JP5186155B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an image forming technique using a contrast agent.

  Microbubbles (or nanobubbles) mean fine bubbles injected into a liquid or the like. Since these microbubbles have various excellent characteristics, they are used in many fields. For example, as an application to the medical field, microbubbles are suitable reflectors for ultrasonic waves, and are therefore used as contrast agents when acquiring ultrasonic images. As a method for forming an ultrasound image using a contrast agent, for example, a phase inversion method is known (see Patent Document 1).

  On the other hand, techniques for labeling proteins (antigens, antibodies, etc.) and nucleic acids (DNA, RNA, etc.) on the surface of microbubbles are attracting attention. For example, a molecule is modified on the surface of the microbubble, the microbubble is captured by the target cell in the living tissue, and the amount of the target cell in the tissue or the distribution of the target cell in the tissue is determined via the microbubble. This is a technique for imaging and diagnosis.

  When microbubbles are captured by target cells and imaged, for example, in order to observe only captured microbubbles, microbubbles that move within the tissue without being captured by target cells and captured by target cells It is desirable to be able to distinguish the microbubbles that have stopped. In response to such a request, for example, Patent Document 2 emphasizes information obtained from a contrast agent that moves relatively slowly (stationary microbubbles) against a contrast agent that moves fast (moving microbubbles). The technology to display is described.

  Regarding the distinction between the stationary microbubbles and the moving microbubbles, Patent Literature 2 roughly describes three methods. The first method is based on the Doppler principle, and this method complicates signal processing, for example. The second method uses the fact that the spectrum of the generated signal accompanying the non-linear vibration of the stationary microbubble shifts to the fundamental wave band. In the third method, since the vibration is limited and the signal intensity is weakened in the stationary microbubble, signals from the same position are detected at different times and changes in the intensity are used. However, the second and third methods have problems in detection sensitivity and accuracy.

  Incidentally, although it is not a technique for discriminating between stationary microbubbles and moving microbubbles, Patent Documents 3 and 4 disclose techniques for detecting and imaging signals from the same position at different times.

JP 2003-102726 A JP 2007-90075 A JP 2002-153462 A JP 2004-613 A

  Under such circumstances, the inventor of the present application has repeatedly studied on an imaging technique using ultrasonic waves using a contrast agent. In particular, research has been conducted on a technique for discriminating between a signal component of a subject tissue and a signal component of a contrast agent, and further discriminating between a stationary contrast agent and a moving contrast agent.

  The present invention has been made in the course of its research, and its purpose is to appropriately distinguish the signal component of the subject tissue and the signal component of the contrast agent. Another object of the present invention is to appropriately distinguish between a contrast agent that remains and a contrast agent that moves.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred embodiment of the present invention includes a probe for transmitting and receiving ultrasonic waves to a subject to which a contrast agent is administered, an ultrasonic beam by controlling the probe. And a plurality of reception signals corresponding to the plurality of ultrasonic beams in the scanning space are formed by processing a signal obtained from the probe. Based on a reception unit, an identification unit for identifying a stationary component and a movement component of a contrast agent included in each reception signal for each ultrasonic beam, and a plurality of reception signals corresponding to a plurality of ultrasonic beams in the scanning space An image forming unit for forming a display image in which the stationary component and the moving component of the contrast agent are identified, and the probe includes a signal component of the subject tissue and a signal component of the contrast agent included in each received signal. home, Wherein the signal components of Kagezai to transmit the ultrasonic waves dominant become low sound pressure.

  In a preferred aspect, the contrast agent includes a contrast bubble, and the identification unit identifies a stationary component and a moving component of the bubble included in a harmonic component extracted from each received signal. And

  In a preferred aspect, the transmission unit controls a probe based on a transmission pulse having a waveform of a chirp signal, and each received signal is subjected to pulse compression processing corresponding to the chirp signal. .

  In a preferred aspect, a center frequency of the chirp signal is set according to a resonance frequency of a bubble included in the contrast agent.

  In a preferred aspect, the signal strength of each reception signal subjected to the pulse compression processing is adjusted based on a pulse length of a transmission pulse having the waveform of the chirp signal. Thereby, for example, even in a low sound pressure transmission waveform, the intensity of the received signal can be increased by increasing the pulse length of the transmission pulse.

  In a preferred aspect, the probe has a bass sound in which the second harmonic component of the bubble is dominant among the second harmonic component of the subject tissue and the second harmonic component of the bubble included in the harmonic component. A pressure ultrasonic wave is transmitted.

  In a preferred aspect, the probe transmits an ultrasonic wave having a low sound pressure with a mechanical index (MI) of 0.1 or less.

  In a preferred aspect, the transmission unit performs a plurality of transmissions for each beam direction of a plurality of ultrasonic beams, and the reception unit forms a plurality of reception signals corresponding to the plurality of transmissions for each beam direction. Then, for each beam direction, the identification unit extracts the stationary component by adding a plurality of reception signals corresponding to the beam direction, and subtracts the plurality of reception signals corresponding to the beam direction. Thus, the moving component is extracted.

  In a preferred aspect, the image forming unit forms a display image representing a temporal change in the amount of the stationary component.

  According to the present invention, the signal component of the subject tissue and the signal component of the contrast agent can be appropriately identified. Furthermore, according to a preferred aspect of the present invention, it is possible to appropriately distinguish between a contrast agent that remains and a contrast agent that moves.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a functional block diagram showing the overall configuration thereof. The ultrasonic diagnostic apparatus shown in FIG. 1 is suitable for forming an image using a contrast agent including a contrast bubble (microbubbles such as microbubbles and nanobubbles). The contrast agent is administered to a diagnostic site such as a blood vessel or a tumor in a living body. A diagnosis is performed by the ultrasonic diagnostic apparatus shown in FIG. 1 after a certain period of time has elapsed from the administration of the contrast agent to, for example, the accumulation and uptake of bubbles in the living body.

  The signal generator 10 is controlled by a control unit (not shown) or the like, generates a drive signal for forming a transmission pulse, and outputs it to the transmission circuit 12. In this embodiment, a transmission pulse having a chirp signal waveform is used. For example, the signal generator 10 outputs a transmission pulse having a chirp signal waveform with a center frequency of 3.5 MHz, a start frequency of 3 MHz, an end frequency of 4 MHz, and a pulse length of 20 μsec.

  The transmission circuit 12 controls a plurality of vibration elements (not shown) included in the probe 14 based on the transmission pulse output from the signal generator 10 to form a transmission beam, and electronically scans the formed transmission beam. Thus, a plurality of transmission beams are formed over the entire scanning region. In the present embodiment, transmission is performed twice for each beam direction of a plurality of transmission beams. That is, after the first transmission is performed based on the transmission pulse of the chirp signal waveform for one beam direction and the reception signal is acquired, the transmission signal is continuously transmitted based on the transmission pulse of the same waveform for the same beam direction. A second transmission is performed to obtain a received signal. Then, after two transmissions are performed for one beam direction, the transmission is performed twice for the next beam direction by changing the beam direction. In this way, two transmissions are executed for each beam direction over the entire scanning region.

  By the way, the repetition frequency in transmission, that is, the time interval between the first transmission and the second transmission in the same beam direction, should be set so as not to cause aliasing due to an echo signal from a bubble moving in the bloodstream. Is desirable. For example, if the center frequency of the chirp signal forming the transmission pulse is 3.5 MHz, the second harmonic component described later is 7 MHz. Therefore, for example, assuming that the blood flow velocity in the abdomen is about 60 cm / sec as the bubble velocity, the repetition does not occur when the repetition interval is set to 250 μsec and the repetition frequency (PRF) is set to 4 KHz.

  The probe 14 transmits / receives ultrasonic waves to / from the living body to which the contrast agent is administered. The probe 14 includes a plurality of vibration elements that transmit and receive ultrasonic waves. The plurality of vibration elements are transmission-controlled by the transmission circuit 12, and the transmission beam is scanned. Further, the plurality of vibration elements receive the ultrasonic waves reflected from the living body, and a signal obtained thereby is output to the receiving circuit 16.

  The reception circuit 16 forms a reception beam signal corresponding to each of the plurality of transmission beams in the scanning region by performing phasing addition processing on the signals obtained from the plurality of vibration elements of the probe 14. In the present embodiment, since transmission is performed twice for each beam direction of a plurality of transmission beams, the reception circuit 16 performs the first reception beam signal corresponding to the first transmission for each beam direction. A second received beam signal corresponding to the second transmission is formed.

  The low-pass filter 18 extracts a fundamental wave component (fundamental frequency component) from the received beam signal formed in the receiving circuit 16. The fundamental wave component contains reflected echoes from the tissue in the living body more preferentially than those from the bubble. The pulse compression processing unit 20 performs pulse compression processing corresponding to the chirp signal at the time of transmission on the fundamental wave component of the received beam signal extracted by the low pass filter 18. By this pulse compression processing, the received beam signal (fundamental wave component) is converted (compressed) into a sharp pulse signal. Then, the data of the reception beam signal (the fundamental wave component after compression processing) corresponding to each of the plurality of transmission beams in the scanning region is stored in the image memory 22. Since the fundamental wave component contains predominantly reflected echoes from the tissue, the data stored in the image memory 22 corresponds to image data corresponding to the tissue in the living body.

  The high pass filter 24 extracts a second harmonic component (second harmonic component) from the reception beam signal formed in the reception circuit 16. The second harmonic component contains reflected echoes from the bubbles more preferentially than those from the tissue. The pulse compression processing unit 26 performs pulse compression processing corresponding to the chirp signal at the time of transmission on the second harmonic component of the received beam signal extracted by the high pass filter 24. By this pulse compression processing, the received beam signal (second harmonic component) is converted (compressed) into a sharp pulse signal.

  In the present embodiment, transmission is performed twice for each beam direction of a plurality of transmission beams, and for each beam direction, the first received beam signal corresponding to the first transmission and the second transmission are supported. A second received beam signal is formed. Therefore, when pulse compression processing is performed on the first received beam signal in the pulse compression processing unit 26, the converted received beam signal is stored in the memory 28. Next, the pulse compression processing unit 26 applies pulse compression processing to the second received beam signal in the same beam direction as the first time. Then, the first received beam signal for the same beam direction is output from the memory 28, and the second received beam signal for the same beam direction is output from the pulse compression processing unit 26. In this way, a set of the first received beam signal and the second received beam signal is sequentially output from the memory 28 and the pulse compression processing unit 26 for each beam direction over the entire scanning region.

  The moving component extraction unit 30 extracts a bubble moving component included in the received beam signal for each beam direction. The second harmonic component of the received beam signal extracted by the high-pass filter 24 includes a reflected echo from the bubble more preferentially than that from the tissue. That is, in the first received beam signal and the second received beam signal output from the memory 28 and the pulse compression processing unit 26, the reflected echo from the bubble is dominant.

  The moving component extraction unit 30 performs difference processing (subtraction processing) between the first received beam signal and the second received beam signal in the same beam direction. That is, the difference between the signal portions corresponding to the same depth (position) is calculated for the first received beam signal and the second received beam signal. When the bubble is stationary, the signal portion corresponding to the bubble appears at the same depth and at the same intensity in the first received beam signal and the second received beam signal. Therefore, by calculating the difference between the first received beam signal and the second received beam signal, the remaining bubble component is removed. On the other hand, when the bubble is moving, the signal portion corresponding to the bubble is very unlikely to appear at the same depth and with the same intensity in the first received beam signal and the second received beam signal. . Therefore, by calculating the difference between the first received beam signal and the second received beam signal, only the moving bubble component is extracted.

  The moving component extraction unit 30 extracts a moving bubble component for each beam direction and for each depth (position) in each beam direction for a plurality of beam directions over the entire scanning region. The extracted result is stored in the image memory 34 as image data of the moving bubble.

  On the other hand, the stationary component extraction unit 32 extracts a stationary component of bubbles included in the received beam signal for each beam direction. The stationary component extraction unit 32 performs addition processing of the first received beam signal and the second received beam signal in the same beam direction. That is, signal portions corresponding to the same depth (position) are added to the first received beam signal and the second received beam signal. When the bubble is stationary, the signal portion corresponding to the bubble appears at the same depth and at the same intensity in the first received beam signal and the second received beam signal. Therefore, by adding the first received beam signal and the second received beam signal, the signal strength of the component of the bubble to be retained is almost doubled. On the other hand, when the bubble is moving, the signal portion corresponding to the bubble is very unlikely to appear at the same depth and with the same intensity in the first received beam signal and the second received beam signal. . Therefore, even if the first received beam signal and the second received beam signal are added, the signal intensity is not as high as that of the stationary component.

  Accordingly, the stationary component extraction unit 32 extracts the stationary bubble component by regarding the received beam signal in which the stationary bubble component becomes dominant by the addition processing as the stationary bubble received beam signal. Note that the bubble component to be retained may be extracted by extracting only a portion of the received beam signal after the addition processing having a high signal intensity with a threshold or the like. The stationary component extraction unit 32 extracts a stationary bubble component for each beam direction and for each depth (position) in each beam direction with respect to a plurality of beam directions over the entire scanning region. The result extracted in this manner is stored in the image memory 36 as image data of the stationary bubble.

  As described above, the moving component extraction unit 30 and the stationary component extraction unit 32 extract the moving bubble component and the stationary bubble component. That is, the moving component extraction unit 30 has a function corresponding to an MTI filter (inverse Wall filter) that removes signal components from the stationary bubble, while the stationary component extraction unit 32 receives a signal from the moving bubble. A function corresponding to an inverse MTI filter (Wall filter) for removing components is provided.

  However, in the present embodiment, the frequency analysis processing of the received beam signal is not necessarily required. Therefore, in this embodiment, compared with the method of extracting the moving component based on the Doppler principle, the moving bubble component and the stationary bubble component are discriminated by relatively easy signal processing with a relatively simple configuration. can do. In the above description of the present embodiment, an example of two transmissions and receptions for each beam direction has been shown. For example, three or four (or more) transmissions and receptions are performed for each beam direction. By performing this, the accuracy of discrimination (discrimination) between the moving bubble component and the stationary bubble component may be further improved.

  Returning to the description of FIG. 1, the image synthesis unit 38 synthesizes the image data stored in the image memories 22, 34, and 36 to form a display image in which the stationary component and the moving component of the bubble are identified. That is, the image composition unit 38 forms a tissue image (for example, a B-mode image) corresponding to the tissue in the living body based on the image data stored in the image memory 22. Further, the image composition unit 38 forms a moving bubble image based on the image data stored in the image memory 34, and forms a stationary bubble image based on the image data stored in the image memory 36. Then, the image composition unit 38 composes the moving bubble image and the stationary bubble image on the tissue image. At the time of the synthesis, display processing corresponding to each of the moving bubble image and the stationary bubble image is performed. The formed display image (composite image) is displayed on the display unit 40.

  FIG. 2 is a diagram for explaining a display image 50 displayed on the display unit (reference numeral 40 in FIG. 1). The display image 50 in FIG. 2 synthesizes a stationary bubble (a plurality of circled dots) and a moving bubble (a plurality of filled circles) in a B-mode image 52 including a tissue such as a blood vessel. It is a thing. Note that the stationary bubble and the moving bubble may be identified and displayed by a coloring process. For example, a moving bubble is expressed in red, and a stationary bubble is expressed in blue.

  In FIG. 2, the plurality of moving bubbles are bubbles flowing in the blood vessel, for example. On the other hand, the bubble to be retained is a bubble trapped in, for example, a tissue. In the present embodiment, in addition to the display image that identifies the moving bubble and the stationary bubble, a time-change image 56 that represents a temporal change in the amount of the stationary bubble may be formed.

  The time change image 56 shows the time change of the amount of bubbles in the region of interest (ROI) 54 set in the display image 50. The time change image 56 is a graph showing the integrated value of the signal intensity of the bubble on the vertical axis with the horizontal axis as the time axis. From the time change image 56, for example, a time change of the amount of bubbles captured in a specific portion (specific cell) can be observed. Note that the region of interest 54 is desirably set at a desired position to be observed, for example, in accordance with a user (observer) operation.

  The display image 50 and the time-change image 56 in FIG. 2 identify and display, for example, bubbles that remain in the blood vessel or tissue and bubbles that move in the blood vessel. As a result, for example, a low molecular weight ligand for capturing a molecule such as a protein that specifically expresses a lesion is labeled on the surface of a bubble (microbubble), and a protein that is specifically expressed in a lesion is labeled. Bubbles can be accumulated and imaged (molecular imaging).

  Alternatively, the Kupffer cells may be indirectly imaged using bubbles (eg, sonazoids) trapped by phagocytic cells (Kupffer cells) in hepatocytes. For example, by using sonazoid, since cancer cells generated by metastasis do not have Kupffer cells, it is possible to form an image in which only a portion of cancer cells is not displayed (blackened). The image may be used for cancer diagnosis.

  As described above, in the present embodiment, the signal from the bubble and the signal from the tissue are discriminated by utilizing the fact that the reflected echo from the bubble is predominantly included in the second harmonic component. Yes.

  The harmonic signal generated from the tissue is based on the non-linearity of the tissue with respect to the ultrasound. In general, the second harmonic from the tissue is proportional to the square of the sound pressure of the ultrasound. On the other hand, the harmonic signal from the bubble is generated along with the nonlinear vibration of the bubble. When the sound pressure of the ultrasonic wave is reduced, the amount of vibration of the bubble is reduced, so that the second harmonic generated from the bubble is also reduced. However, the degree of reduction of the second harmonic generated from the bubble is smaller than the degree of reduction of the second harmonic generated from the tissue. Therefore, CTR (Contrast to Tissue Ratio), which is the ratio of the second harmonic signal from the bubble and the second harmonic signal from the tissue, can be improved by reducing the ultrasonic transmission sound pressure.

  FIG. 3 is a diagram showing a result of examining improvement in CTR when sound pressure is reduced by simulation. In the simulation, the generation of nonlinear signals during tissue propagation was analyzed by numerical calculation using the KZK equation and the bubble vibration model using the Herring equation. As analysis conditions, a bubble having a diameter of 2 μm, a chirp signal forming a transmission pulse, a signal having a start frequency of 3 MHz, an end frequency of 4 MHz, and a pulse length of 2 μsec was used. Further, two kinds of transmission sound pressures of 300 KPa and 30 KPa, a vibrator diameter of 1.3 cm, and a focus depth of 7 cm were used. Under this condition, the mechanical index (MI value) was MI = 0.42 at a transmission sound pressure of 300 KPa and MI = 0.042 at 30 KPa from the waveform at the focus.

  FIG. 3A shows the second harmonic (after pulse compression processing) from the bubble at MI = 0.32. Similarly, FIG. 3B shows the second harmonic (after pulse compression processing) from the tissue at MI = 0.32. At this time, it was assumed that the reflection coefficient from the tissue had the same amplitude (CTR = 1) as the signal from the bubble. Using this reflection coefficient condition at a high sound pressure, the signal ratio (CTR) from the bubble to the tissue when the sound pressure was changed from 300 KPa to 30 KPa, that is, the MI was changed from 0.32 to 0.042 was calculated.

  FIG. 3C shows a signal waveform from the bubble, and FIG. 3D shows a signal from the tissue. In FIGS. 3C and 3D, the vertical axis is the same scale. At this time, the signal ratio CTR from the bubble to the tissue was 7.76, which was 17.8 dB higher than that in the case of MI = 0.32.

  Thus, although the CTR can be improved by reducing the transmission sound pressure, the signal itself from the bubble is reduced. Under the above analysis conditions, the signal intensity from the bubble was about 20 dB smaller than when MI = 0.32. Therefore, in this embodiment, pulse compression processing is used. In the pulse compression process, the intensity of the signal after the pulse compression process can be enhanced by increasing the pulse length of the transmission pulse. In the simulation, the signal intensity was increased by 3.6 dB by changing the pulse length from 2 μsec to 8 μsec.

  From the above analysis, it can be seen that the signal from the bubble can be extracted efficiently by using the pulse compression process and using a transmission waveform having a low sound pressure of MI = 0.1 or less. By the way, it is said that MI for imaging sonazoid captured by Kupffer cells with an optimum sensitivity is about 0.2 to 0.4. However, even with the sound pressure of ultrasonic waves corresponding to this range of MI, a certain amount of sonazoid disappears. On the other hand, by using a low sound pressure of MI = 0.1 or less, it is possible to minimize the disappearance (rupture) of the sonazoid as much as possible. In addition, it is desirable that the transmission frequency of the ultrasonic wave transmitted to the bubble, for example, the center frequency of the chirp signal in this embodiment is in the range from the same level as the resonance frequency of the bubble.

  FIG. 4 is a diagram showing the acoustic characteristics of the contrast agent, and shows an acoustic characteristics graph obtained by simulation of microbubbles having a diameter of 2.5 μm. In the graph of FIG. 4, the horizontal axis represents the ultrasonic transmission frequency. Further, the “versus-organization signal normalized second harmonic amount” shown on the vertical axis corresponds to the harmonic level. In the graph of FIG. 4, the results are shown for each transmission sound pressure of Pa = 100, 200, 300, 400 (unit KPa).

  In the graph shown in FIG. 4, the resonance frequency is about 2.5 MHz. And, in the range of about 2.5 MHz or less, the attenuation of the harmonic level is relatively small as compared with the case of being larger than about 2.5 MHz. That is, a relatively high harmonic level can be maintained when the ultrasonic transmission frequency is in the range from about the same as or below the bubble resonance frequency.

  The preferred embodiment of the present invention has been described above. Incidentally, in this embodiment, it is desirable that the diameter of the bubble is, for example, 0.2 to 15 μm. Moreover, it is desirable that the particle size distribution of the plurality of bubbles is uniform. For example, it is desirable to remove bubbles of a certain size or larger. In addition, other coded signals may be used instead of the chirp signal. The above-described embodiments are merely examples in all respects, and do not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

1 is a functional block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is a figure for demonstrating the display image displayed on a display part. It is a figure which shows the result of having examined improvement of CTR at the time of making sound pressure small. It is a figure which shows the acoustic characteristic of a contrast agent.

Explanation of symbols

  12 transmitting circuit, 14 probe, 16 receiving circuit, 18 low-pass filter, 24 high-pass filter, 30 moving component extracting unit, 32 stationary component extracting unit, 38 image synthesizing unit.

Claims (9)

A probe that transmits and receives ultrasound to and from a subject to which a contrast medium is administered;
A transmitter that forms a plurality of ultrasonic beams in a scanning space by controlling the probe to scan the ultrasonic beams;
A receiver that forms a plurality of received signals corresponding to a plurality of ultrasonic beams in the scanning space by processing a signal obtained from the probe;
An identification unit for identifying a stationary component and a moving component of a contrast agent included in each reception signal for each ultrasonic beam;
An image forming unit that forms a display image in which a stationary component and a moving component of a contrast agent are identified based on a plurality of reception signals corresponding to a plurality of ultrasonic beams in a scanning space;
Have,
The transmission unit performs transmission a plurality of times for each beam direction of a plurality of ultrasonic beams,
The receiving unit forms a plurality of received signals corresponding to a plurality of transmissions for each beam direction,
For each beam direction, the identification unit extracts the stationary component by adding a plurality of reception signals corresponding to the beam direction, and subtracts the plurality of reception signals corresponding to the beam direction. Extracting the moving component;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The contrast agent contains a contrast bubble,
The identification unit identifies a stationary component and a moving component of a bubble included in a harmonic component extracted from each received signal.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The transmitter controls the probe based on a transmission pulse having a chirp signal waveform,
Each received signal is subjected to a pulse compression process corresponding to the chirp signal.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3.
A center frequency of the chirp signal is set according to a resonance frequency of a bubble included in the contrast agent.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3 or 4,
Based on the pulse length of the transmission pulse having the waveform of the chirp signal, the signal strength of each reception signal subjected to the pulse compression processing is adjusted,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to any one of claims 2 to 5,
The probe is a low sound pressure ultrasonic wave in which the second harmonic component of the bubble is dominant among the second harmonic component of the subject tissue and the second harmonic component of the bubble contained in the harmonic component. To transmit,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 6,
The probe transmits a low sound pressure ultrasonic wave having a mechanical index (MI) of 0.1 or less.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3.
A center frequency of the chirp signal is set to be equal to or lower than a resonance frequency of a bubble contained in the contrast agent;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to any one of claims 1 to 8,
The image forming unit forms a display image representing a temporal change in the amount of the stationary component;
An ultrasonic diagnostic apparatus.

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