JP2014000260A - Ultrasonic diagnostic device, medical image processor, medical image processing method and medical image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic device, capable of visualizing the propagation of a shearing wave generated in a subject in the form of being simply confirmed by an inspector.SOLUTION: An ultrasonic diagnostic device 1 related to the present embodiment includes: an ultrasonic probe 3; a transmitting part 11 for transmitting a first ultrasonic wave for generating a shearing wave in a subject to a first region through the ultrasonic probe 3, and transmitting a second ultrasonic wave to a second region in the subject; a receiving part 13 for generating a receive signal based on the second ultrasonic wave; a displacement calculating part 19 for calculating the displacement of a tissue caused by the propagation of a shearing wave to the second region using the receive signal; an arrival time deciding part 21 for deciding the arrival time when the shearing wave arrives at each position based on a time change of the displacement concerning each position in the second region; and an image generating part 23 for generating a shearing wave arrival image to which a hue is assigned according to the arrival time based on the arrival time and the hue preset according to the arrival time.

Description

  Embodiments of the present invention provide an ultrasonic diagnostic apparatus, a medical image processing apparatus, a medical image processing method, and a medical image that image an internal organ of a subject by scanning inside the subject and diagnose a disease of the subject. It relates to a processing program.

  The ultrasonic diagnostic apparatus can display the state of heart beat and fetal movement in real time with a simple operation of simply touching the ultrasonic probe from the body surface in ultrasonic diagnosis. In addition, since the ultrasonic diagnostic apparatus is highly safe, it is repeatedly used for inspection. Furthermore, the ultrasonic diagnostic apparatus has an X-ray diagnostic apparatus, an X-ray computed tomography (hereinafter referred to as CT) apparatus, a magnetic resonance imaging apparatus (hereinafter referred to as MRI), and the like. Smaller than other medical image diagnostic apparatuses. For this reason, the ultrasonic diagnostic apparatus also has convenience such as being easily usable for examination by being moved to the bedside. In addition, the ultrasonic diagnostic apparatus is used in obstetrics, home medical care and the like because there is no influence of exposure on the subject unlike a medical image diagnostic apparatus using X-rays.

  In recent years, ultrasonic diagnostic apparatuses having a function of evaluating the hardness of a tissue in a subject have been widely used. There are roughly two methods for evaluating hardness. First, by compressing and releasing the tissue in the subject from the body surface with an ultrasonic probe, the strain of each point in the cross section observed at the time of compression and release is used to determine the tissue in the subject. It is a method of visualizing relative hardness. Second, by applying acoustic radiation force or mechanical vibration from the body surface to the tissue, the tissue displacement at each point in the cross section is observed over time. Specifically, it is a method of obtaining the elastic modulus of the tissue to be diagnosed by obtaining the propagation velocity of a shear wave (shear wave) generated by acoustic radiation force or mechanical vibration.

  In the first method, the magnitude of the local distortion depends on the magnitude by which the operator moves the ultrasonic probe. In the first method, the hardness of an area focused by the operator (hereinafter referred to as the focused area) is compared with the hardness of the area around the focused area (hereinafter referred to as the peripheral area). Done. That is, in the first method, the hardness of the region of interest is a relative hardness compared to the hardness of the peripheral region.

  In the second method, the absolute elastic modulus of the region of interest can be obtained. Specifically, in the second method, generally, the displacement of the tissue at each position in the subject due to the passage of the generated shear wave is acquired in time series. In addition, since the tissue displacement may include the entire tissue displacement due to the body movement of the subject in addition to the tissue displacement due to the shear wave, a process for canceling the entire tissue displacement is generally used. To be executed. Next, the time when the displacement at each position becomes maximum is estimated as the arrival time when the shear wave arrives. Based on the estimated arrival time and the distance from the shear wave generation position to each position, the propagation speed of the shear wave propagated through the subject is obtained.

  However, if the direction and speed of the overall movement of the tissue is irregular such that it changes in a short time, cancellation of the overall displacement of the tissue may not be accurate. In addition, depending on the location of the region of interest and the hardness of the tissue, the displacement of the tissue due to the shear wave becomes minute, and the arrival time may not be accurately estimated. In addition, when the shear wave is reflected / refracted at the boundary surface of the tissue, and when a blood vessel through which the shear wave does not propagate exists in the region of interest, the arrival time may be erroneously obtained.

  If the cancellation of the overall displacement of the tissue is not performed correctly, if the shear wave is reflected / refracted, or if there is an area where the shear wave does not propagate in the area of interest, the position of the area of interest The arrival time of the shear wave to each position is a point that deviates from the overall tendency of the arrival time. For this reason, points that deviate from the overall tendency are excluded in the process of calculating the propagation speed of shear waves, or it is determined that the propagation speed of shear waves cannot be calculated and output so that no plotting is performed. . For this reason, a method for indicating the degree of reliability with respect to the calculated propagation speed of the shear wave has also been proposed.

  However, when measurement results such as the propagation velocity of shear waves are not output, there is a problem that the operator cannot specifically know the reason why the measurement results are not output. In addition, even when measurement results such as shear wave propagation velocity are output, there is a problem that the operator cannot specifically know how reliable the measurement results are. is there. In addition, when the measurement result is low, there is a problem that the operator cannot determine whether or not a reliable measurement result can be obtained by changing the measurement area. Therefore, the operator blindly sets the region of interest, makes a comprehensive judgment based on the obtained measurement results (numerical values), palpation and other clinical findings, and determines whether the obtained numerical values are appropriate. I am doing. From the above, in the conventional ultrasonic diagnostic apparatus, the operator cannot judge the validity of the measurement result obtained by the above method unless a certain degree of examination is made on the hardness of the tissue in the subject in advance. There's a problem.

  There is a demand for a display method capable of intuitively and easily grasping the validity of the measurement result even when the operator cannot predict the hardness of the tissue in the subject. For example, how the shear wave, which is the primary information of hardness measurement, propagates in the subject (for example, whether it propagates uniformly in the lateral direction as expected by the operator, It suffices for the operator to check whether the shear wave is reflected and refracted or whether the shear wave propagates with some tendency. For example, there is a method of displaying the state of shear wave propagation as a movie as a method for the operator to check the state of shear wave propagation. In clinical practice, a movie that confirms the propagation of shear wave is displayed for each measurement. However, since it takes time to confirm the propagation of the shear wave, there is a problem that is not practical.

  An object of the present embodiment is to provide an ultrasonic diagnostic apparatus that can visualize the propagation of shear waves generated in a subject in a form that allows an examiner to easily confirm the propagation.

  The ultrasonic diagnostic apparatus according to the present embodiment transmits an ultrasonic probe having a plurality of transducers and a first ultrasonic wave that generates a shear wave in a subject to the first region via the ultrasonic probe. And generating a reception signal based on the second ultrasonic wave and a transmitter for transmitting a second ultrasonic wave for observing a displacement at a predetermined position to the second region in the subject. A reception unit; a displacement amount calculation unit that calculates a displacement amount of the tissue accompanying propagation of the shear wave to the second region using the received signal; and a time of the displacement amount for each position of the second region. Based on the change, the arrival time determination unit that determines the arrival time at which the shear wave has arrived at each position, and the arrival time based on the arrival time and a hue set in advance according to the arrival time. The hue is not assigned accordingly Characterized by comprising an image generator for generating a wave arrival image.

FIG. 1 is a configuration diagram illustrating an example of the configuration of the ultrasonic diagnostic apparatus according to the first embodiment. FIG. 2 is a diagram illustrating an example of a flowchart illustrating a procedure of processing related to the displacement amount observation scanning function according to the first embodiment. FIG. 3 relates to the first embodiment, and shows a scanning line related to the first ultrasonic wave that generates a shear wave and a scanning line related to the second ultrasonic wave for obtaining the first and second received signals. It is a figure shown with a region of interest. FIG. 4 is a diagram illustrating an example of a flowchart illustrating a procedure of processing relating to the shear wave arrival image generation function according to the first embodiment. FIG. 5 is a diagram illustrating an example of a temporal change in the amount of tissue displacement at a position of a region of interest according to the first embodiment. FIG. 6 is a diagram illustrating an example of a temporal change of the displacement amount obtained by removing the tissue displacement amount due to the body movement of the subject at a position of the region of interest according to the first embodiment. FIG. 7 is a diagram illustrating an example of a temporal change in the amount of tissue displacement at a position of a region of interest according to the first embodiment. FIG. 8 is a diagram illustrating an example of a temporal change of the displacement amount obtained by removing the tissue displacement amount due to the body movement of the subject at a position of the region of interest according to the first embodiment. FIG. 9 is a diagram illustrating an example of the generated shear wave arrival image according to the first embodiment, together with an example of a color map showing a legend of hue corresponding to the shear wave arrival time. FIG. 10 is a diagram illustrating an example of a flowchart illustrating a procedure of processing relating to a shear wave arrival correction image generation function according to a modification of the first embodiment. FIG. 11 is a diagram illustrating an example of the shear wave arrival correction image together with an example of the shear wave arrival image according to the modification of the first embodiment. FIG. 12 is a configuration diagram illustrating an example of a configuration of an ultrasonic diagnostic apparatus according to the second embodiment. FIG. 13 is a diagram illustrating an example of a flowchart illustrating a procedure of shear wave propagation velocity image generation processing according to the second embodiment. FIG. 14 shows an example of a temporal change in displacement in a direction away from the ultrasonic probe at four points of the same depth on four different scanning lines according to the first modification of the second embodiment. FIG. FIG. 15 relates to the first modification of the second embodiment, and the relationship of the distance from the shear wave generation position to the shear wave arrival time at four points of the same depth on four different scanning lines. It is a figure which shows an example.

  The ultrasonic diagnostic apparatus according to this embodiment will be described below with reference to the drawings. In the following description, components having substantially the same configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

(First embodiment)
FIG. 1 is a configuration diagram showing a configuration of an ultrasonic diagnostic apparatus 1 according to the first embodiment. As shown in the figure, the ultrasonic diagnostic apparatus 1 is connected to the ultrasonic probe 3, the apparatus main body 5, the display unit 7, and the apparatus main body 5 to take various instructions / commands / information from the operator into the apparatus main body 5. Input section 9. In addition, a biological signal measurement unit (not shown) and a network represented by an electrocardiograph, a heart sound meter, a pulse wave meter, and a respiration sensor are connected to the ultrasonic diagnostic apparatus 1 via an interface unit 29 described later. May be.

  The ultrasonic probe 3 includes a plurality of piezoelectric vibrators, a matching layer, and a backing material provided on the back side of the plurality of piezoelectric vibrators. The plurality of piezoelectric vibrators are acoustic / electric reversible conversion elements such as piezoelectric ceramics. The plurality of piezoelectric vibrators are arranged in parallel and are provided at the tip of the ultrasonic probe 3. Hereinafter, description will be made assuming that one piezoelectric vibrator constitutes one channel. The piezoelectric vibrator generates an ultrasonic wave in response to a drive signal supplied from a transmission unit 11 described later. When an ultrasonic wave is transmitted to the subject P via the ultrasonic probe 3, the transmitted ultrasonic wave (hereinafter referred to as a transmitted ultrasonic wave) is reflected by a discontinuous surface of acoustic impedance in a living tissue in the subject. Is done. The piezoelectric vibrator receives the reflected ultrasonic wave and generates an echo signal. The amplitude of the echo signal depends on the difference in acoustic impedance with the discontinuous surface regarding the reflection of the ultrasonic wave as a boundary. The frequency of the echo signal when the transmitted ultrasonic wave is reflected by the moving blood flow and the surface of the heart wall, etc. is transmitted by the Doppler effect. It shifts depending on the velocity component of the direction.

  Hereinafter, the ultrasonic probe 3 will be described as a probe that performs two-dimensional scanning with a one-dimensional array. Note that the ultrasonic probe 3 may be a mechanical four-dimensional probe that performs three-dimensional scanning by swinging a one-dimensional array in a direction orthogonal to the arrangement direction of a plurality of transducers. Further, the ultrasonic probe 3 is not limited to a mechanical four-dimensional probe, and may be a two-dimensional array probe.

  The matching layer is provided on the ultrasonic radiation surface side of the plurality of piezoelectric vibrators in order to efficiently transmit and receive ultrasonic waves to and from the subject P. The backing material prevents the propagation of ultrasonic waves to the back of the piezoelectric vibrator.

  The apparatus body 5 includes a transmission unit 11, a reception 13, a B-mode processing unit 15, a Doppler processing unit 17, a displacement amount calculation unit 19, an arrival time determination unit 21, an image generation unit 23, and an image synthesis unit. 25, a storage unit 27, an interface unit 29, and a control unit (Central Processing Unit: hereinafter referred to as CPU) 31.

  The transmission unit 11 includes a pulse generator 11A, a transmission delay circuit 11B, and a pulsar circuit 11C. The pulse generator 11A repeatedly generates a rate pulse for forming a transmission ultrasonic wave at a predetermined rate frequency frHz (cycle: 1 / fr second). The generated rate pulse is distributed to the number of channels and sent to the transmission delay circuit 11B.

  The transmission delay circuit 11B uses, for each rate pulse, a delay time (hereinafter referred to as a transmission delay time) necessary for converging the transmission ultrasonic wave in a beam shape and determining transmission directivity for each of a plurality of channels. give. The transmission direction or transmission delay time of transmission ultrasonic waves (hereinafter referred to as a transmission delay pattern) is stored in the storage unit 27 described later. The transmission delay pattern stored in the storage unit 27 is referred to when transmitting ultrasonic waves by the CPU 3 described later.

  The pulser circuit 11C applies a voltage pulse (drive signal) to each transducer of the ultrasonic probe 3 at a timing based on this rate pulse. Thereby, an ultrasonic beam is transmitted to the subject.

  Hereinafter, transmission of the first ultrasonic wave that generates a shear wave will be described in detail. The transmission unit 11 transmits a push pulse (first ultrasonic wave) that generates a shear wave in the subject to the first region described later via the ultrasonic probe 3. The transmission unit 11 transmits the second ultrasonic wave to a second region described later before and after the transmission of the first ultrasonic wave. The second ultrasonic wave is transmitted by the transmission unit 11 in order to obtain the amount of tissue displacement caused by the shear wave generated in the first region. Specifically, the transmission unit 11 receives a region of interest (hereinafter referred to as ROI) input via the input unit 9 described later, or a region focused by the operator (hereinafter referred to as a region of interest). A push pulse is transmitted in the vicinity of the boundary in the azimuth direction of a predetermined area (hereinafter referred to as a first area) such as a predetermined depth (hereinafter referred to as a shear wave generation position). To do. In other words, for example, the shear wave generation position is set on the scanning line outside the predetermined area and in the vicinity of the predetermined area. The preset depth is, for example, the average depth of a predetermined region.

  The frequency of the push pulse is substantially the same as the frequency of the ultrasonic wave transmitted in the B mode and the Doppler mode. The wave number of the push pulse is larger than the wave number of the ultrasonic wave transmitted in the B mode and the Doppler mode. Specifically, the transmission unit 11 uses a CPU 31 to be described later, for example, a transmission delay pattern (hereinafter referred to as a shear wave generation transmission delay pattern) for converging an ultrasonic wave in a beam shape at a midpoint in the depth direction of the first region. Is read from the storage unit 27. The transmission delay circuit 11B gives a transmission delay time according to the shear wave generation transmission delay pattern to each rate pulse. The pulser circuit 11C applies a drive signal for generating a push pulse to each vibrator at a timing based on the rate pulse.

  The transmission unit 11 transmits the second ultrasonic wave to a predetermined area (second area) before and after transmitting the first ultrasonic wave.

  The receiving unit 13 includes a preamplifier 13A, an analog-to-digital (hereinafter referred to as A / D) converter, a reception delay circuit 13B, and an adder 13C (not shown). The receiving unit 13 generates a reception signal based on the reflected wave caused by the second ultrasonic wave and the shear wave.

  The preamplifier 13A amplifies the echo signal from the subject P taken in via the ultrasonic probe 3 for each channel. The A / D converter converts the amplified received echo signal into a digital signal.

  The reception delay circuit 13B gives a delay time (hereinafter referred to as reception delay time) necessary for determining reception directivity to the reception echo signal converted into the digital signal. The reception direction or reception delay time of the echo signal (hereinafter referred to as reception delay pattern) is stored in the storage unit 27 described later. The reception delay pattern stored in the storage unit 27 is referred to by the CPU 31 described later. The adder 13C adds a plurality of echo signals given delay times. By this addition, the reception unit 13 generates a reception signal (also referred to as an RF (radiofrequency) signal) that emphasizes the reflection component from the direction according to the reception directivity. The overall directivity of ultrasonic transmission / reception is determined by the transmission directivity and the reception directivity. This total directivity determines the ultrasonic beam (so-called “ultrasonic scanning line”). Specifically, the receiving unit 13 receives a reflected wave of the second ultrasonic wave related to the physical tissue displacement caused by the shear wave.

  The B mode processing unit 15 includes an envelope detector, a logarithmic converter, and the like not shown. The envelope detector performs envelope detection on the reception signal output from the reception unit 13. The envelope detector outputs the envelope-detected signal to a logarithmic converter described later. The logarithmic converter relatively emphasizes a weak signal by logarithmically converting the envelope-detected signal. The B mode processing unit 15 generates a signal value (B mode data) for each depth in each scanning line and each ultrasonic wave transmission / reception based on the signal emphasized by the logarithmic converter.

  When the ultrasonic probe 3 is a mechanical four-dimensional probe or a two-dimensional array probe, the B-mode processing unit 15 performs an azimuth direction, an elevation direction, and a depth direction in the scanned region. Three-dimensional B-mode data including a plurality of signal values arranged in association with each other (hereinafter referred to as a range direction) may be generated. The range direction is the depth direction on the scanning line. The azimuth direction is, for example, an electronic scanning direction along the arrangement direction of the one-dimensional ultrasonic transducers. The elevation direction is the mechanical oscillation direction of the one-dimensional ultrasonic transducer. The three-dimensional B-mode data may be data in which a plurality of pixel values or a plurality of luminance values are arranged in association with the azimuth direction, the elevation direction, and the range direction along the scanning line. . The three-dimensional B-mode data may be data relating to ROI set in advance in the scanned region. Further, the B mode processing unit 15 may generate volume data instead of the three-dimensional B mode data. Hereinafter, data generated by the B-mode processing unit 15 is collectively referred to as B-mode data.

The Doppler processing unit 17 includes a mixer (not shown), a low-pass filter (hereinafter referred to as LPF), a speed / dispersion / Power calculation device, and the like. The mixer multiplies the reception signal output from the reception unit 17 by a reference signal having the same frequency f ₀ as the transmission frequency. By this multiplication, a signal having a component of Doppler shift frequency f _d and a signal having a frequency component of (2f ₀ + f _d ) are obtained. The LPF removes a signal having a high frequency component (2f ₀ + f _d ) from signals having two types of frequency components from the mixer. The Doppler processing unit 142 generates a Doppler signal having a component of the Doppler shift frequency f _d by removing the signal of the high frequency component (2f ₀ + f _d ).

The Doppler processing unit 17 may use a quadrature detection method in order to generate a Doppler signal. At this time, the received signal (RF signal) is quadrature detected and converted to an IQ signal. Doppler processing unit 142, by complex Fourier transform of the IQ signal, for generating a Doppler signal having a component of the Doppler shift frequency f _d. The Doppler signal is, for example, a Doppler component due to blood flow, tissue, or contrast medium.

  The speed / dispersion / Power calculation device includes an MTI (Moving Target Indicator) filter, an LPF filter, an autocorrelation calculator, and the like (not shown). A cross-correlation calculator may be provided instead of the autocorrelation calculator. The MTI filter removes Doppler components (clutter components) caused by respiratory movement or pulsatile movement of the organ from the generated Doppler signal. The MTI filter is used to extract a Doppler component related to blood flow (hereinafter referred to as a blood flow Doppler component) from the Doppler signal. The LPF is used to extract a Doppler component related to tissue movement (hereinafter referred to as a tissue Doppler component) from the Doppler signal.

  The autocorrelation calculator calculates autocorrelation values for the blood flow Doppler component and the tissue Doppler component. Based on the calculated autocorrelation value, the autocorrelation calculator calculates an average velocity value, a variance value, a reflection intensity (power) of the Doppler signal, and the like of the blood flow and the tissue. The velocity / dispersion / power calculation device generates color Doppler data at each position in a predetermined region based on blood flow and tissue average velocity values based on a plurality of Doppler signals, dispersion values, reflection intensity of Doppler signals, and the like. Hereinafter, Doppler signals and color Doppler data are collectively referred to as Doppler data.

  Hereinafter, processing for calculating the phase difference of the tissue Doppler component using the autocorrelation calculator (hereinafter referred to as autocorrelation processing) will be described. First, ultrasonic waves are transmitted and received a plurality of times (n times) at a predetermined pulse repetition frequency (hereinafter referred to as PRF) in one scanning line direction. Next, the reception unit 13 generates a plurality of reception signals (n). A plurality of tissue Doppler components are extracted from a plurality of Doppler signals respectively corresponding to the plurality of received signals. To the tissue Doppler component, a depth in one scanning line direction and a number indicating the number of transmission / receptions are added as supplementary information.

The autocorrelation calculator performs autocorrelation processing on a plurality of tissue Doppler components (n) at the same depth in one scanning line direction. Specifically, based on the i th (1 ≦ i ≦ n−1) tissue Doppler component TD (i) and the (i + 1) th (2 ≦ i + 1 ≦ n) tissue Doppler component TD (i + 1), Calculate the phase difference of the tissue Doppler component. More specifically, the autocorrelation calculator performs a complex Fourier transform on the complex conjugate product TD (i) × TD ^* (i + 1) of TD (i) and TD (i + 1), thereby obtaining TD (i ) And TD (i + 1). The procedure for calculating the phase difference is repeatedly calculated from i = 1 to i = n−1. That is, (n−1) phase differences are calculated for each 1 / PRF and for each depth, using n received signals generated by transmission / reception of n ultrasonic waves in one scanning line direction. The The phase difference may be calculated each time a tissue Doppler component is generated. The phase difference corresponds to the amount of tissue displacement for each 1 / PRF and for each depth. By accumulating the first to i-th phase differences, the displacement amount of the i-th tissue based on the first tissue Doppler component can be obtained.

  The phase difference may be calculated by a cross-correlation process by a cross-correlation calculator (not shown) instead of the autocorrelation process. The cross-correlation process is, for example, a process of calculating a phase difference between a tissue Doppler component obtained by transmission / reception of the first ultrasonic wave and a tissue Doppler component obtained by transmission / reception of the second and subsequent ultrasonic waves. That is, the cross-correlation process is a process for calculating a phase difference with reference to a tissue Doppler component obtained by first transmission / reception of an ultrasonic wave.

The cross-correlation calculator performs a cross-correlation process on a plurality of tissue Doppler components (n) at the same depth in one scanning line direction. Specifically, the phase difference of the tissue Doppler component is calculated based on the first tissue Doppler component TD (1) and the j-th (2 ≦ j ≦ n) tissue Doppler component TD (j). More specifically, the cross-correlation calculator performs a complex Fourier transform on the complex conjugate product TD (1) × TD ^* (j) of TD (1) and TD (j), thereby obtaining TD (1 ) And TD (j) are calculated. The procedure for calculating this phase difference is repeatedly calculated from j = 2 to j = n. That is, (n−1) phase differences are calculated for each 1 / PRF and for each depth for transmission / reception of n ultrasonic waves in one scanning line direction. The phase difference by the cross-correlation calculator indicates the phase of the jth tissue Doppler component with reference to the first tissue Doppler component. That is, the phase difference output by the cross-correlation calculator indicates the amount of tissue displacement based on the first tissue Doppler component.

  The displacement amount calculation unit 19 calculates the tissue displacement amount obtained by the autocorrelator before transmission of the push pulse (hereinafter referred to as first displacement data) and the tissue obtained by the autocorrelation calculator after transmission of the push pulse. Body movement of the subject based on the amount of tissue displacement (n-th, (n-1) -th, etc.) just before the end of the n-th ultrasound transmission / reception among the above-mentioned displacement amounts (hereinafter referred to as second displacement data) The tissue displacement amount (hereinafter referred to as body motion displacement amount) is approximated for each depth in the second region. The displacement amount calculation unit 19 subtracts the approximate body movement displacement amount from the first and second displacement data, thereby obtaining the displacement amount of the tissue accompanying the propagation of the shear wave (hereinafter referred to as shear wave propagation data). calculate. The shear wave propagation data may be the amount of tissue displacement in the direction away from the ultrasonic probe 3 along the scanning line direction.

  Hereinafter, in order to specifically describe, the number of times of transmission / reception of ultrasonic waves executed for one scanning line in a predetermined area before transmission of push pulses (hereinafter referred to as transmission / reception times before push pulse) is 15 times. And In addition, the number of times of transmission / reception of ultrasonic waves (hereinafter referred to as the number of transmission / reception after a push pulse) n executed for one scanning line in a predetermined region after transmission of a push pulse is 65.

  Specifically, the displacement amount calculation unit 19 corresponds to the first displacement data related to the number of transmission / reception before push pulse (15 times) and the 64th and 65th times among the number of transmission / reception after push pulse (65), respectively. Based on the displacement amount, the temporal change of the body motion displacement amount is approximated by, for example, a second-order polynomial over the transmission / reception period of the ultrasonic waves related to the first and second displacement data. Hereinafter, data representing the temporal change in the amount of body movement displacement is referred to as body movement displacement data. The body movement displacement data is generated for each position in the predetermined area (that is, for each scanning line and depth in the predetermined area). The displacement amount calculation unit 19 calculates shear wave propagation data indicating a temporal change in the displacement amount of the tissue due to the shear wave by subtracting the body movement displacement data from the first and second displacement data. Shear wave propagation data is generated for each position within a predetermined region. The displacement amount calculation unit 19 outputs the shear wave propagation data to the arrival time determination unit 21 described later. The displacement amount calculation unit 19 calculates shear wave propagation data corresponding to each position in the predetermined region by the above processing.

  The arrival time determination unit 21 determines the arrival time of the shear wave that has reached each position in the predetermined region (hereinafter referred to as shear wave arrival time) based on the temporal change of the tissue displacement amount in the shear wave propagation data. . Specifically, the arrival time determination unit 21 sets the maximum value of the displacement amount of the tissue in the shear wave propagation data with respect to each position in the predetermined region, with the push pulse transmission start time or the push pulse transmission end time set to time 0. The time corresponding to is determined as the shear wave arrival time. The arrival time determination unit 21 outputs data relating to the arrival time at each position in the predetermined area (hereinafter referred to as arrival time data) to the image generation unit 23 described later.

  The arrival time determination unit 21 may determine, as the shear wave arrival time, the time corresponding to the maximum time change among the time changes of the tissue displacement amount in the shear wave propagation data. The arrival time determination unit 21 corresponds to the maximum value of the tissue displacement amount in the shear wave propagation data, with the time shifted by a predetermined time with reference to the start of push pulse transmission or the end of push pulse transmission as 0. The time to perform may be determined as the shear wave arrival time.

  The arrival time determination unit 21 may determine the arrival time based on the maximum displacement amount among the maximum values in the temporal change of the tissue displacement amount in the shear wave propagation data. Specifically, the arrival time determination unit 21 extracts the one that takes the maximum value from the temporal change in the amount of tissue displacement in the shear wave propagation data. For example, when the waveform of the shear wave propagation data has a plurality of peaks, there are a plurality of points where the maximum value is obtained. The arrival time determination unit 21 extracts a maximum value having the maximum amount of displacement among these maximum values. The arrival time determination unit 21 determines the arrival time based on the displacement amount of the maximum value.

  The image generation unit 23 includes a digital scan converter (Digital Scan Converter: hereinafter referred to as DSC) and an image memory (not shown). The image generation unit 23 performs coordinate conversion processing (resampling) on the DSC. The coordinate conversion process is, for example, a process for converting a scanning line signal sequence of ultrasonic scanning composed of B-mode data, Doppler data, and arrival time data into a scanning line signal sequence of a general video format represented by a television set It is. The image generation unit 23 generates an ultrasonic image as a display image by coordinate conversion processing. Specifically, the image generator 23 generates a B-mode image based on the B-mode data. The image generation unit 23 generates a Doppler image such as an average speed image, a dispersed image, or a power image based on the Doppler data.

  Based on the arrival time data and an arrival time hue correspondence table stored in the storage unit 27 described later, the image generation unit 23 assigns a hue according to the arrival time at each position in a predetermined area. Is generated. The arrival time hue correspondence table is, for example, a hue correspondence table for arrival time values. For example, the hue when the arrival time is 0 is blue. For example, the hue is defined as the maximum arrival time as red in the order of blue, blue-green, green, yellow-green, yellow, orange, and red as the arrival time increases.

  The image memory stores data (hereinafter referred to as image data) corresponding to the generated ultrasonic image (B-mode image, average velocity image, dispersion image, power image, shear wave arrival image). The image data stored in the image memory is read out according to an operator instruction via the input unit 9 described later. The image memory is, for example, a memory that stores ultrasonic images corresponding to a plurality of frames immediately before freezing. By continuously displaying the images stored in the cine memory (cine display), the ultrasonic moving image can be displayed on the display unit 7 to be described later.

  The image synthesizing unit 25 synthesizes character information and scales of various parameters with the ultrasonic image. The image composition unit 25 outputs the synthesized ultrasonic image to the display unit 7 described later. The image composition unit 25 generates a superimposed image in which the shear wave arrival image is aligned and superimposed on the B-mode image. The image composition unit 23 outputs the generated superimposed image to the display unit 7.

  The storage unit 27 stores various data such as a plurality of reception delay patterns, a plurality of transmission delay patterns, and a plurality of shear wave generation / transmission delay patterns having different focus depths, a control program of the ultrasonic diagnostic apparatus 1, a diagnostic protocol, and transmission / reception conditions. Group, diagnosis information (patient ID, doctor's findings, etc.), received signal generated by the receiving unit 13, B-mode data generated by the B-mode processing unit 15, Doppler data generated by the Doppler processing unit 17, predetermined area 1st, 2nd displacement data, body movement displacement data, shear wave propagation data, arrival time data, arrival time hue correspondence table, B mode image, average velocity image, dispersion image, power image, shear wave arrival at each position Algorithms related to image and shear wave arrival image generation (hereinafter referred to as shear wave arrival image generation algorithm) To 憶. Note that the above-described image memory may be provided in the storage unit 27.

  The interface unit 29 is an interface related to the input unit 9, a network, an external storage device (not shown), and a biological signal measurement unit. Data such as an ultrasound image and analysis results obtained by the apparatus main body 5 can be transferred to another apparatus via the interface unit 29 and the network. The interface unit 29 can also download a medical image related to the subject acquired by another medical image diagnostic apparatus (not shown) via a network.

  The CPU 31 stores data in the storage unit 27 based on the selection of the B mode, the Doppler mode, and the shear wave arrival image display mode input by the operator via the input unit 9, the frame rate, the scanned depth, and the transmission start / end. The stored transmission delay pattern, reception delay pattern, shear wave generation / transmission delay pattern and apparatus control program are read out, and the apparatus body 5 is controlled according to these. For example, the CPU 31 reads the shear wave arrival image generation algorithm from the storage unit 27. The CPU 31 controls the transmission unit 11, the Doppler processing unit 17, the displacement amount calculation unit 19, and the arrival time determination unit 21 according to the read shear wave arrival image generation algorithm. The shear wave arrival image display mode is a mode in which a shear wave arrival image is generated and displayed.

  Specifically, when the shear wave arrival image display mode is input via the input unit 7, the CPU 31 transmits an ultrasonic wave for obtaining the first displacement data in the scanning line direction within the predetermined region. Next, the transmission unit 11 is controlled. The CPU 31 controls the Doppler processing unit 17 to generate the first displacement data.

  Next, the CPU 31 outputs the shear wave generation transmission delay pattern read from the storage unit 27 to the transmission unit 11 in order to generate a push pulse. The CPU 31 controls the transmission unit 11 to transmit ultrasonic waves for obtaining the second displacement data in the scanning line direction within the predetermined area. The CPU 31 controls the Doppler processing unit 17 in order to generate the second displacement data. The CPU 31 controls the displacement amount calculation unit 19 to generate body motion displacement data based on the first and second displacement data. The CPU 31 controls the displacement amount calculation unit 19 to generate shear wave propagation data based on the first and second displacement data and the body movement displacement data. The CPU 31 controls the arrival time determination unit 21 to generate arrival time data based on the shear wave propagation data. The CPU 31 controls the image generation unit 23 to generate a shear wave arrival image based on the arrival time hue correspondence table and the arrival time data read from the storage unit 27.

  The display unit 7 displays an ultrasonic image such as a B-mode image and a Doppler image, a shear wave arrival image, a superimposed image, and the like based on the output from the image synthesis unit 25. Note that the display unit 7 may perform adjustments such as brightness, contrast, dynamic range, and γ correction and color map assignment for the displayed image.

  The input unit 9 is connected to the interface unit 29 and takes various instructions, commands, information, selections, and settings from the operator into the apparatus body 5. The input unit 9 includes input devices such as a trackball, a switch button, a mouse, and a keyboard (not shown). The input device detects the coordinates of the cursor displayed on the display screen, and outputs the detected coordinates to the CPU 31 described later. The input device may be a touch command screen provided to cover the display screen. In this case, the input unit 9 detects coordinates instructed by a touch reading principle such as an electromagnetic induction type, an electromagnetic distortion type, and a pressure sensitive type, and outputs the detected coordinates to the CPU 31. Further, when the operator operates the end button or the freeze button of the input unit 9, the transmission / reception of the ultrasonic waves is ended, and the apparatus main body 5 is temporarily stopped.

  The input unit 9 inputs a region of interest or a predetermined region that the operator focuses on according to an instruction from the operator. The input unit 9 inputs a mode selected by an operator's instruction.

(Displacement observation scanning function)
The displacement amount observation scanning function is a function related to a scanning procedure for acquiring the displacement amount of the tissue accompanying the propagation of the shear wave. Hereinafter, processing related to the displacement amount observation scanning function (hereinafter referred to as displacement amount observation scanning processing) will be described.

  FIG. 2 is a flowchart showing the procedure of the displacement amount observation scanning process. FIG. 3 shows a scanning line (hereinafter referred to as a shear wave generation scanning line) 53 for generating a shear wave and a scanning line related to transmission / reception of ultrasonic waves for observing the displacement amount of the tissue due to the shear wave in the displacement amount observation scanning process. 4 is a schematic diagram schematically showing 54, 55, 56, and 57 (hereinafter referred to as observation scanning lines) together with a region of interest (or a region of interest) 52. FIG.

  Prior to transmitting ultrasonic waves to the subject P, the region of interest 52 is set according to an instruction from the operator via the input unit 9 (step Sa1). At this time, a variable k indicating the observation scanning line number is initialized. Instead of the region of interest 52, a region that the operator is paying attention to may be set. The second ultrasonic wave is transmitted / received a plurality of times (for example, 15 times) with respect to the kth scanning line (for example, 54) in the region of interest 52, and a first reception signal is generated for each transmission / reception of the ultrasonic wave (step) Sa2). Next, a shear wave generation transmission delay pattern is read from the storage unit 27 based on the position of the region of interest 52. A push pulse (first ultrasonic wave) is transmitted to a predetermined scanning line 54 in the vicinity of the region of interest 52 using the read shear wave generation transmission delay pattern (step Sa3). After transmission of the push pulse, ultrasonic waves (second ultrasonic waves) are transmitted / received to / from the kth scanning line (for example, 54) a plurality of times (for example, 65 times), and the second received signal is transmitted and received every time ultrasonic waves are transmitted / received. Is generated (step Sa4). If the first and second received signals are not generated in the entire region of interest, that is, the scanning lines 55 to 57 (step Sa5), k is incremented (step Sa6). Thereafter, the processing from step Sa2 to step Sa4 is repeated.

  The displacement amount observation scanning process transmits / receives ultrasonic waves to each of the plurality of observation scanning lines in the region of interest 52 to generate a first reception signal before transmitting the push pulse, and then transmits the push pulse. This is a process of repeatedly performing ultrasonic transmission / reception to generate a second reception signal after the push pulse transmission. That is, the displacement amount observation scanning process is a scanning process in which ultrasonic transmission / reception with respect to one scanning line is performed with one push pulse. Note that, after transmitting one push pulse, ultrasonic transmission / reception may be performed on a plurality of scanning lines. Further, after transmitting one push pulse, so-called parallel simultaneous reception may be executed in which ultrasonic waves are transmitted once and reception in a plurality of scanning line directions is performed.

(Shear wave arrival image generation function)
The shear wave arrival image generation function is a function of generating a shear wave arrival image that indicates the shear wave arrival time at each position in a predetermined region by hue. Hereinafter, processing related to the shear wave arrival image generation function (hereinafter referred to as shear wave arrival image generation processing) will be described.

FIG. 4 is a flowchart illustrating an example of a procedure of shear wave arrival image generation processing.
Autocorrelation processing is executed using a plurality of first received signals generated before push pulse transmission by transmitting and receiving ultrasonic waves a plurality of times for one scanning line. By the autocorrelation process, first displacement data relating to each position in the predetermined area is generated (step Sb1). Autocorrelation processing is executed using a plurality of second received signals generated after the push pulse transmission by a plurality of times of ultrasonic wave transmission / reception with respect to one scanning line. By the autocorrelation process, second displacement data relating to each position in the predetermined area is generated (step Sb2).

  FIG. 5 is a diagram illustrating an example of a temporal change in the amount of tissue displacement at a position of the region of interest. That is, FIG. 5 is a diagram summarizing the first and second displacement data regarding the position of the region of interest. The horizontal axis in FIG. 5 corresponds to the number of ultrasonic transmissions excluding push pulses. The vertical axis in FIG. 5 indicates the amount of tissue displacement. The amount of tissue displacement with respect to the number of transmissions from 1 to 15 corresponds to the first displacement data. The amount of tissue displacement corresponding to the number of transmissions from 16 to 80 corresponds to the second displacement data. The displacement amount in FIG. 5 is a displacement amount based on the displacement amount of the tissue with respect to the number of times of transmission of the first ultrasonic wave. That is, the displacement amount in FIG. 5 corresponds to the integrated value of the phase difference generated by the autocorrelation process or the phase difference generated by the cross correlation process.

  FIG. 5 shows that the tissue is moving at almost constant speed in one direction (direction approaching the ultrasonic probe 3) due to body movement of the subject. The displacement of the tissue due to the propagation of the shear wave cannot be identified due to the body movement of the subject.

  The body movement displacement amount of the subject is shown based on the tissue displacement amount (n-th, (n-1) -th, etc.) immediately before the end of the n-th ultrasound transmission / reception among the first displacement data and the second displacement data. Body movement displacement data is generated (step Sb3). By subtracting the body movement displacement data from the first and second displacement data, shear wave propagation data indicating a temporal change in the displacement amount of the tissue due to the shear wave is generated (step Sb4). Based on the shear wave propagation data, the shear wave arrival time that has reached each position in the region of interest corresponding to the shear wave propagation data from the shear wave generation position is determined (step Sb5).

  FIG. 6 is a diagram illustrating an example of a temporal change (shear wave propagation data) of the displacement amount obtained by removing the displacement amount due to the body movement of the subject from the displacement amount of the tissue illustrated in FIG. 5. The horizontal axis in FIG. 6 corresponds to the number of ultrasonic transmissions excluding push pulses. The vertical axis in FIG. 6 indicates the amount of tissue displacement. 6 is different from the vertical axis of FIG. That is, the vertical axis in FIG. 6 indicates a direction away from the ultrasonic probe, and is negative opposite to the sign of the vertical axis in FIG. Further, the order of the amount of tissue displacement caused by shear waves is different from the order of the amount of tissue displacement caused by body motion.

  As shown in FIG. 6, the absolute value of the displacement amount of the tissue becomes maximum after the shear wave passes (around the 22nd transmission frequency). In FIG. 6, the arrival time determination unit 21 determines 48 times (number of transmissions) in the figure at which the absolute value of the tissue displacement amount is maximum as the shear wave arrival time. In addition, when determining the time when the temporal change in the displacement amount of the tissue is negative and maximal as the shear wave arrival time, the arrival time determination unit 21 determines the vicinity of the number of transmissions 16 as the shear wave arrival time. .

  FIG. 7 is a diagram illustrating an example of a temporal change in the amount of tissue displacement at a position of a region of interest different from that in FIG. 5. The vertical axis in FIG. 7 indicates the direction away from the ultrasonic probe, and is negative opposite to the sign of the vertical axis in FIG. FIG. 7 shows that the tissue moves in one direction (a direction away from the ultrasonic probe 3) at a substantially constant speed due to the body movement of the subject. The displacement of the tissue due to the propagation of the shear wave cannot be identified due to the body movement of the subject.

  FIG. 8 is a diagram illustrating an example of a temporal change (shear wave propagation data) of the displacement amount obtained by removing the displacement amount due to the body movement of the subject from the displacement amount of the tissue illustrated in FIG. 7. The vertical axis and horizontal axis in FIG. 8 are the same as the vertical axis and horizontal axis in FIG. 6, respectively. FIG. 8 shows a shear wave generated when the amount of tissue displacement due to the shear wave is too small at the position where the shear wave propagation data is obtained, or when the amount of tissue displacement due to the body motion of the subject is irregular. An example of propagation data is shown. The arrival time determination unit 21 determines the vicinity of the transmission count 24 as the shear wave arrival time. The graph of FIG. 8 differs from the graph of FIG. 6 in that the shear wave arrival time is not clear. When shear wave propagation data as shown in FIG. 8 is obtained, for example, the shear wave arrival image has a hue that is significantly different from the surrounding hue.

  Based on the determined shear wave arrival time and arrival time hue correspondence table, a shear wave arrival image to which a hue is assigned according to the shear wave arrival time is generated (step Sb6). The generated shear wave arrival image is superimposed on the B-mode image and displayed on the display unit 7.

  FIG. 9 is a diagram showing an example of the generated shear wave arrival image together with an example of a color map showing a legend of hue corresponding to the shear wave arrival time. FIGS. 9A and 9B are diagrams illustrating an example of a superimposed image in which a shear wave arrival image is superimposed on a B-mode image. The circles in FIGS. 9A and 9B indicate the region of interest (target). (C) of FIG. 9 is a diagram showing a legend of the color maps of (a) and (b) of FIG.

  The region of interest in (a) of FIG. 9 indicates a region having a softer tissue than the periphery of the region of interest. The region of interest in (b) of FIG. 9 indicates a region having a tissue harder than the periphery of the region of interest. 9 (a) and 9 (b), the change in the hue in the azimuth direction (change in light and shade due to the light color) shows how the shear wave propagates from left to right as viewed in the figure. . In FIG. 9A, a mottled pattern (mosaic pattern) is displayed in a region below the region of interest. That is, in FIG. 9A, the region below the region of interest indicates a region where the shear wave arrival time cannot be accurately evaluated as shown in FIG. 8, for example. When comparing (a) of FIG. 9 and (b) of FIG. 9, the hue (shading in the drawing) is shown in FIG. 9 (b) along the azimuth direction in the vicinity of the center of FIG. Compared to sudden changes. For this reason, it is estimated that the propagation speed of the shear wave is low near the center of FIG. 9A, that is, the tissue is softer than the tissue around the region of interest in FIG.

  In the vicinity of the center of FIG. 9B, the hue (light and shade in the figure) changes gradually along the azimuth direction compared to FIG. 9A. For this reason, it is estimated that the propagation speed of the shear wave is high near the center of FIG. 9B, that is, the tissue is harder than the tissue around the region of interest in FIG.

(Modification)
The difference from the first embodiment is that the corrected arrival time is obtained by correcting the shear wave arrival time at each position in the predetermined area with reference to the shear wave arrival time at the specified position specified in the predetermined area by the operator's instruction. And a shear wave arrival correction image in which the hue of the shear wave arrival image is corrected is generated based on the corrected arrival time and the arrival time hue correspondence table. This modification has a process executed in addition to the shear wave arrival image generated according to the first embodiment.

  The input unit 9 inputs a designated position designated by the operator to the apparatus main body 5.

  The arrival time determination unit 21 determines a corrected arrival time by correcting the shear wave arrival time at each position in the predetermined region with reference to the shear wave arrival time at the designated position. Specifically, the arrival time determination unit 21 determines the corrected arrival time at each position by subtracting the shear wave arrival time at the specified position from the shear wave arrival time at each position. The arrival time determination unit 21 outputs the determined corrected arrival time to the image generation unit 23.

  The image generation unit 23 generates a shear wave arrival correction image in which the hue in the shear wave arrival image is corrected based on the corrected arrival time and the arrival time hue correspondence table. Specifically, the image generation unit 23 determines the hue corresponding to the value of the corrected arrival time at each position using the arrival time hue correspondence table. The image generation unit 23 generates a shear wave arrival correction image by changing the hue at each position of the shear wave arrival image to a hue corresponding to the correction arrival time.

  The image synthesis unit 25 updates the shear wave arrival image superimposed on the B-mode image to the shear wave arrival correction image, thereby generating a corrected superimposed image in which the hue of the superimposed image is corrected.

  The display unit 7 replaces the displayed shear wave arrival image with the shear wave arrival correction image and displays it. In addition, when displaying the superimposed image, the display unit 7 may replace the displayed superimposed image with the corrected superimposed image for display.

(Shear wave arrival correction image generation function)
The shear wave arrival correction image generation function determines the corrected arrival time by correcting the shear wave arrival time at each position in the specified area based on the shear wave arrival time at the specified position, and supports the corrected arrival time and arrival time hue. This is a function for generating a shear wave arrival correction image in which the hue of the shear wave arrival image is corrected based on the table. Hereinafter, processing related to the shear wave arrival correction image generation function (hereinafter referred to as shear wave arrival correction image generation processing) will be described.

  FIG. 10 is a flowchart illustrating an example of a procedure of shear wave arrival correction image generation processing.

  A designated position (or designated region) is input in accordance with an operator's instruction within the region of interest of the shear wave arrival image displayed on the display unit 7 (step Sc1). The designated position may be a point or a line segment. The line segment as the designated position is, for example, a line segment that passes through the position designated in the region of interest by an instruction from the operator and is parallel to the scanning line. Based on the shear wave arrival time at the designated position, a corrected arrival time obtained by correcting the shear wave arrival time at each position is determined (step Sc2). The arrival time hue correspondence table is read from the storage unit 27. Based on the read arrival time hue correspondence table and the corrected arrival time, a shear wave arrival correction image in which the hue in the shear wave arrival image is corrected is generated (step Sc3).

  FIG. 11 is a diagram illustrating the shear wave arrival correction image together with the shear wave arrival image. FIG. 11A is a diagram showing a shear wave arrival image generated in the first embodiment. FIG. 11B is a diagram illustrating a shear wave arrival correction image generated in the present modification. In FIG. 11, the shear wave propagates from the left to the right as viewed in the drawing. A circular region 91 in FIG. 11 indicates a region where the shear rate is faster than the surrounding tissue. A circular region 92 in FIG. 11 indicates a region where the shear rate is slower than that of the surrounding tissue.

  In FIG. 11A, for example, when a shear wave arrival correction image is displayed by paying attention to a circular region 92, a line segment 90 (that is, a shear wave) serving as a reference for the shear wave arrival time is input via the input unit 9. The position where the arrival time is zero) is input. The arrival time determination unit 21 subtracts the shear wave arrival time at the same depth position on the line segment 90 (hereinafter referred to as a reference line segment) from the shear wave arrival time at the same depth position in the ROI. The arrival time determination unit 21 determines the corrected arrival time by executing the difference for each depth in the ROI. When the arrival time becomes negative, the arrival time determination unit 21 sets the corrected arrival time to zero. The image generation unit 23 generates a shear wave arrival correction image in which the hue of the shear wave arrival image is corrected based on the corrected arrival time and the arrival time hue correspondence table.

  FIG. 11B is a diagram illustrating an example of a shear wave arrival correction image obtained by correcting the hue of the shear wave arrival image of FIG. 11A based on the shear wave arrival time on the reference line segment. As shown in FIG. 11B, in the region 92, the hue in the azimuth direction (light and shade in the figure) changes abruptly. That is, FIG. 11B shows that the propagation speed of the shear wave in the region 92 is slower than the peripheral region of the region 92.

According to the configuration described above, the following effects can be obtained.
According to the ultrasonic diagnostic apparatus 1 of the present embodiment, based on the time variation of the tissue variable obtained by removing the tissue displacement due to the body movement of the subject, according to the shear wave arrival time at each position in the region of interest. A shear wave arrival image to which a hue is assigned can be generated. Thereby, the propagation state (for example, refraction, reflection, etc.) of the shear wave generated in the subject can be visualized as one image. As a result, the operator cannot accurately determine the shear wave arrival time due to the fact that the displacement of the mottled pattern area in the shear wave arrival image cannot be accurately removed due to the body movement of the subject. It can be used as a judgment material for judging that it is. Further, the operator can exclude the mottled pattern region from the processing object for determining the propagation speed of the shear wave and the evaluation object for evaluating the hardness of the tissue in the shear wave arrival image. .

  Further, according to the ultrasonic diagnostic apparatus 1 of the present embodiment, a value having the maximum displacement amount is extracted from the maximum value of the temporal change of the tissue displacement amount after removing the tissue displacement amount due to the body movement of the subject. Then, the arrival time is determined based on the displacement amount of the local maximum value, and a shear wave arrival image in which the hue is assigned according to the shear wave arrival time at each position in the region of interest can be generated. Thereby, for example, in the displacement amount observation scanning process, an appropriate arrival time can be determined even when at least one of the ultrasonic probe and the subject moves. That is, when the entire movement occurs continuously, the apparent amount of tissue displacement may monotonously increase with time (number of transmissions). If the maximum amount of displacement is simply extracted at this time, if the rate of monotonic increase is large, the value increased by the monotonous increase is extracted as the maximum amount of displacement. However, using the displacement amount increased by monotonous increase means that the arrival time is calculated using the displacement amount at the time when the entire movement occurs, and as a result, the physically incorrect arrival time is determined. Therefore, the maximum value obtained by the monotonic increase described above is used by extracting the value having the maximum displacement amount from the maximum value and determining the arrival time based on the displacement amount of the maximum value. Instead, it is possible to use a displacement amount at an appropriate time point to determine the arrival time. This improves the robustness in determining the arrival time.

  From the above, according to the present embodiment, the operator can observe the propagation state of the shear wave by one shear wave arrival image without observing the image obtained by visualizing the displacement amount at each time as a moving image. I can grasp it. In addition, the operator observes the degree of hue change in the azimuth direction (slowness of hue change) in the shear wave arrival image, so that the propagation speed of the shear wave at each position in the predetermined region, that is, the tissue at each position. Can be qualitatively grasped.

  Further, according to the modification of the present embodiment, the shear wave arrival correction image in which the hue of the shear wave arrival time is corrected with reference to the shear wave arrival time at the specified position input by the operator via the input unit 9. Can be generated. Thereby, even when the region of interest focused by the operator is away from the shear wave generation position, the state of the shear wave propagating through the region of interest can be easily displayed. In addition, according to the modification of the present embodiment, a position that is a reference for the shear wave arrival time can be designated as a line segment. As a result, even if the wave front of the shear wave is disturbed due to nonuniform shear wave propagation speed or refraction of the shear wave before the shear wave reaches the target area, the wave front disturbance is initialized in the target area. can do. As a result, the state of shear wave propagation in the region of interest can be displayed intuitively and easily for the operator.

(Second Embodiment)
The difference from the first embodiment is that the shear wave propagation speed at each position in the predetermined area is calculated using the shear wave arrival time at each position in the predetermined area (region of interest), and the calculated propagation speed is calculated. It is to generate a shear wave propagation velocity image to which a hue is assigned according to the above.

FIG. 12 is a configuration diagram illustrating an example of a configuration of an ultrasonic diagnostic apparatus according to the second embodiment.
The velocity calculation unit 22 calculates the shear wave propagation velocity at each position in the predetermined region using the shear wave arrival time (arrival time data) at each position in the predetermined region. Specifically, the velocity calculation unit 22 calculates a difference in shear wave arrival times (hereinafter referred to as arrival time difference) at positions adjacent to each other at each position in the predetermined region. In addition, the speed calculation unit 22 calculates the distance between adjacent positions at the same time. Next, the velocity calculation unit 22 calculates the product of the reciprocal of the arrival time difference at each position in the predetermined region and the distance between adjacent positions as the shear wave propagation velocity. The velocity calculation unit 22 outputs shear wave propagation velocity data (hereinafter referred to as propagation velocity data) at each position in the predetermined region to the image generation unit 23.

  Based on the propagation velocity data and the propagation velocity hue correspondence table stored in the storage unit 27, the image generation unit 23 assigns a hue according to the propagation velocity of the shear wave at each position in a predetermined region. Generate speed images. The propagation velocity hue correspondence table is, for example, a hue correspondence table with respect to propagation velocity values. For example, the hue when the propagation speed is 0 is blue. For example, the hue is defined as red with a maximum propagation speed in the order of blue, blue-green, green, yellow-green, yellow, orange, and red as the propagation speed increases.

  The image composition unit 25 generates a propagation velocity superimposed image in which the shear wave propagation velocity image is aligned and superimposed on the B-mode image. The image composition unit 25 outputs a propagation velocity superimposed image or a shear wave propagation velocity image to the display unit 7.

  The storage unit 27 includes propagation velocity data, propagation velocity hue correspondence table, shear wave propagation velocity image, propagation velocity superimposed image, algorithm relating to generation of shear wave propagation velocity image (hereinafter referred to as shear wave propagation velocity image generation algorithm), and the like. Remember.

  Based on the selection of the shear wave propagation velocity image display mode input by the operator via the input unit 9, the CPU 31 transmits the transmission delay pattern, reception delay pattern, shear wave generation transmission delay pattern, and the like stored in the storage unit 27. The apparatus control program is read out, and the apparatus main body 5 is controlled according to these. For example, the CPU 31 reads out a shear wave propagation velocity image generation algorithm from the storage unit 27. The CPU 31 controls the velocity calculation unit 22, the image generation unit 23, and the like according to the read shear wave propagation velocity image generation algorithm. The shear wave propagation velocity image display mode is a mode in which a shear wave propagation velocity image is generated and displayed.

  Specifically, when the shear wave propagation velocity image display mode is input via the input unit 9, the CPU 31 controls the velocity calculation unit 22 to generate propagation velocity data based on the arrival time data. . The CPU 31 controls the image generation unit 23 to generate a shear wave propagation velocity image based on the propagation velocity data and the propagation velocity hue correspondence table read from the storage unit 27.

  The display unit 7 displays a shear wave propagation velocity image, a propagation velocity superimposed image, and the like based on the output from the image synthesis unit 25.

(Shear wave propagation velocity image generation function)
The shear wave propagation velocity image generation function is a function of generating a shear wave propagation velocity image indicating the propagation velocity of the shear wave at each position in a predetermined region (second region) with a hue. Hereinafter, processing related to the shear wave propagation velocity image generation function (hereinafter referred to as shear wave propagation velocity image generation processing) will be described.

  FIG. 13 is a flowchart illustrating an example of a procedure of shear wave propagation velocity image generation processing.

  Based on the shear wave arrival time at each position in the predetermined region, the propagation speed of the shear wave at each position is calculated (step Sd1). Based on the propagation velocity at each position and the propagation velocity hue correspondence table, a shear wave propagation velocity image in which a hue is assigned according to the propagation velocity of the shear wave is generated at each position in the predetermined region (step Sd2).

(First modification)
The difference from the second embodiment is that the average propagation velocity of the shear wave in the designated region designated in the predetermined region by the operator's instruction (hereinafter referred to as the average propagation velocity in the region) is calculated, and the average in the region is calculated. It is to display the propagation speed.

  The input unit 9 inputs a designated area designated within the predetermined area by the operator to the apparatus main body 5.

  The velocity calculation unit 22 calculates the average propagation velocity in the region based on the shear wave arrival time at each position in the designated region and the distance from the shear wave generation position to each position in the designated region. For example, the velocity calculation unit 22 performs linear regression based on a plurality of shear arrival times at positions of the same depth on different scanning lines in the specified region and the distances from the shear wave generation position to each position. Calculate the average propagation velocity in the region by analysis.

  The image generation unit 23 generates an image that displays the average propagation velocity in the region together with the shear wave arrival image.

  FIG. 14 is a diagram in which shear wave propagation data at each position at the same depth on four different scanning lines in the designated region is plotted with the amount of displacement on the vertical axis and the time on the horizontal axis. Curves 64, 65, 66, and 67 in FIG. 14 show shear wave propagation data at the same depth on the scanning line as a term. Curves 64, 65, 66, and 67 in FIG. 14 correspond to, for example, the scanning lines 54, 55, 56, and 57 in FIG. The arrival time determination unit 21 sets the time of the maximum value in the direction away from the ultrasonic probe (negative displacement amount in FIG. 14) as the shear wave arrival time for each of the curves 64, 65, 66, and 67 in FIG. decide.

  FIG. 15 is a diagram illustrating an example of the relationship of the distance from the shear wave generation position to the shear wave arrival time. A point 74 in FIG. 15 indicates the distance from the shear wave generation position with respect to the shear wave arrival time determined for the curve 64 in FIG. A point 75 in FIG. 15 indicates the distance from the shear wave generation position with respect to the shear wave arrival time determined for the curve 65 in FIG. A point 76 in FIG. 15 indicates the distance from the shear wave generation position with respect to the shear wave arrival time determined for the curve 66 in FIG. A point 77 in FIG. 15 indicates the distance from the shear wave generation position with respect to the shear wave arrival time determined for the curve 67 in FIG. A straight line 78 in FIG. 15 is an approximate straight line determined by linear regression analysis using the points 74, 75, 76, and 77. The speed calculation unit 21 calculates the slope of the straight line by linear regression analysis as the average propagation speed within the region.

(Second modification)
The difference from the first modified example in the second embodiment is that the average elastic modulus in the designated region is calculated using the calculated average propagation velocity in the region.

The velocity calculation unit 22 calculates an average elastic modulus (Young's modulus) using the calculated in-region average propagation velocity. Specifically, the velocity calculation unit 22 multiplies the square (v _s ² ) of the average propagation velocity in the region (v _s (m / s)) by three times (3 × v _s ² ), thereby obtaining an average elastic modulus. (E (kPa)) is calculated. That is, the formula calculated by the speed calculation unit 22 is E = 3 × v _s ² .

  The image generation unit 23 generates an image for obtaining an average elastic modulus together with the shear wave arrival image.

  The display unit 7 displays an image for obtaining the average elastic modulus together with the shear wave arrival image.

According to the configuration described above, the following effects can be obtained.
According to the ultrasonic diagnostic apparatus 1 of the present embodiment, the propagation speed of the shear wave at each position in the predetermined region is calculated using the shear wave arrival time at each position in the predetermined region (region of interest). It is possible to generate a shear wave propagation velocity image to which a hue is assigned according to the propagation velocity. Thereby, the spatial distribution of the propagation speed of the shear wave generated in the subject can be visualized. Further, the operator can determine that the propagation of the shear wave is not well captured in a region where the propagation speed of the shear wave is noisy. In addition, on the shear wave arrival image, the area where the shear wave propagates or the area where the shear wave propagation is accurately captured is designated as the area for analyzing the average propagation velocity and average elastic modulus of the shear wave. The mean propagation velocity and mean modulus of shear waves can be calculated. Thereby, the reliability with respect to quantitative analysis results, such as the average propagation velocity and average elastic modulus of a shear wave, can be improved.

  Further, as a modification of the first embodiment, when the medical idea of the ultrasonic diagnostic apparatus 1 is realized by the medical image processing apparatus 100, for example, it has constituent elements in dotted lines in the configuration diagram of FIG. It becomes. The medical image processing apparatus 100 can also store the first and second displacement data in the storage unit 27 and execute the subsequent processing. At this time, the displacement amount calculation unit 19 becomes unnecessary. The medical image processing apparatus 100 can also store the shear wave propagation data in the storage unit 27 and execute the subsequent processing. At this time, the displacement amount calculation unit 19 and the arrival time determination unit 21 are not necessary.

  As a modification of the second embodiment, when the technical idea of the ultrasonic diagnostic apparatus 1 is realized by the medical image processing apparatus 101, for example, it has constituent elements in dotted lines in the configuration diagram of FIG. It becomes. The medical image processing apparatus 101 can also read the shear wave arrival image data output from the ultrasound diagnostic apparatus 1 and execute the above-described processing.

(Third embodiment)
The difference from the first and second embodiments is that the number of push pulses transmitted corresponding to each of the plurality of observation scanning lines is executed a plurality of times. As a specific example, a case where a plurality of push pulses are transmitted to a plurality of focal points having different depths in the first region will be described.

  The transmitter 11 transmits a plurality of push pulses respectively corresponding to a plurality of focal points having different depths in the first region. By transmitting a plurality of push pulses, shear waves are generated at each of the plurality of focal points. In the second region, a superimposed shear wave in which shear waves generated at a plurality of focal points are superimposed is propagated. For example, the transmission unit 11 transmits push pulses to four focal points having different depths in the first region. Specifically, in step Sa3 in FIG. 2, the transmission unit 11 transmits a push pulse to each of the four focal points.

  The second displacement data obtained by the auto-correlator or the cross-correlator of the Doppler processing unit 17 has a tissue displacement amount due to the superimposed shear wave.

  The displacement amount calculation unit 19 calculates superimposed shear wave propagation data indicating a temporal change in the displacement amount of the tissue due to the superimposed shear wave by subtracting the body movement displacement data from the first and second displacement data.

  The arrival time determination unit 21 determines the shear wave arrival time based on the temporal change of the tissue displacement amount in the superimposed shear wave propagation data. Specifically, the arrival time determination unit 21 sets the superimposed shear wave for each position in the predetermined region with the time 0 as the start of transmission of any one push pulse or the end of transmission of any one push pulse. The time corresponding to the maximum tissue displacement amount in the propagation data is determined as the shear wave arrival time. The arrival time determination unit 21 outputs arrival time data at each position in the predetermined area to the image generation unit 23. The reference time of the shear wave arrival time can be arbitrarily selected at the transmission start time or transmission end time of any push pulse.

According to the configuration described above, the following effects can be obtained.
According to the ultrasonic diagnostic apparatus 1 of the present embodiment, the arrival of the shear wave of the superimposed shear wave at each position in the region of interest based on the temporal change of the tissue variable obtained by removing the tissue displacement due to the body movement of the subject. It is possible to generate a shear wave arrival image to which a hue is assigned according to time. Thereby, the propagation state (for example, refraction, reflection, etc.) of the shear wave generated in the subject can be visualized as one image.

  The ultrasonic diagnostic apparatus connected to the medical image processing apparatuses 100 and 101 via a network may perform data acquisition and storage in the ultrasonic examination. The medical image processing apparatuses 100 and 101 can be used to observe a shear wave arrival image in detail after ultrasonic examination. That is, when the examiner who performs the ultrasonic examination is different from the analyst who analyzes the medical image generated by the ultrasonic diagnostic apparatus, the effect of this embodiment appears. That is, the analyst can confirm whether the shear wave is propagating as desired by the analyst by the shear wave arrival image after the ultrasonic inspection. The analyst can calculate the elastic modulus of the tissue in the predetermined region based on the shear wave arrival image. For this reason, for example, the reliability of the elastic modulus that is the analysis result can be improved. In addition, it is possible to avoid a situation in which the analysis range is determined by the subjectivity of the examiner, and to reduce the possibility of misdiagnosis.

  In addition, each function according to the embodiment can also be realized by installing a program for executing the processing in a computer such as a workstation and developing the program on a memory. At this time, a program capable of causing the computer to execute the technique can be stored and distributed in a storage medium such as a magnetic disk (such as a hard disk), an optical disk (such as a CD-ROM or DVD), or a semiconductor memory. .

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Ultrasonic diagnostic apparatus, 3 ... Ultrasonic probe, 5 ... Apparatus main body, 7 ... Display part, 9 ... Input part, 11 ... Transmission part, 13 ... Reception part, 15 ... B mode process part, 17 ... Doppler process part , 19 ... displacement amount calculation unit, 21 ... arrival time determination unit, 22 ... speed calculation unit, 23 ... image generation unit, 25 ... image synthesis unit, 27 ... storage unit, 29 ... interface unit, 31 ... control processor (CPU) , 100 ... medical image processing apparatus, 101 ... medical image processing apparatus

Claims (12)

An ultrasonic probe having a plurality of transducers;
A transmission unit that transmits a first ultrasonic wave that generates a shear wave in the subject to the first region and transmits a second ultrasonic wave to the second region in the subject via the ultrasonic probe; ,
A receiving unit that generates a reception signal based on the second ultrasonic wave;
Using the received signal, a displacement amount calculation unit that calculates the displacement amount of the tissue accompanying the propagation of the shear wave to the second region,
An arrival time determination unit for determining an arrival time at which the shear wave arrives at each position based on a change in the displacement amount with respect to each position in the second region;
Based on the arrival time and a hue set in advance according to the arrival time, an image generator that generates a shear wave arrival image to which the hue is assigned according to the arrival time;
An ultrasonic diagnostic apparatus comprising: The arrival time determination unit determines the arrival time based on a maximum displacement amount among the displacement amounts;
The ultrasonic diagnostic apparatus according to claim 1. The arrival time determination unit determines the arrival time based on the maximum displacement amount among the maximum values in the time variation of the displacement amount,
The ultrasonic diagnostic apparatus according to claim 1. The arrival time determination unit determines the arrival time based on a maximum time change among the time changes of the displacement amount;
The ultrasonic diagnostic apparatus according to claim 1. The displacement calculator calculates a displacement amount along a direction away from the ultrasonic probe as the displacement amount;
The ultrasonic diagnostic apparatus according to any one of claims 1 to 4, wherein: An input unit for inputting a designated area designated by an operator in the second area;
The arrival time determination unit determines a corrected arrival time by correcting the arrival time at each position on the basis of the arrival time in the designated region,
The image generation unit generates a shear wave arrival correction image in which the hue in the shear wave arrival image is corrected based on the correction arrival time and the hue;
The ultrasonic diagnostic apparatus according to any one of claims 1 to 5, wherein: Using the arrival time at each position, further comprising a velocity calculation unit for calculating the propagation velocity of the shear wave at each position;
The image generation unit generates a shear wave propagation velocity image in which the hue is assigned according to the propagation velocity at each position based on the calculated propagation velocity and a hue preset according to the propagation velocity. What happens,
The ultrasonic diagnostic apparatus according to claim 1, wherein: An input unit for inputting a designated area designated by an operator in the second area;
A speed calculator that calculates a propagation speed of a shear wave propagating in the designated area using the arrival time at each position in the designated area;
The ultrasonic diagnostic apparatus according to claim 1, wherein: An input unit for inputting a designated area designated by an operator in the second area;
Using a velocity of shear wave propagating in the designated region, further comprising a velocity calculation unit for calculating an elastic modulus in the designated region;
The ultrasonic diagnostic apparatus according to claim 1, wherein: A storage unit for storing received signals;
Using the received signal, a displacement amount calculation unit that calculates the displacement amount of the tissue due to the shear wave propagated to each position in the subject, and
An arrival time determination unit that determines an arrival time at which the shear wave arrives at each position, based on a change in the displacement amount with respect to each position.
Based on the arrival time and a hue set in advance according to the arrival time, an image generator that generates a shear wave arrival image to which the hue is assigned according to the arrival time;
A medical image processing apparatus comprising: Memorize the received signal,
Using the received signal, calculate the amount of tissue displacement due to shear waves propagated to each position in the subject,
Based on the change over time of the displacement amount for each position, determine the arrival time when the shear wave reaches each position;
Generating a shear wave arrival image to which the hue is assigned according to the arrival time, based on the arrival time and a hue preset according to the arrival time;
A medical image processing method comprising: On the computer,
Memorize the received signal,
Using the echo signal, the amount of tissue displacement due to shear waves propagated to each position in the subject is calculated,
Based on the change over time of the displacement amount for each position, the arrival time at which the shear wave reaches each position is determined,
Generating a shear wave arrival image to which the hue is assigned according to the arrival time, based on the arrival time and a hue preset according to the arrival time;
A medical image processing program comprising:

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