Patent Description:
Newborns, babies and infants have immaturely developed bodies, and their vital signs are necessarily checked. In particular, newborns and babies have immature livers. Accordingly, the functions of the livers are required to be periodically monitored. One of important parameters indicating hepatic functions is bilirubin, which is generated during degradation of hemoglobin. Since the newborns and babies have immature livers, they cannot quickly degrade generated bilirubin. As a result, undegraded bilirubin is accumulated in skin tissue to cause jaundice. If appropriate treatment is not applied when jaundice is caused, bilirubin can be deposited in the brain and possibly cause a brain damage. The bilirubin allowance level depends on the ages (ages in month) of newborns and babies. Accordingly, in order to find the symptoms of jaundice as early as possible, it is important to measure the bilirubin concentrations (bilirubin values) of newborns and infants continuously.

The bilirubin concentration is measured using a method of sampling and directly measuring blood (blood sampling method), or an optical method. The blood sampling method has an advantage that can highly accurately measure bilirubin values. However, the method is invasive, and requires time and effort for measurement accordingly. On the other hand, the optical method is non-invasive. Consequently, the method can more easily achieve measurement than the invasive blood sampling method. For such a reason, the optical method is widely used to measure the bilirubin concentration (Patent Literatures <NUM> and <NUM>). Another bilirubin concentration measurement system is disclosed in document <CIT> (Patent Literatures <NUM>). This system includes a sensor device attachable to a subject, said sensor device comprising a unique light emitting element. However, such sensor device fails to provide accurate measures. A further bilirubin concentration measurement system is disclosed in document <CIT>. This document discloses a non-invasive monitor for the measurement of the level of bilirubin in the bloodstream of an infant, and, more particularly, to the use of certain light sources of predetermined wavelengths to be directed on to the infant's skin to penetrate to the infant's arterial bloodstream. The reflectivity or backscatter of the light from the infant's bloodstream from the light sources is detected and measured to determine the bilirubin level of that arterial system of the infant.

As described above, the optical method is non-invasive. Consequently, this method can more easily measure the bilirubin concentration than the invasive blood sampling method. However, conventional bilirubin concentration measurement apparatuses that use the optical method are large in size. Accordingly, they impose heavy burden on medical staff and subjects (newborns and babies). Consequently, it is difficult to measure the bilirubin concentration continuously.

Furthermore, use of the conventional bilirubin concentration measurement apparatus requires medical staff to conduct measurement for a subject, with the bilirubin concentration measurement apparatus being in contact with the subject, at every time of measurement. Accordingly, it is difficult to monitor the bilirubin concentration continuously. In particular, the bilirubin concentrations of newborns and babies sometimes change rapidly. In the case of using the conventional bilirubin concentration measurement apparatus, it is difficult to detect such rapid change in bilirubin concentration.

In view of the above problems, the present invention has an object to provide a bilirubin concentration measurement system that is small in size and capable of continuously monitoring the bilirubin concentration.

A bilirubin concentration measurement system according to an aspect of the present invention includes: a sensor device attachable to a subject; and a terminal device capable of wirelessly communicating with the sensor device. The sensor device includes: a first light emitting element that emits light in a first wavelength band at a first timing; a second light emitting element that emits light in a second wavelength band at a second timing; a light detection element that detects first reflected light that is the light in the first wavelength band having been incident on skin of the subject and been reflected at the first timing, and detects second reflected light that is the light in the second wavelength band having been incident on the skin of the subject and been reflected at the second timing; and a first communication unit that wirelessly transmits information about intensities of the first and second reflected light detected by the light detection element. The terminal device includes: a second communication unit that receives the information about the intensities of the first and second reflected light transmitted from the first communication unit; and a computing unit that calculates a bilirubin concentration using the information about the intensities of the first and second reflected light. The bilirubin concentration measurement system is characterized in that:.

The present invention can provide the bilirubin concentration measurement system that is small in size and capable of continuously monitoring the bilirubin concentration.

Hereinafter, referring to the drawings, embodiments of the present invention are described.

<FIG> is a block diagram for illustrating a bilirubin concentration measurement system according to an embodiment. As shown in <FIG>, the bilirubin concentration measurement system <NUM> according to this embodiment includes a sensor device <NUM>, and a terminal device <NUM>. The sensor device <NUM> is configured to be attachable to a subject (a newborn or a baby). The terminal device <NUM> is configured to be capable of wirelessly communicating with the sensor device <NUM>.

The sensor device <NUM> includes a control circuit <NUM>, light emitting elements <NUM> and <NUM>, and a light detection element <NUM>, an amplifier <NUM>, and a communication unit <NUM>. The terminal device <NUM> includes a communication unit <NUM>, a computing unit <NUM>, and a display unit <NUM>.

The control circuit <NUM> included in the sensor device <NUM> controls each of circuit elements included in the sensor device <NUM>. The control circuit <NUM> can be configured using an MCU (Micro Controller Unit), for example.

The light emitting element <NUM> emits light in a blue wavelength band (e.g., <NUM>) (hereinafter, also described as blue light) at a predetermined timing. The light emitting element <NUM> can be configured using a blue light emitting diode (LED), for example. The light emitting element <NUM> is configured to emit light according to a control signal (drive signal) supplied from the control circuit <NUM>. In other words, the light emitting timing of the light emitting element <NUM> is controlled using the control circuit <NUM>.

The light emitting element <NUM> emits light in a green wavelength band (e.g., <NUM>) (hereinafter, also described as green light) at a predetermined timing. The light emitting element <NUM> can be configured using a green light emitting diode (LED), for example. The light emitting element <NUM> is configured to emit light according to a control signal (drive signal) supplied from the control circuit <NUM>. In other words, the light emitting timing of the light emitting element <NUM> is controlled using the control circuit <NUM>.

The light detection element <NUM> detects reflected light that is blue light of the light emitting element <NUM> having entered skin of a subject and been reflected. Likewise, the light detection element <NUM> detects reflected light that is green light of the light emitting element <NUM> having entered the skin of the subject and been reflected. The light detection element <NUM> can be configured using an element capable of outputting an electric signal (voltage signal) according to the intensity of the reflected light. The light detection element <NUM> can be configured using a photodiode, for example.

The amplifier <NUM> amplifies the electric signal supplied from the light detection element <NUM>, and supplies the amplified signal to the control circuit <NUM>. Note that in a case where the control circuit <NUM> can directly deal with the electric signal (voltage signal) generated by the light detection element <NUM>, the amplifier <NUM> may be omitted.

The control circuit <NUM> supplies the communication unit <NUM> with the electric signal supplied from the amplifier <NUM>. Here, the electric signal supplied from the amplifier <NUM> corresponds to information about the intensities of the reflected light detected by the light detection element <NUM>. For example, the control circuit <NUM> may convert the electric signal supplied from the amplifier <NUM>, which is an analog signal, into a digital signal, and supply the converted digital signal to the communication unit <NUM>.

The communication unit <NUM> wirelessly transmits the electric signal supplied from the control circuit <NUM> (i.e., the information about the intensities of the reflected light), to the terminal device <NUM>. In other words, the communication unit <NUM> wirelessly transmits, to the terminal device <NUM>, the information about the intensities of the reflected light detected by the light detection element <NUM>.

The communication unit <NUM> of the terminal device <NUM> receives the information about the intensities of the reflected light, the information having been transmitted from the communication unit <NUM> of the sensor device <NUM>. The information about the intensities of the reflected light received by the communication unit <NUM> is supplied to the computing unit <NUM>.

For example, the communication unit <NUM> of the sensor device <NUM> and the communication unit <NUM> of the terminal device <NUM> can wirelessly communicate with each other using a wireless LAN, Bluetooth (R), or a mobile phone network, such as of <NUM>, <NUM> or <NUM>. The network to be used can be appropriately selected in conformity with the distance and the like between the communication unit <NUM> and the communication unit <NUM>.

The computing unit <NUM> calculates the bilirubin concentration using the information about the intensities of the reflected light received by the communication unit <NUM>. In other words, the computing unit <NUM> calculates the bilirubin concentration, using the intensity of the reflected light that is the blue light of the light emitting element <NUM> having entered the skin of the subject and been reflected, and the intensity of the reflected light that is the green light of the light emitting element <NUM> having entered the skin of the subject and been reflected. Note that a specific method of calculating the bilirubin concentration is described later. The computing unit <NUM> can be configured using an MCU (Micro Controller Unit), for example.

The display unit <NUM> displays the bilirubin concentration calculated by the computing unit <NUM>. The display unit <NUM> can be configured using a liquid crystal display, for example. For example, when the calculated bilirubin concentration exceeds a predetermined reference value, a warning message may be displayed on the display unit <NUM>.

The terminal device <NUM> can be configured using a smartphone, a tablet terminal or the like, for example. For example, when the calculated bilirubin concentration exceeds the predetermined reference value, a warning sound may be issued from a speaker included in the terminal device <NUM>.

The settings (e.g., settings of the light emitting timings and light intensities of the light emitting elements <NUM> and <NUM>, etc.) of the sensor device <NUM> may be configured using the terminal device <NUM>. In this case, setting information on the sensor device <NUM> is generated by the computing unit <NUM> of the terminal device <NUM>. The generated setting information is transmitted from the communication unit <NUM> of the terminal device <NUM> to the communication unit <NUM> of the sensor device <NUM>. The communication unit <NUM> of the sensor device <NUM> supplies the control circuit <NUM> with the setting information received from the terminal device <NUM>. Accordingly, the control circuit <NUM> can change the settings (e.g., settings of the light emitting timings and light intensities of the light emitting elements <NUM> and <NUM>, etc.) of the sensor device <NUM>.

<FIG> is a diagram for illustrating an arrangement example of the light emitting elements <NUM> and <NUM> and light detection elements <NUM> included in a sensor device <NUM> according to the embodiment. In the arrangement example shown in <FIG>, the two light emitting elements <NUM> and <NUM> and the four light detection elements 14_1 to 14_4 are implemented on an identical substrate <NUM>. The four light detection elements 14_1 to 14_4 are arranged around the two light emitting elements <NUM> and <NUM>. The light emitting surfaces of the two light emitting elements <NUM> and <NUM> and the light receiving surfaces of the four light detection elements 14_1 to 14_4 are configured to be on the same plane.

In the configuration example shown in <FIG>, the light detection elements 14_1 to 14_4 are arranged so as to encircle the light emitting elements <NUM> and <NUM>. Accordingly, it is possible to effectively detect reflected light which is light that is originated from the light emitting elements <NUM> and <NUM>, then incident on skin of the subject and reflected. Consequently, the sensor device <NUM> can be reduced in size. Note that the arrangement example shown in <FIG> is only an example. For the bilirubin concentration measurement system according to this embodiment, the arrangements and the numbers of light emitting elements <NUM> and <NUM> and light detection elements <NUM> can be freely determined.

<FIG> is a sectional view for illustrating a configuration example of the sensor device according to this embodiment. As shown in <FIG>, the sensor device <NUM> includes the substrate <NUM>, an exterior resin <NUM>, a substrate <NUM>, and a battery <NUM>. The sensor device <NUM> is attached to the surface of skin of a subject <NUM>.

The substrate <NUM> is a substrate on which the light emitting elements <NUM> and <NUM> and the light detection elements <NUM> are implemented. The substrate <NUM> is a substrate on which circuit elements, such as the control circuit <NUM>, the amplifier <NUM> and the communication unit <NUM> (see <FIG>), are implemented. The substrate <NUM> and the substrate <NUM> are stacked in the vertical direction. The battery <NUM> is a battery for driving the sensor device <NUM>, and can be configured using a lithium-ion secondary battery or the like.

As shown in <FIG>, the substrate <NUM>, the substrate <NUM> and the battery <NUM> are implemented in the exterior resin <NUM>. Specifically, the exterior resin <NUM> allows the substrate <NUM>, the substrate <NUM> and the battery <NUM> to be implemented, so as to enclose these elements. The light emitting surfaces of the light emitting elements <NUM> and <NUM>, and the light receiving surfaces of the light detection elements <NUM> are exposed from a surface of the exterior resin <NUM> facing the subject <NUM>. Consequently, when the sensor device <NUM> is attached to the surface of the skin of the subject <NUM>, this device is attached such that the light emitting surfaces of the light emitting elements <NUM> and <NUM> and the light receiving surfaces of the light detection elements <NUM> can be in contact with the subject <NUM>.

Preferably, the surface of the exterior resin <NUM> facing the subject <NUM> has a shape corresponding to the position of the subject <NUM> to which the sensor device <NUM> is attached. For example, in order to attach the sensor device <NUM>, which is a wearable device, onto a forehead of a newborn, the sensor device <NUM> is configured to have an attachment surface having a shape corresponding to the forehead of the newborn (a shape having a predetermined curve). For example, the substrates <NUM> and <NUM> may be flexible polyimide substrates. Such a configuration can bring the sensor device <NUM> into close contact with the skin surface of the subject <NUM>. For example, the exterior resin <NUM> can be configured using silicone rubber, PDMS (polydimethylsiloxane), epoxy resin, polyurethane or the like.

As shown in <FIG>, when the light emitting element <NUM> emits light in a state where the sensor device <NUM> is attached on the surface of the skin of the subject <NUM>, blue light from the light emitting element <NUM> is incident on the skin of the subject <NUM>. A part of the blue light incident on the skin reaches a blood vessel <NUM> of the subject <NUM> and is reflected, and is detected as reflected light by the light detection elements <NUM>. Likewise, when the light emitting element <NUM> emits light in the state where the sensor device <NUM> is attached on the surface of the skin of the subject <NUM>, green light from the light emitting element <NUM> is incident on the skin of the subject <NUM>. A part of the green light incident on the skin reaches the blood vessel <NUM> of the subject <NUM> and is reflected, and is detected as reflected light by the light detection elements <NUM>. Note that "reflected light" includes light from the light emitting elements <NUM> and <NUM> having been absorbed by or passed through the skin surface.

Next, a method of measuring the bilirubin concentration using the bilirubin concentration measurement system according to this embodiment is described. First a bilirubin concentration measurement principle is described. The bilirubin concentration measurement system according to this embodiment measures the bilirubin concentration in the blood of a subject using an optical method. Specifically, the bilirubin concentration is measured using the difference between the absorbance (absorptance) of bilirubin in the blue wavelength band, and the absorbance (absorptance) of bilirubin in the green wavelength band.

<FIG> is a diagram for illustrating the bilirubin concentration measurement principle. In a measurement apparatus shown in <FIG>, a blue light emitting element <NUM> and a green light emitting element <NUM> are arranged above a container that contains a bilirubin solution <NUM>. Furthermore, a light detection element <NUM> is arranged below the container, which contains the bilirubin solution <NUM>. The intensity of light detected by the light detection element <NUM> is converted into predetermined data by a detector <NUM>. Through use of the apparatus shown in <FIG>, the absorbance (absorptance) of blue light having passed through the bilirubin solution <NUM>, and the absorbance (absorptance) of green light having passed through the bilirubin solution <NUM> can be measured.

<FIG> is a graph showing the relationship between the bilirubin concentration and light intensity (in the case of blue light). <FIG> is a graph showing the relationship between the bilirubin concentration and light intensity (in the case of green light). In the graphs shown in <FIG>, the light intensity is normalized to be one when the bilirubin concentration is zero. As shown in <FIG>, for both the cases of blue light and green light, the intensity of light detected by the light detection element <NUM> decreases with increase in bilirubin concentration. In particular, in the case of blue light, the attenuation of light intensity is higher than that in the case of green light. Consequently, the blue light and the green light have different absorptances in the bilirubin solution. In particular, with respect to the blue light, the absorptance of light in the bilirubin solution is large. Note that as shown in <FIG>, the measured values approximately coincide with respective theoretical values.

In this embodiment, the bilirubin concentration is measured using the difference between the absorptance of blue light and the absorptance of green light for bilirubin. A specific method is described below.

In the bilirubin concentration measurement system according to this embodiment, the computing unit <NUM> of the terminal device <NUM> calculates the bilirubin concentration, using information about the intensity of the reflected light of blue light and the intensity of the reflected light of green light, and the following Expression <NUM>. The following Expression <NUM> is an equation for obtaining the bilirubin concentration, the equation is derived using the Lambert-Beer law. <NUM>] <MAT>.

In Expression <NUM>, C is the bilirubin concentration, I(λ<NUM>) is the intensity of reflected light of blue light, I<NUM>(λ<NUM>) is the intensity of blue light incident on the skin of the subject, I(λ<NUM>) is the intensity of reflected light of green light, I<NUM>(λ<NUM>) is the intensity of the green light incident on the skin of the subject, and D and R are specific constants determined for each subject.

When the bilirubin concentration is measured, the control circuit <NUM> causes the light emitting elements <NUM> and <NUM> to emit light at timings shown in <FIG>, for example. That is, the control circuit <NUM> applies a rectangular pulse voltage <NUM> to the light emitting element <NUM> to cause the light emitting element <NUM> to emit green light. After the green light from the light emitting element <NUM> is incident on the skin of the subject, the green light incident on the skin is reflected by the skin of the subject. The reflected light reflected this time is converted into an electric signal (voltage signal) <NUM> by the light detection element <NUM>.

Subsequently, the control circuit <NUM> applies a rectangular pulse voltage <NUM> to the light emitting element <NUM> to cause the light emitting element <NUM> to emit blue light. After the blue light from the light emitting element <NUM> is incident on the skin of the subject, the blue light incident on the skin is reflected by the skin of the subject. The reflected light reflected this time is converted into an electric signal (voltage signal) <NUM> by the light detection element <NUM>.

In the above example, the light emitting element <NUM> (blue light) emits light after the light emitting element <NUM> (green light). The order thereof may be inverted. The blue light has a higher absorptance of light in bilirubin than the green light. Accordingly, as shown in the lower diagram of <FIG>, the electric signal <NUM> corresponding to the blue light has a lower value of the electric signal <NUM> corresponding to the green light.

The electric signals <NUM> and <NUM> detected by the light detection element <NUM> are wirelessly transmitted as information about the intensities of the reflected light, from the sensor device <NUM> to the terminal device <NUM>. The computing unit <NUM> of the terminal device <NUM> calculates the bilirubin concentration, using the information about the intensities of the reflected light obtained from the sensor device <NUM>, and Expression <NUM> described above.

Specifically, the bilirubin concentration C can be obtained by substituting, in Expression <NUM>, the intensity I(λ<NUM>) of the reflected light of blue light and the intensity I(λ<NUM>) of the reflected light of green light, which are the information about the intensities of the reflected light. Here, I<NUM>(λ<NUM>) is the intensity of blue light incident on the skin of the subject, and is a value according to the drive voltage supplied from the control circuit <NUM> to the light emitting element <NUM>, and the property of the light emitting element <NUM>. Accordingly, this value is a known value. Likewise, I<NUM>(λ<NUM>) is the intensity of green light incident on the skin of the subject, and is a value according to the drive voltage supplied from the control circuit <NUM> to the light emitting element <NUM>, and the property of the light emitting element <NUM>. Accordingly, this value is a known value. D and R are specific constants determined for each subject. Consequently, the bilirubin concentration C can be obtained by substituting, in Expression <NUM>, the intensity I(λ<NUM>) of the reflected light of blue light and the intensity I(λ<NUM>) of the reflected light of green light, which are the information about the intensities of the reflected light. Note that in Expression <NUM>, "I(λ<NUM>)/I<NUM>(λ<NUM>)" corresponds to the transmittance of blue light, and "I(λ<NUM>)/I<NUM>(λ<NUM>)" corresponds to the transmittance of green light.

As described above, D and R are specific constants determined for each subject. D is the constant corresponding to the length of a path along which light propagates in the subject. R is the constant corresponding to attenuation of light in the subject.

In this embodiment, the computing unit <NUM> preliminarily measures the bilirubin concentration of each subject to be tested, using other means and/or the bilirubin concentration measurement system <NUM>, and predetermines the constant D and the constant R in the Expression <NUM> for each subject to be tested, using the bilirubin concentration measured using the other means and/or the bilirubin concentration measurement system <NUM>. Hereinafter, a method of determining the constants D and R is described.

First, the bilirubin concentration is preliminarily measured for each subject to be tested, using other means (a blood test etc.). Each of the light emitting elements <NUM> and <NUM> of the sensor device <NUM> is caused to emit light multiple times to obtain multiple data on combinations between the intensities I(λ<NUM>) of the reflected light of blue light and the intensities I(λ<NUM>) of the reflected light of green light.

The bilirubin concentration C preliminarily obtained using the other means, and the multiple values of intensities I(λ<NUM>) and I(λ<NUM>), are substituted in Expression <NUM>, thereby creating simultaneous equations. The unknown constants are the two constants, which are D and R. Accordingly, in principle, the constants D and R can be obtained by solving the two simultaneous equations. For example, multiple constants D and R are obtained, and the obtained constants D and R are statistically processed (for example, mean values are obtained), thereby allowing the accuracies of the constants D and R to be improved. Through use of such a method, the constant D and the constant R can be predetermined for each subject to be tested.

In a case where measurement of variation from an initial value is sufficient for measurement of the bilirubin concentration of a subject (i.e., a case where the relative value of the bilirubin concentration is calculated but the absolute value is not required to be measured), preliminary measurement of the bilirubin concentration using other means (blood test etc.) is unnecessary. That is, in the case where the variation in bilirubin concentration (relative value) is obtained, the constants D and R are temporarily determined. For example, the values of the constants D and R may be determined using previously used data on the constants D and R. The bilirubin concentration measurement system <NUM> is then used to obtain the intensity I(λ<NUM>) of the reflected light of blue light, and the intensity I(λ<NUM>) of the reflected light of green light are obtained, and the values of I(λ<NUM>) and I(λ<NUM>) are substituted in Expression <NUM>, which can obtain the variation in bilirubin concentration (relative value).

As described above, in the case where the constants D and R are predetermined, the absolute value of the bilirubin concentration is subsequently obtained using other means (blood test etc.), thereby allowing the preliminarily obtained relative value of the bilirubin concentration to be converted into the absolute value.

<FIG> is a graph showing the relationship between values measured using a commercially available bilirubin concentration measurement apparatus (apparatus A: R=<NUM>) (abscissa axis) and values measured using a bilirubin concentration measurement system according to the present invention (apparatus B) (ordinate axis). In <FIG>, bilirubin concentrations are obtained for each subject through the two apparatuses, which are the apparatus A and the apparatus B, and these values are plotted. The plotted values correspond respective subjects. When the bilirubin concentration is measured using the bilirubin concentration measurement system according to the present invention, blue light and green light are alternatively emitted every <NUM>, as shown in <FIG>.

As shown in <FIG>, there is a relationship between the values measured using the bilirubin concentration measurement system according to this embodiment (ordinate axis) and the values measured using the commercially available bilirubin concentration measurement apparatus (abscissa axis). That is, the bilirubin concentration measurement system according to this embodiment has a measurement accuracy equivalent to that of the commercially available bilirubin concentration measurement apparatus.

The bilirubin concentration measurement system <NUM> according to this embodiment includes: the sensor device <NUM> attachable to a subject; and the terminal device <NUM> capable of wirelessly communicating with the sensor device <NUM>. The sensor device <NUM> has the configuration that includes the light emitting elements <NUM> and <NUM> and the light detection elements <NUM>. The bilirubin concentration is calculated by the terminal device <NUM>. Consequently, the configuration of the sensor device <NUM> can be simplified, which can reduce the size of the sensor device <NUM>.

The sensor device <NUM> according to this embodiment can be attached to the subject in a state of being in close contact, and continuously monitor the bilirubin concentration of the subject accordingly. That is, the light emitting elements <NUM> and <NUM> can be caused to emit light alternately, and reflected light at this time is detected by the light detection element <NUM>, which can continuously monitor the bilirubin concentration of the subject.

Consequently, the invention according to this embodiment can provide the bilirubin concentration measurement system that is small in size and capable of continuously monitoring the bilirubin concentration.

<FIG> is a diagram for illustrating an example of temporal change in output of the light detection element <NUM>, and shows temporal change when reflected light having a predetermined color (blue or green) is detected by the light detection element <NUM>. As shown in <FIG>, the light detection element <NUM> continuously detects the reflected light. However, the outputs of the light detection element <NUM> sometimes include data <NUM> and <NUM> having higher voltages than a predetermined value V1 (i.e., data having high light intensities). It is assumed that this is because the light detection element <NUM> is temporarily apart from the subject owing to, for example, movement of the subject, and an abnormality temporarily occurs in reflected light detection.

In such a case, the computing unit <NUM> may exclude the data <NUM> and <NUM> temporarily having a higher voltage than the predetermined value V1 (i.e., data having high light intensities), and calculate the bilirubin concentration. The computing unit <NUM> can accurately calculate the bilirubin concentration by excluding such abnormal data <NUM> and <NUM>.

<FIG> is a diagram for illustrating an example of temporal change in output of the light detection element <NUM>, and shows temporal change when reflected light having a predetermined color (blue or green) is detected by the light detection element <NUM>. As shown in <FIG>, while the light detection element <NUM> continuously detects reflected light, the output of the light detection element <NUM> becomes higher than a predetermined value V2 at a certain timing (see an arrow in the graph of <FIG>) and the state is continued in some cases. It is assumed that this is because the sensor device <NUM> (light detection element <NUM>) is apart from the subject owing to, for example, movement of the subject, and an abnormality occurs in reflected light detection.

In such a case, the computing unit <NUM> can determine that the sensor device <NUM> is not correctly attached on the subject. For example, when the computing unit <NUM> determines that the state of the sensor device <NUM> is abnormal, a warning message indicating that the state of the sensor device <NUM> is abnormal may be displayed on the display unit <NUM>. A warning sound may be output from the speaker included in the terminal device <NUM>.

As described above, the bilirubin concentration measurement system <NUM> according to this embodiment can be preferably used for bilirubin measurement for newborns (babies and infants). However, the close contact between the sensor device <NUM> and the skin of a newborn becomes insufficient by movement of the newborn, and light from the light emitting elements <NUM> and <NUM> is reflected by the surface of the skin of the newborn in some cases. In such cases, the reflected light serves as a disturbance. Accordingly, the accuracy of the measured value of the bilirubin concentration sometimes decreases.

The bilirubin concentration measurement system <NUM> according to this embodiment may apply predetermined statistical processing to the output data of the light detection elements <NUM> in order to reduce the adverse effects of such a disturbance.

That is, the light emitting element <NUM> (blue light) is caused to emit light multiple times, and reflected light at the times is detected multiple times by the light detection element <NUM>. The computing unit <NUM> applies the predetermined statistical processing to data corresponding to the intensities of reflected light (reflected light of blue light) detected multiple times. Among statistically processed data corresponding to the intensity of the reflected light, data in a predetermined range are selectively used to calculate the bilirubin concentration. Likewise, the light emitting element <NUM> (green light) is caused to emit light multiple times, and reflected light at the times is detected multiple times by the light detection element <NUM>. The computing unit <NUM> applies the predetermined statistical processing to data corresponding to the intensities of reflected light (reflected light of green light) detected multiple times. Among statistically processed data corresponding to the intensity of the reflected light, data in a predetermined range are selectively used to calculate the bilirubin concentration.

Specifically, the computing unit <NUM> classifies the data corresponding to the intensities of the reflected light detected multiple times, into multiple classes corresponding to the intensities of the reflected light. The bilirubin concentration is then calculated, selectively using data having cumulative relative frequencies in a predetermined range, among the classified data corresponding to the intensities of the reflected light. At this time, the computing unit <NUM> may calculate the bilirubin concentration using the mean value of the selected data. The computing unit <NUM> applies such processes to each of the reflected light of the light emitting element <NUM> (blue light) and the reflected light of the light emitting element <NUM> (green light).

Hereinafter, a specific example of such statistical processing is described with reference to <FIG> and <FIG>. <FIG> is a graph showing an example where the statistical processing is applied to the output of the light detection element (blue light). <FIG> is a graph showing an example where the statistical processing is applied to the output of the light detection element (green light). <FIG> and <FIG> indicate histograms of the outputs of the light detection element <NUM>.

In <FIG> and <FIG>, the abscissa axes indicate the outputs of the light detection element <NUM>, and correspond to the intensities of the reflected light. Each abscissa axis is classified into multiple classes corresponding to the intensities of the reflected light. Data corresponding to the reflected light detected by the light detection element <NUM> (e.g., electric signal values of the light detection element <NUM>) are classified into multiple classes. Each ordinate axis (left side) indicates the relative frequency. That is, the ordinate axis (left side) indicates the value (frequency) obtained by dividing the number of data classified into the individual classes by the number of total measured data (the number of total measurement times). Curves in the graphs of <FIG> and <FIG> indicate the integrated values of the relative frequencies, that is, the cumulative relative frequencies (the ordinate axis on the left side).

The graph shown in <FIG> shows results of continuous measurement for about <NUM> seconds, with the light emitting element <NUM> (blue light) being caused to emit light for about three seconds, in order to survey the overview of the output (electric signal value) of the light detection element <NUM>. <FIG> collectively shows measured results of <NUM> babies and infants, and the number of total measurement times is <NUM>. Likewise, the graph shown in <FIG> indicates results of continuous measurement for about <NUM> seconds, with the light emitting element <NUM> (green light) being caused to emit light for about <NUM> seconds. <FIG> collectively shows measured results of <NUM> babies and infants, and the number of total measurement times is <NUM>. Note that during measurement, the light emitting element <NUM> (blue light) and the light emitting element <NUM> (green light) are alternately caused to emit light, and the individual reflected light is measured.

In <FIG> and <FIG>, each part where the output (electric signal value) of the light detection element <NUM> is high are considered as reflected light that is light from the light emitting elements <NUM> and <NUM> reflected by the surface of the skin, that is, a disturbance. Accordingly, in this embodiment, among the outputs (electric signal values) of the light detection element <NUM>, data having low values (i.e., data of the reflected light having reached below the skin and been reflected) are selectively used, which can improve the accuracy of the measured value of the bilirubin concentration.

Here, the data having low values are data in a range having the cumulative relative frequencies from <NUM> to <NUM> shown in <FIG> and <FIG>. Specifically, the data are the outputs (electric signal values) of the light detection element <NUM> in a range B11 shown in <FIG>. The outputs (electric signal values) of the light detection element <NUM> in a range G11 shown in <FIG>.

For example, the mean value of the outputs (electric signal values) of the light detection element <NUM> in the range B11 indicated in <FIG> may be obtained, and the mean value may be used as information about the intensities of the reflected light of blue light. That is, the mean value may be used as the value of the intensity I(λ<NUM>) of the reflected light of blue light in Expression <NUM>. Likewise, the mean value of the outputs (electric signal values) of the light detection element <NUM> in the range G11 indicated in <FIG> may be obtained, and the mean value may be used as information about the intensities of the reflected light of green light. That is, the mean value may be used as the value of the intensity I(λ<NUM>) of the reflected light of green light in Expression <NUM>. These values may be used to obtain the constant D and the constant R in Expression <NUM>. The bilirubin concentration can be accurately obtained using such a method.

Note that in this embodiment, data in any range may be selected to be used only if the data are included in the range B11 shown in <FIG>. Likewise, data in any range may be selected to be used only if the data are included in the range G11 shown in <FIG>.

In particular, in this embodiment, it is preferable to use data having the cumulative relative frequencies ranging from <NUM> to <NUM> shown in <FIG> and <FIG>. Specifically, it is preferable to use the outputs (electric signal values) of the light detection element <NUM> in a range B12 shown in <FIG>. Furthermore, it is preferable to use the outputs (electric signal values) of the light detection element <NUM> in a range G12 shown in <FIG>.

In a case of obtaining the bilirubin concentration using values in the range B12 shown in <FIG> and values in the range G12 shown in <FIG>, the correlation with the bilirubin concentration measured using the commercially available bilirubin concentration measurement apparatus (apparatus A: R=<NUM>) was specifically favorable.

Note that <FIG> and <FIG> show data on multiple babies and infants in order to survey the overview of the output (electric signal value) of the light detection element <NUM>. However, in actual measurement, for example, by repeating for about <NUM> seconds one time of emission and detection of light every period ranging from <NUM> to <NUM> seconds for each of the babies and infants, <NUM> measured data on the reflected light of blue light, and <NUM> measured data on the reflected light of green light can be obtained at the maximum. The bilirubin concentration can be accurately obtained by applying such a method to the data obtained as described above.

<FIG> is a block diagram for illustrating a system configuration example of a bilirubin concentration measurement system according to this embodiment. The bilirubin concentration measurement system <NUM> shown in <FIG> includes multiple sensor devices 10_0 to 10_n (n is an integer of one or more), and a terminal device <NUM> capable of communicating with these sensor devices 10_0 to 10_n. For example, the bilirubin concentration measurement system <NUM> shown in <FIG> can be used as a system that collectively manages the bilirubin concentrations of multiple newborns in a hospital or the like. That is, the sensor devices 10_0 to 10_n are attached to the respective newborns, and information about the intensities of the reflected light is wirelessly transmitted from each of the sensor devices 10_0 to 10_n to the terminal device <NUM>. Accordingly, the terminal device <NUM> can collectively manage the bilirubin concentrations of the individual newborns.

At this time, the communication units <NUM> of the sensor devices 10_0 to 10_n respectively add pieces of ID information unique to the sensor devices 10_0 to 10_n, and wirelessly transmit the information about the intensities of the reflected light to the terminal device <NUM>. Accordingly, the terminal device <NUM> can identify the transmitter of the information about the intensities of the reflected light, using the added ID information.

As described above, the bilirubin concentration measurement system <NUM> according to this embodiment wirelessly transmits the data from the sensor devices 10_0 to 10_n to the terminal device <NUM>. Accordingly, wiring for connecting the sensor devices with the terminal device can be omitted, which can improve the work environment for nurses and the like in the hospital or the like.

As for the bilirubin concentration measurement system according to this embodiment described above, the case of measuring the bilirubin concentration of the subject using the sensor device <NUM> has been described. However, this embodiment may have a configuration that detects information other than that on the bilirubin concentration using the sensor device <NUM>. For example, multiple vital signs, such as the pulse rate, respiration rate, heart rate, body temperature, brain waves (EEG: electroencephalogram), and blood oxygen saturation level, may be measured over time.

<FIG> is a diagram for illustrating another configuration example of a sensor device included in a bilirubin concentration measurement system according to this embodiment. In the sensor device shown in <FIG>, three light emitting elements <NUM> to <NUM>, and a light detection element <NUM> are implemented on a substrate <NUM>. In the configuration shown in <FIG>, the light detection element <NUM> is arranged at the center position of the three light emitting elements <NUM> to <NUM>. The three light emitting elements <NUM> to <NUM> are elements that emit red light, green light, and blue light, respectively. In the sensor device shown in <FIG>, when the bilirubin concentration is measured, the light emitting element <NUM> (green light) and the light emitting element <NUM> (blue light) are used for measuring the bilirubin concentration. For measuring the blood oxygen saturation level, the light emitting element <NUM> (red light) and the light emitting element <NUM> (green light) are used. As described above, the sensor device is provided with the three light emitting elements <NUM> to <NUM>, which can measure the bilirubin concentration and measure the blood oxygen saturation level. By further implementing a thermistor in the sensor device, the body temperature of a subject can be measured. Such information is wirelessly transmitted to the terminal device <NUM>. Accordingly, multiple vital signs of the subject can be monitored over time in the terminal device <NUM>.

Claim 1:
A bilirubin concentration measurement system (<NUM>), comprising: a sensor device (<NUM>) attachable to a subject; and a terminal device (<NUM>) capable of wirelessly communicating with the sensor device (<NUM>), wherein
the sensor device (<NUM>) comprises:
a first light emitting element (<NUM>) that emits light in a first wavelength band at a first timing;
a second light emitting element (<NUM>) that emits light in a second wavelength band at a second timing;
a light detection element (<NUM>) that detects first reflected light that is the light in the first wavelength band having been incident on skin of the subject and been reflected at the first timing, and detects second reflected light that is the light in the second wavelength band having been incident on the skin of the subject and been reflected at the second timing; and
a first communication unit (<NUM>) that wirelessly transmits information about intensities of the first and second reflected light detected by the light detection element, and
the terminal device (<NUM>) comprises:
a second communication unit (<NUM>) that receives the information about the intensities of the first and second reflected light transmitted from the first communication unit (<NUM>); and
a computing unit (<NUM>) that calculates a bilirubin concentration using the information about the intensities of the first and second reflected light,
wherein:
the light detection element (<NUM>) detects, multiple times, each of the first and second reflected light at the first and second timings, and
the computing unit (<NUM>) applies predetermined statistical processing to data corresponding to the intensities of the first and second reflected light detected multiple times, and calculates the bilirubin concentration selectively using data in a predetermined range among the statistically processed data corresponding to the intensities of the first and second reflected light.