JP2015128554A - Ultrasonic diagnostic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measuring precision of a shear wave in ultrasonic diagnostic equipment.SOLUTION: A probe 10 has a function to transmit an ultrasonic wave (push pulse) for generating a shear wave, a function to transmit/receive an ultrasonic wave (tracking pulse) for measuring the shear wave, and a function to transmit/receive an ultrasonic wave for forming an image. A reception part 14 forms a reception beam of the tracking pulse based on a received wave signal acquired when the probe 10 transmits/receives the tracking pulse, and acquires a reception signal corresponding to the reception beam. A phase calculation part 30 generates displacement data showing the displacement of the shear wave over a plurality of time phases based on the reception signal corresponding to the reception beam of the tracking pulse acquired from the reception part 14. A speed calculation part 40 calculates a speed of the shear wave based on time differential data acquired by subjecting the displacement data to time differential processing.

Description

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

  Technology that generates shear waves in the target tissue, measures shear waves propagating in the target tissue using ultrasonic waves, and obtains physical quantities related to the hardness of the target tissue based on the propagation speed of the shear waves, etc. It has been.

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

  However, in the living body, for example, it may be difficult to accurately detect the maximum displacement of the shear wave due to external factors such as body movement of the living body and movement of the probe. For example, in the invention according to Patent Document 1, if the maximum displacement of the shear wave cannot be accurately detected, the measurement accuracy of the shear wave is lowered.

US Pat. No. 8,118,744

  In view of the background art described above, the inventor of the present application has repeatedly researched and developed a technique for measuring a shear wave using an ultrasonic diagnostic apparatus.

  The present invention has been made in the course of its research and development, and its purpose is to increase the measurement accuracy of shear waves in an ultrasonic diagnostic apparatus.

  A suitable ultrasonic diagnostic apparatus for the above purpose includes a probe for transmitting and receiving ultrasonic waves, a transmission unit for outputting ultrasonic transmission signals for measuring shear waves to the probes, and processing signals obtained from the probes to obtain shear waves. A receiving unit for obtaining a received ultrasonic signal, a displacement measuring unit for generating displacement data indicating displacement of shear waves over a plurality of time phases based on the received signal, and time-differentiating the displacement data. And a velocity calculating unit that calculates the velocity of the shear wave based on the obtained time differential data.

  In the above apparatus, the velocity of the shear wave is calculated based on the time differential data obtained by time differential processing of the displacement data. The displacement data may include external factors such as body movement of the living body and movement of the probe. According to the above apparatus, by performing time differentiation processing on the displacement data, the external factors included in the displacement data are reduced, and preferably completely eliminated, so that the shear wave measurement accuracy is improved.

  In a preferred embodiment, the displacement measurement unit generates displacement data for each position based on the received signals obtained from different positions, and the speed calculation unit performs time differentiation on the displacement data for each position. Processing to generate time differential data, and based on the characteristic time phase in the time differential data at the first position and the characteristic time phase in the time differential data at the second position, the velocity of the shear wave is calculated, It is characterized by that.

  In a preferred embodiment, the speed calculation unit is based on at least one time phase among a maximum value time phase, a minimum value time phase, and a zero-cross time phase as a characteristic time phase in the time differential data at each position. The velocity of the shear wave is calculated.

  In a preferred embodiment, the displacement measuring unit generates displacement data indicating a temporal change in the phase of the shear wave at each position based on the received signals obtained from different positions. To do.

  In a preferred embodiment, the transmission unit outputs an ultrasonic transmission signal for generating a shear wave to the probe, and outputs an ultrasonic transmission signal for measuring the shear wave generated thereby to the probe. Features.

  According to the present invention, the measurement accuracy of shear waves in the ultrasonic diagnostic apparatus is enhanced.

1 is a diagram illustrating an overall configuration of an ultrasonic diagnostic apparatus that is preferable in the practice of the present invention. It is a figure for demonstrating the specific example of generation | occurrence | production and measurement of a shear wave. It is a figure which shows the specific example of the data obtained in the measurement of a shear wave.

  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 a region including a diagnosis target such as a tissue in a living body. The probe 10 includes a plurality of vibration elements each of which transmits / receives or transmits an ultrasonic wave, and the transmission unit 12 controls transmission of the plurality of vibration elements to form a transmission beam.

  In addition, the plurality of vibration elements included in the probe 10 receive ultrasonic waves from within the region including the diagnosis target, and a signal obtained thereby is output to the reception unit 14. The reception unit 14 forms a reception beam. A reception signal (echo data) is collected along the reception beam.

  The probe 10 has a function of transmitting an ultrasonic wave (push pulse) that generates a shear wave in a region including a diagnosis target, a function of transmitting and receiving an ultrasonic wave (tracking pulse) that measures the shear wave, and an image forming function. It has a function to send and receive ultrasonic waves.

  Transmission of ultrasonic waves is controlled by the transmission unit 12. That is, when generating a shear wave, the transmission unit 12 outputs a push pulse transmission signal to a plurality of vibration elements included in the probe 10, thereby forming a push pulse transmission beam. Further, when measuring the shear wave, the transmission unit 12 outputs a tracking pulse transmission signal to a plurality of vibration elements included in the probe 10, thereby forming a tracking pulse transmission beam. Furthermore, when forming an ultrasonic image, the transmission unit 12 outputs a transmission signal for image formation to a plurality of vibration elements included in the probe 10, thereby scanning the transmission beam for image formation.

  In addition, the receiving unit 14 forms a reception beam of the tracking pulse based on the reception signals obtained from the plurality of vibration elements when the probe 10 transmits and receives the tracking pulse, and obtains a reception signal corresponding to the reception beam. . Further, the receiving unit 14 forms an image-forming reception beam based on reception signals obtained from a plurality of vibration elements by the probe 10 transmitting and receiving ultrasonic waves for image formation, and corresponds to the reception beam. Generate a received signal.

  The ultrasonic beam for image formation (transmission beam and reception beam) is scanned in a two-dimensional plane including a diagnostic object, and reception signals for image formation are collected from the two-dimensional plane. Of course, the ultrasonic beam for image formation may be scanned three-dimensionally in the three-dimensional space, and reception signals 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. For example, the image forming unit 20 forms image data of a B-mode image of an area including a diagnosis target. Note that when the reception signals for image formation are collected three-dimensionally, the image forming unit 20 may form image data of a three-dimensional ultrasonic image.

  The phase calculation unit 30 generates displacement data indicating the displacement of the shear wave over a plurality of time phases based on the reception signal corresponding to the reception beam of the tracking pulse obtained from the reception unit 14. Moreover, the velocity calculation unit 40 calculates the velocity of the shear wave based on the time differential data obtained by time differential processing of the displacement data. The processing in the phase calculation unit 30 and the speed calculation unit 40 will be described in detail later.

  The display processing unit 50 forms a display image based on the image data of the ultrasonic image obtained from the image forming unit 20 and the shear wave velocity calculated by the velocity calculating unit 40. The display image formed in the display processing unit 50 is displayed on the display unit 52. The control unit 60 generally controls the inside of the ultrasonic diagnostic apparatus shown in FIG.

  In each configuration (each functional block) illustrated in FIG. 1, the transmission unit 12, the reception unit 14, the image forming unit 20, the phase calculation unit 30, the speed calculation unit 40, and the display processing unit 50 are each an electric / electronic circuit, for example. And a hardware such as a processor, and a device such as a memory may be used as necessary in the realization. A suitable specific example of the display unit 52 is a liquid crystal display or the like. The control unit 60 can be realized by, for example, 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.

  The outline of the ultrasonic diagnostic apparatus in FIG. 1 is as described above. Next, the generation and measurement of shear waves by the ultrasonic diagnostic apparatus of FIG. 1 will be described in detail. In addition, about the structure (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 of generation and measurement of shear waves. FIG. 2A shows a specific example of a push pulse transmission beam P formed by using the probe 10 and tracking pulse ultrasonic beams T1 and T2.

  In FIG. 2A, the transmission beam P of the push pulse is formed along the depth Y direction so as to pass the position p in the X direction. For example, the transmission beam P of the push pulse is formed with the position p on the X axis shown in FIG. The position p is set to a desired position, for example, by a user (inspector) who has confirmed the diagnostic target ultrasonic image displayed on the display unit 52.

  When the push pulse transmission beam P is formed with the position p as the focal point and the push pulse is transmitted, a relatively strong shear wave is generated starting from the position p. In FIG. 2A, the propagation velocity in the X direction of the shear generated around the position p is measured.

  In FIG. 2A, two ultrasonic beams T1 and T2 related to the tracking pulse are formed. The ultrasonic beam (transmission beam and reception beam) T1 is formed so as to pass through a position x1 on the X axis shown in FIG. 2A, for example, and the ultrasonic beam (transmission beam and reception beam) T2 is shown in FIG. It is formed so as to pass through a position x2 on the X axis shown in FIG. For example, the position x1 and the position x2 may be set to desired positions by a user (examiner) who has confirmed an ultrasonic image to be diagnosed displayed on the display unit 52, or from the position p along the X direction. Positions x1 and x2 may be set at locations separated by a predetermined distance. Note that the distance from the position p to the position x2 is, for example, about several mm to several cm, and particularly preferably about 10 mm.

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

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

  In the period P, multiple push pulses are transmitted. For example, in the period P, continuous wave ultrasonic waves are transmitted. Thereby, for example, a shear wave is generated at the position p.

  In periods T1 and T2, a tracking pulse of a so-called pulse wave of about 1 to several waves is transmitted, and a reflected wave accompanying the pulse wave is received. For example, ultrasonic beams T1 and T2 passing through the positions x1 and x2 are formed, and a reception signal at the positions x1 and x2 is obtained.

  The tracking pulse is repeatedly transmitted and received over a plurality of periods. That is, as shown in FIG. 2B, the periods T1 and T2 are alternately repeated, for example, the period T1 and the period T2 are each repeated about 75 times. Thereby, at each of the position x1 and the position x2, a reception signal is acquired over a plurality of times, and a shear wave is measured.

  Note that PRT (T1) is a repetition time of the period T1, and PRT (T2) is a repetition time of the period T2. The reference time T1 and the reference time T2 are times that serve as a reference when calculating the phase of the shear wave. For example, as shown in FIG. 2B, periods T1 and T2 that first appear after the period P of the push pulse are set as the reference time T1 and the reference time T2, respectively. Note that the reference time T1 and the reference time T2 are not limited to immediately after the period P, and may be set to any period T1 and period T2. However, it is desirable that the reference time T1 and the reference time T2 are set to a period T1 and a period T2 that are adjacent to each other.

  In the specific example of FIG. 2, the tracking pulse ultrasonic beams T1 and T2 are formed on the positive direction side of the X axis with respect to the push pulse transmission beam P. On the other hand, the ultrasonic waves T1 and T2 of the tracking pulse may be formed on the negative direction side of the X axis, and the shear wave propagating on the negative direction side of the X axis may be measured. Of course, it is desirable that the position p of the push pulse transmission beam P and the positions x1 and x2 of the ultrasonic pulses T1 and T2 of the tracking pulse are appropriately set according to the diagnosis target, the diagnosis situation, and the like.

  FIG. 3 is a diagram illustrating a specific example of data obtained in the measurement of shear waves. FIG. 3 (1) shows a specific example of displacement data indicating the time change of the phase φ of the shear wave. In FIG. 3A, a waveform T1 indicates the phase of the shear wave at a position x1 (FIG. 2) where the ultrasonic beam T1 of the tracking pulse is formed, and a waveform T2 indicates that the ultrasonic beam T2 of the tracking pulse is The phase of the shear wave at the position x2 (FIG. 2) to be formed is shown.

  The phase calculation unit 30 generates the position x1 based on the received signal at the position x1 at the reference time T1 (FIG. 2) and the received signal at the position x1 obtained for each period T1 (FIG. 2) over a plurality of periods T1. The waveform T1 is formed by calculating the phase φ of the shear wave at. Further, the phase calculation unit 30 is based on the reception signal at the position x2 at the reference time T2 (FIG. 2) and the reception signal at the position x2 obtained for each period T2 (FIG. 2) over a plurality of periods T2. The waveform T2 is formed by calculating the phase φ of the shear wave at the position x2.

For example, the phase calculation unit 30 performs a quadrature detection process or the like on the reception signal at the reference time, and calculates the complex reception signal (IQ _n ) at the reference time shown in Equation 1. In addition, the phase calculation unit 30 performs a quadrature detection process or the like on the reception signal in each period, and calculates a complex reception signal (IQ _i ) at each time i shown in Formula 1.

Further, the phase calculation unit 30 calculates a complex conjugate product (r _i ) for the complex received signal (IQ _n ) at the reference time and the complex received signal (IQ _i ) in each period as shown in Equation 2.

Then, based on Real (r _i ), which is a real component of the complex conjugate product (r _i ), and Imag (r _i ), which is an imaginary component, the phase calculation unit 30, as shown in Equation 3, at time i, The phase φ (angle _i ) is calculated.

The phase calculation unit 30 applies Equations (1) to (3) to the complex reception signal (IQ _n ) at the position x1 at the reference time T1 and the complex reception signal (IQ _i ) at the position x1 in each period T1 to obtain a plurality of periods. The waveform T1 of FIG. 3 is generated by calculating the phase φ for T1 (a plurality of times). Further, the phase calculation unit 30 applies Equations (1) to (3) to the complex reception signal (IQ _n ) at the position x2 at the reference time T2 and the complex reception signal (IQ _i ) at the position x2 in each period T2, and a plurality of periods are applied. The waveform T2 of FIG. 3 is generated by calculating the phase φ for T2 (a plurality of times).

  When the phase calculation unit 30 generates the displacement data indicating the time change of the phase φ of the shear wave, the velocity calculation unit 40 performs time differentiation processing on the displacement data to generate time differential data. In the specific example of FIG. 3, the speed calculation unit 40 performs time differentiation processing on the waveform T1 and the waveform T2 of FIG. 3A to generate a time differentiation waveform of the phase φ illustrated in FIG.

  The waveform T1 and the waveform T2 in FIG. 3 (2) are obtained by time-differentiating the waveform T1 and the waveform T2 in FIG. 3 (1), respectively. The speed calculation unit 40 generates the waveform T1 and the waveform T2 of FIG. 3 (2) from the waveform T1 and the waveform T2 of FIG. 3 (1) by, for example, differentiation processing using a differential filter or the like. It should be noted that it is desirable to perform differential processing after applying a low-pass filter or the like to the waveforms T1 and T2 in FIG.

  Then, the speed calculation unit 40 calculates the shear wave speed based on the time differential data. The velocity calculation unit 40 calculates the shear wave velocity based on the characteristic time phase in the waveform T1 and the characteristic time phase in the waveform T2 in FIG. As the characteristic time phase, for example, at least one time phase among a maximum value time phase, a minimum value time phase, and a zero-cross time phase is used.

  In FIG. 3 (2), time t1 and time t3 are time phases when the maximum values (positive peaks) of the waveform T1 and the waveform T2 are obtained, respectively. Time t2 and time t5 are the zero-cross time phases of the waveform T1 and the waveform T2, respectively. In addition, time t4 and time t6 are time phases when the minimum values (negative peaks) of the waveform T1 and the waveform T2 are obtained, respectively.

  The speed calculation unit 40 calculates the propagation speed of the shear wave in the X-axis direction (FIG. 2) using Equation 4 based on time t1 to time t6. In Equation 4, Vs (P) is a speed based on the maximum value (positive peak) of the waveform T1 and the waveform T2, and Vs (0) is a speed based on the zero crossing of the waveform T1 and the waveform T2, and Vs (N) is a speed based on the minimum value (negative peak) of the waveform T1 and the waveform T2. Δx is the distance between the position x1 and the position x2.

When the speed calculation unit 40 calculates the speed Vs, the display processing unit 50 forms a display image including the speed Vs, and the display image is displayed on the display unit 52. For example, at least one of Vs (P), Vs (0), and Vs (N) in Expression 4 is displayed. As the speed Vs, an average value of Vs (P), Vs (0), and Vs (N) may be calculated and displayed. Further, an index related to tissue hardness may be calculated and displayed together with the speed Vs or instead of the speed Vs. For example, as an index related to hardness, Young's modulus E = 3ρVs ² (ρ: density) may be calculated and displayed based on the speed Vs.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

  10 probe, 12 transmitting unit, 14 receiving unit, 20 image forming unit, 30 phase calculating unit, 40 speed calculating unit, 50 display processing unit, 52 display unit, 60 control unit.

Claims (5)

A probe for transmitting and receiving ultrasound,
A transmitter that outputs an ultrasonic transmission signal to the probe to measure the shear wave;
A reception unit for obtaining an ultrasonic reception signal for measuring a shear wave by processing a signal obtained from the probe;
Based on the received signal, a displacement measurement unit that generates displacement data indicating shear wave displacement over a plurality of time phases;
Based on the time differential data obtained by time differential processing the displacement data, a speed calculation unit that calculates the speed of the shear wave;
Having
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The displacement measuring unit generates displacement data for each position based on the received signals obtained from different positions,
The speed calculation unit generates time differential data by performing time differential processing on the displacement data for each position, and includes a characteristic time phase in the time differential data at the first position and a time differential data at the second position. Calculate the shear wave velocity based on the characteristic time phase,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The speed calculation unit, as the characteristic time phase in the time differential data at each position, based on at least one of the time phase of the maximum value, the time phase of the minimum value, and the time phase of the zero cross, Calculate speed,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The displacement measurement unit generates displacement data indicating temporal changes in the phase of the shear wave at each position based on the received signals obtained from different positions.
An ultrasonic diagnostic apparatus. In the ultrasonic diagnostic apparatus according to any one of claims 1 to 4,
The transmission unit outputs an ultrasonic transmission signal for generating a shear wave to the probe, and outputs an ultrasonic transmission signal for measuring the shear wave generated thereby to the probe.
An ultrasonic diagnostic apparatus.

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