Fetal heart rate measuring device, fetal heart rate measuring system, and fetal heart rate measuring program

Abstract

To determine whether or not a measured numerical value is a pulse rate of a mother when measuring a fetal heart rate on the basis of a Doppler signal indicating a differential frequency between a frequency of an ultrasonic wave transmitted toward the heart of a fetus and a frequency of a reflection wave of the ultrasonic wave.SOLUTION: A Doppler signal forming unit 18 forms a Doppler signal indicating a differential frequency between a frequency of an ultrasonic wave transmitted toward the heart of a fetus and a frequency of a reflection wave of the ultrasonic wave. A learning model 30 learns so as to determine whether or not the Doppler signal includes a mother's pulse component using a feature amount indicating a Doppler signal including a mother's pulse component as learning data, and outputs the result. A mother's pulse component determination unit 32 determines whether or not a mother's pulse component is included in the object Doppler signal by inputting the object Doppler signal, which is a Doppler signal of a determination processing object, formed by the Doppler signal forming unit 18 to the learning model 30 that has learned.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This specification discloses improvements in fetal heart rate measurement devices, fetal heart rate measurement systems, and fetal heart rate measurement programs. [Background technology]

[0002] Conventionally, fetal heart rate has been measured. As a method for measuring the fetal heart rate, a method using a fetal electrocardiograph has been proposed, but a method for measuring the fetal heart rate based on a Doppler signal obtained from a reflected wave from the fetal heart by transmitting an ultrasonic wave toward the fetal heart has also been proposed. Since the Doppler signal detects the movement of an object to be examined, the measurement of the fetal heart rate based on the Doppler signal can be said to be a measurement method based on the period of the movement of the fetal heart.

[0003] For example, Patent Document 1 discloses a technology for measuring the fetal heart rate by transmitting ultrasound toward the fetus, obtaining a Doppler signal from the wave reflected from the fetus, and performing autocorrelation processing on the Doppler signal to detect its periodicity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP Patent Publication No. 10-028686 Summary of the Invention [Problem to be solved by the invention]

[0005] Because the fetus is inside the mother's body, or because sound waves spread as they travel, even if ultrasound is transmitted toward the fetal heart, it is not possible to transmit the ultrasound only to the fetal heart. As a result, the ultrasound probe that transmits ultrasound toward the fetal heart receives not only the reflected waves from the fetal heart, but also the reflected waves from the surrounding tissues. Therefore, the Doppler signal for measuring the fetal heart rate includes not only a signal indicating the fetal heartbeat, but also a signal indicating the movement of the surrounding tissues.

[0006] In particular, the ultrasound probe may receive reflected waves from the mother's blood flow. Since the mother's blood flow velocity periodically varies in response to the mother's pulse, a Doppler signal containing a maternal pulse component will contain the maternal blood flow velocity that periodically varies (i.e., the maternal pulse component that corresponds to the mother's pulse). When attempting to measure the fetal heart rate based on such a Doppler signal, the maternal pulse rate may be measured instead of the fetal heart rate.

[0007] The purpose of the fetal heart rate measuring device, fetal heart rate measuring system, or fetal heart rate measuring program disclosed in this specification is to determine whether the measured value is the maternal pulse rate when measuring the fetal heart rate based on a Doppler signal representing the difference frequency between the frequency of an ultrasound wave transmitted toward the fetal heart and the frequency of the reflected wave of the ultrasound. [Means for solving the problem]

[0008] The fetal heart rate measuring device of this embodiment is a fetal heart rate measuring device that measures the heart rate of the fetus based on a Doppler signal that represents the difference frequency between the frequency of an ultrasound wave transmitted toward the fetal heart and the frequency of a reflected wave of the ultrasound, and is characterized in that it includes a maternal pulse component determination unit that determines whether or not the target Doppler signal contains the maternal pulse component based on output data of a learning model trained to determine whether or not the Doppler signal contains the maternal pulse component by using a feature value that represents a Doppler signal including a maternal pulse component corresponding to the maternal pulse as learning data and outputting the result. The learning model is trained to determine whether or not the Doppler signal contains the maternal pulse component based on output data of the learning model when a feature value that represents a target Doppler signal, which is the Doppler signal to be subjected to the determination process, is input.

[0009] The learning model may be trained using the learning data further including a feature quantity representing a Doppler signal in which a fetal heart rate component corresponding to a fetal heart rate is dominant among the Doppler signals.

[0010] The feature representing the Doppler signal may be an acoustic feature when the Doppler signal is viewed as an audio signal, and the feature representing the target Doppler signal may be an acoustic feature when the target Doppler signal is viewed as an audio signal.

[0011] The device may further include a notification unit that, when the maternal pulse component determination unit determines that the target Doppler signal contains the maternal pulse component, notifies a user that the target Doppler signal contains the maternal pulse component.

[0012] The present invention further includes a waveform forming unit that forms an output waveform representing the time change of the fetal heart rate or the maternal pulse rate measured based on the target Doppler signal, and the notification unit displays the output waveform on a display in a manner that enables a distinction to be made between a waveform portion formed based on the target Doppler signal including the maternal pulse component and a waveform portion formed based on the target Doppler signal not including the maternal pulse component.

[0013] The fetal heart rate measuring system according to the present embodiment is a fetal heart rate measuring system including a fetal heart rate measuring device that measures the heart rate of the fetus based on a Doppler signal that represents a difference frequency between the frequency of an ultrasound wave transmitted toward the fetal heart and the frequency of a reflected wave of the ultrasound, and a maternal pulse component determining device, wherein each of the fetal heart rate measuring devices includes a measurement device side communication unit that transmits a target Doppler signal, which is the Doppler signal to be subjected to determination processing, to the maternal pulse component determining device, and the maternal pulse component determining device includes a maternal pulse component determining unit that determines whether or not each of the target Doppler signals includes the maternal pulse component based on output data of a learning model when a feature value representing each of the target Doppler signals transmitted from each of the fetal heart rate measuring devices is input to the learning model that is trained to determine whether or not the Doppler signal includes the maternal pulse component using a feature value representing a Doppler signal that includes a maternal pulse component corresponding to the maternal pulse as learning data and output the result.

[0014] The maternal pulse component determination device may further include a determination device side communication unit that notifies the fetal heart rate measurement device that transmitted the target Doppler signal when the maternal pulse component determination unit determines that the target Doppler signal contains the maternal pulse component, and the fetal heart rate measurement device may further include a notification unit that notifies a user that the target Doppler signal contains the maternal pulse component in response to the notification from the maternal pulse component determination device.

[0015] The fetal heart rate measurement program of this embodiment is a fetal heart rate measurement program that operates a computer as a fetal heart rate measuring device that measures the heart rate of the fetus based on a Doppler signal that represents the difference frequency between the frequency of an ultrasound transmitted toward the fetal heart and the frequency of a reflected wave of the ultrasound, and is characterized in that the computer is operated as a maternal pulse component determination unit that determines whether or not the target Doppler signal contains the maternal pulse component based on output data of a learning model that is trained to use, as learning data, a feature representing a Doppler signal that includes a maternal pulse component corresponding to the maternal pulse, and output the result of determining whether or not the Doppler signal contains the maternal pulse component, when a feature representing a target Doppler signal, which is the Doppler signal to be subjected to the determination process, is input to the learning model. Effect of the Invention

[0016] According to the fetal heart rate measuring device, fetal heart rate measuring system, or fetal heart rate measuring program disclosed in this specification, when measuring the fetal heart rate based on a Doppler signal representing the difference frequency between the frequency of an ultrasound wave transmitted toward the fetal heart and the frequency of the reflected wave of the ultrasound, it is possible to determine whether the measured value is the maternal pulse rate. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing the configuration of a fetal heart rate measuring device according to an embodiment of the present invention. [Diagram 2] 1 is a conceptual diagram showing a comparison target portion used in autocorrelation processing in a Doppler signal. FIG. [Diagram 3] FIG. 2 is a conceptual diagram showing a reference signal used in autocorrelation processing. [Figure 4] 11 is a graph showing a change over time in a correlation coefficient between a comparison portion and a reference signal. [Diagram 5] FIG. 13 is a diagram showing an example of an output waveform. [Figure 6] FIG. 2 is a diagram showing an example of a Doppler signal. [Figure 7]This is two-dimensional data showing the MFCC of the unit Doppler signal. [Figure 8] FIG. 13 is a conceptual diagram showing the processing of a learning model. [Figure 9] FIG. 13 is a diagram showing an example of a display of a fetal heart rate waveform. [Figure 10] 1 is a schematic diagram illustrating the configuration of a fetal heart rate measuring system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 is a schematic diagram of a fetal heart rate measuring device 10 according to this embodiment. The fetal heart rate measuring device 10 is a medical device installed in a medical institution such as a hospital, and has a function of measuring the fetal heart rate. The fetal heart rate measuring device 10 may be, for example, a labor monitoring device that measures the uterine contraction pressure of the mother in addition to the fetal heart rate.

[0019] The ultrasonic probe 12 transmits ultrasonic waves toward the fetal heart and receives reflected waves of the ultrasonic waves. The ultrasonic probe 12 includes a plurality of transducer elements.

[0020] The ultrasonic probe 12 transmits ultrasonic waves from a plurality of transducer elements based on a transmission signal, which is an electrical signal, from a transmitter 14, which will be described later. The plurality of transducer elements then receive reflected waves reflected from tissues, including the fetal heart, within the transmission range of the ultrasonic waves, and convert the reflected waves into received signals, which are electrical signals, for output.

[0021] The ultrasound probe 12 is a portable device and is attached to the surface of the mother's abdomen by a belt, etc. In this state, the ultrasound probe 12 transmits ultrasound waves toward the fetal heart and receives reflected waves of the ultrasound waves.

[0022] The transmitting unit 14 transmits a transmission signal to the ultrasonic probe 12 (more specifically, a plurality of transducer elements). As a result, ultrasonic waves are transmitted from each transducer element toward the fetal heart. In this embodiment, the transmitting unit 14 causes the plurality of transducer elements to transmit ultrasonic waves having a center frequency of about 1 MHz. In this embodiment, the transmitting unit 14 causes the plurality of transducer elements to transmit ultrasonic waves simultaneously, and simultaneously stops the transmission of ultrasonic waves, and repeats this. In the ultrasonic transmission stop state, the plurality of transducer elements receive reflected waves from the fetal heart, etc. Specifically, the transmitting unit 14 transmits a transmission signal intermittently to the plurality of transducer elements so that the ultrasonic transmission period and the transmission stop period (reception period) are repeated at a frequency of several KHz. In this embodiment, about 100 waves of ultrasonic waves are transmitted in one transmission period.

[0023] In this embodiment, the ultrasound transmitted to the fetal heart is used solely for measuring the fetal heart rate, and is not used to form an ultrasound image or to measure the velocities of tissues, blood flow, etc. of the subject.

[0024] The receiving unit 16 receives from the ultrasonic probe 12 (more specifically, the multiple transducer elements) a reception signal based on the reflected waves received by the multiple transducer elements during the above-mentioned reception period. As described above, the ultrasonic waves from the ultrasonic probe 12 are transmitted toward the fetal heart, but the ultrasonic waves may also be reflected from tissues other than the fetal heart. In particular, the ultrasonic waves may also be reflected from the blood flow of the mother. Therefore, the reception signal received by the receiving unit 16 may include signals based on reflected waves from not only the fetal heart but also the blood flow of the mother. The frequency of the reflected waves may have a frequency (Doppler shift frequency) that is shifted from the frequency of the transmitted ultrasonic waves (transmission frequency) due to the Doppler effect caused by the movement of each tissue including the fetal heart.

[0025] The receiving unit 16 includes an amplifier, and adds up the received signals from the multiple transducer elements and amplifies the sum in the amplifier. The receiving unit 16 outputs the amplified received signal to the Doppler signal forming unit 18.

[0026] The Doppler signal forming unit 18 includes a mixer. The mixer multiplies the received signal received from the receiving unit 16 by a reference signal having the same frequency f0 as the transmission frequency. As a result, the Doppler shift frequency f d (in other words, the difference frequency with the transmission frequency), and d A signal having a frequency of

[0027] The Doppler signal forming unit 18 also includes a low-pass filter. The low-pass filter filters out the high frequency component 2f0+f d This removes the signal at the Doppler shift frequency f d The signal having the Doppler shift frequency f d is generally within the audible frequency range (20Hz to 20kHz).

[0028] Furthermore, the Doppler signal forming unit 18 includes an AD converter. The AD converter converts the Doppler shift frequency f d In this embodiment, the sampling frequency of the digital conversion is about 2 kHz.

[0029] The Doppler shift frequency f obtained by the Doppler signal forming unit 18 d The signal having the above expression is the Doppler signal in this specification. The Doppler signal can be expressed as a waveform in a coordinate space defined by the horizontal axis representing time and the vertical axis representing the signal strength of the reflected wave. When the received signal received by the receiving unit 16 includes a signal based on the reflected wave from the fetal heart, the Doppler signal includes a fetal heartbeat component corresponding to the movement of the fetal heart, whereas when the received signal may include a signal based on the reflected wave from the maternal blood flow, the Doppler signal includes a maternal pulse component corresponding to the fluctuation of the maternal blood flow.

[0030] The heart rate measurement unit 20 executes a measurement process for measuring the fetal heart rate based on the Doppler signal formed by the Doppler signal formation unit 18. Specifically, the heart rate measurement unit 20 executes a measurement process for measuring the fetal heart rate based on the periodicity of the Doppler signal. Hereinafter, a measurement process using autocorrelation processing on the Doppler signal will be described as a measurement process for measuring the fetal heart rate, but the heart rate measurement unit 20 may execute a measurement process by other processes.

[0031] FIG. 2 is a conceptual diagram showing a comparison portion CP in a Doppler signal DS used in autocorrelation processing. FIG. 3 is a conceptual diagram showing a reference signal RDS used in autocorrelation processing. The heart rate measurement unit 20 calculates a correlation coefficient (hereinafter, may be simply referred to as a "correlation coefficient") between the reference signal RDS and a comparison portion CP, which is a portion of the Doppler signal DS having the same time length as the reference signal RDS. As will be described later, the reference signal RDS may be updated, but an initial reference signal RDS indicating a fetal heartbeat component is prepared in advance. When the reference signal RDS indicates a fetal heartbeat component, the reference signal RDS becomes a signal indicating the movement of the fetal heart wall or heart valve.

[0032] The heart rate measurement unit 20 repeatedly calculates the correlation coefficient while shifting the comparison portion CP little by little in the time direction (for example, by the time equivalent to one sample at the sampling frequency of the AD converter of the Doppler signal formation unit 18). By calculating the correlation coefficient while shifting the comparison portion CP in the time direction, the change in the correlation coefficient over time is calculated.

[0033] FIG. 4 is a graph showing the change in correlation coefficient over time. When the reference signal RDS indicates a fetal heartbeat component, the timing at which the correlation coefficient becomes large (for example, the timing at which it reaches a maximum value) can be said to indicate the timing at which the fetal heart wall or heart valve moves in the same way as the reference signal RDS. From this, it can be said that the period of the time change in the correlation coefficient represents the fetal heartbeat. Therefore, the heart rate measurement unit 20 can measure the fetal heart rate based on the period of the time change in the correlation coefficient. For example, the time t between the maximum values ​​of the correlation coefficient can be said to represent the time between one heartbeat of the fetus, so the heart rate measurement unit 20 obtains the fetal heartbeat per second by calculating the reciprocal of the time t.

[0034] In the above-mentioned autocorrelation process, the reference signal RDS is updated. Specifically, when the correlation coefficient satisfies a predetermined condition (for example, when it exceeds a predetermined threshold value or when the correlation coefficient is a maximum value), the comparison target portion CP corresponding to the correlation coefficient is set as a new reference signal RDS. By updating the reference signal RDS, even if the signal waveform of the Doppler signal representing the fetal heart rate component gradually changes, it is possible to suppress a decrease in the calculation accuracy of the fetal heart rate.

[0035] The heart rate measuring section 20 measures the fetal heart rate over time by the above-mentioned measurement process based on the Doppler signals successively formed based on the reception signals successively received by the ultrasonic probe 12 .

[0036] When the Doppler signal includes a maternal pulse component, the maternal pulse rate may be measured by the measurement process. Here, in this specification, the Doppler signal including the maternal pulse component includes not only a Doppler signal that is entirely composed of the maternal pulse component, but also a Doppler signal that includes a fetal heartbeat component but cannot read the fetal heartbeat component when viewed as a waveform, such as when the fetal heartbeat component is buried in the maternal pulse component. In other words, the Doppler signal including the maternal pulse component is a Doppler signal in which the maternal pulse component is dominant. On the other hand, the Doppler signal not including the maternal pulse component includes not only a Doppler signal that does not include the maternal pulse component at all, but also a Doppler signal that includes the maternal pulse component but in which the fetal heartbeat component can be sufficiently read when viewed as a waveform. In other words, the Doppler signal not including the maternal pulse component is a Doppler signal in which the fetal heartbeat component is dominant.

[0037] In particular, when performing measurement processing using autocorrelation processing, if there is a portion in the Doppler signal that contains a maternal pulse component, the heart rate measurement unit 20 may continue to measure the maternal pulse rate instead of the fetal heart rate for a certain period of time. For example, if the correlation coefficient between the comparison portion CP that contains the maternal pulse component and the reference signal RDS happens to satisfy a predetermined condition, the reference signal RDS will be updated to one that contains the maternal pulse component. Thereafter, the heart rate measurement unit 20 will calculate the correlation coefficient between the reference signal RDS that contains the maternal pulse component and the comparison portion CP, and calculate the period of time change of the correlation coefficient. This means that the maternal pulse rate is being calculated, not the fetal heart rate.

[0038] In this way, if the Doppler signal contains a maternal pulse component, the measurement process will measure the maternal pulse rate instead of the fetal heart rate. Therefore, as will be described in detail later, in this embodiment, the maternal pulse component determination unit 32 determines whether the Doppler signal contains a maternal pulse component, thereby determining whether the measured value is the fetal heart rate or the maternal pulse rate.

[0039] The waveform forming unit 22 forms an output waveform representing the time change of the fetal heart rate or maternal pulse rate based on the fetal heart rate or maternal pulse rate measured over time by the heart rate measuring unit 20. Fig. 5 is a diagram showing an example of the output waveform. In the example of Fig. 5, the horizontal axis represents time, and the vertical axis represents the fetal heart rate or maternal pulse rate.

[0040] The output control unit 24 causes the display 26 to display the fetal heart rate or maternal pulse rate measured by the heart rate measurement unit 20 and the output waveform formed by the waveform formation unit 22. The output control unit 24 causes the display 26 to display the fetal heart rate or maternal pulse rate as a numerical value, such as beats per minute, for example. The output control unit 24 may also output the fetal heart rate or maternal pulse rate as a sound from a speaker (not shown) in addition to or instead of displaying it on the display 26. For example, a heart sound prepared in advance may be output from the speaker in time with the fetal heart rate.

[0041] The display 26 includes, for example, a liquid crystal display. Various screens are displayed on the display 26 according to the control from the output control unit 24.

[0042] The memory 28 includes a non-volatile memory such as an eMMC (embedded multi media card) or a ROM (read only memory), and a volatile memory such as a RAM (random access memory). A fetal heart rate measuring program for operating each part of the fetal heart rate measuring device 10 is stored in the non-volatile memory. The fetal heart rate measuring program can also be stored in a computer-readable non-transitory storage medium such as a USB (universal serial bus) memory or a CD-ROM. The fetal heart rate measuring device 10 can read and execute the fetal heart rate measuring program from such a storage medium.

[0043] 1, the memory 28 (specifically, a non-volatile memory) stores a learning model 30. The learning model 30 is not limited to this, but may be, for example, an image recognition model such as a Convolutional Neural Network (CNN) or a natural language processing model such as a Transformer.

[0044] The learning model 30 is trained to determine whether or not the Doppler signal contains a maternal pulse component by using a feature quantity representing the Doppler signal including the maternal pulse component as training data, and to output the result. In this embodiment, a training process for training the learning model 30 is executed in a training processing device that is a device other than the fetal heart rate measurement device 10. Then, the training model 30 trained in the training processing device is stored in the memory 28. However, the fetal heart rate measurement device 10 may be provided with a training processing unit that executes the training process described below, that is, the fetal heart rate measurement device 10 may be the training processing device, and the training process may be performed by the fetal heart rate measurement device 10. A training method for the learning model 30 will be described in detail below.

[0045] First, previously acquired Doppler signals are stored in a Doppler signal database accessible from the learning processing device. Then, a learning processor who performs the learning process extracts a portion of the Doppler signals stored in the Doppler signal database that includes a maternal pulse component.

[0046] 6 is a diagram showing a Doppler signal DS including a maternal pulse component. A unit Doppler signal DSU of a predetermined time length is cut out from the Doppler signal DS including the maternal pulse component. The cutting out of the unit Doppler signal DSU may also be performed by a learning processor. Since the maternal pulse rate may vary, the time length of the unit Doppler signal DSU is set to a time that can include one heartbeat even if the maternal pulse rate has dropped significantly. In this embodiment, the time length of the unit Doppler signal DSU is set to 3 seconds.

[0047] A plurality of unit Doppler signals DSU are extracted from a Doppler signal DS including a maternal pulse component. As shown in Fig. 6, it is preferable to extract the unit Doppler signals DSU so that there is an overlap between the previous unit Doppler signal DSU and the next unit Doppler signal DSU. This makes it possible to extract more unit Doppler signals DSU from the Doppler signal DS (this makes it possible to obtain more learning data, as will be described in detail later).

[0048] The feature quantity representing the unit Doppler signal DSU becomes the learning data for training the learning model 30. The feature quantity representing the unit Doppler signal DSU may be the unit Doppler signal DSU itself, but in this embodiment, as described below, considering that the Doppler signal DS is within the audible frequency band, in order to have the learning model 30 execute a process in which a human listens to the Doppler signal DS as sound and judges whether or not the Doppler signal DS contains a maternal pulse component, the acoustic feature quantity when the unit Doppler signal DSU is viewed as a sound signal is used as the feature quantity of the unit Doppler signal DSU (i.e., the learning data for training the learning model 30).

[0049] Specifically, in this embodiment, two-dimensional data in which the unit Doppler signal DSU is expressed by MFCC (Mel Frequency Cepstral Coefficient) is used as the acoustic feature of the unit Doppler signal DSU. Since MFCC is a known technology, detailed description is omitted, but below, a process of obtaining MFCC from the unit Doppler signal DSU will be briefly described.

[0050] First, the processor of the learning processing device performs a Fourier transform on the unit Doppler signal DSU to obtain a frequency spectrum of the unit Doppler signal DSU. The processor of the learning processing device also performs a Mel filter bank on the obtained frequency spectrum to convert the frequency of the unit Doppler signal DSU into a Mel scale (Mel frequency) and obtain a Mel frequency spectrum in which the frequency of the unit Doppler signal DSU is converted into a Mel scale (Mel frequency) and the resolution is increased as the frequency component decreases and decreased as the frequency component increases. Here, the Mel scale is a frequency scale that takes into account human perception that sounds near the lower limit of the audible frequency band sound higher and sounds near the upper limit sound lower. Furthermore, the processor of the learning processing device obtains a logarithmic Mel frequency spectrum by taking the logarithm of the Mel frequency spectrum.

[0051] Next, the processor of the learning processing device performs DCT (Discrete Cosine Transform) on the logarithmic Mel-frequency spectrum. The signal obtained by performing DCT on the logarithmic Mel-frequency spectrum is called a (logarithmic) Mel-frequency cepstrum.

[0052] Finally, the processor of the learning processing device extracts a predetermined number (for example, 12) of signal components on the lower-order side of the obtained Mel-frequency cepstrum. Then, the extracted signal components are normalized to obtain MFCCs.

[0053] Figure 7 is two-dimensional data showing the MFCCs of the unit Doppler signal DSU. In the two-dimensional data shown in Figure 7, the horizontal axis represents time and the vertical axis represents frequency (Mel scale). In the two-dimensional map of time and frequency, the values ​​of the MFCCs are (originally) represented by colors.

[0054] The processor of the learning processing device inputs the feature amount (MFCC in this embodiment) of the unit Doppler signal DSU as learning data to the learning model 30. When two-dimensional data indicating the MFCC of the unit Doppler signal DSU is used as learning data, the learning model 30 is a CNN, and the two-dimensional data may be input to the learning model 30 as two-dimensional image data. The learning model 30 predicts whether or not the unit Doppler signal DSU contains a maternal pulse component based on the feature amount of the input unit Doppler signal DSU, and outputs the prediction result. The processor of the learning processing device adjusts the parameters of the learning model 30 so that the difference between the prediction result and the teacher data indicating that the unit Doppler signal DSU contains a maternal pulse component becomes small. By repeating such processing, the learning model 30 that has been sufficiently learned becomes able to predict with high accuracy whether or not the input unit Doppler signal DSU contains a maternal pulse component and output it.

[0055] The learning model 30 may be trained to determine whether or not the Doppler signal contains a maternal pulse component by using learning data further including a feature amount representing a Doppler signal in which the fetal heartbeat component is dominant, and output the result. In this case, a learning processor who performs the learning process extracts a part in which the fetal heartbeat component is dominant from the Doppler signal database, together with a part including the maternal pulse component. Then, a plurality of unit Doppler signals DSU are also extracted from the Doppler signal DS in which the fetal heartbeat component is dominant, and a feature amount (e.g., MFCC) of each unit Doppler signal DSU is acquired. In this case, a label indicating that the unit Doppler signal DSU is a unit Doppler signal DSU containing a maternal pulse component is attached to the feature amount of the unit Doppler signal DSU extracted from the Doppler signal DS in which the fetal heartbeat component is dominant, as the learning data, and a label indicating that the unit Doppler signal DSU is a unit Doppler signal DSU in which the fetal heartbeat component is dominant is attached to the feature amount of the unit Doppler signal DSU extracted from the Doppler signal DS in which the fetal heartbeat component is dominant, as the learning data. Such a label is used as teacher data. The learning model 30 can improve the prediction accuracy of the trained learning model 30 or the learning efficiency of the learning model 30 by training the learning model 30 using training data including not only features of a unit Doppler signal DSU that includes a maternal pulse component, but also features of a unit Doppler signal DSU in which the fetal heart rate component is dominant.

[0056] Returning to FIG. 1, the maternal pulse component determination unit 32 determines whether or not a maternal pulse component is included in the Doppler signal to be subjected to the determination process (referred to as a target Doppler signal in this specification) formed by the Doppler signal formation unit 18. Specifically, the maternal pulse component determination unit 32 cuts out the target Doppler signal at predetermined time intervals (for example, at the same time as the unit Doppler signal DSU (see FIG. 6) that is the basis of the learning data). In this specification, the signal cut out from the target Doppler signal is referred to as a unit target Doppler signal. Then, as shown in FIG. 8, the maternal pulse component determination unit 32 inputs the feature amount of the cut-out unit target Doppler signal to the trained learning model 30, and determines whether or not the unit target Doppler signal includes a maternal pulse component based on the output data of the learning model 30.

[0057] The maternal pulse component determination unit 32 inputs to the learning model 30 the feature amount of the unit object Doppler signal corresponding to the feature amount of the unit Doppler signal DSU used as learning data for the learning model 30. For example, when the feature amount (e.g., MFCC) of the unit Doppler signal DSU viewed as an audio signal is used as learning data for the learning model 30, the maternal pulse component determination unit 32 inputs to the learned learning model 30 the feature amount (e.g., MFCC) of the unit object Doppler signal viewed as an audio signal.

[0058] The maternal pulse component determination unit 32 successively extracts the target unit Doppler signals from the target Doppler signal and inputs them sequentially to the learning model 30. In this way, the maternal pulse component determination unit 32 determines over time whether or not the Doppler signal contains a maternal pulse component.

[0059] The results of the determination by the maternal pulse component determiner 32 are sequentially passed to the output controller 24 .

[0060] When the maternal pulse component determination unit 32 determines that the target Doppler signal contains a maternal pulse component, the output control unit 24, which serves as a notification unit, notifies a user of the fetal heart rate measurement device 10 (e.g., a doctor or technician) that the target Doppler signal contains a maternal pulse component.

[0061] There may be various methods for the output control unit 24 to notify the user that the target Doppler signal contains a maternal pulse component. For example, the output control unit 24 causes the display 26 to display the output waveform 40 formed by the waveform forming unit 22 in a manner that allows a distinction between a waveform portion formed based on the target Doppler signal containing a maternal pulse component (hereinafter referred to as a maternal pulse waveform portion) and a waveform portion formed based on the target Doppler signal not containing a maternal pulse component (hereinafter referred to as a fetal heartbeat waveform portion).

[0062] Specifically, as shown in Fig. 9, the output control unit 24 may display an indicator 42 together with the output waveform 40. The indicator 42 has a bar shape extending in the time direction (horizontal axis direction in the example of Fig. 9), and displays the period of the maternal pulse waveform portion and the period of the fetal heart rate waveform portion in a manner that allows them to be distinguished from each other. For example, in the example of Fig. 9, the period of the maternal pulse waveform portion is displayed by diagonal lines in the indicator 42, and the period of the fetal heart rate waveform portion is displayed by shading.

[0063] In addition, instead of or in addition to the indicator 42, the output control unit 24 may display the output waveform 40 itself in a manner that allows the maternal pulse waveform portion and the fetal heart rate waveform portion to be distinguished from each other (for example, by displaying them in different colors).

[0064] Furthermore, the output control unit 24 may output an alert at the timing when a target Doppler signal containing a maternal pulse component is detected (or at the timing when a waveform portion formed based on a target Doppler signal containing a maternal pulse component is displayed on the display 26) instead of or in addition to the indicator 42. The alert can be issued, for example, by displaying on the display 26, by illuminating a light-emitting unit (e.g., an LED (Light-Emitting Diode) or the like) provided in the fetal heart rate measuring device 10, or by outputting a sound from a speaker provided in the fetal heart rate measuring device 10.

[0065] There may be cases where the target Doppler signal is determined to include a maternal pulse component for only a short period of time. In such cases, the measurement target immediately returns to the fetal heart rate, so there is no practical problem. Therefore, the output control unit 24 may be configured to output an alert when the target Doppler signal is determined to include a maternal pulse component for a predetermined consecutive period of time.

[0066] The output control unit 24 may display a uterine contraction pressure waveform 44, which indicates the time change in the mother's uterine contraction pressure, on the display 26 together with the output waveform 40. The uterine contraction pressure is also measured by the fetal heart rate measuring device 10. For example, a pressure sensor may be provided on the ultrasound probe 12 attached to the surface of the mother's abdomen, and the uterine contraction pressure may be measured based on the pressure detected by the pressure sensor.

[0067] The fetal heart rate measuring device 10 according to the present embodiment has been outlined above. Among the above-mentioned components of the fetal heart rate measuring device 10, the transmitting section 14, the receiving section 16, the Doppler signal forming section 18, the heart rate measuring section 20, the waveform forming section 22, the output control section 24, and the maternal pulse component determining section 32 are configured by a processor. The processor includes at least one of a general-purpose processing device (e.g., a CPU (Central Processing Unit)) and a dedicated processing device (e.g., a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a programmable logic device). The processor may not be a single processing device, but may be configured by the cooperation of multiple processing devices located at physically separate locations. Furthermore, each of the above-mentioned components may be realized by the cooperation of hardware such as a processor and software.

[0068] According to the fetal heart rate measuring device 10, the maternal pulse component determining unit 32 can determine that the target Doppler signal contains a maternal pulse component. As a result, even if the heart rate measuring unit 20 measures the maternal pulse rate instead of the fetal heart rate, the user can easily understand this. If the user can understand that the maternal pulse rate is being measured, the user is prevented from erroneously determining that the fetal heart rate is decreasing, for example. Furthermore, although the maternal pulse rate is normally smaller than the fetal heart rate, if the user can understand that the maternal pulse rate is being measured, if the maternal pulse rate increases to a level equivalent to the fetal heart rate, the user can detect this in the fetal heart rate measuring device 10. Furthermore, if the maternal pulse rate is measured due to the attachment state of the ultrasound probe 12 attached to the abdominal surface of the mother, the user can check the attachment state of the ultrasound probe 12 if he or she can understand that the maternal pulse rate is being measured.

[0069] Fig. 10 is a schematic diagram of a fetal heart rate measuring system 50 according to this embodiment. In the fetal heart rate measuring device 10 shown in Fig. 1, the process of forming the target Doppler signal, the process of measuring the fetal heart rate, and the process of determining whether or not the target Doppler signal contains a maternal pulse component are performed in one device, but the process of forming the target Doppler signal, the process of measuring the fetal heart rate, and the process of determining whether or not the target Doppler signal contains a maternal pulse component may be performed in different devices.

[0070] 10 includes a fetal heart rate measuring device 52 and a maternal pulse component determining device 54. The fetal heart rate measuring device 52 and the maternal pulse component determining device 54 are communicatively connected to each other via a communication line 56 such as a LAN (Local Area Network) or a WAN (Wide Area Network). The fetal heart rate measuring system 50 may include a plurality of fetal heart rate measuring devices 52. That is, the maternal pulse component determining device 54 may be communicatively connected to a plurality of fetal heart rate measuring devices 52.

[0071] The fetal heart rate measuring device 52 is installed in an examination room or a delivery room in a hospital, and the maternal pulse component determining device 54 is installed in a nurse center or a central control room in the hospital, which is different from the examination room or the delivery room. Alternatively, the fetal heart rate measuring device 52 may be installed in, for example, the pregnant woman's home, and the maternal pulse component determining device 54 may be a server provided remotely from the pregnant woman's home. In this case, the function performed by the maternal pulse component determining device 54 may be provided by a cloud service.

[0072] The fetal heart rate measuring device 52 has an ultrasonic probe 12, a transmitting unit 14, a receiving unit 16, a Doppler signal forming unit 18, a heart rate measuring unit 20, a waveform forming unit 22, an output control unit 24, a display 26, and a communication unit 60. The configurations and functions of the ultrasonic probe 12, the transmitting unit 14, the receiving unit 16, the Doppler signal forming unit 18, the heart rate measuring unit 20, the waveform forming unit 22, the output control unit 24, and the display 26 of the fetal heart rate measuring device 52 are similar to those of the ultrasonic probe 12, the transmitting unit 14, the receiving unit 16, the Doppler signal forming unit 18, the heart rate measuring unit 20, the waveform forming unit 22, the output control unit 24, and the display 26 in Fig. 1, and therefore a description thereof will be omitted.

[0073] The communication unit 60 is composed of, for example, a network card and has a function of communicating with the maternal pulse component determination device 54 via the communication line 56. The communication unit 60, which serves as a measurement device side communication unit, transmits the target Doppler signal formed by the Doppler signal forming unit 18 to the maternal pulse component determination device 54.

[0074] Maternal pulse component determination device 54 has maternal pulse component determination section 32, memory 62 in which learning model 30 is stored, display 64, and communication section 66. The configurations and functions of maternal pulse component determination section 32 and learning model 30 of maternal pulse component determination device 54 are similar to those of maternal pulse component determination section 32 and learning model 30 in Fig. 1, and therefore description thereof will be omitted.

[0075] The memory 62 includes a non-volatile memory such as a hard disk drive (HDD), eMMC, or ROM, and a volatile memory such as a random access memory (RAM). The display 64 includes, for example, a liquid crystal display. Various screens are displayed on the display 64 under the control of a processor (not shown) of the maternal pulse component determination device 54.

[0076] The maternal pulse component determination unit 32 of the maternal pulse component determination device 54 inputs features representing each target Doppler signal transmitted from each fetal heart rate measurement device 52 included in the fetal heart rate measurement system 50 into the learning model 30, and determines whether or not each target Doppler signal contains a maternal pulse component based on the output data of the learning model 30.

[0077] The determination process by the maternal pulse component determination unit 32 using the learning model 30 requires a large amount of calculation. Therefore, the processor of the device having the maternal pulse component determination unit 32 and the learning model 30 is required to have high calculation power. In the fetal heart rate measurement system 50, the maternal pulse component determination unit 32 and the learning model 30 are provided in the maternal pulse component determination device 54, and are not provided in each fetal heart rate measurement device 52. Therefore, according to the fetal heart rate measurement system 50, it is sufficient to provide only the maternal pulse component determination device 54 with a processor having high calculation power, and it is not necessary to provide a processor having high calculation power for each fetal heart rate measurement device 52. As a result, it is possible to determine whether or not each target Doppler signal formed by each fetal heart rate measurement device 52 contains a maternal pulse component without increasing the cost of each fetal heart rate measurement device 52.

[0078] In addition, if the judgment results of the maternal pulse component judgment unit 32 for each target Doppler signal formed by each fetal heart rate measuring device 52 are displayed on the display 64, the user can consolidate and check the judgment results for each target Doppler signal from each fetal heart rate measuring device 52 on the display 64.

[0079] The communication unit 66 is composed of, for example, a network card and has a function of communicating with each fetal heart rate measuring device 52 via the communication line 56. When the maternal pulse component determining unit 32 determines that the target Doppler signal contains a maternal pulse component, the communication unit 66 as the determination device side communication unit may notify the fetal heart rate measuring device 52 that transmitted the target Doppler signal. When the output control unit 24 as the notification unit of the fetal heart rate measuring device 52 receives a notification from the maternal pulse component determining device 54, it notifies the user that the target Doppler signal formed by the own device contains a maternal pulse component.

[0080] In this way, the process of forming the object Doppler signal may be performed by fetal heart rate measuring device 52, the process of determining whether or not the object Doppler signal contains a maternal pulse component may be performed by maternal pulse component determining device 54, and a notification to the user when the object Doppler signal contains a maternal pulse component may be performed by fetal heart rate measuring device 52. In this way, the user can check whether or not the object Doppler signal contains a maternal pulse component by using fetal heart rate measuring device 52, without increasing the cost of fetal heart rate measuring device 52.

[0081] The fetal heart rate measuring device, fetal heart rate measuring system, and fetal heart rate measuring program of this embodiment have been described above, but the fetal heart rate measuring device, fetal heart rate measuring system, and fetal heart rate measuring program of this embodiment are not limited to the above embodiment, and various modifications are possible without departing from the spirit thereof. [Explanation of symbols]

[0082] 10,52 Fetal heart rate measuring device, 12 Ultrasound probe, 14 Transmitter, 16 Receiver, 18 Doppler signal forming section, 20 Heart rate measuring section, 22 Waveform forming section, 24 Output control section, 26,64 Display, 28,62 Memory, 30 Learning model, 32 Maternal pulse component determining section, 40 Output waveform, 42 Indicator, 44 Uterine contraction pressure waveform, 50 Fetal heart rate measuring system, 54 Maternal pulse component determining device, 56 Communication line, 60,66 Communication section.

Claims

1. A fetal heart rate measuring device that measures a heart rate of a fetus based on a Doppler signal that represents a difference frequency between a frequency of an ultrasound wave transmitted to a fetal heart and a frequency of a reflected wave of the ultrasound, comprising: a maternal pulse component determination unit that determines whether or not the target Doppler signal includes the maternal pulse component based on output data of a learning model that is trained to determine whether or not the target Doppler signal includes the maternal pulse component by using, as learning data, a feature value that represents a Doppler signal that includes a maternal pulse component corresponding to a maternal pulse among the Doppler signals and output the determined result; and A fetal heart rate measuring device comprising:

2. the learning model is trained using the learning data further including a feature representing a Doppler signal in which a fetal heartbeat component corresponding to a fetal heartbeat is dominant among the Doppler signals; 2. The fetal heart rate measuring device according to claim 1 .

3. the feature representing the Doppler signal is an acoustic feature when the Doppler signal is viewed as a sound signal, The feature representing the target Doppler signal is an acoustic feature when the target Doppler signal is viewed as a sound signal.

2. The fetal heart rate measuring device according to claim 1 .

4. a notification unit that notifies a user that the object Doppler signal contains the maternal pulse component when the maternal pulse component determination unit determines that the object Doppler signal contains the maternal pulse component; 2. The fetal heart rate measuring device according to claim 1, further comprising:

5. a waveform forming unit that forms an output waveform representing a time change in the fetal heart rate or the maternal pulse rate measured based on the object Doppler signal; Further equipped with the notification unit causes the output waveform to be displayed on a display in a manner that enables a waveform portion formed based on the target Doppler signal including the maternal pulse component and a waveform portion formed based on the target Doppler signal not including the maternal pulse component to be distinguished.

5. The fetal heart rate measuring device according to claim 4.

6. a fetal heart rate measuring device for measuring a heart rate of the fetus based on a Doppler signal representing a difference frequency between a frequency of an ultrasound wave transmitted to the fetal heart and a frequency of a reflected wave of the ultrasound; A maternal pulse component determining device; A fetal heart rate measuring system comprising: Each of the fetal heart rate measuring devices is a measurement device side communication unit that transmits a target Doppler signal, which is a Doppler signal to be subjected to determination processing, to the maternal pulse component determination device; Equipped with The maternal pulse component determining device comprises: a maternal pulse component determination unit that determines whether or not each of the target Doppler signals includes the maternal pulse component based on output data of a learning model that is trained to determine whether or not the Doppler signal includes the maternal pulse component by using, as learning data, feature values ​​that represent a Doppler signal that includes a maternal pulse component corresponding to a maternal pulse among the Doppler signals; Equipped with A fetal heart rate measuring system comprising:

7. The maternal pulse component determining device comprises: a determination device side communication unit that notifies the fetal heart rate measurement device that transmitted the target Doppler signal when the maternal pulse component determination unit determines that the target Doppler signal contains the maternal pulse component; Further equipped with The fetal heart rate measuring device includes: a notification unit that notifies a user that the target Doppler signal contains the maternal pulse component in response to a notification from the maternal pulse component determination device; Further comprising:

7. The fetal heart rate measuring system according to claim 6.

8. A fetal heart rate measuring program for operating a computer as a fetal heart rate measuring device for measuring a heart rate of a fetus based on a Doppler signal representing a difference frequency between a frequency of an ultrasound wave transmitted to a fetal heart and a frequency of a reflected wave of the ultrasound, the program comprising: The computer, a maternal pulse component determination unit that determines whether or not the target Doppler signal includes the maternal pulse component based on output data of a learning model that is trained to determine whether or not the target Doppler signal includes the maternal pulse component by using, as learning data, a feature value that represents a Doppler signal that includes a maternal pulse component corresponding to a maternal pulse among the Doppler signals and output the determined result; and A fetal heart rate measuring program comprising:

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