam having a first polarization angle to the light scattering medium; an ultrasonic irradiating means for irradiating an ultrasonic beam to an observation portion in the light scattering medium; And a light receiving means for receiving a light component polarized under the action of the ultrasonic wave in the scattered light emitted from the medium and outputting a light reception signal.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of an optical measuring device according to the present invention, and FIG. 1 is a conceptual diagram showing the entire configuration. In the present embodiment, the optical measurement device is used for measurement of a living tissue (for example, measurement of a light absorption coefficient or blood oxygen concentration).

In FIG. 1, a light scattering medium 10 is a medium having a property of scattering near-infrared rays, and in this example, is a living tissue. In FIG. 1, a light irradiation unit 12 is provided on one side of the light scattering medium 10, and a light receiving unit 14 is provided on the other side. However, the light receiving section 14 does not necessarily have to be provided on the light beam axis. As will be described later, there is a degree of freedom in the arrangement of the light receiving unit 14 as long as the polarization action by the ultrasonic wave can be detected.

In this embodiment, the light irradiation unit 12
A laser device 20 that emits laser light 100 as near-infrared light, a polarizer 18 that allows a component of a predetermined polarization angle (for example, +45 degrees) of the laser light 100 emitted from the laser device 20 to pass therethrough, It consists of. Therefore, the laser beam 100 from the laser device 20 passes through the polarizer 18 and the laser beam 102 as a passing component thereof.
Is irradiated on the light scattering medium 10. In the light scattering medium 10, the laser light 102 is multiple-scattered, and a part of the laser light 102 passes through an ultrasonic beam B, which will be described later, and proceeds to the light receiving unit 14 side.

In this embodiment, the light receiving section 14 has a photodetector 24 for detecting a laser beam and a predetermined polarization angle (for example, -45 degrees) in the light 104 emitted from the light scattering medium.
And a polarizer 22 that transmits a light component having Since the polarizer 18 and the polarizer 22 have an orthogonal relationship, if the laser light is not polarized in the light scattering medium 10, the laser light does not reach the photodetector 24. On the other hand, when the laser beam is polarized by the birefringence phenomenon of the ultrasonic beam B described later, only the polarized component is extracted by the polarizer 22, and the component is received by the photodetector 24. The photodetector 24 is, for example, a photodiode, a photomultiplier, or the like.

Incidentally, because of the scattering of the laser light in the light scattering medium 10, as described above, the detection of the scattered light from the light scattering medium 10 is possible even on a position other than the light beam axis. That is, the arrangement position of the light receiving unit 14 is not limited to the position on the light beam axis. For example, according to the shape of the light scattering medium 10,
It is desirable to arrange at a position where the maximum amount of received light can be secured. In that case, the angle of the polarizer 22 is appropriately set so that only the polarized component by the ultrasonic wave is extracted.

An ultrasonic transducer 16 for irradiating an ultrasonic wave in a direction (Z direction) orthogonal to the light beam direction (X direction) in the drawing is joined to the light scattering medium 10. In this example, the ultrasonic beam and the light beam are orthogonal to each other, but it is sufficient if at least both cross or the ultrasonic beam passes through the light scattering region. The ultrasonic transducer 16 is a single transducer or an array transducer. It is desirable to provide an acoustic lens for acoustic focusing in the ultrasonic vibrator 16, and it is desirable to apply electronic focusing in the case of an array vibrator. It is desirable that the ultrasonic beam B is set so as to pass through the observation site T, and is formed so as to be focused at the observation site T.

In this embodiment, for example, ultrasonic waves of 5 MHz are pulse-modulated at a repetition period of 200 Hz, and ultrasonic pulses are applied intermittently. The pulse width is, for example, 1 μs. Lock-in amplifier 3 described later
In No. 2, synchronous detection is performed at 5 MHz. In such a situation where the ultrasonic pulse (PW) is intermittently radiated, the laser light is irradiated as described above, and the polarization component due to the ultrasonic wave is detected. Incidentally, as the transmitted ultrasonic wave, a continuous wave (CW), a continuous wave by frequency modulation (FMCW), and the like are also conceivable.

When the propagation velocities of the light and the ultrasonic wave are compared, it can be considered that the ultrasonic wave has stopped for the light. Therefore, if the timing from the transmission timing of the ultrasonic wave to the optical measurement is adjusted, it is possible to control the depth of the observation site T. For example, if light measurement is performed at fixed time intervals from the transmission timing of ultrasonic waves, sampling can be performed continuously in the depth direction. in this case,
In order to enhance the resolution in the depth direction, transmission focus of ultrasonic waves and the like are important. When optical measurement is performed intermittently,
The operations of the light irradiating unit 12 and the light receiving unit 14 may be controlled simultaneously, or the control may be performed so that only the light receiving unit 14 is operated intermittently. Alternatively, a shutter or the like can be provided on the optical path.

The controller 26 controls the operation of each component on the apparatus and controls the timing of each operation. The modulation signal generator 28 generates a pulse signal for modulating the ultrasonic wave and sends it to the transmitter 30. The transmitter 30 is a circuit that outputs a drive signal for exciting the ultrasonic vibrator 16, and outputs a 5 MHz drive signal that is pulse-modulated as described above. Of course, when the ultrasonic transducer 16 is formed of an array transducer, the transmitter 3
In 0, a delay device is provided for each vibration element, and electronic delay control of the drive signal is performed. Note that a reference signal is sent from the transmitter 30 to the lock-in amplifier 32.

In the photodetector 24, as described above, the polarization component due to the ultrasonic wave is detected, and the detection signal is sent to the lock-in amplifier 32, where amplification synchronized with the reference signal is executed. This is to detect only the intended polarization component while eliminating noise. Note that the target signal may be extracted using another synchronous detection method.

The signal processing unit 34 is provided with the lock-in amplifier 32
Based on the signal output from, for example, calculation of an absorption coefficient (reflection / absorption coefficient) at an observation site and various calculations based on the calculation are performed. When the absorption coefficient is obtained two-dimensionally, it may be expressed as a two-dimensional image. The processing result by the signal processing unit 34 is sent to the display unit 36.

FIG. 2 shows a scanning plane S as an area in which the observation site T can be set. As described above, when performing optical measurement of the observation site T, the direction of the ultrasonic beam B is set so as to pass over the observation site T, and a transmission focus point is set at the observation site T. If the observation site T is moved two-dimensionally, light measurement can be performed over the entire scanning surface S. The scanning surface S is formed by mechanical sector scanning, electronic sector scanning, or the like.

In the embodiment shown in FIG. 1, the locality is lost in the light scattering medium but metabolic information can be measured (near infrared ray), and the ultrasonic wave having locality in the light scattering medium. The local light measurement can be realized by utilizing the interaction between light and ultrasonic waves, specifically, the polarization due to birefringence. That is, according to the optical measurement device of the present embodiment, labeling of the observation site by the ultrasonic wave can be realized.

Since the polarized light is used, the light receiving section 14
There are various advantages, such as no limitation on the light receiving area, no need for delicate setting of the optical path length, and no need for complicated calculations. In addition, high-precision measurement can be performed easily and easily,
The apparatus cost can be reduced, and meaningful information for tissue diagnosis can be provided.

The present apparatus can be combined with an ultrasonic diagnostic apparatus. For example, an optical measurement result (two-dimensional absorption coefficient image) may be displayed in combination with a known B-mode image (two-dimensional tomographic image). In this case, the latter can be colored.

Next, a probe used in the optical measurement device of the present embodiment will be described.

FIG. 3 shows an example of the composite probe. The composite probe 204 is used, for example, in contact with the neck of a living body, and is a probe for analyzing blood in the carotid artery 202, for example. The light irradiating section 12 and the light receiving section 14 described above are provided in the casing of the probe 204, and the ultrasonic transducer 16 is further provided therebetween. The ultrasonic vibrator 16 emits ultrasonic waves along the central axis of the probe, and the directivity directions of the light irradiation unit 12 and the light receiving unit 14 are set so as to intersect the central axis. According to such a composite probe 204, there is an advantage that desired measurement can be performed only by bringing the probe into contact with the living body, similarly to the conventional ultrasonic diagnosis.

FIG. 3 shows a composite probe 2 used outside the body.
While FIG. 4 is shown, FIG. 4 shows a composite probe 212 for use in the body. This composite probe 2
12 is to be inserted into a blood vessel or lumen,
A light irradiating section 12 and a light receiving section 14 are provided in the distal end portion thereof, and an ultrasonic transducer 16 is provided therebetween. According to such a probe 212, for example, the esophagus 2
For example, analysis of the adjacent organ 214 can be performed via the apparatus 10.

FIG. 5 shows still another embodiment. In this embodiment, the measurement probe is roughly composed of an ultrasonic probe 224 and an optical probe 222. The optical probe 222 is inserted into a blood vessel of the living body 220, for example, and transmits and receives light inside the blood vessel. On the other hand, the ultrasonic probe 224 is used in contact with the body surface, and the probe 224 emits ultrasonic waves. Of course, it is also possible to provide an ultrasonic transducer for the probe inserted into the blood vessel. Further, in the optical probe 222 shown in FIG. 5, both the light irradiating section 12 and the light receiving section 14 may be provided on the distal end surface to analyze blood in front of the probe. Further, while transmitting ultrasonic waves inside the body, transmission and reception of light outside the body may be performed.

In the above embodiment, an apparatus for measuring a living body has been described. However, the present invention can be applied to measurement of an object other than a living body.

[0038]

As described above, according to the present invention,
In measuring a light scattering medium, the interaction between ultrasonic waves and light can be measured with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram illustrating a scanning plane.

FIG. 3 is a diagram showing an example of a composite probe.

FIG. 4 is a diagram showing another example of a composite probe.

FIG. 5 is a diagram showing an ultrasonic probe and an optical probe.

[Explanation of symbols]

10 light scattering medium, 12 light irradiation part, 14 light receiving part, 1
6. Ultrasonic transducer, 18 polarizer, 20 laser device, 22 polarizer, 24 photodetector, 26 controller, 28 modulation signal generator, 30 transmitter, 32 lock-in amplifier, 34 signal processing unit, 36 display unit.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshiyuki Matsunaka 6-22-1, Mure, Mitaka-shi, Tokyo Aloka F-term (reference) 2G059 AA05 AA06 AA10 BB12 EE04 EE05 FF01 GG01 GG04 HH01 HH02 JJ19 KK01 LL04 MM01 MM08 MM09 NN01 4C301 BB02 CC01 DD01 DD06 DD11 EE04 EE11 EE12 EE17 FF01 GB02 GB27 HH01 HH21 HH31 JB02 JB21 LL20

Claims (7)

[Claims] 1. A light irradiating means for irradiating a light beam having a first polarization angle to a light scattering medium, and an ultrasonic irradiating means for irradiating an ultrasonic beam to an observation site in the light scattering medium. And a light receiving unit that receives a light component polarized under the action of the ultrasonic wave in the scattered light emitted from the light scattering medium and outputs a light reception signal. . 2. The apparatus according to claim 1, wherein said light receiving means has a second polarization angle orthogonal to said first polarization angle.
An optical measurement device for receiving a light component having a polarization angle. 3. The apparatus according to claim 1, wherein the light irradiating means includes: a laser light source; and a first polarizer that transmits only light having the first polarization angle out of light from the laser light source. An optical measurement device, comprising: 4. The device according to claim 2, wherein the light receiving means includes: a second polarizer that allows only a light component having the second polarization angle to pass therethrough in light emitted from the light scattering medium; A light detector that receives a light component that has passed through the second polarizer. 5. The apparatus according to claim 1, wherein: an ultrasonic modulator for modulating an ultrasonic wave transmitted by the ultrasonic irradiator; a detector for detecting an output signal from the light receiver; An optical measurement device comprising: 6. A light irradiating means for irradiating a light beam to a light scattering medium; an ultrasonic wave irradiating means for irradiating an ultrasonic beam to an observation portion in the light scattering medium; A light measuring probe, comprising: light receiving means for receiving a light component affected by the ultrasonic wave in the emitted scattered light and outputting a light receiving signal. 7. A light irradiating unit for irradiating a light beam having a first polarization angle to a light scattering medium, and an ultrasonic irradiating unit for irradiating an ultrasonic beam to an observation site in the light scattering medium. And a light receiving means for receiving, in the scattered light emitted from the light scattering medium, a light component polarized under the action of the ultrasonic wave and outputting a received light signal, probe.