JP6614608B2 - Fluid evaluation apparatus and method, computer program, and recording medium - Google Patents

Description

  The present invention relates to a fluid evaluation apparatus and method, a computer program, and a computer program for evaluating the fluid based on a signal obtained by receiving light irradiated to a fluid such as blood flowing inside the measurement object. The present invention relates to the technical field of recording media for storing computer programs.

  As an apparatus of this type, for example, an apparatus has been proposed in which an LED (Light Emitting Diode) and a light receiving element are arranged around a medical tube, and hematocrit of blood flowing in the medical tube is measured from a light reception signal ( Patent Document 1). Alternatively, a device is proposed that irradiates a tube in which blood flows inside with a laser beam and corrects the blood flow calculated from the Doppler shift of the laser beam based on the blood concentration calculated from the amount of light received by the light receiving element. (See Patent Document 2).

  As prior art documents related to the present invention, there are Patent Document 3 and Patent Document 4. In Patent Document 3, blood flowing through a flow path having a width smaller than the blood cell diameter of red blood cells is photographed by a camera, and a hematocrit value of blood is obtained by performing image processing on the photographed image, and based on the hematocrit value. An apparatus for calculating the deformability of red blood cells by correcting the speed of red blood cells in the blood flowing through the flow path is disclosed. Patent Document 4 discloses an apparatus for calculating hematocrit from a dialysate flow rate, pump rotation speed, dialysate inlet / outlet concentration, blood flow rate, and the like related to a dialyzer in order to obtain hemodialysis parameters during treatment. .

International Publication No. 2004/057313 Pamphlet International Publication No. 2013/153664 Pamphlet International Publication No. 2010/137470 Pamphlet JP 10-314299 A

  The techniques described in Patent Documents 1 and 2 have a technical problem that there is room for improvement.

  The present invention has been made in view of the above problems, for example, and includes a fluid evaluation apparatus and method, a computer program, and a recording medium for storing the computer program that can suitably determine at least one of the flow rate and the flow velocity of the fluid. The issue is to provide.

In order to solve the above-described problems, the fluid evaluation apparatus of the present invention receives a light source that irradiates light to a measurement target in which a fluid flows inside, and scattered light from the measurement target of the irradiated light. A light receiving unit that outputs a light reception signal corresponding to the received scattered light, and a first information output unit that outputs light reception amount information that is information related to the light reception amount of the light reception unit included in the output light reception signal. And the relationship between the information included in the output light reception signal based on the beat signal due to the Doppler shift of the light, the output light reception amount information, and the information based on the light reception amount information and the beat signal. based on the correspondence information, the second information output section for outputting information regarding at least one of the flow rate of the flow rate and the fluid of the fluid, wherein the correspondence information, the received light amount information and the In the coordinate system having each axis based on the information based on the beat signal, each of the parameters corresponds to a plurality of parameters relating to the flow rate of the fluid or the flow velocity of the fluid, and the relationship between the received light amount information and the information based on the beat signal Are a plurality of relationship lines.

In order to solve the above problems, a fluid evaluation method of the present invention receives a light source that irradiates light to a measurement target in which a fluid flows inside, and scattered light from the measurement target of the irradiated light. A fluid evaluation method in a fluid evaluation apparatus comprising: a light receiving unit that outputs a light reception signal corresponding to the received scattered light, wherein the information regarding the amount of light received by the light receiving unit included in the output light reception signal A first information output step for outputting received light amount information, information based on a beat signal resulting from a Doppler shift of the light, included in the output received light signal, the output received light amount information, and the received light A second information output step of outputting information relating to at least one of the flow rate of the fluid and the flow velocity of the fluid based on correspondence information defining a relationship between quantity information and information based on the beat signal , Wherein the corresponding relationship information in said received light amount information and the coordinate system whose axes information respectively based on the beat signal, with each corresponding to a plurality of values of flow rate or a parameter related to the flow velocity of the fluid in the fluid , A plurality of relationship lines that define the relationship between the received light amount information and the information based on the beat signal.

In order to solve the above problems, a computer program of the present invention receives a light source that irradiates light to a measurement target in which a fluid flows inside, and scattered light from the measurement target of the irradiated light. A light receiving unit that outputs a light receiving signal corresponding to the received scattered light, and a computer mounted on the fluid evaluation device, the information regarding the amount of light received by the light receiving unit included in the output light receiving signal. A first information output unit that outputs received light amount information; information based on a beat signal caused by the Doppler shift of the light included in the output received light signal; the output received light amount information; and the received light amount information And second information output for outputting information on at least one of the flow rate of the fluid and the flow velocity of the fluid based on the correspondence information defining the relationship of information based on the beat signal. Parts, to function as the correspondence information, in the amount of light received information and coordinate system with axes information respectively based on the beat signal, corresponding respectively to a plurality of values of flow rate or a parameter related to the flow velocity of the fluid in the fluid And a plurality of relationship lines that define the relationship between the received light amount information and the information based on the beat signal.

  In order to solve the above problems, the recording medium of the present invention stores the computer program of the present invention.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a block diagram which shows the structure of the fluid evaluation apparatus which concerns on 1st Example. 4 is a circuit diagram illustrating an example of a light receiving element 21 and an IV conversion unit 22 according to the first embodiment. FIG. 4 is a circuit diagram illustrating an example of a light receiving element 31 and an IV conversion unit 32 according to the first embodiment. FIG. It is a figure which shows an example of the relationship between a hematocrit value and the amount of transmitted light. It is a conceptual diagram which shows an example of a frequency analysis. It is a conceptual diagram which shows an example of the calculation method of a primary moment and an average frequency. It is a figure which shows an example of the relationship between a frequency and a power spectrum. It is a figure which shows an example of the relationship between a flow velocity and a primary moment or an average frequency. It is an example of the actual value which measured the power spectrum of the beat signal which measured the velocity of the fluid with respect to a plurality of fluid concentrations. It is an example of the map data which shows the relationship between transmitted light amount and average frequency for every flow volume. It is a flowchart which shows the flow volume estimation process which concerns on 1st Example. (A) It is an example of the estimation result at the time of estimating a flow volume only from an average frequency. (B) It is an example of the estimation result at the time of estimating a flow volume from the transmitted light amount and average frequency. It is a conceptual diagram which shows the concept of the flow volume estimation which concerns on the 1st modification of 1st Example. It is a block diagram which shows the structure of the fluid evaluation apparatus which concerns on the 2nd modification of 1st Example. It is a block diagram which shows the structure of the fluid evaluation apparatus which concerns on the 3rd modification of 1st Example. It is an example of the map data which shows the relationship between transmitted light amount and average frequency for every hematocrit value. It is an example of the map data which shows the relationship between the transmitted light amount and the primary moment for every hematocrit value. It is a flowchart which shows the hematocrit estimation process which concerns on 2nd Example. (A) It is an example of the estimation result at the time of estimating a hematocrit value only from the transmitted light amount. (B) It is an example of the estimation result at the time of estimating a hematocrit value from the transmitted light amount and the average frequency.

  An embodiment of the fluid evaluation apparatus and the like of the present invention will be described.

(Fluid evaluation device)
The fluid evaluation apparatus according to the embodiment receives a light source that irradiates light to a measurement target in which a fluid flows inside, and scattered light from the measurement target of the irradiated light. A light receiving unit that outputs a corresponding light receiving signal, a first information output unit that outputs received light amount information that is information relating to a light receiving amount of the light receiving unit included in the output light receiving signal, and included in the output light receiving signal. Based on the information based on the beat signal resulting from the Doppler shift of light, the received light amount information, and the correspondence information that defines the relationship between the light amount information and the information based on the beat signal, the flow rate of the fluid and the flow rate of the fluid And a second information output unit that outputs information related to at least one.

  According to the fluid evaluation apparatus of the present embodiment, the light source irradiates the measurement target with light. A fluid flows inside the object to be measured. The light is preferably applied to the fluid.

  Examples of the measurement target and the fluid include living bodies such as humans and animals and blood. Alternatively, as another example of the measurement target and the fluid, an artificial conduit through which blood flows and blood can be cited. Alternatively, as another example of the measurement target and the fluid, a tube having a window through which light can pass and a transparent tube, and a fluid flowing in the tube or the tube (for example, ink, oil, sewage, seasoning, etc.) A fluid containing at least a scatterer that scatters light as a constituent element).

  The light receiving unit receives scattered light from an object to be measured. The light receiving unit may receive light transmitted through the object to be measured (so-called forward scattered light corresponding to transmitted light), or light reflected by the object to be measured (so-called back scattering corresponding to reflected light). Light) or both of them may be received. As a result, a light reception signal corresponding to the received light is output from the light receiving unit.

  For example, the first information output unit including a memory, a processor, and the like outputs received light amount information (for example, average signal intensity, signal intensity of DC (Direct Current) component included in the received signal, etc.) included in the received light signal. To do. The “light reception amount information” according to the present embodiment is not limited to information indicating the light reception amount itself, and may be any physical quantity or parameter related to the light reception amount.

  In addition, when the light receiving unit receives light transmitted through the object to be measured (that is, forward scattered light), the fluid has a higher concentration of the fluid (that is, more scatterers or the like that hinder light transmission are included in the fluid). The signal intensity of the received light signal becomes smaller. On the other hand, when the light receiving unit receives light reflected by the object to be measured (that is, backscattered light), the fluid has a higher concentration (that is, more scatterers that reflect the light are included in the fluid). The higher the signal intensity, the greater the received signal strength.

  For example, the second information output unit including a memory, a processor, and the like includes information based on the beat signal caused by the Doppler shift of light, information on the received light amount, and information based on the received light amount information and the beat signal. And information on at least one of the flow rate of the fluid and the flow velocity of the fluid is output based on the correspondence relationship information defining the relationship.

  When light is irradiated onto the measurement target, scattered light is generated due to the flow of fluid inside the measurement target. This scattered light includes scattered light scattered by scatterers contained in the fluid (especially moving scatterers), other fixed tissues (especially skin tissues, transparent tubes forming windows and channels, etc.) And scattered light scattered by a non-moving tissue). The frequency of the scattered light scattered by the moving scatterer is changed by the Doppler action corresponding to the flow velocity of the fluid as compared with the frequency of the scattered light scattered by the other fixed tissue. Due to the mutual interference between these two types of scattered light, the received light signal includes a beat signal corresponding to a so-called frequency difference signal. The second information output unit obtains information (for example, average frequency, first moment, etc.) based on the beat information by analyzing the beat signal.

  Here, according to the inventor's research, the following matters have been found. That is, when the concentration of the fluid is relatively low, the number of scatterers moving in the fluid per unit volume is small, which is caused by the Doppler shift of light caused by the movement of the scatterers included in the light reception signal. The power of the beat signal decreases. On the other hand, since the noise power caused by the parasitic capacitance of the input terminal of the amplifier that amplifies the received light signal that is a result of receiving the scattered light of the light irradiated to the object to be measured does not change, the influence of the noise becomes relatively large. . In other words, when the fluid concentration is relatively low, it is strongly influenced by noise caused by the parasitic capacitance of the input terminal of the amplifier, and the received light signal that is the result of receiving the scattered light of the light irradiated to the measurement target There is a possibility that the beat signal may be different from that which should originally appear. It should be noted that similar technical problems may occur accordingly when the fluid concentration is relatively high. Accordingly, when the flow rate or flow velocity is obtained only from the beat signal as in the conventional case, the obtained flow rate or flow velocity and the actual flow rate or flow velocity may deviate beyond the error range.

  Blood produces a mixed flow consisting of a blood cell component mainly composed of red blood cells and a plasma component. It is known that erythrocytes have a disk-like shape (diameter: 7-8 μm (micrometer), thickness: 2 μm), and orientation characteristics change depending on the flow rate (flow rate). For this reason, transmitted light and reflected light when light is irradiated to blood change due to the difference in flow rate even for blood of the same concentration, and conversely, even if the blood flow is the same, the difference in concentration is different. May vary.

  Thus, in the present embodiment, the second information output unit holds in advance correspondence information that defines the relationship between the light reception amount information and the information based on the beat signal. “Corresponding relationship information” is obtained by experimenting, for example, when a fluid having a known concentration is flowed, and determining a change in the relationship between the information based on the beat signal and the amount of received light for a plurality of concentrations according to the flow rate or flow velocity. What is necessary is just to build using the calculated | required data. The “correspondence information” according to the present embodiment may be, for example, a table indicating the relationship between information based on beat signals, received light amount information, and density, or information based on beat signals, received light amount information, and density. It may be represented as a map with each axis as an axis.

  The second information output unit is information on at least one of the flow rate of the fluid and the flow velocity of the fluid based on the information based on the beat signal, the received light amount information that changes according to the concentration of the fluid, and the correspondence information. Is output. Therefore, the fluid evaluation apparatus according to the present embodiment can suitably (in other words, highly accurately) obtain at least one of the flow rate and the flow velocity of the fluid while considering the concentration of the fluid.

  In one aspect of the fluid evaluation apparatus according to the present embodiment, the correspondence information is a plurality of values of parameters relating to the flow rate of the fluid or the flow velocity of the fluid in a coordinate system centered on each information based on the received light amount information and the beat signal. These are a plurality of relationship lines that correspond to each other and that define the relationship between the received light amount information and the information based on the beat signal.

  With this configuration, it is possible to obtain a parameter relating to the flow rate or flow rate of the fluid corresponding to the flow rate or flow rate of the fluid relatively easily from the flow rate information and the received light amount information, which is very advantageous in practice.

  In this aspect, the second information output unit includes at least one of the plurality of relational lines and the point indicated by the information based on the received light amount information output in the coordinate system and the beat signal included in the output received light signal. Information regarding at least one of the fluid flow rate and the fluid flow rate may be output by identifying a value of a parameter relating to the fluid flow rate or the fluid flow rate corresponding to the point based on the relationship line.

  With such a configuration, the correspondence information can be constructed relatively easily, and the flow rate or flow velocity of the fluid can be obtained suitably, which is very advantageous in practice.

  In another aspect of the fluid evaluation apparatus according to the present embodiment, the light receiving unit includes a first light receiving unit that receives scattered light (that is, forward scattered light) that has passed through the measurement target out of the scattered light, and the scattered light. A second light receiving unit that receives scattered light (that is, back scattered light) reflected by the measurement target, and the first information output unit is included in the light reception signal output from the first light receiving unit. The received light amount information that is information related to the received light amount of one light receiving unit is output, and the second information output unit outputs information based on the beat signal included in the received light signal output from the second light receiving unit, and the received received light amount Based on the information and the correspondence information, information on at least one of the fluid flow rate and the fluid flow velocity is output.

  According to this aspect, the light receiving unit is separated into the first light receiving unit used for obtaining the received light amount information and the second light receiving unit used for obtaining the beat signal.

  In another aspect of the fluid evaluation apparatus according to the present embodiment, the light source includes a first light source that emits laser light and a second light source that emits light different from the laser light, and the light receiving unit includes: The first scattered light from the measurement target of the laser light emitted from one light source is received, and a received light signal including a beat signal is output according to the received first scattered light, and emitted from the second light source. The second scattered light from the measurement target of the received light is received, and a received light signal including the received light amount information is output.

  According to this aspect, for example, a semiconductor laser having high monochromaticity and high coherence and widely distributed is used as the first light source, and the second light source does not depend on, for example, oxygen saturation of blood as an example of fluid. An LED that emits light of 805 nm (nanometers) can be used.

(Fluid evaluation method)
The fluid evaluation method according to the embodiment includes a light source that irradiates light to a measurement target in which a fluid flows inside, a scattered light from the measurement target of the irradiated light, and the received scattered light. A fluid evaluation method in a fluid evaluation apparatus comprising: a light receiving unit that outputs a light reception signal corresponding to the first received light amount information that is information related to the light reception amount of the light receiving unit included in the output light reception signal. Correspondence that regulates the relationship between the information output process and the information based on the beat signal caused by the Doppler shift of light, the output light reception amount information, and the information based on the light reception amount information and the beat signal, included in the output light reception signal A second information output step of outputting information on at least one of the flow rate of the fluid and the flow rate of the fluid based on the relationship information.

  According to the fluid evaluation method of this embodiment, similarly to the fluid evaluation apparatus according to the above-described embodiment, it is possible to suitably obtain at least one of the flow rate and the flow velocity of the fluid while considering the concentration of the fluid. In addition, also about the fluid evaluation method of this embodiment, the various aspects similar to the various aspects of the fluid evaluation apparatus which concern on embodiment mentioned above can be taken.

(Computer program)
The computer program according to the embodiment receives a light source that irradiates light to an object to be measured in which a fluid flows, and scattered light from the object to be measured of the irradiated light, and the received scattered light The first information for outputting received light amount information, which is information related to the received light amount of the light receiving unit included in the received light receiving signal, is received by a computer mounted on the fluid evaluation device including a light receiving unit that outputs a light receiving signal according to Correspondence relationship that defines the relationship between the output unit and information based on the beat signal resulting from the Doppler shift of light, the output light reception amount information, and the information based on the light reception amount information and the beat signal, included in the output light reception signal Based on the information, it functions as a second information output unit that outputs information on at least one of the flow rate of the fluid and the flow rate of the fluid.

  According to the computer program of this embodiment, from a recording medium such as a RAM (Random Access Memory), a CD-ROM (Compact Disc Read Only Memory), and a DVD-ROM (DVD Read Only Memory) that stores the computer program. If the computer program is read and executed by a computer provided in the fluid evaluation apparatus, or if the computer program is executed after being downloaded via communication means, the fluid evaluation apparatus according to the above-described embodiment. Can be realized relatively easily. Thereby, like the fluid evaluation apparatus according to the above-described embodiment, at least one of the flow rate and the flow velocity of the fluid can be suitably obtained while considering the concentration of the fluid.

  A CD-ROM, DVD-ROM, or the like in which the computer program according to the above embodiment is stored is an example of an embodiment according to the recording medium of the present invention.

  Embodiments of the fluid evaluation apparatus of the present invention will be described with reference to the drawings. In the following examples, blood is used as the fluid. Moreover, the tube which comprises the blood-flow circuit of an artificial dialysis apparatus is mentioned as a to-be-measured object. The fluid evaluation apparatus of the present invention can also be applied to the evaluation of blood flowing in blood vessels of a living body and any fluid other than blood (for example, ink, oil, sewage, seasoning, etc.).

<First embodiment>
A first embodiment of the fluid evaluation apparatus of the present invention will be described with reference to FIGS. In the present embodiment, blood flow is taken as an example of evaluation.

(Configuration of fluid evaluation device)
The configuration of the fluid evaluation apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the fluid evaluation apparatus according to the first embodiment.

  In FIG. 1, a fluid evaluation apparatus 100 includes a semiconductor laser 11, a laser driving unit 12, light receiving elements 21 and 31, IV conversion units 22 and 32, an LPF (Low-pass Filter) amplifier 23, and an A / D conversion unit 24. And 34, an LPF calculation unit 25, a flow rate two-dimensional estimation unit 26, a BPF (Band-pass Filter) amplifier 33, and a frequency analysis unit 35.

  The laser driving unit 12 generates a current for driving the semiconductor laser 11 (specifically, a specified driving current equal to or higher than a threshold current of the semiconductor laser 11). The semiconductor laser 11 oscillates in accordance with the drive current generated by the laser drive unit 12. The laser light emitted from the semiconductor laser 11 is, for example, an extracorporeal circulation blood circuit to be measured (that is, a transparent tube in which blood flows) via an optical system (not shown) such as a lens element. Is irradiated. The irradiated laser light is scattered and absorbed by a tube constituting an extracorporeal circulation blood circuit and blood flowing inside the tube.

  The extracorporeal blood circuit is semi-fixed to a housing (not shown) on which the semiconductor laser 11 and the light receiving elements 21 and 31 are installed and fixed so that the irradiation position does not shift due to vibration or the like.

  The light receiving element 21 receives scattered light (here, forward scattered light) of laser light irradiated on the measurement target. The scattered light received by the light receiving element 21 includes scattered light scattered by the blood flowing through the tubes constituting the extracorporeal circulation blood circuit (in particular, red blood cells that are moving scatterers contained in the blood) , Scattered light scattered by stationary tissue such as tubes.

  The light receiving element 21 outputs a detection current (see “detection current 1” in FIG. 1) as an example of the “light reception signal” according to the present invention, according to the intensity of the received scattered light. The IV conversion unit 22 converts the detection current output from the light receiving element 21 into a voltage signal (see “detection voltage 1” in FIG. 1).

  Here, an example of the light receiving element 21 and the IV conversion unit 22 will be described with reference to FIG. FIG. 2 is a circuit diagram illustrating an example of the light receiving element 21 and the IV conversion unit 22 according to the first embodiment.

  In FIG. 2, the light receiving element 21 is constituted by a photodetector PD0 made of, for example, a PIN type semiconductor. The IV conversion unit 22 includes an amplifier Amp0 and a feedback resistor Rf0. Here, the amplifier Amp0 constitutes a so-called transimpedance amplifier.

  The anode of the photodetector PD0 is connected to a reference potential such as a ground potential. The cathode of the photodetector PD0 is connected to the inverting input terminal of the amplifier Amp0. The non-inverting input terminal of the amplifier Amp0 is connected to a reference potential such as a ground potential.

  The current Idt0 output from the photodetector PD0 is converted into a voltage by the feedback resistor Rf0 and output from the amplifier Amp0 as a detection voltage (that is, a voltage signal).

  Returning to FIG. 1 again, the LPF amplifier 23 cuts and amplifies signal components in frequency bands other than the low-frequency signal components included in the voltage signal output from the IV converter 22. The LPF amplifier 23 also performs band limitation in order to reduce aliasing noise in the A / D converter 24.

  Here, the voltage signal output from the IV conversion unit 22 includes a high-frequency signal that is a noise component such as switching power supply noise. By inputting the voltage signal output from the IV conversion unit 22 to the LPF amplifier 23, it is possible to amplify the signal while suppressing noise components.

  The A / D converter 24 performs A / D conversion processing (that is, quantization processing) on the transmission signal (see “transmission signal” in FIG. 1) that is a signal output from the LPF amplifier 23.

  The LPF calculation unit 25 performs LPF calculation by digital signal processing (Digital Signal Processing: DSP) on the transmission signal quantized by the A / D conversion unit 24. The output of the LPF calculation unit 25 is input to the flow rate two-dimensional estimation unit 26 as the transmitted light amount TDC. Note that the LPF calculation is a calculation for suppressing high-frequency noise such as hum noise.

  The light receiving element 31 receives scattered light (here, backscattered light) of the laser light irradiated on the measurement target. The light receiving element 31 outputs a detection current (refer to “detection current 2” in FIG. 1) as another example of the “light reception signal” according to the present invention in accordance with the intensity of the scattered light received. The IV conversion unit 32 converts the detection current output from the light receiving element 31 into a voltage signal (see “detection voltage 2” in FIG. 1).

  The scattered light incident on the light receiving element 31 is scattered by scattered light scattered by a stationary tissue (for example, a tube constituting an extracorporeal circulation blood circuit) and red blood cells contained in blood that is a moving object. And scattered light. In the scattered light scattered by the red blood cells, a Doppler shift corresponding to the moving speed of the red blood cells occurs.

  For this reason, the scattered light scattered by the stationary tissue and the scattered light scattered by the red blood cells cause interference due to the coherence of the laser light. The detection current output from the light receiving element 31 includes a beat signal as a result of this interference.

  Here, an example of the light receiving element 31 and the IV conversion unit 32 will be described with reference to FIG. FIG. 3 is a circuit diagram illustrating an example of the light receiving element 31 and the IV conversion unit 32 according to the first embodiment.

  In FIG. 3, the light receiving element 31 is constituted by photodetectors PD1 and PD2 made of, for example, a PIN type semiconductor. As shown in FIG. 3, the cathode of the photodetector PD1 and the cathode of the photodetector PD2 are connected. That is, the photodetectors PD1 and PD2 are connected in series in opposite directions.

  The IV conversion unit 32 includes amplifiers Amp1, Amp2, and Amp3, feedback resistors Rf1, Rf2, and resistors Ra1, Rb1, Ra2, and Rb2.

  The anode of the photodetector PD1 is connected to the inverting input terminal of the amplifier Amp1. The non-inverting input terminal of the amplifier Amp1 is connected to a reference potential such as a ground potential. The anode of the photodetector PD2 is connected to the inverting input terminal of the amplifier Amp2. The non-inverting input terminal of the amplifier Amp2 is connected to a reference potential such as a ground potential. The output of the amplifier Amp1 is input to the non-inverting input terminal of the amplifier Amp3. The output of the amplifier Amp2 is input to the inverting input terminal of the amplifier Amp3.

  If the light receiving element 31 is configured as described above, a DC component corresponding to a steady light component included in scattered light incident on each of the photodetectors PD1 and PD2 out of currents output from the photodetectors PD1 and PD2 is reduced or reduced. Can be removed. On the other hand, a current mainly including an AC (Alternate Current) component corresponding to a signal light component included in incident scattered light can be output as a detection current.

Specifically, if the output current of the photodetector PD1 is Id1, and the output current of the photodetector PD2 is Id2, the photodetectors PD1 and PD2 are connected in series with opposite polarities.
Idt = Id2-Id1 (1)
It becomes.

  The scattered light received by the photodetector PD1 and the scattered light received by the photodetector PD2 are approximately uncorrelated current signals because their paths are different from each other when the wavelength of the light is a reference length. For this reason, by subtracting as in the above equation (1), the intensity of the beat signal becomes √2. On the other hand, the DC component included in the output current is canceled by subtraction.

  The light receiving element 31 can efficiently detect a beat signal as an AC component while canceling out the DC component of the output current of the photodetector PD1 and the DC component of the output current of the photodetector PD2.

  As described above, since the DC component is reduced or removed, even if the detection sensitivity of the amplifiers Amp1 and Amp2, which are so-called transimpedance amplifiers constituting the IV conversion unit 32, is set to be relatively high, saturation is achieved. Can be prevented. Specifically, the resistance values of the feedback resistors Rf1 and Rf2 can be set relatively high, and the current-voltage conversion sensitivity can be improved. As a result, the detection S / N ratio (Signal to Noise Ratio) can be improved.

  As described above, the non-inverting input terminals of the amplifiers Amp1 and Amp2 are connected to the reference potential. Then, due to the negative feedback action of the feedback resistor Rf1 or Rf2, the non-inverting input terminal and the inverting input terminal of each of the amplifiers Amp1 and Amp2 are in an imaginary shoot state and have approximately the same potential.

  As a result, the anode of the photodetector PD1 and the anode of the photodetector PD2 are at the same potential, and the photodetectors PD1 and PD2 operate in a so-called power generation mode. Then, dark current is suppressed by a so-called power generation mode, and noise due to dark current fluctuation can be suppressed.

The output voltage Vd1 output from the amplifier Amp1 is
Vd1 = Rf1 · Idt (2)
It becomes. The output voltage Vd2 output from the amplifier Amp2 is
Vd2 = −Rf2 · Idt (3)
It becomes.

  The amplifier Amp3 differentially amplifies the output voltages Vd1 and Vd2 and outputs a detection voltage Vout. The differential amplification removes common mode noise such as power supply noise and hum.

Here, when the resistor Ra1 and the resistor Ra2 are set to the resistance value Ra and the resistor Rb1 and the resistor Rb2 are set to the resistance value Rb, the detection voltage Vout is
Vout = (Rb / Ra) (Vd1-Vd2) (4)
It can be expressed as.

When the feedback resistor Rf1 and the feedback resistor Rf2 are set to the resistance value Rf, from the equations (2), (3), and (4), the detection voltage Vout is
Vout = 2Rf (Rb / Ra) Idt (5)
It can be expressed as.

  Returning to FIG. 1 again, the BPF amplifier 33 cuts and amplifies the signal components in the frequency band other than the signal components in the predetermined frequency band included in the voltage signal output from the IV conversion unit 32.

  Specifically, the BPF amplifier 33 amplifies a beat signal corresponding to a signal component in a predetermined frequency band by cutting a low frequency signal such as a hum signal and a high frequency signal such as a switching power supply noise. To do.

  The A / D converter 34 performs A / D conversion processing on the beat signal output from the BPF amplifier 33, and outputs beat data that is a quantized beat signal.

  The frequency analysis unit 35 performs frequency analysis such as FFT (Fast Fourier Transform) on the beat data using, for example, a DSP, and outputs a power spectrum P (f). The output power spectrum P (f) is input to the flow rate two-dimensional estimation unit 26.

  Here, a specific example of frequency analysis will be described with reference to FIG. FIG. 5 is a conceptual diagram showing an example of frequency analysis.

  In FIG. 5, beat data output from the A / D conversion unit 34 is accumulated in a buffer of the frequency analysis unit 35, for example, constituted by a memory. Note that the capacity of the buffer corresponds to, for example, the number of points n for executing FFT.

  Preprocessing for performing FFT is performed on the buffer data, which is output from the buffer, using a Hanning window. Thereafter, an n-point FFT operation is performed in the FFT unit on the data limited by the window function of the Hanning window.

  As a result of the FFT operation by the FFT unit, n / 2 point data is output as the power spectrum P (f) after the complex conjugate process by the complex conjugate unit.

  Returning to FIG. 1 again, the flow rate two-dimensional estimation unit 26 calculates the first moment 1stM and the average frequency fm based on the power spectrum P (f).

  Here, a specific example of the calculation method of the first moment and the average frequency will be described with reference to FIG. FIG. 6 is a conceptual diagram showing an example of a method for calculating the first moment and the average frequency.

  In FIG. 6, the first moment accumulation unit of the flow rate two-dimensional estimation unit 26 multiplies the power spectrum P (f) and the frequency vector f, and accumulates them in a specified band (here, f0 to f1). As the next moment, 1stM = Σ {f · P (f)} is output.

  The integrating unit of the flow rate two-dimensional estimating unit 26 integrates the power spectrum P (f) in a specified band (here, f0 to f1), and outputs Ps = Σ {P (f)}. The division unit of the flow rate two-dimensional estimation unit 26 outputs a value obtained by dividing the first moment 1stM by Ps, which is the output of the integration unit, as an average frequency fm.

(Flow estimation)
Next, flow rate estimation processing (that is, processing in the flow rate two-dimensional estimation unit 26) by the fluid evaluation device 100 configured as described above will be described.

  The relationship between the transmitted light amount TDC output from the LPF calculation unit 25 and the hematocrit value Hct corresponding to the blood concentration is, for example, as shown in FIG. FIG. 4 is a diagram illustrating an example of the relationship between the hematocrit value and the amount of transmitted light.

  As shown in FIG. 4, when the blood concentration increases (that is, when the hematocrit value Hct increases), the amount of transmitted light TDC attenuates due to, for example, an increase in light scattering and absorption by red blood cells.

  Here, according to the study by the present inventor, the transmitted light amount TDC mainly changes according to the hematocrit value Hct, but also depends on the flow velocity of blood flowing in the tube constituting the extracorporeal circulation blood circuit. But it turns out.

  Further, the relationship between the power spectrum P (f) of the beat signal output from the frequency analysis unit 35 and the frequency f is, for example, as shown in FIG. FIG. 7 is a diagram illustrating an example of the relationship between the frequency and the power spectrum.

  As shown in FIG. 7, when the flow rate of blood is relatively low, that is, when the flow rate of red blood cells as scatterers flowing through the tubes constituting the extracorporeal circulation blood circuit is relatively slow, the low frequency component becomes the high frequency component. The number is significantly increased (see the broken line in FIG. 7). On the other hand, when the blood flow rate is relatively high, that is, when the flow rate of red blood cells is relatively high, the high-frequency component is relatively large (see the solid line in FIG. 7). This is because when the speed of the moving body (here, red blood cells) increases, the amount of Doppler shift increases, and components in a region where the frequency of the frequency spectrum of the beat signal is relatively high increase.

  The relationship between the first moment 1stM and the average frequency fm obtained based on the power spectrum P (f) and the flow velocity is as shown in FIG. 8, for example. FIG. 8 is a diagram illustrating an example of the relationship between the flow velocity and the first moment or the average frequency.

  As shown in FIG. 8, both the first moment 1stM (see the broken line in FIG. 8) and the average frequency fm (see the solid line in FIG. 8) increase as the flow velocity increases. However, both the first moment 1stM and the average frequency fm depend not only on the flow velocity but also on the concentration of the fluid containing the scatterer (here, the hematocrit value Hct).

  Here, the reason why the average frequency fm depends on the concentration of the fluid containing the scatterer will be described with reference to FIG. FIG. 9 is an example of measured values obtained by actually measuring the power spectrum of the beat signal measured at a constant fluid velocity for a plurality of fluid concentrations. In FIG. 9, the solid line indicates the actual measurement value for the high-concentration fluid, and the alternate long and short dash line indicates the actual measurement value for the low-concentration fluid. A thick broken line indicates amplifier noise, and a thin broken line indicates a theoretical value for a low-concentration fluid when there is no amplifier noise.

  The amplifier noise is dominated by the noise generated by the transimpedance amplifier at the first stage of the amplifier, and increases as the frequency increases. This amplifier noise is related to the parasitic capacitance of the amplifier input terminal. The frequency characteristic of the amplifier noise has a differential characteristic. For this reason, noise power increases as the frequency increases.

  As the concentration of the fluid increases, the number of scatterers contained in the fluid per unit volume increases, so the power of the measured beat signal increases over the frequency. On the other hand, as the concentration of the fluid decreases, the number of scatterers contained in the fluid per unit volume decreases, so the power of the measured beat signal decreases across the frequency.

  Since the amplifier noise does not depend on the power of the beat signal, a low-concentration fluid with a relatively small beat signal power has a relatively large influence of the amplifier noise, and the beat signal power apparently increases particularly in a high frequency region. On the other hand, a high-concentration fluid with relatively high beat signal power is hardly affected by amplifier noise.

  Since the fluid velocity is constant, the average frequency fm that is proportional to the fluid velocity is theoretically constant even if the fluid concentration changes. However, due to the influence of amplifier noise, the average frequency obtained from the actual measurement value for the high-concentration fluid (see the black circle in FIG. 9) and the average frequency obtained from the actual measurement value for the low-concentration fluid (see the thick white circle in FIG. 9). (If there is no influence of amplifier noise, the average frequency of a low-concentration fluid is a value indicated by a thin white circle in FIG. 9).

  In order to reduce the influence of the amplifier noise, a measure of increasing the power of the semiconductor laser 11 is conceivable. However, for example, an increase in power consumption or an adverse effect on the eyes of workers or subjects may occur. That is, the power increase of the semiconductor laser 11 is limited from the viewpoint of safety and power consumption.

  As described above, the transmitted light amount TDC depends on the hematocrit value Hct (that is, the concentration) and the flow velocity, and the power spectrum P (f), and the average frequency fm and the first moment 1stM obtained from the power spectrum P (f). Depends on flow rate and concentration. The inventor of the present application has come up with the idea of obtaining at least one of the hematocrit value Hct of blood, the flow rate or the flow rate based on two parameters of the transmitted light amount TDC and the average frequency fm or the first moment 1stM.

  The method for obtaining the power spectrum P (f), the average frequency fm, and the first moment 1stM is not limited to the above-described method, and various known modes can be applied.

  In the present embodiment, a method of obtaining the blood flow rate Q from the transmitted light amount TDC and the average frequency fm or the first moment 1stM will be described.

  The flow rate two-dimensional estimation unit 26 (see FIG. 1) stores in advance map data indicating the relationship between the transmitted light amount TDC and the average frequency fm for each flow rate, for example, as shown in FIG.

  In FIG. 10, Line1, Line2, and Line3 are, for example, a relationship line between the transmitted light amount TDC and the average frequency fm when the flow rate Q = 50 [milliliter / minute], and when the flow rate Q = 100 [milliliter / minute]. A relationship line between the transmitted light amount TDC and the average frequency fm, and a relationship line between the transmitted light amount TDC and the average frequency fm when the flow rate Q = 150 [milliliter / min] are shown.

  In FIG. 10, a region Ar1 means a region below Line 1 in the drawing, a region Ar2 means a region between Line1 and Line2, and a region Ar3 means a region between Line2 and Line3. Ar4 means a region on the upper side of Line3 in the drawing.

  The map data as shown in FIG. 10 typically includes a plurality of measured values of the transmitted light amount TDC and the average frequency fm obtained when the fluid (here, blood) having a known concentration is irradiated with light. The flow rate (flow velocity) is obtained, and a relationship line (for example, “Line 1”) between the transmitted light amount TDC and the average frequency fm is obtained from the actually measured values corresponding to one flow rate based on the obtained actually measured values. You can build it.

  In FIG. 10, when the transmitted light amount TDC is “x” and the average frequency fm is “y”, Line1 indicating the flow rate Q = 50 [milliliter / minute] can be expressed as “y = K1 · x + C1”. Similarly, Line2 indicating the flow rate Q = 100 [milliliter / minute] is expressed as “y = K2 · x + C2”, and Line3 indicating the flow rate Q = 150 [milliliter / minute] is expressed as “y = K3 · x + C3”. expressed. “K1”, “C1”, “K2”, “C2”, “K3”, and “C3” are constants obtained from the actual measurement values used to construct the map data shown in FIG.

The flow rate estimation processing according to the present embodiment will be described with reference to the flowchart of FIG. 11 in addition to FIG. The value corresponding to the transmitted light amount TDC output from the LPF calculation unit 25 is “x _i ”, and the value corresponding to the average frequency fm based on the power spectrum P (f) output from the frequency analysis unit 35 is “y”. _i ”.

In FIG. 11, the flow rate two-dimensional estimation unit 26 (see FIG. 1) first calculates the measurement result “x _i ” (that is, the equation “y = K1 · x + C1” indicating Line 1 in FIG. , The measured value of the transmitted light amount TDC) is substituted, and “y1” which is the value of the average frequency fm at which the transmitted light amount TDC becomes “x _i ” is obtained on Line1. Subsequently, the two-dimensional flow estimation unit 26 compares the obtained “y1” with the measurement result “y _i ” (that is, the measured value of the average frequency fm) by the fluid evaluation device 100 (step S101). .

Specifically, the flow rate two-dimensional estimation unit 26 subtracts “y1” from “y _i ” (that is, “y _i −y1 = y _i − (K1 · x _i + C1)”). If this calculation result is negative, the point (x _i , y 1) on Line 1 is larger than the measurement result (x _i , y _i ) (that is, the measurement result is the line 1 on the map data). Will be on the lower side). On the other hand, if the result is not negative, the measurement result _(x i, _{y i)} will be greater than the point on Line1 _(x i, y1) is equal or point _(x i, y1) _(i.e., Measurement The result will be on Line1 or above Line1 on the map data).

When it is determined that the calculation result is negative (ie, “y _i − (K1 · x _i + C1) <0”) (step S101: Yes), the flow rate two-dimensional estimation unit 26 determines the measurement result (x _i , It is determined that y _i ) exists in the area Ar1 which is the lower area of Line1 on the map data (step S102).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the flow rate Q using the measurement results (x _i , y _i ) (step S103). As shown in FIG. 10, since the area Ar1 is below Line1, the flow rate two-dimensional estimation unit 26 estimates the flow rate Q corresponding to the measurement result by extrapolation processing based on Line1.

Specifically, the flow rate two-dimensional estimation unit 26 first substitutes the measurement result “x _i ” into the expression “y = K1 · x + C1” indicating Line1, and the transmitted light amount TDC is “x” on Line1. “yH” (the same value as “y1” described above), which is the value of the average frequency fm that becomes “ _i ”, is obtained. That is, yH = K1 · x _i + C1.

Next, the flow rate two-dimensional estimation unit 26 multiplies the difference between the obtained “yH” and the measurement result “y _i ” by the estimation coefficient α2 and adds 50 (Line1 has a flow rate Q = 50 [milliliter / To obtain the flow rate Q. That is, the flow rate Q = 50 + α2 (y _i− yH).

When it is determined in the process of step S101 that the calculation result is not negative (that is, “y _i − (K1 · x _i + C1) ≧ 0”) (step S101: No), the flow rate two-dimensional estimation unit 26 The measurement result “x _i ” is substituted into the expression “y = K2 · x + C2” indicating Line 2 of 10 and “y2” is the value of the average frequency fm at which the transmitted light amount TDC becomes “x _i ” on Line2. ” Subsequently, the two-dimensional flow rate estimation unit 26 compares the obtained “y2” with the measurement result “y _i ” (step S104).

When it is determined that the comparison result is negative (that is, “y _i − (K2 · x _i + C2) <0”) (step S104: Yes), the flow rate two-dimensional estimation unit 26 determines the measurement result (x _i , It is determined that y _i ) exists in the area Ar2 that is the area between Line1 and Line2 on the map data (step S105).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the flow rate Q using the measurement results (x _i , y _i ) (step S106). As shown in FIG. 10, since the region Ar2 is between Line1 and Line2, the flow rate two-dimensional estimation unit 26 estimates the flow rate Q corresponding to the measurement result by interpolation processing based on Line1 and Line2.

Specifically, the flow rate two-dimensional estimation unit 26 first substitutes the measurement result “x _i ” into the expression “y = K1 · x + C1” indicating Line1, and the transmitted light amount TDC is “x” on Line1. “yL”, which is the value of the average frequency fm that becomes “ _i ”, is obtained. That is, yL = K1 · x _i + C1.

Similarly, the flow rate two-dimensional estimation unit 26 substitutes the measurement result “x _i ” into the expression “y = K 2 · x + C 2” indicating Line 2, and the transmitted light amount TDC becomes “x _i ” on Line 2. “YH” (the same value as “y2” described above), which is the value of the average frequency fm, is obtained. That is, yH = K2 · x _i + C2.

Next, the flow rate two-dimensional estimation unit 26 obtains how far the measurement result “y _i ” is from each of the obtained “yL” and “yH”, for example, at a flow rate Q = 50 [milliliter / minute]. On the other hand, the flow rate Q is obtained by correcting it. That is, the flow rate Q = 50 + (100−50) {(y _i −yL) / (yH−yL)}.

In the process of step S104, when it is determined that the comparison result is not negative (ie, “y _i − (K2 · x _i + C2) ≧ 0”) (step S104: No), the flow rate two-dimensional estimation unit 26 The measurement result “x _i ” is substituted into the expression “y = K3 · x + C3” indicating Line 3 of 10 and “y3” which is the value of the average frequency fm at which the transmitted light amount TDC becomes “x _i ” on Line3. ” Subsequently, the flow rate two-dimensional estimation unit 26 compares the obtained “y3” with the measurement result “y _i ” (step S107).

When it is determined that the comparison result is negative (that is, “y _i − (K3 · x _i + C3) <0”) (step S107: Yes), the flow rate two-dimensional estimation unit 26 determines the measurement result (x _i , It is determined that y _i ) exists in the area Ar3 which is an area between Line2 and Line3 on the map data (step S108).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the flow rate Q using the measurement results (x _i , y _i ) (step S109).

Specifically, the flow rate two-dimensional estimation unit 26 substitutes the measurement result “x _i ” into the expression “y = K2 · x + C2” indicating Line2, and the transmitted light amount TDC is “x _i ” on Line2. “YL” which is the value of the average frequency fm is obtained. That is, yL = K2 · x _i + C2.

Similarly, the flow rate two-dimensional estimation unit 26 substitutes the measurement result “x _i ” for the expression “y = K3 · x + C3” indicating Line 3 and the transmitted light amount TDC becomes “x _i ” on Line 3. “YH” (the same value as “y3” described above), which is the value of the average frequency fm, is obtained. That is, yH = K3 · x _i + C3.

Next, the flow rate two-dimensional estimation unit 26 determines the flow rate Q = 100 + (150-100) {(y _i -yL) / based on the measurement result “y _i ” and the obtained “yL” and “yH”. The flow rate Q is obtained according to the equation (yH−yL)}.

When it is determined in the process of step S107 that the comparison result is not negative (ie, “y _i − (K3 · x _i + C3) ≧ 0”) (step S107: No), the flow rate two-dimensional estimation unit 26 performs measurement. It is determined that the result (x _i , y _i ) exists in the area Ar4 that is on the line 3 or on the upper side of the line 3 on the map data (step S110).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the flow rate Q using the measurement results (x _i , y _i ) (step S111).

Specifically, the flow rate two-dimensional estimation unit 26 first substitutes the measurement result “x _i ” into the expression “y = K3 · x + C3” indicating Line3, and the transmitted light amount TDC is “x” on Line3. “yL” (the same value as “y3” described above), which is the value of the average frequency fm that becomes “ _i ”, is obtained. That is, yL = K3 · x _i + C3.

Next, the flow rate two-dimensional estimation unit 26 multiplies the difference between the obtained “yL” and the measurement result “y _i ” by the estimation coefficient β2 and adds it to 150 (Line 3 has a flow rate Q = 150 [milliliter / To obtain the flow rate Q. That is, the flow rate Q = 150 + β2 (y _i −yL).

  In the above-described flow rate estimation, the relationship between the transmitted light amount TDC and the average frequency fm as shown in FIG. 10 is replaced with the map data shown for each flow rate, and the relationship between the transmitted light amount TDC and the first moment 1stM. May be performed using map data indicating each flow rate.

  The flow rate two-dimensional estimation unit 26 may obtain the blood flow velocity in addition to or instead of the flow rate Q. In this case, the flow rate two-dimensional estimation unit 26 may obtain the flow velocity based on the obtained flow rate Q, for example, construct map data as shown in FIG. 10 for the flow velocity, and construct the constructed map data The flow rate may be obtained based on Various known modes can be applied to the method for obtaining the flow velocity from the flow rate Q.

(effect)
Next, the effect of the fluid evaluation apparatus 100 according to the present embodiment will be described with reference to FIG. FIG. 12A is an example of an estimation result when the flow rate is estimated only from the average frequency. FIG. 12B is an example of an estimation result when the flow rate is estimated from the transmitted light amount and the average frequency. The estimation results shown in FIG. 12 are the estimation results when the blood concentration (hematocrit value Hct) is changed while the flow rate (that is, the flow rate Q of blood flowing in the tube constituting the extracorporeal circulation blood circuit) is kept constant. It is.

  When the flow rate Q is estimated from only the average frequency fm, as shown in FIG. 12A, the estimated flow rate Q increases as the concentration decreases. That is, if the flow rate Q is estimated only from the average frequency fm, the error increases as the concentration decreases.

  On the other hand, when the flow rate Q is estimated from the transmitted light amount TDC and the average frequency fm as in this embodiment, the flow rate Q is constant without depending on the concentration, as shown in FIG. That is, according to the fluid evaluation apparatus 100, the flow rate Q can be obtained with high accuracy without being affected by the blood concentration.

  The “semiconductor laser 11” and “laser driver 12” according to the present embodiment are examples of the “light source” according to the present invention. The “light receiving elements 21 and 31” according to the present embodiment are examples of the “light receiving portion”, the “first light receiving portion”, and the “second light receiving portion” according to the present invention. The “LPF calculation unit 25” according to the present embodiment is an example of the “first information output unit” according to the present invention. The “frequency analysis unit 35” and the “flow rate two-dimensional estimation unit 26” according to the present embodiment are examples of the “second information output unit” according to the present invention.

  “Power spectrum P (f)”, “average frequency fm”, and “first moment 1stM” according to the present embodiment are examples of “information based on beat signals” according to the present invention. The “transmitted light amount TDC” according to the present embodiment is an example of “light reception amount information” according to the present invention. The “flow rate Q” according to the present embodiment is an example of the “parameter relating to the flow rate or flow velocity” according to the present invention. “Map data” shown in FIG. 10 is an example of “correspondence information” according to the present invention. “Line 1”, “Line 2”, and “Line 3” in FIG. 10 are examples of “relation lines” according to the present invention.

<First Modification>
Next, a first modification of the fluid evaluation apparatus according to the present embodiment will be described with reference to FIG. In addition, about the 1st modification, while abbreviate | omitting the description which overlaps with 1st Example mentioned above, the same code | symbol is attached | subjected and shown to the common location on drawing. FIG. 13 is a conceptual diagram illustrating the concept of flow rate estimation according to a first modification of the first embodiment.

In this modification, the measurement result (x _i , y _i ) is present in the area Ar2 or area Ar3 (see FIG. 10) of the map data, and the method for obtaining the flow rate Q by interpolation processing is the same as in the first embodiment described above. Different.

  Specifically, the flow rate two-dimensional estimation unit 26 first obtains the length dL of the perpendicular drawn from the measurement point P to Line 1 and the length dH of the perpendicular drawn from the measurement point P to Line 2 (FIG. 13). reference).

Here, the length dL = {y _i − (K1 · x _i + C1)} / {√ (1−K1 ² )}, and the length dH = {(K2 · x _i + C1) −y _i } / { √ (1-K2 ² )}.

  Next, the flow rate two-dimensional estimation unit 26 uses the length dL and the length dH to determine how much the measurement point P deviates from, for example, the flow rate Q = 50 [milliliter / minute] (that is, Line 1). Thus, the flow rate Q is obtained. Specifically, the flow rate two-dimensional estimation unit 26 obtains the flow rate Q according to the formula “flow rate Q = 50 + (100−50) {dL / (dL + dH)}”.

<Second Modification>
Next, a second modification of the fluid evaluation apparatus according to the present embodiment will be described with reference to FIG. In addition, about the 2nd modification, while omitting the description which overlaps with the 1st Example mentioned above, the same code | symbol is attached | subjected and shown to a common location on drawing. FIG. 14 is a block diagram showing a configuration of a fluid evaluation apparatus according to a second modification of the first embodiment having the same meaning as in FIG. 1.

  In FIG. 14, a fluid evaluation apparatus 200 according to this modification includes a semiconductor laser 11, a laser driving unit 12, a light receiving element 21, an IV conversion unit 22, an LPF amplifier 23, A / D conversion units 24 and 42, and LPF calculation. Unit 25, flow rate two-dimensional estimation unit 26, BPF amplifier 41, and frequency analysis unit 43.

  The detection current output from the light receiving element 21 includes a beat signal resulting from the Doppler shift of the laser light.

  The BPF amplifier 41 cuts and amplifies a signal component in a frequency band other than a signal component in a predetermined frequency band included in the voltage signal output from the IV converter 22.

  Specifically, the BPF amplifier 41 amplifies a beat signal corresponding to a signal component of a predetermined frequency band by cutting a low frequency signal such as a hum signal and a high frequency signal such as a switching power supply noise. To do.

  The A / D conversion unit 42 performs A / D conversion processing on the beat signal output from the BPF amplifier 41, and outputs beat data that is a quantized beat signal.

  The frequency analysis unit 43 performs frequency analysis such as FFT on the beat data using, for example, a DSP, and outputs a power spectrum P (f). The output power spectrum P (f) is input to the flow rate two-dimensional estimation unit 26.

<Third Modification>
Next, a third modification of the fluid evaluation apparatus according to the present embodiment will be described with reference to FIG. In addition, about the 3rd modification, while abbreviate | omitting the description which overlaps with 1st Example mentioned above, the same code | symbol is attached | subjected and shown to a common location on drawing. FIG. 15 is a block diagram showing a configuration of a fluid evaluation apparatus according to a third modification of the first embodiment having the same meaning as in FIG.

  In FIG. 15, the fluid evaluation apparatus 300 according to this modification includes a semiconductor laser 11, a laser driving unit 12, an LED 51, an LED driving unit 52, light receiving elements 21 and 31, IV conversion units 22 and 32, an LPF amplifier 23, The A / D conversion units 24 and 34, the LPF calculation unit 25, the flow rate two-dimensional estimation unit 26, the BPF amplifier 33, and the frequency analysis unit 35 are provided.

  The semiconductor laser 11 is a semiconductor laser that can emit laser light having a wavelength of, for example, 780 nm, which has high monochromaticity and interference and is widely distributed. The LED 51 is an LED that can emit light having a wavelength of, for example, 805 nm that does not depend on the oxygen saturation of blood.

  Each of the laser drive unit 12 and the LED drive unit 52 receives a signal LD_En and a signal LED_En so that the measurement target is alternately irradiated with laser light and LED light (that is, time-division driven). Is done. Further, the signal LD_En is also input to the A / D converter 34 so that the laser driver 12 and the A / D converter 34 operate in synchronization. Similarly, the signal LED_En is also input to the A / D conversion unit 24 so that the LED driving unit 52 and the A / D conversion unit 24 operate in synchronization.

  The “semiconductor laser 11” and “LED 51” according to the present modification are examples of the “first light source” and the “second light source” according to the present invention, respectively.

<Second embodiment>
A second embodiment of the fluid evaluation apparatus of the present invention will be described with reference to FIGS. The second embodiment is the same as the first embodiment described above except that a hematocrit value that is an index indicating the blood concentration is estimated instead of or in addition to the flow rate. Accordingly, in the second embodiment, the description overlapping with that of the first embodiment is omitted, and the common portions in the drawings are denoted by the same reference numerals, and only the points that are basically different are shown in FIGS. The description will be given with reference.

  The flow rate two-dimensional estimation unit 26 (see FIG. 1) of the fluid evaluation apparatus 100 according to the present embodiment, for example, as shown in FIG. For example, as shown in FIG. 17, at least one of map data indicating the relationship between the transmitted light amount TDC and the first moment 1stM for each hematocrit value is stored in advance.

  In FIG. 16, Line1, Line2, and Line3 are, for example, a relationship line between the transmitted light amount TDC and the average frequency fm when the hematocrit value Hct = 35%, and the transmitted light amount TDC and the average when the hematocrit value Hct = 30%. A relationship line with the frequency fm and a relationship line between the transmitted light amount TDC and the average frequency fm when the hematocrit value Hct = 25% are shown.

  In FIG. 17, Line1, Line2, and Line3 are, for example, a relationship line between the transmitted light amount TDC and the first moment 1stM when the hematocrit value Hct = 35%, and the transmitted light amount TDC when the hematocrit value Hct = 30%. A relationship line with the first moment 1stM and a relationship line between the transmitted light amount TDC and the first moment 1stM when the hematocrit value Hct = 25% are shown.

  In FIG. 16 and FIG. 17, a region Ar1 means a region on the left side of Line1 in the drawing, a region Ar2 means a region between Line1 and Line2, and a region Ar3 means a region between Line2 and Line3. The region Ar4 means a region on the right side of the drawing of Line3.

  The map data as shown in FIG. 16 and FIG. 17 typically includes a transmitted light amount TDC obtained when light is irradiated to a fluid (here, blood) having a known concentration, an average frequency fm, or a first moment. Measured values for 1stM are obtained for a plurality of flow rates, and based on the obtained measured values, a relationship line between the transmitted light amount TDC for a fluid of one concentration and the average frequency fm or first moment 1stM ( For example, “Line 1” or the like may be acquired.

  As described above, the average frequency fm and the first moment 1stM obtained from the power spectrum P (f) are affected by, for example, amplifier noise. Further, the inventor of the present application considers that the transmitted light amount TDC is affected by a scatterer included in the fluid. For this reason, it is desirable from the viewpoint of the accuracy and reliability of the finally determined hematocrit value Hct to construct map data as shown in FIGS. In particular, as can be seen from FIG. 16 and FIG. 17, it has been found by experiments of the present inventor that the slopes of Line1, Line2, and Line3 differ depending on the hematocrit value Hct. It is extremely difficult to construct map data.

  In FIG. 16, when the transmitted light amount TDC is “x” and the average frequency fm is “y”, Line 1 indicating a hematocrit value Hct = 35% can be expressed as “y = −K35 · x + C35”. Similarly, Line2 indicating a hematocrit value Hct = 30% is expressed as “y = −K30 · x + C30”, and Line3 indicating a hematocrit value Hct = 25% is expressed as “y = −K25 · x + C25”. “K35”, “C35”, “K30”, “C30”, “K25”, and “C25” are constants obtained from the actual measurement values used to construct the map data shown in FIG.

  In FIG. 17, when the transmitted light amount TDC is “x” and the first moment 1stM is “y”, Line 1 indicating a hematocrit value Hct = 35% can be expressed as “y = −K35 · x + C35”. Similarly, Line2 indicating a hematocrit value Hct = 30% is expressed as “y = −K30 · x + C30”, and Line3 indicating a hematocrit value Hct = 25% is expressed as “y = −K25 · x + C25”. “K35”, “C35”, “K30”, “C30”, “K25”, and “C25” are constants obtained from the actual measurement values used to construct the map data shown in FIG.

  In the hematocrit estimation process according to this example to be described below, any of the map data shown in FIGS. 16 and 17 can be used, but here, description will be made using the map data shown in FIG.

The hematocrit estimation process according to this example will be described with reference to the flowchart of FIG. 18 in addition to FIG. The value corresponding to the transmitted light amount TDC output from the LPF calculation unit 25 is “x _i ”, and the value corresponding to the average frequency fm based on the power spectrum P (f) output from the frequency analysis unit 35 is “y”. _i ”.

In FIG. 18, the flow rate two-dimensional estimation unit 26 (see FIG. 1) first adds the measurement result “y _i ” (“y = −K35 · x + C35”) indicating the Line 1 in FIG. That is, the measured value of the average frequency fm) is substituted, and “x1” that is the value of the transmitted light amount TDC at which the average frequency fm becomes “y _i ” is obtained on Line1. Subsequently, the flow rate two-dimensional estimation unit 26 compares the obtained “x1” with the measurement result “x _i ” (that is, the measured value of the transmitted light amount TDC) by the fluid evaluation device 100 (step S201). .

Specifically, the flow rate two-dimensional estimation unit 26 subtracts “x _i ” from “x1” (that is, “x1−x _i = (C35−y _i ) / K35−x _i ”). If this calculation result is positive, the point (x1, y _i ) on the Line 1 is larger than the measurement result (x _i , y _i ) (that is, the measurement result is the Line 1 on the map data). Will be on the left). On the other hand, if the result is not positive, the measurement result _(x i, _{y i)} will be greater than the points on Line1 (x1, _{y i)} equal to or point (x1, _{y i)} (i.e., Measurement The result will be on Line 1 or on the right side of Line 1 on the map data).

When it is determined that the calculation result is positive (that is, “(C35−y _i ) / K35−x _i > 0”) (step S201: Yes), the flow rate two-dimensional estimation unit 26 determines the measurement result (x _i , Y _i ) is determined to exist in the area Ar1 that is the area on the left side of Line1 on the map data (step S202).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the hematocrit value Hct using the measurement results (x _i , y _i ) (step S203).

  Here, the estimation of the hematocrit value Hct will be described with reference to FIG. As shown in FIG. 16, since the measurement point P1 of the area Ar1 is on the left side of Line1, the flow rate two-dimensional estimation unit 26 estimates the hematocrit value Hct corresponding to the measurement point P1 by extrapolation processing based on Line1. .

Specifically, the flow rate two-dimensional estimation unit 26 first substitutes the measurement result “y _i ” into the expression “y = −K35 · x + C35” indicating Line1, and the average frequency fm is “1” on Line1. “xH” (the same value as “x1” described above), which is the value of the transmitted light amount TDC related to the point P2 corresponding to y _i ”, is obtained. That is, xH = (C35−y _i ) / K35.

Next, the flow rate two-dimensional estimation unit 26 multiplies the difference between the obtained “xH” and the measurement result “x _i ” by the estimation coefficient α and adds 35 (Line1 is set to a hematocrit value Hct = 35%). Therefore, the hematocrit value Hct is obtained. That is, the hematocrit value Hct = 35 + α (xH−x _i ).

Returning to FIG. 18 again, in the process of step S201, when it is determined that the calculation result is not positive (that is, “(C35−y _i ) / K35−x _i ≦ 0”) (step S201: No), the flow rate 2 The dimension estimation unit 26 substitutes the measurement result “y _i ” for the expression “y = −K30 · x + C30” indicating Line 2 in FIG. 16, and transmits the average frequency fm “y _i ” on Line 2. “X2” which is the value of the light quantity TDC is obtained. Subsequently, the flow rate two-dimensional estimation unit 26 compares the obtained “x2” with the measurement result “x _i ” (step S204).

When it is determined that the comparison result is positive (that is, “(C30−y _i ) / K30−x _i > 0”) (step S204: Yes), the flow rate two-dimensional estimation unit 26 determines the measurement result (x _i , Y _i ) is determined to exist in the area Ar2 that is the area between Line1 and Line2 on the map data (step S205).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the hematocrit value Hct using the measurement results (x _i , y _i ) (step S206).

  Here, the estimation of the hematocrit value Hct will be described with reference to FIG. As shown in FIG. 16, since the measurement point P3 of the area Ar2 is between Line1 and Line2, the flow rate two-dimensional estimation unit 26 performs the hematocrit value Hct corresponding to the measurement point P3 by interpolation processing based on Line1 and Line2. Is estimated.

Specifically, the flow rate two-dimensional estimation unit 26 first substitutes the measurement result “y _i ” into the expression “y = −K35 · x + C35” indicating Line1, and the average frequency fm is “1” on Line1. “xL”, which is the value of the transmitted light amount TDC related to the point P4 corresponding to y _i ”, is obtained. That is, xL = (C35−y _i ) / K35.

Similarly, the flow rate two-dimensional estimation unit 26 substitutes the measurement result “y _i ” for the expression “y = −K30 · x + C30” indicating Line 2, and the average frequency fm is “y _i ” on Line 2. “XH” (the same value as “x2” described above), which is the value of the transmitted light amount TDC related to the point P5, is obtained. That is, xH = (C30−y _i ) / K30.

Next, the flow rate two-dimensional estimation unit 26 obtains how far the measurement result “x _i ” is from each of the obtained “xL” and “xH”, and corrects, for example, the hematocrit value Hct = 35%. Thus, the hematocrit value Hct is obtained. That is, the hematocrit value Hct = 35− (35−30) {(x _i −xL) / (xH−xL)}.

Returning to FIG. 18 again, in the process of step S204, when it is determined that the comparison result is not positive (that is, “(C30−y _i ) / K30−x _i ≦ 0”) (step S204: No), the flow rate 2 The dimension estimation unit 26 substitutes the measurement result “y _i ” into the expression “y = −K25 · x + C25” indicating Line 3 in FIG. 16, and transmits the average frequency fm “y _i ” on Line 3. “X3” which is the value of the light quantity TDC is obtained. Subsequently, the flow rate two-dimensional estimation unit 26 compares the obtained “x3” with the measurement result “x _i ” (step S207).

When it is determined that the comparison result is positive (ie, “(C25−y _i ) / K25−x _i > 0”) (step S207: Yes), the flow rate two-dimensional estimation unit 26 determines the measurement result (x _i , Y _i ) is determined to exist in the area Ar3 that is the area between Line2 and Line3 on the map data (step S208).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the hematocrit value Hct using the measurement results (x _i , y _i ) (step S209).

Specifically, the flow rate two-dimensional estimation unit 26 substitutes the measurement result “y _i ” into the expression “y = −K30 · x + C30” indicating Line2, and the average frequency fm is “y _i ” on Line2. “XL”, which is the value of the transmitted light amount TDC, is obtained. That is, xL = (C30−y _i ) / K30.

Similarly, the flow rate two-dimensional estimation unit 26 substitutes the measurement result “y _i ” into the expression “y = −K25 · x + C25” indicating Line 3 and the average frequency fm is “y _i ” on Line 3. “XH” (the same value as “x3” described above), which is a value of the transmitted light amount TDC. That is, xH = (C25−y _i ) / K25.

Next, the two-dimensional flow estimation unit 26 determines the hematocrit value Hct = 30− (30−25) {(x _i −xL) based on the measurement result “x _i ” and the obtained “xL” and “xH”. ) / (XH−xL)}, the hematocrit value Hct is obtained.

When it is determined in the process of step S207 that the comparison result is not positive (that is, “(C25−y _i ) / K25−x _i ≦ 0”) (step S207: No), the flow rate two-dimensional estimation unit 26 It is determined that the measurement result (x _i , y _i ) exists in the area Ar4 that is the area on the right side of Line3 on the map data (step S210).

Subsequently, the flow rate two-dimensional estimation unit 26 estimates the hematocrit value Hct using the measurement results (x _i , y _i ) (step S211).

Specifically, the flow rate two-dimensional estimation unit 26 first substitutes the measurement result “y _i ” into the expression “y = −K25 · x + C25” indicating Line3, and the average frequency fm is “3” on Line3. “xL” (the same value as “x3” described above), which is a value of the transmitted light amount TDC to be y _i ”, is obtained. That is, xL = (C25−y _i ) / K25.

Next, the flow rate two-dimensional estimation unit 26 multiplies the difference between the obtained “xL” and the measurement result “x _i ” by the estimation coefficient β and subtracts it from 25 (Line 3 reduces the hematocrit value Hct = 25%). Therefore, the hematocrit value Hct is obtained. That is, the hematocrit value Hct = 25−β (x _i −xL).

  In the present embodiment, each of Line1, Line2, and Line3 is represented by a linear function, but is not limited to a linear function, and may be represented by other functions such as a quadratic function and a cubic function. Although linear approximation is used for extrapolation processing and interpolation (interpolation) processing when obtaining the hematocrit value Hct, other approximations may be used instead of the linear approximation.

  Each of the map data in FIGS. 16 and 17 is not limited to the three relational lines Line1, Line2, and Line3, and may include four or more relational lines. Further, the map data is not limited to two dimensions (here, the transmitted light amount TDC and the average frequency fm or the first moment 1stM), for example, a three-dimensional map using the transmitted light amount TDC, the average frequency fm, and the hematocrit value Hct as parameters. It may be a table.

(effect)
Next, the effect of the fluid evaluation apparatus 100 according to the present embodiment will be described with reference to FIG. FIG. 19A is an example of an estimation result when the hematocrit value is estimated only from the transmitted light amount. FIG. 19B is an example of an estimation result when the hematocrit value is estimated from the transmitted light amount and the average frequency. The estimation result shown in FIG. 13 is an estimation result when the blood flow (ie, hematocrit value Hct) is kept constant and the flow rate is changed.

  When the hematocrit value Hct is estimated only from the transmitted light amount TDC, the hematocrit value Hct increases as the flow velocity increases, as shown in FIG. That is, if the hematocrit value Hct is estimated from only the transmitted light amount TDC, the error increases as the flow velocity increases.

  On the other hand, when the hematocrit value Hct is estimated from the transmitted light amount TDC and the average frequency fm as in this embodiment, the hematocrit value Hct is constant without depending on the flow velocity, as shown in FIG. That is, according to the fluid evaluation apparatus 100, the hematocrit value Hct can be obtained with high accuracy without being affected by the blood flow velocity.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the scope or spirit of the invention that can be read from the claims and the entire specification. A method, a computer program, and a recording medium are also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 11 ... Semiconductor laser, 12 ... Laser drive part, 21, 31 ... Light receiving element, 22, 32 ... IV converter, 23 ... LPF amplifier, 24, 34 ... A / D converter, 25 ... LPF calculating part, 26 ... 2D flow estimation unit, 33 ... BPF amplifier, 35 ... Frequency analysis unit, 51 ... LED, 52 ... LED drive unit, 100, 200, 300 ... Fluid evaluation device

Claims (7)

A light source that irradiates light to a measurement target in which a fluid flows inside;
A light receiving unit that receives scattered light from the object to be measured of the irradiated light and outputs a light reception signal corresponding to the received scattered light;
A first information output unit that outputs received light amount information that is information relating to the received light amount of the light receiving unit included in the output received light signal;
Correspondence that defines the relationship between the information based on the beat signal resulting from the Doppler shift of the light, the output light reception amount information, and the information based on the light reception amount information and the beat signal, included in the output light reception signal A second information output unit that outputs information related to at least one of the flow rate of the fluid and the flow rate of the fluid based on the relationship information;
Equipped with a,
The correspondence information corresponds to a plurality of values of parameters relating to the flow rate of the fluid or the flow velocity of the fluid, respectively, in a coordinate system having the information based on the received light amount information and the beat signal as axes, and the received light amount It is a plurality of relationship lines that define the relationship between information and information based on the beat signal
A fluid evaluation apparatus. The second information output unit includes at least one of the plurality of relational lines and the point indicated by the information based on the output light reception amount information and the beat signal included in the output light reception signal in the coordinate system. Output information related to at least one of the flow rate of the fluid and the flow rate of the fluid by specifying a parameter value relating to the flow rate of the fluid or the flow rate of the fluid corresponding to the point based on the relationship line of The fluid evaluation apparatus according to claim 1 . The light receiving section receives a first light receiving section that receives the scattered light that has passed through the object to be measured among the scattered light, and a second light receiving section that receives the scattered light reflected by the target to be measured among the scattered light. And having
The first information output unit outputs received light amount information that is information on the received light amount of the first light receiving unit included in the light reception signal output from the first light receiving unit,
The second information output unit includes the fluid based on the information based on the beat signal included in the light reception signal output from the second light receiving unit, the output light reception amount information, and the correspondence information. flow and fluid evaluation apparatus according to claim 1 or 2, characterized in that for outputting information regarding at least one of the flow velocity of the fluid. The light source includes a first light source that emits laser light, and a second light source that emits light different from the laser light,
The light receiving unit receives first scattered light from the measurement target of laser light emitted from the first light source, and receives a light reception signal including the beat signal according to the received first scattered light. output, either the said light emitted from the second light source receives the second scattered light from the object to be measured, according to claim 1 to 3, characterized in that for outputting a light reception signal including the received light amount information The fluid evaluation apparatus according to claim 1. A light source for irradiating light to a measurement target with fluid flowing therein, and scattered light from the measurement target of the irradiated light is received, and a light reception signal corresponding to the received scattered light is output. A fluid evaluation method in a fluid evaluation device comprising a light receiving unit,
A first information output step of outputting received light amount information which is information related to the received light amount of the light receiving unit included in the output received light signal;
Correspondence that defines the relationship between the information based on the beat signal resulting from the Doppler shift of the light, the output light reception amount information, and the information based on the light reception amount information and the beat signal, included in the output light reception signal A second information output step for outputting information on at least one of the flow rate of the fluid and the flow velocity of the fluid based on the relationship information;
Equipped with a,
The correspondence information corresponds to a plurality of values of parameters relating to the flow rate of the fluid or the flow velocity of the fluid, respectively, in a coordinate system having the information based on the received light amount information and the beat signal as axes, and the received light amount It is a plurality of relationship lines that define the relationship between information and information based on the beat signal
The fluid evaluation method characterized by the above-mentioned. A light source for irradiating light to a measurement target in which fluid flows inside, and scattered light from the measurement target of the irradiated light is received, and a light reception signal corresponding to the received scattered light is output. A computer mounted on a fluid evaluation apparatus including a light receiving unit,
A first information output unit that outputs received light amount information that is information relating to the received light amount of the light receiving unit included in the output received light signal;
Correspondence that defines the relationship between the information based on the beat signal resulting from the Doppler shift of the light, the output light reception amount information, and the information based on the light reception amount information and the beat signal included in the output light reception signal A second information output unit that outputs information on at least one of the flow rate of the fluid and the flow rate of the fluid based on the relationship information;
To function as,
The correspondence information corresponds to a plurality of values of parameters relating to the flow rate of the fluid or the flow velocity of the fluid, respectively, in a coordinate system having the information based on the received light amount information and the beat signal as axes, and the received light amount It is a plurality of relationship lines that define the relationship between information and information based on the beat signal
A computer program characterized by the above. A recording medium storing the computer program according to claim 6 .

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