JP2002113007A - Ultrasonic wave transmitting/receiving method, and ultrasonic wave transmitter/receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic wave transmitting/receiving method capable of obtaining images with excellent space resolution. SOLUTION: This method is provided with a step of transmitting ultrasonic waves which are continuous for more than two cycles to a subject 10, a step of detecting echo generated by reflection of transmitted ultrasonic waves in a tissue of the subject using an ultrasonic probe 20 including an ultrasonic transducer 21 formed of plural electrodes 22a, 22b, etc., and plural piezoelectric elements 23a, 23b, etc., alternately laminated with each other in the receiving direction, as a step for obtaining basic wave components in thickness resonance in the ultrasonic transducer based on output voltages of at least two electrodes in the plural electrodes, and a step of obtaining image information related to the tissue of the subject based on the basic wave components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an ultrasonic transmitting / receiving method and an ultrasonic transmitting / receiving apparatus, and more particularly to an ultrasonic diagnostic image forming method using ultrasonic waves having a plurality of continuous periods (wavelengths). . Further, the present invention relates to an ultrasonic transmission / reception method for detecting a subharmonic (subharmonic) echo intensity using a microbubble contrast agent.

[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 (such as air and fluorocarbon) in a shell made of a substance harmless to the living body (such as lecithin).

[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 transmission / reception technology, 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. .

In US Pat. No. 5,706,819, the influence of the harmonic contrast agent is received while alternately inverting the polarity (phase), thereby suppressing the harmonic components of the transmission signal and scattering. An ultrasonic diagnostic image processing method for detecting the effect of a harmonic contrast agent by removing the image is disclosed. However, in order to perform such harmonic image processing, it is necessary to transmit a plurality of ultrasonic waves having different polarities (phases), and the measurement takes a long time. There is a problem that the resolution is reduced.

On the other hand, 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 imaging.

Regarding sub-harmonic echo of microbubbles, see P.S. M. Shankar et al. Akou
st. Soc. Am. , 106 (4), 2104 (19
As shown in a paper published in 99), it is known that a continuous ultrasonic wave is generated. In order to perform subharmonic imaging, an ultrasonic wave including a plurality of continuous waves called a burst wave is used. . However, when a plurality of waves that are continuous for a long time, such as a burst wave, are used, one set of waves becomes long, and the spatial resolution of an image also decreases.

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, in order to detect sub-harmonics containing a large number of long wavelength components with respect to a transmission wave, further improvements are desired, including processing of a received signal.

As a method of detecting the subharmonic intensity, a method of performing a fast Fourier transform (FFT) on a received waveform is used. However, since the FFT requires a long calculation time, it is not suitable for real-time image display. There is. In addition, according to the method of extracting the sub-harmonic frequency component by filtering in a circuit, the sub-harmonic frequency component exists at a plurality of frequencies sandwiched between the fundamental wave and the harmonic, so that only the sub-harmonic is extracted. It is difficult.

Incidentally, Japanese Patent Application Laid-Open No. 11-342129 or US Pat. No. 5,980,459 (Jan. 1999)
(Published on Jan. 9), a system for imaging an ultrasonic scatterer, comprising: an ultrasonic transducer array having a plurality of transducer elements;
Pulse generating means for pulsing the selected transducer element, coupled to the pulse generating means, wherein the first beam for the first transmit launch and the second beam for the second transmit launch are the same Transmitting beam forming means for forming these beams so as to be focused on the transmitting focal position;
Forming a first beam summed received signal from a first set of received signals from a selected transducer element forming a receive aperture after a first transmit launch and a second set after a second transmit launch. Receiving beam forming means for forming a second beam-added received signal from the received signals, filtering means for "slow-time" filtering these beam-added received signals, and vector addition for adding the filtered signals The system including the device etc. is published.

In this system, the receive beamforming means applies an appropriate time delay to each amplified echo signal, provides dynamic apodization upon reception, and adds the delayed, apodized signals. To form one summed echo signal that accurately indicates the total ultrasound energy reflected from points located at a particular range (distance) along one ultrasound beam.

[0013]

SUMMARY OF THE INVENTION In view of the foregoing, an object of the present invention is to provide a method for detecting a fundamental component of an echo in each ultrasonic transducer element included in an ultrasonic probe, thereby improving spatial resolution. An object of the present invention is to provide an ultrasonic transmission / reception method and an ultrasonic transmission / reception device capable of obtaining an excellent image. Another object of the present invention is to provide an ultrasonic transducer capable of displaying subharmonic information at a speed close to real time by detecting a subharmonic component of an echo in each ultrasonic transducer element included in the ultrasonic probe. An object of the present invention is to provide a transmission / reception method and an ultrasonic transmission / reception device.

[0014]

In order to solve the above-mentioned problems, an ultrasonic transmitting / receiving method according to a first aspect of the present invention comprises:
Transmitting an ultrasonic wave having a period equal to or longer than a period to the subject; and using an ultrasonic probe including an ultrasonic transducer formed by alternately stacking a plurality of electrodes and a plurality of piezoelectric elements in a receiving direction. Detecting an echo resulting from reflection of the transmitted ultrasonic wave on the tissue, wherein obtaining a fundamental wave component in thickness resonance in the ultrasonic transducer based on output voltages of at least two of the plurality of electrodes. And obtaining image information on the tissue of the subject based on the fundamental wave component.

The ultrasonic transmitting / receiving method according to a second aspect of the present invention includes a step of transmitting an ultrasonic wave that is continuous for at least four cycles to the subject, wherein the plurality of electrodes and the plurality of piezoelectric elements alternate in the receiving direction. Detecting an echo generated by reflection of transmitted ultrasonic waves on the tissue of the subject using an ultrasonic probe including an ultrasonic transducer formed by being laminated on at least two electrodes of the plurality of electrodes. Obtaining a sub-harmonic component in the thickness resonance in the ultrasonic transducer based on the output voltage of the ultrasonic transducer.

An ultrasonic transmitting / receiving apparatus according to a first aspect of the present invention is an ultrasonic probe including an ultrasonic transducer formed by alternately stacking a plurality of electrodes and a plurality of piezoelectric elements in a receiving direction. An ultrasonic probe that transmits an ultrasonic wave that is continuous for at least two cycles to a subject in a predetermined period, and detects an echo generated when the transmitted ultrasonic wave is reflected by a tissue of the subject; and at least one of a plurality of electrodes. There are provided means for obtaining a fundamental wave component in thickness resonance in the ultrasonic transducer based on output voltages of the two electrodes, and means for obtaining image information on tissue of the subject based on the fundamental wave component.

An ultrasonic transmitting and receiving apparatus according to a second aspect of the present invention is an ultrasonic probe including an ultrasonic transducer formed by alternately stacking a plurality of electrodes and a plurality of piezoelectric elements in a receiving direction. An ultrasonic probe that transmits an ultrasonic wave that is continuous for four or more cycles to a subject, detects an echo generated when the transmitted ultrasonic wave is reflected by the tissue of the subject, and obtains a reception signal, and a plurality of electrodes. Means for obtaining a subharmonic component in thickness resonance in the ultrasonic transducer based on output voltages of at least two electrodes in the ultrasonic transducer.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an ultrasonic transmitting and receiving apparatus according to one embodiment of the present invention. As shown in FIG. 1, the ultrasonic transmission / reception device has an ultrasonic probe 20 including a plurality of ultrasonic transducers 21. The ultrasonic probe 20 is used in contact with the subject 10 by an operator. A microbubble contrast medium is injected into the subject 10 in advance, and contains the microbubbles 100.

FIG. 1 shows only two ultrasonic transducers in order to make the structure of the ultrasonic transducer 21 easy to see. In the ultrasonic transducer 21, a plurality of electrodes 22a, 22b,.
And a plurality of piezoelectric elements 23a, 23b,... Are alternately stacked in the receiving direction. As the material of the piezoelectric element,
Lead zirconate piezoelectric ceramic called PZT,
A polymer material (polymer) called PVDF (polyvinylidene fluoride) can be used, but in the present invention, a PVDF polymer having a small bulk modulus is preferable.

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.

The ultrasonic wave is incident on the tissue of the subject as shown in FIG. 2, and the ultrasonic wave (echo) reflected from the subject 10 is incident on the ultrasonic probe. As shown in FIG. 2, the subject 10 includes tissues a, b, and c.
For example, tissues a and c are cells, and tissue b is a blood vessel. Microbubbles 100 are injected into the tissue b. The sound ray 202 of the transmission wave advances through the tissues a, b, and c, and a part of the transmission wave
Are reflected at the two walls, tissue c. Another part of the transmission wave is reflected by the microbubbles 100 existing inside the tissue b to generate a subharmonic component.

On the other hand, in FIG. 1, an ultrasonic probe 20 having a plurality of ultrasonic transducers 21 receives an ultrasonic wave (echo) reflected from the subject 10 and converts the ultrasonic wave into an electric signal to switch between transmission and reception. The signal is output to the receiving beamformer 331 via the circuit 311. This receiving operation will be described in detail below.

The ultrasonic wave reflected by the subject 10 and incident on the ultrasonic transducer 21 is applied to a plurality of electrodes 22 a and 22 included in each ultrasonic transducer 21.
.. and the piezoelectric elements 23a, 23b,. However, it is assumed that the thickness of the electrode is sufficiently smaller than the thickness of the piezoelectric element. The speed of the ultrasonic wave changes under the influence of the bulk modulus and density of the passing object. In each of the ultrasonic transducers 21, when distortion is generated in the piezoelectric element by the received ultrasonic waves, an electric field, that is, a voltage per unit length is generated.

In FIG. 3, if the wavelength of the ultrasonic wave (fundamental wave) in the ultrasonic transducer is λ, and the distance from the end face of the ultrasonic transducer in the direction of travel of the ultrasonic wave is δ, the thickness resonance of the piezoelectric element causes , Δ = nλ /
2 (where n = 0, 1, 2,...) Has the maximum amplitude of the fundamental wave. Therefore, as shown by the solid line in FIG. 3, the fundamental wave is represented by A ₁ cos (2πδ / λ),
Subharmonic wave of 1/2 harmonic of fundamental wave is A ₂ cos
(Πδ / λ). These equations assume that there is no sound pressure attenuation in the ultrasonic transducer.

If the characteristics of the piezoelectric element are ideal,
An electric field proportional to the amount of distortion is generated in the piezoelectric element. Since the voltage generated at the electrode is obtained by integrating the electric field in the piezoelectric element, the fundamental wave is represented by B _{1 as} shown by the broken line in FIG.
sin (2πδ / λ), δ = λ / 4 + nλ / 2
It becomes the maximum in the surface which becomes. Further, the subharmonic wave of a half harmonic of the fundamental wave is represented by B ₂ sin (πδ / λ), and is maximized in a plane where δ = λ / 2 + nλ.
In the present embodiment, a fundamental wave component and a sub-harmonic component (hereinafter simply referred to as a fundamental wave component and a sub-harmonic component) in a thickness resonance in an ultrasonic transducer of an echo obtained by transmitting a transmission ultrasonic wave having a predetermined frequency to a subject. In order to detect a harmonic component, the distance between the electrodes is set to be equal to a quarter wavelength of the fundamental wave in the ultrasonic transducer.

As shown in FIG. 3, when the output potential of the electrode 22a is Va, the output potential of the electrode 22b is Vb, the output potential of the electrode 22c is Vc, and the output potential of the electrode 22d is Vd.
Received signal S ₁ obtained by the voltage between electrodes 22a and 22b, received signal S ₂ obtained by the voltage between electrodes 22b and 22c, and reception obtained by the voltage between electrodes 22c and 22d The signal S ₃ , the received signal S ₁₂ obtained by the voltage between the electrode 22a and the electrode 22b, and the received signal S ₂₃ obtained by the voltage between the electrode 22b and the electrode 22d are expressed as follows. S ₁ = Vb−Va S ₂ = Vc−Vb S ₃ = Vd−Vc S ₁₂ = Vc−Va S ₂₃ = Vd−Vb

The fundamental wave component of each received signal is expressed as follows. S ₁ = B ₁ S ₂ = −B ₁ S ₃ = −B ₁ S ₁₂ = 0 S ₂₃ = −2B ₁ Since there is actually sound pressure attenuation in the ultrasonic transducer, the absolute value of S ₂ Becomes smaller than the absolute value of S ₁ .

The sub-harmonic component of each received signal is expressed as follows. S ₁ = (1 / √2) B ₂ S ₂ = (1-1 / √2) B ₂ S ₃ = − (1-1 / √2) B ₂ S ₁₂ = B ₂ S ₂₃ = 0 The ratio of the sub-harmonic component to the fundamental wave component is S ₁₂ / S ₁ . Note that, in practice, since there is sound pressure attenuation in the ultrasonic transducer, the ratio of the subharmonic component to the fundamental component is 2S ₁₂ / (S ₁ −
S ₂ ).

Thus, the electrodes 22a, 22b,.
By using at least two of the above, the fundamental wave component and the subharmonic component of the echo can be detected with various sensitivities. When detecting the fundamental wave component, the voltage of the fundamental wave component is increased, in view of being able to suppress the subharmonic component, the received signal S ₂₃ obtained from the electrodes 22b and 22d are suitable. Alternatively, the electrodes 22b and 2
The sum (S ₂ + S ₃ ) of the reception signal S ₂ obtained from 2c and the reception signal S ₃ obtained from the electrodes 22c and 22d may be obtained.

On the other hand, when detecting the subharmonic waves, high voltage sub-harmonic components, in terms of being able to suppress the fundamental wave component, the received signal S ₁₂ obtained from the electrodes 22a and 22c are suitable. Alternatively, electrode 2
The sum (S ₁ + S ₂ ) of the reception signal S ₁ obtained from 2a and 22b and the reception signal S ₂ obtained from the electrodes 22b and 22c may be obtained. Further, when the ultrasonic transducer is long, a reception signal obtained from the electrodes 22c and 22g can be used.

These received signals are transmitted to the ultrasonic probe 20
Is input to the receiving beamformer 331. further,
The reception beam former 331 adjusts the phase by adding a time difference to the plurality of reception echoes, and then adds them to form an echo reception signal along the sound ray, that is, performs beam forming of the reception wave. You may do it.

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. 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 a radiation point 200 is divided into a fan-shaped two-dimensional region 2
06 in the θ direction, so-called sector scan is performed.

On the other hand, when the transmitting and receiving apertures are formed by 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.

When only the fundamental wave component contained in the received ultrasonic echo is used, the ultrasonic beam transmitted by the ultrasonic probe forms, for example, a sound pressure waveform shown in FIG. 7 in the convergence region. It is set to produce such a continuous wave. This sound pressure waveform is a continuous wave for k / 2 periods (wavelengths) (k is an integer of 4 or more). Desirably, 4 ≦ k ≦ 10 ⁵ , and the continuous wave includes a wave having two cycles or more and 50,000 cycles or less.

The reason why the period is set to two cycles or more is that a period for stabilizing the transmission oscillator is required.
The reason why the period is set to 50,000 cycles or less is to prevent a wave reflected from the subject and returned from becoming an obstruction. When using 1 MHz ultrasonic waves, 5
A 0000 cycle corresponds to 1/20 second. In addition, the upper limit of the number of periods of the continuous wave is more preferably 10,000 wavelengths or less, and further preferably 1,000 wavelengths or less.

On the other hand, when the sub-harmonic component included in the received ultrasonic echo is also used, the ultrasonic beam transmitted by the ultrasonic probe forms a sound pressure waveform shown in FIG. It is set to generate a continuous wave like this. As shown in FIG. 8, this sound pressure waveform is a continuous wave for n periods (wavelengths) (n is an integer of 4 or more). The subharmonic is a sound wave having a wavelength n / m times the transmission wavelength λ (m is a natural number and n and m are independent), and particularly, m
= 2 sound waves tend to appear strongly.

In the above, preferably, 4 ≦ n ≦ 5 ×
10 ⁴ , and this continuous wave has 5
Waves of less than 0000 cycles are included. Here, the reason why the number of cycles is four or more is to make it easier to generate subharmonics. FIG. 9A shows an example of the waveform of such a transmission wave. FIG. 9B shows an example of an echo waveform of a microbubble generated by the transmission wave.

Next, processing of the received ultrasonic waves will be described.
I do. As shown in FIG.
The output is connected to the waveform processing unit 400 of the signal processing unit 40.
ing. Receiving beamformer 331 and waveform processing unit 40
0, see FIG. 3 and FIG.
It will be explained while referring to the figures. As shown in FIG.
At intervals of 1/4 wavelength of the fundamental wave in the transducer,
The number of electrodes 22a, 22b,... Is provided. This
The output potentials Va, Vb,... Of these electrodes are shown in FIG.
Are supplied to the differential amplifiers 1, 2,... these
Voltage between two electrodes (received signal) by differential amplifier
S₁= Vb-Va, S_Two= Vc-Vb, S_Three= Vd-V
c, S₁₂= Vc-Va, S_{twenty three}= Vd-Vb etc.
For something For example, the reception signal S_{twenty three}The received wave basics
Using the received signal S₁₂The received wave of sub-harmon
It can be used as a nick component. Or arithmetic
Unit 6 for receiving a received wave based on the output signal of the differential amplifier.
Calculation of the fundamental or subharmonic components of
May be. For example, as a fundamental wave component, S_Two+ S_ThreeCalculate
And S as a subharmonic component ₁+ S_TwoAct
It is calculated and output.

Referring again to FIG. 1, the reception beamformer 331 and the waveform processing unit 400 separate the fundamental wave component and the subharmonic component from the input echo reception signal for each sound ray, and convert the fundamental wave component into the fundamental wave. Output to the processing unit 401 and the sub-harmonic component to the sub-harmonic processing unit 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-mode image is generated.

Each unit of the waveform processing unit 400 to the image processing unit 403 shown in FIG. 1 may be constituted by an analog circuit or a digital circuit. Or you may comprise with software and CPU. In that case, C
The control unit 60 including the PU processes the received signal based on the ultrasonic diagnostic image processing program recorded on the recording medium 70. As the recording medium 70, a floppy (registered trademark) disk, hard disk, MO, MT, RAM,
A CD-ROM, a DVD-ROM, or the like corresponds.

Here, 1 is generated based on the fundamental wave component.
The image data of the dimensions, the luminance signal X ₀ 9 in FIG. 11 (a)
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.

One-dimensional image data generated based on the sub-harmonic component is shown as a luminance signal X _SUB 920 in FIG. The sub-harmonic signal 925 of the microbubble injected into the tissue b shown in FIG. 2 is extracted from the luminance signal X _SUB .

In the present embodiment, an example has been described in which B-mode imaging is performed using continuous ultrasonic waves. However, ultrasonic imaging is not limited to B-mode imaging, and uses Doppler shift of subharmonic echo. Alternatively, a dynamic image may be taken.

Referring to FIG. 1 again, image processing in the ultrasonic transmitting / receiving apparatus according to the present embodiment will be described in detail. Fundamental wave processing unit 401 and subharmonic processing unit 4
02 is connected to the image processing unit 403. 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.

The fundamental wave processing unit 401 has a filter for passing a fundamental wave echo, that is, an echo reception signal having the same frequency as the fundamental frequency of the transmission wave, and performs logarithmic amplification and envelope amplification of the fundamental wave echo obtained from the reception wave. By performing line detection, a signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A-scope signal, is obtained. Generate image data. In this way, the fundamental wave processing unit 401 generates B-mode image data based on the fundamental wave echo.

The sub-harmonic processing unit 402 performs logarithmic amplification and envelope detection on the sub-harmonic echo obtained from the received wave, thereby converting a signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A-scope signal. Then, a signal is generated in which the instantaneous amplitude of each of the A-scope signals at each time point is set as a respective brightness value. further,
This signal is converted into a change signal per unit distance on the distance axis to obtain the absolute value of the differentiation, thereby generating B-mode image data. In this way, the sub-harmonic processing unit 402 generates B-mode image data based on the sub-harmonic echo.

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 a digital scan converter (DS).
C) The scan conversion in 404 converts the data in the sound ray data space into data in the physical space. 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 section 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 60
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.

Next, the operation of the ultrasonic transmitting / receiving apparatus according to one embodiment of the present invention will be described. The operator touches the ultrasonic probe 20 to a desired portion of the subject 10 and operates the operation unit 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 FIG. 6 may be performed.

The ultrasonic beam transmitted at this time has, for example, the sound pressure waveform shown in FIG. 8 and continuously oscillates the microbubbles 100 to reliably generate 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 scan-converted by the DSC 404, and
05 are respectively written. The operator scans the operation unit and causes the display unit 50 to display these B-mode images.
When the sub-harmonic echo of the microbubble is obtained, as shown in FIG. 12, the tomographic image 111 of the tissue obtained based on the fundamental wave echo and the sub-harmonic of the microbubble are displayed on the display 110 of the display unit. A composite image with the image 112 obtained based on the echo is displayed.

[0053]

As described above in detail, according to the present invention, it is possible to transmit / receive ultrasonic waves capable of obtaining an image with excellent spatial resolution, or to display subharmonic information at a speed close to real time. Possible ultrasonic transmission and reception can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an ultrasonic transmitting and receiving apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a state in which an ultrasonic wave transmitted from an ultrasonic transmission / reception device according to an embodiment of the present invention is incident on a subject.

FIG. 3 is a diagram for explaining an operation of an ultrasonic transducer in the ultrasonic transmitting and receiving apparatus according to one embodiment of the present invention.

FIG. 4 is a diagram showing an example of sound ray scanning in the ultrasonic transmission / reception device according to one embodiment of the present invention.

FIG. 5 is a diagram showing another example of sound ray scanning in the ultrasonic transmission / reception device according to one embodiment of the present invention.

FIG. 6 is a diagram showing still another example of sound ray scanning in the ultrasonic transmission / reception device according to one embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a sound pressure waveform of an ultrasonic wave transmitted by the ultrasonic transmission / reception device according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating another example of a sound pressure waveform of an ultrasonic wave transmitted by the ultrasonic transmission / reception device according to an embodiment of the present invention.

9A is a diagram illustrating an example of a sound pressure waveform of a transmission wave in the ultrasonic transmission / reception device according to the embodiment of the present invention, and FIG. 9B is a diagram illustrating an echo of a microbubble generated by the transmission wave; It is a figure showing an example of a waveform.

FIG. 10 is a diagram showing a circuit configuration for performing processing of received ultrasonic waves in the ultrasonic transmission / reception apparatus according to one embodiment of the present invention.

FIG. 11 is a diagram showing one-dimensional image data generated by the ultrasonic transmitting and receiving apparatus according to one embodiment of the present invention as a luminance signal.

FIG. 12 is a diagram showing an example of a display image in the ultrasonic transmission / reception device according to one embodiment of the present invention.

[Explanation of symbols]

1-5 Differential amplifier 6 Arithmetic unit 10 Subject 20 Ultrasonic probe 22a, 22b, ... Electrodes 23a, 23b, ... Piezoelectric element 30 Transmitter / receiver unit 40 Signal processing unit 50 Display unit 60 Control unit 70 Recording medium 100 Microbubble 200 Emission point 202 Sound ray 204 Trajectory 206 Two-dimensional area 208 Divergence point 311 Transmission / reception switching circuit 321 Transmission beamformer 322 Transmission transmission timing generation circuit 331 Receiving beamformer 400 Waveform processing unit 401 Fundamental wave processing unit 402 Subharmonic processing Unit 403 Image processing unit 404 Digital scan converter (DSC) 405 Image memory 910 Luminance signal X ₀ 911 Scattering of tissue a 912, 913 Scattering of two walls of tissue b 914 Scattering of tissue c 915 Micro injected into tissue b Bubble scattering 92 Microbubbles subharmonic signals are injected into a luminance signal X _SUB 925 tissue b

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C301 CC02 DD01 EE01 EE10 GB03 GB14 GB18 GB37 HH02 HH46 HH47 HH48 KK12 5D019 BB14 FF03 5J083 AA02 AB17 AC28 BB07 BC01 BC20 BD02 BD03 CB03 CB05 CB13 CB18 EB30 EA30

Claims (5)

[Claims] An ultrasonic probe including an ultrasonic transducer formed by alternately stacking a plurality of electrodes and a plurality of piezoelectric elements in a receiving direction; Detecting echoes generated by reflection of transmitted ultrasonic waves on the tissue of the subject using, based on output voltages of at least two of the plurality of electrodes, the ultrasonic transducer in the ultrasonic transducer An ultrasonic transmitting and receiving method, comprising: a step of obtaining a fundamental wave component in thickness resonance; and a step of obtaining image information on the tissue of the subject based on the fundamental wave component. 2. An ultrasonic probe including: transmitting an ultrasonic wave continuous for at least four periods to a subject; and an ultrasonic transducer formed by alternately stacking a plurality of electrodes and a plurality of piezoelectric elements in a receiving direction. Detecting echoes generated by reflection of transmitted ultrasonic waves on the tissue of the subject using, based on output voltages of at least two of the plurality of electrodes, the ultrasonic transducer in the ultrasonic transducer Obtaining a subharmonic component in thickness resonance. 3. The ultrasonic transmitting and receiving method according to claim 2, further comprising a step of injecting a microbubble contrast agent into the subject. 4. An ultrasonic probe including an ultrasonic transducer formed by laminating a plurality of electrodes and a plurality of piezoelectric elements alternately in a receiving direction, wherein an ultrasonic wave continuous for two or more cycles in a predetermined period is transmitted. Transmitted to the subject, the transmitted ultrasonic waves are reflected by the tissue of the subject to detect the echo generated by the ultrasonic probe, Based on the output voltage of at least two of the plurality of electrodes, An ultrasonic transmission / reception apparatus comprising: means for obtaining a fundamental wave component in thickness resonance in the ultrasonic transducer; and means for obtaining image information on the tissue of the subject based on the fundamental wave component. 5. An ultrasonic probe including an ultrasonic transducer formed by laminating a plurality of electrodes and a plurality of piezoelectric elements alternately in a receiving direction, and transmitting an ultrasonic wave continuous for at least four cycles to a subject. Then, the transmitted ultrasonic wave is reflected on the tissue of the subject, detects the echo generated and obtains a received signal, and based on an output voltage of at least two electrodes of the plurality of electrodes. Means for obtaining a subharmonic component in thickness resonance in the ultrasonic transducer.