JP2025030338A - Ultrasound diagnostic device, medical information processing device, and hardness calculation program - Google Patents

Abstract

The present invention aims to improve the accuracy of measuring the stiffness of biological tissue by calculating the stiffness of biological tissue using the pressure displacement amount rather than the measured displacement amount.
[Solution] According to an embodiment, an ultrasound diagnostic device that acquires an applied pressure to a subject from a pressure sensor attached to an ultrasound probe includes an image generating unit, a displacement amount calculating unit, and a stiffness calculating unit. The image generating unit generates a plurality of first images in a time series including the biological tissue at an applied pressure less than a pressure threshold, and generates a plurality of second images in a time series including the biological tissue at an applied pressure equal to or greater than the pressure threshold. The displacement amount calculating unit calculates the amount of displacement of the biological tissue between each of the second images of the plurality of second images and the plurality of first images. The stiffness calculating unit calculates the stiffness of the biological tissue based on the amount of displacement corresponding to each second image and the applied pressure equal to or greater than the pressure threshold corresponding to each second image.
[Selected Figure] Figure 1

Description

The embodiments disclosed in this specification and the drawings relate to an ultrasound diagnostic device, a medical information processing device, and a hardness calculation program.

In the medical field, ultrasound diagnostic devices are used that are equipped with an ultrasound probe and an ultrasound image processing device, and that use ultrasound generated by multiple transducers (or piezoelectric transducers) in the ultrasound probe to image the inside of a subject. The ultrasound image processing device transmits ultrasound from the ultrasound probe into the subject, generates echo signals based on the reflected waves, and obtains the desired ultrasound image through image processing.

There is a technology in which ultrasonic images are acquired by applying pressure to a subject, either manually by an operator or automatically by a robot arm, and an elasticity image is generated that shows the hardness of biological tissue based on the amount of displacement (hereinafter referred to as the "measured displacement") based on multiple ultrasonic images with different phases and the applied pressure. This technology involves providing a pressure sensor behind the transducer element of an ultrasonic probe, determining the pressure applied to the ultrasonic probe by applying pressure to the subject, determining the Young's modulus, and displaying an elasticity image. The measured displacement used here includes noise components caused by periodic movements such as pulsation and respiratory fluctuation, and the measured displacement is not the displacement excluding the noise components (hereinafter referred to as the "pressure displacement").

JP 2018-20140 A

One of the problems that the embodiments disclosed in this specification and the drawings attempt to solve is to improve the accuracy of measuring the stiffness of biological tissue by calculating the stiffness of biological tissue using the pressure displacement amount rather than the measured displacement amount. However, the problems that the embodiments disclosed in this specification and the drawings attempt to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in each embodiment described below can also be positioned as other problems.

An ultrasound diagnostic device according to an embodiment, which acquires the pressure applied to a subject from a pressure sensor attached to an ultrasound probe, includes an image generator, a displacement calculator, and a stiffness calculator. The image generator generates a plurality of first images in a time series including the biological tissue at an applied pressure less than a pressure threshold, and generates a plurality of second images in a time series including the biological tissue at an applied pressure equal to or greater than the pressure threshold. The displacement calculator calculates the amount of displacement of the biological tissue between each of the second images of the plurality of second images and the plurality of first images. The stiffness calculator calculates the stiffness of the biological tissue based on the amount of displacement corresponding to each second image and the applied pressure equal to or greater than the pressure threshold corresponding to each second image.

1 is a schematic diagram showing an example of the configuration of an ultrasound diagnostic apparatus according to a first embodiment. FIG. 2 is a flowchart showing a first operation example of the ultrasound diagnostic apparatus according to the first embodiment. 4A and 4B are diagrams showing the relationship between a plurality of images and electrocardiogram waveforms in a first operation example of the ultrasound diagnostic apparatus according to the first embodiment. 4A and 4B are views showing a relationship between a first image and a second image in a first operation example of the ultrasound diagnostic apparatus according to the first embodiment. FIG. 4 is a diagram showing an example of a hysteresis loop in a first operation example of the ultrasound diagnostic apparatus according to the first embodiment. FIG. 4 is a flowchart showing a second operation example of the ultrasound diagnostic apparatus according to the first embodiment. FIG. 11 is a flowchart showing a third operation example of the ultrasound diagnostic apparatus according to the first embodiment. 13A and 13B are diagrams showing the relationship between a plurality of images and electrocardiogram waveforms in a third operation example of the ultrasound diagnostic apparatus according to the first embodiment. 13A and 13B are views showing the relationship between a first image and a second image in a third operation example of the ultrasound diagnostic apparatus according to the first embodiment. FIG. 11 is a schematic diagram showing an example of the configuration of a medical image processing apparatus according to a second embodiment.

Below, embodiments of an ultrasound diagnostic device, a medical information processing device, and a hardness calculation program are described in detail with reference to the drawings.

First Embodiment
1 shows an ultrasonic diagnostic device 1 including an ultrasonic image processing device 10 according to a first embodiment. In addition to the ultrasonic image processing device 10, the ultrasonic diagnostic device 1 includes an ultrasonic probe 20, an input interface 30, a display 40, a pressure sensor 50, and a phase sensor 60. Note that the ultrasonic diagnostic device 1 may include at least one of the ultrasonic probe 20, the input interface 30, the display 40, the pressure sensor 50, and the phase sensor 60. In the following description, a case will be described in which the ultrasonic diagnostic device 1 includes all of the ultrasonic probe 20, the input interface 30, the display 40, the pressure sensor 50, and the phase sensor 60.

The ultrasound image processing device 10 includes an ultrasound transmission circuit 11, an ultrasound reception circuit 12, an image memory 13, a network interface 14, a processing circuit 15, and a main memory 16. The circuits 11 and 12 are configured using an application specific integrated circuit (ASIC) or the like. However, this is not limited to this case, and all or part of the functions of the circuits 11 and 12 may be realized by the processing circuit 15 executing a computer program.

The ultrasonic transmission circuit 11 and the ultrasonic reception circuit 12 control the transmission directivity and reception directivity in transmitting and receiving ultrasonic waves under the control of the processing circuit 15. Note that, although a case where both the ultrasonic transmission circuit 11 and the ultrasonic reception circuit 12 are provided in the ultrasonic image processing device 10 will be described, at least one of the ultrasonic transmission circuit 11 and the ultrasonic reception circuit 12 may be provided in the ultrasonic probe 20, or may be provided in both the ultrasonic image processing device 10 and the ultrasonic probe 20.

Although not shown, the ultrasonic transmission circuit 11 includes a pulse generation circuit, a transmission delay circuit, a pulsar circuit, etc., and supplies a drive signal to the ultrasonic transducer of the ultrasonic probe 20. The pulse generation circuit repeatedly generates a rate pulse for forming a transmission ultrasonic wave at a predetermined repetition frequency (PRF: Pulse Repetition Frequency). The transmission delay circuit provides each rate pulse generated by the pulse generation circuit with a delay time for each piezoelectric transducer required to focus the ultrasonic waves generated from the ultrasonic probe 20 into a beam and determine the transmission directivity. The transmission direction or the transmission delay time that determines the transmission direction is stored in the main memory 16 and is referenced at the time of transmission. The pulsar circuit applies a drive signal (drive pulse) to multiple ultrasonic transducers provided in the ultrasonic probe 20 at a timing based on the rate pulse. By changing the delay time provided to each rate pulse by the transmission delay circuit, the transmission direction from the piezoelectric transducer surface can be adjusted arbitrarily.

The ultrasonic receiving circuit 12 includes an amplifier circuit, an A/D (Analog to Digital) converter, an adder, etc. (not shown), and receives echo signals received by the ultrasonic transducer of the ultrasonic probe 20 and performs various processes on the echo signals to generate echo data. The amplifier circuit amplifies the echo signals for each channel and performs gain correction processing. The A/D converter A/D converts the gain-corrected echo signals and gives the digital data a delay time required to determine the reception directivity. The adder performs addition processing on the echo signals processed by the A/D converter to generate echo data. The addition processing by the adder emphasizes the reflected components from a direction corresponding to the reception directivity of the echo signal.

The image memory 13 includes, for example, a magnetic or optical recording medium, or a processor-readable recording medium such as a semiconductor memory. The image memory 13 stores multiple ultrasound images under the control of the processing circuit 15. The image memory 13 is an example of a storage unit.

The network interface 14 implements various information communication protocols according to the type of network. In accordance with these various protocols, the network interface 14 connects the ultrasound diagnostic device 1 to other devices such as an external medical image management device 70 and a medical information processing device 80. This connection can be an electrical connection via an electronic network. Here, the electronic network refers to a general information communication network that uses electrical communication technology, and includes wireless/wired hospital-based LANs (Local Area Networks) and Internet networks, as well as telephone communication line networks, optical fiber communication networks, cable communication networks, and satellite communication networks.

The network interface 14 may also implement various protocols for non-contact wireless communication. In this case, the ultrasound image processing device 10 can transmit and receive data directly to, for example, the ultrasound probe 20 without going through a network. The network interface 14 is an example of a network connection unit.

The processing circuit 15 refers to a dedicated or general-purpose CPU (Central Processing Unit), MPU (Micro Processor unit), or GPU (Graphics Processing Unit), as well as an ASIC and a programmable logic device. Examples of programmable logic devices include a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA).

The processing circuit 15 may be configured as a single circuit, or may be configured as a combination of multiple independent circuit elements. In the latter case, the main memory 16 may be provided separately for each circuit element, or a single main memory 16 may store programs corresponding to the functions of multiple circuit elements. The processing circuit 15 is an example of a processing unit.

The main memory 16 is composed of semiconductor memory elements such as RAM (random access memory) and flash memory, a hard disk, an optical disk, etc. The main memory 16 may be composed of a portable medium such as a universal serial bus (USB) memory and a digital video disk (DVD). The main memory 16 stores various processing programs (including application programs and an operating system (OS)) used in the processing circuit 15 and data required for executing the programs. The OS can also include a graphical user interface (GUI) that makes extensive use of graphics to display information to the operator on the display 40 and allows basic operations to be performed by the input interface 30. The main memory 16 is an example of a storage unit.

The ultrasonic probe 20 has multiple tiny transducers (piezoelectric elements) on the front surface, and transmits and receives ultrasonic waves to and from the area including the object to be scanned. Each transducer is an electroacoustic conversion element, and has the function of converting an electric pulse into an ultrasonic pulse during transmission, and converting a reflected wave into an electric signal (received signal) during reception. The ultrasonic probe 20 is small and lightweight, and is connected to the ultrasonic image processing device 10 via a cable (or wireless communication).

The ultrasonic probe 20 is divided into types such as linear type, convex type, and sector type depending on the scanning method. Also, the ultrasonic probe 20 is divided into types such as 1D array probes in which multiple transducers are arranged one-dimensionally (1D) in the azimuth direction (i.e., the long axis direction) and 2D array probes in which multiple transducers are arranged two-dimensionally (2D) in the azimuth direction and the elevation direction (i.e., the short axis direction) depending on the array arrangement dimension. Note that 1D array probes include probes in which a small number of transducers are arranged in the elevation direction.

When a 3D scan, i.e., a volume scan, is performed, a 2D array probe equipped with a scanning method such as a linear type, a convex type, or a sector type is used as the ultrasound probe 20. Alternatively, when a volume scan is performed, a 1D probe equipped with a scanning method such as a linear type, a convex type, or a sector type and equipped with a mechanism for mechanically oscillating in the elevation direction is used as the ultrasound probe 20. The latter probe is also called a mechanical 4D probe.

The input interface 30 includes an input device that can be operated by an operator, and an input circuit that inputs signals from the input device. The input device can be a trackball, a switch, a mouse, a keyboard, a touchpad that performs input operations by touching the operation surface, a touchscreen that combines a display screen and a touchpad, a non-contact input device that uses an optical sensor, and a voice input device. When the operator operates the input device, the input circuit generates a signal according to the operation and outputs it to the processing circuit 15. The input interface 30 is an example of an input unit.

The display 40 is configured with a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display. The display 40 displays various information according to the control of the processing circuit 15. The display 40 is an example of a display unit.

The pressure sensor 50 is attached to the ultrasound probe 20 and detects the pressure from the ultrasound probe 20 to the subject as an electrical signal. The pressure sensor 50 performs various processes, including digitalization, on the detected pressure signal and transmits it to the ultrasound image processing device 10 as pressure data. Note that the pressure sensor 50 can also be an acceleration sensor, and information related to pressure can be generated from the output signal of the acceleration sensor.

The phase sensor 60 is composed of, for example, either an electrocardiograph or a respiration sensor. The electrocardiograph as the phase sensor 60 acquires information on a specific phase (cardiac phase) of one cycle of periodically repeating beats as an electrocardiogram waveform signal (ECG: Electrocardiogram). The electrocardiograph detects the electrocardiogram waveform signal of the subject as an electrical signal. The electrocardiograph performs various processes, including digitization, on the detected electrocardiogram waveform signal and then transmits it to the ultrasound image processing device 10.

The respiratory sensor as the phase sensor 60 acquires information on a specific phase of one periodic respiration cycle as a respiratory waveform signal. The respiratory sensor acquires the subject's respiratory waveform signal as an electrical signal. For example, the respiratory sensor has a laser generator and a photoreceiver, and processes the signal of reflected light from the subject's abdominal surface to repeatedly calculate the distance between the laser generator and the subject's abdominal surface in real time based on the time from laser irradiation to reception of reflected light or the phase change of the reflected light signal, and transmits the distance as time-series data to the ultrasound image processing device 10. The respiratory sensor may be configured to attach a pressure sensor between the subject's abdomen and a band worn on the abdomen, and observe the respiratory state based on changes in pressure. Alternatively, the respiratory sensor may observe the respiratory state by placing an object with a light reflecting material on the abdomen, photographing it with a camera, and tracking the movement of the light reflecting material.

FIG. 1 also shows a medical image management device 70 and a medical information processing device 80, which are external devices of the ultrasound diagnostic device 1. The medical image management device 70 is, for example, a DICOM (Digital Imaging and Communications in Medicine) server, and is connected to devices such as the ultrasound diagnostic device 1 so as to be able to send and receive data via a network N. The medical image management device 70 manages ultrasound images generated by the ultrasound diagnostic device 1 as DICOM files.

The medical information processing device 80 is connected to devices such as the ultrasound diagnostic device 1 and the medical image management device 70 via the network N so that data can be transmitted and received. Examples of the medical information processing device 80 include a workstation that performs various image processing on the ultrasound images generated by the ultrasound diagnostic device 1, and a portable information processing terminal such as a tablet terminal. Note that the medical information processing device 80 may be an offline device that can read out the ultrasound images generated by the ultrasound diagnostic device 1 via a portable storage medium.

Next, the functions of the ultrasound image processing device 10 will be explained using FIG. 1.

The processing circuitry 15 realizes a B-mode processing function F1, a Doppler processing function F2, an image generation function F3, a displacement amount calculation function F4, a stiffness calculation function F5, and a display control function F6 by reading and executing a computer program stored in the main memory 16 or a memory within the processing circuitry 15. Below, an example will be described in which functions F1 to F6 are realized by a computer program, but all or part of functions F1 to F6 may be provided in the ultrasound image processing device 10 as functions of a circuit such as an ASIC.

The B-mode processing function F1 receives echo data from the ultrasound receiving circuit 12, and performs logarithmic amplification and envelope detection processing to generate data (two-dimensional or three-dimensional data) in which the signal strength is expressed as luminance brightness. This data is generally called B-mode data.

The B-mode processing function F1 can change the detection frequency through filter processing, thereby changing the frequency band to be visualized. By using the filter processing function of the B-mode processing function F1, it is possible to perform harmonic imaging such as contrast harmonic imaging (CHI) and tissue harmonic imaging (THI).

The Doppler processing function F2 performs frequency analysis on velocity information from the echo data from the ultrasound receiving circuit 12, and generates data (two-dimensional or three-dimensional data) that extracts moving object information such as average velocity, variance, and power for multiple points. This data is generally called Doppler data. Here, moving objects are, for example, blood flow, tissues such as the heart wall, and contrast agents.

The B-mode data generated by the B-mode processing function F1 and the Doppler data generated by the Doppler processing function F2 are ultrasound image data before the scan conversion process. On the other hand, the data generated by the display control function F6 described below is display image data after the scan conversion process. Note that the B-mode data and Doppler data are also called raw data.

The image generation function F3 generates an ultrasound image expressed in a predetermined brightness range as image data based on the reception signal received by the ultrasound probe 20. For example, the image generation function F3 generates, as an ultrasound image, a B-mode image (a first image and a second image described below) in which the intensity of the reflected wave is expressed as brightness from the two-dimensional B-mode data generated by the B-mode processing function F1. The image generation function F3 generates, as a plurality of first images, a plurality of B-mode images in a time series including biological tissues at an applied pressure less than a pressure threshold when pressure is not actively applied, and generates, as a plurality of second images, a plurality of B-mode images in a time series including biological tissues at an applied pressure equal to or greater than a pressure threshold when pressure is actively applied.

In addition, the image generation function F3 generates, as an ultrasound image, an average velocity image, a variance image, a power image, or a color Doppler image as a combination of these images, which represents the movement state information from the two-dimensional Doppler data generated by the Doppler processing function F2.

Here, the image generation function F3 generally converts (scan converts) the scan line signal sequence of the ultrasound scan into a scan line signal sequence of a video format, such as that of a television, to generate an ultrasound image. Specifically, the image generation function F3 generates an ultrasound image by performing coordinate conversion according to the ultrasound scanning form of the ultrasound probe 20. In addition to scan conversion, the image generation function F3 also performs various image processing, such as image processing (smoothing processing) that regenerates an average brightness image using multiple image frames after scan conversion, and image processing (edge enhancement processing) that uses a differential filter within the image. The image generation function F3 also combines text information of various parameters, scales, body marks, etc., with the ultrasound image.

That is, the B-mode data and Doppler data are ultrasound images before the scan conversion process, and the data generated by the image generation function F3 is an ultrasound image for display after the scan conversion process. Note that the B-mode data and Doppler data are also called raw data. The image generation function F3 generates a two-dimensional ultrasound image for display from the two-dimensional ultrasound image before the scan conversion process.

The displacement amount calculation function F4 includes a function for calculating the amount of displacement of biological tissue between each second image generated by the image generation function F3 and the multiple first images generated by the image generation function F3 as a pressure displacement amount (a displacement amount obtained by removing noise components from the measured displacement amount). For example, the displacement amount calculation function F4 calculates the pressure displacement amount by a block matching method or the like. The block matching method divides an image into blocks, for example, each consisting of N×N pixels, searches the first image for a block that is most similar to a block of interest in the second image, and performs predictive coding by referring to this block.

The stiffness calculation function F5 includes a function for calculating the stiffness of biological tissue based on the pressure displacement amount corresponding to each second image calculated by the displacement amount calculation function F4 and the applied pressure equal to or greater than the pressure threshold corresponding to each second image.

The display control function F6 includes a function for displaying multiple ultrasound images on the display 40 and a function for displaying the stiffness of the biological tissue calculated by the stiffness calculation function F5 on the display 40.

(First operation example)
Next, a first operation example of the ultrasonic diagnostic device 1 will be described with reference to Fig. 2. In the flow chart shown in Fig. 2, each step is indicated by a reference symbol consisting of an "S" followed by a number.

The ultrasound image processing device 10 receives an instruction to start an ultrasound scan after receiving examination order information from an examination request device (not shown), such as a HIS (Hospital Information Systems). The operator places the tip of the ultrasound probe 20 on the body surface of the subject, aiming at the biological tissue (e.g., the heart, liver, pancreas, etc.), while suppressing the application of pressure. The B-mode processing function F1 controls the ultrasound transmission circuit 11, the ultrasound reception circuit 12, the pressure sensor 50, the phase sensor 60, etc., to perform an ECG-synchronized scan using the ultrasound probe 20. Note that in the first operation example, the operation of the pressure sensor 50 is not necessarily required. Then, the image generation function F3 generates a plurality of first images (step S1). If the pressure application is suppressed and considered to be 0, the image generation function F3 acquires a plurality of first images G1 (G11, G12, ...) generated only by pulsation (or respiratory fluctuation) together with an ECG waveform prior to step S2 (first measurement shown in FIG. 3 (A)). FIG. 3(A) shows multiple first images G1 when no pressure is actively applied, the applied pressure PG1 when these images were acquired, and the electrocardiogram waveform signal.

The images of biological tissue appearing in the multiple first images G1 shown in FIG. 3(A) are not static but are changing due to pulsation, respiratory fluctuation, etc. The pressures PG11, PG12, ... associated with the multiple first images G11, G12, ... respectively are pressures measured by the pressure sensor 50 when the multiple first images G11, E12, ... were acquired. The pressures PG11, PG12, ... are approximately constant values because the ultrasound probe 20 is not actively pressed against the body surface in the first measurement.

Next, the operator applies pressure to the subject's body surface toward the same biological tissue and then places the tip of the ultrasound probe 20 on it. The B-mode processing function F1 controls the ultrasound transmission circuit 11, the ultrasound reception circuit 12, the pressure sensor 50, the phase sensor 60, and the like to perform a scan using the ultrasound probe 20. Then, the image generation function F3 generates multiple second images (B-mode images) (step S2). That is, the image generation function F3 acquires multiple second images G2 (G21, G22, ...) generated by pressure application and pulsation (or respiratory fluctuation based on the respiratory sensor) together with an electrocardiogram waveform (second measurement shown in FIG. 3(B)). FIG. 3(B) shows multiple second images G2 when pressure is actively applied, the pressure PG2 (PG21, PG22, ...) [Pa] at that time, and the electrocardiogram waveform signal.

The images of biological tissue appearing in the multiple second images G2 shown in FIG. 3(B) change in response to the applied pressure PG2 in addition to pulsation and respiratory fluctuation. The pressures PG21, PG22, ... associated with the multiple second images G21, G22, ... respectively, are pressures measured by the pressure sensor 50 when the multiple second images G21, G22, ... were acquired.

The displacement amount calculation function F4 aligns the phase based on the electrocardiogram waveform (or respiratory waveform) between the multiple first images acquired in step S1 and the multiple second images acquired in step S2, and then calculates the displacement amount of biological tissue between the first image and the second image having corresponding phases as a pressure displacement amount (step S3). In other words, noise components caused by periodic movements such as pulsation and respiratory fluctuation are removed from the second image. The phase may be acquired as a cardiac phase based on phase information acquired from an electrocardiograph, or as a respiratory phase based on phase information acquired from a respiratory sensor.

For example, based on the electrocardiogram waveform, the second image G22 shown in FIG. 3(B) can be determined to be in the same phase as the first image G11 in FIG. 3(A) (shown in FIG. 4, the phase of the peak of the R wave). The displacement amount calculation function F4 calculates the amount of displacement of the biological tissue between the first image G11 and the second image G22, and sets this displacement amount as the pressure displacement amount CE22 at the phase of the second image G22. The displacement amount is calculated by block matching or the like. The displacement amount calculation function F4 records the pressure displacement amount CG22 corresponding to the second image G22 in the main memory 16 together with the applied pressure PG22 applied at that phase.

Similarly, based on the electrocardiogram waveform, the second image G23 shown in FIG. 3(B) can be determined to be in the same phase as the first image G12 shown in FIG. 3(A) (shown in FIG. 4). For example, the second image G23 and the first image G12 are images in which the elapsed time from the R wave, or the "elapsed time from the R wave/heartbeat interval" is approximately equal. The displacement amount calculation function F4 calculates the displacement amount of the biological tissue between the first image G12 and the second image G23, and sets this displacement amount as the pressure displacement amount CG23 at the phase of the second image G23. The displacement amount calculation function F4 records the pressure displacement amount CG23 corresponding to the second image G23 in the main memory 16 together with the applied pressure PG23 applied at that phase.

Similarly, based on the electrocardiogram waveform, the second image G24 shown in FIG. 3(B) can be determined to be in the same phase as the first image G13 shown in FIG. 3(A) (shown in FIG. 4). For example, the second image G24 and the first image G13 are images in which the elapsed time from the R wave, or the "elapsed time from the R wave/heartbeat interval" is approximately equal. The displacement amount calculation function F4 calculates the displacement amount of the biological tissue between the first image G13 and the second image G24, and sets this displacement amount as the pressure displacement amount CG24 at the phase of the second image G24. The displacement amount calculation function F4 records the pressure displacement amount CG24 corresponding to the second image G24 in the main memory 16 together with the applied pressure PG24 applied at that phase.

Similarly, based on the electrocardiogram waveform, the second image G25 shown in FIG. 3(B) can be determined to be in the same phase as the first image G14 shown in FIG. 3(A) (shown in FIG. 4). For example, the second image G25 and the first image G14 are images in which the elapsed time from the R wave, or the "elapsed time from the R wave/heartbeat interval" is approximately equal. The displacement amount calculation function F4 calculates the displacement amount of the biological tissue between the first image G14 and the second image G25, and sets this displacement amount as the pressure displacement amount CG25 at the phase of the second image G25. The displacement amount calculation function F4 records the pressure displacement amount CG25 corresponding to the second image G25 in the main memory 16 together with the applied pressure PG25 applied at that phase.

Similarly, based on the electrocardiogram waveform, the second image G26 shown in FIG. 3(B) can be determined to be in the same phase as the first image G15 shown in FIG. 3(A) (shown in FIG. 4). For example, the second image G26 and the first image G15 are images in which the elapsed time from the R wave, or the "elapsed time from the R wave/heartbeat interval" is approximately equal. The displacement amount calculation function F4 calculates the displacement amount of the biological tissue between the first image G15 and the second image G26, and sets this displacement amount as the pressure displacement amount CG26 at the phase of the second image G26. The displacement amount calculation function F4 records the pressure displacement amount CG26 corresponding to the second image G26 in the main memory 16 together with the applied pressure PG26 applied at that phase.

Returning to the explanation of FIG. 2, the stiffness calculation function F5 was calculated in step S3. Based on the pressure displacement amount corresponding to each second image and the applied pressure equal to or greater than the pressure threshold corresponding to each second image, the stiffness (or elasticity) of the biological tissue is calculated (step S4). Specifically, the stiffness calculation function F5 obtains the applied pressure corresponding to the pressure displacement amount as a stress-displacement hysteresis loop, and calculates the slope of the hysteresis loop as the stiffness of the biological tissue.

Figure 5 shows a stress-displacement hysteresis loop in which the applied pressure P is plotted according to the pressure displacement amount C. The stiffness calculation function F5 acquires the pressure displacement amount CG22 and the corresponding applied pressure PG22 from the main memory 16, and plots the applied pressure PG22 according to the pressure displacement amount CG22. Similarly, the stiffness calculation function F5 acquires the pressure displacement amount CG23 and the corresponding applied pressure PG23 from the main memory 16, and plots the applied pressure PG23 according to the pressure displacement amount CG23. Similarly, the stiffness calculation function F5 acquires the pressure displacement amount CG24 and the corresponding applied pressure PG24 from the main memory 16, and plots the applied pressure PG24 according to the pressure displacement amount CG24. Similarly, the stiffness calculation function F5 acquires the pressure displacement amount CG25 and the corresponding applied pressure PG25 from the main memory 16, and plots the applied pressure PG25 according to the pressure displacement amount CG25. Similarly, the stiffness calculation function F5 acquires the pressure displacement amount CG26 and the corresponding applied pressure PG26 from the main memory 16, and plots the applied pressure PG26 according to the pressure displacement amount CG26. Note that a description of the pressure displacement amount CG27 and subsequent values will be omitted.

When the pressure applied to the biological tissue by the ultrasonic probe 20 increases (compression), the plot increases from the lower left to the upper right of the hysteresis loop, whereas when the pressure applied to the biological tissue by the ultrasonic probe 20 decreases (release), the plot increases from the upper right to the lower left of the hysteresis loop. By repeatedly compressing and releasing the biological tissue by the ultrasonic probe 20, the stiffness calculation function F5 obtains multiple slopes. The stiffness calculation function F5 may obtain a single slope or may obtain an average value of multiple slopes.

As described above, the electrocardiogram waveform signal can be used to calculate stiffness after removing the effects of periodic deformation and movement of biological tissues due to pulsation of the heart and blood vessels. Note that the respiratory signal can also be used instead of the electrocardiogram waveform signal to calculate stiffness after removing the effects of periodic deformation and movement of biological tissues due to respiratory fluctuations.

The display control function F6 displays the stiffness of the biological tissue calculated in step S4 on the display 40 (step S5).

In the first operation example of the ultrasound diagnostic device 1, the displacement amount calculation function F4 associates the first images with the second images using the phase information acquired from the phase sensor 60, but the present invention is not limited to this case. For example, the displacement amount calculation function F4 may acquire the cardiac phase or respiratory phase in each of the first images and the second images based on the morphology of the biological tissue contained in the first images and the second images. In this case, the phase sensor 60 is not required. The displacement amount calculation function F4 may acquire the phase information of each image using machine learning. For example, deep learning using a multi-layer neural network such as a CNN (convolutional neural network) or a convolutional deep belief network (CDBN) is used as the machine learning. The displacement amount calculation function F4 constructs a trained model using a pair of an image and phase information indicated by the image, and inputs the first images and the second images to the trained model, respectively, to output the phase information of each image.

As described above, according to the first operation example of the ultrasound diagnostic device 1, it is possible to obtain only the pressure displacement amount by removing noise components from the measured displacement amount, which includes the pressure displacement amount dependent on the externally applied pressure and the noise components due to biological displacement caused by pulsation and respiratory fluctuation. By calculating the stiffness of biological tissue using the pressure displacement amount rather than the measured displacement amount, it is possible to improve the accuracy of measuring the stiffness of biological tissue.

(Second operation example)
The second operation example of the ultrasound diagnostic device 1 is, in the first operation example described above, to forcibly terminate the scan if the pressure acquired during the first measurement exceeds a threshold value, and output a message to that effect to the operator.

A second operation example of the ultrasound diagnostic device 1 will be described with reference to FIG. 6. In the flowchart shown in FIG. 6, the reference numbers with "S" followed by a number indicate each step. Note that in FIG. 6, the same steps as in FIG. 2 are given the same reference numbers and their description will be omitted.

After receiving test order information from a test request device (not shown), such as an HIS, the ultrasound image processing device 10 accepts an instruction to start a scan. The operator places the tip of the ultrasound probe 20 against the body surface of the subject, aiming at the biological tissue, while suppressing the application of pressure. The B-mode processing function F1 controls the ultrasound transmission circuit 11, the ultrasound reception circuit 12, the pressure sensor 50, the phase sensor 60, etc., to start performing an ECG-gated scan using the ultrasound probe 20. Note that, unlike the first operation example described above, the second operation example requires the operation of the pressure sensor 50. Then, the image generation function F3 starts generating a plurality of first images (B-mode images) (step S11).

When acquiring the first images, the image generating function F3 judges whether or not an applied pressure equal to or greater than the pressure threshold has been detected (step S12). If the judgment in step S12 is YES, that is, if it is judged that an applied pressure equal to or greater than the pressure threshold has been detected, the image generating function F3 judges whether or not the applied pressure equal to or greater than the pressure threshold detected in step S12 continues beyond the time threshold (step S13). If the judgment in step S13 is NO, that is, if the applied pressure equal to or greater than the pressure threshold is only for a period equal to or less than the time threshold (immediately drops below the pressure threshold), the image generating function F3 stops acquiring the first images (transmitting and receiving ultrasonic waves) as the first measurement is inappropriate due to the large influence of the applied pressure, and outputs a message indicating that the acquisition has stopped (step S14). For example, the image generating function F3 displays on the display 40 that the acquisition of the first images has stopped.

On the other hand, if the determination in step S13 is YES, that is, if it is determined that the applied pressure equal to or greater than the pressure threshold continues beyond the time threshold, the process proceeds to step S2. If the determination in step S12 is NO, that is, if it is determined that the applied pressure equal to or greater than the pressure threshold has not been detected, the image generation function F3 continues scanning until it detects an applied pressure equal to or greater than the pressure threshold.

As described above, according to the second operation example of the ultrasound image processing device 10, in addition to the effect of the second operation example described above, an inappropriate first measurement can be stopped and the operator can be notified of this. As a result, the operator can recognize that a first measurement is necessary again.

(Third operation example)
The third operation example of the ultrasound diagnostic device 1 differs from the above-described first and third operation examples in that it does not require the phase sensor 60 and does not require acquisition of an electrocardiogram waveform or a respiratory waveform.

A third operation example of the ultrasound diagnostic device 1 will be described with reference to FIG. 7. In the flowchart shown in FIG. 7, the reference numbers with "S" followed by a number indicate each step. Note that in FIG. 7, the same steps as in FIG. 2 are given the same reference numbers and their description will be omitted.

After receiving examination order information from an examination request device (not shown), such as an HIS, the ultrasound image processing device 10 accepts an instruction to start a thrustography scan. The operator places the tip of the ultrasound probe 20 against the body surface of the subject while suppressing the application of pressure toward the living tissue. The B-mode processing function F1 controls the ultrasound transmission circuit 11, the ultrasound reception circuit 12, the pressure sensor 50, etc. to perform a scan using the ultrasound probe 20. Then, the image generation function F3 acquires multiple images (B-mode images) (step S21). If the pressure application is suppressed and considered to be 0, the image generation function F3 acquires multiple first images H1 (H11, H12, ...) generated only by pulsation (or respiratory fluctuation) together with an electrocardiogram waveform prior to step S22 (first measurement shown in FIG. 8 (A)). FIG. 8 (A) shows multiple first images H1 when pressure is not actively applied and the applied pressure PH1 when these images are acquired.

The images appearing in the multiple first images H1 shown in FIG. 8(A) are not static but are changing due to pulsation, respiratory fluctuation, etc. The pressures PH11, PH12, ... associated with the multiple first images H11, H12, ... respectively are pressures measured by the pressure sensor 50 when the multiple first images H11, H12, ... were acquired, and are approximately constant values because the ultrasound probe 20 was not actively pressed against the body surface in the first measurement.

Next, the operator applies pressure to the subject's body surface toward the same biological tissue and then places the tip of the ultrasound probe 20 on it. The B-mode processing function F1 controls the ultrasound transmission circuit 11, the ultrasound reception circuit 12, the pressure sensor 50, and the like to perform a scan using the ultrasound probe 20. The image generation function F3 then acquires multiple second images (B-mode images) (step S22). That is, the image generation function F3 applies pressure to acquire multiple second images H (H21, H22, ...) (second measurement shown in FIG. 8(B)). FIG. 8(B) shows multiple second images H22 when pressure is actively applied, and the pressure PH2 (PH21, PH22, ...) at that time.

The images appearing in the multiple second images H2 shown in FIG. 8(B) change according to the applied pressure PH, in addition to pulsation and respiratory fluctuation. The pressures PH21, PH22, ... associated with the multiple second images H21, H22, ... respectively, are pressures measured by the pressure sensor 50 when the multiple second images H21, H22, ... were acquired.

The displacement amount calculation function F4 aligns the phase based on the electrocardiogram waveform (or respiratory waveform) between the multiple first images acquired in step S21 and the multiple second images acquired in step S22, and then calculates the displacement amount of biological tissue between the first image and the second image that correspond in phase as the pressure displacement amount (step S23). In other words, noise components caused by periodic movements such as pulsation and respiratory fluctuation are removed from the second image.

For example, six variation elements _CH211 to CH216 of the biological tissue are calculated between the second image H21 shown in Fig. 8(B) and each of the six first images H11 to H16 shown in Fig. 8( _A ) (shown in Fig. 9). The displacement amount calculation function F4 obtains the average value of the _six displacement amount elements _CH211 to CH216 as the pressure displacement amount CH21 in the second image H21, and records the pressure displacement amount CH21 in the second image H21 in the main memory 16 together with the applied pressure PH21 applied at that phase.

Similarly, six displacement amount elements CH221 to _CH226 of the biological tissue are calculated between the second image H22 shown in Fig. 8(B) and each of the six first images H11 to H16 shown in Fig. ₈ (A). The type of the first image to be compared with the second image H22 is the same as the type of the second image H21 described above. The displacement amount calculation function F4 obtains the average value of the six displacement amount elements _CH221 to _CH226 as the pressure displacement amount CH22 of the second image H22, and records the pressure displacement amount CH22 in the second image H22 in the main memory 16 together with the applied pressure PH22 applied at that phase.

The same applies to the method of calculating the pressure displacement amount for the second image H23 and subsequent images shown in FIG. 8(B). It has been described that the displacement amount calculation function F4 calculates multiple displacement amount elements of the biological tissue between each second image and the same multiple first images (six first images H11 to H16) among the multiple first images, and sets the average value of the multiple displacement amount elements as the pressure displacement amount corresponding to each second image, but this is not limited to the case. It is sufficient to calculate multiple displacement amount elements of the biological tissue between each second image and multiple first images among the multiple first images, and set the average value of the multiple displacement amount elements as the pressure displacement amount corresponding to each second image. For example, the displacement amount calculation function F4 may stagger the acquisition times while keeping the number of multiple first images compared with the second image the same.

Next, the stiffness calculation function F5 calculates the stiffness (or elasticity) of the biological tissue based on the displacement of the biological tissue calculated in step S23 and the corresponding pressure P (step S4).

As described above, according to the third operation example of the ultrasound image processing device 10, it is possible to extract only the pressure displacement amount by removing noise components from the measured displacement amount, which includes the pressure displacement amount dependent on the externally applied pressure and the noise components due to biological displacement caused by pulsation and respiratory fluctuation, without the phase sensor 60. By calculating the stiffness of biological tissue using the pressure displacement amount rather than the measured displacement amount, it is possible to improve the accuracy of measuring the stiffness of biological tissue.

Second Embodiment
The second embodiment relates to a medical information processing device 80 (also shown in FIG. 1 ) communicatively connected to an ultrasonic diagnostic device 1 that acquires the pressure applied to a subject from a pressure sensor 50 attached to an ultrasonic probe 20 .

As shown in FIG. 10, the medical information processing device 80 includes a network interface 84, a processing circuit 85, a memory 86, an input interface 87, and a display 88. Note that the configurations of the network interface 84, the processing circuit 85, the memory 86, the input interface 87, and the display 88 are the same as the configurations of the network interface 14, the processing circuit 15, the main memory 16, the input interface 30, and the display 40 shown in FIG. 1, respectively, and therefore will not be described.

The processing circuitry 85 realizes a displacement calculation function F4, a stiffness calculation function F5, a display control function F6, and an image generation function F7 by reading and executing a computer program stored in the memory 86 or a memory within the processing circuitry 85. Below, an example will be described in which the functions F4 to F7 are realized by a computer program, but all or part of the functions F4 to F7 may be provided in the medical information processing device 80 as functions of a circuit such as an ASIC. Note that in FIG. 10, the same functions as those shown in FIG. 1 are denoted by the same reference numerals and will not be described.

The image acquisition function F7 includes a function for acquiring, via the network N, a plurality of first images in a time series including biological tissue, which were generated with an applied pressure below a threshold value, and acquiring, via the network N, a plurality of second images in a time series including biological tissue, which were generated with an applied pressure equal to or greater than the threshold value.

The displacement amount calculation function F4 includes a function for calculating the displacement amount of biological tissue between each second image acquired by the image acquisition function F7 and a plurality of first images acquired by the image acquisition function F7 as a pressure displacement amount (a displacement amount obtained by removing noise components from the measured displacement amount).

In post-processing, the medical information processing device 80 operates in the same manner as the first to third operation examples described above in the ultrasound diagnostic device 1.

As described above, according to the example operation of the medical information processing device 80, it is possible to extract only the pressure displacement amount by removing noise components from the measured displacement amount, which includes the pressure displacement amount dependent on the externally applied pressure and the noise components due to biological displacement caused by pulsation and respiratory fluctuation. By calculating the stiffness of biological tissue using the pressure displacement amount rather than the measured displacement amount, it is possible to improve the accuracy of measuring the stiffness of biological tissue.

According to at least one of the embodiments described above, the accuracy of measuring the stiffness of biological tissue can be improved by calculating the stiffness of biological tissue using the pressure displacement amount rather than the measured displacement amount.

The B-mode processing function F1 is an example of a B-mode processing unit. The Doppler processing function F2 is an example of a Doppler processing unit. The image generation function F3 is an example of an image generation unit. The displacement amount calculation function F4 is an example of a displacement amount calculation unit. The stiffness calculation function F5 is an example of a stiffness calculation unit. The display control function F6 is an example of a display control unit. The image acquisition function F7 is an example of an image acquisition unit.

Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, combinations of embodiments, and combinations of embodiments with one or more modified examples can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

1...Ultrasound diagnostic device 10...Ultrasound image processing device 15...Processing circuit 20...Ultrasound probe 30...Input interface 40...Display 50...Pressure sensor 60...Phase sensor 80...Medical information processing device F1...B-mode processing function F2...Doppler processing function F3...Image generation function F4...Displacement amount calculation function F5...Hardness calculation function F6...Display control function F7...Image acquisition function

Claims (9)

An ultrasonic diagnostic apparatus that acquires an applied pressure to a subject from a pressure sensor attached to an ultrasonic probe,
an image generating unit that generates a plurality of first images in a time series including the biological tissue at an applied pressure less than a pressure threshold, and generates a plurality of second images in a time series including the biological tissue at an applied pressure equal to or greater than the pressure threshold;
a displacement amount calculation unit that calculates a displacement amount of the biological tissue between each of the second images of the plurality of second images and the plurality of first images;
a stiffness calculation unit that calculates stiffness of the biological tissue based on the displacement amount corresponding to each of the second images and the applied pressure equal to or greater than the pressure threshold corresponding to each of the second images;
An ultrasound diagnostic device comprising: The displacement amount calculation unit
calculating a displacement amount of the biological tissue between each of the second images and a first image among the plurality of first images, the first image having a corresponding cardiac phase or respiratory phase;
The ultrasonic diagnostic apparatus according to claim 1 . The displacement amount calculation unit
acquiring the cardiac phase in each of the first images and the second images based on phase information acquired from an electrocardiograph, and acquiring the respiratory phase in each of the first images and the second images based on phase information acquired from a respiratory sensor;
The ultrasonic diagnostic apparatus according to claim 2 . The displacement amount calculation unit
acquiring the cardiac phase or the respiratory phase in each of the first images and the second images based on morphologies of the biological tissue included in the first images and the second images;
The ultrasonic diagnostic apparatus according to claim 2 . The displacement amount calculation unit
Calculating a plurality of displacement amount elements of the biological tissue between each of the second images and a plurality of first images among the plurality of first images, and setting an average value of the plurality of displacement amount elements as the displacement amount corresponding to each of the second images.
The ultrasonic diagnostic apparatus according to claim 1 . The displacement amount calculation unit
Calculating a plurality of displacement amount elements of the biological tissue between each of the second images and the same plurality of first images among the plurality of first images, and setting an average value of the plurality of displacement amount elements as the displacement amount corresponding to each of the second images.
The ultrasonic diagnostic apparatus according to claim 1 . The image generating unit includes:
When an applied pressure equal to or greater than the pressure threshold is detected for a period equal to or less than a time threshold during acquisition of the plurality of first images, the acquisition of the plurality of first images is stopped, and a message is output to the effect that the acquisition has been stopped.
7. The ultrasonic diagnostic apparatus according to claim 1. A medical information processing device communicably connected to an ultrasonic diagnostic device that acquires an applied pressure to a subject from a pressure sensor attached to an ultrasonic probe,
an image acquisition unit that acquires a plurality of first images in a time series including biological tissue generated at an applied pressure less than a pressure threshold, and acquires a plurality of second images in a time series including biological tissue generated at an applied pressure equal to or greater than the pressure threshold;
a displacement amount calculation unit that calculates a displacement amount of the biological tissue between each of the second images of the plurality of second images and the plurality of first images;
a stiffness calculation unit that calculates stiffness of the biological tissue based on the displacement amount corresponding to each of the second images and the applied pressure equal to or greater than the pressure threshold corresponding to each of the second images;
A medical information processing device comprising: On the computer,
generating a plurality of first images in a time series including the biological tissue at an applied pressure less than a pressure threshold, and generating a plurality of second images in a time series including the biological tissue at an applied pressure equal to or greater than the pressure threshold;
A function of calculating a displacement amount of the biological tissue between each of the second images of the plurality of second images and the plurality of first images;
a function of calculating a hardness of the biological tissue based on the displacement amount corresponding to each of the second images and the applied pressure equal to or greater than the pressure threshold corresponding to each of the second images;
A hardness calculation program that makes this possible.

Images