JP2002209895A - Ultrasonic imaging method and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic imaging method, or the like, which has high probability of generating a sub-harmonic component in ultrasonic wave transmission so as to detect the sub-harmonic component included in an ultrasonic echo at a speed being in nearly real-time and to obtain an image which is excellent in spatial resolution. SOLUTION: The method is provided with a step (a) for transmitting ultrasonic wave which continues for >=10 cycles to a subject, a step (b) for transmitting ultrasonic wave which continues for >=4 to <10 cycles to the subject after a prescribed time elapses after the step (a), a step (c) for receiving the ultrasonic echo generated by the reflection of the ultrasonic wave which is transmitted in the step (b) from the subject and obtaining a detection signal, and a step (d) for extracting the sub-harmonic component of the ultrasonic echo based on the detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an ultrasonic imaging method and an ultrasonic imaging apparatus, and more particularly, to a sub-harmonic echo using a micro bubble contrast agent. The present invention relates to an ultrasonic imaging method and an ultrasonic imaging device for detecting intensity.

[0002]

2. Description of the Related Art In recent years, ultrasonic diagnosis has remarkably developed in the diagnosis of the chest and abdomen because of its characteristic that blood flow information can be obtained. In particular, since an ultrasonic imaging technique using a contrast agent has been developed, more accurate blood flow information has been obtained. In such ultrasonic imaging, a microbubble contrast agent in which a large number of microbubbles having a diameter of 1 to several μm are mixed in a liquid is used mainly by injecting it into a vein. The microbubbles are formed by encapsulating a gas harmless to the living body (air, fluorocarbon, etc.) in a shell made of a substance harmless to the living body (lecithin, etc.).

[0003] Japanese Patent Application Publication (JP-A-9-164)
No. 138 discloses that an ultrasonic contrast agent for microbubbles is injected into a blood flow, an ultrasonic pulse for breaking microbubbles in a tissue is transmitted, and how much tissue is disturbed during a certain time interval from the destruction of the microbubbles. An ultrasonic diagnostic image processing method for measuring whether or not microbubbles are reperfused therein by ultrasonic waves is disclosed.

[0004] Also in the ultrasonic imaging technique, the use of Doppler signals and harmonic signals has advanced, and blood flow information in more tissues can be obtained. In particular, blood flow dynamics have been more accurately evaluated in combination with ultrasound imaging.

Japanese Patent Application Laid-Open No. H11-178824 discloses a transmitting step in which a modulated ultrasonic sequence is transmitted into the body, and a phase difference is generated in an ultrasonic echo obtained as a response, and a response is made to the transmitting sequence. A pulse inverted Doppler ultrasound diagnostic image processing method is described, comprising the steps of receiving a set of ultrasound echo signals and analyzing the set to separate phase shift information of linear and non-linear signal components. However, in the detection of such a Doppler signal, it is not possible to detect only microbubbles in a blood vessel because a strong signal from a tissue with a large motion such as a myocardium or a harmonic signal generated from the tissue itself is mixed. .

[0006] Therefore, by irradiating an ultrasonic wave having a plurality of continuous waves, an image is generated based on a subharmonic (subharmonic) echo generated only from microbubbles in a blood vessel, so-called subharmonic imaging. Has begun to be considered. Since the subharmonic component is generated only by the chaotic oscillation and bifurcation of the microbubbles, it is considered that the subharmonic imaging can provide a higher contrast contrast than the harmonic (harmonic) imaging.

US Pat. No. 5,706,819 discloses a method of injecting a harmonic contrast agent into a subject and combining the echo signals received while alternately inverting the polarity of the transmission pulse, thereby obtaining harmonics of the transmission signal. An ultrasonic diagnostic image processing method that suppresses components and removes scattering to detect the influence of a harmonic contrast agent is disclosed. However, according to this method, since the sum of the harmonic and the subharmonics is detected, only the subharmonics cannot be detected.

Japanese Patent Application Laid-Open No. 2000-5167 discloses that an ultrasonic wave having a plurality of continuous waves is transmitted.
Ultrasonic waves are transmitted before and after at least one wave having an instantaneous sound pressure that does not destroy microballoons (microbubbles), and a subharmonic echo is reliably generated. An ultrasonic transmission method is described. However, according to this method, the microballoon is destroyed, so that the microballoon injected into the subject cannot be continuously observed in real time.

Further, in recent years, many studies have been made on the generation mechanism of subharmonics, and it is known that the intensity of subharmonics is increased by irradiating ultrasonic waves having a plurality of continuous waves. (Nico de Jong, 1st International Contrast-Enhanced Ultrasound Kyoto Symposium S1-1, October 23, 1999).
However, in ultrasonic imaging, since the spatial resolution is determined by the length of the transmitted continuous wave, the problem is that the spatial resolution of the obtained ultrasonic image is reduced when long-term continuous ultrasonic waves are used. Occurs.

[0010]

SUMMARY OF THE INVENTION In view of the foregoing, an object of the present invention is to provide a method for transmitting a sub-harmonic component contained in an ultrasonic echo in real time with a high probability of generating a sub-harmonic component in transmission of an ultrasonic wave. An object of the present invention is to provide an ultrasonic imaging method and an ultrasonic imaging apparatus that can detect an image at a close speed and obtain an image with excellent spatial resolution.

[0011]

In order to solve the above-mentioned problems, an ultrasonic imaging method according to the present invention comprises the steps of: (a) transmitting an ultrasonic wave continuous for at least 10 cycles to a subject; and (a). After a predetermined period of time, 4 cycles or more and 10
A step (b) of transmitting an ultrasonic wave continuous for less than a period to the subject, and a step (c) of receiving an ultrasonic echo generated by reflecting the ultrasonic wave transmitted in the step (b) to the subject and obtaining a detection signal (c) ) And extracting a subharmonic component of the ultrasonic echo based on the detection signal (d).

An ultrasonic imaging apparatus according to the present invention comprises an ultrasonic probe in which a plurality of ultrasonic transducers are arranged, and an ultrasonic probe which transmits an ultrasonic wave for ten or more cycles to a subject after a predetermined period has elapsed. Transmitting means for supplying a drive signal to the ultrasonic probe so as to transmit ultrasonic waves continuous for at least 4 cycles to less than 10 cycles to the subject; and ultrasonic waves continuous for 4 cycles to less than 10 cycles are reflected by the subject. The apparatus includes a receiving unit that receives a echo with an ultrasonic probe to obtain a detection signal, and a signal processing unit that extracts a subharmonic component of the ultrasonic echo based on the detection signal.

According to the above configuration, by transmitting an ultrasonic wave continuous for at least 10 cycles to the subject, the chaotic vibration or bifurcation of the microbubbles is activated to increase the probability of generating a subharmonic component. 1 or more for 4 cycles
By transmitting an ultrasonic wave that is continuous for less than 0 cycles to the subject and detecting a subharmonic component included in the ultrasonic echo at a speed close to real time, an image with excellent spatial resolution can be obtained.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of the ultrasonic imaging apparatus according to the first embodiment of the present invention.

As shown in FIG. 1, the ultrasonic imaging apparatus includes an ultrasonic probe 20 including an ultrasonic transducer array constituted by a plurality of ultrasonic transducers.
Having. The ultrasonic probe 20 is used in contact with the subject 10 by an operator. A microbubble contrast agent is injected into the subject 10 in advance, and the microbubble 10
0 is included.

The ultrasonic probe 20 is connected to a transmitting / receiving unit 30. In the transmission / reception unit 30, the transmission timing generation circuit 322 periodically generates a transmission timing signal and supplies it to the transmission beamformer 321. The transmission beamformer 321 generates a plurality of drive signals (transmission beamforming signals) for driving the plurality of ultrasonic transducers of the ultrasonic probe 20 with a time difference based on the transmission timing signal, and the transmission / reception switching circuit 3
The signal is supplied to the ultrasonic probe 20 via the line 11. The waveforms of these drive signals are selected so that the sound pressure waveform of the transmitted ultrasonic wave becomes a waveform described later. The plurality of ultrasound transducers constituting the transmission aperture of the ultrasound probe 20 transmit a plurality of ultrasound waves having a phase difference corresponding to a time difference between these drive signals toward the subject 10.
An ultrasonic beam is formed by the wavefront synthesis of the plurality of ultrasonic waves.

On the other hand, the ultrasonic probe 20
It receives the ultrasonic wave (echo) reflected from, converts it into an electric signal, and outputs it to the reception beamformer 331 via the transmission / reception switching circuit 311. As described above, a plurality of echo signals received by a plurality of ultrasonic transducers constituting a receiving aperture of the ultrasonic probe 20 are input to the receiving beam former 331. The receiving beamformer 331 adjusts the phase by adding a time difference to a plurality of reception echoes, and then adds them to form an echo detection signal along the sound ray, that is, performs beamforming of the reception wave. It has become. The received sound beam is also scanned by the receiving beamformer 331 in accordance with the transmission.

The ultrasonic beam transmitted by the ultrasonic probe 20 is set so as to generate a continuous wave which forms the sound pressure waveform shown in FIG. 2 in the convergence region. As shown in FIG. 2, first, in order to activate chaotic oscillation or branching phenomenon of microbubbles, a first burst wave continuous for m (m is an integer of 10 or more) periods (wavelengths) is generated. Send. Then, in order to obtain an ultrasonic image, a second burst wave that is continuous for n (n is an integer of 4 or more and less than 10) cycles (wavelengths) is transmitted. In the first burst wave, the number m of continuous cycles is preferably set to 10 or more and 50,000 or less, more preferably 1 to 50,000.
0 to 100. In the second burst wave, the number n of continuous cycles is preferably 4 or more and 6 or less.

Here, the reason why the length of the first burst wave is set to 10 periods or more is that such a period is required to activate the microbubbles. Further, the length of the first burst wave is set to 50,000 cycles or less in consideration of the balance between the efficiency of microbubble activation and the time required for ultrasonic scanning. On the other hand, the second
The length of the burst wave is set to four periods or more in order to easily generate subharmonics. Also, the second
The reason why the length of the burst wave is less than 10 periods is that if an ultrasonic wave that is continuous for a long time is used, the spatial resolution of the obtained ultrasonic image is reduced.

As shown in FIG. 2, after the first burst wave for activating the microbubbles is transmitted in the first period t ₁ and after the transmission of the ultrasonic wave is stopped in the second period t ₂ . , A second burst wave for obtaining an ultrasonic image is transmitted in a _third period t3. Here, the second period t ₂ is set to 1 msec or more and 1 sec or less, preferably 10 msec, in consideration of the time until the ultrasonic wave transmitted in the first period t ₁ is reflected by the subject and returns.
msec or more and within 100 msec.

The irradiation intensity of the first and second burst waves is set to a sound pressure that does not destroy the contrast agent (microbubble) instantaneously. Specifically, the sound pressure of the first and second burst waves is 10 kPa or more and 200 kPa or less,
It is desirable that the pressure be 30 kPa or more and 100 kPa or less. With this configuration, the microbubbles are not instantaneously destroyed, so that the microbubbles injected into the subject can be continuously observed in real time.

The ultrasonic wave having such a waveform is incident on the tissue of the subject as shown in FIG. 3, and the ultrasonic wave (echo) reflected from the subject 10 is incident on the ultrasonic probe. As shown in FIG. 3, the subject 10 includes tissues a, b, and c. For example, tissues a and c are cells and tissue b
Is a blood vessel. Inside the tissue b, microbubbles 10
0 has been injected. The sound ray 202 of the transmission wave is a tissue a,
While passing through b and c, a part of the transmission wave is reflected on the two walls of the tissue a and the tissue b and the tissue c. Further, another part of the transmission wave is reflected by the microbubbles 100 existing inside the tissue b to generate a subharmonic component. Here, the image information at different positions in the depth direction can be selectively obtained by specifying the time from transmitting the transmission wave to receiving the reflected wave.

The transmission of the ultrasonic beam is repeatedly performed at predetermined time intervals by the transmission timing signal generated by the transmission timing generation circuit 322 shown in FIG. The direction of the ultrasonic beam is sequentially changed by the transmission beam former 321. Thus, the inside of the subject 10 is scanned by the sound ray formed by the ultrasonic beam. That is, the direction of the sound ray changes sequentially inside the subject 10. The transmission / reception unit 30 having such a configuration performs, for example, scanning as shown in FIG. In FIG. 4, an ultrasonic beam (sound ray 202) extending in the z direction from the radiation point 200 scans the fan-shaped two-dimensional area 206 in the θ direction, and performs a so-called sector scan.

On the other hand, when the transmitting and receiving apertures are formed using a part of the ultrasonic transducer array, the apertures are sequentially moved along the ultrasonic transducer array, for example, as shown in FIG. Such scanning can be performed. In FIG. 5, a sound ray 202 extending in the z direction from a radiation point 200 is represented by a locus 2 on a straight line.
By translating along the line 04, the rectangular two-dimensional area 206 is scanned in the x direction, so-called linear scan is performed.

Also, the ultrasonic transducer array is
In the case of a so-called convex array formed along an arc extending in the ultrasonic wave transmission direction, for example, scanning as shown in FIG. 6 can be performed by sound ray scanning similar to linear scanning. In FIG. 6, the radiation point 200 of the sound ray 202 is moved along an arc-shaped trajectory 204 centered on a divergence point 208 to form a fan-shaped two-dimensional area 206.
Are scanned in the θ direction to perform a so-called convex scan.

Here, the first burst wave and the second burst wave may be alternately irradiated for each sound ray. Further, after scanning one two-dimensional region with the first burst wave, the same two-dimensional region may be scanned with the second burst wave to obtain an ultrasonic image. Alternatively, the scanning may be appropriately performed with the first burst wave while obtaining an ultrasonic image by scanning the inside of a plurality of two-dimensional regions with the second burst wave. In any case, the first burst wave and the second burst wave are alternately irradiated, and during that time,
1 msec or more and within 1 sec, preferably 10 msec
It is desirable to provide a non-transmission period within 100 msec or more.

Referring again to FIG. 1, the receiving beamformer 331 is connected to the waveform processing section 400 of the signal processing section 40. The waveform processing unit 400 separates the fundamental wave component and the sub-harmonic component from the input echo reception signal for each sound ray, outputs the fundamental wave component to the fundamental wave processing unit 401, and outputs the sub-harmonic component to the sub-harmonic processing unit. Output to 402. The fundamental wave processing unit 401 and the sub-harmonic processing unit 402 process the input fundamental wave component and the sub-harmonic component, respectively, and
Output to 3. The image processing unit 403 generates a fundamental B-mode image obtained by performing luminance modulation based on the intensity of the fundamental wave based on the fundamental wave component, and performs luminance modulation based on the intensity of the subharmonic component based on the subharmonic component. A subharmonic B image is generated.

Here, the waveform processing section 400 extracts a subharmonic component from the detection signal input from the reception beamformer 331 using a bandpass filter.
The frequency of the sub-harmonic component to be extracted is preferably set to 1/2 or 3/2 of the frequency of the fundamental wave, and particularly preferably 3/2 of the frequency of the fundamental wave.

The fundamental wave processing unit 401 detects a fundamental wave echo (a received wave having the same frequency as the fundamental frequency of the transmitted wave) obtained from the received wave, and performs logarithmic amplification and envelope detection on the detected echo. A signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A-scope signal is obtained. Further, the fundamental wave processing unit 401 sets the instantaneous amplitude of each of the A scope signals at each time point as a respective luminance value,
Form B-mode image data.

[0030] Here, the one-dimensional image data generated on the basis of the fundamental wave echo, the luminance signal X ₀ in FIG. 7 (a) 9
Shown as 10. The luminance signal X ₀ 910 includes the scattering 911 of the tissue a, the scattering 912 and 913 of the two walls of the tissue b, the scattering 914 of the tissue c, and the scattering 915 of the microbubbles injected into the tissue b shown in FIG. Has been extracted.

Subharmonic processing section 402 (FIG. 1)
Obtains a signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A-scope signal by logarithmic amplification and envelope detection of the subharmonic echo obtained from the received wave. Also, the sub-harmonic processing unit 402
The B-mode image data is formed by using the instantaneous amplitude of the A scope signal at each point in time as the respective luminance value.

Here, one-dimensional image data generated based on the subharmonic echo is shown as a luminance signal X _SUB 920 in FIG. 7B. The sub-harmonic signal 925 of the microbubble injected into the tissue b shown in FIG. 3 is extracted from the luminance signal X _SUB 920.

Referring again to FIG. 1, the fundamental wave processing unit 40
1 and the sub-harmonic processing unit 402
03 is connected. The image processing unit 403 generates a plurality of B-mode images based on the B-mode image data input from the fundamental wave processing unit 401 and the sub-harmonic processing unit 402, respectively. About this behavior,
This will be described in detail below.

The B-mode image data based on the fundamental wave echo and the sub-harmonic echo input for each sound ray from the fundamental wave processing unit 401 and the sub-harmonic processing unit 402 are:
These are stored in the sound ray data memory in the image processing unit 403, respectively. Each sound ray data space is formed in the sound ray data memory.

The sound ray data space in the sound ray data memory is as follows.
The scan conversion of the digital scan converter (DSC) 404 converts sound ray data space data into physical space data. The image data converted by the DSC 404 is stored in the image memory 405. The image memory 405 stores image data of a physical space. The data in the sound ray data memory and the image memory 405 are respectively subjected to predetermined data processing by an image processor.

The display unit 50 is connected to the image memory 405. The display unit 50 displays an image based on the image data of the physical space stored in the image memory 405. The display unit 50 is preferably capable of displaying a color image.

The transmitting / receiving section 30 and the signal processing section 40 are connected to a control section 60. The control section 60 supplies a control signal to each of these sections to control the operation thereof. Further, the control unit 60 is configured to receive various notification signals from these units. Ultrasonic imaging is performed under the control of the control unit 60. Further, the control unit 6
“0” includes an operation unit. The operation unit is operated by an operator, and inputs desired commands and information to the control unit. The operation unit includes, for example, an operation panel including a keyboard and other operation tools.

The fundamental wave processing unit 401 to the image processing unit 4
Each part of 03 may be constituted by an analog circuit or a digital circuit. Or you may comprise with software and CPU. In that case, the control unit 60 including the CPU processes the detection signal based on the ultrasonic processing program recorded on the recording medium 70. As the recording medium 70, a floppy (registered trademark) disk, hard disk, MO, MT, RAM, CDROM, or D
VDROM and the like correspond.

Next, the operation of the ultrasonic imaging apparatus according to this embodiment will be described. The operator operates the ultrasonic probe 20.
Is brought into contact with a desired portion of the subject 10 and the operation unit is operated to perform imaging. Under the control of the control unit 60, transmission and reception of ultrasonic waves are performed while sequentially scanning sound rays, and imaging is performed. For example, while sequentially scanning sound rays by a sector scan as shown in FIG. 4, an ultrasonic beam is transmitted for each sound ray, its echo is received, and a B-mode image is formed based on the echo received wave. Generate. Of course, a linear scan or a convex scan as shown in FIG. 5 or 6 may be performed.

At this time, the transmitted ultrasonic beam has, for example, the sound pressure waveform shown in FIG. 2, activates the microbubbles 100, and reliably generates a subharmonic echo. B-mode image data is formed based on the echo reception waves of each sound ray. As the B-mode image data, one based on the fundamental wave echo and one based on the subharmonic echo are formed, and are stored in the sound ray data memory in the image processing unit 403.

The sound ray data in the sound ray data memory is stored in a DSC
Scan conversion is performed in 404, and the data is written to the image memory 405. The operator operates the operation unit to display these B-mode images on the display unit 50. For example, as shown in FIG. 8, a display 110 of the display unit displays a composite image of a tomographic image 111 of the tissue obtained based on the fundamental wave echo and an image 112 obtained based on the subharmonic echo of the microbubbles. Let it.

Next, a second embodiment of the present invention will be described. In the present embodiment, in order to extract the sub-harmonic component from the detection signal of the ultrasonic echo, instead of using the band-pass filter in the first embodiment, the detection signal and the delayed detection signal Find the difference between

A method of extracting a subharmonic signal according to the present embodiment will be described with reference to FIG. Echo microbubbles are adapted to the waveform R ₁ shown in FIG. The waveform R _1, and delayed by the fundamental period τ of the transmission wave, creating a wave R _2. Next, obtains the difference between the waveform R ₁ and waveform R _2, to obtain a waveform R _SUB subharmonic signal. The echo of the transmitted ultrasonic wave is formed by the sum of a fundamental wave, a harmonic, and a subharmonic signal. here,
The fundamental wave and the harmonics are waveforms having the fundamental period τ of the transmission wave as a repetition unit, and thus are removed by the above-described signal processing. As a result, only the sub-harmonic signal remains.

FIG. 10 shows a part of the configuration of the waveform processing section in the present embodiment. In FIG. 10, the delay circuit 1
The detection signal is delayed by the transmission fundamental period τ. Difference circuit 2
Extracts and outputs a subharmonic signal by calculating a difference between the detection signal and the delayed detection signal.

Next, a third embodiment of the present invention will be described. In the present embodiment, instead of using the delay circuit in the second embodiment to extract a sub-harmonic component from a detection signal of an ultrasonic echo, a plurality of points included in an ultrasonic probe and an ultrasonic probe are used. The two detection signals having a phase difference are obtained based on the path difference between the ultrasonic transducer and the ultrasonic transducer, and the difference between them is obtained.

As shown in FIG. 11, the ultrasonic probe 20
The plurality of ultrasonic transducers 21 included in
It is desirable to arrange them with a step in the receiving direction. The reception beamformer 331 selects at least two ultrasonic transducers from among the plurality of ultrasonic transducers 21 to obtain two detection signals whose phases are shifted by a time corresponding to one cycle of the transmission ultrasonic wave. . For example, to obtain a detection signals S ₁ from the ultrasonic transducer T _1, to obtain a detection signal S ₂ from the ultrasonic transducer T _2. Here, one wavelength of the transmitted ultrasonic wave is λ, a distance from the reflection point of the subject 10 to the ultrasonic transducer T ₁ is L ₁ , and a distance from the reflection point of the subject 10 to the ultrasonic transducer T ₂ is L ₂ . Then, there is a relationship of L ₂ −L ₁ = λ.

Further, the reception beamformer 331 gives a time difference to the plurality of reception echoes to adjust the phases, and then adds them to form an echo detection signal along the sound ray, that is, to receive the reception echoes. May be performed. The receiving beamformer 331 detects the detection signal S ₁ ,
Processes the S _2, and outputs transmission ultrasound of the first phase is shifted by the time corresponding to one period of the detection signal R ₁ and the second detection signal R ₂ finally. The waveform processing unit 400 obtains the difference between the first detection signal R ₁ and the second detection signal R ₂ , thereby obtaining the waveform R _{SUB of the} subharmonic signal as shown in FIG. 8, as in the second embodiment. Get.

In these embodiments, an example has been described in which B-mode imaging is performed using sub-harmonic echoes. However, ultrasonic imaging is not limited to B-mode imaging, but uses Doppler shift of sub-harmonic echoes. Alternatively, a dynamic image may be taken.

[0049]

As described above, according to the present invention,
By transmitting an ultrasonic wave that is continuous for 10 cycles or more to the subject, the chaotic vibration or bifurcation of the contrast agent (microbubble or the like) is activated to increase the probability of generating a subharmonic component. By transmitting an ultrasonic wave shorter than the period to the subject and detecting a subharmonic component included in the ultrasonic echo at a speed close to real time, an image with excellent spatial resolution can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an ultrasonic imaging apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a sound pressure waveform of an ultrasonic wave transmitted by the ultrasonic imaging apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a state where ultrasonic waves transmitted by the ultrasonic imaging apparatus according to the first embodiment of the present invention are incident on a subject.

FIG. 4 is a diagram illustrating an example of sound ray scanning in the ultrasonic imaging apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating another example of sound ray scanning in the ultrasonic imaging apparatus according to the first embodiment of the present invention.

FIG. 6 is a diagram showing still another example of sound ray scanning in the ultrasonic imaging apparatus according to the first embodiment of the present invention.

FIG. 7 is a diagram showing one-dimensional image data generated as a luminance signal in the method for processing a signal of an ultrasonic diagnostic image according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of a display image in the ultrasonic imaging apparatus according to the first embodiment of the present invention.

FIG. 9 is a waveform chart for explaining processing of a detection signal according to the second embodiment of the present invention.

FIG. 10 is a block diagram illustrating a part of a configuration of a waveform processing unit according to a second embodiment of the present invention.

FIG. 11 is a block diagram showing an ultrasonic probe and its peripheral circuits according to a third embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 delay circuit 2 difference circuit 10 subject 20 ultrasonic probe 30 transmitting / receiving unit 40 signal processing unit 50 display unit 60 control unit 70 recording medium 100 microbubble 110 display of display unit 111 tomographic image of tissue obtained based on fundamental wave echo 112 Image obtained based on sub-harmonic echo of microbubble 200 Radiation point 202 Sound ray 204 Trace 206 Two-dimensional area 208 Divergence point 311 Transmission / reception switching circuit 321 Transmission beamformer 322 Transmission timing generation circuit 331 Receiving beamformer 400 Waveform processor 401 fundamental wave processing unit 402 subharmonic processor 403 image processing unit 404 a digital scan converter (DSC) 405 image memory 910 the luminance signal X ₀ 911 2 one wall of the scattered 912 and 913 tissue b tissue a Scattering 914 tissue c scattered 915 scattered 920 luminance signal X _SUB 925 tissue b injected into the microbubbles of the sub-harmonic signal of the microbubbles injected into the tissue b of

Claims (7)

[Claims] 1. A step (a) of transmitting an ultrasonic wave continuous for at least 10 cycles to a subject, and an ultrasonic wave continuous for at least 4 cycles and less than 10 cycles after a predetermined period has elapsed after the step (a). (B) transmitting the ultrasonic wave transmitted in the step (b) to the subject to receive an ultrasonic echo generated by the ultrasonic wave reflected in the subject, and (c) obtaining a detection signal, based on the detection signal. Extracting a sub-harmonic component of the ultrasonic echo (d). 2. The method according to claim 1, wherein the predetermined period has passed from 1 msec to 1
2. The ultrasonic imaging method according to claim 1, wherein the time is within sec. 3. The sound pressure of the ultrasonic waves transmitted in the steps (a) and (b) is 10 kPa or more and 200 kPa or more.
The ultrasonic imaging method according to claim 1 or 2, wherein the pressure is equal to or less than kPa. 4. The ultrasonic imaging method according to claim 1, further comprising, before step (a), injecting a microbubble contrast agent into the subject. 5. An ultrasonic probe in which a plurality of ultrasonic transducers are arranged, and an ultrasonic probe which is continuous for at least 4 cycles and less than 10 cycles after a predetermined period has elapsed after transmitting ultrasonic waves for 10 or more cycles to the subject. A transmitting unit that supplies a drive signal to the ultrasonic probe so as to transmit a sound wave to the subject; and an echo generated when the continuous ultrasonic wave is reflected by the subject for at least 4 cycles and less than 10 cycles. An ultrasonic imaging apparatus, comprising: a receiving unit that obtains a detection signal by using the detection signal; and a signal processing unit that extracts a subharmonic component of an ultrasonic echo based on the detection signal. 6. The ultrasonic imaging apparatus according to claim 5, wherein the predetermined period has elapsed from 1 msec to 1 sec. 7. The ultrasonic imaging apparatus according to claim 5, wherein a sound pressure of the ultrasonic wave transmitted by the ultrasonic probe is 10 kPa or more and 200 kPa or less.