JP2022154291A - Cardiac output measuring sensor and control program of cardiac output measuring sensor - Google Patents

Abstract

To provide a cardiac output measuring sensor capable of estimating cardiac output according to individual differences of measurement object persons.SOLUTION: A cardiac output measuring sensor includes: a transmission antenna 11 for transmitting an electromagnetic wave toward a living body; a reception antenna 12 disposed so as to be opposed with the heart of the living body in between; a primary distribution creation unit 211 for creating waveform data indicating a temporal change in signal strength of the electromagnetic wave received by the reception antenna 12; a cardiac output estimation unit 214 for estimating cardiac output from the waveform data; a biological feature data extraction unit 417 for extracting biological feature data from a signal obtained by receiving the electromagnetic wave transmitted toward the living body; a classification determination unit 418 for classifying features of the living body into biological patterns from the biological feature data; and a correction execution unit 419 for executing correction on the basis of the biological patterns into which the features of the living body are classified for a calculation process of the cardiac output estimation by the cardiac output estimation unit 214.SELECTED DRAWING: Figure 2

Description

The present invention relates to a cardiac output measuring sensor and a control program for the cardiac output measuring sensor.

Conventional technologies related to cardiac output detection include a device disclosed in Patent Document 1, which includes a transmitting antenna, a receiving antenna, and an estimator. In the above device, the transmitting antenna transmits microwaves, etc. to the patient's chest, the receiving antenna receives the microwaves, etc. transmitted from the transmitting antenna and passed through the living body, and the estimating unit calculates the phase of the microwaves received by the receiving antenna. Alternatively, the cardiac output of the subject is estimated based on the signal strength.

WO2018/194093

Conventional techniques estimate the cardiac output from changes in microwaves that have passed through the body due to contraction and expansion of the heart. The signal intensity of the microwave that has passed through the living body differs depending on the individual difference of the person to be measured, for example, the difference in body type and body fat percentage.

However, when estimating the cardiac output, the conventional technique does not take into consideration the individual differences of the measurement subjects, resulting in a decrease in the accuracy of estimating the cardiac output.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cardiac output measuring sensor and a control program for the cardiac output measuring sensor, which can estimate the cardiac output according to the individual differences of the person to be measured. do.

The present invention for achieving the above object is
a transmitting antenna for transmitting electromagnetic waves toward a living body;
a receiving antenna arranged to face the transmitting antenna with the heart of the living body interposed therebetween;
a waveform data creation unit that creates waveform data representing changes over time in signal strength of the electromagnetic wave received by the receiving antenna;
a cardiac output estimation unit that estimates a cardiac output from the waveform data;
a biometric feature data extracting unit for extracting biometric feature data representing features of the living body from a signal obtained by receiving the electromagnetic waves transmitted toward the living body;
a classification determination unit that classifies the biometric features into biometric patterns from the biometric feature data;
a correction execution unit that executes correction based on the classified biometric pattern in the calculation process of the cardiac output estimation by the cardiac output estimation unit;
A cardiac output measurement sensor comprising:

In addition, the present invention for achieving the above object is
a transmitting antenna for transmitting electromagnetic waves toward a living body;
a receiving antenna arranged to face the transmitting antenna with the heart of the living body interposed therebetween;
A control program executed by a computer for controlling a cardiac output measurement sensor for estimating cardiac output using the electromagnetic wave received by the receiving antenna and transmitted through the living body,
step (a) of creating waveform data representing changes over time in signal strength of the electromagnetic wave received by the receiving antenna;
a step (b) of extracting biometric feature data representing features of the living body from the signal obtained by receiving the electromagnetic waves transmitted toward the living body;
a step (c) of classifying the biometric features into biometric patterns from the biometric feature data;
In the step of estimating the cardiac output using the waveform data, the cardiac output is corrected based on the classified biological pattern in a calculation process for estimating the cardiac output. estimating (d)
is a control program having

According to the present invention, biometric feature data representing features of a living body are extracted from signals obtained by irradiating a living body with electromagnetic waves, and are further classified into biometric patterns. It was decided to correct the calculation process of the output amount. As a result, the present invention can obtain a highly accurate cardiac output corresponding to individual differences among measurement subjects.

1 is a schematic perspective view showing the entire cardiac output measurement sensor in the first embodiment; FIG. 1 is a block diagram showing the configuration of a cardiac output measurement sensor according to a first embodiment; FIG. FIG. 2 is a diagram showing a configuration example of a transmitting/receiving antenna in the first embodiment; FIG. It is a figure which shows the structural example of the transmission/reception antenna in a modification. FIG. 11 is a diagram showing a configuration example of a transmitting/receiving antenna in another modified example; FIG. 4 is a schematic diagram showing high-speed switching processing of each antenna element in element scanning processing; 5B is a schematic diagram showing point data obtained by the process of FIG. 5A; FIG. FIG. 5B is a schematic diagram showing waveform data generated from the point data of FIG. 5B; FIG. 10 is a main routine flowchart showing from antenna element determination processing to cardiac output measurement processing; FIG. FIG. 7 is a subroutine flowchart showing processing in step S19 of FIG. 6. FIG. FIG. 4 is a schematic diagram showing an example of waveform distribution data (primary distribution data); 4 is a table showing examples of various evaluation values; FIG. 10 is a schematic diagram for explaining a differential time between peak timings; FIG. 4 is a schematic diagram for explaining a difference in differential time depending on position; FIG. 4 is a schematic diagram showing an example of secondary distribution data created by arranging evaluation values in association with positions of respective antenna elements in the first embodiment; FIG. 7 is a subroutine flowchart showing the process of step S20 of FIG. 6 in the first embodiment; FIG. FIG. 4 is a graph showing an example of respiratory amplitude; FIG. It is a figure which shows the example of classification|category of distribution variance. It is a graph which shows an example of distribution dispersion. 4 is a biometric pattern table showing an example of biometric pattern classification in the first embodiment. 4 is a figure data table showing an example of figure data; 4 is a correction data table showing an example of correction values determined from a combination of biometric pattern and body shape data in the first embodiment; It is a graph for explaining a modification, and is a graph showing waveform data of a microwave signal received corresponding to one certain antenna element r. 4 is a correction data table showing examples of filter coefficients and electric field intensity correction coefficients as correction values in a modified example of the first embodiment; FIG. 7 is a block diagram showing the configuration of a cardiac output measurement sensor according to a second embodiment; FIG. 7 is a subroutine flowchart showing the processing of step S20 of FIG. 6 in the second embodiment; FIG. FIG. 4 is a schematic diagram for explaining the tendency of reflection coefficients with respect to a living body; FIG. 10 is a biometric pattern table showing an example of biometric pattern classification in the second embodiment; FIG. FIG. 11 is a correction data table showing an example of correction values determined from a combination of biometric pattern and body type data in the second embodiment; FIG.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. Also, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios. The technical scope of the present invention is not limited to the embodiments described below, and various modifications can be made within the scope of the claims.

FIG. 1 is a schematic diagram showing the entire cardiac output measurement sensor 1000 according to the first embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the cardiac output measurement sensor 1000 according to the first embodiment, and FIG. 3 is a diagram showing a configuration example of a transmitting/receiving antenna according to the first embodiment.

FIG. 1 shows a state in which a patient 90 (also referred to as a living body or subject) is lying on a bed 95 (supine position). The cardiac output measurement sensor 1000 measures (estimates) the amount of blood pumped from the heart, such as the cardiac output of the patient 90 . For example, the cardiac output measurement sensor 1000 is used for examination of heart failure, follow-up observation after heart surgery, verification of drug effects and side effects of heart disease, and the like.

At the time of measurement, a user such as a nurse or a doctor aligns the line connecting the centers of the transmitting antenna 11 and the receiving antenna 12 with the heart 91. They are arranged so as to face each other with the heart 91 interposed therebetween. In order to reduce the influence of external radio waves, a radio wave shield made of cloth may be used to cover the chest of the patient 90 and the entire transmitting/receiving antenna during measurement. For example, receive antenna 12 is positioned below patient 90 and transmit antenna 11 is positioned above patient 90 . Specifically, the receiving antenna 12 is placed on a bed 95 on which the patient 90 lies supine. The upper transmitting antenna 11 is attached to a U-shaped movable fixed base (not shown) when viewed from the side. This fixed base can manually adjust the height of the transmitting antenna 11 . The transmitting antenna 11 is arranged above the patient 90 while being slightly separated from the patient 90 by a fixed base. The purpose of the separation is not to interfere with the patient's 90 breathing and to prevent unintended movement of the transmitting antenna 11 due to contact with the patient 90 . Note that the arrangement of the transmitting and receiving antennas is not limited to the arrangement shown in FIG. 1 and the like. The transmission and reception antennas may be arranged upside down, for example, with the transmission antenna 11 arranged below the patient 90 (back side) and the reception antenna 12 arranged above the patient 90 (front side). .

As shown in FIG. 2 , cardiac output measurement sensor 1000 includes transmitting antenna 11 , receiving antenna 12 , and device main body 20 . The apparatus main body 20 is mounted on a movable frame (not shown) and arranged beside the bed 95 . The device main body 20 operates with an internal battery or power supplied from a commercial power source. Both antenna units are connected to the device main body 20 through the signal cable 13, through which data signals are transmitted and received and power is supplied. The transmitting/receiving antenna will be described later.

(Device body 20)
The apparatus main body 20 includes a transmission/reception controller 14 , a control section 21 , a storage section 22 , an input/output I/F (interface) 23 and a communication I/F 24 .

(transmission/reception controller 14)
Transmit/receive controller 14 is electrically connected to transmitting antenna 11 and receiving antenna 12 via signal cable 13 . Under the control of the control unit 21 , the transmission/reception controller 14 controls the timing of transmission/reception between both antenna units and acquires measured values (received signals) from the reception antenna 12 .

(control unit 21)
The control unit 21 includes a CPU, RAM, ROM, etc., and controls each unit in the device according to a program stored in the ROM or the storage unit 22 . By executing a program, the control unit 21 controls a primary distribution generation unit 211, a secondary distribution generation unit 212, an element determination unit 213, a cardiac output estimation unit 214, an installation state determination unit 215, an instruction unit 216, a biological It functions as a feature data extraction unit 417 , a classification determination unit 418 , a correction execution unit 419 , and a body type data acquisition unit 420 . The primary distribution generator 211 also includes a point data recorder 301 and a waveform data generator 302 .

The primary distribution generating unit 211 generates waveform data representing temporal changes in measured values measured for each antenna element by the functions of the point data recording unit 301 and the waveform data generating unit 302 (hereinafter referred to as “pre-processing”). ). The primary distribution generator 211 also generates waveform distribution data by associating the waveform data with each antenna element (hereinafter referred to as "post-processing").

The secondary distribution creating unit 212 calculates evaluation values (described later) and creates distribution data of the evaluation values according to the positions of the antenna elements.

The element determination unit 213 determines antenna elements to be used in estimating the cardiac output based on the waveform distribution data created by the primary distribution creation unit 211 . That is, the element determining unit 213 uses the distribution data of the evaluation values created by the secondary distribution creating unit 212 based on the waveform distribution data created by the primary distribution creating unit 212 when estimating the cardiac output. Determine the antenna elements to be used for Further, the element determination unit 213 may determine the antenna elements to be used in estimating the cardiac output based on the calculated evaluation value based on the waveform distribution data created by the primary distribution creation unit 211. good.

The cardiac output estimator 214 estimates (calculates) the cardiac output of the patient 90 , that is, the volume of blood pumped from the heart 91 .

The installation state determination unit 215 determines whether the installation state of the transmission/reception antenna (antenna array) is appropriate.

The instruction unit 216 functions as a first instruction unit, and outputs an instruction for re-measurement or rearrangement according to the determination result of the installation state determination unit 215 . In addition, the instruction unit 216 functions as a second instruction unit and instructs the moving direction of rearrangement.

The biometric feature data extracting unit 417 extracts biometric feature data representing biometric features from the waveform data for each antenna element created by the primary distribution creating unit 211 (waveform data creating unit).

The classification determination unit 418 classifies predetermined features of each living body as biometric parameters from the biometric feature data acquired by the biometric feature data extraction unit 417 .

The correction executing unit 419 corrects the calculation process of estimating (calculating) the cardiac output by the cardiac output estimating unit 214 for each classified biological pattern. By performing the correction by the correction execution unit 419, the cardiac output estimation unit 214 can estimate (calculate) the cardiac output corrected in accordance with the body type.

The body type data acquisition unit 420 acquires the body type data of the person to be measured.

The details of the functions of these units in the control unit 21 will be described later.

(storage unit 22)
The storage unit 22 is composed of a semiconductor memory in which various programs and various data are stored in advance, or a magnetic memory such as a hard disk. Further, the storage unit 22 stores point data, waveform data, waveform distribution data, comparative distribution patterns, setting ranges of cardiac output characteristic data, FFT data, frequency components that are noise components, and the like (all of which will be described later). . The storage unit 22 also stores position information of antenna elements (antenna elements r1 to rx or t1 to tx, which will be described later) in the antenna array. The positional information is, for example, XY coordinates on the substrate and relative positional relationship (distance, direction) information.

(Input/output I/F 23)
The input/output I/F 23 functions as an input/output unit, has input/output terminals conforming to the USB and DVI standards, etc., and is connected to input devices such as a keyboard, mouse, and microphone, and output devices such as a display, speaker, and printer. It is an interface to In the example shown in FIGS. 1 and 3, the input/output I/F 23 is connected to the touch panel 51 . Also, an XY stage 52 may be connected. The touch panel 51 is composed of a liquid crystal panel and a touch pad superimposed thereon, and receives instructions from the user to start antenna element determination processing and cardiac output measurement. The XY stage 52 moves at least one of the two antenna units according to the rearrangement instruction from the instruction unit 216 to change the arrangement position. Input/output devices such as the touch panel 51 and the XY stage 52 may be included in the device main body 20 or the cardiac output measurement sensor 1000 .

(Communication I/F 24)
The communication I/F 24 is an interface that transmits and receives data via wired or wireless communication with an external terminal device such as a PC (personal computer), tablet terminal, or the like via a network or peer-to-peer. Wired communication may use network interfaces conforming to standards such as Ethernet (registered trademark), SATA, PCI Express, IEEE1394, etc., and wireless communication may use wireless communication interfaces such as Bluetooth (registered trademark), IEEE802.11, 4G, and the like. may be used. In the example shown in FIGS. 1 and 3, a PC 61 is connected to the communication I/F 24 .

(Transmitting antenna 11)
As shown in FIGS. 2 and 3, the transmitting antenna 11 includes a substrate 110, a transmission waveform generator 111, and an antenna element t1. In the first embodiment shown in FIG. 3, the transmitting antenna 11 is provided with a single antenna element t1, and the receiving side is provided with a plurality of antenna elements (one pair configuration).

The transmitting antenna 11 transmits electromagnetic waves (radio waves) that pass through a living body. The substrate 110 is a rectangular plate-shaped member with each side of several tens mm to two hundred and several tens mm. As the antenna element t1, a patch antenna, a dipole-type linear antenna, or a loop antenna having a side or a diameter of several tens mm to a hundred and several tens mm can be applied. For example, antenna element t1 is a patch antenna.

Transmission waveform generator 111 includes a radio wave generator. The frequency of the generated electromagnetic wave is not particularly limited as long as it can pass through the heart 91 of the living body without ionizing action. For example, microwaves with a frequency of 300 MHz to 30 GHz are preferred, and microwaves with a frequency of 400 M to 1.0 GHz are more preferred. Microwaves are suitable for measuring cardiac output because of their bio-penetrability and high sensitivity (rate of change in electric field strength) due to changes in loss during contraction and expansion of the heart 91 . The power of the radio waves to be generated is not particularly limited as long as sufficient power can be detected by the receiving antenna 12, but may be several mW to several tens of mW, for example. Further, the generated radio wave may be a continuous wave, a pulse wave, or a phase-modulated or frequency-modulated radio wave.

(receiving antenna 12)
As shown in FIGS. 2 and 3, the receiving antenna 12 includes a substrate 120, an antenna array 121, a high speed switching section 122, and a sampling section 123. FIG. The antenna array 121, the high-speed switching unit 122, and the sampling unit 123 are all formed on a rectangular plate-shaped substrate 120, each side of which is several tens mm to two hundred and several tens mm.

Antenna array 121 is composed of a plurality of antenna elements r1 to rx (hereinafter collectively referred to as "antenna element r" (the same applies to antenna element t). Also referred to as "element" in the drawings). , are arranged in a grid on the same plane on the surface of the planar substrate 120 . By configuring the transmitting side with a single antenna element t and the receiving side with a plurality of antenna elements r, the position of the transmitting antenna that creates the electric field becomes constant, and the electric field by electromagnetic waves is stabilized.

In the first embodiment shown in FIG. 3, a dipole linear antenna or a minute loop antenna can be applied as each antenna element r. The antenna elements r are, for example, loop antennas each having a side or a diameter of several millimeters to ten and several millimeters. Adjacent antenna elements r are arranged without being in close contact with each other. The size of the entire antenna array 121 is set to be larger than the size of the heart 91 when viewed from the back side of the living body. Specifically, the size of the entire antenna array 121 is, for example, a rectangular shape with one side of 100 to 500 mm, and may be equal to or larger than the chest width of a general adult male.

Also, the total number of antenna elements r is preferably 40 or more and 100 or less. From the viewpoint of positional accuracy (positional resolution) when determining antenna elements r to be used, which will be described later, the number is preferably 40 or more. The upper limit number is preferably 100 or less from the viewpoint of one cycle time tc (sampling rate) calculated by multiplying the period ts by the total number and from the viewpoint of cost. For example, in the example shown in FIG. 3, each antenna element r is a substantially rectangular loop antenna of 12 mm, and the antenna array 121 is composed of a total of 49 antenna elements r1 to r49, 7 in length and 7 in width. Adjacent antenna elements r are arranged at intervals of about 2 mm, and the size of the entire antenna array 121 is about 100 mm square. Hereinafter, the horizontal axis (the row direction of rows A to G described later) is also referred to as the X direction, and the vertical axis (the column direction of columns 1 to 7 described later) is also referred to as the Y direction. The positional information (XY coordinates) of each of these antenna elements r is stored in the storage unit 22 as described above, and used for the processing of the secondary distribution generation unit 212 .

By setting the overall size and number of the antenna array 121 to the above size and number, it is possible to ensure that at least one antenna element corresponds to the targeted portion of the heart. The overall size and number of antenna arrays 121 are not limited to the size and number described above.

The high-speed switching unit 122 is composed of a plurality of switching elements s1 to sx (hereinafter collectively referred to as "switching elements s") corresponding to the respective antenna elements r1 to rx. In high-speed switching section 122, only one switching element s (for example, element s1 (see FIG. 2)) is turned ON, and all other switching elements s (for example, elements s2 to sx) are turned OFF. When a plurality of antenna elements are operated in the ON state at the same time, the antennas are coupled to each other and operate as one antenna, which may make it impossible to obtain a desired measurement value. In order to avoid such a phenomenon, the high-speed switching unit 122 turns ON only one antenna element r (and the transmission antenna element t in the example of FIG. 4A and the like).

The high-speed switching unit 122 also controls the termination condition of the antenna element r in the OFF state, that is, grounds the antenna element r in the OFF state at high frequencies. By doing so, it is possible to reduce the influence of induction disturbances and the like caused by the antenna element in the OFF state.

The sampling section 123 includes a sampling circuit, an AD conversion circuit, and a buffer circuit. The sampling unit 123 samples the radio signal received by the ON-state antenna element r (for example, the element r1), and converts the electric field intensity into a digital signal (measurement value). The digitized measurement values corresponding to each antenna element r are sent to the transmission/reception controller 14 of the device main body 20 either sequentially or collectively in predetermined units (for example, one cycle period).

(Modified example of transmitting/receiving antenna)
FIG. 4A is a diagram showing a configuration example of transmission/reception antennas in a modification (many-to-many), and FIG. 4B is a diagram showing a configuration example of transmission/reception antennas in another modification (many-to-one).

In the first embodiment (one-to-many) shown in FIG. 3 described above, a plurality of antenna elements are arranged on the receiving antenna 12 side. That is, the receiving antenna 12 has an antenna array 121 and a high-speed switching section 122 that controls switching of the antenna array 121 . However, as in the modification shown in FIG. 4A, a plurality of antenna elements t1 to tx may also be arranged on the transmitting antenna 11b side. That is, as shown in FIG. 4A, the transmission antenna 11b may include a transmission waveform generation section 111, an antenna array 113, and a high-speed switching section 112 that controls switching of the antenna array 113. FIG. Note that the antenna array 113 and the high-speed switching section 112 have the same configurations as the antenna array 121 and the high-speed switching section 122 of the receiving antenna 12, and thus description thereof is omitted.

Further, as in another modification (many-to-one) shown in FIG. 4B, one antenna element may be used on the receiving antenna 12b side. The receiving antenna 12b shown in FIG. 4B is composed of one receiving antenna r1 and a sampling section 123 connected thereto. It should be noted that the number of transmitting and receiving antenna elements constituting the antenna array in the embodiments of FIGS. 3, 4A, and 4B is merely an example, and may be at least 49 or may be more. For example, the number of antenna elements t in the transmitting antenna array 113 may be several or may be 100 or more, and the number of antenna elements r in the receiving antenna array 121 may be several or 100 or more. may The lower bounds of these numbers affect the positional accuracy of the placement of the antenna elements, and the upper bounds affect the sampling rate. If the number is increased, one cycle time tc becomes longer, the sampling rate becomes lower, and correct waveform data (see FIG. 5C described later) cannot be obtained.

In both the modification (many-to-many) shown in FIG. 4A and the modification (many-to-one) shown in FIG. 4B, the size of the transmitting antenna array 113 is, for example, a rectangular and more preferably equal to or greater than the width of the patient's 90 chest.

Note that when comparing the configuration in which the receiving antenna 12 side is an array shown in FIG. 3 and the configuration in which the transmitting antenna 11b side is an array shown in FIG. Antenna elements suitable for measuring cardiac output can be selected more accurately than the configuration in which the antenna 11b side is an array.

(Pre-processing of primary distribution generation unit 211)
Next, with reference to FIGS. 5A to 5C, pre-processing up to waveform data generation by the primary distribution generator 211 will be described. This pre-processing is mainly performed by the point data recording unit 301 and the waveform data generating unit 302, as described below. In the following description, the configuration of the transmitting/receiving antennas will be described as being a configuration example similar to that of the first embodiment shown in FIG. 3 (the same applies to FIG. 6 and subsequent figures). In this case, as described below, the point data recording unit 301 records, as point data, the measurement values obtained for each of the antenna elements r turned on by the high-speed switching unit 122 in association with each of the antenna elements r. .

Note that when the modification (many-to-many) shown in FIG. 4A is applied, the antenna element t on the transmitting side and the antenna element r on the receiving side are sequentially switched by the high-speed switching sections 112 and 122 . That is, at a certain time, both antenna units are synchronized and switched at high speed so that only the propagation paths of one system of antenna elements t and r are activated at the same time. In this case, the point data recording unit 301 records the measurement values of the antenna elements t and r turned on by the high speed switching units 112 and 122 as point data in association with the antenna elements t and r. For example, at a certain time, received signals transmitted and received on the propagation paths of the transmitting antenna element tx and the receiving antenna element rx are linked to these transmitting and receiving antennas tx and rx and recorded as point data. In another modified example (many-to-one) shown in FIG. 4B, each antenna element tx (and one antenna element r1) is associated with a similar process and recorded as point data.

FIG. 5A is a schematic diagram showing high-speed switching processing of each antenna element in the element scanning processing. The transmission/reception controller 14 controls the high-speed switching unit 122 during the element scanning process (corresponding to steps S101 to S107 in FIG. 6, which will be described later). FIG. 5A shows an example in which the cyclic mode is the "all cyclic mode" and the predetermined period ts is set to 100 μsec. During the element scanning process, the high-speed switching unit 122 sequentially switches ON/OFF of each of the antenna elements r1 to r49 at the cycle ts in accordance with the setting of the cyclic mode and cycle. Note that there is a "partial circulation mode" as another circulation mode. In this partial circulation mode, only some of the antenna elements r in the antenna array 121 are thinned out and made to make one circulation. For example, alternate antenna elements r such as antenna elements r1, r3, r5, .

Also, the period ts and/or one cycle time tc can be set to any value. For example, the period ts can be set to any value between 10 μsec and 1 msec. One cycle time tc can be set to any value between 1 msec and 100 msec according to the setting of the cycle ts, or the wait time can be adjusted by fixing the cycle ts (for example, fixed at 100 μsec) regardless of the cycle ts. By doing so, one cycle time tc may be arbitrarily set between 5 and 100 msec. The setting of the cyclic mode and period/one cycle time may be performed by the user, or may be performed automatically by the control unit 21 side. The setting of the cyclic mode and cycle may be performed by the user, or may be performed automatically by the control unit 21 side.

When it is automatically performed by the control unit 21, it is changed in multiple steps, for example, from the viewpoint of shortening the scanning time and reducing the required memory capacity. This multistep change may be performed in a series of element scanning processes (see FIG. 6), or may be changed when re-measurement (12B, etc., to be described later). For example, first, it is operated in a partial recursive mode with half or quarter decimation to roughly determine antenna element candidates, then the periphery of the surrounding antenna elements is operated, and more finely, the reception characteristics of the antenna elements are determined. judge. First, the period ts is shortened to roughly determine antenna element candidates, and then the period ts is lengthened by the reciprocal (for example, doubled) for the reduced number (for example, half) of the antenna elements. to determine the reception characteristics of the candidate antenna elements in more detail.

The sampling unit 123 acquires a reception signal corresponding to the electric field strength received by the antenna element r in the ON state. The point data recording unit 301 acquires this reception signal via the transmission/reception controller 14, associates it with each element r, and temporarily records it in the storage unit 22 or RAM.

FIG. 5B is a schematic diagram showing point data obtained by the processing of FIG. 5A. Acquisition timings of adjacent antenna elements r are shifted by one period ts (100 μsec). For example, the acquisition time of the point data p12 of the element r2 is delayed by the period ts from the acquisition time of the point data p11 of the element r1. Similarly, the point data p149 of the last antenna element r49 is delayed by 48 periods ts (4.8 msec) from the point data p11 of the element r1. Also, in one element, adjacent point data are spaced for one cycle time tc. For example, the point data p21 is acquired one cycle time tc after the point data p11 of the element r1. One cycle time tc can be calculated by multiplying the total number (the number of combinations in the case of many-to-many) by the period ts. For example, in FIG. 5B, one cycle time tc is 4.9 msec (=49×100 μsec). In addition, in FIG. 5B and below, the numerical value is rounded and 4.9 msec is expressed as 5 msec.

FIG. 5C is a schematic diagram showing waveform data generated from the point data of FIG. 5B. This waveform data is obtained by collecting the point data recorded by the point data recording unit 301 by the waveform data generating unit 302 for each element r and arranging them chronologically. FIG. 5C shows, as a representative, waveform data w1 of one element r, which captures changes in signal intensity due to cardiac output. This waveform data is composed of a large number of point data p11, p21, p23, etc. linked to this element r.

(Range of predetermined cycle ts)
The upper limit of the cycle ts is a cycle such that one cycle time tc in which a plurality of antenna elements r are turned ON is sufficiently shorter than the cardiac cycle. Specifically, the maximum heart rate is 180 beats/minute, ie, 3 Hz, in consideration of heart disease. In general, the sampling rate for generating a waveform with good accuracy is preferably 30 Hz (33 msec), which is 10 times or more. Dividing this by 40, which is the lower limit number in the preferred range of 40 to 100 total number of antenna elements r, gives 0.8 msec. The upper limit of the period ts was set to 1.0 msec (assuming a sampling rate of about 8 times), which is slightly wider than this. Note that the lower limit of the period ts is appropriately determined depending on the stability of sampling that depends on the circuit configuration. For example, the lower limit of the period ts is several tens of microseconds. In particular, one cycle time tc is set to a period that is sufficiently shorter than the cardiac cycle, for example, 1 msec or less, so that a sufficient sampling rate can be secured and a waveform can be generated with high accuracy.

(From antenna element determination processing to cardiac output measurement processing)
FIG. 6 is a main routine flow chart showing from the antenna element determination process to the cardiac output measurement process.

(Step S11)
The control unit 21 starts transmission/reception by the transmission/reception antenna in response to the user's instruction to start measurement. Specifically, the user arranges the transmitting antenna 11 and the receiving antenna 12 so as to face each other with the heart 91 interposed therebetween. Thereafter, the user inputs an instruction to start measurement using the touch panel 51, keyboard, or the like. At this time, the user may set the circulation mode and the period ts. 5A to 5C, the cyclic mode is the full cyclic mode, the number of elements is 49, the period ts is 100 μsec, and the cycle time tc is 5 msec.

(Element scanning process (S12 to S17))
The processing from steps S12 to S17 is element scanning processing. In this element scanning process, each antenna element r is sequentially scanned in order to determine the antenna element r suitable for measuring the cardiac output, that is, the antenna element r best arranged relative to the heart 91 from among the plurality of antenna elements. to collect the measurement signal. During execution of the element scanning process, the transmitting antenna 11 continues to transmit microwaves, or transmits pulse waves in accordance with the switching timing of the antenna element r on the receiving side.

(Step S12)
In step S12, the control unit 21 performs loop a processing between step S16 and step S16. In this loop a, the target antenna elements r are sequentially switched one by one from the antenna element r1 to the last antenna element rx (r49) according to the setting of the all-loop mode.

(Step S13)
The high-speed switching unit 122 switches the target antenna element r to the ON state. For example, the antenna element r1 is changed from the OFF state to the ON state, and if there is another antenna element r in the ON state, it is changed to the OFF state.

(Step S14)
The sampling unit 123 acquires the measured value at the antenna element r in the ON state.

(Step S15)
The point data recording unit 301 records the measured value obtained in step S14 as point data in association with the target antenna element r. Note that this step S15 may be processed collectively in a predetermined unit (for example, 49 pieces in one cycle period). For example, the buffer of the sampling unit 123 holds data of a predetermined unit. The point data recording unit 301 collectively acquires the data of the predetermined unit and processes them collectively.

(Step S16)
If it is not the last antenna element rx, the target antenna element r is changed to the next one at the predetermined cycle ts, and the loop processing from step S12 onward is repeated. If it is the last antenna element rx, the loop is exited and the process proceeds to step S17.

(Step S17)
The control unit 21 determines whether or not the termination condition is satisfied, and if satisfied (YES), the process proceeds to step S18, and if not satisfied (NO), loop processing from step S12 onward is repeated. The termination condition is, for example, when a period of time corresponding to one to several heartbeats (for example, several seconds to ten and several seconds) has elapsed, or when the number of repetitions (hundreds to thousands) has been reached.

(Step S18)
A waveform data generator 302 generates waveform data for the elements r1 to rx from the point data. For example, waveform data as shown in FIG. 5C is generated. Up to this point, the first-stage processing by the primary distribution generation unit 211 is performed.

(Step S19)
Here, the primary distribution generator 211, the secondary distribution generator 212, and the element determiner 213 work together to determine the antenna element r with the best characteristics. FIG. 7 is a subroutine flow chart showing the process of step S19.

(Step S511)
Here, the primary distribution generation unit 211 performs post-processing. That is, the primary distribution creating unit 211 creates waveform distribution data by associating the waveform data of each antenna element r created in step S18 with each antenna element r. FIG. 8 is a schematic diagram showing an example of waveform distribution data created in step S511. The waveform distribution data are waveform data arranged in association with each antenna element r. Waveform distribution data will also be referred to as primary distribution data hereinafter.

(Step S512)
The secondary distribution generator 212 evaluates the waveform corresponding to each antenna element r based on the primary distribution and calculates an evaluation value. Then, evaluation value distribution data (hereinafter also referred to as “secondary distribution data”) corresponding to the position of the antenna element r is created. FIG. 9 is a table showing examples of various evaluation values. As the index of the evaluation value calculated by the secondary distribution generator 212, any one of indices 1 to 6 as shown in the figure may be used, or a combination thereof may be used.

(1) The “amplitude of waveform data” of index 1 is the amplitude of one waveform included in the waveform data. A waveform having a frequency close to a normal cardiac cycle is extracted, and the amplitude of the waveform is obtained as an evaluation value of index 1. If the waveform data contains several waveforms, the average value of the amplitudes may be used. As preprocessing for obtaining this evaluation value, a bandpass is applied to exclude frequencies outside a specific frequency (0.5 to 3 Hz) corresponding to the normal cardiac cycle range (30 to 180 beats/minute). Noise removal processing may be performed using a filter. The positional relationship between the antenna elements and the heart can be estimated from the amplitude of the waveform data. Note that the "amplitude" here is not the amplitude of the microwave, but the fluctuation range of the received intensity of the microwave accompanying the heartbeat (the same shall apply hereinafter unless otherwise specified).

(2) Index 2, ``intensity at a specific frequency after Fourier transform'', is obtained by performing FFT processing on the waveform data, and performing FFT processing on the frequency corresponding to the cardiac cycle and a specific frequency (0 0.5 to 10 Hz) is obtained as an evaluation value of index 2. The positional relationship with the heart can be estimated from the intensity distribution at specific frequencies.

(3) Index 3 is the “inflection point time of waveform data”. The inflection point time can be calculated by second-order differentiating the waveform data. The evaluation value of index 3 is an evaluation value representing the shape of the waveform. Since the shape of the waveform tends to change depending on the positional relationship between the antenna element and the heart, the positional relationship with the heart can be estimated from the evaluation value of this index 3.

(4) Index 4 is the "time integral value of waveform data" and can be calculated by time integration of one waveform.

(5) Index 5 is an "autocorrelation coefficient" and can be calculated from waveform data including multiple waveforms. The autocorrelation coefficient is an evaluation value representing the similarity of consecutive waveforms. Since the waveforms of antenna elements with stable waveform acquisition are considered to have little change, antenna elements with high waveform similarity (large autocorrelation coefficient) of consecutive antenna elements should be used for cardiac output estimation. use.

(6) Index 6 is the "difference time between peak timings". The secondary distribution generator 212 first calculates the peak timing at which the signal intensity associated with the contraction (or expansion) of the heart 91 becomes maximum (or minimum). Next, the difference time is calculated by comparing this peak timing with the reference waveform. A reference waveform is predetermined waveform data of one of the antenna elements r. For example, it is waveform data of an antenna element r near the center of the antenna array 121 (for example, antenna element r25). The heart tends to be near the antenna element r whose peak timing is advanced. The reason for this is that the peak of the blood flow pumped from the heart is thought to arrive later with increasing distance from the heart.

Here, index 6 will be described in more detail with reference to FIGS. 10A and 10B. FIG. 10A is a schematic diagram for explaining the differential time between peak timings. FIG. 10B is a schematic diagram showing the difference in differential time depending on the position. FIG. 10A shows the waveform at the target antenna element rx (eg, element r1) and the reference waveform. The reference waveform is waveform data obtained from the central antenna element r25 as described above.

The secondary distribution generation unit 212 calculates the differential time between the peak timings of the waveform data created from the point data of the two target antenna elements r1 and the reference antenna element r25 measured simultaneously or substantially simultaneously, and calculates the evaluation value from this differential time. Calculate Here, the waveform data created from the point data measured substantially simultaneously is created from the point data measured at a cycle such that one cycle time tc is sufficiently shorter than the cardiac cycle, as described with reference to FIG. 5A. This is the waveform data. "Simultaneous" literally means waveform data created from point data obtained by simultaneously measuring electromagnetic waves transmitted from one transmitting antenna element t by a plurality of antenna elements r. In this case, point data measured by antenna elements rx, which are separated from each other by a certain distance, are used so that the antennas are not coupled to each other and operate as one antenna.

FIG. 10B shows changes in differential time of waveform data when measuring while displacing the position of an antenna element r in the X direction. In the experiment of FIG. 10B, unlike the embodiment, an electrocardiogram waveform is used as a reference waveform when calculating the differential time. As shown in FIG. 10B, the difference time (delay time) is the largest (absolute value) at the left end, gradually decreases by moving in the positive direction of the X direction, and becomes the minimum in the range of -10 to -30 mm. , -40 also show an increasing trend. It is believed that this delay time is caused by differences in motion between different locations of the heart (left ventricle, right ventricle, or portions thereof). For this reason, as the relative position of the antenna element r to the heart 91 increases, that is, the propagation path of the radio wave between the antenna element t of the receiving antenna 12 and the antenna element r becomes closer to the center of the heart 91 (especially Left ventricle), the delay time of the peak becomes longer. That is, for the evaluation value of index 6, the secondary distribution generating unit 212 calculates a higher evaluation value as the difference time is smaller (or the peak timing is the earliest). Then, the element determination unit 213 selects the antenna element r having the highest evaluation value from the plurality of antenna elements r.

The secondary distribution creating unit 212 creates secondary distribution data using at least one of the indices 1 to 6 as described above. The secondary distribution data represents the position (XY coordinates) of each antenna element r and the distribution of evaluation values calculated from the waveform data of the antenna element r.

(Step S513)
The element determination unit 213 determines antenna elements to be used for estimating the cardiac output from the secondary distribution data created in step S512. FIG. 11 is a schematic diagram showing an example of secondary distribution data created by arranging the evaluation values in association with the positions of the antenna elements r according to the first embodiment. In the example shown in FIG. 11, six levels of gradation from 0 to 5 are schematically shown according to the evaluation value. The higher the level, the higher the evaluation value and the antenna element r with the most suitable characteristics. Normally, the antenna element r with a better positional relationship with the heart 91 (particularly the left ventricle) has a higher evaluation value.

The element determination unit 213 determines the antenna element r32 at the position E4 (column 4, row E) with the highest evaluation value in the example of the secondary distribution data shown in FIG.

As shown in FIG. 11, the level of the evaluation value is highest at a certain position (for example, position E4 in FIG. 11), and the evaluation value changes as the distance from that position increases. For this reason, the element determination unit 213 calculates the peak position by polynomial approximation of the secondary distribution data on the X-axis, Y-axis, or XY plane. The antenna element r may be selected (determined) as the antenna element r for cardiac output measurement. Further, the element determination unit 213 may determine the antenna element r for cardiac output measurement by comparing with the comparison distribution pattern stored in the storage unit 22 . As another example, the element determination unit 213 determines the heart rate from the evaluation values (for example, indices 1 to 5) calculated by the secondary distribution generation unit 212 (without going through the generation of the secondary distribution data). An antenna element r for output amount measurement may be determined. As described above, the processing in the subroutine flowchart of FIG. 7 is completed, and the processing returns to that of FIG.

(Step S20)
Here, biometric feature data extraction unit 417, classification determination unit 418, correction execution unit 419, and body type data acquisition unit 420 cooperate to extract biometric feature data from waveform data, classify biometric patterns, and Furthermore, a correction value is determined. FIG. 12 is a subroutine flowchart showing the processing of step S20.

(Step S811)
First, the biometric feature data extraction unit 417 extracts biometric feature data from the waveform data for each antenna element r created in step S18. The biometric feature data extracted from the waveform data is, for example, a change in microwave signal intensity (respiratory amplitude) and distribution variance associated with respiration.

A change in microwave signal intensity associated with respiration can be obtained, for example, by extracting a waveform synchronized with respiration timing from waveform data of each antenna element. In addition, the change in the signal strength of the microwave accompanying respiration can be obtained, for example, by performing a fast Fourier transform (FFT) on the waveform data for each antenna element r, and extracting the frequency component whose frequency is close to the respiration timing frequency. be done. In this case, the strength of the extracted frequency component can be used as the signal strength. In addition, changes in signal strength associated with respiration are distributed over more antenna elements than changes in signal strength associated with cardiac output. Therefore, if there is a change in signal strength that spreads over more antenna elements r, it may be determined that the change in signal strength is due to respiration.

FIG. 13 is a graph showing an example of respiratory amplitude. FIG. 13 shows respiratory waveforms of the first body type and the second body type. Here, the first body type and the second body type are such that the chest circumference of the person with the first body type<the chest circumference of the person with the second body type.

As shown in FIG. 13, the respiratory amplitude differs depending on the body type of the person to be measured, and the amplitude a of the person with the first body type is larger than the amplitude b of the person with the second body type. This is because the movement of the chest due to respiration, particularly the change in the direction sandwiched between the antennas, is greater for people with the first body type than for people with the second body type. Loss of microwaves to living organisms tends to increase as changes in living organisms increase. For this reason, the amplitude a of the person with the first body type having a large change in the chest is larger than the amplitude b of the person with the second body type.

The dispersiveness indicates the extent to which the change in microwave signal intensity (that is, the amplitude) due to respiration is spread. For example, the distribution dispersion is the number of antenna elements r whose amplitude is greater than or equal to a predetermined amplitude with respect to the maximum amplitude and its spread. More specifically, classification determination section 418 first obtains the maximum amplitude among all antenna elements r. Subsequently, the classification determination unit 418 extracts the antenna element r whose amplitude is equal to or greater than a predetermined amplitude with respect to the obtained maximum amplitude, and obtains its position. The predetermined amplitude is, for example, 80% or more of the maximum amplitude.

In this embodiment, this distribution dispersion is classified according to the arrangement and number of antenna arrays in the matrix. FIG. 14 is a diagram showing an example of classification of distribution dispersion. FIG. 14(a) shows that when the spread of the antenna elements where the amplitude of the signal due to respiration is 80% or more of the maximum amplitude is the range of a total of nine antenna elements of 3 rows and 3 columns, the dispersion is "1". ”. Similarly, in FIG. 14(b), the dispersibility is set to "2" in the case of a range of 25 antenna elements in total of 5 rows and 5 columns. Similarly, in FIG. 14(c), the dispersibility is set to "3" in the case of a range of 49 antenna elements in total of 7 rows and 7 columns. Note that the relationship between distribution dispersion and the number of antenna elements may be determined arbitrarily, and is not limited to this example. Alternatively, the distribution dispersion may be classified simply based on the number of antenna elements having a predetermined amplitude or more without using the matrix of the antenna array.

FIG. 15 is a graph showing an example of respiration distribution dispersion. FIG. 15 shows the respiration distribution dispersion of the first body type and the second body type.

As shown in FIG. 15, the respiration distribution varies depending on the body type of the subject. Antenna element r with which the microwave signal due to respiration is 80% or more of the maximum amplitude is shown in FIG. It is distributed more than the first body type. This is because a person with the second body type has a wider chest than a person with the first body type. 14, the distribution variance of the first figure shown in FIG. 15(a)=1, and the distribution variance of the second figure shown in FIG. 15(b)=3.

(Step S812)
The classification determination unit 418 classifies biometric feature data into biometric patterns. FIG. 16 is a biometric pattern table showing an example of biometric pattern classification in the first embodiment. As shown in FIG. 16, the biometric pattern is classified from the biometric feature data described in step S811, that is, the combination of respiratory amplitude and distribution variance. For example, if the respiratory amplitude is 1.0 db and the distribution variance is 2, the biological pattern is biological pattern No. 5. Such a biological pattern table is preferably stored in the storage unit 22 in advance.

(Step S813)
Body type data acquisition unit 420 acquires body type data from, for example, PC 61 and stores it in storage unit 22 . FIG. 17 is a figure data table showing an example of figure data. The body type data, as shown in FIG. 17, is, for example, the body weight, body fat percentage, sex, etc. of the subject. Such body type data is stored in the PC 61 by measuring the person to be measured in advance using a weight and body fat scale. The body type data may be obtained from an external server other than the PC 61. Before measuring the cardiac output, the person to be measured is measured using a body fat scale or the like, and the measurement results are obtained. It may be input and stored in the storage unit 22 .

(Step S814)
A correction execution unit 419 obtains a correction value from a combination of the biometric pattern and body shape data. In the present embodiment, correction values determined in advance from a combination of biometric patterns and body shape data are stored in the storage unit 22 as a correction data table.

FIG. 18 is a correction data table showing an example of correction values determined from a combination of biometric pattern and body type data. In the correction data table shown in FIG. 18, the intensity coefficient of the correction value is a correction coefficient for correcting the constant β (described later) in equation (2) described later, and the amplitude coefficient corrects the amplitude h (described later). is a correction factor for

The correction execution unit 419 determines correction values by referring to the correction data table shown in FIG. Correction execution unit 419, for example, the classified biological pattern No. is "1", and the acquired body type No. is "1". is "A", the correction No. As for A1, the correction values are assumed to be an intensity coefficient of 1.2 and an amplitude coefficient of 0.8.

Then, the correction execution unit 419 corrects the estimation (calculation process) of the cardiac output by the cardiac output estimation unit 214 in step S21 described later.

As described above, the processing in the subroutine flowchart of FIG. 12 is completed, and the processing returns to that of FIG.

(Step S21)
Cardiac output estimator 214 estimates the cardiac output or the volume of blood pumped from the heart using the waveform data of antenna element r determined in step S19. At this time, correction is performed by the correction execution unit 419 . In the heartbeat waveform as shown in FIG. 5C, the difference between the signal intensity when the heart is in the systole and the diastole is defined as amplitude h, and the cardiac output of the heart 91 of the patient 90, or the beat from the heart Estimate the amount of blood drawn. The heart 91 experiences greater microwave losses and signal attenuation during diastole as compared to systole. That is, the intensity of the received signal during systole is smaller than the base intensity b, and the intensity of the received signal during diastole is larger than the base intensity b. The amplitude h is the difference between the top of the crest and the bottom of the trough of the waveform w1. The base intensity b is the average value of the electric field intensity of microwaves received by all the antenna elements r.

The amplitude h, which is the change in signal intensity, is proportional to the change in the size of the heart, that is, the stroke volume, so the cardiac output can be estimated (calculated) from the amplitude h. Specifically, for example, it is calculated by the following formula (1).

Cardiac output = amplitude h x constant α - constant β (1)
In the equation (1), the terms of constants α and β are constants for converting the value obtained from the electric field intensity of the received signal into the value of mL (or L) as the volume of blood pumped from the heart. Instead of such constants α and β, a calibration curve or the like for converting numerical values of cardiac output based on electric field intensity into numerical values of blood volume may be used.

In this embodiment, in the process of calculating the cardiac output, the constant β and the amplitude h are corrected by the correction values obtained in step S20. Therefore, the cardiac output for correction is calculated by the following equation (2).

Cardiac output = amplitude h x amplitude coefficient x constant α - constant β x intensity coefficient (2)
Cardiac output estimator 214 estimates the cardiac output using this equation (2).

The first embodiment described above has the following effects.

The cardiac output measurement sensor 1000 extracts the biometric characteristics of the subject from the waveform data of the signal received through the organism, classifies them as biometric patterns, and calculates correction values determined for each classification. We decided to correct the calculation process of cardiac output by

As a result, the present embodiment can estimate the cardiac output, which is the purpose of measurement, with high accuracy according to the individual differences of the person to be measured.

In addition, in the present embodiment, the accuracy of estimating the cardiac output can be further improved by using separately measured body shape data together with the classification of the biological pattern.

In addition, in the present embodiment, the variation (amplitude) of the reception intensity due to respiration is used to extract biometric feature data. The variation in received intensity due to respiration depends on the size of the body, thus improving the accuracy of bio-pattern classification.

In addition, in the present embodiment, measured values obtained by each antenna element are used at the same time or substantially at the same time, and waveform data is created from the obtained measured values. By using measured values measured at the same time or substantially at the same time in this way, accuracy is improved when extracting cardiac output feature data using secondary distribution data using evaluation values of any of indices 1 to 6. do.

Further, in this embodiment, the high-speed switching section 122 (or the high-speed switching section 112) is included, and the primary distribution creating section 211 includes a point data recording section 301 and a waveform data generating section 302. FIG. As a result, measurements can be performed with a plurality of antenna elements substantially at the same time, and the accuracy can be improved as described above.

In the case of using a difference time other than peak timing (evaluation value of index 6), measured values obtained at different times for each antenna element may be used. For example, the measurement of the received signal on the propagation path between one transmitting-side antenna element t and one receiving-side antenna element r is performed while sequentially switching at intervals of several seconds, and this is repeated for all the antenna elements r. You can also get the value.

Further, in this embodiment, microwaves are used as electromagnetic waves. Microwaves are attenuated less than other frequencies when they pass through the human body, and are more sensitive to signal changes (amplitude increase/decrease rate) associated with loss changes in response to heart expansion/contraction movements than other frequencies. It is also large and suitable for measuring cardiac output.

Note that, in the first embodiment, only the distribution variance may be used as biometric characteristic data without using respiratory amplitude data. When only the distribution variance is used, it is possible to discriminate differences in the spread of muscle and fat in the chest (particularly around the heart) in a living body. If the spread of muscle or fat is different, the easiness of passage of electromagnetic waves (difference in loss) will be different, so it is possible to classify biological patterns according to this. By performing correction based on the classified biological patterns, the estimation accuracy of the cardiac output can be improved.

Further, in the first embodiment, only the respiratory amplitude may be used as the biometric characteristic data without using the distribution dispersion data. Even if only the respiratory amplitude is used, it is possible to determine how easily the electromagnetic wave passes through the living body (difference in loss), so that the living body pattern can be classified. By performing correction based on the classified biological patterns, the estimation accuracy of the cardiac output can be improved. In this case, each of the transmitting antenna 11 and the receiving antenna 12 may be composed of one antenna element. When both the transmitting antenna 11 and the receiving antenna 12 are formed as one antenna element, it is desirable to place them so as to sandwich the heart, particularly the left ventricle, as much as possible. Also, in this case, the processing of steps S11 to S17 and S19 is unnecessary, and the waveform data for one antenna element is created and used.

(Modification of the first embodiment)
The correction due to differences in living organisms according to the first embodiment can also be applied to the waveform generation process of received microwave signals.

FIG. 19 is a graph for explaining a modification, and is a graph showing waveform data of a microwave signal received corresponding to one certain antenna element r.
FIG. 19A is a graph showing waveform data of a microwave signal received corresponding to one antenna element r, FIG. showing. Filtering here is a process of applying a smoothing filter to remove high frequency components. Specifically, the high frequency components in the graph shown in FIG. 19(a) are removed by a smoothing filter as shown in FIG. 19(b).

In this modified example, filter coefficients and electric field intensity correction coefficients used in such a smoothing filter are set for each classified biological pattern.

FIG. 20 is a correction data table showing examples of filter coefficients and electric field intensity correction coefficients as correction values in the modified example of the first embodiment.

In the correction data table shown in FIG. 20, the correction value is determined from the combination of the biometric pattern and body type data, as in the first embodiment. It should be noted that the classification of biometric patterns and body type data are as described in the first embodiment.

A filter coefficient serving as a correction value is a coefficient for removing high-frequency components, and an intensity coefficient is a correction coefficient used to equalize the signal intensity by increasing low signal intensity values.

The correction execution unit 419 determines correction values by referring to the correction data table shown in FIG. Correction execution unit 419, for example, the classified biological pattern No. is "1", and the acquired body type No. is "1". is "A", the correction No. As for A1, its correction value is set to a filter coefficient of 1.2 and an electric field intensity correction coefficient of 0.8.

Then, in step S21, the cardiac output estimator 214 estimates (calculates) the cardiac output using the waveform data smoothed by the smoothing filter corrected by the correction value.

(Second embodiment)
FIG. 21 is a block diagram showing the configuration of a cardiac output measurement sensor according to the second embodiment.

The second embodiment uses the reflection coefficient of the living body as the biological feature data. For this purpose, the cardiac output sensor 1000 of the second embodiment has a network analyzer 600 . The network analyzer 600 causes the transmitting antenna 11 to irradiate the living body with electromagnetic waves via the transmitting/receiving controller 14, causes the transmitting antenna 11 to function as a receiving antenna, and receives reflected waves from the living body. Then, the network analyzer 600 obtains the reflection coefficient, and the biometric feature data extraction unit 417 extracts the reflection coefficient as biometric feature data.

When there are a plurality of antenna elements t of the transmitting antenna 11 (see FIGS. 4A and 4B), any one antenna element t may be used.

Since other configurations are the same as those of the first embodiment, description thereof will be omitted. In addition, the second embodiment differs from the first embodiment in some functions of a biological characteristic data extraction unit 417, a classification determination unit 418, and a correction execution unit 419 in the control unit 21. FIG. Of the functions of these units, only the portions different from those of the first embodiment will be described here.

FIG. 22 is a subroutine flowchart showing the processing of step S20 of FIG. 6 in the second embodiment.

(Step S20)
Here, the biometric feature data extraction unit 417, the network analyzer 600, the classification determination unit 418, the correction execution unit 419, and the body shape data acquisition unit 420 cooperate to measure the reflection coefficient, obtain biometric feature data, and obtain biometric data. Classify the pattern and determine the correction value.

(Step S911)
First, the biometric feature data extraction unit 417 activates the network analyzer 600 to irradiate the biometric body with electromagnetic waves. The electromagnetic waves used may be the same microwaves used to estimate cardiac output. Thereby, the network analyzer 600 measures the reflection coefficient of the living body. A dedicated electromagnetic wave may be used for the measurement of the reflection coefficient. In that case, the biological characteristic data extracting unit 417 may directly access the transmitting antenna 11 from the network analyzer 600 without going through the transmitting/receiving controller 14 to transmit a dedicated electromagnetic wave. The dedicated electromagnetic waves may be microwaves or non-microwaves, but electromagnetic waves that have no or very little effect on the living body (that has cleared safety standards) are used.

The reflection coefficient is the ratio of the reflected wave to the incident wave, is called the S11 parameter, and is represented by the following equation (3). An incident wave is an electromagnetic wave irradiated toward a living body, and a reflected wave is a reflection from the living body.

Reflection coefficient (S11)=(field strength of reflected wave)/(field strength of incident wave) (3)
The reflection coefficient measured by the network analyzer 600 varies depending on the electrical constants of the contact surface, that is, the surface of the living body. When the electrical constant of the surface of the living body changes, the loss of microwaves passing through the living body also changes.

The reflection coefficient measured by the network analyzer 600 is extracted as biometric feature data by the biometric feature data extraction unit 417 .

FIG. 23 is a schematic diagram for explaining the tendency of the reflection coefficient with respect to a living body. People with the third body type in FIG. 23(a) have more muscles than people with the fourth body type in FIG. many).

The reflection coefficient (S11 parameter) for the living body tends to be higher for a person with a large amount of muscle, such as the third body type shown in FIG. 23(a), than a person with a large amount of fat.

Therefore, in the present embodiment, by measuring the reflection coefficient and using it as biological characteristic data, it is possible to distinguish between people with well-developed muscles and those with less muscles, even if they have similar body types (for example, the same chest circumference). be able to discern the difference in microwave loss between

(Step S912)
The classification determination unit 418 classifies the reflection coefficients (biological feature data) into biological patterns. FIG. 24 is a biometric pattern table showing an example of biometric pattern classification in the second embodiment. The biological patterns in the second embodiment are classified according to the reflection coefficients measured by the network analyzer 600, as shown in FIG.

(Step S913)
The figure data acquisition unit 420 is the same as in the first embodiment, and acquires figure data from, for example, the PC 61 and stores it in the storage unit 22 .

(Step S914)
A correction execution unit 419 obtains a correction value from a combination of the biometric pattern and body shape data. FIG. 25 is a correction data table showing examples of correction values determined from combinations of biometric patterns and body type data in the second embodiment. In the second embodiment, unlike the first embodiment, only amplitude coefficients are determined as correction values. Also in the second embodiment, as shown in FIG. 25, the correction value is determined in advance from the combination of the biometric pattern and body shape data. Such correction data table is stored in the storage unit 22 . The correction execution unit 419 refers to this correction data table to determine correction values.

Then, the correction execution unit 419 corrects the estimation (calculation process) of the cardiac output by the cardiac output estimation unit 214 in step S21 described later.

As described above, the processing in the subroutine flowchart of FIG. 22 is completed, and the processing returns to that of FIG.

(Step S21)
Cardiac output estimator 214 uses the waveform data of antenna element r determined in step S19 to estimate the cardiac output or the volume of blood pumped from the heart, as in the first embodiment. do. At this time, correction is performed by the correction execution unit 419 . The correction here is for the amplitude h. Therefore, the cardiac output for correction is calculated by the following equation (4).

Cardiac output = amplitude h x amplitude coefficient x constant α - constant β (4)
The cardiac output estimation unit 214 estimates the cardiac output using this equation (4). It should be noted that the constants α and β in the equation (4) are the same as those in the equation (1).

The second embodiment described above has the following effects in addition to the effects of the first embodiment.

In the present embodiment, since the reflection coefficient is measured as the biometric characteristic data, it is possible to distinguish the difference in electromagnetic wave loss due to the difference in the amount of muscle and fat in the living body. Therefore, in the present embodiment, even if the body shape is the same in appearance, the cardiac output can be accurately estimated even when the amount of electromagnetic wave loss is actually different. As a result, the present embodiment can estimate the cardiac output, which is the purpose of measurement, with high accuracy according to the individual differences of the person to be measured.

In addition, in the second embodiment, each of the transmitting antenna 11 and the receiving antenna 12 may be composed of one antenna element. This is because, unlike the first embodiment, when the reflection coefficient is used as biometric feature data, its distribution dispersion is not used. For this reason, if it is only necessary to measure the reflection coefficient, it suffices to irradiate the living body with an electromagnetic wave at one point and receive its reflection. When both the transmitting antenna 11 and the receiving antenna 12 are one antenna element, the transmitting antenna 11 and the receiving antenna 12 are installed so as to sandwich the heart, especially the left ventricle, as much as possible when measuring the cardiac output. It is desirable to Also, in this case, the processing of steps S11 to S17 and S19 is unnecessary, and the waveform data for one antenna element is created and used.

Further, in the second embodiment, the network analyzer 600 is incorporated in the cardiac output measurement sensor 1000 and controlled by the controller 21 to obtain the reflection coefficient. However, in the second embodiment, the network analyzer 600 alone is used to determine the reflection coefficient in advance, and then the cardiac output is estimated by the cardiac output measurement sensor according to the first embodiment. good too. In that case, the value of the reflection coefficient measured using the network analyzer 600 alone is input to the cardiac output measurement sensor and used as biological characteristic data. Biometric pattern classification and correction are performed by the cardiac output sensor. Further, the classification and correction of the biometric pattern may be performed separately by a computer (PC) or the like, and the correction value may be provided to the cardiac output measurement sensor to estimate the cardiac output.

The embodiments described above are not limited to the configurations described above, and various modifications can be made within the scope of the claims.

In each of the above-described embodiments, the body shape data is acquired and used together with the biological pattern classification. Accuracy can be improved. If the body type data is not used, the body type data acquisition unit 420 may be omitted. Moreover, steps S813 and S913 are unnecessary.

As for the correction value, both the intensity coefficient and the amplitude coefficient are used in the first embodiment, but only one of them may be used as the correction value. That is, the correction value may use only the intensity coefficient or only the amplitude coefficient. The same applies to the modified examples, and only the filter coefficients or only the electric field strength correction coefficients may be used. Further, in the second embodiment, not only the amplitude correction by the amplitude coefficient, but also the signal strength correction (strength coefficient) is used from the difference in the reception intensity of the transmitted microwave due to the difference in the reflection coefficient. good.

Moreover, the means and methods for performing various processes in the cardiac output measurement sensor 1000 described above can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided, for example, by a computer-readable recording medium such as a USB memory or DVD-ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. Moreover, the above program may be provided as independent application software, or may be incorporated into the software of the apparatus as one function.

REFERENCE SIGNS LIST 1000 cardiac output measurement sensors 11, 11b transmission antenna unit 110 substrate 111 transmission waveform generator 112 high-speed switching unit 113 antenna array (transmission side)
t1 to tx antenna element (transmitting side)
12, 12b receiving antenna unit 120 substrate 121 antenna array (receiving side)
122 high-speed switching unit 123 sampling unit 13 signal cable 14 transmission/reception controller 20 device body 21 control unit 211 primary distribution creating unit 301 point data recording unit 302 waveform data creating unit 212 secondary distribution creating unit 213 element determining unit 214 cardiac output Estimation unit 215 Installation state determination unit 216 Instruction unit 217 Biological feature data extraction unit 218 Classification determination unit 219 Correction execution unit 600 Network analyzer 22 Storage unit 23 Input/output I/F
24 Communication I/F
51 touch panel 52 XY stage 61 PC

Claims (15)

a transmitting antenna for transmitting electromagnetic waves toward a living body;
a receiving antenna arranged to face the transmitting antenna with the heart of the living body interposed therebetween;
a waveform data creation unit that creates waveform data representing changes over time in signal strength of the electromagnetic wave received by the receiving antenna;
a cardiac output estimation unit that estimates a cardiac output from the waveform data;
a biometric feature data extracting unit for extracting biometric feature data representing features of the living body from a signal obtained by receiving the electromagnetic waves transmitted toward the living body;
a classification determination unit that classifies the biometric features into biometric patterns from the biometric feature data;
a correction execution unit that executes correction based on the classified biometric pattern in the calculation process of the cardiac output estimation by the cardiac output estimation unit;
A cardiac output sensor, comprising: The biometric feature data extracting unit extracts at least one of a variation in signal intensity of the electromagnetic wave transmitted through the living body and a reflection coefficient obtained from the electromagnetic wave reflected from the living body as the biometric feature data. The cardiac output measurement sensor according to claim 1, wherein 3. The cardiac output according to claim 1 or 2, wherein in the calculation process, the correction execution unit corrects signal intensity derived from changes in the cardiac output obtained from the waveform data based on the biometric pattern. volume measurement sensor. at least one of the transmitting antenna and the receiving antenna includes a plurality of antenna elements having different positions with respect to the living body;
The cardiac output measurement sensor according to any one of claims 1 to 3, wherein the waveform data creation unit creates the waveform data for each of the antenna elements. 5. The cardiac output measurement sensor according to claim 4, wherein said biometric characteristic data extraction unit extracts a difference in variation in signal intensity for each of said antenna elements as said biometric characteristic data. a high-speed switching unit that sequentially switches ON/OFF of each of the plurality of antenna elements at a predetermined cycle;
6. The waveform data creation unit according to claim 4, wherein the waveform data creating unit creates the waveform data corresponding to each of the antenna elements turned on by the high-speed switching unit from the signal strength of the electromagnetic wave received by the receiving antenna. cardiac output sensor. 7. The cardiac output measurement sensor according to claim 6, wherein, in said predetermined cycle, one cycle time for turning on the plurality of said antenna elements is shorter than a cardiac cycle. The cardiac output measurement sensor according to any one of claims 4 to 7, wherein the plurality of antenna elements are antenna arrays arranged in a grid pattern on the same plane. a body type data acquisition unit that acquires body type data measured for each living body;
a storage unit that stores a correction data table in which correction values are determined in advance based on the correspondence relationship between the body shape data and the biological feature data;
The cardiac output measurement sensor according to any one of claims 1 to 8, wherein the correction execution unit uses the correction data table to correct the calculation process. a transmitting antenna for transmitting electromagnetic waves toward a living body;
a receiving antenna arranged to face the transmitting antenna with the heart of the living body interposed therebetween;
A control program executed by a computer for controlling a cardiac output measurement sensor for estimating cardiac output using the electromagnetic wave received by the receiving antenna and transmitted through the living body,
step (a) of creating waveform data representing changes over time in signal strength of the electromagnetic wave received by the receiving antenna;
a step (b) of extracting biometric feature data representing features of the living body from a signal obtained by receiving the electromagnetic waves transmitted toward the living body;
a step (c) of classifying the biometric features into biometric patterns from the biometric feature data;
In the step of estimating the cardiac output using the waveform data, the cardiac output is corrected based on the classified biological pattern in a calculation process for estimating the cardiac output. estimating (d)
A control program. In the step (b), at least one of a variation in signal intensity of the electromagnetic wave transmitted through the living body and a reflection coefficient obtained from the electromagnetic wave reflected from the living body is extracted as the biological feature data. 11. The control program according to claim 10. 12. The control program according to claim 10 or 11, wherein in said step (d), in said calculation process, signal intensity derived from changes in said cardiac output obtained from said waveform data is corrected based on said biological pattern. . at least one of the transmitting antenna and the receiving antenna includes a plurality of antenna elements having different positions with respect to the living body;
The control program according to any one of claims 10 to 12, wherein said step (a) creates said waveform data for each said antenna element. 14. The control program according to claim 13, wherein said step (b) extracts, as said biometric characteristic data, differences in the amount of change in reception intensity for each of said antenna elements. further comprising a step (e) of acquiring body shape data measured for each living body prior to the step (d);
a correction data table in which correction values are determined in advance from the corresponding relationship between the body shape data and the biological characteristic data is stored in the computer;
15. The control program according to any one of claims 10 to 14, wherein said step (d) uses said correction data table to correct said calculation process.

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