WO2021066017A1

WO2021066017A1 - Estimation device and estimation method

Info

Publication number: WO2021066017A1
Application number: PCT/JP2020/037161
Authority: WO
Inventors: 筱薇呂; 信一郎須田; 圭本田
Original assignee: テルモ株式会社
Priority date: 2019-09-30
Filing date: 2020-09-30
Publication date: 2021-04-08
Also published as: JPWO2021066017A1

Abstract

An estimation device (100) is an estimation device for estimating an electrical characteristic value of a chest (H). The estimation device has: a transmission antenna (111) that transmits microwaves to the chest; a reception antenna (112) that receives the microwaves that have passed through the chest; and an estimation unit (126) that estimates the electrical characteristic value from a waveform difference between the waveform of the transmitted microwaves and the waveform of the received microwaves on the basis of the relationship between the electrical characteristic value and the waveform difference between the waveform of the transmitted microwaves and the waveform of the received microwaves.

Description

Estimator and estimation method

The present invention relates to an estimation device and an estimation method for estimating electrical characteristic values of a living body.

Conventional techniques for estimating the amount of change in the volume of body fluid in a living organ such as cardiac output include the device described in Patent Document 1 including a transmitting antenna, a receiving antenna, and an estimation unit. In the above device, the transmitting antenna transmits microwaves and the like to the chest of the patient, the receiving antenna receives the microwaves and the like transmitted through the chest, and the estimating unit estimates the cardiac output from the electric field strength of the received microwaves.

International Publication No. 2018/194093

By the way, when microwaves propagate in a living body, the microwaves are attenuated due to electrical characteristics such as the dielectric properties of the living body. Therefore, for example, when estimating the amount of change in the volume of body fluid in a living organ such as cardiac output using transmitted microwaves, it is important to grasp the electrical characteristic value of the living body.

Therefore, an object of the present invention is to provide an estimation device and an estimation method capable of estimating the electrical characteristic values of a living body.

The estimation device according to the present invention that achieves the above object is an estimation device for the electrical characteristic value of a living body, and is a transmitting unit that transmits microwaves to the living body and a receiving unit that receives the microwave transmitted through the living body. And, based on the relationship between the waveform difference of the transmitted microwave and the waveform of the received microwave and the electrical characteristic value, the estimation of the electrical characteristic value is estimated from the waveform difference of the transmitted microwave and the received microwave. It has a part and.

The estimation method according to the present invention that achieves the above object is a method of estimating the electrical characteristic value of a living body, which transmits microwaves to the living body, receives microwaves transmitted through the living body, and transmits microwaves and receives. Based on the relationship between the microwave waveform difference and the electrical characteristic value, the electrical characteristic value is estimated from the waveform difference between the transmitted microwave and the received microwave.

According to the estimation device and method according to the present invention, the electrical characteristic value of the living body can be estimated.

It is a block diagram which shows the estimation apparatus which concerns on one Embodiment of this invention. It is the schematic which shows the transmitting antenna and the receiving antenna provided in the estimation apparatus shown in FIG. It is a graph which shows an example of the electric field strength of the transmission microwave and the electric field strength of the reception microwave of the estimation apparatus shown in FIG. It is a flowchart which shows the estimation method by the estimation apparatus shown in 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 designated by the same reference numerals, and duplicate description will be omitted. The size and ratio of the members in the drawings may be exaggerated for convenience of explanation and may differ from the actual size and ratio.

(Estimator)
_{The estimation device 100 shown in FIG. 1 has a cardiac output ΔV blood} (change amount ΔV) in the living body of a patient (subject) in a heart failure test, follow-up after heart surgery, verification of a medication effect of heart disease, and the like. It is composed so that it can be estimated (corresponding to _{body fluid).} In the present specification, the cardiac output ΔV _blood is an expanded state (corresponding to the first volume) of the blood (corresponding to the body fluid) contained in the heart H1 (corresponding to a biological organ) having the maximum volume (corresponding to the first volume). It means the amount of change in blood volume between the contraction state (corresponding to the second state) of the heart H1 in which the blood is the minimum volume (corresponding to the second volume) (corresponding to the state 1). That is, in the present specification, the cardiac output ΔV _blood means the so-called stroke volume.

As shown in FIG. 1, the estimation device 100 includes a transmitting antenna 111 (corresponding to a transmitting unit), a receiving antenna 112 (corresponding to a receiving unit), a transmitting waveform generating unit 113, and a receiving waveform preprocessing unit 114. .. The estimation device 100 includes a control unit 120, a start switch 130, a notification unit 140, and an input unit 150. The estimation device 100 is configured to be able to communicate with the external terminal 160. The details will be described below.

(Transmitting antenna and receiving antenna)
As shown in FIGS. 1 and 2, the transmitting antenna 111 is electrically connected to the transmitting waveform generating unit 113, and the patient's chest H (heart H1 and living tissue H2 other than the heart H2) in the expanded and contracted states of the heart H1. (Including) is configured to be able to transmit microwaves. Examples of the biological tissue H2 other than the heart H1 include skin, adipose tissue, and muscle.

As shown in FIG. 2, the receiving antenna 112 is arranged so as to face the transmitting antenna 111. The receiving antenna 112 is configured to be able to receive microwaves transmitted by the transmitting antenna 111 and transmitted through the patient's chest H.

The transmitting antenna 111 and the receiving antenna 112 can be configured by a dipole type linear antenna or the like. However, the formats of the transmitting antenna 111 and the receiving antenna 112 are not particularly limited as long as microwaves can be transmitted and received. The transmitting antenna 111 and the receiving antenna 112 may be a linear antenna of a microloop type or a helical type, or may be a flat antenna of a patch type or an inverted F type.

(Transmission waveform generator)
The transmission waveform generator 113 is composed of a microwave generator. The frequency of the generated microwave is not particularly limited as long as it can pass through the human heart H1, but can be, for example, 0.4 to 1.0 GHz. The power of the generated microwave is not particularly limited as long as sufficient power can be detected by the receiving antenna 112, but can be, for example, several mW to several tens of mW. Further, the generated microwave may be a continuous wave, a pulse wave, or an electromagnetic wave subjected to phase modulation or frequency modulation.

(Received waveform pre-processing unit)
The reception waveform preprocessing unit 114 performs preprocessing such as AD conversion so that the control unit 120, which will be described later, can process the microwave received from the reception antenna 112. The received waveform preprocessing unit 114 can be configured by, for example, an AD converter or the like.

(Control unit)
As shown in FIG. 1, the control unit 120 includes a processor 121 such as a CPU, a storage unit 122, and a communication unit 123. The processor 121, the storage unit 122, and the communication unit 123 are connected to each other by a bus (not shown).

In the present embodiment, the processor 121 has functions as an acquisition unit 124, a signal processing unit 125, and an estimation unit 126. Hereinafter, each function of the processor 121 will be described in detail.

The acquisition unit 124 controls the operation of the transmission waveform generation unit 113 so that the transmission antenna 111 transmits microwaves during a period in which the expansion and contraction cycle of the heart H1 is included at least once. Further, the acquisition unit 124 receives a microwave (transmitted microwave) transmitted by the transmitting antenna 111 and a microwave (received microwave) received by the receiving antenna during a period in which the expansion and contraction cycle of the heart H1 is included at least once. To get. The transmitted microwave and received microwave data acquired by the acquisition unit 124 are stored in the storage unit 122.

The signal processing unit 125 performs processing such as filtering on the transmitted microwave and the received microwave acquired by the acquisition unit 124. Details of the processing of the signal processing unit 125 will be described later.

The estimation unit 126 estimates the electrical characteristic value of the chest H from the waveform difference between the transmitted microwave and the received microwave. Further, the estimation unit 126 estimates the energy absorption amount difference ΔP from the received microwaves in the expanded state and the contracted state by using the estimated electrical characteristic value of the chest H. _{Here, the energy absorption difference ΔP is the energy absorption amount P d} (corresponding to the energy absorption amount P ₁ ) absorbed by the chest H from the microwave in the expanded state and the energy absorption amount absorbed by the chest H from the microwave in the contracted state. This is the difference from _{P s} (corresponding to the amount of energy absorbed P _2). Then, the estimation unit 126 estimates the cardiac output ΔV _blood using the energy absorption amount difference ΔP. Hereinafter, the method of estimating each value of the estimation unit 126 will be described in detail.

First, a method in which the estimation unit 126 estimates the electrical characteristic value of the chest H will be described.

When a high-frequency electromagnetic wave such as a microwave passes through a loss medium, it is attenuated (reduced in amplitude) or phase-delayed with respect to the microwave before passing through the loss medium due to electrical characteristics such as the dielectric property of the loss medium. Occurs. Since the living body is also a loss medium, the microwave (received microwave) transmitted through the chest H has a waveform difference such as attenuation or phase delay with respect to the transmitted microwave due to the electrical characteristics of the chest H. Utilizing such a principle, the estimation unit 126 determines the waveform of the transmitted microwave and the waveform of the received microwave based on the relationship between the waveform difference between the transmitted microwave and the received microwave and the electrical characteristic value of the chest H. The electrical characteristic value of the chest H is estimated from the waveform difference.

In the following, an example will be described in which the estimation unit 126 estimates the dielectric loss tangent tan δ and the dielectric constant ε as the electrical characteristic values of the chest H.

The microwave transmitted by the transmitting antenna 111 is actually a spherical wave, but the microwave observed by the receiving antenna 112 installed at a point sufficiently distant from the transmitting antenna 111 has a spherical radius approaching infinity. Therefore, it can be regarded as a plane wave. From the solution of the wave equation of the plane wave propagating in the loss medium, the microwave Ez propagating from the transmitting antenna 111 toward the receiving antenna 112 (in the microwave transmitting direction z) is expressed by the following equation (1-1). Can be done.

Here, it is known that the attenuation constant α can be expressed by the following equation (1-2), and the phase constant β can be expressed by the following equation (1-3).

If the thickness of the thoracic H and L, and the amplitude E _i of the received microwave passes through the chest H by substituting z = L to the amplitude part of the above formula (1-1), the following equation (1-4 ) Can be expressed.

Therefore, the amplitude difference A (see FIG. 3) between _{the amplitude E 0} of the transmitted microwave and the amplitude E _{i of the received microwave can be expressed by the following equation (1-5).} Here, the amplitude difference A means a quantity expressed by the logarithm (decibel) of the ratio of _{the amplitude E i} of the lower received microwave and the amplitude E _{0 of the transmitted microwave.}

Here, it is generally known that the following relationship holds.

By substituting equations (1-6) to (1-8) into equation (1-5), the relationship between the amplitude difference A of the transmitted microwave and the received microwave and the dielectric constant ε and the dielectric loss tangent tan δ is expressed as follows. Equation (1-9) is obtained.

Further, from the equation (1-1), the relationship between the phase difference θ (see FIG. 3) of the transmitted microwave and the received microwave and the dielectric constant ε and the dielectric loss tangent tan δ can be expressed by the following equation (1-10). ..

The estimation unit 126 is based on the relational expression (1-9) between the amplitude difference A and the dielectric loss tangent tan δ of the chest H and the relational expression (1-10) between the phase difference θ and the dielectric loss tangent tan δ of the chest H. , The dielectric loss tangent tan δ of the chest H is estimated from the amplitude difference A and the phase difference θ.

Here, the amplitude difference A and the phase difference θ of the transmitted microwave and the received microwave are values calculated from the transmitted microwave and the received microwave measured by the estimation unit 126. The speed of light c is a known value. Further, the frequency f of the transmitted microwave is a set value of the frequency of the microwave generated by the transmission waveform generation unit 113. Further, the thickness L of the chest H may be a value obtained by measuring the thickness L of the chest H of the patient by the estimation device 100 using a length measuring instrument or the like, or the user such as a doctor or a nurse may be the patient. The thickness L of the chest H may be measured, and the thickness L of the chest H may be input to the estimation device 100 by the input unit 150.

Also, equation (1-9) can be transformed as follows.

Further, from the equation (1-1), the relationship between the phase difference θ (see FIG. 3) of the transmitted microwave and the received microwave and the dielectric constant ε and the dielectric loss tangent tan δ can be expressed by the following equation (1-12). ..

The estimation unit 126 uses the relational expression (1-11) between the estimated dielectric loss tangent tan δ and the amplitude difference A and the magnetic permeability μ and the permittivity ε of the chest H, and the estimated dielectric loss tangent tan δ and the phase difference θ and the transparency of the chest H. Based on the relational expression (1-12) between the magnetic coefficient μ and the dielectric constant ε, the dielectric constant ε of the chest H is estimated from the amplitude difference A and the phase difference θ.

As described above, the estimation unit 126 includes the relational expressions (1-9) and (1-11) between the amplitude difference A and the electrical characteristic values of the chest H, and the electrical characteristic values of the phase difference θ and the chest H. The dielectric loss tang tan δ and the permittivity ε of the chest H are estimated from the amplitude difference A and the phase difference θ based on the relational expressions (1-10) and (1-12) of.

The electric field strength of the microwave transmitted through the heart H1 changes according to the blood volume of the heart H1 (that is, according to the expansion and contraction of the heart H1). Therefore, the received microwave not only causes an amplitude difference A and a phase difference θ with respect to the transmitted microwave by passing through the chest H, which is a loss medium, but also has a periodic electric field strength due to the expansion and contraction of the heart H1. Changes also occur. Therefore, the estimation unit 126 excludes the periodic change in the electric field strength due to the expansion and contraction of the heart H1 when estimating the electrical characteristic value, and the amplitude difference A and the phase difference θ of the transmitted microwave and the received microwave. It is desirable to calculate.

In the present embodiment, the amplitude difference A and the phase difference θ of the received microwave generated by passing through the chest H, which is a loss medium, with respect to the transmitted microwave are extremely higher than the frequency of expansion contraction (GHz order). ) This is the waveform change in the nearby components. Therefore, the amplitude difference A and the phase difference θ caused by passing through the chest H, which is a loss medium, and the periodic change in the electric field strength due to the expansion and contraction of the heart H1 can be clearly distinguished. For example, the estimation unit 126 extracts time-series data for a period in which the pumping state of the heart H1 can be regarded as substantially constant from the time-series data of the transmission microwave and the reception microwave, and extracts the time-series data from the extracted transmission microwave and the reception microwave. , Amplitude difference A and phase difference θ may be calculated. Further, for example, the signal processing unit 125 performs a filtering process such as a bandpass filter on the received microwave to exclude the fluctuation component due to the expansion contraction, and the estimation unit 126 extracts the received microwave and the received microwave after the filtering process. The amplitude difference A and the phase difference θ may be calculated.

Next, a method in which the estimation unit 126 estimates the energy absorption amount difference ΔP using the electrical characteristic value of the chest H and the received microwaves in the expanded state and the contracted state will be described.

When the dielectric is in the electric field strength E, the energy absorption amount p (power consumption or dielectric loss) absorbed by the dielectric per unit volume can be expressed by the following equation (2-1).

Therefore, the energy absorption amount p _d which is absorbed into the chest H per unit volume in the expanded _state, and the energy absorption amount p _s to be absorbed into the chest H per unit volume in the contracted state, the following equation (2-2) And (2-3).

The electric field strength of the received microwave varies depending on the amount of blood in the heart H1. Therefore, from the electric field strength of the received microwave, it is possible to determine in which state the heart H1 has transmitted the microwave. Field strength E _d expanded state of the chest H, in the field strength of the received microwave corresponds to the minimum value in the period of one expansion shrinkage (minimum value). Field strength E _s deflated chest H, in the field strength of the received microwave corresponds to the maximum value in the period of one expansion shrinkage (maximum value). When the received microwave is acquired over a plurality of expansion contraction cycles, the estimation unit 126 sets the average value obtained by averaging the maximum values within the plurality of expansion contraction cycles as the electric field strength E in the expanded state of the chest H. and _d, an average value obtained by averaging the local minimum values in the period of the plurality of extended contraction may be the electric field strength E _s deflated chest H. The signal processing unit 125 performs filtering processing such as a bandpass filter so that the estimation unit 126 removes components other than the fluctuation component due to expansion and contraction from the received microwave before calculating the maximum value and the minimum value. You may.

_{The energy absorption difference ΔP between the energy absorption amount P d of the} entire chest H in the expanded state _{and the energy absorption amount P s of the} entire chest H in the contracted state can be expressed by the following equation (2-4).

_{The volume V body} of the portion of the chest H through which microwaves are transmitted can be calculated by, for example, (chest thickness L × antenna area S). Strictly speaking, the volume V _body changes as the volume of blood in the heart H1 changes due to the expansion and contraction of the heart H1. However, since the volume that changes with the expansion and contraction of the heart H1 is sufficiently smaller than the volume that does not change with the expansion and contraction of the heart H1, the volume V _body can be treated as a constant value.

Estimating unit 126, based on the equation (2-2) to formula (2-4), electric characteristic values of the chest H, the electric field intensity of the received microwave field strength E _d and the contracted state of the received microwave expanded state E _s, the frequency f of the transmitted microwave, antenna area S, and the thickness of the thoracic L, estimates the energy absorption amount difference ΔP from. The electrical characteristic value of the chest H is an estimated value estimated by the estimation unit 126 as described above. Further, the electric field strength E _s of the received microwave field strength E _d and the contracted state of the received microwave expanded state, a value estimating unit 126 has calculated from the received microwaves as described above. Further, the antenna area S means an area where microwaves are transmitted and received in the transmitting antenna 111 and the receiving antenna 112, and is a set value depending on the transmitting antenna 111 and the receiving antenna 112 incorporated in the estimation device 100.

The estimation unit 126 does not necessarily have to estimate the electrical characteristic value of the chest H. For example, the estimation unit 126 may estimate the energy absorption amount difference ΔP by using a known electric characteristic value of a living body or an electric characteristic value measured by another device. However, the electrical characteristic value may change depending on the environment even for the same patient due to environmental conditions such as temperature and humidity. In addition, the electrical characteristic value may differ from patient to patient due to differences in fat content, water content, and the like. In particular, patients with heart failure have a larger amount of water than normal people due to body congestion and the like, so the electrical characteristic values may differ significantly from normal people. Therefore, it is better for the estimation unit 126 _{to estimate the electrical characteristic value for each patient each time the cardiac output ΔV blood} is estimated, and to estimate the energy absorption amount difference ΔP using the estimated electrical characteristic value. This is preferable from the viewpoint of accurately estimating the difference ΔP.

In this embodiment, the time interval between the diastole and the systole is short, for example, about 0.5 seconds. Therefore, it is considered that the electrical characteristic value does not change during that period, and the same electricity is used in the diastole and the systole. Characteristic values are used. However, the estimation unit 126 estimates the electrical characteristic value in the expanded state from the waveform difference between the transmitted microwave and the received microwave in the expanded state, and the contracted state is derived from the waveform difference between the transmitted microwave and the received microwave in the contracted state. The electrical characteristic value may be estimated. As a result, a more accurate electrical characteristic value can be estimated according to each state.

Next, a method in which the estimation unit 126 estimates the cardiac output ΔV _blood using the energy absorption amount difference ΔP will be described.

As described above, there is an energy absorption difference ΔP between the energy absorption amount Pd of the entire chest H in the expanded state and the energy absorption amount Ps of the entire chest H in the contracted state. Examples of the components constituting the chest H include skin, muscle, fat, blood and the like. In the portion where microwaves are transmitted, the only component whose volume changes in the expanded state and the contracted state is blood, and it is considered that the volume of other components such as skin, muscle, and fat does not change. The present inventors focused on this point, the capacity of blood and expanded state contracted state is changed by amount of cardiac output [Delta] V _blood, absorbing energy blood aliquot of cardiac output [Delta] V _blood absorbs A new idea was obtained that the amount P _blood ( _{corresponding to P body fluid} ) is equal to the energy absorption difference ΔP between the energy absorption amount Pd of the entire chest in the expanded state and the energy absorption amount Ps of the entire chest in the contracted state. Specifically, this new idea can be expressed by the following equation (3-1).

Here, the absorbed energy amount P _blood _{absorbed by the blood in} the amount of the heartbeat output amount ΔV blood is the specific absorption rate SAR indicating the energy absorption amount per unit mass of blood as shown in the following formula (3-2). _blood (corresponding to SAR _{body fluid)} can be represented by the cardiac output [Delta] V _blood, and the density of the blood [rho _blood (corresponding to [rho _{body fluid).}

Therefore, the following equation (3-3) can be obtained from the equations (3-1) and (3-2).

Based on the above equation (3-3), the estimation unit 126 estimates the cardiac output ΔV _blood _{from the energy absorption difference ΔP, the specific absorption rate SAR blood of blood} , and the blood density ρ _blood . The energy absorption amount difference ΔP is an estimated value estimated by the estimation unit 126 from the electrical characteristic value and the received microwaves in the expanded state and the contracted state as described above. The specific absorption rate of _blood, SAR blood, and the density of _{blood, ρ blood,} are known values. As described above, the estimation unit 126 receives the received microwaves in the expanded state and the contracted state based on the relationship that the absorbed energy amount P _blood _{absorbed by the blood in the amount of the cardiac output ΔV blood is equal to the energy absorption amount difference ΔP.} From this, the cardiac output ΔV _blood can be estimated.

Estimation unit 126 according to this embodiment, the energy absorption amount difference ΔP caused by the amount of change in volume of blood (cardiac output [Delta] V _blood), estimates cardiac output [Delta] V _blood. Therefore, the estimation unit 126 can accurately estimate the _{cardiac output ΔV blood} as compared with the conventional technique of estimating the _{cardiac output ΔV blood} with the mass M of the heart H1 constant.

Further, as described above, in the prior art, the electric field strength of the heart H1 in each state is replaced with the electric field strength of the received microwave in each state, and the energy absorption amount of the heart H1 per unit volume in each state is set to ". It was estimated as "the electric field strength of the received microwave in each state x the conductivity of the heart". However, since microwaves pass through not only the heart H1 but also living tissues H2 other than the heart H1, strictly speaking, the amount of energy absorbed by the heart H1 alone cannot be calculated from the electric field strength of the received microwaves. On the other hand, the estimation unit 126 according to the present embodiment is based on the electrical characteristic values of the chest H including the heart H1 and the biological tissue H2 other than the heart H1 and the electric field strength of the received microwave, and the chest H in the expanded state and the contracted state The energy absorption difference ΔP is estimated. Then, the estimation unit 126, the energy absorption amount difference ΔP caused by the amount of change in volume of blood in the heart H1 (cardiac output [Delta] V _blood), estimates cardiac output [Delta] V _blood. Therefore, the estimation unit 126 can accurately estimate the _{cardiac output ΔV blood} even if there is an interposition of a biological tissue H2 other than the heart H1 between the heart H1 and the receiving antenna 112.

The storage unit 122 stores various data necessary for estimation by the estimation unit 126. The storage unit 122 can be configured by a ROM, RAM, or the like.

In the present embodiment, the storage unit 122 stores data such as a waveform of the transmitted microwave and a waveform of the received microwave. In the present embodiment, the storage unit 122 stores an input value such as a patient ID. In the present embodiment, the storage unit 122 stores the measured values such as the thickness L of the chest H, the antenna area S, and the set values such as the frequency f of the transmitted microwave. In the present embodiment, the storage unit 122 stores predetermined values such as the _{speed of light c, the blood absorption rate SAR blood,} and the blood density ρ _blood. In the present embodiment, the storage unit 122 stores estimated values such as the dielectric constant ε, the dielectric loss tangent tan δ, the energy absorption amount difference ΔP, and the cardiac output ΔV _blood.

The communication unit 123 enables data to be transmitted / received between the estimation device 100 such as the external terminal 160 and a device different from the estimation device 100. The communication unit 123 is configured to enable wired or wireless communication with the external terminal 160. The communication unit 123 can be configured by, for example, a network card or a port (interface) of a wired cable such as USB (Universal Serial Bus).

(Start switch)
The start switch 130 is configured so that a user such as a medical worker such as a doctor or a nurse can instruct the start of estimation of the _{cardiac output ΔV blood.} The specific mode of the start switch 130 is not particularly limited as long as it can be switched on and off, and examples thereof include a toggle type switch and a button type switch.

(Notification unit)
The notification unit 140 notifies the cardiac output ΔV _blood estimated by the estimation unit 126 by various means. The specific mode of the notification unit 140 is _{not particularly limited as long as it can notify the user of the cardiac output ΔV blood} , but it can be configured by, for example, a display unit such as a speaker that performs voice notification or a display that performs display notification.

(Input section)
The input unit 150 is configured so that a user such as a medical worker can input information about the patient to the estimation device 100. The input unit 150 can be configured by any one of a push button, a keyboard, a pointing device such as a mouse, or a combination thereof in whole or in part. Although the input unit 150 is a component of the estimation device 100 in the present embodiment, the estimation device does not include a configuration corresponding to the input unit 150 other than this, and the estimation device may be externally attached to other embodiments of the present invention. include.

(External terminal)
The external terminal 160 is configured to enable communication of index data related to the heart with the estimation device 100 through the communication unit 116. The external terminal 160 can be configured by a known tablet (type terminal), a personal computer, or the like.

(Estimation method)
Next, the estimation method according to the present embodiment will be described. FIG. 4 is a flowchart showing an estimation method according to the present embodiment. To outline the estimation method according to the present embodiment with reference to FIG. 4, the transmission / reception of microwaves (S1), signal processing (S2), estimation of electrical characteristic values (dielectric constant ε and dielectric loss tangent tan δ) (S3), energy. The absorption amount difference ΔP is estimated (S4), the cardiac output ΔV _blood is estimated (S5), and the cardiac output ΔV _blood is notified (S6). The details will be described below.

The estimation device 100 receives an input from the input unit 150 by the user and acquires information about the patient such as a patient ID and the like.

Next, when the start switch 130 is operated by the user, the acquisition unit 124 controls the operation of each unit to transmit and receive microwaves (S1). Specifically, the transmission waveform generation unit 113 generates a microwave to irradiate the patient's chest H and transmits it from the transmission antenna 111. The microwave transmitted through the chest H is received by the receiving antenna 112. The reception waveform preprocessing unit 114 converts the microwave received by the reception antenna 112 from an analog signal to a digital signal. The acquisition unit 124 acquires the transmitted microwave and the received microwave during a period including at least one expansion / contraction cycle.

Next, the signal processing unit 125 performs processing such as filtering on the transmitted microwave and the received microwave (S2).

Next, the estimation unit 126 of the control unit 120 describes the relational expression (1-9) between the amplitude difference A of the transmission microwave and the reception microwave and the dielectric constant ε and the dielectric loss tangent tan δ of the chest H, and the transmission microwave and the reception. Based on the relational expression (1-10) between the phase difference θ of the microwave and the permittivity ε of the chest H and the dielectric loss tangent tan δ, from the amplitude difference A and the phase difference θ of the transmitted microwave and the received microwave, the chest The permittivity ε of H and the dielectric loss tangent tan δ are estimated (S3).

Next, the estimation unit 126 includes the dielectric constant ε and the dielectric loss tangent tan δ of the chest H estimated in step S3 based on the equations (2-2) to (2-4), and the electric field of the received microwave in the expanded state. The energy absorption amount difference ΔP is calculated from the electric field strength Es of the received microwave in the contracted state and the strength Ed and the volume V _{body of the portion where the microwave is transmitted in the chest H (S4).}

Next, the estimation unit 126 determines the energy absorption amount based on the relational expression (3-3) that the energy absorption amount P _blood _{absorbed by the blood in} the amount of the cardiac output ΔV blood is equal to the energy absorption amount difference ΔP. _{Cardiac output ΔV blood} is estimated from the difference ΔP (S5).

Next, the notification unit 140 notifies the _{user of the cardiac output ΔV blood} estimated in step S5 (S6).

As described above, the estimation device 100 according to the present embodiment is an estimation device for the electrical characteristic value of a living body. The estimation device 100 includes a transmission antenna 111, a reception antenna 112, and an estimation unit 126. The transmitting antenna 111 transmits microwaves to the living body. The receiving antenna 112 receives the microwave transmitted through the living body. The estimation unit 126 estimates the electrical characteristic value from the waveform difference between the transmitted microwave and the received microwave based on the relationship between the waveform difference between the transmitted microwave and the received microwave and the electrical characteristic value.

Further, the estimation method according to the present embodiment is a method for estimating the electrical characteristic value of a living body. In the estimation method according to the present embodiment, microwaves are transmitted to a living body and microwaves transmitted through the living body are received. Then, based on the relationship between the waveform difference between the transmitted microwave and the received microwave and the electrical characteristic value, the electrical characteristic value is estimated from the waveform difference between the transmitted microwave and the received microwave.

According to the estimation device 100 and the estimation method, the electrical characteristic value of the living body can be estimated.

Further, the estimation unit 126 has at least one of the relationship between the amplitude difference A of the transmitted microwave and the received microwave and the electrical characteristic value, and the relationship between the phase difference θ of the transmitted microwave and the received microwave and the electrical characteristic value. Estimate the electrical characteristic values based on the relationship. Therefore, the estimation unit 126 can estimate the electrical characteristic value by a simple method of calculating the amplitude difference A and / or the phase difference θ of the received microwave and the transmitted microwave.

Further, the estimation unit 126 estimates the dielectric constant ε and / or the dielectric loss tangent tan δ as electrical characteristic values. Therefore, it is possible to estimate the energy absorption amount (dielectric loss) of the living body from the estimated dielectric constant ε and / or the dielectric loss tangent tan δ.

The microwave frequency is 0.4 to 1.0 GHz. The higher the frequency, the greater the attenuation of electromagnetic waves by the living tissue, and the more important it is to grasp the electrical characteristic values of the living body. Therefore, the effect of the present invention becomes remarkable in the measuring device using microwaves.

In addition, the estimation unit 126 estimates the electrical characteristic value of the chest H. Therefore, the estimated electrical characteristic value of the chest H can be used for estimating the cardiac output ΔV and the like.

Note that this embodiment is not limited to the above-described embodiment, and various changes can be made within the scope of claims.

For example, the electric specific value estimated by the present invention is not limited to the dielectric constant ε and the dielectric loss tangent tan δ. For example, in the present invention, conductivity σ, magnetic permeability μ, and the like may be estimated as electrical characteristic values. Further, for example, when at least one of the dielectric constant ε and the dielectric loss tangent tan δ is known, at least one of the equations (1-9) and (1-10) is used to determine the electrical characteristic value of the other. You may estimate.

Further, for example, in the above embodiment, the embodiment in which the electrical characteristic value of the chest is estimated and the estimated electrical characteristic value is used for the estimation of the cardiac output has been described. However, the part for estimating the electrical characteristic value and the use of the electrical characteristic value are not particularly limited. For example, the electrical characteristic value of the living body may be used for estimating the amount of change in the volume of body fluid in other living organs such as the lung and the bladder.

Further, in the estimation device and the estimation method according to the above embodiment, the so-called stroke volume is estimated as _{the cardiac output ΔV blood} , but the so-called cardiac output is calculated by the sum of the _{ΔV blood in one minute.} The cardiac index may be estimated by estimating or further dividing by the body surface area.

This application is based on Japanese Patent Application No. 2019-179104, which was filed on September 30, 2019, and the disclosure contents are cited as a whole by reference.

100 estimator,
111 Transmitting antenna (transmitter),
112 Receiving antenna (receiver),
126 Estimator.

Claims

It is an estimation device for the electrical characteristics of living organisms.
A transmitter that transmits microwaves to the living body,
A receiving unit that receives the microwave that has passed through the living body,
An estimation unit that estimates the electrical characteristic value from the difference between the transmitted microwave waveform and the received microwave waveform based on the relationship between the transmitted microwave waveform and the received microwave waveform difference and the electrical characteristic value. An estimation device having.
The estimation unit is at least the relationship between the amplitude difference between the transmitted microwave and the received microwave and the electrical characteristic value, and the relationship between the phase difference between the transmitted microwave and the received microwave and the electrical characteristic value. The estimation device according to claim 1, wherein the electrical characteristic value is estimated based on one of the relationships.
The estimation device according to claim 2, wherein the estimation unit estimates the dielectric constant and / or the dielectric loss tangent as the electrical characteristic value.
The estimation device according to any one of claims 1 to 3, wherein the frequency of the microwave is 0.4 to 1.0 GHz.
The estimation device is the estimation device according to any one of claims 1 to 4, which estimates the electrical characteristic value of the chest.
It is a method of estimating the electrical characteristics of living organisms.
Microwaves are transmitted to the living body to
Upon receiving the microwave that has passed through the living body,
An estimation method for estimating the electrical characteristic value from the waveform difference between the transmitted microwave and the received microwave based on the relationship between the waveform difference between the transmitted microwave and the received microwave and the electrical characteristic value.