WO2017169332A1 - Ultrasonic imaging device and ultrasonic reception signal processing method - Google Patents

Abstract

Provided is an ultrasonic imaging device capable of accurately assessing the tissue properties of an organism. According to the present invention, an ultrasonic wave is transmitted toward a subject to be inspected through which a wave is being propagated, and an ultrasonic wave from the subject to be inspected is received so that a reception signal is obtained. The speed of the wave being propagated through the subject to be inspected is calculated on the basis of the reception signal. A post-addition physical property value is obtained by adding, at a predetermined ratio, the physical property value of a first tissue and the physical property value of a second tissue by using the physical property value of the first tissue and the physical property value of the second tissue having been obtained in advance. The ratio is set such that the propagation speed, of the wave, corresponding to the post-addition physical property value corresponds to the calculated speed of the wave. The obtained ratio is used as a value of an index indicating the composition property of the subject to be inspected.

Description

Ultrasonic imaging apparatus and ultrasonic reception signal processing method

The present invention relates to an ultrasonic imaging apparatus and a method of processing an ultrasonic reception signal, and relates to a technique for evaluating the properties of a living tissue by generating a shear wave in a subject and measuring the propagation speed thereof.

Medical image display devices represented by ultrasound, magnetic resonance (MRI), and X-ray CT (Computed Tomography) are widely used as devices that present in-vivo information in the form of numerical values or images. Yes. In particular, an image display device using ultrasonic waves has a higher time resolution than other devices, and has the ability to image a heart under pulsation without bleeding.

Ultrasound propagating in the living body of the subject is mainly classified into longitudinal waves and transverse waves, and in many of the technologies installed in the product, that is, the technology to visualize the tissue form and the technology to measure the blood flow velocity, Mainly information on longitudinal waves (sound speed of about 1540 m / s) is used.

In recent years, a technique for evaluating the elastic modulus of a tissue using a transverse wave (hereinafter referred to as shear wave) has attracted attention, and clinical use for chronic liver disease and cancer has been promoted. In this technique, shear waves are generated inside the tissue to be measured, and elasticity is evaluated from the propagation velocity. Methods for generating shear waves are broadly divided into mechanical methods and radiation pressure methods. The mechanical system is a system that generates a shear wave by applying a vibration of about 1 kHz to the body surface using a vibrator or the like, and requires a driving device as a vibration source. On the other hand, in the radiation pressure method, acoustic radiation pressure is applied to the living body using focused ultrasound that concentrates the ultrasonic waves locally in the tissue, and shear waves are generated using tissue displacement that occurs instantaneously. Each method is a technique for calculating the propagation speed of the generated shear wave from the measurement result of the tissue displacement by ultrasonic waves and evaluating the tissue properties.
Patent Document 1 discloses a technique for evaluating elasticity using acoustic radiation pressure. The technique described in this document uses focused ultrasound to generate a radiation force in the tissue and propagate a shear wave in the tissue. A plurality of measurement points for performing ultrasonic transmission / reception are provided in the propagation direction, and a temporal change in tissue displacement is measured. The arrival time of the shear wave at each measurement point is measured using the displacement measurement result, and the velocity and elasticity evaluation values of the propagation wavefront are calculated.

Non-Patent Document 1 discloses an evaluation method of tissue properties using frequency dispersion (phase velocity) of shear wave velocity. A tangential gradient at a specific frequency is used as a diagnostic index for liver steatosis with respect to the phase velocity measured by ultrasound.

Special table 2010-526626

K. R. Nightingale, et al., IEEE trans. Ultrason. Ferroelectr. Freq. Control, 62, 1, (2015) pp.165

Gastrointestinal system tissues and muscle tissues including the liver are fattened as tissue characteristics due to lack of exercise and aging. Fattening is regarded as a risk factor for chronic diseases and severe diseases, and mid- to long-term observation from the health checkup stage will be necessary in the future.

In particular, nonalcoholic fatty liver (NAFL) among fatty livers can be divided into simple fatty liver with good prognosis and progressive nonalcoholic steatohepatitis (NASH). Fatty liver is improved by lifestyle, but NASH causes irreversible changes in liver cells, and some percent progress to cirrhosis and further to liver cancer. Therefore, NASH and simple fatty liver are discriminated, and NASH is actively treated. Discrimination between simple fatty liver and NASH is currently performed by biopsy in which a part of the tissue is taken out and examined, such as by inserting a needle into the liver.

However, a biopsy has a heavy burden on the subject, and is unnecessary when the subject has simple fatty liver. Therefore, if it is possible to discriminate between non-invasive simple fatty liver and NASH using an ultrasound imaging apparatus and perform a biopsy only when the possibility of NASH is high and confirm the diagnosis, the burden on the subject is reduced. The benefits can be reduced.

When the evaluation value of the velocity and elasticity of the propagation wavefront obtained by the technique of Patent Document 1 and the tangential gradient at a specific frequency of the phase velocity of the shear wave obtained by the technique of Non-Patent Document 1 is used as the evaluation value, simple fatty liver And NASH are often close to each other or overlap in value, and it is difficult to accurately distinguish between simple fatty liver and NASH.

Against this background, an object of the present invention is to provide an ultrasonic imaging apparatus that can accurately evaluate the tissue properties of a living body.

According to the present invention, a transmission / reception control unit that transmits an ultrasonic wave toward an inspection target in which a wave is propagating and receives an ultrasonic wave from the inspection target, and a reception signal An ultrasonic imaging apparatus is provided that includes a property evaluation unit that evaluates tissue properties of a test object. The property evaluation unit includes a velocity calculation unit that calculates the velocity of the wave propagating through the inspection object based on the received signal, and an index calculation unit that calculates an index value indicating the tissue property of the inspection object using the velocity. The index calculation unit uses a predetermined physical property value of the first tissue and a physical property value of the second tissue to obtain a predetermined ratio between the physical property value of the first tissue and the physical property value of the second tissue. The ratio of the physical property value of the first tissue and the physical property value of the second tissue corresponding to the velocity calculated by the velocity calculation unit is calculated as the wave propagation velocity corresponding to the post-addition physical property value added in (1). The calculated ratio is set as an index value indicating the tissue property of the inspection target.

According to the present invention, it is possible to provide an ultrasonic imaging apparatus that can accurately evaluate the tissue properties of a living body.

1 is a block diagram of a configuration example of an ultrasonic imaging apparatus according to a first embodiment. (A)-(c) is explanatory drawing which shows the approximate model in case the test object is a liver. 3 is a flowchart illustrating an operation of the ultrasonic imaging apparatus according to the first embodiment. (A), (b) is explanatory drawing which shows the ultrasonic wave radiated | emitted to a test object from a probe. (A)-(d) is explanatory drawing which shows the procedure of the phase velocity calculation by a velocity calculation part. It is a flowchart which shows operation | movement of an parameter | index calculation part. (A), (b) is explanatory drawing which shows the example of a display screen of a display part. (A) is a graph which shows the parameter | index (sigma) calculated for every frequency band in 2nd Embodiment, (b) is a graph which shows the concept which calculates parameter | index (sigma) for every phase velocity and a frequency band. It is a block diagram which shows the structure of the database of 3rd Embodiment. In the third embodiment, the concept of calculating the physical property value J _a ^* and the physical property value J _b ^* from the phase velocities of the first and second tissues (adipose tissue and liver tissue) and obtaining the index σ to be examined is shown. It is explanatory drawing. In the fourth embodiment, a concept is shown in which a physical property value J _a ^* and a physical property value J _b ^* are calculated from the phase velocities of the first and second tissues (severe fatty liver and normal liver) to obtain an index σ to be examined. It is explanatory drawing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, any method for exciting and propagating a wave in the inspection object may be used as long as it is a method for applying vibration to the inspection object, such as an acoustic radiation pressure or a mechanical device such as a vibration device. In addition to a simple excitation method, excitation by a subject to be examined such as a heartbeat is also included. Further, in the present embodiment, the description of the tissue properties of the living tissue will be described with respect to fat formation, but the essence of the present invention is to calculate an index that accurately represents the tissue properties, and the target tissue properties are fat. It is not limited to the conversion. For example, in addition to the hardening of tissue accompanying fibrosis, even in the case of targeting a cyst or a tumor tissue having a complicated tissue structure, the index of the present invention can be used as information for property determination in principle.

FIG. 1 is a block diagram showing a configuration example of the ultrasonic imaging apparatus according to the embodiment. The ultrasonic imaging apparatus (ultrasonic transmission / reception apparatus) of the present embodiment transmits an ultrasonic wave toward the inspection object 100 in which the wave is propagating and receives the ultrasonic wave from the inspection object 100. A transmission / reception control unit 11 that receives a signal and a property evaluation unit 14 that evaluates the tissue property of the test object 100 are provided. The property evaluation unit 14 evaluates the tissue property of the inspection target 100 using the received signal received by the transmission / reception control unit 11.

The property evaluation unit 14 calculates a velocity of a wave propagating through the inspection object 100 based on the received signal, and an index that calculates an index value indicating the tissue property of the inspection object 100 using the calculated velocity. And a calculation unit 14b. The index calculation unit 14a uses the physical property value of the first tissue and the physical property value of the second tissue, which are obtained in advance, to obtain the physical property value of the first tissue and the physical property value of the second tissue as a predetermined value. Add by the ratio and get the physical property value after addition. The physical property value of the first tissue and the physical property of the second tissue so that the wave propagation speed corresponding to the physical property value after addition corresponds to (for example, substantially the same) the speed calculated by the speed calculation unit 14a. Determine the ratio of addition to the value. The obtained ratio is set as an index value indicating the tissue properties of the test object 100.

The physical property value is preferably a complex number including viscosity and elasticity information. In particular, it is desirable to use a complex compliance defined as the reciprocal of the complex elastic modulus as a physical property value in numerical calculation considering apparatus mounting.

The inventors approximate the tissue of the inspection target 100 as a typical mixed tissue of the first tissue and the second tissue, and use the mixing ratio as an index indicating the tissue properties. FIGS. 2A, 2B, and 2C show approximate models when the inspection object 100 is a liver. When the test object 100 is the liver, the first tissue is the adipose tissue 100b, and the second tissue is the tissue that realizes the function of the test object, that is, the liver tissue 100a (FIG. 2A). The liver tissue of the subject 100 can be approximated to be a mixed tissue of adipose tissue 100b and liver tissue 100a (FIG. 2 (b)).

At this time, the inventors use a complex physical property value (J ^* ) including information on viscosity η and elasticity E as the physical property values of the first and second tissues, as shown in FIG. The physical property value J ^* of the mixed tissue of the first and second tissues is expressed by a linear sum obtained by weighting the physical property value J _a ^* of the first tissue and the physical property value J _b ^* of the second tissue with a ratio σ. I found out. More specifically, the product of the physical property value (J ^* ) of the mixed structure and the stress S is calculated by the composite coupled model as shown in the following formulas (1-1) and (1-2). It is expressed as the sum of products of _n ^* and stress S. Here, n represents the organization number.

By expanding the formulas (1-1) and (1-2), the physical property value J ^* becomes the physical property value J _a ^* of the first tissue and the physical property value of the second tissue as shown in the following formula (2). A linear sum obtained by weighting J _b ^* by the ratio σ is derived.

We have physical properties J _{a *} represented by the formula ^(2), J _b ^* and a ratio Physical properties of the linear sum of sigma J ^* is well with change by the physical property values J ^* of properties of actual biological tissue I found that it corresponds. Therefore, by determining the mixing ratio σ of the mixed tissue model so as to realize the speed obtained from the received signal, the ratio (σ) of the first tissue of the mixed tissue can be obtained. Σ can be used as an index indicating the degree. According to the inventors' research, there is a clear difference in the value of σ between simple fatty liver and NASH, and it is possible to accurately distinguish between simple fatty liver and NASH.

In particular, when compliance is used as J ^* , simple fatty liver and NASH can be distinguished with high accuracy from the difference in the value of σ.

Note that the first tissue and the second tissue are not limited to the fat tissue and the tissue that realizes the function of the test object 100, and the case where the site of the test object 100 is normal as the first tissue. Using the tissue, the second tissue can be modeled as a tissue when the test object 100 suffers from a disease. For example, normal liver tissue may be used as the first tissue, and severe fatty liver tissue may be used as the second tissue.

The following is a more detailed explanation.

<< First Embodiment >>
The ultrasonic imaging apparatus according to the first embodiment will be described in detail with reference to FIG.

FIG. 1 shows an outline of the overall configuration of the ultrasonic imaging apparatus according to the first embodiment of FIG. The ultrasonic imaging apparatus includes a probe 10 and an apparatus main body 20. A display unit 15 is connected to the apparatus main body 20. In the apparatus main body 20, a transmission / reception control unit 11 and a signal processing unit 12 are arranged. The transmission / reception control unit 11 generates a predetermined point in the inspection object 100 from the transmission beamformer 21 that generates a transmission signal to be transferred to each transducer constituting the probe 10 and the output of each transducer of the probe 10. And a reception beamformer 22 for generating a reception signal for.

The signal processing unit 12 includes an image configuration unit 13 that generates an image of the inspection target 100 using the reception signal output from the reception beamformer 22, and a property evaluation unit 14 that evaluates the tissue property of the inspection target 100. Yes. A storage unit 16 storing a database is connected to the signal processing unit 12.

Further, the transmission / reception control unit 11 and the signal processing unit 12 are connected to a control unit 17 that controls the operation.

The functions of the control unit 17, the property evaluation unit 14, and the image configuration unit 13 can be realized by software, or part or all of the functions can be realized by hardware. When implemented by software, the control unit 17, the property evaluation unit 14, and the image configuration unit 13 are configured by a CPU (Central Processing Unit) and a memory in which a program is stored in advance. When the CPU reads and executes the program, the functions of the control unit 17, the property evaluation unit 14, and the image configuration unit 13, which will be described later, are realized. Further, when realized by hardware, a custom IC such as ASIC (Application Specific Integrated Circuit) or a programmable IC such as FPGA (Field-Programmable Gate Array) is used. The circuit design may be performed so as to realize at least the operations of the image forming unit 14 and the image forming unit 13.

Hereinafter, the operation of each part will be described in detail. Here, a case where it is executed by software will be described as an example.

The control unit 17 is read and executed by a CPU containing a program stored in advance in a built-in memory. Thereby, each part is controlled like the flowchart which shows operation | movement of the ultrasonic imaging device shown in FIG.

First, the control unit 17 transmits the first ultrasonic wave from the vibrator 10 to excite the radiation pressure in the inspection object 100 and generate a shear wave (step 101). Specifically, the control unit 17 causes the transmission beam former 21 to generate a transmission signal for irradiating a predetermined position with the first ultrasonic wave that generates the acoustic radiation pressure. The transmission signal generated by the transmission beamformer 21 is transferred to each transducer constituting the probe 10, and the probe 10 has a predetermined acoustic intensity and converges to a focal point having a predetermined depth. One ultrasonic wave 23 is transmitted in a predetermined transmission direction (step 101).

4 (a) and 4 (b) show ultrasonic waves radiated from the probe 10 to the inspection object 100. FIG. The first ultrasonic wave 23 is irradiated to a predetermined position and direction of the region of interest (ROI) 100a of the inspection object 100, and a wave (longitudinal wave and shear wave) is generated in the inspection object 100 by the acoustic radiation pressure of the first ultrasonic wave 23. ) Occurs. The wave propagates radially starting from the position irradiated with the first ultrasonic wave 23. 4A and 4B illustrate a case where a wavefront propagating in the right direction is measured. Hereinafter, the generated shear wave will be described as an example.

The control unit 17 transmits the second ultrasonic wave from the vibrator 10 and measures the displacement of the tissue (step 102). Specifically, in order to measure the displacement of the tissue due to the generated shear wave, the control unit 17 transmits one or more second ultrasonic waves from the probe 10 to a predetermined position at a predetermined timing. The beamformer 21 is caused to generate a transmission signal. As a result, as shown in FIG. 4A, a plurality of second ultrasonic waves 24 are irradiated at a predetermined timing at a predetermined interval in the direction in which the shear wave generated by the first ultrasonic wave 23 propagates. The ultrasonic wave reflected from the inspection object 100 at the location irradiated with the second ultrasonic wave 24 is received by the transducer of the probe 10. The control unit 17 operates the reception beam former 22 to perform reception beam forming on the signal output from the probe, and for each point on one reception scanning line centering on the irradiation position of the second ultrasonic wave 24. Get the received signal. This is repeated over time. The image constructing unit 13 constructs an image to be inspected from the received signal. Based on the obtained image, the velocity calculation unit 14a of the property evaluation unit 14 detects a temporal change in displacement of each point in the predetermined propagation direction of the shear wave in the inspection object 100 (step 102).

On the other hand, in the example of FIG. 4B, one second ultrasonic wave 24 is irradiated over a predetermined range in the propagation direction of the shear wave generated by the first ultrasonic wave 23. The ultrasonic wave reflected from the inspection object 100 at the location irradiated with the second ultrasonic wave 24 is received by the transducer of the probe 10. The control unit 17 operates the reception beam former 22 to perform reception beam forming from the signal output from the probe 10, and each point on the plurality of reception scanning lines centering on the irradiation position of the second ultrasonic wave 24. Get the received signal for. By repeating this over time, the velocity calculation unit 14a detects the displacement of the inspection object 100 due to the propagation of the shear wave at a plurality of propagation positions starting from the irradiation position of the first ultrasonic wave 23.

The transmission / reception pattern of the second ultrasonic wave 24 in FIG. 4A is excellent in sensitivity, but the time resolution is reduced because the second ultrasonic wave 24 needs to be transmitted many times. On the other hand, the transmission / reception pattern of FIG. 4B has a high time resolution because a reception signal can be obtained for a plurality of reception scanning lines with one second ultrasonic wave 24, but the irradiation with the second ultrasonic wave 24 is performed. Because the range is wide, the sensitivity cannot be so high. Any of the transmission / reception patterns shown in FIGS. 4A and 4B may be used according to the region of the inspection object 100 and the required time resolution.

The control unit 17 instructs the speed calculation unit 14a to calculate the shear wave speed (here, phase speed as an example) (steps 103 to 105). The processing of the speed calculation unit 14a will be described with reference to FIG. FIG. 5 is an explanatory diagram showing a procedure of phase velocity calculation by the velocity calculator 14a. As shown in FIG. 5A, the image of the inspection object 100 is configured by the image construction unit 13 in the above step 102, and the velocity calculation unit 14 a is in a plurality of propagation positions starting from the irradiation position of the first ultrasonic wave 23. The time change of the displacement of the inspection object 100 due to the propagation of the shear wave is detected. The velocity calculation unit 14a plots the detected displacement on a map having two axes of the distance in time and propagation direction (propagation position) x, and generates a map (displacement distribution) (FIG. 5B). The velocity calculation unit 14a performs two-dimensional Fourier transform on the generated map to obtain an intensity spectrum distribution having the time frequency f (Hz) and the spatial frequency k (m ⁻¹ ) in FIG. 5C as two axes (step 103). ). The peak position shown in the intensity spectrum distribution of FIG. 5C is detected (step 104). From the relationship between the temporal frequency f at the peak position and the spatial frequency k, the phase velocity V is calculated by V = f / k. Thereby, the frequency dependence of the phase velocity as shown in FIG. 5D is calculated (step 105).

Next, the control unit 17 operates the index calculation unit 14 b of the property evaluation unit 14. This will be described with reference to the flowchart of FIG. The phase velocity V (ω) of the predetermined frequency band ω is received for the phase velocity calculated by the velocity calculation unit 14a (step 201). The index calculation unit 14b reads the physical property value J _a ^* of the liver tissue as the first tissue and the physical property value J _b ^* of the fatty tissue as the second tissue from the database stored in the storage unit 16 in advance. (Step 210). Then, the index calculation unit 14b uses the above formula (2) to determine a predetermined ratio σ between the physical property value J _a ^* of the liver tissue that is the first tissue and the physical property value J _b ^* of the fat tissue that is the second tissue. The physical property value J ^* of the mixed tissue mixed in (1) is calculated (step 211).

Next, the index calculation unit 14b calculates a phase velocity V (ω) corresponding to the physical property value J ^* of the mixed tissue based on the calculated physical property value J ^{* of} the mixed tissue based on the equation (3) (step 212). . Note that ρ is the density of the inspection object 100 and is a constant determined in advance.

　指標算出部１４ｂは、ステップ２１２で算出した位相速度Ｖ（ω）とステップ２０１で受け取った速度算出部１４ａが算出した位相速度をＶ（ω）とを比較し、その差が所定値の範囲内である等、両者が対応しているかどうかを判定し、両者が対応していなければステップ２１１に戻って、比率σの値を所定量だけ変化させてステップ２１１～２１３を繰り返す。ステップ２１３において、対応する位相速度Ｖ（ω）が得られている場合には、その時の比率σを組織性状を表す指標として決定する（ステップ２１４）。

The index calculation unit 14b compares the phase velocity V (ω) calculated in step 212 with the phase velocity calculated by the velocity calculation unit 14a received in step 201 and V (ω), and the difference is within a predetermined value range. For example, it is determined whether or not the two correspond to each other. If the two do not correspond, the process returns to step 211, the value of the ratio σ is changed by a predetermined amount, and steps 211 to 213 are repeated. If the corresponding phase velocity V (ω) is obtained in step 213, the ratio σ at that time is determined as an index representing the tissue properties (step 214).

The index σ is the ratio of the adipose tissue in the test object 100, and shows different values for simple fatty liver and NASH. FIGS. 7A and 7B are explanatory diagrams illustrating display screen examples of the display unit 15. 7A, the property evaluation unit 14 displays the index σ calculated by the index calculation unit 14b together with the image of the ROI 100a of the inspection target 100 generated by the image configuration unit 13 as a numerical value. You may display on 15 display areas 15a. Further, as shown in the screen example of FIG. 7B, the display unit 15 superimposes an image obtained by converting the index σ into a color shade or a change in color tone on the image of the inspection target 100 generated by the image configuration unit 13. May be displayed. In this case, the user can easily grasp the value of the index σ and the severity level of the organization by displaying the intensity level of the organization indicated by the index range in combination with a lightness bar, a color bar 15b, etc. Can do. For example, as shown in FIGS. 7A and 7B, a lightness bar and a color bar 15b are displayed which indicate the severity in three levels of severe, middle, and normal.

Also, by comparing the index σ with a predetermined index range, it is also possible to display by replacing the severity of the organization indicated by the index range. For example, the color bar 15b shown in FIGS. 7A and 7B is displayed by replacing it with colors and shades representing the three levels of tissue severity.

Further, as shown in FIG. 7A, the ROI 100a can be set only to a part of the inspection object 100. As shown in FIG. 7B, the ROI 100a may be set two-dimensionally, the entire inspection object 100 may be colored according to the numerical value of the index, and displayed on the display unit 15 as a two-dimensional map.

The physical property values J _a ^* and J _b ^* of the first tissue and the second tissue stored in advance in the database of the storage unit 16 are, for example, adipose tissue provided from a subject different from the test object 100 It may be a physical property value (complex compliance) measured for liver tissue or a value obtained by calculation.

According to the first embodiment, an index σ of fatification such as fatty liver is obtained based on the phase velocity. It is extremely difficult to measure only one physical property such as elastic modulus and viscosity of a biological tissue having a complicated composition. In the present embodiment, the physical property index including the complexity of the composition is stored in advance, the tendency of the numerical value to be inspected is determined based on this numerical value, and used as a diagnostic index reflecting the tissue properties. High accuracy and high reproducibility are realized. Thereby, treatment judgment based on objective information, lifestyle guidance, and postoperative progress judgment are possible. This technique is also effective for evaluation of fibrosis other than fat and tumor properties, and the biological tissue to be applied is not particularly limited.

In the flow of FIG. 6, the physical property value J ^* of the mixed tissue of the first and second tissues is obtained in step 211, and the phase velocity V (ω) corresponding to the physical property value J ^* is calculated in step 212. The index σ is obtained by comparing the calculated phase velocity with the phase velocity calculated from the received signal (step 201). However, the present embodiment is not limited to this procedure. From the phase speed calculated from the received signal (step 201), calculates a physical property value J ^* using the equation (3), the calculated property values J ^* compared with mixed structure of physical values J ^* obtained in step 211 The value of the index σ may be changed so that the two correspond (for example, the difference falls within a predetermined range).

In this embodiment, complex numbers including viscosity and elasticity information are used as physical property values. However, the present invention is not limited to this, and physical quantities such as ultrasonic velocity in the inspection target are used instead of physical property values. Also good.

<< Second Embodiment >>
An ultrasonic imaging apparatus according to the second embodiment will be described. FIG. 8A is a graph showing the index σ calculated for each frequency band in the second embodiment, and FIG. 8B shows the concept of calculating the index σ for each phase velocity and frequency band. It is a graph.

In the first embodiment, the phase velocity of one frequency band is obtained for the inspection target 100 and the index σ is calculated. In the second embodiment, the frequency dependence of the calculated phase velocity as shown in FIG. For the characteristics, as shown in FIG. 8B, a plurality of frequency bands F1 to F4 are set, and indices σ _F1 to σ _F4 are obtained for each frequency band. The operation for obtaining the index σ in each of the frequency bands F1 to F4 is the same as the flow in FIG. 6 of the first embodiment.

As a result, since the indices σ _F1 to σ _F4 are obtained in the frequency bands F1 to F4 as shown in FIG. 8A, gradient values and average values of the indices σ _F1 to σ _F4 can be calculated. Therefore, it becomes possible to evaluate tissue fatification and the like using the gradient value and the average value. For example, tissue viscosity has a characteristic that it appears strongly in a high frequency region and tissue elasticity strongly appears in a low frequency region. Therefore, by calculating an index for each frequency band, higher accuracy can be realized as a tissue property determination index.

That is, when the user's interest is particularly viscous (eg, fatty liver or cyst), the diagnostic index can be calculated by selectively using the high-frequency band index σ according to the user's instruction or the like. For example, a form in which the overall tissue characteristics are determined in a wide band and more detailed tissue characteristics are determined in a narrow band is also effective by diagnosis.

Other configurations and operations are the same as those in the first embodiment, and thus description thereof is omitted.

<< Third Embodiment >>
An ultrasonic imaging apparatus according to the third embodiment will be described.

In the first embodiment, the physical property value J _a ^* of the first tissue and the physical property value J _b ^* of the second tissue are stored in advance in the database of the storage unit 16, and they are stored in step 210 of the flow of FIG. In the third embodiment, the phase velocities of the first and second tissues are stored in the database as shown in the block diagram of the database structure in FIG. Examples of the phase velocity of the first tissue include the phase velocity of the hepatocyte main tissue and the phase velocity of normal liver. Further, examples of the phase velocity of the second tissue include the phase velocity of the fat-based tissue and the phase velocity of the abnormal liver.

In the third embodiment, in Step 210, the phase velocities of the first and second tissues are read from the database, and the physical property value J _a ^* and the physical property value corresponding to the respective phase velocities are obtained using Equation (3). J _b ^* is calculated. The operation of the other steps and the device configuration are the same as in the first embodiment. FIG. 10 shows the physical property value J _a ^* and the physical property value J _b ^* calculated from the phase velocities of the first and second tissues (adipose tissue and liver tissue) in the third embodiment, and the index σ of the test object 100 is calculated. It is explanatory drawing which shows the concept which calculates | requires. As shown in this conceptual diagram, a physical property value J _a ^* indicating low viscosity and a physical property value J _b ^* indicating high viscosity are calculated from the phase velocities of the first and second tissues (adipose tissue, liver tissue), The index σ can be obtained by calculating the physical property value J ^* indicating the intermediate viscosity of the test liver that is the test object 100.

Since the phase velocity can be measured without removing the tissue from the subject, the phase velocity actually measured with another subject can be stored in the database. Therefore, since the average value of the phase velocities actually measured for a large number of subjects can be used as the physical property value, the reliability of the database can be improved.

<< Fourth Embodiment >>
An ultrasonic imaging apparatus according to the fourth embodiment will be described.

In the first embodiment, a fat tissue is used as the first tissue, and a tissue (for example, liver tissue) that realizes the function of the examination target is used as the second tissue. However, a severely diseased tissue is used as the first tissue. A normal tissue (for example, normal liver) may be used as the second tissue (for example, severe fatty liver). In this case, the phase velocities of the first and second tissues (severe fatty liver and normal liver) are stored in advance in the database of the storage unit 16. FIG. 11 shows that the physical property value J _a ^* and the physical property value J _b ^* are calculated from the phase velocities of the first and second tissues (severe fatty liver, normal liver) in the fourth embodiment, and the index σ of the test object 100 is calculated. It is explanatory drawing which shows the concept which calculates | requires. As shown in this conceptual diagram, the index calculation unit 14b has a physical property value J _a ^* indicating low viscosity and a physical property value J _b indicating high viscosity based on the phase velocity of severe fatty liver, as in the third embodiment. By calculating ^* , a physical property value J ^* indicating the intermediate viscosity of the test liver which is a mixture of high viscosity and low viscosity can be calculated, and the index σ of the test object 100 can be obtained.

Since the phase velocity can be measured without removing the tissue from the subject, the phase velocity measured for a serious disease tissue (for example, severe fatty liver) and a normal tissue (for example, normal liver) is stored in a database. I can leave. Other configurations and operations are the same as those of the third embodiment.

As in the third embodiment, the fourth embodiment can use the phase velocities actually measured for a large number of subjects as the physical property values, so that the reliability of the database can be improved.

DESCRIPTION OF SYMBOLS 10 ... Probe, 11 ... Transmission / reception control part, 12 ... Signal processing part, 13 ... Image structure part, 14 ... Property evaluation part, 15 ... Display part, 16 ... Memory | storage part in which the database was stored, 17 ... Control part, 21 ... Transmission beamformer, 22 ... Reception beamformer, 100 ... Inspection object

Claims (14)

A transmission / reception control unit that transmits an ultrasonic wave toward an inspection target in which a wave propagates and receives an ultrasonic wave from the inspection target, and the reception signal, and the reception signal, the inspection It has a property evaluation section that evaluates the target tissue properties,
The property evaluation unit is a velocity calculation unit that calculates a velocity of the wave propagating through the inspection object based on the received signal, and an index that calculates a value of an index indicating the tissue property of the inspection object using the velocity A calculation unit,
The index calculation unit uses the physical property value of the first tissue and the physical property value of the second tissue determined in advance to determine the physical property value of the first tissue and the physical property value of the second tissue. The wave propagation speed corresponding to the added physical property value added at the ratio of the first physical property value of the first tissue and the physical property value of the second tissue corresponding to the speed calculated by the speed calculation unit A ratio is calculated, and the ratio is set as an index value indicating the tissue property of the inspection target.
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 1,
The physical property value is a complex number including viscosity and elasticity information.
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 2,
The physical property value is compliance.
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 1,
The velocity calculation unit calculates the velocity for each of one or more frequency bands of the wave,
The ultrasonic imaging apparatus, wherein the index calculation unit calculates a value of the index for each frequency band. The ultrasonic imaging apparatus according to claim 1,
The index calculation unit obtains a tissue property corresponding to the calculated ratio value based on a relationship between one or more predetermined tissue properties and a range of ratio values corresponding to the tissue property; Display the obtained tissue properties on the display device.
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 1,
The first tissue is adipose tissue;
The second organization is an organization that realizes the function of the inspection target.
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 1,
The first tissue is a tissue in a case where the site to be examined is normal,
The second tissue is a tissue when the test subject suffers from a disease.
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 1,
The wave is a longitudinal wave or a shear wave;
The velocity is a phase velocity or a group velocity having frequency dependency.
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 1,
The velocity calculation unit generates a map representing displacement at a plurality of times for each of a plurality of positions in the propagation direction of the wave to be inspected from the received signal, and performs two-dimensional Fourier transform on the map , Find the relationship between the time frequency and the spatial frequency, and calculate the phase velocity from the relationship,
An ultrasonic imaging apparatus. A transmission / reception control unit that transmits an ultrasonic wave toward the inspection target in which the wave is propagating and receives a reception signal obtained by receiving the ultrasonic wave from the inspection target;
The velocity of the wave propagating through the inspection object is calculated based on the received signal, and based on the physical property value of the first tissue and the physical property value of the second tissue obtained in advance and the calculated velocity. A signal processing unit that calculates an index for evaluating the tissue property of the inspection target;
An ultrasonic imaging apparatus comprising: The ultrasonic imaging apparatus according to claim 10,
The signal processing unit
Based on the physical property value of the first tissue and the physical property value of the second tissue, and the calculated speed, the ratio of the first tissue and the second tissue constituting the examination object is calculated. And using the calculated ratio as the index,
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 11,
The signal processing unit
The velocity of the wave corresponding to the added physical property value obtained by adding the physical property value of the first tissue and the physical property value of the second tissue by the ratio corresponds to the velocity calculated based on the received signal. Calculating the ratio,
An ultrasonic imaging apparatus. The ultrasonic imaging apparatus according to claim 12,
The physical property value is a complex number including viscosity and elasticity information,
The first tissue is adipose tissue;
The second organization is an organization that realizes the function of the inspection target,
The wave is a longitudinal wave or a shear wave;
The velocity is a phase velocity or a group velocity having frequency dependency.
An ultrasonic imaging apparatus. Transmitting an ultrasonic wave toward the inspection object through which the wave is propagating, receiving an ultrasonic wave from the inspection object, and obtaining a reception signal;
Calculating the velocity of the wave propagating through the inspection object based on the received signal;
Addition in which the physical property value of the first tissue and the physical property value of the second tissue are added at a predetermined ratio using the physical property value of the first tissue and the physical property value of the second tissue which are obtained in advance. The ratio of the physical property value of the first tissue and the physical property value of the second tissue, wherein the wave propagation velocity corresponding to the post physical property value corresponds to the calculated wave velocity, calculates the ratio. And a step of setting an index value indicating the composition property of the test object,
A method for processing an ultrasonic reception signal.

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