JP2002065671A - Method and device for transmitting ultrasonic wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for transmitting ultrasonic wave, or the like, by which an image of superior spatial resolution can be obtained. SOLUTION: In one step, ultrasonic waves of two or more continuous cycles are transmitted to a subject 10, and in another step, an echo derived from reflection of transmitting wave from a tissue of the subject is detected by the use of an ultrasonic probe 20 in which a plurality of ultrasonic transducers 21 are arranged stepwise in a receiving direction. A step in which a first receiving signal R1 and a second receiving signal R2 mutually shifting a phase corresponding to a one cycle time for transmitting ultrasonic wave are obtained by selecting at least two in the plurality of the ultrasonic transducers 21 and a step in which the image information on the tissue of the subject 10 is obtained based on the difference between the first receiving signal R1 and the second receiving signal R2, are included.

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 tissue is transmitted, and how much tissue is disturbed during a certain time interval from the destruction of 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 the paper published in (99), it is known that continuous ultrasonic waves are generated. 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 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, it is an object of the present invention to obtain an image having excellent spatial resolution by utilizing an array of a plurality of ultrasonic transducer elements more effectively. It is an object of the present invention to provide an ultrasonic transmission / reception method and an ultrasonic transmission / reception device which can be used. Another object of the present invention is to provide an ultrasonic transmission / reception method and an ultrasonic transmission / reception apparatus capable of displaying subharmonic information at a speed close to real time by effectively utilizing an array of a plurality of ultrasonic transducer elements. It is to provide.

[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 that is continuous for at least a period to the subject, and detecting an echo generated by transmitting the ultrasonic wave to the subject tissue using an ultrasonic probe in which a plurality of ultrasonic transducers are arranged. Then, by selecting at least two of the plurality of ultrasonic transducers, a first reception signal and a second reception signal whose phases are shifted by a time corresponding to one period of the transmission ultrasonic wave are obtained. And a step of obtaining image information on the tissue of the subject based on a difference between the first received signal and the second received signal.

An ultrasonic transmission / reception method according to a second aspect of the present invention includes a step of transmitting an ultrasonic wave continuous for at least four periods to a subject, and an ultrasonic probe having a plurality of ultrasonic transducers arranged therein. Detecting an echo generated when the transmitted ultrasonic wave is reflected on the tissue of the subject by using at least two of the plurality of ultrasonic transducers, which corresponds to one cycle of the transmitted ultrasonic wave. The first received signal and the second
Obtaining a first received signal and a second received signal.
Extracting the sub-harmonic component of the echo based on the difference from the received signal.

Further, in the ultrasonic transmission / reception method according to the third aspect of the present invention, a step of transmitting an ultrasonic wave that is continuous for at least four periods to a subject in a predetermined period, and a plurality of ultrasonic transducers are arranged. Detecting an echo generated when the transmitted ultrasonic wave is reflected on the tissue of the subject using the ultrasonic probe, wherein at least two of the plurality of ultrasonic transducers are selected to transmit one of the transmitted ultrasonic waves; Obtaining a first received signal and a second received signal that are out of phase by a time corresponding to the period;
Obtaining a difference signal between the first received signal and the second received signal; and information about an echo generation position based on a difference between the difference signal in the first predetermined period and the difference signal in the second predetermined period. And obtaining a sub-harmonic component based on the sum of the difference signal in the first predetermined period and the difference signal in the second predetermined period.

An ultrasonic transmitting and receiving apparatus according to a first aspect of the present invention is an ultrasonic probe in which a plurality of ultrasonic transducers are arranged, and an ultrasonic wave that is continuous for two or more cycles in a predetermined period is applied to a subject. By selecting at least two of the plurality of ultrasonic transducers and an ultrasonic probe for transmitting and detecting an echo generated when the transmitted ultrasonic waves are reflected by the tissue of the subject, one of the transmitted ultrasonic waves is selected.
Means for obtaining a first received signal and a second received signal which are out of phase by a time corresponding to a cycle, and a method for obtaining a first received signal and a second received signal based on a difference between the first and second received signals. Means for obtaining image information.

An ultrasonic transmitting and receiving apparatus according to a second aspect of the present invention is an ultrasonic probe in which a plurality of ultrasonic transducers are arranged, and transmits ultrasonic waves continuous for four or more cycles to a subject. An ultrasonic probe that obtains a received signal by detecting an echo generated when the transmitted ultrasonic wave is reflected by the tissue of the subject, and selecting at least two of the plurality of ultrasonic transducers to transmit the ultrasonic wave. Means for obtaining a first received signal and a second received signal which are out of phase by a time corresponding to one cycle of an echo, and a sub-echo based on a difference between the first received signal and the second received signal. Means for extracting a harmonic component.

Further, an ultrasonic transmitting and receiving apparatus according to a third aspect of the present invention is an ultrasonic probe in which a plurality of ultrasonic transducers are arranged, and transmits ultrasonic waves continuous for at least four periods in a predetermined period. Selecting at least two of an ultrasonic probe and a plurality of ultrasonic transducers which transmit the ultrasonic waves to the subject and detect echoes generated by reflection of the transmitted ultrasonic waves on the tissue of the subject to obtain a reception signal; Means for obtaining a first reception signal and a second reception signal, which are out of phase by a time corresponding to one period of the transmission ultrasonic wave, and a difference signal between the first reception signal and the second reception signal. Means for obtaining the difference signal in the first predetermined period and the second signal.
And information on the echo occurrence position is obtained based on the difference between the difference signal and the difference signal in the predetermined period, and the sub-harmonic component is calculated based on the sum of the difference signal in the first predetermined period and the difference signal in the second predetermined period. And means for obtaining

[0020]

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, this ultrasonic transmitting / receiving apparatus has an ultrasonic probe 20 in which a plurality of ultrasonic transducers 21 are arranged. These ultrasonic transducers 21 are preferably arranged with a step in the receiving direction as shown in FIG. 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.

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 ultrasonic transducers constituting the transmission aperture of the ultrasonic probe 20 transmit a plurality of ultrasonic 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.
Receives the ultrasonic wave (echo) reflected from the subject 10 and converts it into an electric signal,
11 to the receiving beamformer 331. In this way, a plurality of echo signals received by the plurality of ultrasonic transducers 21 constituting the receiving aperture of the ultrasonic probe 20 are input to the receiving beamformer 331.

The receiving beamformer 331 selects at least two ultrasonic transducers from among the plurality of ultrasonic transducers 21 so that two receiving transducers whose phases are shifted by a time corresponding to one cycle of transmitting ultrasonic waves. Get the signal. For example, to obtain the received signals S ₁ from the ultrasonic transducer T _1, to obtain a reception signal S ₂ from the ultrasonic transducer T _2. Here, one wavelength of the transmission ultrasonic wave is λ, and the ultrasonic transducer T
L ₁ the distance to _1, and the distance from the reflection point of the subject 10 to the ultrasonic transducer T ₂ and L _2, L ₂ -L ₁ =
λ.

Further, the reception beamformer 331 adjusts the phase by giving 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, the reception signal May be performed. The receive beamformer 331 receives the received signal S ₁ ,
Processes the S _2, and outputs transmission ultrasound of the first phase by a time corresponding to one period is offset in the received signal R ₁ and the second reception signal R ₂ finally.

The transmission of the ultrasonic beam is repeatedly performed at predetermined time intervals by a 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 transmitting / receiving unit 30 having such a configuration performs, for example, scanning as shown in FIG. In FIG. 3, an ultrasonic beam (sound ray 202) extending from the radiation point 200 in the z direction 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 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. 4, a sound ray 202 extending from a radiation point 200 in the z direction 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. 5 can be performed by sound ray scanning similar to linear scanning. In FIG. 5, 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.

Referring again to FIG. 1, the output of the receive beamformer 331 is output to the waveform processing section 400 of the signal processing section 40.
It is connected to the. The waveform processing unit 400 separates a fundamental wave component and a 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 the processed signals to the image processing unit 403. 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.

Each part of the waveform processing section 400 to the image processing section 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 CDROM, a DVDROM, or the like corresponds to this.

First, a first example of the ultrasonic transmission / reception method according to the present embodiment will be described. In a first embodiment, the ultrasound beam transmitted by the ultrasound probe is
In the convergence region, for example, it is set so as to generate a continuous wave forming a sound pressure waveform shown in FIG. In this embodiment, 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.

Here, the reason why the period is set to two or more periods is that the difference between the first received signal and the second received signal is obtained in the signal processing described later, so that the period for stabilizing the transmission oscillator is set. It is necessary. 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. In addition, 1MHz
In the case of using the ultrasonic wave of 50,000, the 50,000 cycle is 1/2.
It corresponds to 0 seconds. Also, the upper limit of the number of periods of continuous waves is
It is more preferably at most 10,000 wavelengths, and still more preferably at most 1,000 wavelengths.

FIG. 7 shows a part of the configuration of the waveform processing section in the first embodiment. A first obtained by selecting at least two of the plurality of ultrasonic transducers
And the second received signal are out of phase by a time corresponding to one cycle of the transmitted ultrasonic wave. The difference circuit 2 calculates a difference between the first received signal and the second received signal, and outputs the obtained difference signal. The delay circuit 3 calculates the difference signal as 1
It is delayed by the number of transmission periods T ₀ . The subtraction circuit 4 calculates the difference between the difference signal and the delayed difference signal.
Find the sum of the difference signal and the delayed difference signal. Selection circuit 6
Selects the output of the subtraction circuit 4 when k is an even number,
Is odd, the output of the adder circuit 5 is selected and output to the fundamental wave processing unit 401 (FIG. 1) as a fundamental wave echo.

Next, the operation of the waveform processing section in the first embodiment will be described with reference to FIG. FIG. 8A shows a waveform of a transmission wave. Transmitting wave has a k / 2 wavelengths continuous structure between the transmitting period T ₀ of the ultrasonic fundamental period τ is 1 times (k is an integer of 4 or more).
Such a transmission wave is incident on the subject 10 shown in FIG. FIG. 8B shows a _first received signal R ₁ that is an echo signal, and FIG. 8C shows a second received signal R ₂ that is an echo signal. These echo signals are reflected by the tissues a, b, and c of the subject 10 shown in FIG. 3 and become complex. Also, the second received signal R ₂
Is the fundamental period τ of the transmitted wave with respect to the first received signal R ₁
Only the phase is delayed.

Here, a difference between the first received signal R ₁ and the second received signal R ₂ is obtained, and a waveform R _TOTAL shown in FIG. 8D is created. The waveform R _TOTAL created in this way is k
If There is even a pulse P _TOP located at the head of the waveform to be continuous between the first transmitting period T _0, situated immediately after the first transmitting period T _0, the pulse P _TOP And a pulse P _LAST having an inverted sign. On the other hand, if k is an odd number, waveform R _{TO TAL} includes a pulse P _TOP located at the head of the waveform to be continuous between the first transmitting period T _0, immediately after the first transmitting period T ₀ And includes a pulse P _LAST having the same sign as the pulse P _TOP . Here, the pulse P
_TOP is and the pulse P _LAST, are shifted by transmitting period T ₀ of 1 times on the time axis. Therefore, the waveform R _{TOTAL obtained} by removing the waveform R _TOTAL from the end by T ₀ on the time axis is referred to as a waveform R _TOP shown in FIG. _8E , and the waveform R _TOTAL is represented by T ₀ from the beginning on the time axis.
A waveform _RLAST shown in FIG.

Further, when k is an even number, R_TOP-R
_LASTAnd if k is odd, R_TOP+ R _LASTOf FIG.
Waveform R shown in (g)₀Asking. In this way
Waveform R₀The magnitude of the first pulse is
Luth P_TOPAnd pulse P_LASTAnd the sum of the absolute values of
You. Also, the waveform R₀Shows the scattering 80 of the tissue a shown in FIG.
1. Scattering 802 and 803 of two walls of tissue b, tissue c
Are extracted. Calculated as above
Waveform R₀Is a fundamental wave echo. In addition, (h) of FIG.
Will be described in another embodiment.

In the first embodiment, an example has been described in which B-mode imaging is performed using ultrasonic waves that are continuous for two or more cycles. However, ultrasonic imaging is not limited to B-mode imaging. You may make it capture a dynamic image using Doppler shift.

Next, a second example of the ultrasonic transmission / reception method according to the present embodiment will be described. In a second embodiment, the ultrasound beam transmitted by the ultrasound probe is
In the convergence region, for example, it is set so as to generate a continuous wave that forms the sound pressure waveform shown in FIG. As shown in FIG. 9, the sound pressure waveform is a continuous wave for n periods (wavelengths) (n is an integer of 4 or more). The subharmonic is n / m with respect to the transmission wavelength λ.
It is a sound wave having twice the wavelength (m is a natural number and n and m are independent), and in particular, a sound wave having a wavelength of m = 2 tends 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. 10A shows an example of such a transmission wave waveform. FIG. 10B shows an example of an echo waveform of a microbubble generated by the transmission wave.

In FIG. 1, the first reception signal and the second reception signal obtained by selecting at least two of the plurality of ultrasonic transducers 21 have a time corresponding to one period of the transmission ultrasonic wave. Out of phase. The waveform processing unit according to the second embodiment extracts a sub-harmonic component from the reception signal input from the reception beamformer 331 by calculating a difference between the first reception signal and the second reception signal. Output to the harmonic processing unit 402.

Next, the operation of the waveform processing section in the second embodiment will be described with reference to FIG. FIG.
FIG. 4 is a waveform chart for explaining processing of a received wave in the waveform processing unit. As shown in FIG. 11, in the echo of the microbubble, the first received signal R ₁ and the second received signal R ₂ are out of phase by the fundamental period τ of the transmission wave. The waveform processing unit obtains a difference between the first received signal R ₁ and the second received signal R ₂ to obtain a subharmonic signal waveform R ₃ . 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 harmonic are the fundamental period τ of the transmitted wave.
Is a repetition unit, and is removed by the above-described signal processing. As a result, only the sub-harmonic signal remains.

In the second embodiment, 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, and uses Doppler shift of sub-harmonic echoes. Alternatively, a dynamic image may be taken.

Finally, a third example of the ultrasonic transmission / reception method according to the present embodiment will be described. In the third embodiment, the ultrasonic beam transmitted by the ultrasonic probe is set so as to generate a continuous wave in the convergence region, for example, forming a sound pressure waveform shown in FIG. As shown in FIG. 9, the sound pressure waveform is a continuous wave for n periods (wavelengths) (n is an integer of 4 or more). Desirably, 4 ≦ n ≦ 5 × 10 ⁴ , and the continuous wave includes a wave of 4 cycles or more and 50,000 cycles or less.

FIG. 12 shows a part of the configuration of the waveform processing section in the third embodiment. The first reception signal and the second reception signal obtained by selecting at least two of the plurality of ultrasonic transducers are out of phase by a time corresponding to one cycle of the transmission ultrasonic wave. The difference circuit 2
The difference between the first received signal and the second received signal is obtained, and the obtained difference signal is output. The delay circuit 3 converts this difference signal into
It is delayed by one transmission period T ₀ . The subtraction circuit 4
A difference between the difference signal and the delayed difference signal is obtained to extract a fundamental wave component, which is output to the fundamental wave processing unit 401 (FIG. 1). Further, the addition circuit 5 extracts a sub-harmonic component by calculating the sum of the difference signal and the delayed difference signal, and outputs the extracted sub-harmonic component to the sub-harmonic processing unit 402 (FIG. 1).

Next, the operation of the waveform processing unit in the third embodiment will be described with reference to FIG. FIG. 8A shows a waveform of a transmission wave. Transmitted wave has n wavelengths continuous structure between the transmitting period T ₀ of the ultrasound batch of fundamental period tau (n is an even number of 4 or more). Such a transmission wave is incident on the subject 10 shown in FIG.
FIG. 8B shows a first reception signal R ₁ which is an echo signal.
FIG. 8C shows the second echo signal.
₂ shows the received signal R2. The echo signal is reflected by the tissues a, b, and c of the subject 10 shown in FIG. Further, the phase of the second received signal R ₂ is delayed from the first received signal R ₁ by the fundamental period τ of the transmission wave.

Here, the difference between the first received signal R ₁ and the second received signal R ₂ is obtained, and R _TOTAL shown in FIG. 8D is created. Thus waveform R _TOTAL created by the pulse P _TOP located at the head of the waveform to be continuous between the first transmitting period T _0, situated immediately after the first transmitting period T _0, pulses P _TOP and it includes a pulse P _LAST sign is inverted, and a sub-harmonic components match the phase in the first transmitting period and the next transmit time relative. Here, the pulse P
_TOP is and the pulse P _LAST, are shifted by transmitting period T ₀ of 1 times on the time axis. Therefore, the waveform R _{TOTAL obtained} by removing the waveform R _TOTAL from the end by T ₀ on the time axis is referred to as a waveform R _TOP shown in FIG. _8E , and the waveform R _TOTAL is represented by T ₀ from the beginning on the time axis.
A waveform _RLAST shown in FIG.

Further, R_TOP-R_LASTTo (g) of FIG.
Waveform R shown in₀Asking. Waveform R ₀In the sub
The harmonic component disappears and the waveform R_TOPAnd waveform R_LASTof
Only the sum of the absolute values is obtained. As described above
Waveform R₀Is calculated by the waveform processing unit 400 shown in FIG.
The result is output to the fundamental wave processing unit 401.

Also, R_TOP+ R_LASTInto (h) of FIG.
Waveform R shown_SUBAsking. Waveform R _SUBIn the
Luth P_TOPAnd pulse P_LASTDisappears and subharmonic
Only components. The waveform R obtained as described above
_SUBIs the calculation result of the waveform processing unit 400 shown in FIG.
And outputs the result to the sub-harmonic processing unit 402.

Here, one-dimensional image data generated based on the waveform R ₀ in FIG. 8G is shown as a luminance signal X ₀ 910 in FIG. 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. 2 are extracted.

One-dimensional image data generated based on the waveform R _SUB 920 of FIG. 8H is shown as a luminance signal X _SUB 920 in FIG. 13B. Luminance signal X
_{In SUB} , a subharmonic signal 925 of the microbubble injected into the tissue b shown in FIG. 2 is extracted.

In the third embodiment, an example has been described in which B-mode imaging is performed by using ultrasonic waves that are continuous for four or more cycles. However, ultrasonic imaging is not limited to B-mode imaging, and it is not limited to B-mode imaging. You may make it capture a dynamic image using Doppler shift.

Referring to FIG. 1 again, image processing in the ultrasonic transmitting / receiving apparatus according to one embodiment of the present invention will be described in detail. The fundamental wave processing unit 401 and the sub-harmonic processing unit 402 are 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 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 transmission / reception unit 30 and the signal processing unit 40 are connected to the control unit 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. 3, 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. 4 or FIG. 5 may be performed.

The ultrasonic beam transmitted at this time has, for example, the sound pressure waveform shown in FIG. 9 and continuously vibrates the microbubbles 100 to reliably generate 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 a subharmonic echo of a microbubble is obtained, as shown in FIG. 14, a tomographic image 111 of the tissue obtained based on the fundamental wave echo and a subharmonic 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.

[0061]

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

FIG. 4 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. 5 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. 6 is a diagram illustrating a sound pressure waveform of an ultrasonic wave transmitted by the ultrasonic transmission / reception method according to the first embodiment of the present invention.

FIG. 7 is a block diagram illustrating a part of a configuration of a waveform processing unit according to the first embodiment of the present invention.

FIG. 8 is a waveform chart for explaining processing of a received wave in the first and third embodiments of the present invention.

FIG. 9 is a diagram showing a sound pressure waveform of an ultrasonic wave transmitted by the ultrasonic transmitting and receiving method according to the second and third embodiments of the present invention.

FIG. 10A is a diagram illustrating an example of a waveform of a transmission wave according to a second embodiment of the present invention, and FIG. 10B is a diagram illustrating an example of an echo waveform of microbubbles generated by the transmission wave; It is.

FIG. 11 is a waveform chart for explaining processing of a received wave in the second embodiment of the present invention.

FIG. 12 is a block diagram illustrating a part of a configuration of a waveform processing unit according to a third embodiment of the present invention.

FIG. 13 is a diagram showing one-dimensional image data generated as a luminance signal in the ultrasonic transmission / reception device according to the third embodiment of the present invention.

FIG. 14 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]

Reference Signs List 2 difference circuit 3 delay circuit 4 subtraction circuit 5 addition circuit 10 subject 20 ultrasonic probe 30 transmission / reception section 40 signal processing section 50 display section 60 control section 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 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 Scattering of microbubbles injected into tissue b 920 Luminance signal X _SUB 925 Injecting into tissue b Was Microbubble subharmonic signal

Claims (9)

[Claims] A step of transmitting an ultrasonic wave that is continuous for at least two periods to a subject; and transmitting the ultrasonic wave to a tissue of the subject using an ultrasonic probe in which a plurality of ultrasonic transducers are arranged. Detecting a resulting echo, wherein at least two of the plurality of ultrasonic transducers are selected to provide a first received signal that is out of phase by a time corresponding to one period of transmitted ultrasonic waves; An ultrasonic transmission / reception method, comprising: obtaining a second reception signal; and obtaining image information on the tissue of the subject based on a difference between the first reception signal and the second reception signal. . 2. A step of transmitting an ultrasonic wave continuous for at least k / 2 periods to a subject in a predetermined period (k is an integer of 4 or more), and using an ultrasonic probe in which a plurality of ultrasonic transducers are arranged. Detecting an echo generated by reflection of the transmitted ultrasonic wave on the tissue of the subject, wherein at least two of the plurality of ultrasonic transducers are selected to correspond to one cycle of the transmitted ultrasonic wave. Obtaining a first received signal and a second received signal that are out of phase by the time required, obtaining a difference signal between the first received signal and the second received signal, and k is an even number Obtaining image information about the tissue of the subject based on a difference between the difference signal during a first predetermined period and the difference signal during a second predetermined period, where k is an odd number Obtaining image information about the tissue of the subject based on a sum of the difference signal in a first predetermined period and the difference signal in a second predetermined period. Method. Transmitting an ultrasonic wave continuous for at least four periods to the subject; and transmitting the ultrasonic wave to the tissue of the subject using an ultrasonic probe on which a plurality of ultrasonic transducers are arranged. Detecting a resulting echo, wherein at least two of the plurality of ultrasonic transducers are selected to provide a first received signal that is out of phase by a time corresponding to one period of transmitted ultrasonic waves; An ultrasonic transmitting and receiving method, comprising: obtaining a second received signal; and extracting a sub-harmonic component of the echo based on a difference between the first received signal and the second received signal. 4. A step of transmitting an ultrasonic wave continuous for at least four cycles to a subject in a predetermined period, and transmitting ultrasonic waves to the tissue of the subject using an ultrasonic probe in which a plurality of ultrasonic transducers are arranged. Detecting an echo generated by reflection of the first ultrasonic wave, wherein at least two of the plurality of ultrasonic transducers are selected to shift the phase by a time corresponding to one cycle of the transmitted ultrasonic wave. Obtaining a received signal and a second received signal, obtaining a difference signal between the first received signal and the second received signal, and obtaining the difference signal and the second signal during a first predetermined period. Obtaining information on an echo generation position based on a difference between the difference signal and the difference signal in a predetermined period of time; Ultrasonic wave transmission and reception method comprising the steps of: obtaining a sub-harmonic component based on the sum of the serial differential signal. 5. The ultrasonic transmission / reception method according to claim 3, further comprising a step of injecting a microbubble contrast agent into the subject. 6. An ultrasonic probe in which a plurality of ultrasonic transducers are arranged, wherein an ultrasonic wave that is continuous for at least two periods in a predetermined period is transmitted to the subject, and the transmitted ultrasonic wave is transmitted to the subject. The ultrasonic probe for detecting an echo generated by being reflected by tissue; and at least two of the plurality of ultrasonic transducers
Means for obtaining a first reception signal and a second reception signal that are out of phase by a time corresponding to one period of the transmission ultrasonic wave by selecting one of the first reception signal and the second reception signal. Means for obtaining image information about the tissue of the subject based on the difference between the received signal and
An ultrasonic transmitting and receiving device comprising: 7. An ultrasonic probe in which a plurality of ultrasonic transducers are arranged, transmitting an ultrasonic wave continuous for at least k / 2 cycles to a subject in a predetermined period (k is an integer of 4 or more), The ultrasonic probe for obtaining a received signal by detecting an echo generated when the transmitted ultrasonic wave is reflected by the tissue of the subject; and at least two of the plurality of ultrasonic transducers
Means for obtaining a first reception signal and a second reception signal that are out of phase by a time corresponding to one period of the transmission ultrasonic wave by selecting one of the first reception signal and the second reception signal. Means for obtaining a difference signal from the received signal of the subject; and, if k is an even number, the subject is determined based on a difference between the difference signal in a first predetermined period and the difference signal in a second predetermined period. Image information on the tissue of the subject, and when k is an odd number, the image information on the tissue of the subject is based on the sum of the difference signal in a first predetermined period and the difference signal in a second predetermined period. Means for obtaining image information. 8. An ultrasonic probe in which a plurality of ultrasonic transducers are arranged, the ultrasonic probe transmitting ultrasonic waves continuous for four or more cycles to a subject, and the transmitted ultrasonic waves are reflected by the tissue of the subject. The ultrasonic probe for detecting a resulting echo to obtain a reception signal; and at least two of the plurality of ultrasonic transducers
Means for obtaining a first reception signal and a second reception signal that are out of phase by a time corresponding to one period of the transmission ultrasonic wave by selecting one of the first reception signal and the second reception signal. Means for extracting a subharmonic component of the echo based on a difference between the received signal and the received signal. 9. An ultrasonic probe in which a plurality of ultrasonic transducers are arranged, wherein an ultrasonic wave that is continuous for at least four periods in a predetermined period is transmitted to a subject, and the transmitted ultrasonic wave is transmitted to the subject. The ultrasonic probe for obtaining a reception signal by detecting an echo generated by being reflected by tissue; and at least two of the plurality of ultrasonic transducers
Means for obtaining a first reception signal and a second reception signal that are out of phase by a time corresponding to one period of the transmission ultrasonic wave by selecting one of the first reception signal and the second reception signal. Means for obtaining a difference signal from the received signal, and obtaining information on an echo generation position based on a difference between the difference signal in a first predetermined period and the difference signal in a second predetermined period. Means for obtaining a sub-harmonic component based on the sum of the difference signal in the predetermined period of time and the difference signal in the second predetermined period of time.