JP2002224111A - Ultrasonic image picking-up and lithography system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate between a higher harmonic component contained in the response signal of biological tissue and a higher harmonic component contained in the response signal of a contrast medium to extract both components. SOLUTION: A transmission part 20 transmits a plurality (M; with the provi so that natureal number of >=2) of sine wave like ultrasonic wave signals of at least one cycle in the same direction as ultrasonic beam so as to leave a time interval and the ultrasonic signal of each time is transmitted while first and second waveforms asymmetric with respect to a phase axis or polarity are alternately changed over. Each of the first and second waveforms has a plurality of frequency components and at least the amplitude of a first half wave is set larger than the amplitude of the succeeding waveform. A receiving part 30 subjects the response signals of plural (M) times of ultrasonic waves to phasing processing to be added or subtracted to attenuate the response signal of biological tissue.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic contrast drawing apparatus for drawing information necessary for diagnosis, such as blood flow distribution information, using an ultrasonic contrast agent. The present invention relates to a technology for enabling drawing.

[0002]

2. Description of the Related Art As a method for measuring blood flow distribution information in a living tissue, an ultrasonic contrast drawing method and apparatus using an ultrasonic contrast agent have been studied. For example, the document "Ultra Sound In Medicine and Biology (Ultr
asound in Medicine & Biology), Vol. 26, No. 6, p.
965, 2000, "Ultrasound Contrast Imaging: Current
and New Potential Methods: Peter JA Frinking e
t al. ""It is described in.

[0003] A contrast medium for ultrasonic waves is generally formed by mixing a large number of bubbles into a medium such as physiological saline. Air bubbles
For example, it is formed by covering an inert gas (such as C ₃ F ₈ , C ₄ F ₁₀ ) with a protein film or a lipid film. The particle size distribution of the bubbles is, for example, a Gaussian normal distribution, and the average particle size is several μm. However, it is known that particles of 0.5 μm or less aggregate with each other to form a substantially large particle size,
It becomes a distorted normal distribution.

[0004] Such a contrast agent is generally produced from a vein.
Injected into the body. Ultrasound on contrast agent injected into the body
When the beam is irradiated, bubbles are deformed if the sound pressure is low
The acoustic information accompanying the deformation is mixed with the reflected signal,
It is emitted as a sound wave response signal. Also, if the sound pressure is high
In this case, the bubbles are destroyed and strong acoustic information is emitted. sand
That is, the ultrasonic contrast agent has a non-linear response to ultrasonic irradiation.
And the fundamental frequency f ₀Response when irradiating
The signal has a fundamental frequency component f₀In addition to the signal corresponding to
Harmonic component 2f of double frequency₀Is said to contain
ing.

[0005] Therefore, conventionally, the center frequency by using a relatively narrow bandpass filter 2f _0, by extracting the 2f _0, have been made to detect the presence of the contrast agent. In other words, the presence or absence of 2f ₀ corresponds to the presence or absence of the contrast agent, 2
Since the magnitude of f ₀ corresponds to the spatial density distribution of the contrast agent,
It is possible to draw which part of the tissue the contrast agent flows into.

[0006] By the way, in a drawing method using a contrast agent, it is roughly classified into an initial stage and a late stage according to a time phase after the contrast agent is injected into a vein. The initial stage is a phase in which an ultrasonic contrast agent injected from a vein flows into a tissue such as a liver to be diagnosed by blood circulation. The latter period is a time phase in which it is assumed that the ultrasonic contrast agent that has flowed into or distributed into the tissue sufficiently flows out of the tissue by blood circulation 3 to 8 minutes after the injection of the contrast agent from the vein. In the initial time phase, generally, an ultrasonic sound pressure that does not destroy the contrast agent but generates sufficient harmonics (for example, MI: mechanical index =
0.2) is used. In the late phase, most of the contrast agent flows out of the tissue, but some are trapped within the tissue. The presence or absence of this trap is considered to be different between a diseased part and a healthy part of the tissue. In this late phase, when an ultrasonic wave of high sound pressure (for example, MI = about 0.8 or more is said to be destroyed) that destroys the contrast agent is applied, strong reflection occurs when the contrast agent is destroyed. Produces a signal. Therefore, by detecting this, a region where the contrast agent is trapped, that is, a diseased portion, and a region where the contrast agent is not trapped, that is, a healthy portion can be distinguished, which can contribute to diagnosis.

On the other hand, as a method of extracting a harmonic using a non-linearity of the frequency of a contrast agent response signal without using a band-pass filter, conventionally, US Pat. No. 5,632,277 and US Pat. No. 5,706,819 have been proposed. ing. According to these, after irradiating the inside of a living body with an ultrasonic pulse based on the first ultrasonic signal and receiving the response signal, the second ultrasonic signal in which the polarity of the first ultrasonic signal is inverted at a short time interval. And irradiates an ultrasonic pulse based on the ultrasonic signal to receive a response signal. Then, by adding the received signals and the like, the component corresponding to the fundamental frequency component in the response signal is removed, and the harmonic component is extracted or emphasized, thereby detecting the contrast agent with high accuracy. is there.

Further, JP-A-2000-300554 discloses, as a period _{t 1} of the first ultrasonic signal is the signal level becomes a positive constant value, time _{t 2} the signal level becomes a negative constant value
Have a waveform that follows in this order, and a second waveform that has a waveform obtained by inverting the first ultrasonic signal with respect to the time axis.
Is proposed. According to this, the symmetry of the ultrasonic pulse based on the first and second ultrasonic signals is enhanced, and the signal of the fundamental wave component (linear component) can be reduced.

[0009]

Any of the above-mentioned prior arts is effective for extracting or enhancing a harmonic component caused by a contrast agent. However, no consideration is given to a case where the harmonic component contained in the tissue response signal is not negligible compared to the harmonic component contained in the contrast agent response signal. Therefore, it may not be possible to extract a high-frequency component contained in the response signal of the contrast agent at a high rate.

That is, the non-linear phenomenon which is the key of the conventional contrast agent detection occurs not only with the contrast agent but also with the propagation of ultrasonic waves in the tissue. In this case, twice the harmonic component 2f ₀ of the ultrasound of the basic frequency frequency f ₀ irradiated is known to occur. In particular, the signal of the harmonic component 2f ₀ included in the response signal of tissue, the intensity increases as the depth increases. Therefore, compared to the signal of the harmonic component 2f ₀ included in the response signal of the contrast medium, at the same level or greater level, reducing the accuracy of the contrast agent detection. For example, when detecting the contrast medium in a blood vessel that is buried in the tissue as the blood flow in the liver, 2f from both the contrast agent and the tissue ₀
Is emitted, and the presence of the contrast agent may be erroneously detected.

Accordingly, an object of the present invention is to discriminate and extract a harmonic component contained in a response signal of a living tissue and a harmonic component contained in a response signal of a contrast agent.

[0012]

First, the principle of the present invention will be described with reference to FIG. FIG. 2 is a result of a detailed study of the nonlinear response of the contrast agent and the tissue to the ultrasonic irradiation, and schematically shows a spectrum of a response signal when the contrast agent distributed in the tissue is irradiated with the ultrasonic wave.
The horizontal axis in the figure represents the frequency, and the vertical axis represents the signal strength of each component. FIG. 3A shows a response signal from a relatively shallow portion near the probe, and FIG. 3B shows a response signal from a relatively deep portion far from the probe. As can be seen from these figures, in both the shallow region and the deep region, the response signal 1 of the contrast agent has a harmonic component over a wide frequency band in addition to the fundamental component corresponding to the fundamental frequency f _0. include. On the other hand, the response signal 2 organizations, appearing divided into a harmonic component 2b of the fundamental wave component 2a and the second harmonic 2f ₀ of the fundamental frequency f _0. In the case of a shallow portion, the harmonic component 2b is not so strong. However, in the case of a deep portion, the harmonic component 2b becomes extremely strong, and becomes stronger than the signal intensity of the response signal 1 of the contrast agent. This is because, as described above, the harmonic component 2b included in the response signal of the tissue is generated by a non-linear effect when the ultrasonic wave propagates through the tissue. This is because the length increases. Therefore, as in the prior art, to extract the components of the harmonics 2f ₀ uniformly, even if an attempt is emphasized response signal of the contrast agent, with the exception of the shallow region, is emphasized harmonics 2f ₀ of the tissue Therefore, the sharpness of the contrast image cannot be improved.

Here, matters derived from the consideration of FIG. 2 will be summarized. (1) Frequency component of contrast agent response signal (non-linear response)
Are not localized at 2f ₀ but distributed over a wide band. This tendency is more remarkable as the frequency spectrum of the transmitted ultrasonic signal is wider. (2) The response signal of the contrast agent strongly depends on the diameter of the contrast agent, and is significantly emphasized at the free resonance frequency fR of the contrast agent. As described above, since the contrast agent has a particle size distribution, harmonics appear in a wide frequency band. (3) The fundamental component of the contrast agent response signal is as strong as the fundamental component of the tissue response signal. (4) harmonic of the response signal of a tissue is localized to the vicinity of relatively 2f ₀ regardless of the intensity of the ultrasonic sound pressure. (5) The harmonics of the tissue response signal are significantly weaker in the case of relatively low ultrasonic sound pressure and in the case of a shallow site than the harmonic components of the contrast agent.

In view of the above considerations (1) to (5), the present invention
Solves the above problems by means of the following features:
It is decided. (First feature) A specific frequency from a response signal is transmitted to a receiving unit.
Providing a filter to extract several components and passing through this filter
The average bandwidth of the ultrasonic signal transmitted to the ultrasonic probe
Wave number f₀0.8f₀~ 2.5f₀Within the range of
It is characterized by setting. That is, the response signal of the contrast agent
Signals are distributed over a wide frequency band and the signal strength is also wide.
In the conventional frequency band.
And 2f₀Wide frequency band 0.8-2.5f without limitation₀
Are extracted with a band-pass filter. this
The contrast agent response signal compared to the tissue response signal.
Can be emphasized on the contrary. In particular, relatively weak sound pressure
In the case (initial phase), the harmonic component 2f of the tissue ₀Ignore
It is effective because it gains.

By the way, in case of high sound pressure (late time phase)
It may not be able to ignore the harmonic component 2f ₀ of the tissue. In this case, set the bandwidth of the bandpass filter to 0.8 to
In the 1.8F _0, preferable to remove the harmonic component 2f ₀ of the tissue. That is, to remove or attenuate the harmonic component 2f ₀ was exclusively be emphasized in the prior art, there are other features of the present invention. In this case, although accompanied by attenuation of the harmonic components of the contrast medium distributed in the vicinity of 2f _0, 0.8~1.8f
_Since the response signal of the contrast agent distributed in a wide frequency band near ₀ is extracted, the above-mentioned attenuation is more than compensated.

[0016] In addition, changes harmonic strength of the component 2f ₀ of the organization at a shallow depth of the site and a deep depth site. Therefore, indexing the temporal position of the response signal corresponding to the depth portion of the ultrasound beam, the response signal deeper than the set depth depth, so as to attenuate harmonics 2f ₀ a pass band width of the filter in real time It is desirable to switch. As the filter for attenuating harmonic components 2f _0, et bandpass filter, the center frequency can be used a band-elimination filter 2f _0. Further, the fundamental wave component of the tissue response signal present in the vicinity of f ₀ may be artifacts in the contrast medium image also include components due to human breathing and beating. In this case, it is preferable that 1.2~1.8f to ₀ set the pass bandwidth of the filter somewhat narrow.

In this manner, the harmonic 2f _{0 of the} tissue can be distinguished from the harmonic contained in the response signal of the contrast agent. By detecting and drawing the contrast agent based on the harmonics of the response signal of the contrast agent extracted and extracted, it is possible to improve the SN ratio of the contrast image as compared with the related art. (Second feature) As described above, the first feature of the present invention is as follows.
In order to emphasize and extract the response signal component of the contrast agent, the pass band width of the filter of the receiving unit is expanded. In order to further promote the effect of the first feature, it is preferable to widen the frequency of the ultrasonic wave applied to the contrast agent. That is, it is desirable that the transmission unit be configured to transmit an ultrasonic signal having a plurality of frequency components to the ultrasonic probe. That is, since the contrast agent has a distributed free resonance frequency corresponding to its particle size distribution, more contrast agents respond by distributing the frequency spectrum of irradiation ultrasonic waves over a wide band, and the contrast agent The response signal itself is enhanced. As a result, the tissue response signals are f ₀ and 2f
₀ whereas the centered, the response signal of the contrast agent appears in strong level over a wider frequency band, it is easy to further distinguish between harmonic tissue harmonics and contrast agents. (Third Feature) The first and second features described above are directed to a case where contrast drawing is performed based on a response signal received by one irradiation of an ultrasonic beam. However, the first and second features of the present invention are not limited to the contrast drawing method using the single irradiation method of the ultrasonic beam, and the contrast drawing method using the so-called double irradiation method (or the multiple irradiation method) described below. Also applicable to In particular, the multiple irradiation method is effective when drawing by detecting the disappearance due to movement or destruction of the contrast agent in real time. In other words, when detecting the movement or disappearance of the contrast agent,
Two images are required before and after the movement or before and after the disappearance. However, when a contrast medium is drawn by a single irradiation method, the time interval between two images is one frame time interval (1
0-20 ms). Therefore, when detecting a site with a high blood flow velocity or a rupture of a contrast medium, a multiple irradiation method is suitable. In the multiple irradiation method, the ultrasonic beam is irradiated at least twice in the same direction at extremely short time intervals,
The response signals corresponding to each irradiation are compared, and the response signals are compared to determine whether the contrast agent has moved from above the ultrasonic beam within a predetermined time interval, or whether the contrast agent has been destroyed and disappeared. That can be detected.

Specifically, the transmitting section of the ultrasonic wave transmits a plurality of ultrasonic beams at a time interval in the same direction (M, where M ≧ M).
2) The ultrasonic signal has a function of transmitting waveforms having different frequencies, at least the amplitude of the leading waveform is larger than the amplitude of the continuous waveform group, and the signal of each of these times has a polarity. It is assumed that the waveforms are set asymmetrically with respect to the inversion and the time axis inversion and the waveforms are transmitted. In accordance with this, the receiving unit performs a phasing process on the response signal of the ultrasonic signal a plurality of (M) times, and attenuates the response signal of the living tissue by adding or subtracting the phasing-processed response signal. It is characterized by having a function to perform. In this case, it is most preferable to equalize the respective mean frequency f ₀ of the first waveform and the second waveform.

According to this, since the frequency band of the ultrasonic wave radiated into the living body is widened as compared with the conventional double irradiation method, the harmonic components included in the response signal of the contrast agent are enhanced over a wide frequency band. be able to. At the same time, the frequency spectrum of the response signal of the contrast medium also frequency shift, by adding or subtracting processing, will be widely distributed to the band around 1.2f ₀ to 1.8F _0. As a result, the harmonic component included in the response signal of the living tissue can be distinguished from the harmonic component included in the response signal of the contrast agent.
Then, by detecting and drawing the contrast agent based on the harmonics of the response signal of the discriminated contrast agent, the S / N ratio of the contrast image can be improved as compared with the related art.

[0020] For example, the frequency spectrum of the response signal of the contrast medium obtained by adding or subtracting processing, 1.2f ₀ to
Are highlighted in the band of 1.8f close to _zero, it is attenuated but rather in the vicinity of 2f _0. Therefore, by performing the reception processing on the response signal over a wide frequency band, the response signal S
The N ratio can be increased, and the response signal of the contrast agent can be selectively drawn.

In particular, each of the above waveforms has a frequency
, Fn,..., FN (where N ≧ 2
N) continuous N waveforms, and f1 to fN
Average frequency is f₀And the frequency components f1 to fN
Cloth width Δf is 0.0f₀~ 0.4f ₀Must be within the range
Is preferred. According to this, the response signal composition of the contrast agent is further increased.
Minutes can be emphasized. In addition, the frequency distribution width Δf
There is no particular limitation, but preferably 0.1 f₀~ 0.4f₀Range of
And 0.2 f₀~ 0.3f₀In the range of
It is practical from the road configuration. In addition, the frequency of f1 to fN
The number distribution width Δf is set to a predetermined time after injection of the contrast agent, for example, 2 minutes.
The interval is 0.0f₀After 2 minutes, 0.0f₀~ 0.4f₀of
It may be variably set within the range.

The unit waveform forming the first waveform or the second waveform may be a half cycle of a sine wave, one cycle or more. Conversely, it is also possible to use a chirp waveform whose frequency is continuously increased or decreased by making the cycle finer such as 1/4 cycle or 1/8 cycle. In the case of a chirp waveform, the start phase of the first irradiation waveform is practically different, but a chirp waveform whose amplitude gradually decreases from the start waveform toward the subsequent waveform, that is, an amplitude-stressed chirp waveform is suitable for the present invention. It is. According to this, the difference in the frequency spectrum of the contrast agent between the two irradiations can be further enhanced by increasing the first amplitude.

Further, the first waveform and the second waveform are set by a code f (A, θ) that defines the frequency f, the amplitude A, and the starting phase θ, and the first waveform is f1 (A1, θ1) <f2.
(A2, θ2) <... <fn (An, θn) <... <fN
(AN, θN) N continuous waveforms, A1 = A2 =... = An =.
.. = Θn =... = ΘN = 0 ° (or 180 °).
On the other hand, the second waveform is f1 ′ (A1 ′, θ1 ′)> f2 ′
(A2 ′, θ2 ′) >> ... fn ′ (An ′, θn ′)>
..> FN ′ (AN ′, θN ′) are made continuous by N waveforms, and the amplitude is A1 ′ = A2 ′ =.
In N ′, the phase is θ1 ′ = θ2 ′ =... = Θn ′ =.
It is preferable to set N ′ = 0 ° (or 180 °).
In other words, the first waveform and the second waveform may be configured such that the increasing and decreasing relationship of the frequency sequence is reversed, the starting phase is the same, and the amplitude is the same or different. In this case, the response signal subjected to the phasing processing is subtracted to attenuate the response signal of the living tissue. When the phases are made different, the response signal subjected to the phasing processing is added to attenuate the response signal of the living tissue.

When the start phase of the first waveform is set to 180 °, the waveform starts from the falling edge (negative side), so that the waveform is continuous from a low frequency f1 <fN, and conversely, the second waveform is started. When the phase is 0 °, the waveform starts from the rising edge (positive polarity side), so that the waveform is characterized by a continuous waveform from a high frequency fN ′> f1 ′. That is, since the bubbles of the contrast medium is irradiated with ultrasonic waves falling waveform starts deformed from the expanded, the frequency distribution of the response signal is shifted to a lower frequency side than the average frequency f _0. On the other hand, since the contrast medium when irradiated with ultrasonic waves in the rising waveform starts deform from a contracted, the frequency distribution of the response signal is shifted to a frequency side higher than the average frequency f _0. Therefore, such a setting has a special effect that the frequency distribution of the response signal of the contrast agent can be further broadened and the response signal component of the contrast agent can be further enhanced.

Also in the third feature, it is desirable that the pass band width of the filter is variably set in accordance with the first feature. Further, it is preferable to variably set according to the depth of the response signal or the sound pressure of the ultrasonic wave to be irradiated. For example, the bandpass width of the filter can be increased when the depth is shallow or in the initial time phase, and the bandpass width of the filter can be narrowed when the depth is deep or in the late time phase. (Fourth feature) In the third feature, the first waveform and the second waveform
A plurality of frequencies f1, f2, forming each of the waveforms;
, Characterized in that the response signal of the contrast agent is enhanced by gradually increasing or decreasing fN. On the other hand, the fourth feature further enhances the response signal of the contrast agent by making the amplitude A of at least the first half-wave of the first waveform and the second waveform larger than the amplitude of the subsequent waveforms. It is in.

The present inventors have found this feature by simulation and experiment and have explained that the contrast agent is considered to be a kind of resonator, although the physical background is not always clear. Cheap. That is, among the sound pressure waveforms applied to the contrast agent, it is considered that the frequency, phase, and amplitude of the start waveform determine the start response of the contrast agent,
The behavior of the contrast agent, once its response is defined by the starting waveform, tends to follow the response defined by the initial response even if the frequency, phase, and amplitude of the subsequent waveform change. Just once, a system that has begun to resonate at a certain frequency is usually difficult to respond to an input that deviates from the resonance frequency, but in the case of a contrast agent, this tendency is remarkable due to its nonlinearity. it can. A fourth feature of the present invention is to use this initial waveform dependency of the contrast agent response, in other words, the initial transient response dependency, to make the amplitude A of the first half-wave of the starting waveform larger than the amplitude of the subsequent waveform. By doing so, the contribution of the frequency component of the starting waveform is further emphasized.

Thus, the harmonic component contained in the response signal of the contrast agent can be emphasized more than the harmonic component contained in the response signal of the living tissue, and can be generated over a wide frequency band. That is, since the amplitude of the irradiation start waveform is increased, it is possible to further increase the response signal caused by the contrast agent, which is generated by the deformation accompanying the expansion and contraction of the contrast agent.

As a result, the signal component of the contrast agent is emphasized at a high rate, so that the signal component of the contrast image can be extracted and discriminated from the harmonics of the tissue. Improvement can be achieved.

More specifically, the first waveform and the second waveform are converted into a code f (A,
θ), and the first waveform is f1 (A1, θ1)
<F2 (A2, θ2) <... <fn (An, θn) <... <
fN (AN, θN) N waveforms are continuous and the amplitude is A
1> A2 >>...> An >>...> AN, and the phase is θ1 = θ2 =
.. = Θn = ... = θN = 180 °, and the second waveform is
f1 ′ (A1 ′, θ1 ′)> f2 ′ (A2 ′, θ2 ′)
>> fn '(An', θn ') >>fN' (A
N ′, θN ′), and the amplitude is A1 ′.
> A2 '>>...>An'>>...> AN 'and the phase θ1' =
.theta.2 '=... = .theta.n' =... = .theta.N '= 0.degree.

In the above description, the waveform of the ultrasonic signal supplied to the ultrasonic probe has been described, but the present invention is also valid for the waveform of the ultrasonic sound pressure applied to the contrast agent itself. That is, if the frequency response characteristic of a recent ultrasonic probe is at least 60% of the relative frequency band with respect to the center frequency,
It has been confirmed that the theory of the waveform of the ultrasonic signal directly applies to the theory of the acoustic waveform.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. The present invention is not limited by the embodiments described below. (First Embodiment) FIG. 1 shows an overall configuration diagram of an ultrasonic contrast imaging apparatus according to an embodiment to which the present invention is applied. This embodiment is suitable for implementing the third and fourth features of the present invention. That is, the ultrasonic signal is transmitted twice in the same direction of the ultrasonic beam at a time interval, and the response signal of the contrast agent is enhanced based on the response signals of the first and second ultrasonic signals. It is trying to get.

As shown in FIG. 1, an ultrasonic contrast drawing apparatus 1
Reference numeral 00 includes a probe 10, a wave transmitting unit 20, a wave receiving unit 30, an image creation display unit 40, and a system control unit 50. The transmitting unit 20 includes an arbitrary waveform generator 21 and a transmitting unit 23. The wave receiving unit 30 includes a wave receiver 31, a phasing adder 32, a line adder 33, and a band selection filter 34.
Consists of

The arbitrary waveform generator 21 of the transmitting unit 20 is configured as shown in FIG.
(A), the first waveform 61 shown in FIGS. 4 (A) and 5 (A),
It is formed so as to generate ultrasonic signals of 71, 81 and second waveforms 62, 72, 82. Arbitrary waveform generator 21
Is output from the broadband ultrasonic probe 1 via the transmitter 23.
0 is supplied. A power amplifier having a necessary number of channels corresponding to the array type ultrasonic probe 10 is provided in parallel at an output unit of the transmitter 23. Ultrasonic pulses mean frequency f ₀ In this way from the ultrasound probe 10 is irradiated to a living tissue. The ultrasound probe 10 receives the response signal from the contrast agent distributed in the living tissue and the response signal from the living tissue as a mixed signal.

The response signal received by the ultrasonic probe 10 is input to the receiver 31. The receiver 31 includes a pre-amplifier, a TGC amplifier, an A / D converter, and the like having a required number of channels. The receiver 31 amplifies an input response signal, converts the signal into a digital signal, and outputs the digital signal to the phasing adder 32. I do. The phasing adder 32 phasing and adding the response signals from a plurality of transducers related to one ultrasonic beam. A specific example of the phasing adder 32 is preferably a so-called digital beamformer in order to minimize the occurrence of distortion during the addition processing. This is because that does not generate unwanted harmonics 2f ₀ component by phasing addition process.

The response signal subjected to the phasing addition by the phasing adder 32 is sent to the line adder 33 by the system controller 5.
Based on the 0 command, two response signals corresponding to the two irradiations are added or subtracted and output to the bandpass filter 34. The bandwidth of the band-pass filter 34 can be variably adjusted as described later. For the adjustment of the band pass width, the band pass filter 34 is formed by a digital filter known as a digital FIR filter, and each coefficient sequence of the digital FIR filter is transmitted to the system controller 50.
Therefore, it can be realized by changing according to the depth or according to the ultrasonic sound pressure. As a digital filter, a third-order Chebyshoff-type filter is particularly suitable. The response signal having the frequency component selected and extracted by the band-pass filter 34 is sent to the image creation / display unit 40 as a signal due to the contrast agent, in common with or in parallel with the processing other than the contrast agent mode. The image creation display unit 40 performs processing including image processing such as normal detection and compression, Doppler processing such as color flow, and scan conversion processing.

The above-described processing operation is performed while scanning the direction of the ultrasonic beam as many times as necessary to cover a desired cross section or region of the living tissue. Then, the image is displayed on the display unit as image information such as the distribution of the contrast agent and the luminance as the size by the processing of the image creation display unit 40. The system control unit 50 controls the above series of operations.

Next, the characteristic operation of the embodiment shown in FIG. 1 will be described. In contrast agent mode imaging performed by injecting a contrast agent, for example, a B-mode tomographic image is captured and displayed on a display monitor, and the contrast mode image obtained by imaging in the contrast agent mode is converted to a normal B-mode image. Normally, they are displayed in an overlapping manner.

The normal B-mode image is picked up by the arbitrary waveform generator 21 based on a control command from the system controller 50.
, An ultrasonic signal having a single frequency of the fundamental frequency f ₀ is generated, subjected to transmission focus processing in the transmitter 23, amplified, supplied to the ultrasonic probe 10, and irradiated with the ultrasonic beam to the living body. It does by doing. After the response signal from the living body is amplified by the receiver 31 and converted into a digital signal, the phase of the response signal from the same part received by the plurality of transducers in the phasing adder 32 is matched. A response signal of a specific frequency component is selected and extracted by the bandpass filter 34 from the response signal for each of the phasing-added ultrasonic beams. For normal B-mode image capturing, the bandwidth of the band-pass filter 34 is adjusted to the band having a center frequency basic frequency f _0. Image creation display section 4
0 performs a detection process on the output of the band-pass filter 34 and performs image processing such as compression or scan conversion processing to create a two-dimensional image (B-mode image) of the living tissue and draw it on a display unit (display).

Next, imaging and drawing of a contrast agent mode image according to the features of the present invention will be described. The basic procedure and operation of imaging and drawing the contrast agent mode image are the same as those of the normal B mode image imaging. (When Realizing the Third Feature) The arbitrary waveform generator 21
The first waveform 61 or the second waveform 6 as shown in FIG.
It is configured to generate an ultrasonic signal having a two. The first waveform 61 and the second waveform 62 can be coded by frequency, starting phase and amplitude, as described later, and can generate an arbitrary waveform continuously from the coded one cycle waveform. Can be.

The arbitrary waveform generator 21 includes a system control unit 5
0 for the same ultrasonic beam direction by the control of FIG.
(A) Two ultrasonic signals of the first waveform 61 are generated at a time interval. The generated first ultrasonic signal is input to the ultrasonic probe 10 via the transmitter 23. On the other hand, the generated second ultrasonic signal becomes the second waveform 62 in FIG.
Is input to the ultrasonic probe 10 via the. When the arbitrary waveform generator 21 has a function of generating both the first waveform 61 and the second waveform 62, the configuration is such that both waveforms are selected by the data selector.

When the living body is irradiated with the ultrasonic signals of the first waveform 61 and the second waveform 62, two response signals corresponding thereto are input to the receiver 31. These two response signals are response signals for ultrasonic beams in the same direction, and are input with a time lag. The receiver 31 and the phasing adder 32 separately amplify the two response signals,
The signal is subjected to / D conversion and phasing addition processing, and is output to the line adder / subtractor 33 as a response signal (RF line signal) having phase information. The line adder / subtractor 33 performs RF addition considering the two response signals up to the phase, to obtain one response signal to be displayed (RF line signal).

As described above, in the response signal obtained by adding and subtracting the response signals of the two ultrasonic irradiations, the same component (linear component) included in the two response signals is attenuated, and the contrast agent or the tissue Are input to the band-pass filter 34. The pass band filter 34 has a configuration similar to that described in the embodiment of FIG. 1, and based on a command from the system control unit 50, a pass band width according to the depth of the response signal component and the time phase of the contrast agent. To enhance the response signal relating to the desired contrast agent.

The system controller 50 controls a series of operations related to the arbitrary waveform generator 21, the receiver 31, the phasing adder 32, the line adder / subtractor 33, and the band-pass filter 34. For example, the first waveform 61 and the second waveform 62 of the ultrasonic wave are issued to the arbitrary waveform generator 21 in accordance with a predetermined code.

Here, the first waveform 61 shown in FIG.
A simulation result will be described on the fact that if the contrast mode imaging is performed using the second waveform 62 and the second waveform 62, the response signal of the contrast agent can be effectively enhanced. In FIG. 3B, when the ultrasonic signal of the first waveform 61 in FIG. 3A is irradiated for the first time and the ultrasonic signal of the second waveform 62 in FIG.
7 shows an example of a frequency spectrum obtained by simulating a signal output from the line adder / subtractor 33. The horizontal axis in FIG. 7B is the frequency normalized by the fundamental frequency f ₀ , and the vertical axis is the normalized signal strength. Also, a line 63 in FIG. 7B is a frequency spectrum of the transmission ultrasonic wave, and a line 64 is a frequency spectrum of the response signal output from the line adder / subtracter 33.

In this simulation, the first waveform 61 of the first transmission has a frequency f1 in the first cycle.
(= 1.8 MHz), and the frequency is f
2 (= 2.2 MHz), and the average frequency f ₀ is 2
MHz. In addition, the second waveform 62 of the second transmission
Means that the frequency is f2 (= 2.2MHz) in the first cycle
In the next cycle, the frequency is f1 (= 1.8 MHz),
The average frequency _{f 0} was set to 2MHz. That is, the first waveform 61 and the second waveform 62 are the first waveform 6 of the first transmission.
The code “frequency f (amplitude A, phase θ)” of 1.8 is 1.8 MHz
z (1.0, 180 °) and 2.2 MHz (1.0, 180 °).
The code of the second waveform 62 of the second transmission is 2.2 MHz.
z (1.0, 0 °) and 1.8 MHz (1.0, 0 °). The frequency change width is 0.4 MHz and the amplitude change width is 0.0. Each waveform is given a Hanning weight in the direction of its time axis to resemble a waveform in a living body. In addition, the simulation calculates the diameter change of the contrast agent when a sound pressure waveform of MI = 0.7 is added to a contrast agent having a diameter of 2 microns by a differential equation governing the diameter change of the well-known contrast agent. The configuration is such that the radiation wave when the diameter change is regarded as a secondary sound source is observed at an observation point far from the contrast agent.

Here, the characteristics of the frequency spectrum of the response signal obtained by the present embodiment shown in FIG. 3B will be described in comparison with the frequency spectrum of the conventional double irradiation method. FIG. 6A shows a conventional ultrasonic transmission waveform, and FIG. 6B shows a frequency spectrum of a transmission signal and a response signal. The vertical and horizontal axes are the same as in FIG. In FIG. 6A, a first waveform 91 indicates a first transmission waveform, and a second waveform 92 indicates a second transmission waveform. Each of these frequencies has a fundamental frequency f ₀ = 2 MH
z. In FIG. 6B, a line 93 is the frequency spectrum of the transmitted ultrasonic wave, and a line 94 is the frequency spectrum of the response signal output from the line adder / subtracter 33.

The line 64 in FIG. 3B and the line 94 in FIG.
In contrast, in the prior art, the response signal component around the fundamental frequency f ₀ is greatly attenuated, and the harmonic component of the tissue around 2f ₀ is emphasized. It is suitable to a so-called tissue harmonic imaging (referred to as Tissue Harmonic Imaging), the response signal component of the contrast agent to be widely distributed over the f ₀ ~2f ₀ is rather attenuated. Above all,
Fundamental component f ₀ of the response signal of the contrast medium is markedly attenuated. Therefore, in the case of the conventional double irradiation method shown in FIG. 6, the response signal of the contrast agent is discriminated from the harmonics of the tissue,
The aim of highlighting cannot be fulfilled. This is a polar or time axis of the ultrasound signal waveform according to the prior art transmitted twice merely mutually inverted not only emphasize the harmonic components of the tissue response signal localized near 2f ₀ together, it is because significantly attenuate the fundamental wave component f ₀ of the contrast agent response signal distributed over a wide range.

[0048] However, according to FIG. 3 according to the invention (B), the area of the band around the discrimination ratio, 1.2f ₀ to 1.8F ₀ on the spectrum of the harmonic contrast agent response signal and the tissue response signal The ratio (energy ratio) is approximately 10dB to 20d
B.

[0049] Accordingly, signals obtained by the line adder 32, the time of the shallow part drawing, 0.8f ₀ to 2.5f
Since including the response signal of the contrast agent spread wide band of near _0, the pass bandwidth of the band-pass filter 34 is set to 0.8f ₀ to 2.5f _0, it is drawn as effect signal of the contrast agent. The same applies to normal contrast agent drawing where the sound pressure of the ultrasonic wave is MI = 0.2 to 0.7. On the other hand, when the sound pressure of the ultrasonic wave is a high MI value (for example, 1.3), 0.8f ₀
Or to 1.8f _0. It is also possible instead of a band elimination filter having a center frequency of 2f _0. In deep portion of the drawing, in order to attenuate the harmonics of tissue near 2f _0, and in order to reduce artifacts tissue fundamental wave by the body movement, it changes the bandwidth to 1.2f ₀ to 1.8F _0.

Although not shown, the frequencies f1 and f2 of the first waveform 61 and the second waveform 62 in FIG. 3A are interchanged, ie, the frequency f1 of the first code and the frequency f1 of the second code are replaced. Similar effects can be obtained even if the relationship of the frequency f2 is set to f1> f2.

As described above, in the first embodiment, each waveform of one cycle constituting an ultrasonic transmission waveform is coded by the frequency f, the amplitude A, and the start phase θ, and the waveforms are made continuous. I have. In particular, as shown in the waveform shown in FIG. 3A, the frequency of the first transmission cycle of the first waveform 61 and that of the second waveform 62 are made different from each other to emphasize the frequency of the ultrasonic transmission signal irradiated twice. It is characterized by. And thus the transmit signal frequency emphasis transmitted twice, adding processes the response signal, band stronger signal appears distribution spectrum centered at 2f ₀ of the response signal of the contrast agent (Fig. 6 ( B)), it has been found that a low frequency shift of the frequency spectrum occurs in the distribution where a strong signal appears in the band of 1.2f0 to 1.8 (FIG. 3B).

The reason why the spectrum of the response signal shifts to a low frequency is not always clearly understood because the contrast agent has a non-linear response. However, it can be considered as follows. First, the first waveform 61 has a starting phase of 18
Since it is 0 °, it starts from the fall (negative side). Conversely, the second waveform 62 starts from the rising edge (positive polarity side) since the start phase is 0 °. Here, because the bubbles of the contrast agent starts irradiation of ultrasonic waves falling waveform is started from the expansion, the frequency distribution of the response signal is considered to be shifted to a lower frequency side than the average frequency f _0. On the other hand, because the bubbles of the contrast medium to the start of the irradiation rising waveform is started from the contraction frequency distribution of the response signal is considered to be shifted to a frequency side higher than the average frequency f _0. Therefore, it is considered that the state of the non-linear response of the contrast agent changes depending on the relationship between the starting phase and the frequency of the first waveform 61 and the second waveform 62, and the frequency spectrum of the response signal changes. In other words, by making the frequency of the start waveform different from the frequency of the other waveforms that follow, the frequency spectrum of the contrast agent response signal obtained by the two irradiations is not the same, and the frequency distribution of the response signal of the contrast agent is changed. It is possible to enhance the response signal component of the contrast agent by further expanding.

In the above embodiment, the case where the ultrasonic wave is irradiated twice with a time interval described has been described. However, the present invention can be applied to the case where the ultrasonic wave is irradiated three or more times. That is, the arbitrary waveform generator 21 has a function of generating a plurality (M, where M ≧ 2 is a natural number) of ultrasonic signals of at least one cycle of a sine wave at a time interval in the same direction of the ultrasonic beam. Shall be. The generated ultrasonic signals are two types of ultrasonic signals of a first waveform and a second waveform that are symmetric with respect to the phase axis or the polarity. Then, the first waveform and the second waveform
The waveforms have frequencies f1, f2,..., Fn,.
It is assumed that there are a plurality of frequency components made up of N (where N ≧ 2 is a natural number) continuous waveforms. Then, the ultrasonic signal of the first waveform and the ultrasonic signal of the second waveform are alternately switched for each transmission and transmitted. In this case, the first
It is most preferred to equalize the average frequency f ₀ of the waveform and f1 to fN of the second waveform. Then, the frequency distribution width Δf of f1 to fN is set within a range of 0.0f ₀ to 0.4F _0. However, preferably practically from 0.1f ₀ to a range of 0.4F _0, further 0.2F ₀ to the circuit configuration for a range of 0.3f _0.

As a unit waveform forming the first waveform or the second waveform, a half cycle of a sine wave, one cycle or more can be used. Conversely, it is also possible to use a chirp waveform whose frequency is continuously increased or decreased by making the cycle finer such as 1/4 cycle or 1/8 cycle. In the case of a chirp waveform, the start phase of the first irradiation waveform is practically different, but a chirp waveform whose amplitude gradually decreases from the start waveform toward the subsequent waveform, that is, an amplitude-stressed chirp waveform is suitable for the present invention. It is. According to this, the difference in the frequency spectrum of the contrast agent between the two irradiations can be further enhanced by increasing the first amplitude.

Further, the first waveform and the second waveform are set by a code f (A, θ) which defines the frequency f, the amplitude A, and the starting phase θ, and the first waveform is f1 (A1, θ1) <f2.
(A2, θ2) <... <fn (An, θn) <... <fN
(AN, θN) N continuous waveforms, A1 = A2 =... = An =.
.. = Θn =... = ΘN = 180 °. On the other hand, the second waveform is f1 ′ (A1 ′, θ1 ′)> f2 ′ (A2 ′, θ
2 ′) >> fn ′ (An ′, θn ′) >> fN ′
(AN ′, θN ′) are made continuous by N waveforms. The amplitude is A1 ′ = A2 ′ =... An ′ =... = AN ′, and the phase is θ1 ′ = θ2 ′ =. .. = ΘN ′ = 0 °. In other words, the first waveform and the second waveform reverse the increase / decrease relationship of the frequency train, and the start phases have a 180 ° difference,
The amplitudes may be the same or different. In this case, the response signal subjected to the phasing processing is added to attenuate the response signal of the living tissue. The start phase may be the same. In this case, the response signal subjected to the phasing processing is subtracted to attenuate the response signal of the living tissue.

[0056] Further, it variably set to within a range of 0.0f ₀ to 0.4F ₀ in accordance with the frequency distribution width Δf and Δf of f1 to fN and f1 'to fN'', the depth of each ultrasound irradiation focused preferable. Also, instead of this, f1
To fN and f1 ′ to fN ′, the frequency distribution width Δf and Δ
The f ', the post-injection is 2 minutes 0.0f ₀ of the contrast agent, after 2 minutes can be variably set within a range of 0.0f ₀ to 0.4F _0.

For example, when N = 3, f1 = 1.
8 MHz, f2 = 2 MHz, and f3 = 2.2 MHz. Even if N = 4 or more, the gist of the present invention is not impaired. However, as the wave number increases, the difference between the waves relatively decreases, and thus it has been confirmed that a wave number of about N <6 is effective. The addition / subtraction process in the case of M ≧ 3 is performed, for example, by adding an odd-numbered response signal and adding or subtracting an even-numbered response signal in accordance with the polarity of the signal.
The response signal component of the contrast agent is extracted. (Case of Realizing the Fourth Feature) Here, another embodiment according to an ultrasonic contrast imaging apparatus that realizes the fourth feature of the present invention will be described. This embodiment can be realized by using the ultrasonic contrast imaging apparatus shown in FIG. For the third feature, only the function of the arbitrary waveform generator 21 is different. That is, the arbitrary waveform generator 21 generates the first waveform 71 and the second waveform 72 shown in FIG. 4A or the first waveform 81 and the second waveform 82 shown in FIG. Are different.
Other features are the same as those of the ultrasonic contrast imaging apparatus shown in FIG. 1, and therefore, different points will be mainly described.

4 (A) and FIG. 5 (A) are different from FIG. 3 (A) in that the amplitude of the waveform of the first cycle of the first waveform and the second waveform is smaller than the amplitude of the subsequent waveform. Is also set to be large. Note that FIGS. 4B and 5B
Is a simulation result similar to that of FIG.
Lines 73 and 83 are the frequency spectrum of the irradiated ultrasonic wave, line 7
Reference numerals 4 and 84 denote frequency spectra of the response signal subjected to the addition / subtraction processing.

The code f of the first waveform 71 in FIG.
(A, θ) are 1.7 MHz (1.1, 180 °) and 2.3 MHz, respectively.
z (0.8, 180 °) and the code f of the second waveform 72
(A, θ) are 2.3 MHz (1.1, 0 °) and 1.7 MHz, respectively.
(0.8, 0 °). That is, the frequency change width Δf is set to 0.6 MHz with respect to 0.4 MHz in FIG. 3, and the amplitude change width ΔA is set to 0.3 with respect to 0.0 in FIG.

According to the ultrasonic waveform of FIG. 4A, the reception spectrum of the response signal of the contrast agent obtained by adding the response signals corresponding to the two ultrasonic transmissions is apparent from FIG. 4B. such as, the further shift in the fundamental f ₀ closer. Although attenuation of harmonics 2f ₀ of the tissue slightly inferior, the distribution of the response signal obtained by adding, by detecting the response signal of the contrast medium distributed by shifting from 1.2f ₀ to 1.8F _0,
The contrast agent can be enhanced to attenuate tissue harmonics. Therefore, in a portion where the movement accompanying the respiration or pulsation of the tissue is not remarkable, the harmonic of the tissue is attenuated exclusively, and the discrimination ratio between the response signal of the contrast agent and the harmonic of the tissue can be further improved.

The code f of the first waveform 81 in FIG.
(A, θ) are 1.8 MHz (1.0, 180 °) and 2.2 MH, respectively.
z (0.9, 180 °) and the code f of the second waveform 82
(A, θ) are 2.2 MHz (1.0, 0 °) and 1.8 MHz, respectively.
(0.9, 0 °), their average frequency is 2 MHz in each case. That is, the frequency change width Δf is
The amplitude change width ΔA, which is the same as 0.4 MHz, is set to 0.1 with respect to 0.0 in FIG.

According to this, the harmonic 2f _{0 of the} tissue is further reduced as compared with FIG. 4 (A), so that the discrimination ratio between the response signal of the contrast agent and the harmonic of the tissue is further improved. Can be done. In the case of three irradiations, the amplitude change of each waveform may be A1 = 1.1, A2 = 1.0, and A3 = 0.9.

As described above, by adopting the waveforms shown in FIGS. 4A and 5A, the ultrasonic wave of the ultrasonic waveform in which the frequency and amplitude of the first one-cycle waveform are emphasized is obtained.
Irradiated twice by adding process these response signals, from the spectrum 2f ₀ vigor of the contrast agent response signal 1.
The low frequency shift of the frequency spectrum is caused from the band 2f ₀ to the band 1.8f ₀ . The reason for this frequency transition is that, as described above, the nonlinear response of the contrast agent differs depending on the relationship between the polarity and frequency of the waveform at the start of ultrasonic irradiation.
Therefore, it is understood that the frequency spectrum changes. In addition, it is believed that increasing the amplitude of the starting waveform enhances the difference in the non-linear response of the contrast agent. In other words, by making the frequency of the start waveform different from the frequency of the other sequential waveforms, the frequency spectrum of the contrast agent obtained by the two transmissions is not the same, and the amplitude of the start waveform is also different. The difference between the spectrums can be further emphasized by making them larger than the sequential waveform trains.

As described above, in the prior art, FIG.
The same waveform shown is simply irradiated twice with inverted polarity.
Even, 2f₀The components can be emphasized. However,
The cycle as shown in Fig. 3 (A), 4 (A) and 5 (A)
The frequency is different for each, especially the first cycle of the transmitted waveform
By changing the frequency of₀From 1.8f₀of
The signal is enhanced, and conversely 2f₀Can attenuate the ingredients
You. In particular, the amplitude of the first cycle of the
If you make it bigger than the descending, the frequency component of the first cycle
Can be emphasized. As a result, the
2 f₀To shift from the center to the low frequency region.
Therefore, it is possible to easily discriminate the harmonics of the tissue. Only
Also increase the frequency and amplitude of the first cycle of the transmitted waveform
Response signal to the low frequency region by changing the degree of
Can be controlled. (When implementing the first and second features) Use the embodiment of FIG.
Therefore, when realizing the first feature of the present invention, it is necessary to take an image of a tissue.
As with the image, a single fundamental frequency from the arbitrary waveform generator 21
f₀To generate an ultrasonic signal having
A desired part of the living body is scanned and irradiated. In addition,
As for the response signal, similarly to the imaging of the tissue, the imaging of the tissue is performed.
As in the case of, the receiver 31 and the phasing adder 32
Perform amplification and phasing. In this case, the line in Figure 1
The adder 33 is unnecessary. In other words, the response signal
Band-pass to extract the response signal caused by the contrast agent contained in the signal
The filter 34 is a characteristic element. That is, FIG.
As described above, the fundamental component 2a and the harmonic
Compared with the wave component 2b, the response signal 1 caused by the contrast agent has a higher signal.
Signal strength and exists over a wide frequency band.
You. The band pass width of the band pass filter 34 is increased,
Enhanced contrast agent response signal relative to tissue response signal
It is characterized by doing. In particular, the band-pass filter 34
The bandwidth is modulatable as in the following (A), (B) and (C)
It is preferable to adjust them. (A) Depending on the depth of the contrast agent distribution, for shallow sites,
0.8f₀~ 2.5f₀Adjust to 0.8f when deep₀No
1.8f₀, Preferably 1.2f₀~ 1.8f₀(Or
1.1f₀~ 1.8f₀). (B) In the initial phase after injection of the contrast agent,
Reduce the amplitude of the sound signal to the initial low sound pressure (MI = 0.4 to 0.7)
And And in the case of a shallow part, 0.8 as in (1)
f₀~ 2.5f₀Adjust to (C) In the late phase after injection of the contrast agent,
The amplitude of the sound wave signal is changed to high sound pressure in the latter period (MI = about 1.0 to 1.3)
, The bandwidth of the band-pass filter 34 is 0.8 f₀
~ 1.8f₀, Preferably 1.2f₀~ 1.8f₀(or
Is 1.1f₀~ 1.8f ₀).

That is, when the sound pressure is relatively weak,
In the case of the phase, the harmonic component 2f of the tissue ₀Can be ignored. So
Here, wide frequency band 0.8-2.5f₀Response signal over
By extracting, the response signal of the contrast agent is
Can be emphasized relatively compared to the issue. The depth
Is deep, the high-frequency component 2f of the tissue₀Becomes stronger,
0.8-2.5f₀Response signal over a wide range
Rather, the response signal of the contrast agent can be enhanced. On the other hand, late phase
In the case of a high sound pressure as shown in FIG.
₀Can not be ignored, so the bandwidth is 0.8-1.8f₀And then
Tissue harmonic component 2f₀Is eliminated or attenuated. This place
2f₀Reduction of harmonic components related to contrast agent distributed near
With weakness. However, imaging that is distributed over a wide frequency band
Since the response signal of the agent is extracted, there is no
You. Also, f₀Fundamental wave of response signal of nearby tissue
The components include components associated with the respiration and pulsation of the human body, and
If artifacts occur in the agent image,
1.2-1.8f₀(Or 1.1
f₀~ 1.8f₀) Is preferably set.

The switching of the bandwidth is controlled by the system controller 50 based on the set transmission focus or reception focus. For example, since the depth of the response signal corresponds to the time axis, the system control unit 50, band time position is shallower than the set depth range of the response signal passing the input to the filter 34, the bandwidth 0.8f ₀ to 2.5f to _0, a deep range switches in real time 1.2f ₀ to 1.8F _0.

[0067] By adjusting the bandwidth of the thus pass filter 34, it is possible to discriminate the harmonics included in the response signal of tissue harmonic 2f ₀ and contrast agents.
By detecting and drawing the contrast agent based on the harmonics of the response signal of the contrast agent extracted and extracted, it is possible to improve the SN ratio of the contrast image as compared with the related art. As the filter for attenuating harmonic components 2f _0, et bandpass filter 34, the center frequency can be used a band-elimination filter 2f _0. (In the case of realizing the second feature) In order to further enhance the effect of extracting the response signal component of the contrast agent by expanding the pass bandwidth of the band-pass filter 34 described above, the second
As described in the above feature, it is desirable to broaden the frequency of the ultrasonic wave applied to the contrast agent. That is, an ultrasonic signal generated by the arbitrary waveform generator 21 is, for example,
As shown in a waveform 61 in FIG.
And by the ultrasonic signal of mean frequency f _0, to a signal having a frequency component of a wide range. In FIG. 3A, a waveform 61 has a waveform in which one cycle of a sine wave of frequencies f ₁ and f ₂ is continuous, and the average frequency of those frequencies f ₁ and f ₂ is f ₀ . In the illustrated example, f ₁ <f ₂ is set. The average frequency f _0, selects the frequency appropriate to the tissue and device. In addition, as is well known, a known Hanning weight is applied in the time axis direction to resemble a waveform in a living body. By irradiating the living body with such an ultrasonic signal having a plurality of frequencies, the response signal of the contrast agent becomes strong over a wide band of the frequency spectrum. In other words, since the contrast agent has a distributed free resonance frequency corresponding to its particle size distribution, more contrast agents respond by distributing the frequency spectrum of irradiation ultrasonic waves over a wide band, and the contrast agent This is because the response signal itself is enhanced. Note that the response signal of the tissue remains unchanged around f ₀ and 2f ₀ . However, since the contrast agent response signal appears at a strong level over a wider frequency band, it is easier to discriminate between the tissue harmonics and the contrast agent harmonics.

Here, the absolute value of the difference between the frequencies f ₁ and f ₂ |
f ₁ −f ₂ |, that is, the distribution width Δf of the constituent frequencies is 0.0
selected within the range of f ₀ ~0.4f _0. Preferably, 0.1f ₀
0.40.4f _{0 is} good, and more preferably 0.2f ₀ 0.30.3f _0.
Is good. The arbitrary waveform generator 21 is not limited to the waveform having the _two frequencies f ₁ and f ₂ described above.
As described later, a waveform having N (≧ 2) frequencies can be applied.

[0069]

As described above, according to the present invention, the harmonic component contained in the response signal of the contrast agent is discriminated from the harmonic component contained in the response signal of the living tissue as a relatively strong signal. Since the extraction can be performed, the sharpness of the contrast agent drawing can be improved.

[Brief description of the drawings]

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

FIG. 2 is a graph illustrating the principle by which a contrast agent response signal of the present invention can be extracted at a high rate.

FIG. 3 is a graph showing an example of a transmission waveform of twice irradiation according to frequency emphasis according to an embodiment of the present invention, and a simulation result of a frequency spectrum of a transmission signal and an obtained response signal based on the transmission waveform.

FIG. 4 is a graph showing an example of a transmission waveform of double irradiation according to the frequency and amplitude emphasis of one embodiment of the present invention, and a simulation result of a frequency spectrum of a transmission signal and an obtained response signal based on the transmission waveform.

FIG. 5 is a graph showing another example of the transmission waveform of the double irradiation according to the frequency and amplitude emphasis of one embodiment of the present invention, and a simulation result of a frequency spectrum of a transmission signal and an obtained response signal based on the transmission waveform. is there.

FIG. 6 is a graph showing, for comparison, a transmission waveform of twice irradiation according to the related art, and a simulation result of a frequency spectrum of a transmission signal and an obtained response signal by the transmission waveform.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ultrasonic probe 20 Transmitting part 21 Arbitrary waveform generator 23 Transmitter 30 Receiving part 31 Receiver 32 Phasing adder 33 Line adder 34 Bandpass filter 40 Image creation display part 50 System control parts 61, 71, 81 First waveform 62, 72, 82 Second waveform 63, 73, 83 Transmission signal spectrum 64, 74, 84 Response signal spectrum

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Minoru Yoshida, 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Medical Corporation (72) Inventor Takeshi Takeshi 1-1-1, Uchikanda, Chiyoda-ku, Tokyo No. 14 F-term in Hitachi Medical Corporation (reference) 4C301 DD01 DD11 EE11 HH01 HH11 JB29 JB38

Claims (8)

[Claims] An ultrasonic probe for transmitting and receiving ultrasonic waves to and from a living body, a transmitting unit for transmitting an ultrasonic signal to the ultrasonic probe, and an ultrasonic probe received by the ultrasonic probe A receiving unit that processes a response signal of a sound wave; and a drawing unit that creates a tomographic image of the living body based on the response signal processed by the receiving unit. It has a function of transmitting a plurality of times (M, where M is a natural number of 2 or more) times with a time interval in the direction, and each ultrasonic signal consists of continuations of waveforms having different frequencies, and at least the amplitude of the leading waveform is continuous. And the signals of each time are set to be asymmetric with respect to the polarity inversion and the time axis inversion, and the receiving unit performs a phasing process on the response signals of the plurality (M) of the ultrasonic signals. Function and the phasing response signal Or subtraction processing becomes a function to attenuate the response signal of the living body tissue ultrasound contrast rendering device. 2. The ultrasonic contrast imaging apparatus according to claim 1, wherein the waveforms having different frequencies are cycle waveforms having inverted polarities and equal frequencies. 3. An ultrasonic probe for transmitting and receiving ultrasonic waves to and from a living body, a transmitting unit for transmitting an ultrasonic signal to the ultrasonic probe, and an ultrasonic probe received by the ultrasonic probe. A receiving unit that processes a response signal of a sound wave; and a drawing unit that creates a tomographic image of the living body based on the response signal processed by the receiving unit. It has a function of transmitting a plurality of times (M, where M ≧ 2 is a natural number) with a time interval in the direction, and the frequency of each ultrasonic signal is f1, f2,.
n, ..., fN (where natural number N ≧ 2) is the average frequency f ₀ of the signal formed by successive N pieces of waveform of the f1
To the frequency distribution width Δf of fN is set within a range of 0.0f ₀ to 0.4F _0, and at least the amplitude of the first waveform is greater than the amplitude of the waveform group to continue, and each time the signal that is the polarity inversion and the time axis The receiver is configured to be asymmetric with respect to inversion, and the receiving unit performs a phasing process on the response signals of the plurality of (M) ultrasonic signals, and adds or subtracts the phasing-processed response signals. And a function of attenuating the response signal of the living tissue. 4. The waveform of each time is set by a code f (A, θ) which defines a frequency f, an amplitude A, and a start phase θ, and f1 (A1, θ1) <f2 (A2, θ2) <. <Fn
(An, θn) <... N waveforms of fN (AN, θN) are continuous, and the amplitudes are A1>A2>.
In the AN, the phase is θ1 = θ2 =... = Θn =.
The first waveform is set to 0 °, and f1 ′ (A1 ′, θ1 ′)> f2 ′ (A2 ′, θ2 ′)
>> fn '(An', θn ') >>fN' (A
N ′, θN ′) are continuous, the amplitude is A1 ′> A2 ′ >>... An ′ >>.
3. The ultrasonic contrast imaging apparatus according to claim 2, wherein the second waveform is set to 1 ′ = θ2 ′ =... = Θn ′ =. 5. The receiving section has a filter for extracting a specific frequency component from the response signal in which the response signal of the living tissue is attenuated, and the pass band of the filter is equal to the average frequency f _0. ultrasound contrast drawing apparatus according to any one of claims 1 to 4, characterized by being set to 0.8f ₀ to 1.8F ₀ as a reference. 6. The receiving section has a filter for extracting a specific frequency component from the response signal in which the response signal of the living tissue is attenuated, and the pass band width of the filter is equal to the average frequency f _0. ultrasound contrast drawing apparatus according to any one of claims 1 to 4, characterized by being set to 1.2f ₀ to 1.8F ₀ as a reference. 7. The receiving section has a filter for extracting a specific frequency component from the response signal in which the response signal of the living tissue is attenuated, and the pass bandwidth of the filter is equal to the average frequency f _0. the in the range of 0.8f ₀ to 1.8F ₀ as a reference, the ultrasound contrast drawing apparatus according to any one of claims 1 to 4, characterized in that it is variably set in accordance with the depth of the response signal. 8. An ultrasonic probe for transmitting and receiving ultrasonic waves to and from a living body, a transmitting unit for transmitting an ultrasonic signal to the ultrasonic probe, and an ultrasonic probe received by the ultrasonic probe. A receiving unit that processes a response signal of a sound wave; and a drawing unit that creates a tomographic image of the living body based on the response signal processed by the receiving unit. Has a function of transmitting a plurality of times (M, where M is a natural number of M ≧ 2) times with a time interval in the direction, and each ultrasonic signal is composed of a half wave group having a different frequency component, and at least the first half wave The amplitude is greater than the amplitude of the subsequent half-wave group, and those half-wave groups are set asymmetrically with respect to the phase axis or the polarity. The reception unit adjusts the response signal of the plurality (M) of ultrasonic signals. A phase processing function, and an addition or subtraction processing of the phasing-processed response signal. And a function of attenuating the response signal of the living tissue.