JP3831097B2 - Ultrasonic imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic imaging method and apparatus, and a micro baloon destruction method, and more particularly to an ultrasonic imaging method and apparatus for a subject injected with a microballoon contrast agent, and a microballoon injected into a subject. It relates to the destruction method.
[0002]
[Prior art]
In ultrasonic imaging using a contrast agent, a microballoon contrast agent in which a large number of microballoons having a diameter of 1 to several μm are mixed in a liquid is used. A microballoon is formed by sealing a gas that is harmless to a living body in a shell that is harmless to the living body and is capable of degrading with time. Such a microballoon generates a characteristic harmonic echo such as a second harmonic, for example, due to the non-linear echo source. The distribution of the agent is imaged.
[0003]
In contrast imaging using a microballoon contrast agent, an ultrasonic wave that does not destroy the shell of the microballoon is transmitted, a non-destructive mode (mode) that generates an image based on the second harmonic echo, and a shell of the microballoon There is a destructive mode in which an ultrasonic wave to be broken is transmitted and an image is generated by using subharmonics echo generated when the shell is broken.
[0004]
[Problems to be solved by the invention]
Due to the nonlinearity of the ultrasound transmission / reception system and the nonlinearity of ultrasound propagation in the subject, second harmonic components and the like are inevitably included in echoes from the body tissue that does not contain the microballoon contrast agent. In this book, this phenomenon is called leakage of the spectrum from the fundamental wave (prectrum). Due to the leakage of the spectrum, when an image is generated from the second harmonic echo, the tissue image is also imaged together, which makes it difficult to identify the contrast agent image.
[0005]
Further, when imaging is performed in the destruction mode, bubbles are released from the destroyed shell of the microballoon. These bubbles do not disappear instantaneously, but continue to exist in the body for a certain period of time until they dissolve and disappear in blood or the like. Therefore, although this bubble can also be used as a contrast agent, conventionally, there is no idea of using this for contrast, and only waiting for the disappearance of the bubble.
[0006]
When imaging in the destruction mode, it is necessary to raise the sound pressure of the transmitted ultrasonic wave to a level that is sufficient to destroy the shell of the microballoon. It is desirable to destroy it.
[0007]
The present invention has been made to solve the above-described problems, and an object thereof is to realize an ultrasonic imaging method and apparatus for effectively performing microballoon contrast imaging. It is another object of the present invention to realize an ultrasonic imaging method and apparatus for performing contrast imaging using bubbles generated after destruction of a microballoon shell. Furthermore, it aims at realizing the microballoon destruction method which destroys a microballoon efficiently.
[0008]
[Means for Solving the Problems]
(1) A first invention for solving the above-described problem is an ultrasonic imaging method for generating an image based on a harmonic echo by transmitting an ultrasonic wave to a subject injected with a microballoon contrast agent, A harmonic echo obtained in a state in which the microballoon contrast agent is injected into the subject by obtaining a leakage component of the harmonic echo contained in the echo obtained in a state where the microballoon contrast agent is not injected into the subject. The leakage component is subtracted from the image and an image is generated based on the harmonic echo after the subtraction.
[0009]
(2) A second invention for solving the above-mentioned problem is an ultrasonic imaging method for generating an image based on an echo by transmitting an ultrasonic wave to a subject injected with a microballoon contrast agent, wherein the microballoon A first ultrasonic wave having a sound pressure that destroys the shell of the microballoon in the contrast agent is transmitted, a second ultrasonic wave is transmitted at a time interval from the transmission of the first ultrasonic wave, and the first ultrasonic wave is transmitted. An image is generated based on an echo with respect to two ultrasonic waves.
[0010]
(3) A third invention for solving the above-described problem is an ultrasonic imaging in which a subject into which a microballoon contrast agent is injected is scanned in an acoustic ray sequence with an ultrasonic beam and an image is generated based on echoes on each acoustic ray. The method has a beam width straddling at least three adjacent sound rays, and a sound pressure sufficient to break a microballoon shell in the microballoon contrast medium on the central sound ray, In the sound ray, an ultrasonic wave having a beam profile having a sound pressure that is insufficient to destroy the shell of the microballoon is transmitted, and the sound ray is sequentially scanned when viewed from the central ray among the sound rays on both sides. An echo is received along a sound ray on the side opposite to the direction, and an image is generated based on the echo.
[0011]
(4) A fourth invention that solves the above-described problem is a transmitter / receiver that transmits an ultrasonic wave to a subject and receives an echo thereof, and the transmitter / receiver that does not inject a microballoon contrast agent into the subject. Calculation means for calculating a leakage component of the harmonic echo contained in the obtained echo, and subtraction for subtracting the leakage component from the harmonic echo obtained by the transmission / reception means in a state where a microballoon contrast agent is injected into the subject. And image generation means for generating an image based on the harmonic echo after the subtraction.
[0012]
(5) According to a fifth invention for solving the above-described problem, a first ultrasonic wave having a sound pressure that destroys a shell of the microballoon in the microballoon contrast agent is transmitted to a subject injected with the microballoon contrast agent. And transmitting means for transmitting the second ultrasonic wave at a time from the transmission of the first ultrasonic wave, receiving means for receiving the echo for the second ultrasonic wave, and the received echo And an image generation means for generating an image based on the image.
[0013]
(6) A sixth invention that solves the above-described problem is an ultrasonic imaging that scans a subject into which a microballoon contrast agent is injected in an acoustic beam sequentially with an acoustic beam and generates an image based on an echo on each acoustic ray. The device has a beam width extending over at least three adjacent sound rays, and has a sound pressure sufficient to destroy the shell of the microballoon in the microballoon contrast medium on the central sound ray, and the sound on both sides. A transmitting means for transmitting an ultrasonic wave having a beam profile that is insufficient to destroy the shell of the microballoon, and the sound ray as viewed from the central sound ray among the sound rays on both sides. It is characterized by comprising receiving means for receiving an echo along a sound ray on the opposite side to the sequential scanning direction, and image generating means for generating an image based on the received echo.
[0014]
(7) A seventh invention for solving the above-described problem is characterized in that an ultrasonic wave having a negative pressure in the first half cycle is transmitted to a subject into which a microballoon has been injected.
In the first invention or the fourth invention, the leakage component into the frequency domain of the harmonic echo means the leakage of the spectrum from the fundamental wave.
[0015]
In the first invention or the fourth invention, it is preferable that subtraction of the leakage component from the harmonic echo is performed between frequency domain signals subjected to Fourier transform in terms of performing contrast imaging with good real-time characteristics.
[0016]
In the second invention or the fifth invention, the first ultrasonic wave is preferably negative in the first half cycle from the viewpoint of efficiently destroying the shell of the microballoon.
In the second or fifth aspect of the invention, the first ultrasonic wave includes a plurality of sound rays for imaging within the cross section of the beam, thereby increasing the efficiency of breaking the microballoon shell. This is preferable.
[0017]
3rd invention or 6th invention WHEREIN: Echo is received along the sound ray in the scanning direction side of the said sound ray sequential seeing from the said center sound ray, and producing | generating an image based on it receives a micro, This is preferable in that an image before the destruction of the balloon shell is obtained.
[0018]
In the seventh invention, it is preferable that the waveform of the ultrasonic wave ends in one cycle from the viewpoint of increasing the destruction efficiency of the shell of the microballoon.
(Function)
In the first invention or the fourth invention, the harmonic echo that does not depend on the microballoon contrast agent is removed by subtracting the signal.
[0019]
In the second invention or the fifth invention, an image is taken after the state of bubbles released from the shell is settled by taking a time between the destruction of the shell of the microballoon and the ultrasonic imaging.
[0020]
In the third invention or the sixth invention, the region through which the acoustic ray for echo reception passes is the region in which the center of the transmitted ultrasonic beam has passed one acoustic ray and the shell of the microballoon has been destroyed.
[0021]
In the seventh invention, the microballoon is efficiently destroyed by applying ultrasonic waves starting from negative pressure.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.
[0023]
FIG. 1 shows a block diagram of an ultrasonic imaging apparatus. This apparatus is an example of an embodiment of an ultrasonic imaging apparatus of the present invention. An example of an embodiment of the apparatus of the present invention is shown by the configuration of the apparatus. An example of an embodiment of the method of the present invention is shown by the operation of the apparatus.
[0024]
(Constitution)
The configuration of this apparatus will be described. As shown in FIG. 1, the apparatus has an ultrasonic probe 2. The ultrasonic probe 2 has, for example, an ultrasonic transducer array (not shown) formed along an arc projecting forward. That is, the ultrasonic probe 2 is a convex probe. The ultrasonic probe 2 is used in contact with the subject 4 by the operator. A microballoon contrast agent 40 is injected into the subject 4.
[0025]
The ultrasonic probe 2 is connected to the transmission / reception unit 6. The transmission / reception unit 6 gives a drive signal to the ultrasonic probe 2 to transmit ultrasonic waves into the subject 4. The transmitter / receiver 6 also receives an echo from the subject 4 received by the ultrasonic probe 2. The ultrasonic probe 2 and the transmission / reception unit 6 are an example of an embodiment of the transmission / reception means in the present invention. Moreover, it is an example of embodiment of the wave transmission means in this invention. Moreover, it is an example of embodiment of the receiving means in this invention.
[0026]
A block diagram of the transceiver 6 is shown in FIG. In the figure, a transmission timing (timing) generation circuit 602 periodically generates a transmission timing signal and inputs it to a transmission beam former (beam former) 604.
[0027]
The transmission beamformer 604 is based on the transmission timing signal, and transmits a beam forming signal, that is, a plurality of drives that drive a plurality of ultrasonic transducers (transducers) in the ultrasonic transducer array with a time difference. A signal is generated and input to the transmission / reception switching circuit 606. The drive signal has variable amplitude and waveform.
[0028]
The transmission / reception switching circuit 606 inputs a plurality of drive signals to a selector 608. The selector 608 selects a plurality of ultrasonic transducers that form a transmission aperture from the ultrasonic transducer array, and gives a plurality of drive signals to them.
[0029]
The plurality of ultrasonic transducers respectively generate a plurality of ultrasonic waves having a phase difference corresponding to the time difference between the plurality of drive signals. An ultrasonic beam is formed by wavefront synthesis of these ultrasonic waves. The transmission direction of the ultrasonic beam is determined by the transmission aperture selected by the selector 608.
[0030]
Transmission of the ultrasonic beam is repeatedly performed at predetermined time intervals by a transmission timing signal generated by the transmission timing generation circuit 602. The transmission direction of the ultrasonic beam is sequentially changed by switching the transmission aperture with the selector 608. As a result, the inside of the subject 4 is scanned by sound rays formed by the ultrasonic beam. That is, the inside of the subject 4 is scanned in a sound ray sequence.
[0031]
The selector 608 also selects a plurality of ultrasonic transducers that form reception apertures from the array of ultrasonic transducers, and inputs a plurality of echo signals received by the ultrasonic transducers to the transmission / reception switching circuit 606. It has become.
[0032]
The transmission / reception switching circuit 606 is configured to input a plurality of echo signals to the reception beam former 610. The received beam former 610 adjusts the phase by giving a time difference to a plurality of echo signals, and then adds them to form a received beam forming, that is, an echo received signal on the received sound ray. . The selector 608 scans the received sound ray in accordance with the transmission.
[0033]
The transmission timing generation circuit 602 through the reception beamformer 610 described above are controlled by the control unit 18 described later.
For example, scanning as shown in FIG. 3 is performed by the ultrasonic probe 2 and the transmission / reception unit 6. That is, as shown in the figure, the sound ray 202 emitted from the radiation point 200 moves on the arc 204, whereby the fan-shaped two-dimensional region 206 is scanned in the θ direction, and so-called convex scan is performed. Is called. When the sound ray 202 is extended in a direction opposite to the ultrasonic wave transmission direction (z direction), all the sound rays intersect at one point 208. A point 208 is a divergence point of all sound rays.
[0034]
The transmission / reception unit 6 is connected to a B-mode processing unit 10 and inputs an echo reception signal for each sound ray to the B-mode processing unit 10. The B-mode processing unit 10 forms B-mode image data (data). As shown in FIG. 4, the B-mode processing unit 10 includes a fundamental wave processing unit 110 and a harmonic processing unit 112, and an output signal of the receiving beam former 610 is input to them.
[0035]
The fundamental wave processing unit 110 performs logarithmic amplification and envelope detection on a signal having a frequency corresponding to the fundamental wave of the transmitted ultrasonic wave for the input signal, and indicates the echo intensity at each reflection point on the sound ray. That is, an A scope signal is obtained, and B-mode image data is formed using the instantaneous amplitude of the A scope signal as a luminance value. That is, the fundamental wave processing unit 110 generates image data based on the fundamental wave echo.
[0036]
The harmonic processing unit 112 performs a logarithmic amplification and envelope detection on a signal corresponding to the harmonic of the transmitted ultrasonic wave with respect to the input signal, that is, a signal representing the intensity of the echo at each reflection point on the sound ray, that is, A A scope signal is obtained, and B-mode image data is formed by using the instantaneous amplitude of the A scope signal as a luminance value. That is, the harmonic processing unit 112 generates image data based on the harmonic echo.
[0037]
The harmonic echo is mainly a second harmonic echo. Not limited to this, other order harmonic echoes included in the echoes of the microballoon contrast agent may be used. The harmonic processing unit 112 will be described later.
[0038]
The B mode processing unit 10 is connected to the image processing unit 14. The B-mode processing unit 10 and the image processing unit 14 are an example of an embodiment of image generation means in the present invention. The image processing unit 14 generates a B-mode image based on data input from the B-mode processing unit 10.
[0039]
As shown in FIG. 5, the image processing unit 14 includes a sound ray data memory 142, a digital scan converter 144, an image memory 146, and an image processing processor connected by a bus 140. (prosessor) 148 is provided.
[0040]
The B-mode image data input for each sound ray from the B-mode processing unit 10 is stored in the sound ray data memory 142, respectively. A sound ray data space is formed in the sound ray data memory 142.
[0041]
The digital scan converter 144 converts sound ray data space data into physical space data by scan conversion. The image data converted by the digital scan converter 144 is stored in the image memory 146. That is, the image memory 146 stores physical space image data. The image processor 148 performs predetermined data processing on the data in the sound ray data memory 142 and the image memory 146, respectively.
[0042]
A display unit 16 is connected to the image processing unit 14. The display unit 16 receives an image signal from the image processing unit 14 and displays an image based on the image signal. The display unit 16 can display a color image.
[0043]
The transmission / reception unit 6, the B-mode processing unit 10, the image processing unit 14, and the display unit 16 are connected to the control unit 18. The control unit 18 gives control signals to these units to control their operations. In addition, various notification signals are input to the control unit 18 from each part to be controlled. Ultrasonic imaging is performed under the control of the control unit 18.
[0044]
An operation unit 20 is connected to the control unit 18. The operation unit 20 is operated by an operator, and inputs desired commands and information to the control unit 18. The operation unit 20 includes, for example, an operation panel (panel) provided with a keyboard and other operation tools.
[0045]
FIG. 6 shows a block diagram of the main part of the harmonic processing unit 112. As shown in the figure, the harmonic processing unit 112 includes a range gate unit 114, which performs range gate on an input signal and inputs the input signal to an FFT (fast fourie transform) unit 116.
[0046]
The FFT unit 116 performs FFT processing, that is, Fourier transform on the input signal to convert a time domain signal into a frequency domain signal, and outputs the output signal to the coefficient calculation unit 120 or the spectrum simulation through the switching unit 118. A (sprectrum simulation) section 122 is selectively input. The spectrum simulation unit 122 is an example of an embodiment of calculation means in the present invention. An input signal to the spectrum simulation unit 122 is also input to the subtraction unit 124 in common. The subtraction unit 124 is an example of an embodiment of a subtraction unit in the present invention.
[0047]
The subtraction unit 124 subtracts the output signal of the spectrum simulation unit 122 from the output signal of the FFT unit 116 and inputs the result to an iFFT (inverse fast fourie transform) unit 126. The iFFT unit 126 performs iFFT processing on the output signal of the subtraction unit 124 to return the frequency domain signal to a time domain signal.
[0048]
The coefficient calculation unit 120 is configured to obtain a coefficient representing spectrum leakage from the fundamental wave based on an input signal given through the switching unit 120. This coefficient is obtained from the FFT result of echoes obtained by scanning the subject 4 with ultrasonic waves without injecting the microballoon contrast agent 40. The magnitude of the coefficient corresponds to the magnitude of spectrum leakage.
[0049]
That is, the echo signal of the section gated by the range gate unit 114 is subjected to FFT processing by the FFT unit 116 to obtain a frequency spectrum, and from this frequency spectrum, the coefficient calculation unit 120 uses the harmonics, that is, the leakage spectrum from the fundamental wave. A coefficient sequence representing the component ratio of each component is obtained. This is performed for all sections on the sound ray, and for all sound lines in the scanning range. The coefficient sequence obtained in this way is given to the spectrum simulation unit 122.
[0050]
The spectrum simulation unit 122 simulates spectrum leakage from the fundamental wave based on a signal input from the FFT unit 116 through the switching unit 120 during contrast imaging.
[0051]
That is, at the time of contrast imaging performed by injecting the microballoon contrast medium 40 into the subject 4, the echo signal of the section gated by the range gate unit 114 is FFT processed by the FFT unit 116 to obtain a frequency spectrum, and this frequency spectrum is obtained. Based on the coefficient sequence, the spectrum simulation unit 122 generates a spectrum leakage from the fundamental wave by simulation. As the coefficient sequence, the sound ray and the range gate section corresponding to those of the input signal are used.
[0052]
The leakage spectrum generated in this manner is subtracted from the output signal of the FFT unit 116 by the subtraction unit 124, thereby obtaining a harmonic spectrum that does not include the leakage spectrum. As a result, a harmonic signal not including a leakage spectrum is obtained from the iFFT unit 126 as a time domain signal. This is performed for all sections on the sound ray, and for all sound lines in the scanning range.
[0053]
The above FFT unit 116 to iFFT unit 124 are configured using, for example, a computer.
(Operation)
The operation of this apparatus will be described. The operator contacts the ultrasonic probe 2 with a desired location of the subject 4 and operates the operation unit 20 to perform imaging. Imaging is performed under the control of the control unit 18.
[0054]
Prior to imaging, the operator performs a pre-scan with ultrasound for the contrast imaging scheduled range without injecting the microballoon contrast medium 40 into the subject 4, and based on the echo signal, the coefficient calculation unit 120 performs the above-described coefficient. Perform the calculation. Thereafter, the microballoon contrast agent 40 is injected into the subject 4 and contrast imaging is started.
[0055]
First, contrast imaging in the nondestructive mode will be described. The transmitter / receiver 6 scans the inside of the subject 4 in the order of sound rays through the ultrasonic probe 2 and receives the echoes one by one. The ultrasonic wave transmission level is set so as not to destroy the shell of the microballoon. When the sound ray scans the injection site of the microballoon contrast agent 40, the echo includes a harmonic echo from the microballoon contrast agent 40 in addition to the fundamental wave echo from the body tissue. The main component of the harmonic echo is the second harmonic echo. A signal in which these echoes are mixed is input from the transmission / reception unit 6 to the B-mode processing unit 10.
[0056]
In the B mode processing unit 10, the fundamental wave processing unit 110 forms B mode image data based on the fundamental wave echo. The harmonic processing unit 112 forms B-mode image data based on the harmonic echo. Since the harmonic processing unit 112 generates B-mode image data based on the harmonic echo excluding the spectrum leakage from the fundamental wave by the functions of the spectrum simulation unit 122 and the subtraction unit 124, only the microballoon contrast agent 40 is used. The image data shown is obtained.
[0057]
Removal of spectrum leakage by the spectrum simulation unit 122 and the subtraction unit 124 is performed at high speed, and the image data of the microballoon contrast agent 40 is obtained in real time with sound ray scanning.
[0058]
These image data are respectively stored in the sound ray data memory 142 of the image processing unit 14. As a result, two sound ray data spaces for the B-mode image data are formed in the sound ray data memory 142.
[0059]
The image processor 148 scans and converts the two B-mode image data in the sound ray data memory 142 by the digital scan converter 144 and writes the B-mode image data in the image memory 146.
[0060]
The image processor 148 writes the two B-mode images in different areas. The B-mode image by the fundamental wave echo shows a tomographic image of the body tissue on the scanning plane. The B-mode image by harmonic echo shows the location of the microballoon contrast agent 40 on the scanning plane.
[0061]
The operator operates the operation unit 20 to display these B-mode images on the display unit 16. That is, for example, as shown in FIG. 7, a composite image of a tissue tomographic image 160 and a harmonic echo image 162 is displayed. The tissue tomographic image 160 and the harmonic echo image 162 are displayed in different display colors. Thereby, a contrast agent image with a clear positional relationship to the tissue can be obtained.
[0062]
Next, imaging in the destructive mode will be described. In the present invention, the microballoon shell is broken to release bubbles, and contrast imaging is performed using the bubbles as a harmonic echo source. Bubbles released from the shell do not disappear instantaneously, but continue to exist in the body for a certain period of time until they dissolve and disappear in blood. Therefore, this bubble can also be used as a kind of contrast agent.
[0063]
First, an ultrasonic wave for breaking the microballoon shell is transmitted. As such an ultrasonic wave, as shown in FIG. 8A, an ultrasonic wave having a negative pressure in the first half cycle is used. Such ultrasonic waves are generated, for example, by a drive signal or the like in which the first half cycle is negative.
[0064]
When such ultrasonic waves are applied to the microballoon, the shell is destroyed by a cavitation effect due to negative pressure. In particular, due to nonlinearity of ultrasonic propagation, for example, as shown in FIG. 8B, the sound pressure waveform tends to have a negative period extending as it progresses. The extension of the negative period lengthens the application time of the negative pressure and acts more favorably on the destruction. For this reason, the shell can be broken even with a relatively low sound pressure, and the efficiency is good. In addition, it is advantageous that the positive part of the sound pressure waveform becomes steep in that the destruction is accelerated.
[0065]
Note that the sound pressure waveform ends in this positive cycle and there is no waveform after that, or the waveform is as small as possible as shown by the broken line in FIG. It is preferable at the point extended to. In addition, using such an ultrasonic wave, it is possible to destroy not only a microballoon as a contrast agent but also a microballoon or a microcapsule encapsulating a drug or the like in a subject. .
[0066]
On the other hand, as shown in FIG. 9 (a), when a positive ultrasonic wave is used in the first half cycle, even if there is a non-linearity of propagation, it is positive as shown in FIG. 9 (b). However, the distance between them does not change, and therefore the period of negative pressure does not increase. Therefore, the effect of destroying the shell of the microballoon is inferior to that of FIG. Therefore, when the first half cycle uses a positive ultrasonic wave, it is necessary to increase the sound pressure level of the transmitted ultrasonic wave so as to obtain a sufficient destruction effect.
[0067]
Ultrasonic waves as shown in FIG. 8A are transmitted by the transmission / reception unit 6 to break the shell of the microballoon, and contrast imaging is performed using the emitted bubbles. Needless to say, ultrasonic waves as shown in FIG. 9A may be used to destroy the shell of the microballoon.
[0068]
The present inventor has found that when imaging is performed in the destructive mode, it is better to use the echo of the ultrasonic wave transmitted after that than the ultrasonic echo used to destroy the shell. .
[0069]
This is presumably because it takes a certain amount of time for the state of the released bubbles to settle (settling) after the shell is broken. Therefore, the transmission / reception unit 6 transmits / receives ultrasonic waves in the following sequence. Hereinafter, the destruction of the shell of the microballoon is simply referred to as the destruction of the microballoon.
[0070]
FIG. 10 schematically shows an ultrasonic transmission / reception sequence. As shown in the figure, in the first period 30, ultrasonic waves for breaking the microballoon are transmitted. The ultrasonic wave for breaking the microballoon is an example of an embodiment of the first ultrasonic wave in the present invention. For example, this ultrasonic wave has a sound pressure of 0.5 MPa or more, a frequency of 0.5 to 1 MHz, and a transmission time of 1 to several μS. As the driving waveform for transmission, it is advantageous to use the one shown in FIG. Of course, the configuration shown in FIG. 9A may be used. In addition, the adjustment of the thickness of the ultrasonic beam or the scanning range is adjusted so that the destruction range becomes a desired range.
[0071]
Next, in period 32, transmission and reception of ultrasonic waves are stopped, and a waiting state is entered. The waiting time is set to, for example, several μS to several mS in accordance with the progress speed of the destruction according to the type of the microballoon. During this time, the destruction of the microballoon is completed and the state of the bubbles released from the shell is settled.
[0072]
The effect of putting such a waiting time is in addition to settling of the released bubbles, and in the meantime, miscellaneous echoes generated by the ultrasonic waves for destruction disappear, and the voltage for driving the vibrator is used for breaking. There is also a time for switching from the voltage to the voltage for imaging.
[0073]
Next, in a period 34, imaging ultrasonic transmission and echo reception are performed. Imaging ultrasound is an example of an embodiment of the second ultrasound in the present invention. The transmitted ultrasonic wave at this time has, for example, a sound pressure of less than 0.5 MPa and a frequency of 1.5 to 1.8 MHz. The scanning range of the ultrasonic beam is the microballoon destruction range. The length of the imaging period 34 is, for example, several mS to several S.
[0074]
By repeating the above sequence for each desired destruction range, the inside of the subject 4 is scanned, and a contrast agent image is generated based on the harmonic echo. When the ultrasonic probe 2 has a two-dimensional ultrasonic transducer array, for example, as shown in FIG. 11, destruction is performed with a thick ultrasonic beam 208 and, for example, a 4 × 4 matrix within the effective destruction range 210 is obtained. You may make it send and receive the ultrasonic wave for imaging sequentially along each sound ray 202 corresponding to (matrix). This is preferable in terms of increasing the destruction efficiency per one transmission. In addition, in FIG. 11, the ultrasonic beam 208 and each sound ray 202 are shown in a cross-sectional view perpendicular to the transmission / reception direction of the ultrasonic wave, that is, a cross-sectional view.
[0075]
FIG. 12 shows an example in which microballoon destruction and echo reception are performed in a form different from the above. As shown in the figure, in this example, a transmission ultrasonic wave having a width or a cross section extending over three adjacent sound rays 20n-1, 20n, 20n + 1 is used. The sound rays 20n-1, 20n, 20n + 1 are scanned in this order.
[0076]
The sound pressure intensity profile 212 in the width direction or in the cross section is a sound pressure sufficient to destroy the microballoon on the central sound ray 20n, and on the sound rays 20n-1, 20n + 1 on both sides. So, the sound pressure does not destroy the microballoon.
[0077]
While the two-dimensional region 206 is scanned in a sound ray sequence by such a transmission ultrasonic wave, an echo for the transmission on the sound ray 20n is received along the sound ray 20n-1. The sound ray 20n-1 is where an ultrasonic wave that destroys the microballoon has passed during the previous transmission, and a time of 1 PRT (pulse repetition time) has elapsed since the destruction of the microballoon. Therefore, on this sound ray, the microballoon has already been destroyed and the bubbles are sufficiently released.
[0078]
For this reason, the harmonic echo from a bubble can be received along the sound ray 20n-1, and a shadow agent image can be generated based on the echo. This imaging is efficient because it is not necessary to newly transmit ultrasonic waves for bubble imaging. Further, by appropriately defining the intensity profile 212, it is possible to receive an acoustic ray 20n-2 (not shown), that is, an echo of a portion destroyed by the previous transmission. As a result, the state of bubbles after 2PRT can be imaged.
[0079]
Also, an image can be generated using the echo of the sound ray 2n + 1. This image is an image of the state before destruction of the microballoon. That is, contrast imaging in the non-destructive mode can be performed, and imaging in the non-destructive mode and imaging in the destructive mode can be performed at a time by ultrasonic scanning of one frame. In addition, if the echoes of the sound ray 2n-2 are also used, two types of contrast mode contrast agent images can be obtained.
[0080]
If the difference between the contrast-enhanced image in the non-destructive mode and the contrast-enhanced image in the destructive mode is obtained between those having the same sound ray, an unnecessary component included in both can be removed. Moreover, the difference image of the contrast agent image before and after destruction provides new diagnostic information.
[0081]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to realize an ultrasonic imaging method and apparatus that effectively performs microballoon contrast imaging. In addition, it is possible to realize an ultrasonic imaging method and apparatus that performs contrast imaging using bubbles generated after destruction of the shell of the microballoon. In addition, it is possible to realize a microballoon destruction method that efficiently destroys the microballoons.
[Brief description of the drawings]
FIG. 1 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram of a transmission / reception unit in an apparatus according to an example of an embodiment of the present invention.
FIG. 3 is a conceptual diagram of sound ray scanning by an apparatus according to an example of an embodiment of the present invention.
FIG. 4 is a block diagram of a B-mode processing unit in an apparatus according to an example of an embodiment of the present invention.
FIG. 5 is a block diagram of an image processing unit in an apparatus according to an example of an embodiment of the present invention.
FIG. 6 is a block diagram of a harmonic processing unit in an example apparatus according to an embodiment of the present invention.
FIG. 7 is a schematic diagram of a display image in an apparatus according to an example of an embodiment of the present invention.
FIG. 8 is a waveform diagram showing an example of a transmission signal in an apparatus according to an example of an embodiment of the present invention.
FIG. 9 is a waveform diagram showing an example of a transmission signal in an example apparatus according to an embodiment of the present invention.
FIG. 10 is a schematic diagram showing a sequence of ultrasonic transmission / reception in the apparatus according to the example of the embodiment of the present invention.
FIG. 11 is a schematic diagram showing a cross section of an ultrasonic beam for breaking a microballoon in an apparatus according to an example of an embodiment of the present invention.
FIG. 12 is a conceptual diagram of sound ray scanning by an apparatus according to an example of an embodiment of the present invention.
[Explanation of symbols]
2 Ultrasonic probe
4 subjects
40 Microballoon contrast agent
6 transceiver
10 B-mode processing section
14 Image processing unit
16 Display section
18 Control unit
20 Operation unit
602 Transmission timing generation circuit
604 Transmitting beamformer
606 Transmission / reception switching circuit
608 selector
610 Receiving beamformer
110 Fundamental wave processing unit
112 Harmonic processing section
140 Bus
142 Sound ray data memory
144 Digital scan converter
146 Image memory
148 image processor
200 Radiation point
202 Sound ray
204 arc
206 2D region
208 Divergence point
114 Range gate
116 FFT section
118 switching section
120 Coefficient calculator
122 Spectrum simulation section
124 subtraction
126 iFFT unit
160 Tomographic image of tissue
162 harmonic echo image
208 Ultrasonic beam
210 Effective destruction range
20n-1, 20n, 20n + 1 sound ray

Claims (6)

Transmitting / receiving means for transmitting ultrasonic waves to the subject and receiving echoes thereof;
A calculation means for calculating a leakage component of the harmonic echo contained in the echo obtained by the transmission / reception means in a state where a microballoon contrast agent is not injected into the subject;
Subtracting means for subtracting the leakage component from the harmonic echo obtained by the transmitting / receiving means in a state where a microballoon contrast agent is injected into the subject,
An ultrasonic imaging apparatus, comprising: an image generation unit configured to generate an image based on the harmonic echo after the subtraction. The ultrasonic imaging apparatus according to claim 1,
The high-frequency echo subtracted by the subtracting means is B-mode image data which is sound ray data,
The calculating means and the subtracting means are included in a B-mode processing means connected to the transmitting / receiving means and the image generating means,
The ultrasonic imaging apparatus, wherein the image generation unit generates the image to be displayed on a display unit by converting the sound ray data output from the B-mode processing unit. The ultrasonic imaging apparatus according to claim 2,
The B-mode processing means includes FFT means for Fourier transforming the echo signal output from the transmission / reception means, and iFFT means for inverse Fourier transforming the signal output from the subtraction means,
The calculation means calculates a coefficient representing a spectrum leakage from the fundamental wave of the ultrasonic wave transmitted by the transmission / reception means based on the frequency spectrum from the FFT means obtained without injecting the microballoon contrast agent into the subject. A coefficient calculation unit to be obtained, and a spectrum leakage from the fundamental wave based on the frequency spectrum from the FFT means obtained in a state where a microballoon contrast agent is injected into the subject and the coefficient obtained by the coefficient calculation unit are simulated. And a spectrum simulation unit generated by
The ultrasonic imaging apparatus, wherein the subtracting unit subtracts a spectrum leakage generated by the spectrum simulation unit from a frequency spectrum from the FFT unit obtained in a state where a microballoon contrast agent is injected into the subject. The ultrasonic imaging apparatus according to claim 2 or 3,
The B-mode processing means processes the echo signal having a frequency corresponding to the fundamental wave of the ultrasonic wave transmitted by the transmission / reception means by the high-frequency processing means having the calculation means and the subtraction means, and is sound ray data. An ultrasonic imaging apparatus comprising fundamental wave processing means for forming B-mode image data. The ultrasonic imaging apparatus according to claim 4,
The tissue tomogram based on the B-mode image data formed by the fundamental wave processing means and the high-frequency echo image based on the B-mode image data formed by the high-frequency processing means are synthesized, and the synthesized image is displayed on the display means. Display
In the synthesized image, the display color of the tomographic image of the tissue and the display color of the high-frequency echo image are different from each other. In the ultrasonic imaging device according to any one of claims 1 to 5,
The ultrasonic imaging apparatus, wherein the transmitting / receiving means transmits an ultrasonic wave that does not destroy the shell of the microballoon.

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