JP6731321B2 - Ultrasonic diagnostic equipment - Google Patents

Description

The present invention relates to an ultrasonic diagnostic apparatus, and particularly to a technique for measuring shear waves.

2. Description of the Related Art There is known an ultrasonic diagnostic apparatus that measures a displacement of a tissue in a subject and obtains diagnostic information from the subject. For example, ultrasonic waves are transmitted to generate a shear wave in the subject, the displacement of the tissue accompanying the propagation of the shear wave is measured by the ultrasonic wave, and the shear wave propagation velocity etc. is used to measure the inside of the subject. It is possible to obtain diagnostic information such as the hardness of the tissue.

For example, Patent Document 1 discloses an invention in which the displacement of a shear wave is measured at a plurality of different positions and the propagation velocity of the shear wave is calculated based on the time when the maximum displacement is obtained at each position. ..

U.S. Pat. No. 8,118,744

The propagation characteristics (propagation velocity, etc.) of shear waves vary depending on the site within the subject. Therefore, when the measurement conditions such as the position at which the ultrasonic wave for shear wave generation is transmitted are constant, the reliability of the measured values may decrease depending on the site inside the subject.

Further, it is difficult to judge whether or not the measured value is a reliable value by simply displaying the measured value such as the propagation velocity of the shear wave in the tissue obtained by using ultrasonic waves. For example, when the propagation velocity of the shear wave is measured for each depth at multiple depths in the subject, that is, when multiple propagation velocities corresponding to the multiple depths are obtained, those multiple propagation velocities It is difficult to judge whether the variation is a reliable variation that reflects the tissue property for each depth or a variation with low reliability due to instability of the measurement state.

The present invention has been made in view of the background circumstances described above, and an object thereof is to improve the reliability of the measured values of shear waves measured using ultrasonic waves.

The present invention transmits a push wave of an ultrasonic wave to generate a shear wave in a subject, and transmits a two tracking waves of ultrasonic waves having different transmission positions with respect to the subject, and a transmitting unit. A shear wave measuring unit that measures the propagation velocity of the shear wave based on the received signals obtained according to the two tracking waves, and a threshold range for the propagation velocity of the shear wave are set according to a user operation. a threshold range setting unit, a PT distance between the position where the position of the push-wave is transmitted, the closer to the push waves of two of said tracking wave is transmitted, the upper limit of the threshold range And a control unit that adjusts based on the above.

According to the present invention, the threshold range for the measurement value of the propagation velocity of the shear wave is set according to the user's operation, and the positional relationship between the push wave and the tracking wave is adjusted according to the threshold range. The threshold range is set, for example, as a range in which the reliability of the measured value of the shear wave propagation velocity is guaranteed. The value that can be taken by the propagation velocity of the shear wave generally tends to fall within a certain range clinically depending on the tissue or the like to be diagnosed. Therefore, for example, the user sets a threshold range based on a large number of clinical results, etc., and the measured value of the propagation velocity outside the threshold range is regarded as a result of low reliability, and the measured value should not be adopted. May be That is, the measured value may be rejected. When measuring the propagation velocity of a shear wave using a push wave and a tracking wave, the reliability of the measured value may decrease depending on the positional relationship of these ultrasonic waves. For example, when the shear wave propagation velocity is too high, when the measurement by the tracking wave is started after the push wave is transmitted, the shear wave has already passed the position where the tracking wave is transmitted, and the measurement is not performed. It may be possible. According to the present invention, the positional relationship between the push wave and the tracking wave is appropriately set, and the reliability of the measurement value of the propagation velocity of the shear wave is guaranteed.

Desirably, the control unit stores an inter-PT distance determination table in which an upper limit value of the threshold range and a target value of the inter-PT distance are associated with each other, and with reference to the inter-PT distance determination table, the obtains the target value corresponding to the upper limit of the threshold value range, and controls the transmitting unit, close the PT distance to the target value, or Ru to match the PT distance to the target value. Desirably, the control unit calculates a target value function for obtaining a target value of the PT distance by giving an upper limit value of the threshold range, and obtains the target value corresponding to the upper limit value of the threshold range. , The wave transmitter is controlled to bring the PT distance closer to the target value, or to make the PT distance match the target value. Preferably, the position adjusting unit increases the distance between the push wave and the tracking wave as the upper limit of the threshold range increases.

The present invention transmits a push wave of an ultrasonic wave to generate a shear wave in a subject, and a wave sending unit that sends a tracking wave of the ultrasonic wave to the subject, and a tracking unit according to the tracking wave. By measuring the propagation characteristics of the shear wave based on the received signal obtained, a shear wave measuring unit to obtain a measurement value sequence including measurement values for each depth in the plurality of depths in the subject, and the A threshold range setting unit that sets a threshold range for measured values of shear waves according to a user operation, and a plurality of measured value sequences obtained by performing the measurement of the shear waves a plurality of times, the threshold range a measurement processing unit for identifying the external measurements were closed, the threshold range setting unit includes an operation unit, a control unit, a display processing unit, a display unit, the display processing unit, said Any one of a plurality of diagnostic parts of the subject is displayed on the display unit with an operation graphic for selecting by operation on the operation unit, and the control unit is the diagnosis selected by operation on the operation graphic. It is characterized in that the threshold range is set based on information stored in advance for a part .

According to the present invention, the threshold value range of the shear wave is set according to the user's operation, and the measurement value outside the threshold value range is specified from the plurality of measurement value sequences obtained by performing the shear wave measurement a plurality of times. To be done. The threshold range is set, for example, as a range in which the reliability of measured values such as shear wave propagation velocity is guaranteed. The value that can be taken as the measurement value of the propagation characteristics of the shear wave generally tends to fall within a certain range clinically depending on the tissue to be diagnosed and the like. Therefore, for example, the user sets a threshold value range based on a large number of clinical results, and regarding a measurement value outside the threshold value range, it is considered that the result is unreliable, and the measurement value may not be adopted. Good.

Desirably, an input field for inputting an upper limit value or a lower limit value of the threshold range is displayed on the display unit together with the operation figure, and the control unit inputs a value to the input field by an operation on the operation unit. In this case, the threshold range is set based on the value input in the input field .

Preferably, the threshold value range setting unit sets at least one of an upper limit value and a lower limit value of the threshold value range based on a value input in the input field by an operation on the operation unit .

Desirably, it is a rejection condition for the measured value of the shear wave, including a condition setting unit for setting a rejection condition including the threshold range as a condition, the measurement value processing unit configures the plurality of measurement value string A reliability evaluation value for the plurality of measured values is obtained based on the plurality of measured values and the rejection condition.

ADVANTAGE OF THE INVENTION According to this invention, the reliability of the measured value of the shear wave measured using ultrasonic waves can be improved.

It is a figure showing the whole ultrasonic diagnostic equipment composition suitable for operation of the present invention. It is a figure for explaining a concrete example concerning generation of a shear wave and measurement of displacement. It is a figure which shows the specific example of a spatiotemporal map. It is a figure which shows notionally the process which measures a phase displacement. It is a figure which shows notionally the process which measures a phase displacement. It is a figure which shows the specific example of fluctuation. It is a figure for explaining a concrete example of detection of fluctuation. It is a figure which shows the specific example of the measurement result of a measurement set. It is a figure for explaining a concrete example of a rejection condition. It is a figure which shows the example of an organ selection image. It is a figure which shows the example of a threshold range preset image. It is a figure which shows the specific example of the histogram regarding propagation velocity Vs. It is a figure which shows the specific example of a display image.

FIG. 1 is a diagram showing an overall configuration of an ultrasonic diagnostic apparatus suitable for implementing the present invention. The probe 10 is an ultrasonic probe that transmits and receives ultrasonic waves to and from a region in a subject (living body) including a diagnostic target such as an organ. The probe 10 includes a plurality of vibration elements, each of which transmits and receives ultrasonic waves or transmits ultrasonic waves. The transmitting unit 12 and the probe 10 have a function as a transmitting unit that transmits an ultrasonic wave, and the plurality of vibrating elements are controlled by the transmitting unit 12 to form a transmission beam.

The probe 10 and the receiving unit 14 also have a function as a wave receiving unit that receives ultrasonic waves. That is, the plurality of vibrating elements included in the probe 10 receive ultrasonic waves from the region including the diagnosis target, the signals obtained by this are output to the receiving unit 14, and the receiving unit 14 forms a reception beam. Received signals (echo data) are collected along the receive beam. It should be noted that the probe 10 may be, for example, a linear type although a convex type is desirable.

The probe 10 has a function of transmitting an ultrasonic wave (push wave) that generates a shear wave in a region including a tissue to be diagnosed, and transmits and receives an ultrasonic wave (tracking wave) that measures displacement of the tissue due to the shear wave. And the function of transmitting and receiving ultrasonic waves for image formation.

The transmission of ultrasonic waves is controlled by the transmitter 12. When the shear wave is generated, the transmission unit 12 outputs the push wave transmission signal to the plurality of vibrating elements included in the probe 10, whereby a push wave transmission beam is formed. Further, when measuring the shear wave, the transmitter 12 outputs the transmission signal of the tracking wave to the plurality of vibrating elements included in the probe 10, whereby a transmission beam of the tracking wave is formed. Further, when forming an ultrasonic image, the transmission unit 12 outputs a transmission signal for image formation to a plurality of vibrating elements included in the probe 10, whereby a transmission beam for image formation is formed.

Further, the receiving unit 14 forms a reception beam of the tracking wave based on the reception signal obtained from the plurality of vibrating elements by the probe 10 transmitting and receiving the tracking wave, and obtains the reception signal corresponding to the reception beam. .. Further, the reception unit 14 forms a reception beam for image formation based on the reception signals obtained from the plurality of vibrating elements by the probe 10 transmitting and receiving ultrasonic waves for image formation, and responds to the reception beam. Generate a received signal.

An ultrasonic beam for image formation (a transmission beam and a reception beam) is scanned in a two-dimensional plane including a diagnosis target, and a received signal for image formation is collected from within the two-dimensional plane. Of course, the ultrasonic beam for image formation may be three-dimensionally scanned in the three-dimensional space, and the received signal for image formation may be collected from the three-dimensional space.

The image forming unit 20 forms ultrasonic image data based on the reception signals for image formation collected by the receiving unit 14. The image forming unit 20 forms image data of a B-mode image (tomographic image) of a region including a tissue such as an organ to be diagnosed. In addition, when the received signals for image formation are three-dimensionally collected, the image forming unit 20 may form image data of a three-dimensional ultrasonic image.

The displacement measuring unit 30 measures the displacement of the tissue in the subject after the generation of the shear wave, based on the reception signal corresponding to the reception beam of the tracking wave obtained from the reception unit 14. The fluctuation detection unit 40 detects a periodic displacement based on the displacement measurement result obtained from the displacement measurement unit 30. The shear wave velocity calculation unit 50 calculates the propagation velocity of the shear wave in the subject based on the measurement result obtained from the displacement measurement unit 30. The velocity evaluation unit 60 evaluates the propagation velocity calculated by the shear wave velocity calculation unit 50. In the evaluation, the detection result obtained from the fluctuation detection unit 40 is also referred to. The processing in the displacement measuring unit 30, the fluctuation detecting unit 40, the shear wave velocity calculating unit 50, and the velocity evaluating unit 60 will be described in detail later.

The display processing unit 70 includes image data of an ultrasonic image obtained from the image forming unit 20, velocity information obtained by the shear wave velocity calculating unit 50, measurement results obtained by the displacement measuring unit 30, and evaluation obtained by the velocity evaluating unit 60. A display image is formed based on at least one of the result and the information about the control output from the control unit 80. The display image formed by the display processing unit 70 is displayed on the display unit 72.

The control unit 80 totally controls the inside of the ultrasonic diagnostic apparatus shown in FIG. The operation unit 82 includes, for example, a mouse, a keyboard, a trackball, a touch panel, and other switches. Then, the overall control by the control unit 80 also reflects the instruction issued from the operation unit 82 in response to the user's operation.

The operation unit 82, the control unit 80, the display processing unit 70, and the display unit 72 may form a touch panel. In this case, the operation unit 82 includes a sensor panel that detects the position of the user's finger by changing the electrostatic capacitance or the like. This sensor panel is overlaid on the screen of the display unit 72. The control unit 80 controls the display processing unit 70 to display operation figures such as buttons and icons on the display section 72, and when the sensor panel detects that the user's finger touches the position corresponding to the operation figure, , Execute the process corresponding to the operation figure.

Of the configuration (functional blocks denoted by reference numerals) shown in FIG. 1, the transmission unit 12, the reception unit 14, the image forming unit 20, the displacement measurement unit 30, the fluctuation detection unit 40, the shear wave velocity calculation unit 50, the velocity evaluation. Each unit of the unit 60 and the display processing unit 70 can be realized by using hardware such as an electric/electronic circuit or a processor, and a device such as a memory may be used as necessary in realizing the same. The functions corresponding to the above units may be realized by the cooperation of hardware such as a CPU, a processor, and a memory, and software (program) that defines the operation of the CPU and the processor. Further, a preferable specific example of the display unit 72 is a liquid crystal display or the like. The control unit 80 is realized, for example, by cooperation between hardware such as a CPU, a processor, and a memory, and software (program) that defines the operation of the CPU and the processor.

Next, generation of shear waves and measurement of displacement, etc. by the ultrasonic diagnostic apparatus of FIG. 1 will be described in detail. In addition, about each structure (each functional block) shown in FIG. 1, the code|symbol of FIG. 1 is utilized in the following description.

FIG. 2 is a diagram for explaining a specific example relating to generation of shear waves and measurement of displacement. FIG. 2A shows a specific example of the push beam transmission beam P formed using the probe 10 and the tracking wave ultrasonic beams T1 and T2.

In FIG. 2A, the transmission beam P of the push wave is formed along the depth Y direction so as to pass through the position p in the X direction. For example, the transmission beam P of the push wave is formed with the position p on the X axis shown in FIG. 2A as the focal point. The position p is set to a desired position by, for example, a user (examiner) such as a doctor or an inspection technician who has confirmed the ultrasonic image of the in-vivo diagnosis target displayed on the display unit 72.

When the transmission beam P is formed with the position p as the focal point and the push wave is transmitted, a shear wave is generated at the position p and its vicinity in the living body. FIG. 2(A) shows a specific example of measuring the propagation velocity of shearing that occurs at the position p in the X direction.

In the specific example of FIG. 2A, two ultrasonic beams T1 and T2 of tracking waves are formed. The ultrasonic beam (transmit beam and receive beam) T1 is formed so as to pass through the position x1 on the X axis shown in FIG. 2A, and the ultrasonic beam (transmit beam and receive beam) T2 is formed, for example, as shown in FIG. It is formed so as to pass through the position x2 on the X axis shown in FIG. As will be described later, the distance between the position p and the position x is set so that the measured value of the shear wave propagation characteristic has sufficient reliability. The interval Δx between the position x1 and the position x2 is set to a desired position by the user who has confirmed the ultrasonic image of the diagnosis target displayed on the display unit 72, for example.

FIG. 2B shows a specific example of the generation timing of the transmission beam P of the push wave and the ultrasonic beams T1 and T2 of the tracking wave. The horizontal axis of FIG. 2B is the time axis t.

In FIG. 2B, a period P is a period in which the push beam transmission beam P is formed, and periods T1 and T2 are periods in which the tracking wave ultrasonic beams T1 and T2 are formed, respectively.

Within the period P, a large number of push waves are transmitted. For example, a continuous wave ultrasonic wave is transmitted within the period P. Then, for example, immediately after the period P ends, a shear wave is generated at the position p.

In the periods T1 and T2, tracking waves of so-called pulse waves of one wave to several waves are transmitted, and reflected waves accompanying the pulse waves are received. For example, the ultrasonic beams T1 and T2 passing through the positions x1 and x2 are formed, and the reception signals are obtained at a plurality of depths including the positions x1 and x2. That is, for each of the ultrasonic beams T1 and T2, received signals can be obtained from a plurality of depths.

The transmission/reception of tracking waves is repeatedly performed over a plurality of periods. That is, as shown in FIG. 2B, the periods T1 and T2 are alternately repeated until, for example, the displacement of the tissue due to the shear wave is confirmed.

The displacement measuring unit 30 and the shear wave velocity measuring unit 50 have a function as a shear wave measuring unit that measures the propagation characteristics of the shear wave based on the received signal obtained according to the tracking wave. As will be described later, the propagation characteristics include a spatiotemporal map that obtains the relationship between the phase displacement (differential value of the phase) of the shear wave and time for each depth of the subject, and the propagation velocity of the shear wave ..

The displacement measuring unit 30 forms a spatiotemporal map regarding the ultrasonic beam T1 based on the received signal of the ultrasonic wave T1 of the tracking wave, and based on the received signal of the ultrasonic beam T2 of the tracking wave, the ultrasonic beam T2. Form a spatiotemporal map for.

FIG. 3 is a diagram showing a specific example of the spatiotemporal map. The displacement measuring unit 30 calculates the phase displacement of the reception signal at a plurality of depths (a plurality of positions in the depth direction) based on the reception signal of the ultrasonic beam T1 of the tracking wave. The displacement measuring unit 30 calculates the phase displacement of the received signal for each depth over a plurality of times. Then, the displacement measuring unit 30 forms a space-time map in which the phase displacement of the received signal is mapped, with the horizontal axis representing time (time axis) and the vertical axis representing depth.

In the specific example of the spatiotemporal map shown in FIG. 3, the phase shift of the received signal is represented by the brightness in the spatiotemporal map. For example, the brightness is higher (white) as the phase displacement is positive and the absolute value is larger, and the brightness is lower (black) as the phase displacement is negative and the absolute value is larger. In the specific example of FIG. 3, the phase displacement relatively changes from high brightness (white) to low brightness (black) in the period from time 0 (zero) to 10 ms (milliseconds), and the shear wave changes during this period. Is passing.

Note that the spatiotemporal map in FIG. 3 is merely one specific example, and the phase shift of the received signal may be expressed by a color other than the display mode, such as color. For example, when the phase displacement is in the positive direction and the absolute value is large, the color is based on red, when the phase displacement is near zero, the color is based on green, and when the phase displacement is in the negative direction and the absolute value is large, the color is blue. It may be a different color.

In this way, the displacement measuring unit 30 forms the spatiotemporal map regarding the ultrasonic beam T1 based on the received signal of the ultrasonic beam T1 of the tracking wave. Further, the displacement measuring unit 30 calculates the phase displacement of the received signal at a plurality of depths based on the received signal of the ultrasonic beam T2 of the tracking wave, and forms the spatiotemporal map regarding the ultrasonic beam T2.

Returning to FIG. 1, the shear wave velocity calculator 50 calculates the propagation velocity Vs of the shear wave in the X-axis direction based on the phase displacement at the position x1 and the position x2 that change due to the influence of the shear wave generated at the position p. For example, the shear wave propagation in the X-axis direction is based on the time t1 when the phase displacement is maximum at the position x1, the time t2 when the phase displacement is maximum at the position x2, and the distance Δx between the position x1 and the position x2. The speed Vs=Δx/(t2-t1) is calculated. The shear wave propagation velocity may be calculated using another known method.

The shear wave velocity calculator 50 calculates the propagation velocity Vs for each depth of a plurality of depths, for example, based on the spatiotemporal map (FIG. 3) of the ultrasonic beam T1 and the ultrasonic beam T2. Furthermore, elasticity information such as the elasticity value of the tissue in which the shear wave is measured may be calculated based on the propagation velocity Vs of the shear wave, and viscoelastic parameters, attenuation, frequency characteristics, etc. are derived as the tissue information. May be done.

The measurement sequence shown in FIG. 2B is a period from when the transmission of the push wave is started to when the propagation velocity of the shear wave is calculated. In the example shown in this figure, there is a rest period for cooling the probe 10 after the end of the measurement sequence. Further, the next measurement sequence may be started after the rest period.

In the ultrasonic diagnostic apparatus according to this embodiment, the distance between the position of the transmission beam P of the push wave and the position of the ultrasonic beam T1 of the tracking wave (hereinafter referred to as the PT distance D) is the shear wave. It is set according to the threshold range of the propagation velocity. The threshold range is a numerical range set in advance as a range in which the reliability of the measured value of the shear wave propagation velocity is guaranteed. That is, the value that the propagation velocity of the shear wave can take generally tends to fall within a certain range clinically depending on the tissue or the like to be diagnosed. Therefore, in the ultrasonic diagnostic apparatus according to the present embodiment, the user sets a threshold range based on, for example, a large number of clinical results, and the measurement value of the propagation velocity outside the threshold range is a result of low reliability. Therefore, it is considered to be rejected.

When diagnosing a tissue having a high shear wave propagation velocity, the measurement value of the propagation velocity also becomes large, and the measurement value of the propagation velocity at which reliability is guaranteed also becomes large. Therefore, when diagnosing a tissue in which the shear wave propagation velocity is relatively large, the lower limit value and the upper limit value of the threshold range are set to be large, so that the measured value of the propagation velocity is appropriately rejected. Similarly, when diagnosing a tissue in which the propagation velocity of shear waves is relatively small, the lower limit value and the upper limit value of the threshold range are set to be small, so that the measured value of the propagation velocity is appropriately rejected.

The process of setting the PT distance D will be described with reference to FIGS. 4 and 5. FIG. 4 conceptually shows the processing when a push wave is transmitted at time tp and the measurement of the phase displacement by the ultrasonic beams of the tracking waves T1 and T2 is started at time tr after time tp. ing.

As shown in FIG. 4A, when the propagation distance of the shear wave W between the time tp and the time tr is smaller than the inter-PT distance D, the shear wave is generated when the phase displacement measurement is started. W does not pass the position x1 of the ultrasonic beam T1 of the tracking wave. In this case, since the shear wave W passes through the position x1 of the ultrasonic beam T1 and the position x2 of the ultrasonic beam T2 after the time tr has passed, the phase displacement due to each tracking wave can be measured. FIG. 4B shows the phase displacement A1 for the reception signal of the ultrasonic beam T1 and the phase displacement A2 for the reception signal of the ultrasonic beam T2. The horizontal axis represents time and the vertical axis represents phase displacement. The phase displacement A1 and the phase displacement A2 indicate the phase displacements at the position x1 and the position x2, respectively. Since the time t1 at which the phase displacement at the position x1 is maximum and the time t2 at which the phase displacement is maximum at the position x2 are both after the time tr, the propagation velocity of the shear wave in the X-axis direction is obtained as described above. ..

On the other hand, as shown in FIG. 5A, when the distance that the shear wave propagates from the time tp to the time tr is larger than the inter-PT distance D, the shear occurs when the measurement of the phase displacement is started. The wave W has already passed the position x1 of the ultrasonic beam T1. In this case, since the phase displacement of the shear wave W cannot be measured by the ultrasonic beam T1, the propagation velocity of the shear wave W cannot be measured. FIG. 5B shows the phase displacement A1 for the reception signal of the ultrasonic beam T1 and the phase displacement A2 for the reception signal of the ultrasonic beam T2. In this example, since the time interval t1 at which the phase displacement at the position x1 becomes maximum is before the time tr, the phase displacement of the shear wave cannot be measured by the ultrasonic beam T1, and the shear wave in the X-axis direction cannot be measured. It is not possible to determine the propagation velocity of.

It should be noted that when the measurement of the phase displacement is started, the shear wave passes through the position x1 of the ultrasonic beam T1 and further passes through the position x2 of the ultrasonic beam T2. Propagation velocity cannot be measured.

As described above, when the propagation velocity of the shear wave is high, the shear wave passes through the position x1 before the measurement of the phase displacement based on the tracking wave is started after the push wave is transmitted, and the shear wave is sheared. The problem arises that it becomes impossible to measure the wave propagation velocity.

Further, even if the shear wave propagates at a low velocity and the shear wave passes through the position x1 and the position x2 after the measurement of the phase displacement based on the tracking wave is started, if the inter-PT distance D is too large. The following problems occur. That is, the shear wave is attenuated by the time it reaches the position x1 and the position x2 and the phase error becomes large, or the waveform of the shear wave collapses and the phase error becomes large, and the error included in the measured propagation velocity becomes large. The problem arises that

Therefore, in the ultrasonic diagnostic apparatus according to the embodiment of the present invention, the inter-PT distance D is set according to the threshold range of the shear wave propagation velocity. As described later, the upper limit value and the lower limit value of the threshold range may be stored in the control unit 80 by a user operation.

The control unit 80, the transmission unit 12, and the reception unit 14 have a function as a position adjustment unit that adjusts the positional relationship between the push wave and the tracking wave. That is, the control unit 80 stores in advance a PT distance determination table that associates the upper limit value of the threshold range with the target value of the PT distance D. In the inter-PT distance determination table, the larger the upper limit value of the threshold range, the larger the target value of the inter-PT distance D associated with. Further, the target value of the inter-PT distance D is set to a value larger than the distance that the shear wave propagates during the time ts from the transmission of the push wave to the start of the measurement of the phase displacement. That is, when the upper limit value of the threshold range is Vm, the target value of the inter-PT distance D is set to a value larger than Vm·ts. The control unit 80 refers to the inter-PT distance determination table to obtain the target value corresponding to the upper limit value of the threshold range. The controller 80 controls the transmitter 12 and the receiver 14 to bring the PT-to-PT distance D closer to the target value or make the PT-to-PT distance D match the target value.

According to such processing, the greater the upper limit value of the threshold range, the greater the inter-PT distance D. Therefore, if the threshold range is appropriately set when diagnosing a tissue having a high shear wave propagation velocity, a sufficiently large distance D between PTs is ensured, and the frequency at which the shear wave propagation velocity cannot be measured becomes low. Get lower. Further, even in the case of diagnosing a tissue having a small shear wave propagation velocity, if the threshold range is appropriately set, the PT distance D can be made sufficiently small according to the tissue, and the accuracy of the measurement value of the propagation velocity can be improved. Is improved.

In the above, the example in which the control unit 80 stores the inter-PT distance determination table in advance has been described. The control unit 80 may calculate a target value function by which the target value of the inter-PT distance D is obtained by giving the upper limit value of the threshold range. In this case, the control unit 80 has a function calculation unit as a functional block that calculates the target value function, calculates the target value function, and obtains the target value corresponding to the upper limit value of the threshold range.

By the way, in the measurement of shear wave propagation velocity, the displacement of tissue periodically fluctuates due to the movement of microvessels and blood flow in the measurement region (region of interest), and this periodic fluctuation causes the shear wave propagation. This may affect speed measurements.

FIG. 6 shows a specific example of the spatiotemporal map obtained when fluctuation occurs. Compared to the spatiotemporal map shown in FIG. 3, in the spatiotemporal map shown in FIG. 6, fluctuations occur near a depth of 45 mm (millimeters). That is, in the vicinity of the depth of 45 mm, the phase shift of the received signal periodically repeats low luminance (black) and high luminance (white) for a relatively long period (0 to 30 ms or more), and the phase shift is periodic. Is fluctuating.

Therefore, in the vicinity of the depth of 45 mm, it is difficult to identify the change in the phase displacement due to the passage of the shear wave, and the propagation velocity of the shear wave cannot be measured. Even if the propagation velocity of the shear wave can be measured in the region (depth) where the fluctuation occurs, there is concern about the reliability of the measurement result.

Therefore, the fluctuation detection unit 40 detects a fluctuation that is a periodical displacement based on the displacement measurement result of the displacement measurement unit 30.

FIG. 7 is a diagram for explaining a specific example of fluctuation detection. The fluctuation detection unit 40 frequency-analyzes the temporal change of the phase displacement at each depth based on the spatiotemporal map obtained from the displacement measurement unit 30, and confirms whether there is a frequency component corresponding to the fluctuation.

FIG. 7 shows the result of frequency analysis of temporal changes in phase displacement. In FIG. 7, the horizontal axis represents frequency (Hz: Hertz), and the vertical axis represents power spectrum intensity, that is, intensity of each frequency component (dB: decibel).

FIG. 7 shows the frequency spectrum of the “phase fluctuation” at the depth where the fluctuation occurs (solid line) and the frequency spectrum of the “shear wave” at the depth where the fluctuation does not occur (broken line). ..

In the frequency spectrum of the "phase fluctuation", a peak (maximum) with a strong intensity appears at a specific frequency, around 100 Hz in the specific example of FIG. On the other hand, no prominent peak such as "phase fluctuation" appears in the frequency spectrum of "shear wave" that does not include fluctuation. Therefore, when there is a peak with a strong intensity in the frequency spectrum of the phase change at each depth, the fluctuation detection unit 40 has a periodic displacement at that depth, and fluctuations occur at that depth. It is determined that The fluctuation detection unit 40 determines that fluctuation occurs in the depth when, for example, a peak having an intensity exceeding the threshold exists in the frequency spectrum of the phase change at each depth.

The fluctuation detector 40 may detect the fluctuation by a process different from the frequency analysis. For example, in the spatiotemporal map, the absolute value of the phase displacement is added for each depth for multiple times, and the depth at which fluctuation is occurring is specified based on the addition result obtained for each depth. You may. As illustrated in FIG. 6, since the phase displacement of the received signal periodically fluctuates over a relatively long period at the depth at which fluctuations occur, the addition results of the absolute values of the phase displacement are compared. On the contrary, since the period in which the phase displacement of the received signal is 0 (zero) is dominant at the depth where the fluctuation does not occur, the addition result of the absolute value of the phase displacement becomes relatively small. Therefore, the fluctuation detection unit 40 adds the absolute values of the phase displacements for each depth over a plurality of times, and if the addition result obtained for each depth exceeds the determination threshold value, at that depth, It may be determined that the fluctuation is occurring. Further, the image portion (depth) in which the fluctuation has occurred may be determined by the image analysis processing on the spatiotemporal map.

The fluctuation detection unit 40 detects the depth at which fluctuation occurs in each of the spatiotemporal map of the ultrasonic beam T1 and the spatiotemporal map of the ultrasonic beam T2. Then, the depth at which the fluctuation occurs in at least one of the spatiotemporal maps of the ultrasonic beam T1 and the ultrasonic beam T2 is transmitted to the velocity evaluation unit 60.

Next, a specific example of shear wave measurement by the ultrasonic diagnostic apparatus of FIG. 1 will be described. In the shear wave measurement, the shear wave propagation velocity Vs is measured by the measurement sequence described with reference to FIG. The shear wave velocity calculation unit 50 calculates the propagation velocity Vs of the shear wave for each depth in the subject based on the spatiotemporal map (see FIG. 3) relating to the ultrasonic beams T1 and T2 of the tracking waves. To do. As a result, a measurement value sequence including a plurality of propagation velocities Vs corresponding to a plurality of depths is obtained. Furthermore, in shear wave measurement, the measurement sequence described using FIG. 2 is executed multiple times, a measurement set consisting of multiple measurement sequences is executed, and multiple measurement values corresponding to multiple measurement sequences are executed. Rows are obtained.

FIG. 8 is a diagram showing a specific example of the measurement result of the measurement set. FIG. 8 shows a series of measured values of the propagation velocity Vs obtained by four measurement sequences. In the specific example shown in FIG. 8, for example, by the first measurement sequence (1), a plurality of propagation velocities Vs(1,1), Vs(1,2) corresponding to a plurality of depths r1, r2,... , Is obtained, and a plurality of propagation velocities Vs(2,1), Vs(2 corresponding to the plurality of depths r1, r2,... Are obtained by the second measurement sequence (2). , 2),... A series of measured values is obtained. Of course, a measurement set including a measurement sequence of 5 times or more or 3 times or less may be executed.

When a measurement set including a plurality of measurement sequences is executed and a plurality of measurement values (a plurality of propagation velocities Vs) forming the measurement set are calculated by the shear wave velocity calculation unit 50, the velocity evaluation unit 60 causes the plurality of measurement values to be calculated. At least one measurement value satisfying the rejection condition is specified from among the measurement values of. The rejection condition is stored in advance in the speed evaluation unit 60 as a condition setting unit. As the rejection condition, for example, a condition based on the magnitude of the measured value (propagation velocity Vs), a condition based on the tissue state in the subject, or the like is suitable.

FIG. 9 is a diagram for explaining a specific example of the rejection condition. FIG. 9 shows a velocity map relating to the propagation velocity Vs calculated by the shear wave velocity calculator 50. The velocity map shown in FIG. 9 corresponds to the propagation velocity Vs obtained by one measurement sequence, the vertical axis is the depth, and the horizontal axis is the propagation velocity Vs. Then, in FIG. 9, Condition 1 to Condition 3 are illustrated as specific examples of the rejection condition.

Under the condition 1, the propagation velocity Vs having a minus sign (reverse direction) is rejected. For example, in the shear wave measurement described with reference to FIG. 2, a relatively strong shear wave is generated at and around the position p where the push beam transmission beam P is transmitted, and the shear wave is a tracking wave. It propagates in the direction of the book ultrasonic beams T1, T2. Therefore, in the specific example of FIG. 2, assuming that the direction from the position p to the position x1 is a positive (plus) direction, it has a positive (plus) value if the shear wave propagation velocity Vs is normal. However, the propagation velocity Vs in the negative (minus) direction may be calculated when the shear wave cannot be normally detected due to the disturbance of the shear wave or the like. Therefore, the propagation velocity Vs with a minus sign (reverse direction) is rejected because the result has low reliability.

Further, in the specific example shown in FIG. 9, under the condition 2, the propagation velocity Vs that is outside the threshold range is rejected. In the ultrasonic diagnostic apparatus according to the present embodiment, for example, the user sets a threshold range based on a large number of clinical results and the like, and the measurement value of the propagation velocity Vs outside the threshold range is a result of low reliability. Considered and rejected.

In setting the condition 2, in the ultrasonic diagnostic apparatus according to the embodiment of the present invention, the organ to be diagnosed is first specified by the user's operation. Then, the lower limit value and the upper limit value of the measured value of the propagation velocity of the shear wave are predetermined according to the organ to be diagnosed, and the threshold value range is set by the lower limit value and the upper limit value.

Further, regardless of the organ to be diagnosed, the lower limit value and the upper limit value may be input by the user's operation with respect to the measured value of the shear wave propagation velocity, and the threshold range may be set by the lower limit value and the upper limit value. For example, a user such as a doctor or a technologist may set the upper limit value and the lower limit value of the threshold range according to the type of tissue to be diagnosed, the age, sex, etc. of the subject.

The process of setting the threshold range will be specifically described. The operation unit 82, the control unit 80, the display processing unit 70, and the display unit 72 have a function as a threshold range setting unit that sets a threshold range according to a user operation. When an instruction to set the organ to be diagnosed is issued from the operation unit 82 based on the user's operation, the control unit 80 causes the display processing unit 70 to execute the process of displaying the organ selection image. The organ selection image is an image representing a figure for allowing the user to select an organ to be diagnosed. The display processing unit 70 displays the organ selection image on the display unit 72 under the control of the control unit 80.

FIG. 10 shows an example of the organ selection image. While this image is displayed on the display unit 72, the organ selection button 74 is operated in response to the operation of the operation unit 82, and the organ to be diagnosed is selected. In FIG. 10, the organ selection buttons 74 are “kidney”, “liver”, “pancreas”, “prostate”, and “spleen” organ selection buttons. When the organ selection button 74 is operated by the user's operation, the lower limit and the upper limit of the shear wave propagation velocity Vs of the organ corresponding to the organ selection button 74 are displayed below the organ selection screen. FIG. 10 shows that the lower limit value is 0.7 m/s and the upper limit value is 4.0 m/s.

While the organ selection image is displayed, the control unit 80 acquires information for identifying the organ to be diagnosed (diagnosis site information for identifying the diagnosis site) by the user operating the operation unit 82, and displays the information in the organ selection image. The set lower and upper limits are set.

When the user setting button 76 labeled "user" is operated by the user's operation, the lower limit and upper limit fields of the propagation velocity Vs in the lower part of the organ selection screen are in the input waiting state. In this state, the lower limit value and the upper limit value of the propagation velocity Vs are input by the user operating the operation unit 82. As a result, the lower limit value and the upper limit value of the propagation velocity Vs are input regardless of the organ to be diagnosed. That is, when the fields of the lower limit value and the upper limit value are in the input waiting state, the control unit 80 operates the operation unit 82 to acquire the lower limit value or the upper limit value.

The lower limit value and the upper limit value of the threshold value range (the lower limit value and the upper limit value as default values) before being changed by the user setting button 76 may be stored in the control unit 80 in advance by a user operation. In this case, when the operation unit 82 issues an instruction to set the upper limit value or the lower limit value of the threshold range based on the user's operation, the control unit 80 causes the display processing unit to display the threshold range preset image. 70 to execute. The threshold range preset image is an image showing a figure for allowing the user to set the upper limit value and the lower limit value of the threshold range. The display processing unit 70 causes the display unit 72 to display the threshold range preset image under the control of the control unit 80.

FIG. 11 shows an example of the threshold range preset image. A lower limit value input area 84 and an upper limit value input area 86 are shown on the right side of the respective organ name displays 78 of “kidney”, “liver”, “pancreas”, “prostate” and “spleen”. The lower limit value is input by operating the button on the right side of the lower limit value input area 84, and the lower limit value is input by operating the button on the right side of the upper limit value input area 86. The lower limit value and the upper limit value for each organ set by the threshold range preset image are displayed as the lower limit value and the upper limit value corresponding to each organ selection button 74 in the organ selection image shown in FIG.

Under the condition 3, the propagation velocity Vs at each depth where the fluctuation is detected is rejected. As described with reference to FIG. 6, in the measurement of the shear wave propagation velocity Vs, the displacement of the tissue periodically fluctuates due to the movement of the small blood vessels and the blood flow in the measurement region (region of interest), This periodic fluctuation may affect the measurement of the shear wave propagation velocity Vs. For example, in a region (depth) where fluctuations occur, it is difficult to identify the change in phase displacement due to the passage of shear waves, and it is difficult to measure the propagation velocity Vs of shear waves. Even if the propagation velocity Vs of the shear wave can be measured in the region (depth) where the fluctuation occurs, there is concern about the reliability of the measurement result. Therefore, the propagation velocity Vs at each depth where the fluctuation is detected is rejected because the result has low reliability. It should be noted that the depth at which the fluctuation is generated is detected by the fluctuation detection unit 40 as described above. The propagation velocity Vs to be rejected is specified by the velocity evaluation unit 60, which is a preferred specific example of the measurement value processing unit.

The velocity evaluation unit 60 sets the propagation velocity Vs calculated by the shear wave velocity calculation unit 50, for example, the propagation velocity Vs satisfying the rejection condition among the plurality of propagation velocity Vs in the measurement set shown in FIG. To do. For example, the propagation velocity Vs corresponding to any one of the conditions 1 to 3 described with reference to FIG. The propagation velocity Vs targeted for rejection may be deleted from the measurement set shown in FIG. 8, for example, and the value (data) of the propagation velocity Vs is not deleted but a flag indicating that it is a rejection target. Etc. may be associated.

Then, the velocity evaluation unit 60 rejects the propagation velocity Vs satisfying the rejection condition from among the plurality of propagation velocity Vs in the measurement set, and the plurality of propagation velocity Vs left without being rejected, that is, effective measurement values. VsN (effective Vs ratio), which is the ratio of the plurality of assumed propagation velocities Vs, is calculated.

The speed evaluation unit 60 calculates VsN for each measurement sequence in the measurement set as an evaluation value (reliability evaluation value) for evaluating reliability. For example, in the measurement set shown in FIG. 8, for the propagation velocities Vs of a plurality of depths forming each measurement sequence of the measurement sequence (1) to the measurement sequence (4), VsN (effective Vs ratio) is calculated for each measurement sequence. calculate. Then, for example, when VsN of each measurement sequence is equal to or less than the threshold value, the reliability of the measurement sequence may be regarded as low, and the propagation velocity Vs of the entire depth of the measurement sequence may be rejected. For example, in the specific example of FIG. 8, when VsN of the measurement sequence (3) is equal to or less than the threshold value of 30%, all the propagation velocities Vs(3,1), Vs(3,2) of the measurement sequence (3). ),... are rejected.

Further, the velocity evaluation unit 60, based on the plurality of propagation velocities Vs left without being rejected among the plurality of propagation velocities Vs in the measurement set, that is, the plurality of propagation velocities Vs regarded as valid measurement values. , A statistical value regarding the propagation velocity Vs is calculated as a reliability evaluation value. As the statistical value, for example, an average value, median value, IQR, standard deviation, VsN (effective Vs ratio), etc. regarding a plurality of propagation velocities Vs regarded as effective measured values are preferable, but other statistical values are preferable. It may be calculated. Then, the calculated statistical value is displayed on the display unit 72 by, for example, a numerical value or the like.

Further, the velocity evaluation unit 60, based on the plurality of propagation velocities Vs left without being rejected among the plurality of propagation velocities Vs in the measurement set, that is, the plurality of propagation velocities Vs regarded as valid measurement values. , A histogram relating to the propagation velocity Vs may be formed. The histogram is information that statistically represents the reliability evaluation value.

FIG. 12 is a diagram showing a specific example of a histogram regarding the propagation velocity Vs. In FIG. 12, (A) is a specific example of a histogram obtained in stable measurement in which VsN (effective Vs ratio) is relatively large, and the distribution has a single peak. On the other hand, (B) is a specific example of the histogram obtained in unstable measurement in which VsN is relatively small, and has a dispersive distribution. In each of the histograms (A) and (B), the horizontal axis represents the propagation velocity Vs and the vertical axis represents the frequency. The maximum value of the vertical axis (frequency) is preferably determined by the following equation, for example.

Formula 1 is one of the specific examples for standardizing the vertical axis frequency of the propagation velocity Vs. In Equation 1, assuming that a normal distribution is obtained when the propagation velocity Vs can be measured ideally and stably, the bin width (ΔBIN) of the histogram and the assumed standard deviation (std) of the propagation velocity Vs can be obtained. Based on this, the maximum value of the vertical axis frequency (Ymax) is calculated.

For example, by normalizing the vertical axis frequency according to Equation 1, the area of the histogram may be changed in accordance with the number of effective propagation velocities Vs (a plurality of propagation velocities Vs not rejected) that are targets of the histogram. become.

In the histogram shown in FIG. 12, the maximum value of the vertical axis frequency is determined based on Formula 1. The histogram of (A) is obtained by stable measurement in which VsN (effective Vs ratio) is relatively large, and since the number of effective propagation speeds Vs is relatively large, the area of the histogram is relatively large. On the other hand, the histogram of (B) is obtained by an unstable measurement in which VsN (effective Vs ratio) is relatively small, and since the number of effective propagation speeds Vs is relatively small, the histogram areas are compared. Small

Thus, for example, by normalizing the maximum value of the vertical axis frequency based on Equation 1, the number of effective propagation velocities Vs reflected in the histogram is reflected in the area of the histogram, and from the area of the histogram, It is possible to visually judge whether or not the measurement result is stable.

The histogram formed in the speed evaluation unit 60, for example, the histogram shown in FIG. 12 is displayed on the display unit 72. The histogram may be displayed together with the B-mode image.

FIG. 13 is a diagram showing a specific example of a display image. FIG. 13 shows a specific example of a display image formed in the display processing unit 70 and displayed on the display unit 72. The display image of FIG. 13 is obtained based on the B-mode image (tomographic image) formed by the image forming unit 20 and the histogram formed by the speed evaluation unit 60.

A region of interest (ROI) may be displayed in the B-mode image. For example, as in the specific example shown in FIG. 13, a rectangular mark indicating the region of interest (ROI) is displayed. The region of interest (ROI) is a region where shear wave measurement is performed, that is, a region where the spatiotemporal map (FIG. 3) is obtained.

Further, a region corresponding to the fluctuation portion detected by the fluctuation detection unit 40 may be clearly indicated in the region of interest (ROI). For example, in the region of interest (ROI), the fluctuation portion is highlighted by a display mode such as a pattern, brightness, or color. Thereby, for example, when the fluctuation part is large (wide) in the region of interest (ROI), the user may reset the position of the region of interest (ROI).

The region of interest (ROI) is basically set by a user operation. However, as described above, when setting the PT distance D according to the threshold range of the shear wave propagation velocity, it is necessary to change the position of the region of interest (ROI) according to the threshold range. That is, the larger the upper limit of the threshold range, the larger the inter-PT distance D is set, and it becomes necessary to separate the region of interest from the position where the push wave is transmitted. Therefore, when the position of the region of interest (ROI) set by the user's operation is not sufficient to secure the PT distance D, the control unit 80 determines the region of interest (ROI) position according to the PT distance D. May be changed. That is, the control unit 80 may perform the process of separating the position of the region of interest (ROI) from the position of the tracking wave as the upper limit value of the threshold range increases.

In the specific example of FIG. 13, a histogram of the propagation velocity Vs (FIG. 12) is displayed on the B-mode image. The histogram may be displayed so as not to overlap the B-mode image, or may be switched between display and non-display according to an instruction from the user. Of course, only the histogram may be displayed large.

In addition, the numerical value of the statistical value (average value, median, IQR, standard deviation, VsN, etc.) regarding the propagation velocity Vs calculated by the velocity evaluation unit 60 is displayed on the B mode image or in the B mode. It may be displayed near the image.

Although the preferred embodiments of the present invention have been described above, the above-described embodiments are merely examples in all respects and do not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

10 probe, 12 transmitter, 14 receiver, 20 image forming unit, 30 displacement measuring unit, 40 fluctuation detecting unit, 50 shear wave velocity calculating unit, 60 velocity evaluating unit, 70 display processing unit, 72 display unit, 74 organ selection Button, 76 User setting button, 78 Organ name display, 80 Control section, 82 Operation section, 84 Lower limit value input area, 86 Upper limit value input area.

Claims (7)

A transmitting unit that transmits a push wave of ultrasonic waves to generate a shear wave in the subject, and transmits two tracking waves of ultrasonic waves having different transmission positions to the subject,
A shear wave measuring unit that measures a propagation velocity of the shear wave based on a received signal obtained according to the two tracking waves;
A threshold range setting unit that sets a threshold range for the propagation velocity of the shear wave according to a user operation,
A position in which the push-wave is transmitted, the PT distance between the position closer to the push-wave of the two said tracking wave is transmitted, the control unit that adjusts, based on the upper limit of the threshold range An ultrasonic diagnostic apparatus comprising: The ultrasonic diagnostic apparatus according to claim 1,
The control unit is
It stores an inter-PT distance determination table that associates an upper limit value of the threshold range with a target value of the PT distance, and refers to the inter-PT distance determination table to correspond to the upper limit value of the threshold range. the calculated target value, and controls the transmitting unit, close the PT distance to the target value, or an ultrasonic diagnostic apparatus according to claim Rukoto match the PT distance to the target value. The ultrasonic diagnostic apparatus according to claim 1,
The control unit is
The target value function that obtains the target value of the inter-PT distance is calculated by giving the upper limit value of the threshold range, the target value corresponding to the upper limit value of the threshold range is obtained, and the transmitting unit is controlled. The ultrasonic diagnostic apparatus is characterized in that the PT distance is brought closer to the target value or the PT distance is made to match the target value. A transmitting unit that transmits a push wave of an ultrasonic wave to generate a shear wave in the subject, and sends a tracking wave of the ultrasonic wave to the subject,
By measuring the propagation characteristics of the shear wave based on the received signal obtained in accordance with the tracking wave, shear to obtain a measurement value sequence including measurement values for each depth in a plurality of depths in the subject A wave measurement unit,
A threshold range setting unit that sets a threshold range for the measured value of the shear wave according to a user operation,
From among the plurality of the measurement sequence obtained by carrying out a plurality of times a measurement of the shear wave, have a, a measuring value processing unit for specifying a measurement value outside the threshold range,
The threshold range setting unit,
An operation unit, a control unit, a display processing unit, and a display unit are provided,
The display processing unit,
Any one of the plurality of diagnostic sites for the subject is displayed on the display unit as an operation graphic for selecting by operation on the operation unit,
The control unit is
An ultrasonic diagnostic apparatus, characterized in that the threshold range is set based on information stored in advance for the diagnostic region selected by an operation on the operation figure . The ultrasonic diagnostic apparatus according to claim 4,
An input field in which the upper limit value or the lower limit value of the threshold range is input is displayed on the display unit together with the operation figure,
The control unit is
The ultrasonic diagnostic apparatus is characterized in that, when a value is input to the input field by an operation of the operation unit, the threshold range is set based on the value input to the input field. The ultrasonic diagnostic apparatus according to claim 5 ,
The threshold range setting unit,
An ultrasonic diagnostic apparatus , wherein at least one of an upper limit value and a lower limit value of the threshold range is set on the basis of a value input to the input section by an operation on the operation unit . The ultrasonic diagnostic apparatus according to any one of claims 4 to 6 ,
A rejection condition for the measured value of the shear wave, including a condition setting unit for setting a rejection condition including the threshold range as a condition,
The measurement value processing unit,
An ultrasonic diagnostic apparatus, wherein a reliability evaluation value for each of the plurality of measurement values is obtained based on the plurality of measurement values that form the plurality of measurement value sequences and the rejection condition.