JP2017148368A - Ultrasound diagnostic apparatus, method of controlling ultrasound diagnostic apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasound diagnostic apparatus, a method of controlling ultrasound diagnostic apparatus, and a program which use a simpler configuration to suitably smooth elasticity information.SOLUTION: An ultrasound diagnostic apparatus comprises: transmission/reception control means for causing an ultrasound probe to transmit an ultrasound wave to a subject and receiving a reception signal relating to the ultrasound wave; elasticity frame data generation means for generating elasticity frame data indicating elasticity information relating to the distortion of the subject, by using a first reception signal and a second reception signal relating to ultrasound waves reflected off the subject in a first pressurized state and a second pressurized state; correlation information generation means for generating correlation information relating to the first and second reception signals; addition coefficient acquisition means for acquiring an addition coefficient, based on at least one of the elasticity information and the correlation information; smoothing means for smoothing first elasticity frame data and second elasticity frame data generated at different times according to the addition coefficient; and display control means for causing smoothed elasticity information after smoothing to be displayed on display means.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an ultrasonic diagnostic apparatus, an ultrasonic diagnostic apparatus control method, and a program.

  Conventionally, an ultrasound image is reflected to reflect the internal structure of the subject by irradiating the subject with ultrasound from the ultrasound probe, receiving the reflected wave, and processing the obtained received signal. There is an ultrasonic diagnostic apparatus that provides diagnostic information of the internal structure by displaying on a display unit. Such an ultrasonic diagnostic apparatus is also used for human medical care as a non-invasive diagnostic apparatus.

  In the ultrasonic diagnostic apparatus, there is a technique for generating elasticity information reflecting the hardness of the internal structure of the subject and displaying it on a display unit. This elasticity information is generated by transmitting ultrasonic waves while applying pressure to the subject and calculating the distortion of the subject from the received signals of the reflected waves at two points in time when the pressurization states are different. The elasticity information is displayed as, for example, an elasticity image colored according to the hardness of each part of the subject. In addition, the elasticity information can be displayed in real time by sequentially calculating the elasticity information based on the new received signal.

However, if the difference in pressure applied to the subject is too small or too large at the two time points when the received signal is received, the strain cannot be calculated properly, and appropriate elasticity information cannot be obtained. As a result, when real-time display of elasticity information is performed, inappropriate elasticity information is frequently displayed, making it difficult to see the display, making it difficult to make an appropriate diagnosis.
On the other hand, by detecting the pressure applied to the subject and adding a plurality of elasticity information so as to increase the weighting of the elasticity information at the timing when an appropriate pressure is applied, and smoothing in the time axis direction There is a technique for displaying elastic information with high reliability (for example, Patent Document 1).

WO2008 / 010500 Publication

  However, the above-described conventional technique requires a means for detecting the pressure applied to the subject in order to determine the weighting in the smoothing process of the elasticity information, and thus there is a problem that the apparatus becomes complicated and large. is there.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus, a control method for the ultrasonic diagnostic apparatus, and a program capable of appropriately smoothing elasticity information with a simpler configuration.

In order to achieve the above object, the invention of the ultrasonic diagnostic apparatus according to claim 1 comprises:
An ultrasonic probe that transmits ultrasonic waves to the subject and receives reflected waves of the transmitted ultrasonic waves;
Transmission / reception control means for transmitting an ultrasonic wave by the ultrasonic probe and acquiring a reception signal related to the ultrasonic wave received by the ultrasonic probe;
Using the first received signal related to the ultrasonic wave reflected by the subject in the first pressurized state and the second received signal related to the ultrasonic wave reflected by the subject in the second pressurized state Elastic frame data generating means for generating elastic frame data indicating elastic information relating to strain of the subject;
Correlation information generating means for generating correlation information indicating a degree of correlation between the first received signal and the second received signal;
Acquisition of an addition coefficient for acquiring an addition coefficient used for smoothing processing of two elastic frame data generated at different times indicating the degree of reliability of the elasticity information based on at least one of the elasticity information and the correlation information Means,
The first elastic frame data and the second elastic frame data generated at a time different from the first elastic frame data are weighted according to the addition coefficient corresponding to the first elastic frame data. Smoothing processing means for generating elastic frame data smoothed by adding, and
Display control means for causing the display means to display the smoothed elasticity information indicated by the smoothed elastic frame data;
It is characterized by having.

The invention according to claim 2 is the ultrasonic diagnostic apparatus according to claim 1,
Storage means for storing a plurality of the addition coefficients respectively determined in advance in association with at least one of the elasticity information and the correlation information;
The addition coefficient acquisition means acquires the addition coefficient from the storage means.

The invention according to claim 3 is the ultrasonic diagnostic apparatus according to claim 1 or 2,
The correlation information generation means generates the correlation information for each elastic frame data,
The addition coefficient acquisition means acquires the addition coefficient for each elastic frame data based on at least one of the predetermined statistical amount of the elastic information in the elastic frame data and the correlation information.

The invention according to claim 4 is the ultrasonic diagnostic apparatus according to claim 1 or 2,
The correlation information generating means generates the correlation information for each acoustic line related to the received signal received at the same position of the ultrasonic probe,
The addition coefficient acquisition means, for each acoustic line corresponding area, based on at least one of the predetermined statistical amount of the elastic information and the correlation information in the acoustic line corresponding area corresponding to the acoustic line in the elastic frame data To obtain the addition coefficient,
The smoothing processing means is characterized in that the first elastic frame data and the second elastic frame data are weighted and added according to the addition coefficient for each acoustic ray corresponding region.

The invention according to claim 5 is the ultrasonic diagnostic apparatus according to claim 1 or 2,
The correlation information generation unit generates the correlation information for each local region having a predetermined size in the elastic frame data,
The addition coefficient acquisition means acquires the addition coefficient for each local region based on at least one of the predetermined statistical amount of the elasticity information in the local region of the elastic frame data and the correlation information,
The smoothing processing unit is characterized in that the first elastic frame data and the second elastic frame data are weighted and added according to the addition coefficient for each local region.

The invention according to claim 6 is the ultrasonic diagnostic apparatus according to claim 5,
The addition coefficient acquisition means acquires the addition coefficient that is larger as the hardness of the subject indicated by the predetermined statistic of the elasticity information in the local region is higher.

The invention according to claim 7 is the ultrasonic diagnostic apparatus according to any one of claims 3 to 6, wherein
The predetermined statistic of the elasticity information is an average value or a median value of the elasticity information.

The invention according to claim 8 is the ultrasonic diagnostic apparatus according to any one of claims 1 to 7,
The addition coefficient acquisition unit acquires the addition coefficient based on a predetermined statistic of the plurality of correlation information generated by the correlation information generation unit.

The invention according to claim 9 is the ultrasonic diagnostic apparatus according to any one of claims 1 to 8,
The transmission / reception control means transmits the ultrasonic wave while scanning in a predetermined scanning direction by the ultrasonic probe,
The addition coefficient acquisition means acquires the addition coefficient such that the higher the frame frequency indicating the scanning frequency, the smaller the weighting of the first elastic frame data in the smoothing.

The invention according to claim 10 is the ultrasonic diagnostic apparatus according to any one of claims 1 to 9,
The smoothing processing unit uses the smoothed elastic frame data as the second elastic frame data in a smoothing process performed after a smoothing process related to the smoothed elastic frame data. It is said.

In order to achieve the above object, an invention of a method for controlling an ultrasonic diagnostic apparatus according to claim 11 comprises:
A method for controlling an ultrasonic diagnostic apparatus including an ultrasonic probe that transmits ultrasonic waves to a subject and receives reflected waves of the transmitted ultrasonic waves,
A transmission / reception step of transmitting ultrasonic waves by the ultrasonic probe and acquiring a reception signal related to the ultrasonic waves received by the ultrasonic probe;
Using the first received signal related to the ultrasonic wave reflected by the subject in the first pressurized state and the second received signal related to the ultrasonic wave reflected by the subject in the second pressurized state An elastic frame data generating step for generating elastic frame data indicating elastic information relating to strain of the subject;
A correlation information generating step for generating correlation information indicating a degree of correlation between the first received signal and the second received signal;
Acquisition of an addition coefficient for acquiring an addition coefficient used for smoothing processing of two elastic frame data generated at different times indicating the degree of reliability of the elasticity information based on at least one of the elasticity information and the correlation information Step,
The first elastic frame data and the second elastic frame data generated at a time different from the first elastic frame data are weighted according to the addition coefficient corresponding to the first elastic frame data. A smoothing step of generating smoothed elastic frame data by adding,
A display step of displaying smoothed elasticity information indicated by the smoothed elastic frame data by a display means;
It is characterized by including.

In order to achieve the above object, an invention of a program according to claim 11 is:
Computer
A transmission / reception control means for transmitting an ultrasonic wave to a subject by an ultrasonic probe and acquiring a reception signal related to the reflected wave of the ultrasonic wave received by the ultrasonic probe;
Using the first received signal related to the ultrasonic wave reflected by the subject in the first pressurized state and the second received signal related to the ultrasonic wave reflected by the subject in the second pressurized state Elastic frame data generating means for generating elastic frame data indicating elastic information relating to strain of the subject,
Correlation information generating means for generating correlation information indicating a degree of correlation between the first received signal and the second received signal;
Acquisition of an addition coefficient for acquiring an addition coefficient used for smoothing processing of two elastic frame data generated at different times indicating the degree of reliability of the elasticity information based on at least one of the elasticity information and the correlation information means,
The first elastic frame data and the second elastic frame data generated at a time different from the first elastic frame data are weighted according to the addition coefficient corresponding to the first elastic frame data. Smoothing processing means for generating elastic frame data smoothed by adding,
Display control means for displaying smoothed elasticity information indicated by the smoothed elastic frame data by a display means;
It is characterized by making it function as.

  According to the present invention, there is an effect that elastic information can be appropriately smoothed with a simpler configuration.

1 is an overall view showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention. It is a block diagram which shows the internal structure of an ultrasonic diagnosing device. It is a figure explaining measurement of distortion. It is a figure explaining the calculation of distortion and the flow of image generation. It is a figure which shows the difference of the phase difference according to the magnitude | size of distortion in case the center frequency of an ultrasonic wave is the same. It is a figure which shows the relationship between the statistics of the value of distortion, the statistics of the correlation coefficient, and the addition coefficient α. It is a flowchart which shows the control procedure of an elasticity image display process. It is a flowchart which shows the control procedure of an elasticity image generation process. It is a figure which shows the example of the elastic image which concerns on the elastic frame data before smoothing, and the elastic frame data after smoothing. It is a figure explaining the influence which the fluctuation | variation of the difference of an applied pressure has on elastic frame data.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall view of an ultrasonic diagnostic apparatus U according to the present embodiment. FIG. 2 is a block diagram showing an internal configuration of the ultrasonic diagnostic apparatus U. As shown in FIG.

As shown in FIG. 1, the ultrasonic diagnostic apparatus U includes an ultrasonic diagnostic apparatus main body 1 and an ultrasonic probe 2 (ultrasonic probe) connected to the ultrasonic diagnostic apparatus main body 1 via a cable 22. With. The ultrasonic diagnostic apparatus main body 1 is provided with an operation input unit 18 and an output display unit 19 (display means). The control unit 15 of the ultrasonic diagnostic apparatus main body 1 outputs a drive signal to the ultrasonic probe 2 and outputs an ultrasonic wave based on an external input operation to an input device such as a keyboard or a mouse of the operation input unit 18. In addition, a reception signal related to ultrasonic reception is acquired from the ultrasonic probe 2 and various processes are performed, and the result and the like are displayed on the liquid crystal screen of the output display unit 19 as necessary. Note that the output display unit 19 may be provided outside the ultrasound diagnostic apparatus U without being included in the ultrasound diagnostic apparatus U.

  As shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes a transmission unit 12, a reception unit 13, a transmission / reception switching unit 14, a control unit 15 (display control unit, storage unit), an image processing unit 16, A storage unit 17, an operation input unit 18, an output display unit 19, and the like are provided. Among these, the transmission unit 12, the reception unit 13, and the control unit 15 constitute a transmission / reception control unit.

  The transmission unit 12 outputs a pulse signal to be supplied to the ultrasonic probe 2 in accordance with a control signal input from the control unit 15, and causes the ultrasonic probe 2 to generate an ultrasonic wave. The transmission unit 12 includes, for example, a clock generation circuit, a pulse generation circuit, a pulse width setting unit, and a delay circuit. The clock generation circuit is a circuit that generates a clock signal that determines the transmission timing and center frequency of a pulse signal. The pulse generation circuit is a circuit for generating a bipolar rectangular wave pulse having a preset voltage amplitude at a predetermined cycle. The pulse width setting unit sets the pulse width of the rectangular wave pulse output from the pulse generation circuit. The rectangular wave pulse generated by the pulse generation circuit is separated into different wiring paths for each transducer 21 of the ultrasonic probe 2 before or after input to the pulse width setting unit. The delay circuit is a circuit that delays and outputs the delay time set for each wiring path in accordance with the timing of transmitting the generated rectangular wave pulse to each transducer 21.

  The receiving unit 13 is a circuit that acquires a received signal input from the ultrasound probe 2 under the control of the control unit 15. The receiving unit 13 includes, for example, an amplifier, an A / D conversion circuit, and a phasing addition circuit. The amplifier is a circuit that amplifies a reception signal corresponding to the ultrasonic wave received by each transducer 21 of the ultrasonic probe 2 with a predetermined amplification factor set in advance. The A / D conversion circuit is a circuit that converts an amplified received signal into digital data at a predetermined sampling frequency. As for the sampling frequency, the Nyquist frequency needs to be higher than the reception frequency described later, and is, for example, 60 MHz. The phasing addition circuit adjusts the time phase by giving a delay time to each wiring path corresponding to each transducer 21 with respect to the A / D converted received signal, and adds these (phasing addition) to generate a sound. A circuit for generating line data.

  Based on the control of the control unit 15, the transmission / reception switching unit 14 transmits a drive signal from the transmission unit 12 to the transducer 21 when transmitting an ultrasonic wave from the transducer 21, while changing the ultrasonic wave emitted from the transducer 21. When such a signal is acquired, a switching operation for causing the reception unit 13 to output the reception signal is performed.

The control unit 15 includes a central processing unit (CPU), a hard disk drive (HDD), a random access memory (RAM), and the like. The CPU reads out various programs stored in the HDD, loads them into the RAM, and performs overall control of operations of the respective units of the ultrasonic diagnostic apparatus U according to the programs. The HDD stores a control program and various processing programs for operating the ultrasonic diagnostic apparatus U, various setting data, and the like. These programs and setting data may be stored in an auxiliary storage device using a non-volatile memory such as a flash memory in addition to the HDD so as to be able to be read / written and updated. The RAM is a volatile memory such as SRAM or DRAM, provides a working memory space for the CPU, and stores temporary data.
The setting data stored in the HDD of the control unit 15 includes an addition coefficient table 15a. Details of the addition coefficient table 15a will be described later.

Independent of the CPU of the control unit 15, the image processing unit 16 is a processing control unit 16a (elastic frame data) including a CPU, a RAM, and the like that perform arithmetic processing for creating a diagnostic image based on ultrasonic reception data. Generation means, correlation information generation means, addition coefficient acquisition means, smoothing processing means). This diagnostic image includes a B-mode image showing the structure of the subject by the luminance distribution, a D-mode image showing the blood flow state measured using the Doppler effect, and the elasticity showing the strain distribution inside the subject. Includes images. The diagnostic image includes image data to be displayed on the output display unit 19 in substantially real time, a series of moving image data thereof, snapshot still image data, and the like.
In addition, the structure by which the arithmetic processing by the process control part 16a is performed by CPU of the control part 15 may be sufficient.

  The storage unit 17 is a volatile memory such as a DRAM (Dynamic Random Access Memory), for example. Alternatively, the storage unit 17 may be various nonvolatile memories that can be rewritten at high speed. The storage unit 17 stores diagnostic image data in units of frames, which are processed by the image processing unit 16 and used for real-time display or display based thereon. The diagnostic image data stored in the storage unit 17 is read according to the control of the control unit 15 and transmitted to the output display unit 19 or output to the outside of the ultrasonic diagnostic apparatus U via a communication unit (not shown). Or At this time, when the display system of the output display unit 19 is a television system, a DSC (Digital Signal Converter) is provided between the storage unit 17 and the output display unit 19 to output after the scanning format is converted. It should be done.

  The operation input unit 18 includes a push button switch, a keyboard, a mouse, a trackball, or a combination thereof, converts a user input operation into an operation signal, and inputs the operation signal to the ultrasonic diagnostic apparatus body 1.

  The output display unit 19 is a display using any one of various display methods such as an LCD (Liquid Crystal Display), an organic EL (Electro-Luminescent) display, an inorganic EL display, a plasma display, and a CRT (Cathode Ray Tube) display. A screen and its drive unit are provided. The output display unit 19 generates a drive signal for the display screen (each display pixel) according to the control signal output from the CPU 15 and the diagnostic image data generated by the image processing unit 16, and performs ultrasonic diagnosis on the display screen. The menu, status, and measurement data based on the received ultrasound are displayed.

  The operation input unit 18 and the output display unit 19 may be provided integrally with the housing of the ultrasonic diagnostic apparatus main body 1 or attached to the outside via a USB cable or the like. There may be. Further, if the operation input terminal and the display output terminal are provided in the ultrasonic diagnostic apparatus main body 1, conventional peripheral devices for operation and display may be connected to these terminals for use.

  The ultrasonic probe 2 oscillates and emits (transmits) ultrasonic waves (here, about 1 to 30 MHz) to a subject such as a living body, and is reflected by the subject among the emitted ultrasonic waves. It functions as an acoustic sensor that receives reflected waves (echoes) and converts them into electrical signals. The ultrasonic probe 2 includes a transducer array 210 that is an array of a plurality of transducers 21 that transmit and receive ultrasonic waves, and a cable 22. The cable 22 has a connector (not shown) to the ultrasonic diagnostic apparatus main body 1 at one end, and the ultrasonic probe 2 is configured to be detachable from the ultrasonic diagnostic apparatus main body 1 by the cable 22. ing. The user operates the ultrasound diagnostic apparatus U by bringing the ultrasound transmitting / receiving surface of the ultrasound probe 2 into contact with the subject with a predetermined pressure, that is, the surface in the direction of emitting ultrasound from the transducer array 210. And perform an ultrasound diagnosis.

  The vibrator array 210 is an array of a plurality of vibrators 21 each including a piezoelectric element having a piezoelectric body and electrodes provided at both ends where charges appear due to deformation (extension / contraction). In the present embodiment, a predetermined scan is performed. It is a one-dimensional array in the direction SD. By sequentially supplying voltage pulses (pulse signals) to the vibrator 21, the piezoelectric bodies are deformed according to the electric field generated in each piezoelectric body, and ultrasonic waves are transmitted. Further, when an ultrasonic wave having a predetermined frequency band is incident on the vibrator 21, the thickness of the piezoelectric body fluctuates (vibrates) due to the sound pressure, thereby generating a charge corresponding to the fluctuation amount. Converted to electrical signal and output.

  The ultrasonic probe 2 transmits ultrasonic waves from the transducers 21 in the order of arrangement in the transducer array 210 based on the pulse signal from the transmission unit 12, so that the ultrasound probe 2 can be supersonic in the scanning direction SD parallel to the transducer array direction. A sound wave scan is performed. In the present embodiment, this ultrasonic scanning is repeatedly performed at a predetermined frame frequency. Further, in the receiving unit 13, in each scan, two-dimensional data (hereinafter also referred to as frame data) of the received signal from a reception signal (hereinafter also referred to as an acoustic line) related to the reflected wave received by each transducer 21. ) Is acquired.

The ultrasonic probe 2 has various electronic scanning methods such as a linear electronic scanning method, a sector electronic scanning method, and a convex electronic scanning method, and various mechanical scanning methods such as a linear scanning method, a sector scanning method, an arc scanning method, and a radial scanning method. Any method may be adopted.
Further, the ultrasonic diagnostic apparatus U can be configured to be usable by connecting any one of a plurality of different ultrasonic probes 2 depending on the diagnosis target to the ultrasonic diagnostic apparatus main body 1.
The ultrasonic probe 2 may include a pressure sensor, measure the pressure of the ultrasonic probe 2 on the subject, and output the pressure to the control unit 15. The ultrasonic probe 2 further includes a motor that moves the transmission / reception surface of the ultrasonic probe 2 back and forth in the ultrasonic transmission / reception direction, and may be pressed against the subject or released with a preset pressure. It may be possible.

Next, the distortion measurement operation in the ultrasonic diagnostic apparatus U of the present embodiment will be described.
In the ultrasonic diagnostic apparatus U of the present embodiment, the luminance is used to measure and display a B-mode in which one-dimensional or two-dimensional display related to tomographic examination is performed in substantially real time, or a blood flow state using the Doppler effect. In addition to the D mode, there is an elastic information display mode in which an elastic image representing the strain distribution of the internal structure is displayed superimposed on the B mode image. In the ultrasonic diagnostic apparatus U, the measurement operation of the strain of the subject is performed in the elasticity information display mode.

FIG. 3 is a diagram illustrating distortion measurement.
As shown in FIG. 3A, in the normal subject S, the depth direction (X) from the contact surface with the ultrasonic wave transmitting surface of the ultrasonic probe 2 on the upper surface of the subject S. The upper end of the structure T is at a position of distance xr in the direction). The width of the structure T in the X direction is L. As shown in FIG. 3 (b), when the pressure ρ (stress) is applied to the subject S from the upper surface side and the pressure ρ is similarly applied to the structure T, the upper end position of the structure T is The distance xs in the X direction and the width changes to L−ΔL.
Therefore, the strain ε = ΔL / L is obtained by measuring the structure T in these two states. At this time, the longitudinal elastic modulus (Young's modulus) E = ρ / ε can be calculated using the pressure ρ (stress) measured by the pressure sensor and displayed.

FIG. 4 is a diagram for explaining the flow of distortion calculation and image generation.
In the elasticity information display mode, ultrasonic waves are transmitted and received while applying a temporally changing pressure to the subject. The pressure change may be performed by an operator's hand, or may be realized by providing a pressing mechanism to the ultrasonic probe 2 and the pressing mechanism. Further, when the subject is a living body, a mode in which a change in pressure is caused by a movement according to the breathing of the subject with respect to the fixed ultrasonic probe 2 may be employed.
The ultrasonic waves are repeatedly scanned at a predetermined frame frequency, and frame data is acquired for each frame. Here, in the elastic information display mode of the present embodiment, the distortion (elastic information) is calculated using the frame data of the odd number, that is, the 2n-1 frame (n is a natural number), and an elastic image is generated. B-mode images are generated using the even-numbered, ie, 2nth frame data.

In two frames adjacent to each other in the odd-numbered frame group (two frames in which n is different by 1), the subject is in a state in which different pressures are applied to the same part (first pressurization state, second frame). Pressurized state). Therefore, in this embodiment, an elastic image is generated using the frame data of these two frames. That is, the frame data of each frame excluding the first and last frames in the odd-numbered frame group is used twice for calculating the distortion. An elastic image is obtained by performing processing such as smoothing and dynamic range adjustment for display on the two-dimensional data (hereinafter, also referred to as elastic frame data) of the calculated strain distribution. The elastic image is displayed on the output display unit 19 so as to be superimposed on the B-mode image, for example, in color display or gray scale display.
In this embodiment, a B-mode image or an elasticity image is sequentially generated and displayed for each frame, thereby displaying the internal structure of the subject in real time.

Next, a distortion calculation process in the ultrasonic diagnostic apparatus U of the present embodiment will be described.
In the ultrasonic diagnostic apparatus U of the present embodiment, an ultrasonic reception signal in a frame in which the pressure applied to the subject is relatively small out of the two frames used for distortion calculation is a waveform r ( t) (first received signal), and an ultrasonic received signal in a frame having a relatively high pressure is acquired as a compressed waveform s (t) (second received signal). Based on the waveform in the time range corresponding to the same region in the depth direction of the subject among the waveform r (t) at the time of extension and the waveform s (t) at the time of the compression, the distortion in the region is as follows. Calculated. Hereinafter, the data range used for calculating one distortion among the data of the waveform r (t) at the time of extension and the data of the waveform s (t) at the time of compression will be referred to as a correlation calculation region _RC .

The waveform r (t) during extension at each data acquisition timing (elapsed time t (time)) in the correlation calculation region _RC is
r (t) = A (t) cos (ω ₀ t + φ (t)) (1)
It is expressed. Here, ω ₀ is the center frequency of the received ultrasonic wave, A (t) is the time variation of the amplitude component (envelope of the received waveform), and φ (t) is the initial phase.
This waveform can be analytically represented by a complex function as follows.
r _a (t) = A (t) exp (iω ₀ t + φ (t)) (2)

On the other hand, in the waveform s (t) at the time of compression, the reflected wave with respect to a predetermined structure according to the strain ε (that is, the expansion rate, ε <0 at the time of compression) is shorter than the waveform r (t) at the time of extension, that is, in a short period. Will be observed. In addition, as the pressure is indirectly applied to the subject, the position of the inner subject moves from xr to xs, so the detection timing of the reflected wave, that is, the phase changes. -Compression waveform s (t) is distorted epsilon minute range (typically, e.g., 5% or less) in, as shown by the following equation (3), the distortion amount corresponding extension time waveform of epsilon r _{a (t} ) Is represented by a compressed waveform.
s _a (t) = A (t (1-ε)) exp (iω ₀ t (1-ε) + φ (t (1-ε)))
(3)

From these analytical solutions (2) and (3), the phase difference F _a (t) (phase difference component) between the waveform r _a (t) at the time of expansion and the waveform s _a (t) at the time of compression according to the following equation (4): Is required.
F _a (t) = Im (log (r _a (t) s _a ^* (t))) = εω ₀ t + δ (4)
Here, s _a ^* (t) is a complex conjugate of the compressed waveform s _a (t), and δ represents a phase shift (initial phase difference) associated with the above-described shift between the distance xs and the distance xr. That is, this phase difference F _a (t
) Is a linear function in which the slope is proportional to the distortion ε and the center frequency ω ₀ and the intercept is represented by the phase shift δ.
Therefore, the phase difference F _a (t) at each time obtained from the real part and imaginary part of the measured waveform r (t) at extension and the real part and imaginary part of the waveform s (t) at compression, The distortion ε in the correlation calculation region _RC can be obtained from the center frequency ω ₀ of the transmission ultrasonic wave.

The above-described calculation of the strain ε is performed for each of the plurality of correlation calculation regions _{RC in} the depth direction of the subject, and this processing is performed for each position in the ultrasound scanning direction, whereby the strain of the subject is determined. Elastic frame data indicating the two-dimensional distribution of the.

  Incidentally, as shown in the above equation (4), the phase difference between the waveform r (t) during extension and the waveform s (t) during compression is proportional to the strain ε, and the slope of the linear function indicating the phase difference is The smaller the strain ε, the smaller.

FIG. 5 is a diagram illustrating the difference in phase difference according to the magnitude of the strain ε when the center frequencies of the ultrasonic waves are the same. FIG. 5A shows the phase difference when the strain ε is ω ₁ , and FIG. 5B shows the phase difference when the strain ε is ε ₂ that is larger than ε ₁ . In FIG. 5A and FIG. 5B, the time range corresponding to the same correlation calculation region _RC is shown in the range from −t _C to t _C.
In both cases of FIG. 5A and FIG. 5B, the noise included in the received signal at each time is the same. Therefore, when the magnitudes of the correlation calculation regions _RC are equal, in the case of FIG. 5A where the slope of the linear function indicating the phase difference is small, the S related to the calculation result of the slope of the linear function (ie, distortion) is obtained. The / N ratio becomes relatively small, and it becomes difficult to calculate accurate distortion.

For this reason, in order to obtain highly reliable elastic frame data including appropriately calculated strain, the magnitude of the strain needs to be a certain value or more. In other words, if the difference in applied pressure to the subject is small and the strain is small between the acquisition of the waveform r (t) during extension and the waveform s (t) during compression, the elastic frame data is included in the elastic frame data. The error included in the included strain value increases, and the reliability of the elastic frame data decreases.
In this embodiment, since the elasticity image is displayed in real time, if the elasticity image related to the elasticity frame data with low reliability is frequently displayed, it is difficult to see the elasticity image display, and it is difficult to perform an appropriate diagnosis. Become.
On the other hand, when the pressure is applied to the subject by the operator's hand, or when the subject is a living body that constantly fluctuates, it is difficult to maintain the difference between the applied pressures at an appropriate value. It is inevitable that elastic frame data with low reliability is generated at the above ratio.

Therefore, in the present embodiment, a smoothing process is performed in which the weighting of highly reliable elastic frame data is increased and a plurality of elastic frame data is added, and such an elastic frame that has been smoothed in the time axis direction is performed. By displaying the elastic image (smoothed elasticity information) based on the data, the influence of the elastic frame data with low reliability on the display is reduced.
Below, this smoothing process is demonstrated.

In the ultrasonic diagnostic apparatus U of the present embodiment, when elastic frame data is acquired in a frame for generating an elastic image, two elastic frame data having different acquisition timings are added based on the following equation (5). To smooth in the time axis direction. That is, the two elastic frame data are weighted by the addition coefficient α and added.
_{Es t = αE t + (1} -α) E t-1 ... (5)
Here, E _t represents the value of the elastic frame data (first elastic frame data) acquired in the current frame, and E _t−1 represents a time (this time different from the elastic frame data related to the current frame). in the embodiment, shows the corresponding values in other elasticity frame data generated just before) the elasticity frame data of the current frame (the second elastic frame data), Es _t is smoothed elasticity frame data Indicates the value of.
When the elastic frame data smoothed by Expression (5) is generated, an elastic image related to the smoothed elastic frame data is displayed on the output display unit 19.
Further, in the frame where the elastic image is generated next, the value (Es _t ) of the smoothed elastic frame data is set to E _t−1 in the equation (5). That is, the elastic frame data E _t-1 is the smoothed elastic frame data when there is elastic frame data that has been smoothed immediately before.

The addition coefficient α is a predetermined statistic ε _t of the distortion value in the elastic frame data of the current frame and a correlation coefficient c indicating the degree of correlation between the received signals in the two frames used for the calculation of the distortion. It is obtained from a function f having a predetermined statistic _ct (correlation information) and the ultrasonic frame frequency τ as variables, and is expressed as α = f (ε _t , c _t , τ).
The strain statistic ε _t can be, for example, an average value or a median value of strain values in the elastic frame data.

The correlation coefficient c is obtained by the following equation (6) from the waveform at extension r (t) and the waveform at compression s (t).
c = (r (t) · s (t)) / (| r (t) || s (t) |) (6)
Therefore, the correlation coefficient c increases as the deviation between the waveform r (t) during extension and the waveform s (t) during compression decreases.
In the present embodiment, the correlation coefficient c is calculated for each correlation calculation region _RC , that is, for each pixel of the elastic frame data. Also, statistics c _t of the correlation coefficient c can be, for example, a mean or median value of a plurality of correlation coefficients c of the elastic frame data.
Note that one correlation coefficient c may be calculated from the expanded waveform r (t) and the compressed waveform s (t) related to the received signal of the entire frame data. In this case, the correlation coefficient c is used as it is for calculating the addition coefficient α, and the correlation coefficient c corresponds to the correlation information.
Further, the above equation (6) calculates the correlation coefficient c by NCC (Normalized Cross-Correlation) of the waveform at extension r (t) and the waveform at compression s (t), but is not limited thereto. The correlation coefficient c may be calculated by SSD (Sum of Squared Difference) or SAD (Sum of Absolute Difference).

FIG. 6 is a diagram illustrating the relationship between the distortion value statistic ε _t and the correlation coefficient c statistic _ct, and the addition coefficient α. 6, the horizontal axis statistics epsilon _t the distortion values are shown size trend of the addition coefficient α in each region when taking statistics c _t of the correlation coefficient c on the vertical axis .
Region r1 as shown in FIG. 6 is a statistic c _t is smaller both regions statistics epsilon _t and correlation coefficient c distortion values, for example, such as ultrasonic probe 2 to skid on the subject Corresponds to the case of illegal movement. For this reason, in such a region r1, the reliability of the elastic frame data is remarkably lowered, so the addition coefficient α is set to zero.
Region r2 is an area statistics c _t of the correlation coefficient c is small while the statistic epsilon _t the distortion values has a certain level of value. In this region r2, been shown to be distorted because the statistics c _t of the correlation coefficient c is small not properly calculated, for example, corresponds to the case by the error of the calculation as the value of the distortion is large . Therefore, since the reliability of the elastic frame data is low, the addition coefficient α is set small.
Regions r3 has a large statistic c _t of the correlation coefficient c, a statistic epsilon _t small area of distortion values. This is because the difference in the applied pressure to the subject between the two frames used for generating the elastic frame data is small, so that the waveform r (t) during extension and the waveform s (t) during compression are highly correlated. The calculated distortion is small. In such a case, as described above, since the S / N ratio related to the distortion calculated is small because the slope of the phase difference shown in Equation (4) and FIG. 5 is small, an error included in the distortion is reduced. growing. Therefore, since the reliability of the elastic frame data is lowered, the addition coefficient α is set small.
Region r4 has statistics epsilon _t is constant over the magnitude of the strain values, is a region statistic c _t of the correlation coefficient c is within a large and a predetermined range than the region r2. In this region r4, the difference in the applied pressure to the subject between the two frames used for generating the elastic frame data is an appropriate magnitude, resulting in a moderately distorted distortion. Calculated correctly. Therefore, since the reliability of the elastic frame data is high, the addition coefficient α is set large.
Further, although not shown in FIG. 6, the addition coefficient α is set to a smaller value as the frame frequency τ is higher.

In this embodiment, an addition coefficient α is predetermined for each possible combination of the distortion value statistic ε _t , the correlation coefficient c statistic _ct, and the frame frequency τ, and the addition coefficient α is added in the HDD of the control unit 15. It is stored as a coefficient table 15a. Then, in each frame to generate an elastic image, statistic epsilon _t, addition coefficient table 15a is referred to based on statistics c _t and frame frequency tau, suitable according to the reliability of the elastic frame data in the frame The addition coefficient α is acquired.

  Subsequently, an elastic image display process and an elastic image generation process executed by the ultrasonic diagnostic apparatus U will be described.

FIG. 7 is a flowchart showing a control procedure by the control unit 15 of the elastic image display process.
This elasticity image display process is executed when the elasticity information display mode is selected by the user's input operation to the operation input unit 18 or the like in the measurement display process related to ultrasonic diagnosis.

  When the elastic image display process is started, the control unit 15 performs a scanning operation based on the transmission / reception setting, that is, a transmission / reception operation related to one scan of the ultrasonic wave (step S101: transmission / reception step). Here, the control unit 15 outputs a pulse signal from the transmission unit 12 to the ultrasonic probe 2, and causes the ultrasonic probe 2 to scan and transmit ultrasonic waves at a predetermined center frequency and frame frequency. . Further, the control unit 15 causes the reception unit 13 to acquire a reception signal related to the reflected wave received by the ultrasound probe 2 at a predetermined sampling frequency, and causes the storage unit 17 to store the obtained frame data.

  The control unit 15 determines whether or not the current frame is the 2n + 1 frame from the start of scanning (step S102). If it is determined that the frame is the 2n + 1th frame (“YES” in step S102), the control unit 15 executes an elastic image generation process to be described later and stores the elastic image in the storage unit 17 (step S103). If it is determined that the frame is not the 2n + 1th frame (that is, the 2nth frame or the first frame) (“NO” in step S102), the control unit 15 performs an image based on the acquired frame data. Image data of a B-mode image is generated by the processing unit 16 and stored in the storage unit 17 (step S104). For the first frame, only frame data acquisition may be performed and B-mode image generation may not be performed.

  The control unit 15 causes the image processing unit 16 to generate composite image data of the latest elastic image and B-mode image, and causes the output display unit 19 to display an image related to the composite image data (step S105: display step).

The control unit 15 determines whether or not an input operation instructing to cancel the scanning operation is performed on the operation input unit 18 (step S106). When it is determined that the input operation has not been performed (“NO” in step S106), the control unit 15 shifts the process to step S101. If it is determined that the input operation is being performed (step S106)
The control unit 15 ends the elastic image display process.

FIG. 8 is a flowchart showing a control procedure by the process control unit 16a for the elastic image generation process.
When the elastic image generation processing is started, the processing control unit 16a acquires frame data of received signals in two adjacent odd-numbered frames, and aligns the ultrasound probe 2 in the scanning direction ( Step S201). The processing control unit 16a determines a combination of scanning positions corresponding to the same position by adjustment or pattern matching between preset positions.

The process control unit 16a uses the two frame data and the value of the center frequency of the transmission ultrasonic wave to calculate the distortion for each correlation calculation region _RC based on the algorithm described above, and generates elastic frame data. Further, the processing control unit 16a calculates a statistic ε _t of the distortion value of the elastic frame data (step S202: elastic frame data generation step). In the calculation of the distortion, the processing control unit 16a inverts the sign of the distortion value when the first received waveform data is a compressed waveform among the received waveform data related to the two frame data.

The processing control unit 16a calculates the correlation coefficient c of the received signals related to the two frames used for generating the elastic frame data in step S202 for each correlation calculation region _RC based on the above algorithm. The processing control unit 16a calculates a statistic _{c t} of the correlation coefficient c (step S203: correlation information generating step).

The process control unit 16a determines whether or not the current frame is the fifth frame or later (that is, the third or later frame among the odd-numbered frames) from the start of the scanning operation (step S204). If it is determined that the frame is the fifth frame or later (“YES” in step S204), the processing control unit 16a determines the statistic ε _t of the distortion value of the elastic frame data and the statistic of the correlation coefficient c. based on c _t and frame frequency τ refers to the addition coefficient table 15a, and acquires the α-addition coefficient corresponding to these values (step S205: addition coefficient acquisition step).

Processing control unit 16a, an elastic frame data E _t of the current frame calculated in step S202, and an elastic frame data E _t-1 which is generated immediately before the elastic frame data E _t, the above equation (5) adds weighted by addition coefficient α based on, it performs the smoothing processing for generating the smoothed elasticity frame data Es _t (step S206: smoothing step). When the process of step S206 ends, the process control unit 16a shifts the process to step S207.

If it is determined in step S204 that the current frame is before the fifth frame, that is, the third frame (“NO” in step S204), the process control unit 16a proceeds to step S207. Let This is because, in the third frame, there is no immediately preceding elastic frame data (E _t-1 ) to be smoothed.

Processing control unit 16a performs the scaling of the distortion value based on the dynamic range of the smoothed elasticity frame data Es _t. Further, the processing control unit 16a converts the distortion data into color data corresponding to the magnitude of the distortion in accordance with a predetermined display setting (step S207). For example, the largest distortion in the dynamic range is red, the smallest distortion is blue, and the intermediate distortion is an intermediate color between red and blue corresponding to the magnitude of the distortion.

The processing control unit 16a outputs the data of the two-dimensional image (elastic image) related to the strain subjected to scaling and color conversion and stores the data in the storage unit 17 (step S208).
When the process of step S208 ends, the process control unit 16a ends the elasticity image generation process.

FIG. 9 is a diagram illustrating an example of an elastic image related to elastic frame data before smoothing and an elastic image related to elastic frame data after smoothing.
Elastic images Pa1 to Pa5 in FIG. 9 are elastic images based on the unsmoothed elastic frame data respectively generated in five consecutive odd-numbered frames, and the elastic images Pb1 to Pb5 are smoothed in the five frames. It is the elasticity image based on the elasticity frame data by which the conversion processing was made. Further, in each elastic image of FIG. 9, color conversion is performed such that the density increases as the strain value decreases (that is, the hardness of the subject increases).

In each elastic image in FIG. 9, a range including two substantially circular structures T (living tissue) whose hardness is relatively higher than that of the surroundings is displayed. However, among the elastic images Pa1 to Pa5 before smoothing, especially in the elastic images Pa2 to Pa4 in the second to fourth frames, noise is increased due to the small distortion. The structure T is unclear compared to the elasticity images Pa1 and Pa5 in the fifth frame.
On the other hand, in the elastic images Pb1 to Pb5 after smoothing, the structure T is clearly displayed in any frame. This is because the influence of the elastic frame data having low reliability related to each frame is suppressed by the smoothing performed by selecting the small addition coefficient α in the second to fourth frames where the noise is large. . Thus, according to this embodiment, even if the reliability of the elastic frame data in each frame is low, an appropriate elastic image can be displayed by performing smoothing based on the addition coefficient α.

As described above, the ultrasonic diagnostic apparatus U of the present embodiment transmits the ultrasonic wave to the subject and receives the reflected wave of the transmitted ultrasonic wave, the ultrasonic probe 2 and the ultrasonic probe. A transmitter 12, a receiver 13 and a controller 15 (transmission / reception control means) for transmitting an ultrasonic wave by the probe 2 and acquiring a reception signal related to the ultrasonic wave received by the ultrasonic probe 2, and an image processing unit 16 process control units 16a, and the process control unit 16a is reflected by the first received signal related to the ultrasound reflected by the subject in the first pressurization state and by the subject in the second pressurization state. Using the second received signal related to the ultrasonic wave, elastic frame data indicating strain (elastic information) of the subject is generated (elastic frame data generating means), and the first received signal and the second received signal are generated. calculating statistics c _t of the correlation coefficient c which indicates the degree of correlation between the (correlation information Distribution generating means), based on statistics c _t statistics epsilon _t and correlation coefficient c strain according to elasticity information, the two elastic frame data of the degree of reliability shown generated at different times of the elasticity information An addition coefficient α used for the smoothing process is acquired (addition coefficient acquisition means), and the first elastic frame data (E _t ) and the second elastic frame generated at a different time from the first elastic frame data The data (E _t-1 ) is weighted according to the addition coefficient α corresponding to the first elastic frame data and added to generate smoothed elastic frame data (Es _t ) (smoothing process) The control unit 15 causes the output display unit 19 to display the smoothed elasticity information indicated by the smoothed elastic frame data (display control unit).
According to such a configuration, the addition coefficient α corresponding to the reliability of the elastic information can be acquired based on the ultrasonic reception signal. Therefore, since it is not necessary to provide other means such as a means for detecting the pressure applied to the subject in order to determine the addition coefficient α, the elastic information can be appropriately smoothed with a simpler configuration.

The ultrasonic diagnostic apparatus U has an HDD for storing a plurality of addition coefficient α defined respectively in association with statistic c _t pre distortion statistics epsilon _t and correlation coefficient c as an addition coefficient table 15a A control unit 15 (storage unit) is provided, and the process control unit 16a acquires the addition coefficient α from the addition coefficient table 15a of the control unit 15 (addition coefficient acquisition unit). Thereby, an appropriate addition coefficient α can be easily obtained by referring to the addition coefficient table 15a. Further, by previously seeking each corresponding addition coefficient α on a combination of statistics c _t pre distortion statistics epsilon _t and correlation coefficient c, it is possible to simplify the process of smoothing the elasticity frame data .

The processing control unit 16a generates a statistic c _t of the correlation coefficient c for each elastic frame data (correlation information generating means), statistics epsilon _t and correlation coefficient c strain values in the elastic frame data based on the statistic c _t acquires the addition coefficient α for each elastic frame data (addition coefficient obtaining means). According to such a configuration, it is possible to perform a smoothing process by calculating the statistic c _t statistics epsilon _t and correlation coefficient c by a simple process.

Further, the addition coefficient α can be acquired based on the statistic ε _t that appropriately reflects the distribution of distortion by setting the statistic ε _t of the distortion value as an average value or a median value of the distortion values. it can.

The processing control unit 16a obtains the addition coefficient α based on a predetermined statistical amount c _t of the plurality of correlation coefficients c (addition coefficient obtaining means). According to such a configuration, an appropriate addition coefficient α corresponding to the distribution of the correlation coefficient c can be acquired.

  The transmitting unit 12 transmits the ultrasonic wave while scanning the ultrasonic probe 2 in a predetermined scanning direction, and the processing control unit 16a performs the first smoothing process as the frame frequency τ indicating the scanning frequency increases. The addition coefficient α is acquired so that the weighting of the elastic frame data is reduced (addition coefficient acquisition means). According to such a configuration, when the frame frequency τ is high, it is possible to suppress the change of the elastic image for each frame and stabilize the display of the elastic image.

  Further, the process control unit 16a uses the smoothed elastic frame data as the second elastic frame data in the smoothing process performed after the smoothing process related to the smoothed elastic frame data (smoothed). Processing means). Thus, the process of adding and smoothing the first elastic frame data relating to the current frame and the second elastic frame data smoothed before the first elastic frame data is continuously performed. Elasticity with the weight of the most reliable elastic frame data increased while reflecting the information of a large number of past elastic frame data by simple processing by sequentially performing on the plurality of elastic frame data generated in Frame data can be generated.

In addition, in the control method of the ultrasonic diagnostic apparatus U according to the present embodiment, the ultrasonic probe 2 transmits ultrasonic waves, and the transmission / reception for acquiring the reception signals related to the ultrasonic waves received by the ultrasonic probe 2 is performed. Step, using a first reception signal related to the ultrasound reflected by the subject in the first pressurization state and a second reception signal related to the ultrasound reflected from the subject in the second pressurization state , elasticity frame data generating step of generating elastic frame data indicating a distortion of the object (elasticity information), statistics of the correlation coefficient c which indicates the degree of correlation between the first received signal and second received signal c _t correlation information generating step of calculating, based on the statistic c _t statistics epsilon _t and correlation coefficient c strain according to elasticity information, two elastic generated at different times indicates the degree of reliability of the elasticity information Used for smoothing frame data Addition coefficient acquisition step of acquiring addition coefficient alpha, the first elastic frame data (E _t), the second elastic frame data generated at different times than the first elasticity frame data (E _t-1) Is weighted in accordance with the addition coefficient α corresponding to the first elastic frame data, and is added by a smoothing step for generating smoothed elastic frame data (Es _t ), by the smoothed elastic frame data A display step of displaying the displayed smoothed elasticity information by the output display unit 19. According to such a control method, elasticity information can be appropriately smoothed with a simpler configuration.

Further, the program according to the present embodiment causes the ultrasonic diagnostic apparatus U as a computer to transmit ultrasonic waves to the subject using the ultrasonic probe 2 and receives the ultrasonic waves received by the ultrasonic probe 2. Transmission / reception control means for acquiring a reception signal related to the reflected wave of the first, a first reception signal related to the ultrasonic wave reflected by the subject in the first pressurization state, and an ultrasonic wave reflected by the subject in the second pressurization state Elastic frame data generating means for generating elastic frame data indicating strain (elastic information) of the subject using the second received signal related to the sound wave, correlation between the first received signal and the second received signal correlation information generating means for calculating a statistic c _t of the correlation coefficient c showing the extent, based on statistics c _t statistics epsilon _t and correlation coefficient c strain according to elasticity information, the elasticity information of the reliability Two generated at different times indicating the degree Addition coefficient acquisition means for acquiring an addition coefficient α used for smoothing processing of the elasticity frame data, first elasticity frame data, and second elasticity frame data generated at a time different from the first elasticity frame data; Is weighted according to the addition coefficient corresponding to the first elastic frame data, and is added to the smoothing processing means for generating the smoothed elastic frame data, and the smoothing indicated by the smoothed elastic frame data It functions as display control means for displaying elasticity information on the output display unit 19. According to such a program, the elasticity information can be appropriately smoothed by the ultrasonic diagnostic apparatus U having a simpler configuration.

(Modification 1)
Subsequently, Modification 1 of the above embodiment will be described.
This modification is different from the above embodiment in that smoothing is performed by setting an addition coefficient α for each acoustic line. Hereinafter, differences from the above embodiment will be described.

  Depending on the frame frequency of the ultrasound scan and the temporal change rate of the pressure applied to the subject, the difference in the pressure applied to the subject may fluctuate from the most recent frame within one frame period. is there.

FIG. 10 is a diagram for explaining the influence of the variation in the applied pressure difference on the elastic frame data.
The upper part of FIG. 10 shows the time change of the difference in the applied pressure to the subject from the most recent frame in one frame period. In FIG. 10, the difference in applied pressure changes periodically. Further, it is assumed that the subject to which pressure is applied has a uniform hardness.
In the lower part of FIG. 10, elastic frame data generated in each frame period is shown. The elastic frame data is stored in the acoustic line corresponding areas a1, a2, a3,... Corresponding to the acoustic lines related to the received signals received at the same position of the ultrasound probe 2 (that is, by the same transducer 21). Consists of. In this modification, the difference in the applied pressure to the subject changes within the frame period, and therefore the difference in the applied pressure when each acoustic line is received is different. Due to this, although the hardness of the subject is uniform, the calculated distortion value is different for each acoustic line (that is, for each acoustic line corresponding region). The elastic frame data in FIG. 10 indicates that the darker the color, the smaller the calculated strain value. From FIG. 10, it can be seen that the strain value calculated when the applied pressure difference is 0 is the smallest, and the calculated strain value increases as the applied pressure difference increases.

  As described above, when the difference in applied pressure fluctuates within the frame period, an artifact indicating a strain distribution unrelated to the hardness distribution of the subject is generated in the elastic frame data. Therefore, in one elastic frame data, the acoustic line corresponding area with high reliability and the acoustic line corresponding area with low reliability are mixed.

Therefore, in this modified example, statistics c _t statistics epsilon _t and correlation coefficient c distortion values for each acoustic line corresponding area is calculated, the statistic epsilon _t, the statistic c _t and frame frequency τ Based on this, the addition coefficient α is acquired for each acoustic line corresponding region. In the smoothing process of the elastic frame data, the elastic frame data is added for each acoustic ray corresponding region based on the addition coefficient α.
In the present modification, the process of step S202 in the flowchart of FIG. 8 according to the above embodiment is changed to a process of calculating a distortion value statistic ε _t for each acoustic line corresponding region. Further, the process of step S203 is changed to the processing for calculating the statistic c _t of the correlation coefficient c for each acoustic line corresponding region. Further, the process of step S205 is the statistic epsilon _t, is changed to the process of acquiring the addition coefficient α for each acoustic line corresponding region based on statistics c _t and frame frequency tau. Further, the process of step S206 is changed to a process of adding elastic frame data for each acoustic ray corresponding region using the addition coefficient α.

As described above, in the ultrasonic diagnostic apparatus U according to the present modification, the processing control unit 16a sets the correlation coefficient c for each acoustic line related to the received signal received at the same position of the ultrasonic probe 2. calculating statistics c _t (correlation information generating means), based on statistics c _t statistics epsilon _t and correlation coefficient c strain values in the acoustic line corresponding region corresponding to the acoustic line of the elasticity frame data Then, the addition coefficient α is acquired for each acoustic line corresponding area (addition coefficient acquiring means), and the first elastic frame data and the second elastic frame data are weighted according to the addition coefficient α for each acoustic line corresponding area. Are added (smoothing processing means). According to such a configuration, it is possible to suppress the occurrence of artifacts due to fluctuations in the difference in pressure applied to the subject within the frame period. As a result, a more reliable elastic image can be displayed, and a high-quality elastic image in which artifacts are suppressed can be displayed.

(Modification 2)
Then, the modification 2 of the said embodiment is demonstrated.
This modification is different from the above-described embodiment in that smoothing is performed by setting the addition coefficient α for each local region having a predetermined size in the elastic frame data. Hereinafter, differences from the above embodiment will be described.

  When the hardness of the subject is not uniform, the distortion value calculated from the received signal increases as the hardness decreases. Since the amount of variation in the strain value when the applied pressure varies is large at a portion where the distortion is large, the image quality and the visibility of the elastic image are more likely to fluctuate than the portion where the distortion is small. Therefore, by performing smoothing by selectively reducing the addition coefficient relating to a part having a low hardness, that is, a part having a large strain, the fluctuation of the part in the elastic frame data for each frame can be suppressed, and the image quality of the elastic image can be reduced. Visibility can be stabilized.

To perform the smoothing as described above, in this modification, the calculated statistic c _t statistics epsilon _t and correlation coefficient c distortion value for each local region of the elastic frame data, the statistic epsilon _t The addition coefficient α is acquired for each local region based on the statistic _ct and the frame frequency τ. Here, the addition coefficient α is selected so that the addition coefficient α increases in the local region where the distortion is larger. In the elastic frame data smoothing process, the elastic frame data is added for each local region based on the addition coefficient α.
Although the size of the local region is not particularly limited, the smoothing process more accurately corresponding to the hardness distribution of the subject can be performed as the local region is reduced. Therefore, it is most desirable that the size of the local region is one pixel of the elastic frame data. When the local area is one pixel, the distortion coefficient of one image corresponding to one correlation calculation area _RC is used instead of the distortion value statistic ε _t for the calculation of the addition coefficient α. is also the correlation coefficient c itself in the pixel is used instead of the statistic c _t of the correlation coefficient c. In this case, the correlation coefficient c corresponds to the correlation information.
In the present modification, the process of step S202 in the flowchart of FIG. 8 according to the above embodiment is changed to a process of calculating a distortion value statistic ε _t for each local region. Further, the process of step S203 is changed to the processing for calculating the statistic c _t of the correlation coefficient c for each local region. Further, the process of step S205 is the statistic epsilon _t, is changed to the process of obtaining the α addition coefficient for each local region on the basis of the statistic c _t and frame frequency tau. Further, the process of step S206 is changed to a process of adding elastic frame data for each local region using the addition coefficient α.

As described above, in the ultrasonic diagnostic apparatus U according to this modification, the processing control unit 16a calculates the statistic c _t of the correlation coefficient c for each local region of a predetermined size of the elasticity frame data ( correlation information generating means), based on statistics c _t statistics epsilon _t and correlation coefficient c strain values in a local region of the elasticity frame data to get the addition coefficient α for each local region (addition coefficient acquiring means ) The first elastic frame data and the second elastic frame data are weighted and added according to the addition coefficient α for each local region (smoothing processing means). According to such a configuration, since an appropriate addition coefficient is set for each local region of the elastic frame data and smoothing is performed, the change of the local region in the elastic image between frames becomes smooth, and the elastic image is more It can be stabilized. As a result, the display of the elastic image on the output display unit 19 can be made easier to visually recognize.

Further, the processing control unit 16a acquires the larger addition coefficient α as the hardness of the subject indicated by the statistic ε _t of the distortion value in the local region is higher (addition coefficient acquisition unit). As a result, when the hardness of the subject is not uniform, the variation of the region corresponding to the relatively low hardness portion of the elastic frame data (region with high strain) is suppressed for each frame, and the image quality of the elastic image Visibility can be stabilized.

(Modification 3)
Subsequently, Modification 3 of the above embodiment will be described. This modification may be combined with Modification 1 or Modification 2 described above.
In this modification, the addition coefficient α is set in consideration of the reliability of the elastic frame data generated immediately before the elastic frame data in addition to the reliability of the elastic frame data of the current frame. And different. Hereinafter, differences from the above embodiment will be described.

  In the above embodiment, smoothing is performed based on the addition coefficient α indicating the reliability of the elastic frame data related to the current frame. However, the reliability of the elastic frame data and the elastic frame data immediately before the addition target ( More appropriate smoothing can be performed by determining the addition coefficient α in consideration of the relative relationship with the reliability of the elastic frame data before smoothing). For example, the smaller the reliability of the immediately preceding elastic frame data, the greater the reliability of the elastic frame data of the current frame with respect to the immediately preceding elastic frame data. Therefore, it is appropriate to increase the addition coefficient α. .

Therefore, in the present modification, the addition coefficient related to the elastic frame data of the current frame determined by the function f (ε _t , c _t , τ) is used for the smoothing process in the previous frame by the addition coefficient α _t . When the obtained addition coefficient is the addition coefficient α _t−1 , the final addition coefficient α is determined by the following equation (7).
α = α _t / (α _t + α _t−1 ) (7)
Instead of the above, by using the function g plus statistics c _t-1 of the statistic epsilon _t-1 and the correlation coefficient c strain values according to the elastic frame data in a variable immediately before, alpha = g The addition coefficient α may be determined from (ε _t , c _t , ε _t−1 , c _t−1 , τ).

As mentioned above, although embodiment and the modification of this invention were demonstrated, this invention is not restricted to the said embodiment and each modification, Various changes are possible.
For example, in the above embodiment and the modifications, an example was described in which determining the addition coefficient α using both statistics c _t distortion statistics epsilon _t and correlation coefficient c of the current elastic frame data However, it is not intended to be limited to this. For example, may be a mode for acquiring addition coefficient α based on either one and the frame frequency τ of statistics c _t of the current elastic frame data distortion statistics epsilon _t and correlation coefficient c of the or it may be a mode for acquiring addition coefficient α based on only one of the statistic epsilon _t and statistic c _t.

  Moreover, although the said embodiment and each modification demonstrated using the example which calculates the correlation coefficient c from the waveform r (t) at the time of extension, and the waveform s (t) at the time of compression, it is not restricted to this. For example, the correlation coefficient c may be calculated from comparison of pixel data of a B-mode image between two frames or comparison of calculated strain values (elastic information).

In the above embodiment and each modification, the addition coefficient table 15a is stored in the HDD of the control unit 15, and the calculation parameter is obtained with reference to the addition coefficient table 15a. Then, the addition coefficient α may be calculated by the control unit 15 (or the processing control unit 16a) based on a predetermined function f (or function g).
Alternatively, the addition coefficient table 15a may be stored in a storage device outside the ultrasound diagnostic apparatus U, and the addition coefficient α may be acquired from the storage device via a communication unit (not shown).

Moreover, although the said embodiment and each modification demonstrated using the example which calculates distortion from the inclination of the linear function of a phase difference by Numerical formula (4), distortion may be calculated by another system. For example, a two-dimensional correlation calculation region _RC in the ultrasonic scanning direction and depth direction is set, and each correlation calculation region _RC in the frame data before compression is a predetermined search region of the frame data after compression. A method may be used in which the position is displaced and the distortion is calculated from the displacement.

  In the above-described embodiment and each modification, an elastic image showing a two-dimensional distribution of strain has been described as an example. However, the elastic image is another image related to the strain of the subject in response to pressurization on the subject. For example, an image showing a distribution of elastic modulus and a distribution of displacement of each part may be used. That is, the elasticity information indicated by the elasticity image may be an elastic modulus or a displacement in addition to the strain.

  Moreover, although the said embodiment and each modification demonstrated using the example which displays the elasticity information on the output display part 19 as an elasticity image, the display aspect of elasticity information is not restricted to such an elasticity image. For example, the elasticity information may be displayed on the output display unit 19 as a graph or text indicating statistical information such as a strain distribution histogram, standard deviation, and representative value (average value or median value).

  In the above-described embodiment and each modification, the elastic image is generated based on the odd-numbered frame reception signal, and the B-mode image is generated based on the even-numbered frame reception signal. Instead of this, the reception signal of each frame may be used for both the generation of the elastic image and the generation of the B-mode image.

  Moreover, in the said embodiment and each modification, it is not restricted to the display screen of the output display part 19, An external apparatus and an external display may be sufficient. Further, it may be possible to output directly to a print output, or numerical data may be output to an external device instead of as image data.

  In addition, the image processing unit 16 of the above embodiment and each modification may be provided independently of the ultrasonic probe 2 and other parts of the ultrasonic diagnostic apparatus main body 1. That is, a dedicated signal processing device may be used. In addition, since the signal processing of the present invention can be realized by ordinary software processing, the software is installed in a computer such as an ordinary PC, and is executed using the waveform data input by the control unit (CPU) of the computer. You may do it.

Moreover, in the said embodiment and each embodiment, although the case where the distortion | strain of a biological tissue was calculated | required was mentioned as an example as a medical device, the calculation object of distortion is not restricted to a biological tissue. As long as pressure is appropriately applied to the internal object, the present invention can be appropriately used for a building structure, various products having a small structure, and the like.

  Although several embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, and includes the scope of the invention described in the claims and equivalents thereof. .

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 12 Transmission part (transmission / reception control means)
13 Receiver (Transmission / reception control means)
14 Transmission / reception switching unit 15 Control unit (display control unit, storage unit)
15a addition coefficient table 16 image processing section 16a processing control section (elastic frame data generation means, correlation information generation means, addition coefficient acquisition means, smoothing processing means)
17 Storage Unit 18 Operation Input Unit 19 Output Display Unit (Display Unit)
21 transducer 210 transducer array 22 cable a1, a2, a3 acoustic line corresponding region _RC correlation calculation region S subject T structure U ultrasonic diagnostic apparatus

Claims (12)

An ultrasonic probe that transmits ultrasonic waves to the subject and receives reflected waves of the transmitted ultrasonic waves;
Transmission / reception control means for transmitting an ultrasonic wave by the ultrasonic probe and acquiring a reception signal related to the ultrasonic wave received by the ultrasonic probe;
Using the first received signal related to the ultrasonic wave reflected by the subject in the first pressurized state and the second received signal related to the ultrasonic wave reflected by the subject in the second pressurized state Elastic frame data generating means for generating elastic frame data indicating elastic information relating to strain of the subject;
Correlation information generating means for generating correlation information indicating a degree of correlation between the first received signal and the second received signal;
Acquisition of an addition coefficient for acquiring an addition coefficient used for smoothing processing of two elastic frame data generated at different times indicating the degree of reliability of the elasticity information based on at least one of the elasticity information and the correlation information Means,
The first elastic frame data and the second elastic frame data generated at a time different from the first elastic frame data are weighted according to the addition coefficient corresponding to the first elastic frame data. Smoothing processing means for generating elastic frame data smoothed by adding, and
Display control means for causing the display means to display the smoothed elasticity information indicated by the smoothed elastic frame data;
An ultrasonic diagnostic apparatus comprising: Storage means for storing a plurality of the addition coefficients respectively determined in advance in association with at least one of the elasticity information and the correlation information;
The ultrasonic diagnostic apparatus according to claim 1, wherein the addition coefficient acquisition unit acquires the addition coefficient from the storage unit. The correlation information generation means generates the correlation information for each elastic frame data,
The said addition coefficient acquisition means acquires the said addition coefficient for every said elastic frame data based on the predetermined statistic of the said elasticity information in the said elastic frame data, and at least one of the said correlation information. The ultrasonic diagnostic apparatus according to 1 or 2. The correlation information generating means generates the correlation information for each acoustic line related to the received signal received at the same position of the ultrasonic probe,
The addition coefficient acquisition means, for each acoustic line corresponding area, based on at least one of the predetermined statistical amount of the elastic information and the correlation information in the acoustic line corresponding area corresponding to the acoustic line in the elastic frame data To obtain the addition coefficient,
The smoothing processing unit adds the first elastic frame data and the second elastic frame data by weighting according to the addition coefficient for each acoustic ray corresponding region. The ultrasonic diagnostic apparatus according to 1 or 2. The correlation information generation unit generates the correlation information for each local region having a predetermined size in the elastic frame data,
The addition coefficient acquisition means acquires the addition coefficient for each local region based on at least one of the predetermined statistical amount of the elasticity information in the local region of the elastic frame data and the correlation information,
The smoothing processing unit adds the first elastic frame data and the second elastic frame data by weighting according to the addition coefficient for each local region. 2. The ultrasonic diagnostic apparatus according to 2.   6. The method according to claim 5, wherein the addition coefficient acquisition unit acquires the larger addition coefficient as the hardness of the subject indicated by the predetermined statistic of the elasticity information in the local region is higher. Ultrasonic diagnostic equipment.   The ultrasonic diagnostic apparatus according to claim 3, wherein the predetermined statistic of the elasticity information is an average value or a median value of the elasticity information.   The said addition coefficient acquisition means acquires the said addition coefficient based on the predetermined statistic of the said some correlation information produced | generated by the said correlation information production | generation means, The any one of Claims 1-7 characterized by the above-mentioned. An ultrasonic diagnostic apparatus according to 1. The transmission / reception control means transmits the ultrasonic wave while scanning in a predetermined scanning direction by the ultrasonic probe,
The said addition coefficient acquisition means acquires the said addition coefficient so that the weight of the said 1st elastic frame data in the said smoothing becomes small, so that the frame frequency which shows the frequency of the said scanning is high. The ultrasonic diagnostic apparatus as described in any one of -8.   The smoothing processing unit uses the smoothed elastic frame data as the second elastic frame data in a smoothing process performed after a smoothing process related to the smoothed elastic frame data. The ultrasonic diagnostic apparatus according to any one of claims 1 to 9. A method for controlling an ultrasonic diagnostic apparatus including an ultrasonic probe that transmits ultrasonic waves to a subject and receives reflected waves of the transmitted ultrasonic waves,
A transmission / reception step of transmitting ultrasonic waves by the ultrasonic probe and acquiring a reception signal related to the ultrasonic waves received by the ultrasonic probe;
Using the first received signal related to the ultrasonic wave reflected by the subject in the first pressurized state and the second received signal related to the ultrasonic wave reflected by the subject in the second pressurized state An elastic frame data generating step for generating elastic frame data indicating elastic information relating to strain of the subject;
A correlation information generating step for generating correlation information indicating a degree of correlation between the first received signal and the second received signal;
Acquisition of an addition coefficient for acquiring an addition coefficient used for smoothing processing of two elastic frame data generated at different times indicating the degree of reliability of the elasticity information based on at least one of the elasticity information and the correlation information Step,
The first elastic frame data and the second elastic frame data generated at a time different from the first elastic frame data are weighted according to the addition coefficient corresponding to the first elastic frame data. A smoothing step of generating smoothed elastic frame data by adding,
A display step of displaying smoothed elasticity information indicated by the smoothed elastic frame data by a display means;
A method for controlling an ultrasonic diagnostic apparatus. Computer
A transmission / reception control means for transmitting an ultrasonic wave to a subject by an ultrasonic probe and acquiring a reception signal related to the reflected wave of the ultrasonic wave received by the ultrasonic probe;
Using the first received signal related to the ultrasonic wave reflected by the subject in the first pressurized state and the second received signal related to the ultrasonic wave reflected by the subject in the second pressurized state Elastic frame data generating means for generating elastic frame data indicating elastic information relating to strain of the subject,
Correlation information generating means for generating correlation information indicating a degree of correlation between the first received signal and the second received signal;
Acquisition of an addition coefficient for acquiring an addition coefficient used for smoothing processing of two elastic frame data generated at different times indicating the degree of reliability of the elasticity information based on at least one of the elasticity information and the correlation information means,
The first elastic frame data and the second elastic frame data generated at a time different from the first elastic frame data are weighted according to the addition coefficient corresponding to the first elastic frame data. Smoothing processing means for generating elastic frame data smoothed by adding,
Display control means for displaying smoothed elasticity information indicated by the smoothed elastic frame data by a display means;
A program characterized by functioning as