JPH07100119A - Blood flow distribution measuring instrument - Google Patents

Abstract

PURPOSE:To provide a blood flow distribution measuring instrument capable of taking high-precision two-dimensional measurement of blood flow in less time. CONSTITUTION:When scanning is carried out via a deflection mirror 6 for common use with beams of light from both a irradiation system and a light- receptor system, scanning along one of two axes is electrically performed by slecting the outputs from respective elements of a photodiode array 11 so placed as to function in harmony with the surface of a living body. A laser light beam outputted by a laser light source 1 is converted into sheet light by a cylindrical lens 2 and falls, via a lens 4, upon a mirror 5 positioned along the optical axis of the light-receptor system at the focus of the lens 4 to be reflected toward the deflection mirror 6. As scanning is performed along one axis instead of two-dimensional scanning by selecting the outputs from respective elements of the photodiode array 11 independently, the instrument is capable of taking a measurement in less time, yet equivalent in accuracy to the measurement taken by an instrument so structured as to perform two-dimensional scanning with a laser beam repeating the acquisition of data on blood flow on the basis of laser radiation toward and reflected light received at one point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood flow distribution measuring device, and more particularly to a blood flow distribution measuring device for irradiating a living body with laser light and receiving reflected light to measure blood flow.

[0002]

2. Description of the Related Art Currently, there are two methods for measuring skin blood flow, such as hydrogen clearance measurement and laser blood flow measurement, which are used for measuring microcirculatory dynamics in areas such as plastic surgery and dermatology. Has been done. Among them, the laser blood flow meter irradiates the skin with laser light and receives scattered light from red blood cells circulating in the skin with an optical system such as a fiber system, and converts the scattered light intensity into an electric signal with a light receiving element. Moreover, the blood flow velocity and the blood flow rate of the skin are measured from the magnitude of this scattered light intensity and the time variation, and there is a feature that the measurement can be performed non-invasively.

From the viewpoint of the structure, such a laser blood flow meter can be roughly classified into a structure for performing one-point measurement and a structure for performing two-dimensional measurement. In the one-point measuring device, the laser light from the laser light source is guided to the measurement site by the optical fiber, and the scattered light from the living body is also guided to the light receiving element by the optical fiber and photoelectrically converted. Blood flow is a value that consists of the speed and volume of blood flowing through the measurement unit. With such a laser blood flow meter, the frequency and magnitude of the scattered light intensity from the living body is analyzed to determine the high intensity in the frequency region of the scattered light intensity. The blood flow velocity is obtained from the extent of spread to the region, the value corresponding to the blood volume is obtained from the signal magnitude, and the value corresponding to the blood flow is obtained from the product of the two. This configuration is based on the concept that blood flow information is to be derived from the entire frequency band of the scattered light intensity measured from the living body from low frequency to high frequency.

[0004]

On the other hand, a configuration as shown in FIG. 4 is known as an apparatus for obtaining a two-dimensional blood flow distribution in a non-contact manner. In FIG. 4, reference numeral 47 is a perforated mirror, a laser beam 49 from a laser light source 48 passes through a hole 50 of the perforated mirror 47, and a deflection mirror 52 is rotated in a direction of an arrow 54 or 55 via a lens 51. Then, a position on the living body surface 53 is selected and irradiation is performed.

Then, the scattered light from the measurement point is imaged on the light receiving element 57 from the deflection mirror 52 through the lenses 51 and 56.

In the light receiving element 57, the scattered light intensity is photoelectrically converted, and only the AC signal having the blood flow information is amplified and then frequency analyzed to obtain the blood flow information at the measurement point. The scattered light is measured while the deflection mirror 52 is stopped. By repeating these measurement points in the process of moving, stopping and measuring in a grid pattern, the planar distribution of blood flow can be measured.

According to this method, the scattered light intensity is measured stationary at each measurement point, so that the scattered light intensity of the entire frequency band from the living body can be measured. Therefore, the blood flow velocity and the blood volume can be obtained, and the two-dimensional distribution of the blood flow can be displayed, as in the conventional laser blood flow meter for one point.

However, in the method of two-dimensionally scanning the position of the irradiation light by the mechanical means such as the deflecting mirror 52, an unnecessary measurement waiting time is required for the following two measurements. The first is the problem of the moment of inertia of the deflecting mirror 52. When the irradiation light is moved from the previous measurement point to the next measurement point and stopped, vibration occurs due to the moment of inertia of the mirror, and it takes time to completely stop. On the other hand, while the scattered light is being received, measurement cannot be performed unless the mirror is stationary, so that the deflection mirror 5 is used for each measurement point.
2 requires a waiting time until it completely comes to rest.

Now, in order to show the importance of this waiting time,
Comparing the measurement time and the waiting time, in the case of a galvano scanner mirror often used as a deflection mirror,
It is known that the time at which the vibration at the time of stop is attenuated and settled is about several ms, and this time is set to 5 ms.

The time required to measure one point is such that the frequency band of scattered light intensity with blood flow information from the living body is several hundreds H.
z or more, and when it is 500 Hz or more, it becomes about 2 ms. If the measurement frequency band is further expanded to a lower frequency band, the time required for this measurement becomes longer. Therefore, the measurement time at one point is the waiting time and the total measurement time, which is 7 ms. That is, 5/7 of the measurement time is a completely useless time for acquisition of blood flow information.

The second problem is that electrical vibration occurs at the stage of AC amplification required after the scattered light from the living body is converted into an electric signal by the photoelectric conversion element. That is, by an electrical high-pass filter when performing AC amplification,
That is, the fluctuation of the light amount when the irradiation light moves from the measurement point to the measurement point appears as a differential waveform. The time to wait for this signal to decay and settle may be an unnecessary loss time for measurement. When this time is added to the previous estimation of the measurement time, the measurement becomes further inefficient in terms of time.

In addition, as a two-dimensional measuring device, Japanese Patent Publication No.
There is a blood flow device as described in No. 28133 that measures blood flow at multiple measurement points without contact. Fig. 5
The apparatus described in 28133 is shown. In FIG. 5, a laser beam 40 from a light source (not shown) becomes a sheet light flux by a cylindrical lens 41, and is irradiated onto a living body surface 43 via a deflection mirror 42. Lens 4 for scattered light from living organisms
4 forms an image, and the scattered light is received by the light receiving element array 45 having the pixel arrangement direction in the same direction as the longitudinal direction of the sheet light.

Then, the scattered light intensity signal at time t is measured at each pixel, and the result is compared with the signal intensity at time t + Δt, and the change in this signal is taken as a value corresponding to the activity of blood flow. Is displayed as a blood flow distribution corresponding to the irradiation site.

In this state, since the measurement is performed on one line, in order to measure the distribution on the plane, the deflection mirror 42 is rotated as indicated by an arrow 46 instead of moving the measurement target, and the sheet light is measured in the longitudinal direction. Move the measuring line in the vertical direction. With this device, since the value corresponding to the blood flow at each point can be easily obtained, the number of pixels constituting one blood flow distribution screen can be increased accordingly.
In this configuration, as the light receiving element, an element that has a large number of pixels, such as a CCD element, but can output an output signal in a time-division manner without continuous output can be used. Blood flow images can be measured.

The device described in Japanese Patent Publication No. 5-28133 handles a huge amount of two-dimensional information as compared with one-point measurement, so that blood flow information at each pixel, that is, at each measurement point can be easily acquired. Is being considered.

In Japanese Examined Patent Publication No. 5-28133, scattered light is measured twice before and after at each measuring point at a fixed time interval, and the blood at the measuring point is determined from the magnitude of the change in the two measured values. I want the "activity" of the flow.

By the method of acquiring the change in the measured value twice as described above, the burden on the analysis unit is remarkably reduced, so that the distribution of the blood flow state having a large number of pixels can be displayed.

However, this method is different from the above-described one-point measuring device or the device shown in FIG.
It is based on the concept of measuring the blood flow state from only some frequency components, and therefore the output is a two-dimensional distribution of the values expressed as the "activity" of the blood flow. It should be understood that, unlike the blood flow equivalent value output by the above-mentioned one-point measurement device or the device of FIG. 4 based on this, a simple measurement value is output instead of a precise measurement value. The measurement results must be evaluated at.

An object of the present invention is to realize a measurement in a shorter time in a device for accurately measuring a blood flow two-dimensionally, as in the configuration of repeating one-point measurement as shown in FIG. However, the blood flow distribution is measured while eliminating unnecessary time due to the moment of inertia of the deflecting mirror.

As a method of shortening the vibration time of the deflecting mirror due to this moment of inertia, it is conceivable to reduce the moment of inertia of the deflecting mirror. However, in the present invention, the use of the deflecting mirror itself makes scanning of at least one axis. A configuration that fundamentally deals with it by making it unnecessary is adopted.

[0021]

In order to solve the above-mentioned problems, in the present invention, an irradiation means for expanding a laser beam to irradiate the surface of a living body to be measured, and an image conjugate to the irradiation surface of this irradiation means. A light receiving optical system configured to form an image of a point on a light receiving surface and sharing at least a part of optical elements of the optical system of the irradiating means, and the irradiation light axis and the light receiving optical axis in common to the living body surface. A unit for scanning about one axis above, a light receiving element array in which a plurality of light receiving elements are arranged on the light receiving surface, that is, an image surface conjugate with the irradiation surface, and signals of each light receiving element array are AC amplified. Means, means for independently selecting an output signal from the means for amplifying each of the alternating currents, and analysis means for measuring blood flow information at multiple points of the living body based on the time series signals of the selected light receiving element output signals The following configuration was adopted.

[0022]

According to the above construction, at least one axis of the two-dimensional scanning can be electrically performed by selecting the output signal of each element of the light receiving element array, so that the measurement time can be shortened. it can.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings.

In the present invention, instead of using a biaxial deflection mirror in the configuration of FIG. 4, a light receiving element array is installed at a position conjugate with the measurement surface, and at least a uniaxial deflection mirror is used for two-dimensional scanning. Do.

At this time, similarly to the apparatus of FIG. 5, the luminous flux of the irradiation light is a sheet luminous flux or a surface luminous flux, and the movement of the measuring point is performed by sequentially designating the elements in the light receiving element array for obtaining the measurement signal. However, as will be described later, unlike the device of FIG. 5, a light receiving element array for photoelectrically converting scattered light from a living body is placed at a position optically conjugate with the measurement target. If it is not used, the above-mentioned selection of the light receiving element cannot be established.

Further, unlike the configuration using the CCD shown in FIG. 5, the signals from the respective light receiving elements are amplified in parallel by an independent signal processing system so that the output of the desired element can be selected at a desired timing. .

With such a structure, unlike the idea of mechanically moving the irradiation light as shown in FIG. 4, attention is paid by electrically switching pixel signals from each element of the light receiving element array. The signal of the element is selected and the two-dimensional distribution is measured. The scattered light intensity of the entire frequency band from the living body at each measurement point can be measured, and the measurement time is wasted by mechanically moving the irradiation light. Can be resolved.

In the present apparatus, the object is irradiated with the spread laser light and the scattered light from the living body is measured by the light receiving element consisting of a plurality of pixels. The signals from each light receiving element can be amplified and processed independently, A signal at a specific position can be taken out and analyzed by designating an element for taking out. Further, it is also possible to measure the scattered light intensity from the light receiving element array in parallel, and the measurement can be performed in a shorter time.

FIG. 1 and FIG. 2 show a concrete structure. The laser light from the laser light source 1 is converted into the sheet light flux 3 by the lens 2. Then, it is once condensed by the lens 4 and reflected by the mirror 5. Since the mirror 5 is located at the converging point of the sheet light beam 3, the light beam reflected by the mirror 5 becomes the sheet light beam again.

Then, the light flux 3 is changed in direction by the deflecting mirror 6 as it spreads, and then the lens 7 having the focal point of the lens 4 as a focal point forms a sheet-like parallel light and irradiates the living body surface 8. .

The scattered light 9 from the living body is condensed by the lens 7 into parallel light, reflected by the deflecting mirror 6, passes through the imaging lens 10, and is imaged on the photodiode array 11.

This photodiode array 11 has a CC
Unlike D, the plurality of photodiodes 13a to 13c
(Fig. 2) are arranged on a line.

Further, unlike the configuration of FIG. 5, the light receiving surface 12 on the photodiode array and the living body surface 8 are optically conjugated by the lens 7 and the lens 10.

The lens 7 also exists as a component of the irradiation optical system, and the lens 7 is a collimator as the irradiation optical system. Photodiode array 11
Is installed so that the direction in which the photodiodes 13a to 13c are arranged in one line is the same as the longitudinal direction of the sheet light flux 3.

FIG. 2 shows a signal processing system, and each of the photodiodes 13a to 1a of the photodiode array 11 is shown.
The photocurrent signal photoelectrically converted for each 3c is a current-voltage conversion circuit 14a, which is provided independently for each photodiode.
After being converted into a voltage by 14c, the AC amplifiers 15a-
After being amplified by c, it is switched by the analog multiplexer 16 so that the signal for each measurement point can be selected. The low-frequency cutoff frequency of the AC amplifiers 15a to 15c is about 100 Hz, and has the purpose of removing a DC signal other than blood flow information from the living body, for example, a DC component due to direct return light from the skin surface. Here, it is important that the AC amplifiers 15a to 15c are provided after the photodiodes 13a to 13c of the photodiode array 11, not after the analog multiplexer 16.

In the actual blood flow distribution measurement, there may be a case where the scattering characteristics are remarkably different in the measurement range plane. For example, when measuring the tip of a hand, the scattered light from a ring attached to the finger returns a stronger return light than the scattered light from the skin, and between the fingers, the table with the hand placed. The return light from is received, but if the table has a low reflectance,
Almost no light returns. As described above, when the DC signal from the photodiode in a certain area is stronger or, conversely, weaker than the adjacent photodiode, if an AC amplifier is provided in the subsequent stage of the analog multiplexer, the difference between the DC signals of the photodiodes 13a to 13c is increased. May be input as a step-like signal to the AC amplifier, and a differential waveform may appear from the output of the AC amplifier. However, in the configuration of FIG. It is not affected by the extreme level difference of signals.

The scattered light intensity signal selected by the analog multiplexer 16 is converted into a digital value by the AD converter 17, and then the power spectrum is obtained by the FFT circuit 18.
From the power spectrum, the microcomputer 19 calculates the blood flow volume corresponding to the photodiode 13a.

One line is measured by sequentially selecting the photodiodes 13a to 13c by the analog multiplexer 16. By the above method, in the measurement of one line, unnecessary waiting time other than the measurement is unnecessary, and the measurement can be performed in a short time.

When expanding this two-dimensionally, the deflection mirror 6 is rotated to move the measurement point in the direction perpendicular to the longitudinal direction of the sheet light beam 3. Here, it is sufficient that the deflecting mirror used can be used for the purpose of merely moving the measurement position as in the prior art shown in FIG. 5, and the vibration damping time in FIG. It is not necessary to use an expensive thing such as the deflection mirror 52.

Here, the number of measurement points in this embodiment is 32 × 3.
Estimate the measurement time when there are two points. The measurement time at each measurement point is set to 2 ms as in the case of the prior art. In reality, the analog multiplexer 16 also has time until the switching is completed, but this is a unit of several μs and is a negligible value.

When the time until the deflection mirror 6 is completely stopped is 5 ms described in the section of the prior art, the total measurement time is (2 ms × 32 + 5 ms) × 32 = 2.2 s. Now, the total measurement time in the configuration of FIG. 4 for performing the measurement equivalent to the present invention is (2 ms + 5 ms) × 32 × 32 = 7
Therefore, in the present invention, the measurement time is about 1/3.

As a method of shortening the time, although not shown, the signals from two elements of the photodiode array are simultaneously analyzed by a multiplexer and an A / D converter arranged in parallel, and By arranging the diode arrays in two steps above and below and expanding the irradiation sheet light flux so that two steps are irradiated, and analyzing at the same time, it is further halved.
It is also possible to shorten the time.

As described above, wasteful time due to the moment of inertia of the deflecting mirror can be eliminated, and the blood flow distribution can be precisely two-dimensionally measured in a shorter time.

The basic embodiment has been described above. Next,
Further, an example in which safety is taken into consideration will be shown. In the present invention, the spread laser light is emitted, and the scattered light intensity from the living body is received by the light receiving element array including a plurality of light receiving elements. Then, the scattered light intensity signal from each light receiving element is electrically switched to select a measurement point.

In this configuration, while one of the pixels is electrically selected, the laser light is also applied to the measurement points corresponding to the other pixels. Is irradiated, and the irradiation energy of the laser light irradiated during that time does not contribute to the measurement. When irradiating a living body with a laser beam, from the viewpoint of safety, it is desirable that the energy of the laser beam with which the living body is irradiated be small.

FIG. 3 is constructed so as to reduce the energy of the laser beam applied to the living body, and here, the measurement of one line is shown. The light flux 21 from the laser light source 20 is converted into a sheet light flux by the lens 22. Next, the light is condensed by the lens 23, and is totally reflected by the prism 24 in the middle thereof to change the direction by 90 degrees, and the mirror 25 further changes the direction by 90 degrees.

Next, the measurement area 28 on the surface 27 of the living body is irradiated with a sheet through the lens 26. The light flux 33 from the other laser light source 32 becomes a sheet light flux by the lens 34. Next, the light is condensed by the lens 35, and the prism 2
The light is totally reflected at 4 and changes its direction by 90 degrees, and the mirror 25 further changes its direction by 90 degrees.

Next, the measurement area 36 on the surface 27 of the living body is irradiated with light through the lens 26. The scattered light 29 from the living body is photoelectrically converted by the photodiode array 31 at the image forming position via the lens 26 and the lens 30.

The signal from the photodiode array 31 is analyzed by a current-voltage conversion circuit, an AC amplifier, an analog multiplexer, an FFT circuit (not shown) and the microcomputer 37 in the same manner as in the above-described embodiment of FIG. The blood flow in the measurement area 28 is measured, and while the measurement point corresponding to the range of the measurement area 28 is being measured, the microcomputer 37
Under the control of, the drive circuit 38 drives only the light source 20 and only the light source 32 outputs the laser beam 33 by the drive circuit 39 while the measurement area 36 is being measured.

With such a configuration, the irradiation time at each measurement point in one measurement of one line is half that in the case of irradiating the whole body with one light flux, and the irradiation energy to the living body can be kept low. You can

[0051]

As is apparent from the above, according to the present invention, the irradiation means for expanding the laser beam to irradiate the surface of the living body to be measured, and the image of the image point conjugate to the irradiation surface of the irradiation means are received. A light-receiving optical system configured to form an image on a surface and sharing at least a part of optical elements of the optical system of the irradiation means, and the irradiation optical axis and the received optical axis are common and one axis is formed on the surface of the living body. A means for scanning as a center, the light receiving surface, that is, a light receiving element array in which a plurality of light receiving elements are arranged on an image plane conjugate to the irradiation surface, a means for AC-amplifying a signal of each light receiving element array, and Adopting a structure comprising means for independently selecting an output signal from each means for amplifying alternating current, and analysis means for measuring blood flow information of a large number of points of the living body based on the time-series signals of the selected light receiving element output signals. Therefore, the number of two-dimensional scanning is small. Since at least one axis can be electrically performed by selecting the output signal of each element of the light receiving element array, the measurement time can be remarkably shortened, and the blood flow distribution can be precisely two-dimensionally measured. An excellent blood flow measurement device can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an optical system of a blood flow distribution measuring device adopting the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a measurement circuit of a blood flow distribution measuring device adopting the present invention.

FIG. 3 is an explanatory diagram showing a different configuration of a blood flow distribution measuring device adopting the present invention.

FIG. 4 is an explanatory diagram showing a configuration of a conventional two-dimensional blood flow measuring device.

FIG. 5 is an explanatory diagram showing a different configuration of a conventional two-dimensional blood flow measuring device.

[Explanation of symbols]

1, 48, 20, 32, 32 Laser light source 2, 4, 7, 10, 22, 23, 26, 30, 34 Lens 35, 44, 44, 44, 51, 56 Lens 3, 3, 21 Sheet light flux 5, 25 mirror 6, 42, 52 deflection mirror 8, 27, 43, 53 living body surface 9, 29 scattered light 11, 31 photodiode array 12 light-receiving surface 13a-13c photodiode 16 analog multiplexer 18 FFT circuit 19, 37 microcomputer 24 prism 33 laser beam 36 measurement area 38, 39 drive circuit 40 laser beam 41 cylindrical lens 45 light receiving element array 47 perforated mirror 49 laser beam 57 light receiving element

Claims (4)

[Claims] 1. An irradiation means for expanding a laser beam to irradiate the surface of a living body to be measured, and an image of an image point conjugate to the irradiation surface of the irradiation means are formed on the light receiving surface, and at least the above-mentioned. A light receiving optical system that shares some of the optical elements of the optical system of the irradiation means, a means that scans the irradiation optical axis and the received optical axis in common on the living body surface around one axis, and the light receiving surface, that is, A light-receiving element array in which a plurality of light-receiving elements are arranged on an image plane conjugate with the irradiation surface, a means for AC-amplifying the signal of each light-receiving element row, and an output signal independently from the AC-amplifying means A blood flow distribution measuring device comprising: a selecting unit; and an analyzing unit that measures blood flow information of a large number of points of a living body based on a time-series signal of the selected light receiving element output signal. 2. The blood flow distribution measuring device according to claim 1, wherein the direction of spread of the irradiation laser light on the irradiation surface is the same as the direction of arrangement of the light receiving element arrays. 3. The light receiving optical system is configured by a coaxial spherical optical system including two optical elements, and an optical element of the two optical elements that is shared with the optical system of the irradiation means emits the irradiation light. The blood flow distribution measuring device according to claim 1, which emits as a parallel light flux. 4. The luminous flux of the irradiating laser light is set to plural, and the luminous flux of the irradiating laser light is selected so that at least the subject surface corresponding to the light receiving element selected by the signal selecting means is selectively irradiated, and the living body surface is selected. The blood flow distribution measuring device according to claim 1, wherein the total irradiation energy to the blood is reduced.