JP2000005167A - Ultrasonic wave transmission and device therefor, and ultrasonic photographing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the security of the generation of subharmonic echo by transmitting ultrasonic waves in which waves having an instantaneous acoustic pressure at which a microballoon is destructed exist, respectively, in the front and rear of at least one wave having an instantaneous acoustic pressure at which a microballoon is not destructed. SOLUTION: An acoustic pressure wave form is composed of a plurality of continuous waves, and wave height values of a wave in the second cycle and a wave in the fourth cycle exceed a destruction limit of a shell of a microballoon. The shell of the microballoon is destructed when an acoustic wave form exceeds the destruction limit due to the irradiation of ultrasonic beams. The shell of a microballon is destructed sequentially by two waves across one cycle so that the acoustic emission generated due to the destruction has a frequency of 1/2 of a basic frequency of an ultrasonic wave to be sent, for example, as shown in Fig. (b). That is, an echo having a frequency of 1/2 of the basic frequency of the ultrasonic wave to be transmitted, namely, a subharmonic echo, is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for transmitting ultrasonic waves and an ultrasonic imaging apparatus, and more particularly to an apparatus for imaging a microballoon contrast medium based on a subharmonic echo. The present invention relates to an ultrasonic wave transmitting method and apparatus, and an ultrasonic imaging apparatus.

[0002]

2. Description of the Related Art In ultrasonic imaging using a contrast agent, a microballoon contrast agent obtained by mixing a large number of microballoons having a diameter of 1 to several μm into a liquid is used. The microballoon is formed by encapsulating a gas harmless to a living body in a shell made of a substance harmless to the living body. The so-called subharmonic imaging is performed in which such a microballoon is injected into the subject, the shell is destroyed by irradiating ultrasonic waves, and an image is generated based on the subharmonic echo generated accordingly.

[0003]

As the transmitted ultrasonic wave for destroying the microballoon, an ultrasonic wave having a plurality of continuous waves is used, but there is a problem that the reliability of generating a subharmonic echo is low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an ultrasonic wave transmitting method and apparatus having high reliability of generating a subharmonic echo, and
It is an object of the present invention to realize an ultrasonic imaging apparatus provided with such an ultrasonic transmitting device.

[0005]

Means for Solving the Problems (1) According to a first invention for solving the above-mentioned problems, in transmitting an ultrasonic wave having a plurality of continuous waves, at least an instantaneous sound pressure that does not destroy microballoons is transmitted. An ultrasonic imaging method characterized by transmitting ultrasonic waves each having a wave having an instantaneous sound pressure that destroys a micro balloon before and after one wave.

(2) A second aspect of the present invention for solving the above-mentioned problem is an ultrasonic transmitting apparatus for transmitting an ultrasonic wave having a plurality of continuous waves, which has an instantaneous sound pressure that does not destroy microballoons. An ultrasonic wave transmitting device, comprising: a wave transmitting unit that transmits ultrasonic waves each having a wave having an instantaneous sound pressure that destroys a micro balloon before and after at least one wave.

(3) According to a third aspect of the present invention, an ultrasonic wave having a plurality of continuous waves is transmitted to a subject into which a microballoon is injected, and an image is generated based on a subharmonic echo. Transmitting means for transmitting ultrasonic waves in which at least one wave having an instantaneous sound pressure that does not destroy a microballoon is present before and after at least one wave having an instantaneous sound pressure that destroys a microballoon. And an ultrasonic imaging apparatus.

[0008] In any one of the first to third inventions, it is preferable that the waves present before and after the at least one wave have a subharmonic whose instantaneous sound pressure of a later wave is higher than that of a preceding wave. This is preferable in that the generation of an echo is further ensured.

(Action) In the present invention, at least one wave having an instantaneous sound pressure that does not destroy the microballoon is inserted between two waves having an instantaneous sound pressure that destroys the microballoon, and the frequency at which the breakdown pressure acts Is made lower than the fundamental frequency of the transmitted ultrasonic wave.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the ultrasonic imaging apparatus. This apparatus is an example of an embodiment of the ultrasonic imaging apparatus of the present invention. An example of an embodiment of the device of the present invention is shown by the configuration of the present device. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

The configuration of the present apparatus will be described. As shown in FIG. 1, the present apparatus has an ultrasonic probe (probe) 2. The ultrasonic probe 2 has an ultrasonic transducer array (not shown). Ultrasonic probe 2
Is used in contact with the subject 4 by an operator (not shown). The subject 4 is provided with a microballoon contrast agent 4 in advance.
0 has been injected.

The ultrasonic probe 2 is connected to a transmitting / receiving unit 6. The transmitting / receiving unit 6 supplies a drive signal to the ultrasonic probe 2 to transmit ultrasonic waves into the subject 4. The transmission / reception unit 6 also receives an echo from the subject 4 that the ultrasonic probe 2 has received.
The ultrasonic probe 2 and the transmitting / receiving unit 6 are an example of an embodiment of the ultrasonic wave transmitting device according to the present invention. It is also an example of an embodiment of the wave transmitting means in the present invention.

FIG. 2 shows a block diagram of the transmission / reception section 6. In the figure, a transmission timing (timing) generating circuit 602
Is configured to periodically generate a transmission timing signal and input the transmission timing signal to a transmission beamformer (beamformer) 604.

The transmission beamformer 604 is configured to perform transmission beamforming (beamforming) based on the transmission timing signal.
ming) signal, that is, a plurality of drive signals for driving a plurality of ultrasonic transducers forming a transmitting aperture in the ultrasonic transducer array with a time difference, and inputting the signals to the transmission / reception switching circuit 606. I have. 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.

The transmission / reception switching circuit 606 inputs a plurality of drive signals to the ultrasonic transducer array. A plurality of ultrasonic transducers constituting a transmission aperture in the array transmit a plurality of ultrasonic waves having a phase difference corresponding to a time difference between a plurality of drive signals. An ultrasonic beam is formed by wavefront synthesis of those ultrasonic waves.

The ultrasonic beam generates an instantaneous sound pressure having a sound pressure waveform as shown in FIG. That is, the sound pressure waveform is composed of a plurality of continuous waves as shown in FIG.
The peak value of the (cycle) wave and the fourth cycle wave exceeds the breaking limit of the microballoon shell.

By the irradiation of the ultrasonic beam, the shell of the microballoon is broken when the sound pressure waveform exceeds the breaking limit. Here, the destruction of the shell of the microballoon (hereinafter, simply referred to as the destruction of the microballoon) is sequentially performed by two waves separated by one cycle, so that acoustic emission (acoustic emission (acoustic emission ( acoustic emission)) has, for example, half the fundamental frequency of the transmitted ultrasonic wave as shown in FIG. That is, an "echo" having a frequency half of the fundamental frequency of the transmitted ultrasonic wave, that is,
Subharmonic echo occurs.

When the instantaneous sound pressure of the latter wave is higher than that of the preceding wave, the latter wave is destroyed by the latter wave, and the acoustic wave is respectively emitted. Since it can be generated, the generation of the subharmonic echo can be made more reliable. It is needless to say that a wave having a higher peak value may be similarly placed after the latter wave.

As shown in FIG. 4A, for example, the sound pressure waveform of the transmitted ultrasonic wave includes two cycles of a wave having a low peak value between two waves having a high peak value for destroying a micro balloon. It may be good. As a result, FIG.
As shown in (1), a sub-harmonic echo having a frequency of 1/3 of the fundamental frequency of the transmitted ultrasonic wave can be obtained.

Similarly, a sub-harmonic echo of a desired frequency can be obtained by selecting the number of low-peak waves to be inserted between two waves. In either case,
It is preferable to increase the crest value of the wave after the previous wave among the two waves for breaking the micro balloon in order to surely generate a subharmonic echo.

FIGS. 3 and 4 show an example in which the micro balloon is broken at a positive sound pressure. However, the micro balloon may be broken at a negative sound pressure.
The microballoon has a property of breaking at a pressure having an absolute value smaller than that of a positive pressure when a negative pressure is used, so that efficient breaking can be performed.

The transmission of the ultrasonic beam is repeatedly performed at predetermined time intervals by a transmission timing signal generated by the transmission timing generation circuit 602. The direction of the ultrasonic beam is sequentially changed by the transmission beam former 604.
Thereby, the inside of the subject 4 is scanned by the sound ray formed by the ultrasonic beam. That is, the inside of the subject 4 is scanned in a sound ray sequence.

The transmission / reception switching circuit 606 inputs a plurality of echo signals received by the reception aperture in the ultrasonic transducer array to the reception beam former 610. The receive beamformer 610 applies a time difference to the plurality of received echoes to adjust the phases, and then adds them to form an echo received signal along the sound ray, that is,
Receiving beam forming is performed.
The reception sound beam is also scanned by the reception beamformer 610 in accordance with the transmission. The transmission timing generation circuit 602 to the reception beam former 610 are controlled by the control unit 18 described later.

The transmission / reception section 6 having such a configuration performs, for example, scanning as shown in FIG. That is, the radiation point 200
An ultrasonic beam (sound ray) 202 extending in the z-direction scans a fan-shaped two-dimensional area 206 in the θ-direction to perform a so-called sector scan.

When the transmitting and receiving 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. Can be. That is, the sound ray 2 emitted from the radiation point 200 in the z direction
02 is translated along the linear trajectory 204, so that the rectangular two-dimensional area 206 is scanned in the x direction, so-called linear scan is performed.

Incidentally, the ultrasonic transducer array is
In the case of a so-called convex array formed along an arc extending in the ultrasonic wave transmission direction, for example, as shown in FIG. The point 200 is moved along the arc-shaped trajectory 204, and the fan-shaped two-dimensional area 20 is moved.
It is needless to say that so-called convex scanning can be performed by scanning 6 in the θ direction.

The transmission / reception unit 6 is connected to a B-mode (mode) processing unit 10, and inputs an echo reception signal for each sound ray to the B-mode processing unit 10. B-mode processing unit 10
Is for forming B-mode image data (data). B
The mode processing unit 10 includes a fundamental wave processing unit 110 and a sub-harmonics processing unit 130, for example, as shown in FIG. The output signal of the receiving beamformer 610 is commonly input to the fundamental wave processing unit 110 and the subharmonics processing unit 130.

The fundamental wave processing unit 110 has a filter (not shown) that passes a fundamental wave echo, that is, an echo reception signal having the same frequency as the fundamental frequency of the transmitted ultrasonic wave. The sub-harmonics processing unit 130 has a filter (not shown) that passes a sub-harmonic echo, that is, an echo reception signal having the same frequency as the sub-harmonics of the transmitted ultrasonic wave.

The fundamental wave processing unit 110 performs
By performing logarithmic amplification and envelope detection of the fundamental wave echo, a signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A scope signal is obtained, and the instantaneous amplitude of the A scope signal is obtained. B-mode image data is formed as each luminance value. That is, the fundamental wave processing unit 110 generates B-mode image data based on the fundamental wave echo.

The sub-harmonics processing unit 130 performs logarithmic amplification and envelope detection of the sub-harmonic echo of the input signal, thereby obtaining a signal representing the intensity of the echo at each reflection point on the sound ray, that is, an A-scope signal. Thus, B-mode image data is formed using the instantaneous amplitude of the A scope signal as a luminance value. That is, the sub-harmonics processing unit 130 generates B-mode image data based on the sub-harmonic echo.

The B-mode processing unit 10 is connected to the image processing unit 14. B-mode processing unit 10 and image processing unit 1
FIG. 4 shows an example of an embodiment of an image generating means according to the present invention. The image processing unit 14 generates a plurality of B-mode images based on a plurality of B-mode image data input from the B-mode processing unit 10.

As shown in FIG. 9, the image processing unit 14 has a sound ray data memory (d) connected by a bus 140.
ata memory) 142, digital scan converter
(digital scan converter) 144, an image memory 146 and an image processor 148.

The B-mode based on the fundamental echo and the sub-harmonic echo input from the B-mode processing unit 10 for each sound ray
The mode image data is stored in the sound ray data memory 142, respectively. Each sound ray data space is formed in the sound ray data memory 142.

Digital scan converter 144
Is for converting data in a sound ray data space into data in a physical space 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 1
Reference numeral 46 stores image data of the physical space. The image processor 148 performs predetermined data processing on the data in the sound ray data memory 142 and the image memory 146, respectively.

A display unit 16 is connected to the image processing unit 14. The display unit 16 is provided with an image signal from the image processing unit 14 and displays an image based on the image signal. The display unit 16 is capable of displaying a color image.

The transmitting / receiving 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 supplies a control signal to each unit to control its operation. Further, the control unit 18 is configured to receive various notification signals from the controlled units. Ultrasonic imaging is performed under the control of the control unit 18.

An operation unit 20 is connected to the control unit 18. The operation unit 20 is operated by the operator, and the control unit 18
A desired command or information is input to the device. The operation unit 20 includes, for example, an operation panel provided with a keyboard and other operation tools.

The operation of the present apparatus will be described. The operator touches the ultrasonic probe 2 to a desired portion of the subject 4 and operates the operation unit 20 to perform imaging. The imaging is performed under the control of the control unit 18.

The transmitting / receiving unit 6 transmits / receives ultrasonic waves by sound ray sequential scanning. That is, for example, a sector scan as shown in FIG. 5 is performed in sound ray sequence, an ultrasonic beam is transmitted for each sound ray, its 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.

The ultrasonic beam transmitted at this time has, for example, the sound pressure waveform shown in FIG. 3 and breaks the microballoons in the microballoon contrast agent 40 with two waves exceeding the microballoon breakage limit, thereby causing a subharmonic. Produces an echo reliably.

The 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 a fundamental echo and a sub-harmonic echo, respectively.
It is stored in the sound ray data memory 142 of the image processing unit 14.

The image processor 148 scan-converts a plurality of B-mode image data in the sound ray data memory 142 with the digital scan converter 144 and writes the data into the image memory 146.

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.

Although the example in which the B-mode imaging is performed using the sub-harmonic echo has been described above, the ultrasonic imaging is not limited to the B-mode imaging, and uses the Doppler shift of the sub-harmonic echo. It goes without saying that a dynamic image may be taken.

[0045]

As described above in detail, according to the present invention, an ultrasonic wave transmitting method and apparatus having high reliability of generation of subharmonic echo, and an ultrasonic wave equipped with such an ultrasonic wave transmitting apparatus. A sound wave imaging device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a block diagram of a transmission / reception unit in the device according to an embodiment of the present invention;

FIG. 3 is a waveform diagram showing an instantaneous sound pressure of a transmitted ultrasonic wave and a sub-harmonic echo in an apparatus according to an embodiment of the present invention.

FIG. 4 is a waveform diagram showing an instantaneous sound pressure and a sub-harmonic echo of transmitted ultrasonic waves in the apparatus according to an embodiment of the present invention.

FIG. 5 is a conceptual diagram of sound ray scanning performed by the apparatus according to the embodiment of the present invention;

FIG. 6 is a conceptual diagram of sound ray scanning performed by the apparatus according to an embodiment of the present invention;

FIG. 7 is a conceptual diagram of sound ray scanning performed by the apparatus according to an embodiment of the present invention;

FIG. 8 is a block diagram of a B-mode processing unit in the device according to an example of the embodiment of the present invention.

FIG. 9 is a block diagram of an image processing unit in the apparatus according to an example of the embodiment of the present invention;

FIG. 10 is a schematic diagram illustrating an example of a display image in the device according to the example of the embodiment of the present invention.

[Explanation of symbols]

 2 Ultrasonic probe 4 Subject 40 Micro balloon contrast agent 6 Transmitter / receiver 10 B-mode processor 14 Image processor 16 Display unit 18 Control unit 20 Operation unit 602 Transmission timing generation circuit 604 Transmission beam former 606 Transmission / reception switching circuit 610 Reception Wave beamformer 110 Fundamental wave processing unit 130 Subharmonics processing unit

Claims (3)

[Claims] When transmitting an ultrasonic wave having a plurality of continuous waves, at least one wave having an instantaneous sound pressure that does not destroy the microballoon is preceded and followed by waves having an instantaneous sound pressure that destroys the microballoon. An ultrasonic imaging method comprising transmitting an existing ultrasonic wave. 2. An ultrasonic transmitting apparatus for transmitting an ultrasonic wave having a plurality of continuous waves, comprising: an instantaneously breaking a micro balloon before and after at least one wave having an instantaneous sound pressure that does not destroy a micro balloon. An ultrasonic wave transmitting device, comprising: a wave transmitting means for transmitting ultrasonic waves each having a wave having a sound pressure. 3. An ultrasonic imaging apparatus for transmitting an ultrasonic wave having a plurality of continuous waves to a subject into which a microballoon has been injected and generating an image based on a subharmonic echo, wherein the microballoon is destroyed. An ultrasonic imaging apparatus, comprising: a transmitting unit that transmits an ultrasonic wave in which waves having an instantaneous sound pressure that destroys a micro balloon exist before and after at least one wave having an instantaneous sound pressure that does not occur. .