JP4083875B2 - Ultrasonic wave transmitter and ultrasonic imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic wave transmission method and apparatus and an ultrasonic imaging apparatus, and more particularly to an ultrasonic wave transmission method and apparatus for performing imaging based on a subharmonic echo for a microballoon contrast agent. The present invention also relates to an ultrasonic imaging apparatus.
[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 enclosing a gas harmless to a living body in a shell made of a substance harmless to the living body. A so-called subharmonic imaging is performed in which such a microballoon is injected into a subject, an ultrasonic wave is irradiated to destroy the shell, and an image is generated based on a subharmonic echo generated accordingly.
[0003]
[Problems to be solved by the invention]
Although ultrasonic waves having a plurality of continuous waves are used as the transmitted ultrasonic waves for destroying the microballoons, there is a problem that the certainty of subharmonic echo generation is low.
[0004]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ultrasonic transmission method and apparatus with high certainty of subharmonic echo generation, and such an ultrasonic transmission apparatus. It is to realize an ultrasonic imaging apparatus.
[0005]
[Means for Solving the Problems]
(1) In the first invention for solving the above-described problem, when transmitting an ultrasonic wave having a plurality of continuous waves, a microballoon is placed before and after at least one wave having an instantaneous sound pressure that does not destroy the microballoon. An ultrasonic imaging method characterized by transmitting ultrasonic waves each having a wave having an instantaneous sound pressure to be destroyed.
[0006]
(2) A second invention that solves the above-described problem is an ultrasonic transmission device that transmits ultrasonic waves having a plurality of continuous waves, and has at least one instantaneous sound pressure that does not destroy the microballoon. An ultrasonic transmission device comprising: a transmission means for transmitting ultrasonic waves each having a wave having an instantaneous sound pressure that breaks the microballoon before and after the wave.
[0007]
(3) A third invention for solving the above-described problem is an ultrasonic wave for generating an image based on a subharmonic echo by transmitting an ultrasonic wave having a plurality of continuous waves to a subject into which a microballoon has been injected. An imaging apparatus, comprising: a wave sending means for sending ultrasonic waves each having a wave having an instantaneous sound pressure that breaks a microballoon before and after at least one wave having an instantaneous sound pressure that does not break the microballoon An ultrasonic imaging apparatus characterized by:
[0008]
In any one of the first to third inventions, in the waves existing before and after the at least one wave, the generation of the subharmonic echo indicates that the instantaneous sound pressure of the subsequent wave is higher than that of the previous wave. This is preferable in that it is more reliable.
[0009]
(Function)
In the present invention, at least one wave having an instantaneous sound pressure that does not break the microballoon is inserted between two waves having an instantaneous sound pressure that breaks the microballoon, and the frequency at which the breaking pressure acts is set to Lower than the fundamental frequency.
[0010]
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. 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.
[0011]
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 an ultrasonic transducer array (not shown). The ultrasonic probe 2 is used in contact with the subject 4 by an operator (not shown). A microballoon contrast medium 40 is injected into the subject 4 in advance.
[0012]
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 an ultrasonic transmission device according to the present invention. Moreover, it is an example of embodiment of the wave transmission means in this invention.
[0013]
A block diagram of the transceiver 6 is shown in FIG. In the drawing, a transmission timing (timing) generation circuit 602 periodically generates a transmission timing signal and inputs it to a transmission beamformer 604.
[0014]
The transmission beamformer 604 drives a plurality of ultrasonic transducers constituting a transmission aperture in the ultrasonic transducer array with time difference based on the transmission timing signal. A plurality of drive signals are generated and input to the transmission / reception switching circuit 606. The waveform of the drive signal is selected so that the sound pressure waveform of the transmitted ultrasonic wave has a waveform as described later.
[0015]
The transmission / reception switching circuit 606 inputs a plurality of drive signals to the ultrasonic transducer array. The plurality of ultrasonic transducers constituting the transmission aperture in the array respectively transmit 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.
[0016]
The ultrasonic beam generates an instantaneous sound pressure having a sound pressure waveform as shown in FIG. That is, as shown in the figure, the sound pressure waveform is composed of a plurality of continuous waves, and the peak values of the second cycle wave and the fourth cycle wave set the fracture limit of the microballoon shell. It has come to exceed.
[0017]
Due to the irradiation of the ultrasonic beam, the shell of the microballoon is destroyed when the sound pressure waveform exceeds the destruction limit. Here, the destruction of the shell of the microballoon (hereinafter simply referred to as “breaking of the microballoon”) is performed sequentially by two waves separated by one cycle, thereby generating acoustic radiation (acoustic emission ( The acoustic emission)) has a frequency that is ½ of the fundamental frequency of the transmitted ultrasonic wave, for example, as shown in FIG. That is, an “echo” having a frequency that is half the fundamental frequency of the transmitted ultrasonic wave, that is, a subharmonic echo is generated.
[0018]
Of the two waves that destroy the microballoon, if the instantaneous sound pressure of the subsequent wave is higher than the previous wave, the wave that was not destroyed by the previous wave will be destroyed by the subsequent wave to generate acoustic radiation. Therefore, the generation of subharmonic echoes can be made more reliable. Of course, a wave having a higher peak value may be placed on the later wave in the same manner.
[0019]
For example, as shown in FIG. 4A, the sound pressure waveform of the transmitted ultrasonic wave is obtained by inserting two cycles of a wave having a low peak value between two waves having a high peak value that destroy the microballoon. Also good. As a result, a subharmonic echo having a frequency 1/3 of the fundamental frequency of the transmitted ultrasonic wave can be obtained as shown in FIG.
[0020]
Similarly, a sub-harmonic echo having a desired frequency can be obtained by selecting the number of low-peak values between two waves. In any case, it is preferable to raise the peak value of the wave after the previous wave among the two waves for breaking the microballoon in order to surely generate the subharmonic echo.
[0021]
FIGS. 3 and 4 show an example in which the microballoon is destroyed with a positive sound pressure, but it is a matter of course that the microballoon may be destroyed with a negative sound pressure. Since the microballoon has the property of breaking at a pressure whose absolute value is smaller than the positive pressure when a negative pressure is used, the microballoon can be efficiently broken.
[0022]
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 direction of the ultrasonic beam is sequentially changed by the transmission beam former 604. 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.
[0023]
The transmission / reception switching circuit 606 is configured to input a plurality of echo signals received by the reception apertures in the ultrasonic transducer array to the reception beam former 610. The reception beamformer 610 adjusts the phase by adding a time difference to a plurality of reception echoes, and then adds them to form an echo reception signal along the sound ray, that is, perform beamforming of reception waves. It has become. The received beamformer 610 scans the received sound ray in accordance with the transmission. The transmission timing generation circuit 602 through the reception beamformer 610 described above are controlled by the control unit 18 described later.
[0024]
The transceiver 6 having such a configuration performs scanning as shown in FIG. 5, for example. That is, an ultrasonic beam (sound ray) 202 extending in the z direction from the radiation point 200 scans the fan-shaped two-dimensional region 206 in the θ direction, and performs a so-called sector scan.
[0025]
When the transmission and reception apertures are formed by using a part of the ultrasonic transducer array, the apertures are sequentially moved along the array to perform scanning as shown in FIG. 6, for example. That is, by translating a sound ray 202 emitted from the radiation point 200 in the z direction along a linear locus 204, a rectangular two-dimensional region 206 is scanned in the x direction, and a so-called linear scan is performed. Done.
[0026]
When the ultrasonic transducer array is a so-called convex array formed along an arc extending in the ultrasonic wave transmission direction, for example, as shown in FIG. Thus, it goes without saying that a so-called convex scan can be performed by moving the radiation point 200 of the sound ray 202 along the arc-shaped locus 204 and scanning the fan-shaped two-dimensional region 206 in the θ direction.
[0027]
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). The B-mode processing unit 10 includes, for example, a fundamental wave processing unit 110 and a subharmonic processing unit 130 as shown in FIG. The fundamental wave processing unit 110 and the subharmonic processing unit 130 receive the output signal of the receiving beam former 610 in common.
[0028]
The fundamental wave processing unit 110 has a filter (not shown) that passes an echo reception signal having the same frequency as the fundamental frequency of the fundamental wave echo, that is, the transmitted ultrasonic wave. The sub-harmonic processing unit 130 includes a filter (not shown) that passes a sub-harmonic echo, that is, an echo reception signal having the same frequency as the sub-harmonic of the transmitted ultrasonic wave.
[0029]
The fundamental wave processing unit 110 obtains a signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A scope signal, by logarithmic amplification and envelope detection of the fundamental wave echo for the input signal. The B-mode image data is formed using the instantaneous amplitude of the A scope signal as the luminance value. That is, the fundamental wave processing unit 110 generates B-mode image data based on the fundamental wave echo.
[0030]
The subharmonic processing unit 130 obtains a signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A scope signal by logarithmic amplification and envelope detection of the subharmonic echo for the input signal. B-mode image data is formed using the instantaneous amplitude of the A scope signal as a luminance value. That is, the subharmonic processing unit 130 generates B-mode image data based on the subharmonic echo.
[0031]
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 plurality of B-mode images based on a plurality of systems of B-mode image data input from the B-mode processing unit 10.
[0032]
As shown in FIG. 9, the image processing unit 14 includes a sound ray data memory 142, a digital scan converter 144, an image memory 146, and an image processor connected by a bus 140. (processor) 148 is provided.
[0033]
The B-mode image data by the fundamental wave echo and the subharmonic echo inputted for each sound ray from the B-mode processing unit 10 is stored in the sound ray data memory 142, respectively. Each sound ray data space is formed in the sound ray data memory 142.
[0034]
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.
[0035]
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.
[0036]
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. Under the control of the control unit 18, ultrasonic imaging is performed.
[0037]
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.
[0038]
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.
[0039]
The transmission / reception unit 6 transmits / receives ultrasonic waves by sound ray sequential scanning. That is, for example, sector scanning as shown in FIG. 5 is performed in the order of sound rays, an ultrasonic beam is transmitted for each sound ray, an echo is received, and a B-mode image is generated based on the echo reception signal. . Of course, the linear scan and the convex scan shown in FIGS. 6 and 7 may be performed.
[0040]
The ultrasonic beam transmitted at this time has, for example, the sound pressure waveform shown in FIG. 3, and the microballoon in the microballoon contrast medium 40 is destroyed by two waves exceeding the microballoon destruction limit, and the subharmonic echo is surely obtained. To cause.
[0041]
B-mode image data is formed by the B-mode processing unit 10 based on the echo reception signal of each sound ray. The B-mode image data is formed based on the fundamental wave echo and based on the sub-harmonic echo, and is stored in the sound ray data memory 142 of the image processing unit 14.
[0042]
The image processor 148 scan-converts the B-mode image data of a plurality of systems in the sound ray data memory 142 by the digital scan converter 144 and writes them in the image memory 146 respectively.
[0043]
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. 13, a composite image of the tomographic image 160 of the tissue and the subharmonic echo image 162 is displayed.
[0044]
The example of performing B-mode imaging using sub-harmonic echo has been described above. However, ultrasonic imaging is not limited to B-mode imaging, and dynamic images can be captured using Doppler shift of sub-harmonic echo. Needless to say, the image may be taken.
[0045]
【The invention's effect】
As described above in detail, according to the present invention, an ultrasonic wave transmission method and apparatus with high reliability of subharmonic echo generation, and an ultrasonic imaging apparatus equipped with such an ultrasonic wave transmission apparatus are realized. can do.
[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 waveform diagram showing instantaneous sound pressure and subharmonic echo of transmitted ultrasonic waves in the apparatus according to an example of the embodiment of the present invention.
FIG. 4 is a waveform diagram showing instantaneous sound pressure and subharmonic echoes of a transmitted ultrasonic wave in an apparatus according to an example of an embodiment of the present invention.
FIG. 5 is a conceptual diagram of sound ray scanning by an apparatus according to an example of an embodiment of the present invention.
FIG. 6 is a conceptual diagram of sound ray scanning by an apparatus according to an example of an embodiment of the present invention.
FIG. 7 is a conceptual diagram of sound ray scanning by an apparatus according to an example of an embodiment of the present invention.
FIG. 8 is a block diagram of a B-mode processing unit in an example apparatus according to an embodiment of the present invention.
FIG. 9 is a block diagram of an image processing unit in an apparatus according to an example of an embodiment of the present invention.
FIG. 10 is a schematic diagram illustrating an example of a display image in the apparatus according to the exemplary embodiment of the present invention.
[Explanation of symbols]
2 Ultrasonic probe 4 Subject 40 Micro balloon contrast agent 6 Transmission / reception unit 10 B mode processing unit 14 Image processing unit 16 Display unit 18 Control unit 20 Operation unit 602 Transmission timing generator circuit 604 Transmission beam former 606 Transmission / reception switching circuit 610 Wave beam former 110 Fundamental wave processing unit 130 Sub harmonic processing unit

Claims (3)

An ultrasonic transmission device for transmitting an ultrasonic wave having a plurality of continuous waves in one transmission, a plurality of times,
The plurality of continuous waves have the same period and a single wave having a half wavelength with both ends having an amplitude of 0, and a single wave having an instantaneous sound pressure that breaks the microballoon. There are at least one wave with instantaneous sound pressure that does not destroy the microballoon before and after, and there are a plurality of waves with instantaneous sound pressure that destroy the microballoon. An ultrasonic wave transmission device comprising a wave transmission means for performing the above operation. An ultrasonic imaging apparatus that transmits an ultrasonic wave having a plurality of continuous waves by one transmission to a subject into which a microballoon has been injected, and generates an image based on a subharmonic echo,
The plurality of continuous waves have the same period and a single wave having a half wavelength with both ends having an amplitude of 0, and a single wave having an instantaneous sound pressure that breaks the microballoon. There are at least one wave with instantaneous sound pressure that does not destroy the microballoon before and after, and there are a plurality of waves with instantaneous sound pressure that destroy the microballoon. An ultrasonic imaging apparatus comprising a wave transmitting means. The ultrasonic imaging apparatus according to claim 1,
The ultrasonic wave imaging device, wherein the wave transmitting means transmits a wave having the same polarity of instantaneous sound pressure that destroys the microballoon.

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