JP2019076539A - Blood flow analysis device, blood flow analysis method, and program - Google Patents

Abstract

To accurately analyze a fluid by reducing influence of shot noise on a detection signal.SOLUTION: A blood flow analysis device comprises: a signal processing unit which performs filtering on a detection signal expressing the strength of laser light having passed through a blood vessel, so that the component of a frequency within a predetermined processing zone is suppressed in comparison with the component of a frequency lower than a frequency at the lower end of the processing band; and an arithmetic processing unit which generates information about a blood flow in the blood vessel, from the filtered signal.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technology for generating information on fluid such as blood.

  Techniques for measuring blood flow in a living body have been conventionally proposed. For example, in Patent Document 1, light passing through a blood vessel of a living body is received by a light receiving element, and the product of the power spectrum of a detection signal representing the received light intensity and each numerical value of frequency is integrated within a range of 200 Hz to 15 kHz. The structure which measures the blood flow rate of a biological body by doing is disclosed.

JP, 2012-210321, A

  By the way, shot noise that is evenly distributed over a wide range on the frequency axis may inevitably occur in the detection signal. Under the technique of Patent Document 1, the product of the power spectrum of the detection signal and each numerical value of the frequency is integrated, so that the shot noise is emphasized in the higher frequency range. Therefore, there is a problem that blood flow can not be measured with high accuracy unless the integration range is strictly selected. Although the above description focuses on the measurement of blood flow, similar problems are assumed in various situations in which various fluids represented by blood are analyzed. In consideration of the above circumstances, a preferred embodiment of the present invention aims to reduce the influence of shot noise in a detection signal and analyze a fluid such as blood with high accuracy.

  In order to solve the above problems, in the blood flow analysis device according to a preferred aspect of the present invention, a component of a frequency within a predetermined processing band is processed with respect to a detection signal representing the intensity of laser light having passed through a blood vessel. A signal processing unit that performs filtering so as to be suppressed in comparison with components at frequencies lower than the frequency at the lower end of the band, and computation that generates information on blood flow in the blood vessel from the signal after the filtering And a processing unit. In the above aspect, the filtering process is performed on the detection signal so that the component of the frequency in the predetermined processing band is suppressed as compared with the component of the frequency lower than the frequency at the lower end of the processing band. The influence of shot noise, which is particularly dominant on the side, is reduced. Therefore, it is possible to generate information on blood flow with high accuracy.

  In a preferred aspect of the present invention, the arithmetic processing unit integrates information on the blood flow by integrating a product of the intensity of each frequency in the intensity spectrum of the filtered signal and the frequency for a predetermined calculation range. And the processing band and the calculation range partially overlap each other. In the configuration in which the product (weighted intensity) of the intensity of each frequency in the intensity spectrum and the frequency is integrated, shot noise on the high frequency side in the intensity spectrum is emphasized. According to a preferred aspect of the present invention in which the processing band and the calculation range partially overlap with each other, the calculation range is sufficiently set to include a part of the high frequency side band in which the shot noise is dominant in the detection signal. Even if it is widely secured, the influence of the shot noise on the high frequency side is reduced. Therefore, it is possible to generate information on blood flow with high accuracy.

  In a preferred aspect of the present invention, the signal processing unit performs the filtering process on the detection signal such that a higher frequency component is suppressed in the predetermined processing band. In the above aspect, the filtering process is performed on the detection signal so that the higher the frequency is within the predetermined processing band, the effect of shot noise that is particularly dominant on the high frequency side is reduced. Can be realized more effectively.

  In a preferred aspect of the present invention, the calculation range is a range between a first frequency and a second frequency above the first frequency, and the frequency at the lower end of the processing band is below the second frequency. In the above aspect, since the frequency at the lower end of the processing band is lower than the second frequency which is the upper end of the calculation range, the high frequency side is set even when the second frequency is set high to ensure a sufficient calculation range. The impact of shot noise on the Therefore, it is possible to generate information on blood flow with high accuracy.

  In a preferred aspect of the present invention, the lower end frequency of the processing band exceeds the frequency higher than the first frequency by 1/2 of the calculation range. In the above aspect, since the frequency at the lower end of the processing band exceeds the frequency higher than the first frequency by 1/2 of the calculation range, the influence of the shot noise in the detection signal is reduced, and the fluid such as blood is highly accurate. It is possible to more effectively realize the above-mentioned effect of analyzing into.

  In a preferred aspect of the present invention, the lower end frequency of the processing band is lower than the higher frequency than the first frequency by 3⁄4 of the calculation range. In the above aspect, since the frequency at the lower end of the processing band falls below the frequency higher than the first frequency by 3⁄4 of the calculation range, the effect of shot noise in the detection signal is reduced, and the fluid such as blood is highly accurate. It is possible to more effectively realize the above-mentioned effect of analyzing into.

  In a preferred aspect of the present invention, the lower end frequency of the processing band is higher than the first frequency by 2/3 of the calculation range. In the above aspect, since the frequency at the lower end of the processing band is higher than the first frequency by 2/3 of the calculation range, the influence of shot noise in the detection signal is reduced, and the fluid such as blood is highly accurate. It is possible to more effectively realize the above-mentioned effect of analyzing into.

  In a preferred aspect of the present invention, the processing band is a range in which the suppression of the detection signal by the signal processing unit is 6 dB / Oct or more. In the above aspect, the detection signal is suppressed with the frequency characteristic of 6 dB / Oct in the processing band. Therefore, it is possible to effectively reduce the effect of shot noise that is emphasized due to the frequency-based intensity of the intensity spectrum being multiplied by the frequency.

  In the blood flow analysis method according to a preferred aspect of the present invention, the frequency component in the predetermined processing band is lower than the frequency at the lower end of the processing band with respect to the detection signal representing the intensity of the laser light passing through the blood vessel. The filter processing is performed to be suppressed as compared with the components of the above, and the information on the blood flow in the blood vessel is generated from the filtered signal. In the above aspect, the filtering process is performed on the detection signal so that the component of the frequency in the predetermined processing band is suppressed as compared with the component of the frequency lower than the frequency at the lower end of the processing band. The influence of shot noise, which is particularly dominant on the side, is reduced. Therefore, it is possible to generate information on blood flow with high accuracy.

  A program according to a preferred aspect of the present invention is that a component of a frequency within a predetermined processing band is lower than a frequency of a lower end of the processing band with respect to a detection signal representing the intensity of laser light having passed through a blood vessel. A computer is functioned as a signal processing unit that executes a filtering process so as to be suppressed by comparison and an arithmetic processing unit that generates information on the blood flow in the blood vessel from the signal after the filtering process. In the above aspect, the filtering process is performed on the detection signal so that the component of the frequency in the predetermined processing band is suppressed as compared with the component of the frequency lower than the frequency at the lower end of the processing band. The influence of shot noise, which is particularly dominant on the side, is reduced. Therefore, it is possible to generate information on blood flow with high accuracy.

It is a side view of the blood flow analysis device concerning a 1st embodiment of the present invention. It is the block diagram which paid its attention to the function of a blood flow analysis device. It is the block diagram which paid its attention to the light-receiving part and the output circuit. 5 is a flowchart illustrating the operation of the arithmetic processing unit. It is a frequency characteristic of the filter processing by a signal processing part. It is explanatory drawing which paid its attention to the frequency of the lower end of a process zone. It is an intensity spectrum of a detection signal. It is explanatory drawing of the problem of the shot noise in a comparative example. It is explanatory drawing of the effect by 1st Embodiment. It is a figure for demonstrating the method to specify the lower end frequency of a process zone. It is a figure which shows the example which calculates | requires the lower end frequency of a process zone. It is the block diagram which paid its attention to the light-receiving part and output circuit in 2nd Embodiment. It is a schematic diagram which shows the usage example of the blood flow analyzer which concerns on 3rd Embodiment. It is a schematic diagram which shows the other usage example of the blood-flow analysis apparatus which concerns on 3rd Embodiment. It is a graph which shows the frequency spectrum in the supplement regarding the frequency of the lower end of a process zone. It is a graph which shows the frequency spectrum in the supplement regarding the frequency of the lower end of a process zone. It is a graph which shows the frequency spectrum in the supplement regarding the frequency of the lower end of a process zone. It is the block diagram which paid its attention to the light-receiving part and output circuit in a modification. It is a frequency characteristic of the filter process by the signal processing part in a modification. It is a frequency characteristic of the filter process by the signal processing part in a modification. It is a block diagram of the blood-flow analysis apparatus in a modification. It is a block diagram of the blood-flow analysis apparatus in a modification. It is a block diagram of the blood-flow analysis apparatus in a modification.

First Embodiment
FIG. 1 is a side view of a blood flow analysis device 100 according to a first embodiment of the present invention. The blood flow analysis device 100 according to the first embodiment is a biometric device that non-invasively generates information (hereinafter referred to as “blood flow information”) regarding blood flow in a blood vessel of a subject (exemplary living body). It is mounted on a site (hereinafter referred to as “measurement site”) M to be measured in the body. The blood flow analysis device 100 according to the first embodiment is, as illustrated in FIG. 1, a wristwatch-type portable device including a housing 12 and a belt 14. That is, by winding the belt 14 around the wrist, which is an example of the measurement site M, the blood flow analysis device 100 is attached to the wrist of the subject. The blood flow information of the first embodiment generates the blood flow velocity of the subject (for example, the distance that the red blood cells move in the artery within a unit time) as the blood flow information.

  FIG. 2 is a block diagram focusing on the function of the blood flow analysis device 100. As illustrated in FIG. 2, the blood flow analysis device 100 according to the first embodiment includes a control device 20, a storage device 22, a display device 24, and a detection device 30. The control device 20 and the storage device 22 are installed inside the housing 12. As illustrated in FIG. 1, the display device 24 (for example, a liquid crystal display panel) is installed, for example, on the surface of the housing 12 opposite to the measurement site M, and various images including measurement results are Display under control.

  The detection device 30 of FIG. 2 is an optical sensor module that generates a detection signal Sd according to the state of the measurement site M. As illustrated in FIG. 2, the detection device 30 according to the first embodiment includes a light emitting unit 31, a light receiving unit 32, a drive circuit 33, and an output circuit 34. The light emitting unit 31 and the light receiving unit 32 are installed, for example, at a position facing the measurement site M (typically, a surface in contact with the measurement site M) in the housing 12. It is also possible to install one or both of the drive circuit 33 and the output circuit 34 as an external circuit separate from the detection device 30.

  The light emitting unit 31 is a light source for irradiating the measurement site M with light. The light emitting unit 31 of the first embodiment irradiates the measurement site M with a narrow band coherent laser beam. For example, a light emitting element such as a VCSEL (Vertical Cavity Surface Emitting LASER) that emits laser light due to resonance in a resonator is suitably used as the light emitting unit 31. The light emitting unit 31 according to the first embodiment irradiates the measurement site M, for example, light of a predetermined wavelength λ (λ = 800 nm to 1300 nm) in the near infrared range. The drive circuit 33 of FIG. 2 causes the light emitting unit 31 to emit light under the control of the control device 20. It is also possible to use a plurality of light emitting elements emitting light of different wavelengths as the light emitting unit 31. Further, the wavelength λ of the light emitted from the light emitting unit 31 is not limited to the near infrared region.

  The light emitted from the light emitting unit 31 and incident on the measurement site M repeats reflection and scattering inside the measurement site M, and then emits toward the housing 12 side to reach the light receiving unit 32. Specifically, light passing through a blood vessel such as an artery (for example, a radial artery or an ulnar artery) present inside the measurement site M and the blood in the blood vessel reaches the light receiving unit 32. The light receiving unit 32 receives light coming from the measurement site M. The light receiving unit 32 according to the first embodiment generates a detection signal Sa representing the intensity of light arriving from the measurement site M. For example, as illustrated in FIG. 3, a light receiving element 321 such as a photodiode (PD: Photo Diode) that generates a charge according to the light receiving intensity is suitably used as the light receiving unit 32. The detection signal Sa is an analog current signal according to the light reception intensity from the measurement site M. As understood from the above description, the detection device 30 according to the first embodiment is a reflective optical sensor in which the light emitting unit 31 and the light receiving unit 32 are located on one side of the measurement site M.

  The light reaching the light receiving unit 32 is reflected by the component reflected by the stationary tissue (static tissue) inside the measurement site M and the object (typically red blood cells) moving in the artery inside the measurement site M Contains an ingredient. The frequency of light does not change before and after reflection from stationary tissue, but before and after reflection from red blood cells, the amount of change (hereinafter referred to as “frequency shift amount”) Δf proportional to the moving velocity of red blood cells (that is, blood flow velocity) Only the frequency of light changes. That is, the light passing through the measurement site M and reaching the light receiving unit 32 contains a component that is shifted (frequency shift) by the frequency shift amount Δf with respect to the frequency of the light emitted by the light emitting unit 31. The detection signal Sa of the first embodiment is a light beat signal in which the frequency shift due to the blood flow inside the measurement site M is reflected.

  The output circuit 34 of FIG. 2 generates a detection signal Sd from the detection signal Sa generated by the light receiving unit 32. The detection signal Sd is a digital voltage signal corresponding to the intensity of the light received by the light receiver 32. As described above, the light irradiated to the measurement site M passes through blood vessels and blood inside the measurement site M and then reaches the light receiving unit 32. Therefore, the detection signal Sd can be reworded as a signal representing the intensity of light passing through the subject's blood.

  FIG. 3 is a configuration diagram of the light receiving unit 32 and the output circuit 34 in the first embodiment. As illustrated in FIG. 3, the output circuit 34 according to the first embodiment includes a signal amplification unit 51, a signal processing unit 52, and an A / D conversion unit 53. The signal amplification unit 51 converts the detection signal Sa supplied from the light receiving unit 32 into a voltage signal and amplifies it to generate a detection signal Sb. For example, the signal amplification unit 51 includes a current / voltage conversion circuit that converts the detection signal Sa into a voltage signal, and a voltage amplification circuit that amplifies the voltage signal.

  The signal processing unit 52 generates a detection signal Sc by performing a predetermined filter process on the detection signal Sb supplied from the signal amplification unit 51 (that is, the signal representing the intensity of the laser beam passing through the blood vessel). . A specific example of the filtering process performed by the signal processing unit 52 will be described later. The A / D conversion unit 53 converts the analog detection signal Sc generated by the signal processing unit 52 into a digital detection signal Sd at a predetermined sampling frequency Fs. As understood from the above description, the detection signal S (Sa, Sb, Sc, Sd) is a light beat signal in which the frequency shift due to the blood flow inside the measurement site M is reflected.

  The control device 20 of FIG. 2 is an arithmetic processing device such as a central processing unit (CPU) or a field-programmable gate array (FPGA), and controls the entire blood flow analysis device 100. The storage device 22 is formed of, for example, a non-volatile semiconductor memory, and stores a program executed by the control device 20 and various data used by the control device 20. A configuration in which the functions of control device 20 are distributed to a plurality of integrated circuits, or a configuration in which some or all of the functions of control device 20 are realized by dedicated electronic circuits may also be employed. Further, although the control device 20 and the storage device 22 are illustrated as separate elements in FIG. 2, the control device 20 including the storage device 22 can be realized by, for example, an application specific integrated circuit (ASIC) or the like.

  The control device 20 according to the first embodiment functions as an arithmetic processing unit 61 by executing a program (application program) stored in the storage device 22. The arithmetic processing unit 61 generates blood flow information of the subject from the detection signal Sd generated by the output circuit 34 of the detection device 30 (that is, the signal processed by the signal processing unit 52). As described above, the arithmetic processing unit 61 of the first embodiment calculates the blood flow velocity in the artery inside the measurement region M as blood flow information.

  FIG. 4 is a flowchart of processing for the arithmetic processing unit 61 to calculate the blood flow velocity. For example, the process of FIG. 4 is executed at predetermined time intervals. When the process of FIG. 4 is started, the arithmetic processing unit 61 calculates an intensity spectrum X from the detection signal Sd (S1). The intensity spectrum X is a distribution of the intensity (power or amplitude) P (f) of the signal component corresponding to each frequency f on the frequency axis in the detection signal Sd. For calculating the intensity spectrum X, known frequency analysis such as discrete Fourier transform may be arbitrarily adopted.

  The arithmetic processing unit 61 calculates the blood flow velocity V (blood flow information) from the intensity spectrum X of the detection signal Sd (S2). Specifically, the arithmetic processing unit 61 of the first embodiment calculates the blood flow index F (so-called FLOW value) by the calculation of the following equation (1a), and cuts separately estimated for the blood vessel of the measurement site M. The blood flow velocity V (V = F / A) is calculated by dividing the blood flow index F by the area A. The blood flow index F is an index of the blood flow of the measurement site M (ie, the volume of blood moving in the artery within a unit time). The arithmetic processing unit 61 can also generate the average value of the plurality of blood flow velocities V calculated for different points in time as blood flow information.

数式(1a)は、検出信号Ｓdの各周波数ｆと当該周波数ｆにおける強度Ｐ(f)とから血流量指標Ｆを算定するための演算式である。記号＜Ｉ^２＞は、検出信号Ｓdの全帯域にわたる平均強度、または、強度スペクトルＸのうち０ｋＨｚにおける強度Ｐ(0)（すなわち直流成分の信号強度）である。

Formula (1a) is an arithmetic expression for calculating the blood flow index F from each frequency f of the detection signal Sd and the intensity P (f) at the frequency f. The symbol <I ² > is the average intensity over the entire band of the detection signal Sd, or the intensity P (0) at 0 kHz in the intensity spectrum X (that is, the signal intensity of the DC component).

  As understood from Equation (1a), the arithmetic processing unit 61 of the first embodiment calculates the product (f × P (f)) of the intensity P (f) of each frequency f in the intensity spectrum X and the frequency f. The blood flow index F is calculated by integrating for a predetermined range (hereinafter referred to as "calculation range"). The product (f × P (f)) of the intensity P (f) of the intensity spectrum X and the frequency f means an intensity weighted by the frequency f (hereinafter referred to as “weighted intensity”). The calculation range corresponds to the integral range of the weighted intensity, and is a predetermined frequency on the frequency axis (hereinafter referred to as "lower end frequency") f1 and a predetermined frequency (hereinafter referred to as "upper end frequency") f2 higher than the lower end frequency f1. Between them. The lower end frequency f1 is an example of the first frequency, and the upper end frequency f2 is an example of the second frequency. As understood from the above description, the arithmetic processing unit 61 of the first embodiment generates blood flow information (blood flow velocity V) from the intensity spectrum X of the detection signal Sd generated by the detection device 30. The display device 24 of FIG. 2 displays the blood flow information (blood flow velocity V) generated by the arithmetic processing unit 61.

  The second index calculating unit 52 may calculate the blood flow index F by the calculation of the following formula (1b) in which the integral of the formula (1a) is replaced with the sum (Σ).

  FIG. 5 is an explanatory diagram of the filtering process performed by the signal processing unit 52 according to the first embodiment. Specifically, FIG. 5 exemplifies the frequency characteristic of the filtering process performed by the signal processing unit 52 (that is, the distribution of the gain in the frequency domain). As understood from FIG. 5, the signal processing unit 52 has a component of the frequency fH in a predetermined frequency band (hereinafter referred to as “processing band”) B and a component of the frequency fL lower than the frequency Fx at the lower end of the processing band B. Perform filtering to be suppressed by comparison. Specifically, the filtering process is performed such that the higher the frequency in the processing band B, the more the component is suppressed. The signal processing unit 52 according to the first embodiment executes the filtering process in which the gain is continuously reduced so that the higher the frequency in the processing band B, the more the component is suppressed. For example, a low pass filter or a band pass filter is preferably used as the signal processing unit 52. Specifically, the signal processing unit 52 is configured by combining a predetermined number (one or more) of primary analog filter circuits.

  The processing band B is a range in which the degree of suppression of the detection signal Sb by the signal processing unit 52 (that is, the frequency characteristic of the filter processing) is 6 dB / Oct (octave) or more. It is a range. That is, in the processing band B, the component of each frequency f which comprises the detection signal S is suppressed by the degree more than the degree (6 dB / Oct) proportional to the frequency f. For example, assuming that the filtering frequency characteristic is set to 6 dB / Oct in the processing band B, the gain at a specific frequency m × f (m is a natural number) in the processing band B is in the processing band B. Is set to 1 / m of the gain at frequency f. The frequency Fx corresponds to the lower end of a range in which the degree of suppression of the detection signal Sb is 6 dB / Oct or more (that is, the processing band B).

  As illustrated in FIG. 5, the calculation range R applied to the calculation of the blood flow index F and the processing band B of the filtering process by the signal processing unit 52 partially overlap each other. Specifically, the portion on the high frequency side in the calculation range R and the portion on the low frequency side in the processing band B overlap each other. That is, the frequency Fx at the lower end of the processing band B is higher than the lower end frequency f1 of the calculation range R and equal to or less than the upper end frequency f2 of the calculation range R. In FIG. 5, the case where the frequency Fx at the lower end of the processing band B is lower than the upper end frequency f2 of the calculation range R is illustrated.

  FIG. 6 is an explanatory view focusing on the frequency Fx at the lower end of the processing band B. Specifically, the frequency Fx is higher than the lower frequency f1 by 1⁄2 of the calculation range R and lower than the upper frequency f2. Preferably, the frequency Fx is higher than the frequency higher than the lower end frequency f1 by 1/2 of the calculation range R and is lower than the frequency higher than the lower end frequency f1 by 3/4 of the calculation range R. FIG. 6 exemplifies a case in which a frequency higher than the first frequency by 2/3 of the calculation range R is set to the frequency Fx.

  Here, the upper end frequency f2 needs to be equal to or less than the Nyquist frequency (Fs / 2) of the A / D conversion unit 53. That is, the upper end frequency f2 of the calculation range R is set to a numerical value between the frequency Fx at the lower end of the processing band B and the Nyquist frequency (Fs / 2) of the A / D converter 53 (Fx ≦ f2 ≦ Fs / 2). For example, assuming that the frequency Fx of the processing band B is 45 kHz and the A / D conversion unit 53 operates at the sampling frequency Fs of 100 kHz, the upper end frequency f2 is 45 kHz (= Fx) or more and 50 kHz (= Fs / = Fs). 2) It is set to a suitable numerical value (for example, 50 kHz) within the following range. On the other hand, the lower end frequency f1 is set to a numerical value (for example, about 200 Hz) sufficiently smaller than the upper end frequency f2. As understood from the above description, the arithmetic processing unit 61 according to the first embodiment determines the weighted intensity (f × P (algorithm The blood flow index F is calculated by integrating f).

  The intensity spectrum X of the detection signal Sd is shown in FIG. Shot noise which is inevitably generated due to circuit elements such as the light receiving unit 32 and the output circuit 34 is included in the detection signal Sd. Shot noise is white noise that is evenly distributed over a wide range of frequency f. On the other hand, the intensity of the signal component derived from the light (that is, the original analysis target) that has passed through the measurement site M tends to be lower toward the high frequency side. Therefore, as can be understood from FIG. 7, in the frequency band N on the high frequency side of the intensity spectrum X, the influence of the shot noise on the light passing through the measurement site M becomes dominant. The frequency (hereinafter referred to as “high noise frequency”) Fn at the lower end of the frequency band N in which the influence of shot noise is dominant may fluctuate depending on the state of blood vessels or blood at the measurement site M.

  FIGS. 8 and 9 show the distribution of weighted intensity (f × P (f)) on the frequency axis. FIG. 8 is a distribution of weighted intensities in a configuration in which the filter processing by the signal processing unit 52 is omitted (hereinafter, referred to as “contrast example”). FIG. 9 is a distribution of weighted intensities in the first embodiment in which the signal processing unit 52 executes filter processing for suppressing signal components in the processing band B.

  Now, from the viewpoint of measuring the blood flow index F with high accuracy by the calculation of the equation (1a), it is necessary to secure a wide calculation range R. That is, it is required to set the upper end frequency f2 high. On the other hand, by multiplying the intensity P (f) of the intensity spectrum X by the frequency f, in the comparative example, shot noise on the high frequency side in the intensity spectrum X is emphasized as understood from FIG. Therefore, in the configuration in which the upper end frequency f2 is set high, shot noise becomes dominant on the high frequency side of the calculation range R, and as a result, the highly accurate measurement of the blood flow index F is inhibited. When the upper end frequency f2 is set to a low value in order to solve the above problem, the calculation range R becomes excessively narrow, and as a result, the accuracy of measurement of the blood flow index F may rather decrease. As understood from the above description, in order to constantly measure the blood flow index F with high accuracy, it is necessary to change the upper end frequency f2 in accordance with the state of the blood vessel or blood at the measurement site M. For example, in the situation where the high noise frequency Fn is high, the upper end frequency f2 is set high, and in the situation where the high noise frequency Fn is low, the upper end frequency f2 is set low.

  In contrast to the comparative example described above, in the first embodiment, the signal component in the processing band B partially overlapping the calculation range R in the detection signal Sb is suppressed by the filter processing. That is, as understood from FIG. 9, regardless of the high end of the upper end frequency f 2, in the calculation range R, the effect of shot noise to be emphasized by the multiplication of the frequency f with the intensity P (f) is reduced by filtering Be done. Therefore, for example, even in a configuration in which the upper end frequency f2 is set high to ensure that the calculation range R is sufficiently secured, the influence of the shot noise of the detection signal Sb can be reduced to measure the blood flow index F with high accuracy. It is possible. In addition, since the above-described process of changing the upper end frequency f2 according to the state of the blood vessel or blood at the measurement site M is unnecessary, there is an advantage that the load for generating blood flow information is reduced.

  Next, the conditions which hold in the above-mentioned situation where operation range R and processing zone B mutually overlap mutually are explained. Now, it is assumed that the range of the blood flow velocity V on the specification that can be measured by the blood flow analysis device 100 is from the minimum value V1 to the maximum value V2. As described above, the frequency shift amount Δf caused by the light reflection from red blood cells in blood is proportional to the blood flow velocity V. Specifically, the frequency shift amount Δf is expressed by the following equation (2).

数式(2)の記号λは発光部３１が測定部位Ｍに照射する光の波長であり、記号θは、発光部３１から測定部位Ｍに入射する光の入射角である。実際の血流解析装置１００を想定すると、波長λは発光部３１が出射する光の波長として既知であり、入射角θは測定部位Ｍの表面に対する発光部３１の光軸の角度から確定される。また、記号ｎは測定部位Ｍ（特に動脈および血液）の屈折率であり、概略的には１．３３〜１．３４の範囲内の既知の数値である。血流解析装置１００による測定が想定される血流速度Ｖの最大値Ｖ2を以上の各定数（λ，θ，ｎ）とともに数式(2)に代入すると、血流解析装置１００が測定可能な範囲内で最大の周波数シフト量Δｆ2を得ることができる。

The symbol λ in Equation (2) is the wavelength of light emitted by the light emitting unit 31 to the measurement site M, and the symbol θ is the incident angle of light incident on the measurement site M from the light emitting unit 31. Assuming an actual blood flow analysis apparatus 100, the wavelength λ is known as the wavelength of light emitted by the light emitting unit 31, and the incident angle θ is determined from the angle of the optical axis of the light emitting unit 31 with respect to the surface of the measurement site M . The symbol n is the refractive index of the measurement site M (particularly, artery and blood), and is generally a known value within the range of 1.33 to 1.34. If the maximum value V2 of the blood flow velocity V assumed to be measured by the blood flow analysis device 100 is substituted into the equation (2) together with the above constants (λ, θ, n), the range in which the blood flow analysis device 100 can be measured Among them, the maximum frequency shift amount Δf2 can be obtained.

  In addition, the maximum value V2 of the blood flow velocity V can be measured by a flowmeter using ultrasonic waves. In the case of measuring blood flow in an artery, for example, the maximum value V2 of the blood flow velocity V is 0.8 m / sec or more and 1.2 m / sec or less, and in the case of measuring blood flow in capillaries. For example, it is known that the maximum value V2 of the blood flow velocity V is 2 mm / sec or more and 12 mm / sec or less.

  Next, a method of determining the lower end frequency Fx of the processing band B will be described. FIG. 10 is a diagram for explaining a method of specifying the lower end frequency Fx of the processing band B. As illustrated in FIG. 10, for example, a sine wave input signal is input from the terminal I of the spectrum analyzer SA to the signal processing unit 52, and the power or voltage from the signal processing unit 52 is input to the terminal A as an output signal. Here, the frequency characteristics as illustrated in FIGS. 5 to 9 can be obtained by changing the frequency of the input signal and acquiring the output signal for each frequency. The lower end frequency Fx of the processing band B is a frequency at which the output signal decreases as the frequency of the input signal increases. Specifically, as shown in FIG. 11, the frequency at which the output signal decreases by 3 dB as the frequency of the input signal increases is taken as the lower end frequency Fx of the processing band B. Although FIG. 10 illustrates the case where the frequency characteristic is obtained from the relationship between the input signal and the output signal of the signal processing unit 52, the input signal may be input to the signal amplification unit 51. Also, an output signal may be acquired from an element (for example, the A / D conversion unit 53) in the subsequent stage.

  Moreover, in order to obtain more blood flow information, it is desirable to obtain blood flow information up to the maximum value V2 of the blood flow velocity V. In other words, it is desirable that the upper end frequency f2 is equal to or higher than the frequency shift amount Δf2 (f2 Δ Δf2). In this case, if it is confirmed that the frequency shift amount Δf2 exceeds the frequency Fx (Fx <Δf2), the upper end frequency f2 exceeds the frequency Fx because the upper end frequency f2 is equal to or higher than the frequency shift amount Δf2 (Δf2 ≦ f2) Fx <f2). When the upper end frequency f2 exceeds the frequency Fx (Fx <f2), the condition that the calculation range R and the processing band B partially overlap is established.

Second Embodiment
A second embodiment of the present invention will be described. In addition, about the element which an operation | movement or a function is the same as 1st Embodiment in each form illustrated below, the code | symbol used by description of 1st Embodiment is diverted and detailed description of each is abbreviate | omitted suitably.

  FIG. 12 is a configuration diagram of the light receiving unit 32 and the output circuit 34 in the second embodiment. As illustrated in FIG. 12, the light receiving unit 32 of the second embodiment is configured to include light receiving elements 321 and light receiving elements 322 disposed at different positions. The light receiving element 321 generates a detection signal Sa1 according to the light reception intensity from the measurement site M, and the light receiving element 322 generates a detection signal Sa2 according to the light reception intensity from the measurement site M.

  The signal amplification unit 51 of the second embodiment generates a detection signal Sb corresponding to the difference between the detection signal Sa1 generated by the light receiving element 321 and the detection signal Sa2 generated by the light receiving element 322. Therefore, the detection signal Sb is generated in which the stationary noise contained in common between the detection signal Sa1 and the detection signal Sa2 is reduced. For example, a differential amplifier circuit is suitably used as the signal amplification unit 51. The signal processing unit 52 performs the same filtering process as that of the first embodiment on the detection signal Sb supplied from the signal amplification unit 51. The functions and actions of the other elements are the same as in the first embodiment.

  Also in the second embodiment, the same effect as that of the first embodiment is realized. In the second embodiment, a detection signal Sb corresponding to the difference between the detection signal Sa1 generated by the light receiving element 321 and the detection signal Sa2 generated by the light receiving element 322 is generated. That is, the detection signal Sb having a high SN ratio is generated with reduced noise contained in common between the detection signal Sa1 and the detection signal Sa2. Therefore, the effect that blood flow information can be generated with high accuracy is particularly remarkable.

Third Embodiment
FIG. 13 is a schematic view showing a usage example of the blood flow analysis device 100 according to the third embodiment. As illustrated in FIG. 13, the blood flow analysis device 100 includes a detection unit 71 and a display unit 72 which are configured separately from each other. The detection unit 71 includes the detection device 30 illustrated in each of the embodiments described above. FIG. 13 illustrates a detection unit 71 mounted on the upper arm of a subject. As illustrated in FIG. 14, a detection unit 71 configured to be worn on the subject's wrist is also suitable.

  The display unit 72 includes the display 24 illustrated in each of the above-described embodiments. For example, an information terminal such as a mobile phone or a smartphone is a preferred example of the display unit 72. However, the specific form of the display unit 72 is arbitrary. For example, a wristwatch-type information terminal portable by the subject or a dedicated information terminal of the blood flow analysis apparatus 100 may be used as the display unit 72.

  The arithmetic processing unit 61 is mounted on the display unit 72, for example. The detection signal Sd generated by the detection device 30 of the detection unit 71 is transmitted to the display unit 72 in a wired or wireless manner. The arithmetic processing unit of the display unit 72 calculates blood flow information from the detection signal Sd and displays it on the display device 24.

  The arithmetic processing unit 61 may be mounted on the detection unit 71. The arithmetic processing unit 61 calculates blood flow information from the detection signal Sd generated by the detection device 30, and transmits data for displaying the blood flow information to the display unit 72 in a wired or wireless manner. The display device 24 of the display unit 72 displays blood flow information indicated by the data received from the detection unit 71.

<Supplement about frequency Fx>
As exemplified in each of the above-described embodiments, the preferred embodiment of the present invention employs a configuration (hereinafter referred to as “configuration A”) that performs filtering so that components with higher frequencies in the processing band B are suppressed. The behavior that can be observed from an actual blood flow analysis device (hereinafter referred to as "a real product") by adopting the configuration A will be described below.

  First, N types of frequency spectra M (1) to M (N) are assumed. Each frequency spectrum M (1) to M (N) corresponds to the product of the frequency f and the intensity spectrum P (f). As shown in FIGS. 15-17, a first range O1 and a second range O2 are defined in the frequency domain. The second range O2 is positioned higher than the first range O1. The second range O2 is divided into N bands K (1) to K (N). The bandwidths of the respective bands K (1) to K (N) are the same. One arbitrary frequency spectrum M (n) is a component of the first range O1 and the n-th (n = 1) of N bands K (1) to K (N) in the second range O2. And N) components of the band K (n). The intensities of the components of the band K (n) are common over the N frequency spectra M (1) to M (N). In the frequency spectrum M (n), a band other than the band K (n) in the second range O2 is zero. The shape of the first range O1 of the frequency spectrum M (n) is arbitrary, but is common to the N frequency spectra M (1) to M (N). One arbitrary input signal Y (n) is a signal in the time domain in which the intensity distribution in the frequency domain is the frequency spectrum M (n). That is, the input signal Y (n) is generated by the inverse Fourier transform on the frequency spectrum M (n). A signal generator such as a pulse generator is used to generate the input signal Y (n).

  It is assumed that each of N types of input signals Y (1) to Y (N) is sequentially input to a wiring or a terminal to which the detection signal Sb is supplied in a real product. When the input signal Y (n) is supplied to the actual product, the blood flow index F (n) is displayed. As described above, the intensities of the components of the band K (n) are common to the N types of input signals Y (1) to Y (N). When the real product adopts the configuration A, the higher the band side component in the processing band B is suppressed, the more the band K (n) of the input signal Y (n) is located on the higher side The flow index F (n) is a small numerical value. Therefore, when “blood flow index F (1)> blood flow index F (2)>...> Blood flow index F (N)” (that is, the higher the frequency is suppressed, the configuration A is adopted) It can be determined that

Although the above description focuses on the blood flow index F, the blood flow index for determining whether the actual product adopts the configuration A is not limited to the above examples. For example, various blood flow indicators such as mean blood pressure, pulse pressure or blood volume indicator may be used. When a software filter is used as an actual product, a blood flow index calculated by receiving light such that the light receiving unit that generates the detection signal Sa in the actual product generates the input signal Y (n) F (n) may be used to determine whether or not configuration A is adopted.

<Modification>
Each form illustrated above can be variously deformed. The aspect of a specific deformation | transformation is illustrated below. It is also possible to appropriately merge two or more aspects arbitrarily selected from the following exemplifications.

(1) It is also possible to realize the blood flow analysis device 100 by a plurality of devices configured separately from one another. For example, it is also possible to realize the arithmetic processing unit 61 illustrated in each of the above-described embodiments by a general-purpose information terminal such as a mobile phone or a smartphone. Moreover, the structure which displays the blood-flow information which the arithmetic processing part 61 produced | generated on the display apparatus 24 which an information terminal comprises can also be employ | adopted.

(2) The order of the plurality of elements constituting the output circuit 34 is not limited to the above-described exemplary embodiments. For example, although the A / D conversion unit 53 A / D converts the detection signal Sc generated by the signal processing unit 52 in each of the embodiments described above, the signal processing unit 52 and the A / D are illustrated as illustrated in FIG. It is also possible to reverse the order with the conversion unit 53. In the configuration of FIG. 18, the A / D conversion unit 53 converts the detection signal Sb amplified by the signal amplification unit 51 from analog to digital, and the signal processing unit 52 performs detection processing on the detection signal Sc after conversion. Generate Therefore, a digital filter that suppresses the component in the processing band B of the detection signal Sc is used as the signal processing unit 52. Also, the signal processing unit 52 can be realized by the control device 20 executing a program. That is, the signal processing unit 52 may be a software filter.

(3) Although the blood flow velocity V is illustrated as blood flow information in each embodiment described above, the type of information on blood flow (blood flow information) is not limited to the above examples. For example, it is also possible to present the subject with the blood flow index F calculated by the above equation (1a) as blood flow information. Alternatively, a blood volume index (so-called MASS value) may be calculated from the detection signal Sd, and the blood volume index may be calculated as blood flow information. It is also possible to generate other biological information from blood flow information such as blood flow index F, blood volume index and blood flow velocity V. For example, various biological information such as blood pressure, average blood pressure, pulse pressure, oxygen saturation (SpO2), blood vessel diameter, or blood vessel age (blood vessel hardness), the blood flow such as blood flow index F and blood flow velocity V It can be deduced from the information.

(4) In the above-described embodiments, the filter processing (FIG. 5) in which the gain is continuously reduced so that the higher the frequency in the processing band B is suppressed, the signal processing unit 52 performs The frequency characteristics of the filtering process are not limited to the above examples. As shown in FIG. 19, a filtering process may be performed in which the gain is reduced stepwise toward the high frequency side in the processing band B. The filter processing in FIGS. 5 and 19 is filter processing in which the higher the frequency in the processing band B is, the more the filter processing is suppressed (ie, the higher the frequency, the monotonically decreasing gain). Further, as shown in FIG. 20, in the filter processing of FIG. 5, a range in which the gain is set to a specific value may be provided at predetermined intervals in the processing band B. Although FIG. 20 exemplifies the case where the range in which the gain is set to 0 is provided at predetermined intervals, the set gain may be 0 or more.

  Furthermore, multiple filtering processes may be combined. For example, the filter processing in which the gain is continuously decreased so that the higher the frequency in the processing band B is suppressed (FIG. 5), and the filter processing in which the gain is decreased stepwise toward the high frequency side (FIG. 19) A plurality of (two or three) filters may be executed among the filter processing (FIG. 20) in which the range in which the gain is set to 0 is provided at predetermined intervals. As understood from the above description, if filtering is performed so that the component of the frequency fH in the processing band B is suppressed compared to the component of the frequency fL lower than the frequency Fx at the lower end of the processing band B The frequency characteristics of the filtering process are arbitrary. However, according to the above-described embodiments in which the filter processing (FIG. 5) in which the gain changes continuously so that the higher the frequency in the processing zone B is suppressed, the shot that becomes particularly dominant on the high frequency side The effect of reducing the influence of noise can be realized more effectively.

(5) In each of the above-described embodiments, the blood flow analysis apparatus 100 configured as a single device is illustrated, but as in the following example, a plurality of elements of the blood flow analysis apparatus 100 are realized as separate devices from each other It can be done.

  In each of the above-described embodiments, the blood flow analysis apparatus 100 including the detection apparatus 30 is illustrated, but as illustrated in FIG. 21, a configuration in which the detection apparatus 30 is separated from the blood flow analysis apparatus 100 is also assumed. . The detection device 30 is, for example, a portable optical sensor module mounted on a measurement site M such as the subject's wrist or upper arm. The blood flow analysis device 100 is realized by an information terminal such as a mobile phone or a smartphone. The blood flow analysis device 100 may be realized by a watch-type information terminal. The detection signal Sd generated by the detection device 30 is transmitted to the blood flow analysis device 100 in a wired or wireless manner. The arithmetic processing unit 61 of the blood flow analysis device 100 calculates blood flow information from the detection signal Sd and displays it on the display device 24. As understood from the above description, the detection device 30 can be omitted from the blood flow analysis device 100.

  In each of the above-described embodiments, the blood flow analysis device 100 including the display device 24 is illustrated, but as illustrated in FIG. 22, a configuration in which the display device 24 is separated from the blood flow analysis device 100 is also assumed. . The arithmetic processing unit 61 of the blood flow analysis device 100 calculates blood flow information from the detection signal Sd, and transmits data for displaying the index to the display device 24. The display device 24 may be a dedicated display device, but may be mounted on, for example, an information terminal such as a mobile phone or a smart phone, or a watch-type information terminal portable by a subject. The blood flow information calculated by the arithmetic processing unit 61 of the blood flow analysis device 100 is transmitted to the display device 24 by wire or wirelessly. The display device 24 displays blood flow information received from the blood flow analysis device 100. As understood from the above description, the display device 24 can be omitted from the blood flow analysis device 100.

  As exemplified in FIG. 23, a configuration in which the detection device 30 and the display device 24 are separated from the blood flow analysis device 100 (biological analysis unit) is also assumed. For example, the blood flow analysis device 100 (biological analysis unit) is mounted on an information terminal such as a mobile phone or a smartphone.

  In addition, in a configuration in which the detection device 30 and the blood flow analysis device 100 are separated, it is possible to mount an element for calculating an intensity spectrum in the detection device 30. The intensity spectrum calculated by the detection device 30 is transmitted to the blood flow analysis device 100 by wire or wireless.

(6) In each of the above-described embodiments, the wristwatch-type blood flow analysis apparatus 100 including the housing 12 and the belt 14 is illustrated, but the specific form of the blood flow analysis apparatus 100 is arbitrary. For example, a patch type that can be applied to the subject's body, an earring type that can be attached to the subject's auricle, a finger-mounted type (for example, nailed type) that can be attached to the subject's fingertips, or can be attached to the subject's head Any form of blood flow analysis device 100 such as a head mounted type may be employed.

(7) In each of the above-described embodiments, the blood flow information of the subject is displayed on the display device 24. However, the configuration for notifying the subject of the blood flow information is not limited to the above examples. For example, blood flow information can be reported to the subject by voice. In the ear-worn blood flow analysis apparatus 100 that can be attached to the subject's ear, a configuration in which blood flow information is notified by voice is particularly preferable. Furthermore, it is not essential to notify blood flow information to the subject. For example, the blood flow information calculated by the blood flow analysis device 100 may be transmitted from the communication network to another communication device. Alternatively, blood flow information may be stored in a portable recording medium that can be attached to or detached from the storage device 22 of the blood flow analysis device 100 or the blood flow analysis device 100.

(8) In each of the above-described embodiments, the blood flow analysis device 100 that analyzes the blood flow of a subject is illustrated, but the scope to which the present invention is applied is not limited to the analysis of blood flow. For example, the present invention can be applied to an apparatus that analyzes the flow of various liquids other than blood (for example, a drug solution flowing in a tube). As understood from the above description, the preferred embodiment of the present invention is a device for analyzing a fluid (fluid analysis device), and the blood flow analysis device 100 described in each of the above embodiments is a preferred embodiment of the present invention It is an illustration of a fluid analysis device concerning the above.

(9) The blood flow analysis device 100 according to each of the above-described embodiments is realized by the cooperation of the control device 20 and the program, as described above. The program according to the preferred embodiment of the present invention may be provided in the form of being stored in a computer readable recording medium and installed on the computer. Moreover, it is also possible to provide a computer stored in a recording medium of the distribution server in the form of distribution via a communication network. The recording medium is, for example, a non-transitory recording medium, and is preferably an optical recording medium (optical disc) such as a CD-ROM, but any known medium such as a semiconductor recording medium or a magnetic recording medium may be used. Recording media of the form Note that non-transitory recording media include any recording media except transient propagation signals, and do not exclude volatile recording media.

DESCRIPTION OF SYMBOLS 100 ... Blood flow analysis apparatus, 12 ... Housing | casing part, 14 ... Belt, 20 ... Control apparatus, 22 ... Storage apparatus, 24 ... Display apparatus, 30 ... Detection apparatus, 31 ... Light emission part, 32 ... Light reception part, 321, 322 ... Light receiving element, 33 ... Drive circuit, 34 ... Output circuit, 51 ... Signal amplification unit, 52 ... Signal processing unit, 53 ... A / D conversion unit, 61 ... Arithmetic processing unit.

Claims (10)

In the detection signal representing the intensity of the laser beam that has passed through the blood vessel, filtering is performed so that the component of the frequency within the predetermined processing band is suppressed compared to the component of the frequency lower than the frequency of the lower end of the processing band. A signal processing unit to be executed,
And a calculation processing unit configured to generate information on blood flow in the blood vessel from the signal after the filtering process. The arithmetic processing unit generates information on the blood flow by integrating a product of the intensity of each frequency in the intensity spectrum of the filtered signal and the frequency for a predetermined arithmetic range.
The blood flow analysis device according to claim 1, wherein the processing band and the calculation range partially overlap each other. The blood flow analysis device according to claim 1 or 2, wherein the signal processing unit performs the filtering process on the detection signal so as to suppress a component having a higher frequency in the predetermined processing band. The calculation range is a range between a first frequency and a second frequency above the first frequency,
The blood flow analysis device according to claim 2 or 3, wherein the frequency at the lower end of the processing band is lower than the second frequency. The blood flow analysis device according to claim 4, wherein the frequency at the lower end of the processing band exceeds the frequency higher than the first frequency by 1/2 of the calculation range. The blood flow analysis device according to claim 5, wherein the frequency at the lower end of the processing band falls below the frequency higher than the first frequency by 3/4 of the calculation range. The blood flow analysis device according to claim 6, wherein the lower end frequency of the processing band is a frequency higher than the first frequency by 2/3 of the calculation range. The blood flow analysis device according to any one of claims 1 to 7, wherein the processing band is a range in which the suppression of the detection signal by the signal processing unit is 6 dB / Oct or more. In the detection signal representing the intensity of the laser beam that has passed through the blood vessel, filtering is performed so that the component of the frequency within the predetermined processing band is suppressed compared to the component of the frequency lower than the frequency of the lower end of the processing band. Run
A blood flow analysis method for generating information on blood flow in the blood vessel from the signal after the filtering process. In the detection signal representing the intensity of the laser beam that has passed through the blood vessel, filtering is performed so that the component of the frequency within the predetermined processing band is suppressed compared to the component of the frequency lower than the frequency of the lower end of the processing band. A signal processing unit to be executed, and
The program which functions a computer as an arithmetic processing part which produces | generates the information regarding the blood flow in the said blood vessel from the signal after the said filter process.

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