JP4470681B2 - Optical biological measurement device - Google Patents

Description

  The present invention relates to an optical biological measurement apparatus that measures biological information using near-infrared light. The present invention, for example, non-invasively measures the activity status of each part of the brain or muscle and measures the function of each part, such as a near-infrared imaging apparatus (such as a brain function measuring apparatus), Used as a biological oxygen monitor for monitoring oxygen consumption.

Near-infrared light is transmitted through skin tissue and bone tissue and is absorbed by oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) in blood. Near-infrared light has different spectral absorption spectrum characteristics for oxyhemoglobin and deoxyhemoglobin.
In recent years, this property of near-infrared light is called near infrared spectroscopy (hereinafter abbreviated as NIRS), which measures the activity state of a living body such as a brain, various organs, and muscles in a non-invasive manner. It is used as a measurement method and is practically used as a brain function measuring device or oxygen monitor.

  For example, in brain function measurement by NIRS, as shown in FIG. 8, a plurality of incident probes 51 that make incident light transmitted from a near-infrared light source via an optical fiber incident on the head and the inside of the head are scattered. Then, a plurality of detection probes 52 that receive light emitted from the head again are used, and these incident probes 51 and detection probes 52 are fixed to a probe holder 53 attached to the scalp. In this example, twelve incident probes 51 and twelve detection probes 52 are arranged on the probe holder 53 so as to be adjacent to each other.

Then, near infrared light is emitted from each incident probe 51 at an appropriate timing, and light scattered and reflected by the brain (brain cortex) is received by the adjacent detection probe 52. Although light can be received by a detection probe other than the adjacent detection probe, here, in order to simplify the explanation, only the case of detection by an adjacent detection unit is considered. Accordingly, the intermediate region between each incident probe 51 and each detection probe 52 becomes a measurement channel (region having measurement sensitivity), and the absorbance of a total of 36 (# 1 to # 36) measurement channels is measured. Based on the so-called modified Lambert Beer's law (MLB law), the oxyhemoglobin concentration at the measurement site (more precisely, the change in oxyhemoglobin concentration and the average optical path length product [oxyHb]) Although the average optical path length is omitted as being constant), deoxyhemoglobin concentration (exactly the concentration change of deoxyhemoglobin / average optical path length product [deoxyHb], the average optical path length is omitted as constant) ) Further, the total hemoglobin concentration ([oxyHb] + [deoxyHb]) calculated from these is calculated. These changes in hemoglobin concentration are acquired as biological signal data (brain activation data), image processing such as averaging processing is performed, a brain image is formed, and displayed on a display (not shown).

In brain function measurement by NIRS, during the measurement, the subject is given exercise load such as running on a treadmill or a mental load caused by a thinking task according to a predetermined time schedule. The influence on each part of the brain function by applying a load or a mental load is also measured.
FIG. 9 shows the time-dependent change data of oxyhemoglobin concentration, deoxyhemoglobin concentration, and total hemoglobin concentration calculated based on the measurement data when exercise load is applied by running the treadmill, and the 36 measurement channels shown in FIG. It is an example of a screen display when a list is displayed side by side for each (# 1 to # 36).

By the way, in an optical biological measurement apparatus such as a brain function measurement apparatus using NIRS, as described above, in order to make light incident on the living body or detect light from the living body, the light is irradiated toward the living body. An incident probe for detecting light from a living body and a detection probe for receiving light from the living body are closely attached to the surface of the living body (such as the scalp). When the position or contact state of the living body contact portion of these probes changes, the amount of light (that is, absorbance) of the detection light suddenly changes discontinuously, and artifacts that cannot be considered as signal changes due to changes in the living body itself (pseudo) Signal) is generated.
Then, by detecting the signal in which the artifact is superimposed on the absorbance signal with the detection probe, the oxyhemoglobin concentration, deoxyhemoglobin concentration, and total hemoglobin concentration calculated based on the absorbance signal (the sum of the oxyhemoglobin concentration and deoxyhemoglobin concentration) The influence of the artifact is also superimposed on the time-lapse data of the biological signal as described above.

In such cases, traditionally, the visual evaluation based on the experience of the measurer has regarded discontinuous signal changes that cannot be generated physiologically or signal changes that seem unnatural in experience as artifacts. .
However, it is difficult to accurately determine whether or not artifacts are included only by visual evaluation based on the experience of the measurer.

Therefore, as a method for determining the artifact, the rate of change of the biological signal per unit time is calculated and compared with a predetermined reference value. If the rate of change is larger than the reference value, the artifact due to body movement is included. It is determined that body movement is not occurring unless it is larger than the reference value, and the influence of the artifact is removed by shifting the biological signal level according to the situation (patent) Reference 1).
JP-A-5-154136

As described above, if a method of calculating the rate of change per unit time of a biological signal is used, it is possible to determine quantitatively whether the biological signal includes an artifact.
However, even if it is actually determined using this method, some of the signals are considered to be biological signals, but there are cases where it is difficult to determine data in which the signals do not return to their original values.

For example, when measurement is performed while applying an exercise load, if a positional shift occurs in the incident probe 51 or the detection probe 52 (see FIG. 8) due to body movement, the time when the positional shift occurs Since a staircase-like change occurs, it can be easily determined as an artifact by monitoring the rate of change of the detection signal per unit time.
However, when the sweat is gradually generated by the exercise load and the sweat enters the optical path of the incident probe 51 or the detection probe 52 and affects it, a sudden change does not occur. It becomes an artifact that cannot be done.
Artifacts that do not show such a sudden change can be caused not only by sweat but also by other causes (the cause may be unknown), in which case the unit time of the detection signal In the method of monitoring the rate of change per hit, it was difficult to determine an artifact.

Therefore, the present invention provides an optical biological measurement apparatus that can accurately determine whether a detected signal is a biological signal that does not include an artifact or a mixed signal that includes an artifact in the biological signal. The purpose is to do.
It is another object of the present invention to provide an optical biological measurement apparatus that can accurately determine at which point an artifact is included when the biological signal includes an artifact.

The optical biometric device of the present invention made to solve the above-mentioned problems is information on a living body based on detection light by irradiating light, scattering inside the living body, and detecting light re-emitted from inside the living body. And an optical probe for irradiating light into the living body and a detection probe for detecting light re-emitted from the living body, at least three different wavelengths λ _n (where n ≧ 3) Optical measurement unit that measures the change in absorbance and obtains the measured change in absorbance ΔAm (λ _n ), the amount of change in oxyhemoglobin concentration / average optical path length [oxyHb], and the amount of change in deoxyhemoglobin concentration / average optical path Using the relational expression (LB) between the long product [deoxyHb] and the absorbance change ΔA, based on the measured absorbance change ΔAm (λn), the oxyhemoglobin concentration change / average light is calculated by the least square method. Path length product [oxyHb], deoxyhemoglobin concentration change amount / average optical path length product [deoxyHb] concentration change amount / average optical path product calculation unit, calculated oxyhemoglobin concentration change amount / average optical path length product [oxyHb], Based on the deoxyhemoglobin concentration change / average optical path length product [deoxyHb], again using the relational expression (LB), a calculated absorbance change calculation unit that calculates a calculated absorbance change ΔAc (λn); Residual square sum / residual square sum ratio for calculating residual square sum D or residual square sum ratio E based on measured absorbance change amount ΔAm (λ _n ) and calculated absorbance change amount ΔAc (λ _n ) An arithmetic unit and a determination unit for determining whether or not an artifact is included by comparing the residual sum of squares D or the residual sum of squares ratio E with a reference value R are provided.

Here, the relational expression (LB) is defined by the following expression (1) on the assumption that the modified Lambert-Beer law holds.
ΔA (λ _n ) = E ₀ (λ _n ) × [oxyHb] + E _d (λ _n ) × [deoxyHb] (1)
Here, E ₀ (λ _n ) is the absorbance coefficient of oxyhemoglobin, and E _d (λ _n ) is the absorbance coefficient of deoxyhemoglobin.

  [OxyHb] is the oxyhemoglobin concentration change / average optical path length product, and [deoxyHb] is the deoxyhemoglobin concentration change / average optical path length product. Can be treated as constant. In that case, equation (1) can treat [oxyHb] as the oxyhemoglobin concentration change amount and [deoxyHb] as the deoxyhemoglobin concentration change amount. Shall be included.

The residual sum of squares D is defined by the following equation (2).
D = (ΔAm (λ ₁ ) −ΔAc (λ ₁ )) ² + (ΔAm (λ ₂ ) −ΔAc (λ ₂ )) ² +... + (ΔAm (λ _n ) −ΔAc (λ _n )) ² (2)
The residual square sum ratio E is defined by the following equation (3).
E = D / ((ΔAm (λ ₁ )) ² + (ΔAm (λ ₂ )) ² +... + (ΔAm (λ _n )) ² )
.... (3)

According to this invention, the optical measurement unit of the optical biological measurement apparatus irradiates the living body with the measurement light from the incident probe and scatters (transmits) the living body by the detection probe attached at a position away from the incident probe. The re-emitted light is detected and the amount of change in absorbance is measured. At this time, the absorbance change amount is measured at at least three different wavelengths λ _n (where n ≧ 3), and the measured absorbance change amount ΔAm (λ _n ) is acquired.

  The amount of change in absorbance from the start of measurement is the case where the modified Lambert Beer's law (MLB rule) is established when the change in absorption is small, and is described above between the absorbance change ΔA, the absorber concentration change, and the average optical path length. (1) Formula is materialized.

Therefore, for example, when the absorbance is measured at _three near infrared wavelengths (λ ₁ , λ ₂ , λ ₃ ), the measured absorbance change amounts ΔAm (λ ₁ ), ΔAm (λ ₂ ), ΔAm (λ ₃ ) Is given by the following equation (4).
ΔAm (λ ₁ ) = E ₀ (λ ₁ ) × [oxyHb] + E _d (λ ₁ ) × [deoxyHb]
ΔAm (λ ₂ ) = E ₀ (λ ₂ ) × [oxyHb] + E _d (λ ₂ ) × [deoxyHb]
ΔAm (λ ₃ ) = E ₀ (λ ₃ ) × [oxyHb] + E _d (λ ₃ ) × [deoxyHb]
... (4)

  The concentration change / average optical path product calculation unit calculates the difference between the oxyhemoglobin concentration change / average optical path length product [oxyHb] and deoxyhemoglobin concentration change / average optical path length product [deoxyHb] and the absorbance change ΔA. Based on the measured absorbance change ΔAm (λn) using the relational expression (LB), the oxyhemoglobin concentration change / average optical path length product [oxyHb], deoxyhemoglobin concentration change / average optical path length by the least square method Calculate the product [deoxyHb]. That is, as a result of measuring at three (or more) different wavelengths, the unknowns are the concentration variation / average optical path length product [oxyHb] of oxyhemoglobin and the concentration variation / average optical path length product [deoxyHb] of deoxyhemoglobin. Since there are three (or more) equations for two, there is no single solution that satisfies the equations at the same time, so the least square method is used to find the optimal solution. .

As a result, [oxyHb] and [deoxyHb] can be expressed by a solution of the following formula (5).

[oxyHb] = K ₁₁ ΔAm (λ ₁ ) + K ₁₂ ΔAm (λ ₂ ) + K ₁₃ ΔAm (λ ₃ )
[deoxyHb] = K ₂₁ ΔAm (λ ₁ ) + K ₂₂ ΔAm (λ ₂ ) + K ₂₃ ΔAm (λ ₃ )
... (5)

Here, the values of K _{11 to} K ₂₃ are E ₀ (λ ₁ ), E ₀ (λ ₂ ), E ₀ (λ ₃ ), E _d (λ ₁ ), E _d (λ ₂ ), E _d ( A value determined from the value of λ ₃ ), that is, a value determined by determining the measurement wavelengths (λ ₁ , λ ₂ , λ ₃ ).
For example, when λ ₁ = 780 nm, λ ₂ = 805 nm, and λ ₃ = 830 nm, E ₀ (λ ₁ ) to E _d (λ ₃ ) are obtained as follows by Matcher SJ et al.
E ₀ (780) = 0.7360, E ₀ (805) = 0.8973, E ₀ (830) = 1.0507
E _d (780) = 1.1050, E _d (805) = 0.8146, E _d (830) = 0.7804
(Matcher SJ, Elwell CE, et al. Performance comparison of several published tissue near-infrared spectroscopy algorithms. Analytical Biochemistry 227: 54-68 (1995))
By using this value and performing an operation by the method of least squares, the values of K _{11 to} K ₂₃ are obtained as follows.
K ₁₁ = −1.4888, K ₁₂ = 0.5970, K ₁₃ = 1.4847
K ₂₁ = 1.8545, K ₂₂ = −0.2394, K ₂₃ = −1.0947

Based on the above calculations, the calculated oxyhemoglobin concentration change / average optical path length product [oxyHb] and deoxyhemoglobin concentration change / average optical path length product [deoxyHb] are used as biological signals indicating the activity data of the living body (for example, the brain). Will do.

  Subsequently, the calculated absorbance change amount calculation unit, residual sum of squares / residual sum of squares ratio calculation unit, and determination unit determine whether or not the calculated [oxyHb] and [deoxyHb] include an artifact. Arithmetic processing is performed to perform quantitatively.

Based on the calculated change in oxyhemoglobin concentration / average optical path length product [oxyHb] and deoxyhemoglobin concentration change / average optical path length product [deoxyHb], the calculated absorbance change amount calculation unit again uses the modified Lambert-Beer law. The calculated absorbance change ΔAc (λn) is calculated by calculation using the relational expression (1).
For example, as described above, when the absorbance is measured at _three near infrared wavelengths (λ ₁ , λ ₂ , λ ₃ ), the calculated absorbance change amounts ΔAc (λ ₁ ), ΔAc (λ ₂ ), ΔAc (λ ₃ ) is given by the following equation (4).

ΔAc (λ ₁ ) = E ₀ (λ ₁ ) × [oxyHb] + E _d (λ ₁ ) × [deoxyHb]
ΔAc (λ ₂ ) = E ₀ (λ ₂ ) × [oxyHb] + E _d (λ ₂ ) × [deoxyHb]
ΔAc (λ ₃ ) = E ₀ (λ ₃ ) × [oxyHb] + E _d (λ ₃ ) × [deoxyHb]
... (6)

The residual sum of squares / residual sum of squares ratio calculation unit is a measured absorbance change amount ΔAm (λ _n ) obtained by measurement by the optical measurement unit and a calculated absorbance change amount ΔAc (λ _n ) calculated by the above equation (6). Based on the above, the residual sum of squares D expressed by the expression (2) or the residual sum of squares ratio E expressed by the expression (3) is calculated.
The residual sum of squares is calculated for the following reason. That is, when the density change amount / average optical path product calculation unit calculates the equation (5), the least square method is used as described above. This is the value of the residual sum of squares of the equation (2). This means that the values of [oxyHb] and [deoxyHb] are calculated so that is minimized. Therefore, if the residual sum of squares is used, the magnitude of the least square error of the calculated [oxyHb] [deoxyHb] value can be determined quantitatively.
Regardless of the cause, whether it is an artifact that causes a sudden change due to body movement or an artifact that does not cause any other sudden change, the magnitude of the effect of the artifact is the magnitude of the least square error. Appears as a change.

  Therefore, the determination unit compares the reference value R set in advance for determination with the residual sum of squares D (or residual sum of squares ratio E). Thereby, it is quantitatively determined whether or not an artifact is included in the signal.

  According to the present invention, it is possible to quantitatively and accurately determine whether a biological signal does not include an artifact or a biological signal that includes an artifact. In particular, it can be considered as a biological signal at first glance where no stepwise change is seen, but even in the case of a signal where the signal does not return to its original value after the change, it can be quantitatively determined.

(Other means and effects to solve the problem)
In the above invention, the optical measurement unit obtains the measured absorbance change amount ΔAm (λ _n ) from time to time, and the concentration change amount / average optical path product calculation unit, calculated absorbance change amount calculation unit, residual sum of squares / residual When the sum of squares calculation unit and determination unit perform calculation and determination over time based on the acquired measured absorbance change amount ΔAm (λ _n ), and when the determination unit determines that the artifact is included, the time when the artifact occurs May be provided with a storage unit for generating artifacts.
According to this, the optical measurement unit measures the absorbance signal that changes from time to time, and based on the measured absorbance signal, the concentration change amount / average optical path product calculation unit, the calculated absorbance change amount calculation unit, the residual The sum of squares / residual sum of squares ratio calculation unit and determination unit operate to determine whether or not artifacts are included over time. Then, when the determination unit determines that the artifact is included, the artifact generation time storage unit stores the artifact generation time point, so that the time point at which the artifact is included in the temporal change of the biological signal is determined. be able to.
Therefore, when the measurer examines the measurement results, only the data up to the time when the artifact occurs will be used, or the data after the time when the artifact will be used should be appropriately interpolated to use the biological signal. Will be able to.

The optical biological measurement apparatus further includes a display unit and a display control unit that controls display contents of the display unit, and the display control unit includes an oxyhemoglobin concentration change amount / average optical path length product [oxyHb ], Deoxyhemoglobin concentration change / average optical path length product [deoxyHb], and the total of these two, total hemoglobin concentration change / average optical path length product [totalHb], is displayed on the display unit as time-dependent data At the same time, when the determination unit determines that the artifact is included, the control is performed to display the area including the artifact in the displayed temporal data with reference to the artifact generation time stored in the artifact generation storage unit. May be.
According to this, at least one of oxyhemoglobin concentration change / average optical path length product [oxyHb], deoxyhemoglobin concentration change / average optical path length product [deoxyHb], total hemoglobin concentration change / average optical path length product [totalHb] If the measured time data is displayed on the display and it is determined that the artifact is included, the area including the artifact and the area not including the artifact are displayed in a distinguishable manner. The measurement results can be examined while considering the presence or absence of

In the above invention, the optical biological measurement apparatus further includes a display unit and a display control unit that controls display contents of the display unit, and the optical measurement unit includes a plurality of incident probes and a plurality of detection probes, For a plurality of measurement channels determined by the combination of the incident probe and the detection probe, the absorbance change amount of each measurement channel is measured to obtain a plurality of measurement absorbance change amounts ΔAm (λ _n ), and the obtained plurality of measurement absorbance changes are obtained. Whether the concentration change amount / average optical path product calculation unit, the calculated absorbance change amount calculation unit, the residual sum of squares / residual sum of squares ratio calculation unit, and the determination unit include an artifact with respect to the amount ΔAm (λ _n ) The display control unit displays the data of a plurality of measurement channels side by side on the display unit and determines the artifact based on the determination result of the determination unit. And a measurement channel that does not contain a measurement channel including bets may perform control to identifiably displayed.
According to this, since the data from a plurality of measurement channels are displayed side by side, and the identification symbol for identifying the measurement channel including the artifact and the measurement channel not including the artifact is displayed, the artifact is displayed when the artifact is included. By examining the positional relationship of the included measurement channels, it becomes easy to identify the cause of the artifact generation (for example, identification of whether the incident probe is the cause or the detection probe is the cause).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an optical biometric device according to an embodiment of the present invention. More specifically, FIG. 1 shows a configuration of a brain function measuring device that measures a brain activity state from oxyhemoglobin concentration or deoxyhemoglobin concentration. FIG. This optical biological measurement apparatus mainly includes an optical measurement unit 10, a control unit 20 that controls the entire optical biological measurement device, a storage unit 30 that stores application programs and measurement data, and a display unit 40 that displays setting screens and measurement results. It consists of.

The optical measurement unit 10 is connected to the light source 12, the plurality of light transmission fibers 13, the incident unit 15 formed by the plurality of incident probes 14 connected to the light transmission fiber, the plurality of detection probes 16, and the plurality of detection probes. A light receiving fiber 17 and a detector 19 formed by a detector 18.
As the light source 12, three laser light sources having different emission wavelengths are used. For example, light having three wavelengths of λ ₁ (780 nm), λ ₂ (805 nm), and λ ₃ (830 nm) is selectively selected by a switching mechanism (not shown). It is configured to emit light.
The incident probe 14 is fixed by the probe holder 53 so that the tip is in close contact with the scalp so that the light transmitted through the light transmission fiber 13 is incident on the head.
The same applies to the detection probe 16, and the probe tip 53 is fixed to the scalp by the probe holder 53. The light detected by the detection probe 16 is sent to the detector 18. For the detector 18, a light receiving element such as a photomultiplier or a photodiode is used.

The incident probe 14 and the detection probe 16 are arranged so as to be adjacent to each other, and an intermediate region sandwiched between the adjacent incident probe 14 and the detection probe 16 becomes a measurement channel (a region having sensitivity). It is like that.
Then, a combination of a pair of incident probe 14 and detection probe 16 is selected by control by an optical measurement unit control unit 21 described later, and one of measurement channels (# 1 to # 36 in FIG. 8) determined by the combination is selected. Measurement is performed. At this time, a plurality of measurement channels may be measured simultaneously by selecting a combination that does not cause light interference with each other.
A signal (absorbance signal) received by the detector 18 is sent to the control unit 20 via the amplifier 36 and the A / D converter 37.

The control unit 20 includes a CPU and executes various functions by executing programs stored in the storage unit 30.
When the control unit 20 is divided based on the function to be executed, the optical measurement unit control unit 21, the concentration change / average optical path product calculation unit 22, the calculated absorbance change calculation unit 23, the residual square sum / residual square sum. They can be classified into a rate calculation unit 25, a determination unit 25, and a display control unit 26.

  The optical measurement unit control unit 21 sequentially receives a pair of incident probes 14a from the plurality of incident probes 14 and the plurality of detection probes 16 of the optical measurement unit 10 at appropriate timing in order to obtain mapping data of brain activity signals. By selecting the combination of the detection probes 16a, transmitting light from the incident probe 14a at an appropriate timing, and receiving light by the detection probe 16a, the absorbance signal for the corresponding measurement channel (# 1 to # 36) is collected. Control.

  The concentration change / average optical path product calculation unit 22 calculates the difference between the oxyhemoglobin concentration change / average optical path length product [oxyHb] and deoxyhemoglobin concentration change / average optical path length product [deoxyHb] and the absorbance change ΔA. Based on the measured absorbance change ΔAm (λ = 780, 805, 830 nm) using the relational expression (1), the oxyhemoglobin concentration change amount / average optical path length product [oxyHb], Calculation to calculate deoxyhemoglobin concentration change / average optical path length product [deoxyHb] (equation (5)) and total oxyhemoglobin concentration change / average optical path length product [totalHb] (= [oxyHb] + [deoxyHb]) I do.

  When the change in the amount of light absorption is small, the average optical path length can be treated as constant for simplification. In this case, in the equation (1), the average optical path length can be omitted, and [oxyHb] can be treated as an oxyhemoglobin concentration change amount and [deoxyHb] as a deoxyhemoglobin concentration change amount. In normal measurements, this condition is met. Also in this embodiment, the average optical path length is assumed to be constant, and this will be omitted in the following description.

  The calculated absorbance change calculator 23 calculates the calculated absorbance change ΔAc (λn) using the formula (1) based on the calculated oxyhemoglobin concentration change [oxyHb] and deoxyhemoglobin concentration change [deoxyHb]. ) Is calculated (formula (6)).

Residual square sum / residual square sum arithmetic operation part 24 includes a measurement amount of change in absorbance ΔAm obtained by measurement by the optical measuring unit _{11 (λ n), (6} ) formula in the calculated calculated absorbance variation ΔAc (λ _n ) To calculate a residual sum of squares D (formula (2)), and further calculate a normalized residual sum of squares ratio E (formula (3)).

  The determination unit 25 compares the reference value R obtained experimentally in advance with the residual sum of squares D (or residual square sum ratio E) to determine whether or not an artifact is included. Do. The reference value R is preferably obtained statistically from the measurement data of the signal including the artifact and the signal not including the artifact, but an appropriate value can be arbitrarily set based on the experience of the measurer.

The display control unit 26 controls the screen displayed on the display unit 40. As one form of display, the calculated oxyhemoglobin concentration change amount [oxyHb] and deoxyhemoglobin concentration change amount [deoxyHb] are displayed as time-dependent data of a biological signal (brain activity signal). In this display, when the data at the time of artifact occurrence is stored in the artifact occurrence time storage unit 27 to be described later, the time-lapse data of the measured biological signal is displayed, and a mark is displayed at the time of occurrence of the artifact, Change the color of the time-lapse data after the point of occurrence.
Further, the time-lapse data for a plurality of measurement channels are displayed side by side (see FIG. 9). In this case, for the measurement channel in which the data at the time of occurrence of the artifact is stored, the background color of the corresponding time-lapse data may be different from the background color of other channels, or the corresponding time-lapse data may be surrounded by a thick frame. And make it stand out.

  The storage unit 30 is configured by a storage device such as an HDD, and stores application programs necessary for control. The measured data is stored as needed and saved for later use. Further, an artifact occurrence storage unit 27 is formed, and when the determination unit 25 determines that an artifact is included, the generation point is stored.

  The display unit 40 is configured by a flat panel, a liquid crystal panel, and the like, and can display time-lapse data and a setting screen under the control of the display control unit 26.

Next, the operation of the above apparatus will be described with reference to the flowchart of FIG.
First, for each measurement channel (# 1 to # 36), an absorbance change amount (ΔAm) is collected by measurement at three different wavelengths (s101).
Subsequently, using the measured absorbance change amount (ΔAm), the average optical path length is constant, and the calculation according to the equation (5) is performed by the least square method, and the oxyhemoglobin concentration change amount [oxyHb], deoxyhemoglobin concentration change amount [deoxyHb ] And the total hemoglobin concentration change amount [totalHb] is calculated (s102).

Subsequently, a calculation according to the equation (6) is performed to calculate a calculated absorbance change amount (ΔAc) (s103).
Further, based on the measured absorbance change (ΔAm) and the calculated absorbance change (ΔAc), the residual sum of squares D (formula (2)) and the residual sum of squares ratio E (formula (3)) are calculated (s104). .

Then, the residual sum of squares D and the residual sum of squares ratio E are compared with a reference value R (threshold value) (S105). If the result of the comparison is smaller than the set reference value R, an artifact is included. The normal display is performed without taking any countermeasures (S106).
As a result of comparison, when the value is larger than the reference value R, it is determined that the artifact is included, and the background color indicating that the artifact is generated is displayed in a background color. In the time-lapse data, the color of the area where the artifact is generated is changed, or a mark is given to display it conspicuously (S107).

Next, an example of artifact determination in biological signal data (brain activation data) will be described. When collecting biosignal data, exercise was added by treadmill walking. The exercise load is a walking task with a speed of 3 km / h, and follows a time course of a 30-second rest, a 90-second task, and a 30-second rest (total 150 seconds).
The measurement channels were set to have the same arrangement as that shown in FIG. 8, and signals were collected from a total of 36 channels. After the measurement, the biological signal data from the 36 measurement channels were displayed side by side (see FIG. 9).
In the following, typical signal data from signals collected in these channels will be described.

  FIG. 3A is a typical brain activation data signal ([oxyHb] and [deoxyHb]) that does not include artifacts, and FIG. 3B shows a residual sum of squares ratio E ((3 ) Refer to equation). FIG. 4A shows a typical brain activation data signal when an artifact is included, and FIG. 4B shows a residual sum of squares ratio E corresponding thereto. Further, FIG. 5 (a) is considered to be a brain activation data signal, but the signal does not return to the original value after the task is finished, and it is difficult to determine whether or not an artifact is included in visual evaluation. FIG. 5B shows the residual sum of squares ratio E corresponding to the brain activation data signal.

In the case of the typical brain activation data of FIG. 3A, the residual sum of squares ratio E is approximately 10 ⁻⁶ or less (see FIG. 3B), whereas FIG. In the case of activation data including this artifact, the residual sum of squares ratio E increases corresponding to the change in the brain activation signal value and is 10 ⁻⁴ or more (see FIG. 4B). Further, in the case of the intermediate brain activation data in FIG. 5A, the residual sum of squares E rapidly increases after 100 seconds (thus, no artifact is included at 90 seconds). After the square sum E increases, it is 10 ⁻³ or more.
For example, the specific values in FIGS. 4A and 5A at the time of 90 seconds were 0.0005 and 0.00006.
Therefore, when it is determined whether or not artifacts are included based on the residual square sum ratio E, the reference value R is selected from the above data to a value larger than 0.00006 and smaller than 0.0005. For example, 0.0001 By setting the degree, it is possible to determine that the artifact is not included when R is smaller than this.

In this way, after setting R, the presence or absence of an artifact is determined using the set R as a reference value. When the residual sum of squares ratio E exceeds the reference value R, the presence or absence of an artifact can be clearly seen by changing the color of the corresponding area of the brain activation data.
When brain activation data from 36 measurement channels are displayed side by side on the display screen (see FIG. 9), channels exceeding the reference value R are displayed with the background color of the brain activation data changed. . According to the display example of FIG. 9, for example, four measurement channels # 2, # 3, # 8, and # 9 are displayed with different background colors. As a result, it is possible to easily determine that the specific incident probe 14 used in common in the measurement of these four channels is displaced.

The modified Lambert Beer's law (MLB law) (Equation (6)) is plotted using the value at the time of 90 seconds in FIG. 4 (a) and FIG. 5 (a). FIG. As shown in FIG.
The three straight lines shown in FIGS. 6 and 7 correspond to the three equations (6), respectively, and the intersection of the two straight lines uses two of the three equations (6). It shows the solution when solved. Since the two equations at this time can take three combinations, there are three intersections, that is, three solutions.
When the variation of the intersection is small, the brain activation signal is consistent with the MLB rule, that is, has no influence of the artifact. On the other hand, when the variation is large, the signal includes not only the brain activation signal but also the artifact. When the variation is large, the residual sum of squares ratio E becomes large.

  When FIG. 6 is compared with FIG. 7, the variation in the intersection is clearly smaller in the case of FIG. 7, and the brain activation signal conforms to the MLB law (no influence of the artifact). It can be seen that the data after 90 seconds in FIG. 5A does not include artifacts. On the other hand, in the case of FIG. 6, the MLB rule is significantly different from the MLB rule, and the signal includes not only the brain activation signal but also the artifact.

  INDUSTRIAL APPLICABILITY The present invention can be used when manufacturing an optical biological measurement apparatus that can accurately determine whether or not an artifact is included in a biological signal.

The block diagram which shows the structure of the optical biological measuring device which is one Embodiment of this invention. The flowchart explaining operation | movement by the optical biological measurement apparatus which is one Embodiment of this invention. The figure which shows the brain activation data which does not contain an artifact. The figure which shows the brain activation data containing an artifact. The figure which shows brain activation data in which it is unknown whether an artifact is included. The figure which shows data when the data of FIG. 4 are plotted by the MLB rule. The figure which shows data when the data of FIG. 5 are plotted by the MLB rule. The figure which shows the arrangement | positioning and measurement channel of the incident probe and detection probe of an optical biological measuring device. The figure which shows a screen when displaying the data for every measurement channel as a list.

Explanation of symbols

10: Optical measurement unit 12: Light source 14: Incident probe 15: Incident unit 16: Detection probe 18: Detector 19: Detection unit 20: Control unit 21: Optical measurement control unit 22: Density change amount / average optical path length product calculation unit 23: Calculated absorbance change amount calculation unit 24: Residual sum of squares / residual sum of squares ratio calculation unit 25: Determination unit 26: Display control unit 27: Artifact occurrence storage unit 30: Storage unit 40: Display unit

Claims (4)

An optical biometric device that obtains information about a living body based on detection light by irradiating light to scatter inside the living body and detecting light re-emitted from within the living body,
The absorbance measured by measuring the amount of change in absorbance at at least three different wavelengths λn (where n ≧ 3) with an incident probe that irradiates light into the living body and a detection probe that detects light re-emitted from the living body. An optical measurement unit for obtaining a change amount ΔAm (λn);
Using the relational expression (LB) between the concentration change amount / average optical path length product [oxyHb] and deoxyhemoglobin concentration change amount / average optical path length product [deoxyHb] of oxyhemoglobin and the absorbance change amount ΔA, Based on the measured absorbance change ΔAm (λn), the oxyhemoglobin concentration change amount / average optical path length product [oxyHb], deoxyhemoglobin concentration change amount / average optical path length product [deoxyHb] are calculated by the least square method. An average optical path product calculation unit;
Based on the calculated oxyhemoglobin concentration change / average optical path length product [oxyHb] and deoxyhemoglobin concentration change / average optical path length product [deoxyHb], using the relational expression (LB) again, the calculated absorbance change is calculated. A calculated absorbance change amount calculation unit for calculating an amount ΔAc (λ _n );
Residual sum of squares / residual sum of squares ratio calculation to calculate residual square sum D or residual sum of squares ratio E based on measured absorbance change amount ΔAm (λn) and calculated absorbance change amount ΔAc (λ _n ) And
An optical biological measurement apparatus comprising: a determination unit that determines whether or not an artifact is included by comparing a residual square sum D or a residual square sum ratio E with a reference value R .
here,
Relational expression (LB);
ΔA (λ _n ) = E ₀ (λ _n ) × [oxyHb] + E _d (λ _n ) × [deoxyHb]
Where E ₀ (λ _n ) is the absorbance coefficient of oxyhemoglobin, E _d (λ _n ) is the absorbance coefficient residual sum of squares D of deoxyhemoglobin;
D = (ΔAm (λ ₁ ) −ΔAc (λ ₁ )) ² + (ΔAm (λ ₂ ) −ΔAc (λ ₂ )) ² +... + (ΔAm (λ _n ) −ΔAc (λ _n )) ²
Residual square sum ratio E;
E = D / ((ΔAm (λ ₁ )) ² + (ΔAm (λ ₂ )) ² +... + (ΔAm (λ _n )) ² ) The optical measurement unit obtains the measured absorbance change ΔAm (λ _n ) from time to time, and also calculates the concentration change / average optical path product calculation unit, calculated absorbance change calculation unit, residual sum of squares / residual sum of squares ratio. Part, the determination part performs calculation and determination over time based on the obtained measured absorbance change amount ΔAm (λ _n ),
The optical biological measurement apparatus according to claim 1, further comprising an artifact generation time storage unit that stores an artifact generation time when determination including an artifact is made by the determination unit. The optical biological measurement device further includes a display unit and a display control unit that controls display contents of the display unit,
The display control unit calculates oxyhemoglobin concentration change / average optical path length product [oxyHb], deoxyhemoglobin concentration change / average optical path length product [deoxyHb], and the total hemoglobin concentration change that is the sum of these two,・ At least one of the average optical path length product [totalHb] is displayed as time-dependent data on the display unit, and when the determination unit determines that the artifact is included, the artifact generation time point stored in the storage unit when the artifact is generated The optical living body measurement apparatus according to claim 2, wherein control is performed so that a region including an artifact in the temporal data is displayed so as to be identified. The optical biological measurement device further includes a display unit and a display control unit that controls display contents of the display unit,
The optical measurement unit has a plurality of incident probes and a plurality of detection probes. For a plurality of measurement channels determined by the combination of the incident probe and the detection probe, a plurality of measurements are performed by measuring the amount of change in absorbance of each measurement channel. Obtain the change in absorbance ΔAm (λ _n )
For a plurality of measured absorbance change amounts ΔAm (λ _n ) acquired, a concentration change / average optical path product calculation unit, a calculated absorbance change calculation unit, a residual square sum / residual square sum rate calculation unit, and a determination unit , Perform calculations to determine whether or not to include artifacts,
The display control unit displays the data of the plurality of measurement channels side by side on the display unit, and performs control to display the measurement channel including the artifact and the measurement channel not including the identification channel based on the determination result of the determination unit. The optical biological measurement apparatus according to claim 1, wherein