WO2022209283A1 - Cardiac output measurement sensor and control program - Google Patents

Abstract

The present invention highly accurately estimates the amount of blood output from the heart using transmission/reception antennas disposed at appropriate positions.　A cardiac output measurement sensor 1000 is provided with a transmission antenna 11, a reception antenna 12, and a cardiac output estimation unit 214 which estimates the amount of blood output from the heart. At least one of the transmission antenna 11 and the reception antenna 12 includes a plurality of antenna elements r which differ in position relative to a living body, and is further provided with: a primary distribution generation unit 211 which generates waveform data indicating a change over time in measured value for each of the antenna elements r and generates waveform distribution data in which the waveform data is associated with each of the antenna elements r; and an element determination unit 213 which determines an antenna element to be used for estimating the amount of blood from among the plurality of antenna elements on the basis of the waveform distribution data.

Description

Cardiac output sensor and control program

The present invention relates to a cardiac output measurement sensor and a control program.

As a conventional technology related to cardiac output detection, Patent Document 1 discloses a device that includes a transmitting antenna, a receiving antenna, and an estimating unit. In this device, the transmitting antenna transmits radio waves such as microwaves to the patient's chest, the receiving antenna receives the radio waves transmitted from the transmitting antenna, and the estimating unit measures the phase or amplitude intensity of the radio waves received by the receiving antenna. Based on this, the cardiac output of the person to be measured is detected (see Patent Document 1).

WO2018/194093

However, depending on the position of the pair of transmitting/receiving antennas for transmitting/receiving radio waves with respect to the living body, especially the positional relationship of the transmitting/receiving antennas with respect to the heart, the received waves obtained by the receiving antennas may not be suitable for measuring cardiac output. If the transmitter/receiver antenna is misaligned with respect to the heart and used in a state unsuitable for measuring cardiac output, the resulting measurement accuracy of the cardiac output decreases.

In addition, when using the change in cardiac output for each measurement in clinical practice, if there is no technology to position the transmitting and receiving antennas in a location suitable for measurement, the obtained change in cardiac output may not be the same as the antenna installation position. It is not possible to determine whether this is due to a change in the patient's condition or a change in the patient's condition.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. The purpose is to provide a control program.

In order to achieve the above object, the cardiac output measurement sensor of the present invention comprises a transmitting antenna for transmitting electromagnetic waves toward a living body, and a receiving antenna arranged to face the transmitting antenna with the heart of the living body interposed therebetween. an antenna; and a cardiac output estimator for estimating the volume of blood pumped from the heart using the electromagnetic wave received by the receiving antenna and transmitted through the living body, wherein At least one of the antenna elements includes a plurality of antenna elements positioned at different positions with respect to the living body, and further creates waveform data representing temporal changes in measured values measured for each of the antenna elements, and transmits the waveform data to each of the antenna elements. and a primary distribution creating unit that creates waveform distribution data associated with the blood volume estimation unit from among the plurality of antenna elements based on the waveform distribution data obtained by the primary distribution creating unit. and an element determination unit that determines an antenna element to be used.

Further, in order to achieve the above object, the control program of the present invention includes a transmitting antenna for transmitting electromagnetic waves toward a living body, and a receiving antenna arranged to face the transmitting antenna with the heart of the living body interposed therebetween. and a cardiac output estimator for estimating a cardiac output using an electromagnetic wave received by the receiving antenna and transmitted through the living body, wherein at least one of the transmitting antenna and the receiving antenna is connected to the living body. A computer-executable control program for controlling a cardiac output sensor comprising a plurality of antenna elements positioned differently with respect to
a primary distribution creating step of creating waveform data representing temporal changes in measured values measured for each of the antenna elements, and creating waveform distribution data in which the waveform data is associated with each of the antenna elements; and an element determination step of determining an antenna element to be used for estimating the blood volume from among the plurality of antenna elements from the waveform distribution data created in the next distribution creation step. let it run.

According to the cardiac output measurement sensor and control program according to the present invention, the amount of blood pumped from the heart can be estimated with high accuracy using the transmitting/receiving antennas placed at appropriate positions.

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; 4 is a flow chart showing antenna element determination processing and cardiac output measurement processing in the first embodiment. 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. 4 is a schematic diagram showing an example of evaluation value distribution data (secondary distribution data); 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. 7 is a subroutine flowchart showing the process of step S19 in FIG. 6 in the second embodiment; FIG. FIG. 12B is a flow chart showing the process following FIG. 12A; FIG. 4 is a table showing examples of various feature amounts; The peak position as feature data is superimposed on the secondary distribution data. 3 is a perspective view showing the configuration of an XY stage; FIG. FIG. 4 is a side view showing the configuration of the XY stage; FIG. 12B is a flow chart showing the process following FIG. 12A in the modified example; FIG. 10 is a flow chart showing antenna element determination processing and cardiac output measurement processing in the third embodiment.

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. Cardiac output usually refers to the amount of blood pumped from the heart per minute, but in this specification, the amount of blood pumped from the heart is referred to as cardiac output. Sometimes.

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 measuring sensor 1000 according to the first embodiment, and FIG. 3 is a diagram showing a configuration example of the transmitting/receiving antenna in the first embodiment.

FIG. 1 shows a state in which a patient 90 (also called 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 medication 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, receiving antenna 12 is positioned below patient 90 and transmitting 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. For example, the patient 90 may be turned upside down so that the transmitting antenna 11 is arranged below the patient 90 (back side) and the receiving antenna 12 is arranged above the patient 90 (front side).

As shown in FIG. 2, the cardiac output measurement sensor 1000 includes a transmitting antenna 11, a receiving antenna 12, and a device 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 functions as 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, and an instruction unit 216. Function. 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 the evaluation values and creates distribution data of the evaluation values according to the positions of the antenna elements. The element determination unit 213 is used in estimating the cardiac output based on the distribution data of the evaluation values created by the secondary distribution creation unit 212 based on the waveform distribution data created by the primary distribution creation unit. Determine antenna elements. That is, the element determining unit 213 indirectly determines the cardiac output based on the waveform distribution data created by the primary distribution creating unit 211 based on the evaluation value distribution data created by the secondary distribution creating unit 212 . It determines the antenna elements to be used when estimating the quantity. 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 secondary distribution generator 212 functions as an evaluation value calculator, and calculates evaluation values (evaluation values 1 to 6 described later) from waveform data or waveform distribution data. 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. Details of these functions will be described later (FIG. 12B, etc., to 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, and a magnetic memory such as a hard disk. The storage unit 22 also stores point data, waveform data, waveform distribution data, comparative distribution patterns, set ranges of feature data, and the like. The storage unit 22 stores position information of antenna elements (antenna elements rx and tx, which will be described later) in the antenna array. The positional information is, for example, XY coordinates on the substrate and information on relative positional relationships (distance, direction).

(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 configuration of 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 or radio waves that pass through the 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.

The 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.

The 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)), which are arranged on the surface of the planar substrate 120. , are arranged in a grid on the same plane. 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 type 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. For example, it has a rectangular shape with one side of 100 to 150 mm.

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 .

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 the high-speed switching unit 122, only one switching element s (for example, element s1 (see FIG. 2)) is turned ON, and all the 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, and there is a possibility that a desired measurement value cannot be obtained. 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).

In addition, the high-speed switching unit 122 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 unit 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 apparatus 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.

Also, 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-side antenna array 113 may be several or may be 100 or more, and the number of antenna elements r in the receiving-side antenna array 121 may be several or 100. You can do more than that. 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.

Comparing the configuration in which the reception antenna side is an antenna array in FIG. 3 and the configuration in which the transmission antenna side is an antenna array in FIG. 4B, the configuration in which the reception antenna side is an antenna array is better in the configuration where the transmission antenna side is an antenna array. The inventor's study has revealed that the antenna element suitable for measuring cardiac output can be selected more accurately than the configuration.

(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. .

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 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 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 according to the setting of the cyclic mode and the 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. In addition, one cycle time tc can be set to an arbitrary 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 period/one cycle time may be performed by the user, or may be performed automatically by the control unit 21 side.

When automatically performed by the control unit 21, from the viewpoint of shortening the scanning time and reducing the required memory capacity, for example, the change is made in multiple stages. 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 surrounding antenna elements are 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, twice) 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 received signal corresponding to the electric field intensity 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 in 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. In FIG. 5C, the waveform data w1 when using the element r1 is shown as a representative. This waveform data is composed of a large number of point data p11, p21, p23, etc. linked to the element r1.

(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 cycle ts is several tens of microseconds.

(Antenna element determination processing and cardiac output measurement processing)
FIG. 6 is a flowchart showing antenna element determination processing and cardiac output measurement processing.

(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 (several hundred 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. The number of antenna elements r to be determined may be one or a plurality (for example, four). 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. Waveform distribution data is obtained by arranging waveform data associated 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. FIG. 10 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. As the index of the evaluation value calculated by the secondary distribution generating unit 212, any one of the evaluation values 1 to 6 may be used as shown in the figure, or a combination thereof may be used.

(1) "Amplitude of waveform data" with an evaluation value of 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 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 band-pass filter is applied to exclude frequencies outside the frequency (0.5 to 3 Hz) corresponding to the normal cardiac cycle range (30 to 180 beats/minute). processing may be performed. The positional relationship between the antenna elements and the heart can be estimated from the amplitude of the waveform data. In addition, such band-pass filtering may be pre-processed so as to acquire frequencies outside the range of the cardiac cycle, for example, components in the frequency band of respiratory fluctuations, thereby estimating the position of the antenna element r. be.

(2) Evaluation value 2 "Intensity at a specific frequency after Fourier transform" is obtained by performing FFT processing on the waveform data and obtaining a specific frequency ( 0.5 to 10 Hz) is obtained as evaluation value 2. The positional relationship with the heart can be estimated from the intensity distribution at specific frequencies. In addition, the evaluation value 2 may use the intensity in a frequency band other than the range of the cardiac cycle, for example, the frequency band of respiratory fluctuations, for estimating the positional relationship.

(3) Evaluation value 3 is "inflection point time of waveform data". The inflection point time can be calculated by second-order differentiating the waveform data. This evaluation value 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 this evaluation value 3.

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

(5) Evaluation value 5 is an "autocorrelation coefficient" and can be calculated from waveform data including multiple waveforms. The autocorrelation coefficient is an index 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) Evaluation value 6 is the "difference time between peak timings". The secondary distribution generating unit 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 waveform data of any predetermined antenna element r. For example, it is waveform data of an antenna element r (for example, antenna element r25) near the center of the antenna array 122 . The peak timing tends to differ depending on the positional relationship between the antenna element and the heart. The reason for this is that the time variation of the blood flow pumped from the heart differs depending on the location, and it is thought that there is a difference in the time to catch the peak timing depending on the positional relationship between the heart and the antenna element. The details of the evaluation value 6 will be described later.

The secondary distribution creating unit 212 creates secondary distribution data from at least one of the evaluation values 1 to 6. 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. In the example shown in FIG. 10, 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 having a better positional relationship with the heart 91 (especially the left ventricle) has a higher evaluation value.

(Step S513)
The element determination unit 213 determines antenna elements to be used for estimating the cardiac output from the quadratic distribution created in step S512. 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. 10(a). In the example of FIG. 10(b), since there are a plurality of antenna elements r having the same evaluation value (antenna elements r18-20, r25-27), the element determination unit 213 selects , may be determined to one antenna element r by a predetermined algorithm set in advance. For example, predetermined algorithms include selecting the center element (position C5) and selecting the upper right element (position C4). Alternatively, secondary distribution data may be newly created using another evaluation value, and the antenna element r may be narrowed down to one antenna element r from among the plurality of elements based on this new secondary distribution data.

As shown in FIGS. 10(a) and 10(b), the level of the evaluation value is highest at a certain position (for example, position E4 in FIG. 10(a)), and the evaluation value changes as the distance from that position increases. characterize. 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 . Further, as another example, the element determination unit 213, from the evaluation values (for example, evaluation values 1 to 5) calculated by the secondary distribution generation unit 212 (without going through the generation of the secondary distribution data) , to determine the antenna element r for measuring cardiac output. As described above, the processing in the subroutine flowchart of FIG. 7 is completed, and the processing returns to that of FIG.

(Step S20)
The cardiac output estimation unit 214 extracts the waveform data acquired using the antenna element r determined in step S19 from the waveform data related to the elements r1 to rx generated in step S18, and extracts the extracted antenna element r Estimates cardiac output, or the volume of blood pumped from the heart, based on the waveform data for . Specifically, in the waveform data shown in FIG. 5C, the cardiac output of the heart 91 of the patient 90 or the heart Estimate the volume of blood pumped from Heart 91 experiences greater loss and greater signal attenuation in diastole than in systole. That is, the strength of the received signal is smaller during diastole than during systole. Since the change in signal intensity is proportional to the change in heart size, that is, the stroke volume, the cardiac output can be estimated (calculated) from the change in signal intensity, that is, the amplitude of the waveform corresponding to the heartbeat. In addition to the cardiac output, the stroke volume calculated from the amplitude intensity of one waveform may be displayed. In addition to the cardiac output, the heartbeat frequency may also be displayed as the heart rate. Furthermore, the body surface area may be calculated from information such as the height and weight of the subject that has been input, and the cardiac coefficient may be displayed by dividing the cardiac output by the body surface area.

(Evaluation value 6 (difference time of peak timing))
Here, the evaluation value 6 briefly mentioned above will be described in more detail with reference to FIGS. 11A and 11B. FIG. 11A is a schematic diagram for explaining the differential time between peak timings. FIG. 11B is a schematic diagram showing the difference in differential time depending on the position. FIG. 11A 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 transmission 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. 11B shows changes in differential time of waveform data when measuring while displacing the position of a certain antenna element r in the X direction. In the experiment of FIG. 11B, unlike the embodiment, an electrocardiogram waveform is used as a reference waveform when calculating the differential time. As shown in FIG. 11B, 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, due to the difference in the relative position of the antenna element r with respect to the heart 91, that is, due to the position of the heart 91 in the radio wave propagation path between the antenna element t of the receiving antenna 12 and the antenna element r ( especially the left ventricle), with different peak delay times. That is, for the evaluation value 6, the secondary distribution generator 212 calculates the positional relationship between the heart position and each antenna element r using the differential time distribution. Then, the element determination unit 213 selects, from the plurality of antenna elements r, the antenna element r whose evaluation value is most suitable for calculating the cardiac output.

As described above, the cardiac output measurement sensor 1000 according to the present embodiment uses the transmitting antenna 11, the receiving antenna 12, and the microwaves received by the receiving antenna 12 and transmitted through the living body to measure the cardiac output of the heart. a cardiac output estimating unit 214 for estimating the blood volume to be applied, at least one of the transmitting antenna 11 and the receiving antenna 12 includes a plurality of antenna elements r located at different positions with respect to the living body, and A primary distribution creation unit 211 that creates waveform data representing changes over time in measured values measured with respect to and creates waveform distribution data in which the waveform data is associated with each antenna element r, and a primary distribution creation unit and an element determination unit 213 that determines, from among a plurality of antenna elements r, an antenna element r to be used in estimating the cardiac output, based on the waveform data created by 211 . By configuring in this way, it is possible to perform measurement using the optimum antenna element, and thus to estimate the volume of blood pumped from the heart with relatively high accuracy.

(Second embodiment)
A second embodiment will now be described with reference to FIGS. 12A to 15B. In the second embodiment, the propriety of the installation state of the antenna 12 is determined using the feature data before determining the antenna element r. 12A and 12B are subroutine flowcharts showing the process of step S19 of FIG. 6 in the second embodiment. In addition, in the second embodiment, the main routine flowchart is the same as that in the first embodiment shown in FIG. 6, and the description thereof is omitted.

(Steps S531, S532)
Here, the control unit 21 performs the same processing as steps S511 and S512 in FIG. Specifically, the primary distribution creating unit 211 of the control unit 21 creates waveform distribution data (primary distribution data), and the secondary distribution creating unit 212 creates evaluation value distribution data (secondary distribution data). do.

(Step S533)
The installation state determination unit 215 extracts feature data from primary or secondary distribution data (waveform distribution data or evaluation value distribution data) and determines the installation state of the antenna. FIG. 13 is a table showing examples of various feature amounts.

(1) "Amplitude of waveform data" of feature amount 1 is the amplitude of one or more waveforms 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 feature quantity 1. This feature quantity 1 can be obtained by a method similar to that for the evaluation value 1 described above. Then, the installation state determination unit 215 compares this feature value 1 with the setting range for the feature value 1 stored in the storage unit 22. If the setting range is within the setting range, the installation state is proper. is judged to be inappropriate. For example, if the positional relationship with the heart 91 is not correct and the amplitude is smaller than a predetermined range, it is determined to be inappropriate.

(2) Feature quantity 2 is an "autocorrelation coefficient" and can be calculated from waveform data containing multiple waveforms. This feature quantity 2 can be obtained by the same method as the evaluation value 5 described above. Then, the installation state determination unit 215 compares this feature value 2 with the setting range for the feature value 2 stored in the storage unit 22. If the setting range is within the setting range, the installation state is proper. is judged to be inappropriate. For example, if the waveform is not stable and the autocorrelation coefficient is smaller than a predetermined range, it is determined to be inappropriate.

(3) The feature amount 3 is "difference time between peak timings". The installation state determination unit 215 calculates the difference time by comparing the peak timing of the waveform of the target antenna element r with the reference waveform. This feature quantity 3 can be obtained by the same method as the evaluation value 6 described above. Then, the installation state determination unit 215 compares this feature value 3 with the setting range for the feature value 3 stored in the storage unit 22. If the setting range is within the setting range, the installation state is proper. is judged to be inappropriate. For example, when the difference time is larger than a predetermined range due to the influence of reflected waves, etc., it is determined to be inappropriate.

(4) The feature quantity 4 is the "waveform shape". The installation state determination unit 215 compares the waveform with the normal waveform shape stored in the storage unit 22, and determines that the installation state is inappropriate if the waveform differs from the normal waveform shape due to the inclusion of noise. do. Anything other than this is judged to be appropriate.

(5) The feature value 5 is the "peak position". A peak position is identified from the secondary distribution data. Any one of evaluation values 1 to 6 may be used to create the secondary distribution data. If the identified peak position is at any position of the antenna element r and is determined to be within the range, or if the peak position is not present at any of the antenna elements r and is outside the range (outside) may be judged. For example, the outermost antenna element r is in the process of increasing, and it is estimated that there is a peak further outside. The installation state determination unit 215 determines that the installation state is proper when within the range, and improper when outside the range. Also, if a plurality of peak positions are detected by receiving not only the direct wave but also the reflected wave, etc., it is determined that the installation state is inappropriate as an abnormality. FIG. 14 is a schematic diagram showing feature data in such a case. FIG. 14 shows peak positions as feature data superimposed on the secondary distribution data. In this figure, two peaks 1 and 2 appear and the installation state is inappropriate.

It should be noted that a comparative distribution pattern may be used to determine whether the installation state is appropriate or not based on the feature amount. For example, the feature data immediately before (for example, the previous day) measured on the same bed 95 for each patient 90 is stored as a comparison distribution pattern in the storage unit 22, and the similarity between the read comparison distribution pattern and the current feature data is determined. It is determined that the installation state is appropriate based on the nature of the installation. For example, if the patterns are substantially the same, it is determined that the installation state is appropriate.

(Step S534)
If the determination in step S533 is appropriate (YES), the installation state determination unit 215 proceeds to step S535, and if the determination is inappropriate (NO), the process proceeds to step S541 in FIG. 12B.

(Step S535)
This process is similar to step S513. The element determination unit 213 determines antenna elements r to be used for estimating the cardiac output from the quadratic distribution created in step S532. Then, the processing in the subroutine flowchart of FIG. 12A is ended, the processing returns to FIG. 6, and thereafter the cardiac output is measured using the determined antenna element r.

(Step S541)
If the peak position is outside the range (outside the antenna array 122), the control unit 21 advances the process to step S542. On the other hand, if, for example, feature quantities 1 to 4 are outside the set range, or if there are multiple peaks in feature quantity 5 (eg, FIG. 14), the process proceeds to step S550.

(Step S542)
The instruction unit 216 functioning as a second instruction unit determines the movement direction of the entire antenna 12 based on the feature data.

(Step S543)
The instruction unit 216 instructs the moving direction of the antenna 12 . Specifically, the movement direction is displayed on the touch panel 51 to prompt the user such as a nurse or doctor to move the antenna 12 . Alternatively, it outputs a movement signal to the XY stage 52 described below. When instructing the direction of movement, the amount of movement may also be displayed at the same time, or may be included in the movement signal.

15A and 15B are diagrams showing the configuration of the XY stage 52. FIG. Cardiac output measurement sensor 1000 may be configured to be movable in the XY directions by XY stage 52 as shown in these figures. 15A and 15B, the transmitting antenna 11 and the receiving antenna 12 are arranged above and below the bed 95 on which the patient 90 lies.

The XY stage 52 holds a controller 520, a holding section 521 that holds the upper transmitting antenna 11 inside the housing, a moving section 522 that moves the holding section 521 in the XY directions, and a lower receiving antenna 12 inside the housing. It is composed of a holding portion 523, a moving portion 524 that moves the holding portion 523 in the XY directions, and a vertical moving portion 525 that moves these members in the vertical direction.

The moving parts 522, 524 have similar configurations and include connecting parts that connect with rails, driving parts, and holding parts, respectively. The XY stage 52 can move the height (Z direction) and the position in the XY directions of the transmitting antenna 11 and the receiving antenna 12 respectively held by the holding units 521 and 523 according to the control signal of the instruction unit 216. .

In this embodiment, the XY stage 52 moves the receiving antenna 12 having a plurality of antenna elements r by a predetermined amount in the XY directions according to the movement signal sent from the instruction unit 216 .

(Step S544)
The controller 520 of the XY stage 52 moves the transmitting antenna 11 according to the instruction from the instruction section 216 and then returns a movement completion signal to the instruction section 216 . Alternatively, a remeasurement start instruction from the user is received via the touch panel 51 or the like. The instructing unit 216 functioning as the first instructing unit having received this command sends a re-measurement instruction to the control unit 21 . After that, the process returns to step S11 in FIG. 6, the subsequent processes are executed again, and the measurement is performed again.

(Step S551)
Here, the instruction unit 216 functioning as the first instruction unit instructs remeasurement or rearrangement. Specifically, the instruction unit 216 instructs the control unit 21 to perform re-measurement, returns to the process of step S11, and performs re-measurement while maintaining the current arrangement state. Alternatively, the touch panel 51 is caused to display an instruction prompting confirmation of the arrangement state. Then, after receiving a re-measurement start instruction from the user via the touch panel 51 or the like, the process returns to step S11 and re-measurement is performed. It should be noted that when re-measuring, the circulation mode may be changed and/or the period ts may be changed.

As described above, the cardiac output measurement sensor 1000 according to the second embodiment includes the installation state determination unit 215 in addition to the configuration of the first embodiment. 122 is determined to be appropriate. By doing so, if the installation state is improper, by performing re-installation or re-measurement, it is possible to prevent the determination of the antenna element to be used under the improper installation state. can be prevented and the volume of blood pumped from the heart can be estimated with higher accuracy.

(Modification)
In the second embodiment, when the feature data is out of the set range, re-measurement is instructed, but processing may be performed as in the modified example described below. FIG. 16 is a flow chart showing processing following FIG. 12A in the modification.

In the example shown in FIG. 16, steps S541 to S544 and step S551 are the same as the process shown in FIG. 12A, and description thereof is omitted.

(Step S550)
Here, if the feature amounts 1 to 4 are outside the set range (YES), the installation state determination unit 215 advances the process to step S555. On the other hand, if it is not out of the set range (NO), that is, if a plurality of peaks exist in feature quantity 5, the process proceeds to step S551, and re-measurement is instructed in step S551.

(Step S555)
The installation state determination unit 215 excludes the antenna element r outside the set range from the targets.

(Step S556)
Here, the element determination unit 213 determines the antenna element r from among the antenna elements other than the antenna elements excluded in step S555. For example, the antenna element r outside the set range in the characteristic quantity 4 (waveform shape) is excluded. As a result, even if the evaluation value 1 (amplitude) is the highest, this excluded antenna element r is not selected as the antenna element used for estimating the cardiac output. After that, the processing in the subroutine flowchart of FIG. 16 is terminated, the processing returns to that of FIG. 6, and thereafter the cardiac output is measured using the determined antenna element r.

In this way, in the modified example, the antenna elements r whose characteristic data are out of the set range are excluded from the selection targets, and the antenna elements r to be used for cardiac output measurement are determined from among the other antenna elements r. As a result, inappropriate antenna elements can be prevented from being selected, and the volume of blood pumped from the heart can be estimated with higher accuracy.

(Other modifications)
As another modification, the element determination unit 213 may select one or a plurality of antenna elements r based on feature data. For example, a plurality of antenna elements r are selected based on feature data obtained from secondary distribution data as shown in FIG. 10(b). For example, a plurality of antenna elements r close to the peak position are selected as feature data. Then, the cardiac output estimating unit 214 averages the signal (digital signal) obtained from the measured value of the selected antenna element r, or weights the signal according to the distance from the peak position. Cardiac output is estimated using the processed signal, such as an average (weighted average). By doing so, the volume of blood pumped from the heart can be estimated with higher accuracy.

(Third embodiment)
In the third embodiment, the patient 90 changes the state such as the body position based on instructions from a user such as a nurse or a doctor. Then, element scanning processing is performed in a plurality of different states of the patient 90, and the installation state is determined based on feature data extracted from the measurement results.

FIG. 17 is a flowchart showing antenna element determination processing and cardiac output measurement processing in the third embodiment. Steps S11 to S20 in FIG. 17 are the same processes as steps S11 to S20 in FIG. 6 described above, and description thereof will be omitted.

(Step S11)
The control unit 21 starts transmission/reception by the transmission/reception antenna in response to the user's instruction to start measurement.

(Step S115)
In step S115, the control unit 21 performs loop b processing between step S176 and step S176. In this loop b, the state of the patient 90 (living body) is changed. This state includes at least one or more of a stationary state, a deep breathing state, a body motion state, and a posture change state. Here, the stationary state and the deep breathing state literally mean that the patient 90 in the lying position (supine position) on the bed 95 remains motionless as much as possible or maintains a state of breathing deeply. A repositioning state is a repositioning between supine, lateral and prone positions. The state of body movement is a movement that does not accompany a change in body position, such as bending and stretching the arms and legs. Both states are performed for a predetermined period of time specified by the user or longer. Here, the predetermined period is about the period of one unit of element scanning processing (for example, several seconds to ten and several seconds).

(Steps S12 to S17 (loop a and element scanning process))
In this step S12, the control unit 21 performs the processing of loop a between step S16 and repeats the processing of this loop a until the termination condition is satisfied in step S17. If the termination condition is satisfied, the process proceeds to step S175.

(Step S175)
The control unit 21 displays on the touch panel 51 or the like that the element scanning process for one unit has been completed. At this time, the next state (for example, deep breathing state) may also be displayed. In response to the display, the user instructs the patient 90 to move from the resting state to the deep breathing state, for example. At this time, the user's operation may be accepted. For example, the user inputs a measurement start instruction from the touch panel 51 after instructing the patient 90 to bring about the following state.

(Step S176)
If the patient 90 has not completed the measurement in the predetermined number of types of states, the processing of the loop b from step S115 onward is repeated. On the other hand, if all the states have been measured, the loop b is exited and the process proceeds to step S18.

(Step S18)
The waveform data generator 302 generates waveform data (first distribution data) of the elements r1 to rx from the point data. At this time, waveform data associated with each state may be generated.

(Step S19)
Here, the control unit 21 determines the installation state, and determines the antenna element r to be used for cardiac output estimation after the determination. Here, the control unit 21 performs the processing shown in FIG. 12A and subsequent FIG. 12B or FIG. Specifically, the secondary distribution data generation unit 212 generates secondary distribution data, and the installation state determination unit 215 generates feature data to determine the installation state. After executing processing according to the result, the element determination unit 213 determines the antenna element r to be used for cardiac output estimation. When executing the installation state determination processing and the antenna element r determination processing, the processing may be performed for each patient state, or a plurality of states may be collectively processed (without distinction). can be

(Step S20)
The cardiac output estimation unit 214 estimates the cardiac output or the volume of blood pumped from the heart using the antenna element r determined in step S19. The processing here is the same as the processing in step S20 of FIG.

The cardiac output measurement sensor 1000 according to the third embodiment performs installation state determination processing and element determination processing based on data measured in a plurality of states of the patient 90 in the configuration of the second embodiment. Therefore, a state with high robustness can be achieved. As a result, even if the condition of the patient 90 changes while the cardiac output is being measured (step S43), the measurement can be stably performed. can be estimated by

In addition, in the present embodiment, measured values measured 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 the measured values measured at the same time or substantially at the same time, the secondary distribution data using any of the evaluation values 1 to 6 and the feature data using any of the feature amounts 1 to 5 are extracted. accuracy is improved. As a modified example, in the case of using a difference time other than the peak timing difference (evaluation value 6, feature amount 3), measurement values measured 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 antenna element t and one receiving 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.

Also, 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 the point data recording section 301 and the waveform data generating section 302. 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 addition, the predetermined cycle is set to a cycle, for example, 1 msec or less, such that one cycle time tc in which a plurality of antenna elements are turned ON is sufficiently shorter than the cardiac cycle. As a result, a sufficient sampling rate can be secured and waveforms can be generated with high accuracy.

The evaluation values are (evaluation value 1) amplitude of waveform data, (evaluation value 2) intensity at specific frequency after Fourier transform, (evaluation value 3) inflection point time of waveform data, (evaluation value 4) waveform data , (evaluation value 5) autocorrelation coefficient, and (evaluation value 6) difference time of peak timing. Even if any of these evaluation values 1 to 6 are used, it is possible to accurately determine a suitable antenna element from among a plurality of antenna elements.

The feature amounts are (feature amount 1) waveform data amplitude, (feature amount 2) autocorrelation coefficient, (feature amount 3) peak timing difference time, (feature amount 4) waveform shape, and (feature amount 5) peak position; Any one of these feature quantities 1 to 5 can be used to appropriately determine whether the installation state of the antenna array 122 (or the antenna array 113) is appropriate.

Also, by making it possible to change the circulation mode and cycle, it is possible to set the optimal conditions for the transmission and reception of electromagnetic waves.

Also, in this embodiment, microwaves are used as electromagnetic waves. Microwaves are attenuated less than other frequencies when passing through the human body and have relatively high loss. is larger than other frequencies and is suitable for measuring cardiac output.

The above-described configuration of the cardiac output measurement sensor 1000 is a main configuration for describing the features of the above-described embodiment, and is not limited to the above-described configuration. can be modified.

For example, in estimating the cardiac output, the antenna element r determined by the element determining unit is used to perform measurement again in order to improve accuracy, and the cardiac output is estimated based on the remeasured waveform data. A plurality of antenna elements may be used at the time of determination and at the time of re-measurement. Specifically, for example, when the evaluation values or feature amounts calculated in step S19 (FIG. 7/FIG. 12A) of four adjacent antenna elements r are very close, the four antenna elements r are used as cardiac output , and the cardiac output may be estimated from the average value of the cardiac output calculated based on the waveform data obtained using each antenna element r.

Also, 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 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.

This application is based on Japanese Patent Application No. 2021-54938 filed on March 29, 2021, the disclosure of which is incorporated by reference in its entirety.

REFERENCE SIGNS LIST 1000 cardiac output measurement sensors 11, 11b transmission antenna unit 110 substrate 111 transmission waveform generation section 112 high-speed switching section 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 22 Storage unit 23 Input/output I/F
24 Communication I/F
51 touch panel 52 XY stage 61 PC

Claims (20)

1. 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 cardiac output estimating unit for estimating the volume of blood pumped from the heart using the electromagnetic wave received by the receiving antenna and transmitted through the living body;
   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;
   Further, a primary distribution creating unit for creating waveform data representing temporal changes in measured values measured for each of the antenna elements and creating waveform distribution data in which the waveform data is associated with each of the antenna elements;
   an element determination unit that determines, from among the plurality of antenna elements, an antenna element to be used in estimating the blood volume based on the waveform distribution data generated by the primary distribution generation unit; Protrusion measurement sensor.
2. Further comprising a secondary distribution creation unit for creating distribution data of evaluation values according to the positions of the antenna elements based on the waveform distribution data created by the primary distribution creation unit,
   The element determination unit determines, from among the plurality of antenna elements, an antenna element to be used when estimating the blood volume, based on the distribution data of the evaluation values created by the secondary distribution creation unit. The cardiac output measurement sensor according to claim 1.
3. The cardiac output measurement sensor according to claim 1 or claim 2, wherein the measured values are measured values measured simultaneously or substantially simultaneously.
4. The one including the plurality of antenna elements further includes a high-speed switching unit that sequentially switches ON/OFF of each of the antenna elements at a predetermined cycle,
   The primary distribution creation unit includes a point data recording unit that records the measured value of each of the antenna elements turned on by the high speed switching unit as point data in association with the antenna element, and the point data recording unit. 4. The cardiac output measuring sensor according to claim 3, further comprising a waveform data generator that creates the waveform data by arranging the recorded point data over time.
5. 5. The cardiac output measurement according to claim 4, wherein the predetermined cycle is set such that one cycle time for one cycle of turning ON of the plurality of antenna elements is sufficiently shorter than a cardiac cycle. sensor.
6. The evaluation value is the amplitude of the waveform data, the intensity at a specific frequency after Fourier transform, the inflection point time of the waveform data, the time integral value of the waveform data, and/or the autocorrelation coefficient. Item 6. The cardiac output measurement sensor according to any one of items 5.
7. The cardiac output measurement sensor according to any one of claims 3 to 5, wherein the evaluation value is a differential time obtained by comparing the timing of the peak of the waveform data with the timing of the peak of the reference waveform.
8. The element determination unit determines the antenna element to be used for estimation by comparing a comparison distribution pattern prerecorded in a storage unit with the distribution data created by the secondary distribution creation unit. The cardiac output measurement sensor according to any one of claims 2 to 7.
9. The plurality of antenna elements is an antenna array arranged in a lattice on the same plane,
   an installation state determination unit that determines whether the installation state of the antenna array is appropriate,
   3. The installation state determination unit extracts feature data from the waveform distribution data or the distribution data of the evaluation values, and determines appropriateness of the installation state of the antenna array based on the feature data. The cardiac output measurement sensor according to claim 8 .
10. 3. The feature data is at least one of waveform data amplitude, autocorrelation coefficient, difference time comparing peak timing with reference waveform peak timing, waveform shape, and peak position of the evaluation value. 9. The cardiac output measurement sensor according to 9.
11. The plurality of antenna elements is an antenna array arranged in a lattice on the same plane,
    11. The cardiac output measurement sensor according to claim 7, wherein said reference waveform is waveform data of an antenna element closest to the center of said antenna array.
12. The plurality of antenna elements is an antenna array arranged in a lattice on the same plane,
    an installation state determination unit that determines whether the installation state of the antenna array is appropriate,
    The installation state determination unit compares a comparison distribution pattern recorded in advance in a storage unit with the distribution data created by the secondary distribution creation unit to determine whether the installation state of the antenna array is appropriate. The cardiac output measurement sensor according to any one of claims 2 to 8.
13. 12. The state of the living body when the installation state determination unit extracts the feature data includes at least one or more of a resting state, a deep breathing state, a body motion state, and a posture change state. Cardiac output measurement sensor according to any one of .
14. The installation state determination unit compares the feature data with a predetermined set range, and determines an abnormality when the feature data is out of the set range,
    14. The heart according to any one of claims 9 to 13, further comprising a first instruction section that outputs an instruction for re-measurement or rearrangement based on the determination of the abnormality by the installation state determination section. Cardiac output sensor.
15. The installation state determination unit compares the feature data with a predetermined set range to identify the antenna element outside the set range,
    The cardiac output measurement sensor according to any one of claims 9 to 13, wherein the element determination unit excludes the antenna element specified by the installation state determination unit from the target of the determination.
16. The installation state determination unit determines whether the installation state of the antenna array is inappropriate from the feature data,
    16. The cardiac output measurement sensor according to any one of claims 9 to 15, further comprising a second instruction section that outputs a movement direction for rearrangement.
17. The high-speed switching unit switches between a full circulation mode in which all of the plurality of antenna elements are circulated, and a partial circulation mode in which only some of the antenna elements are thinned out and circulated.
    5. The cardiac output measurement sensor according to claim 3 or 4, wherein said predetermined period or one cycle time in which a plurality of said antenna elements are turned on can be changed.
18. The element determination unit selects the antenna element based on the feature data,
    10. The cardiac output estimating unit estimates the cardiac output using a post-processing signal obtained by arithmetically processing the signal obtained from the measurement value of the antenna element selected by the element determining unit. 18. The cardiac output measurement sensor according to any one of claims 1 to 17.
19. The cardiac output measurement sensor according to any one of claims 1 to 18, wherein the electromagnetic waves are microwaves.
20. 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 cardiac output estimating unit for estimating the volume of blood pumped from the heart using the electromagnetic wave received by the receiving antenna and transmitted through the living body;
    At least one of the transmitting antenna and the receiving antenna includes a plurality of antenna elements positioned at different positions with respect to the living body, and a control program executed by a computer for controlling a cardiac output measurement sensor,
    a primary distribution creating step of creating waveform data representing temporal changes in measured values measured for each of the antenna elements, and creating waveform distribution data in which the waveform data is associated with each of the antenna elements;
    an element determination step of determining an antenna element to be used in estimating the blood volume from among the plurality of antenna elements based on the waveform distribution data created in the primary distribution creation step; , a control program to be executed by the computer.

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