JPH11318890A - Ultrasonography and ultrasonograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To image a contrast while destroying a micro-balloon in an imaging range within an extremely short time by successively sending a first ultrasonic beam while varying azimuth in an imaging scheduled range, scanning the same range by a second ultrasonic beam and generating an image based on echo. SOLUTION: The first ultrasonic beam is provided with an instantaneous sound pressure level enough for sufficiently destroying the shell of the micro- balloon. Then, a two-dimensional area 206 being an imaging scheduled range is scanned by the first ultrasonic beam to destroy the micro-balloon. At the time, an ultrasonic beam (sound ray) 202 is speedily sent one after another by switching an azimuth fast to allow the wave faces of plural beams 202 different in azimuth to be advanced in parallel by successively delaying little at a time. Continually, in order to execute normal ultrasonic imaging the second ultrasonic beam for imaging is sent by each sound ray 202. Then, its echo is received to generate the image based on an echo receiving signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic imaging method and apparatus, and more particularly, to a microballoon.
n) An ultrasonic imaging method and apparatus for a subject into which a contrast agent has been injected.

[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. Such a microballoon is injected into the subject, and the shell is destroyed by irradiating ultrasonic waves, and the bubbles released as a result are used for imaging.

[0003] Since bubbles generate second harmonic echoes of transmitted ultrasonic waves due to non-linear echo sources, the distribution of bubbles in the body is generated by generating an image based on the second harmonic echo. Is imaged. Alternatively, it is possible to obtain a bubble image, that is, a contrast image, by obtaining a difference between an image captured in a state where bubbles are not generated before breaking the microballoon and an image captured in a state where bubbles are generated by breaking the microballoon. Done.

[0004] The bubbles released by the destruction of the shell dissolve in blood or the like and disappear in, for example, several milliseconds, and thus have a very short life. In order to image such a short-lived bubble, transmission of an ultrasonic beam for destroying a micro balloon, transmission of an ultrasonic beam for imaging a bubble, and its echo are performed for each sound ray of ultrasonic beam scanning. We are going to receive waves.

[0005]

In order to obtain a contrast image from the difference between the images taken before and after the destruction of the microballoon, the destruction of the microballoon must be performed at once for the imaging range, and then the imaging is performed. Although it is preferable in that the sound ray scanning conditions for imaging before and after the destruction of the microballoon are the same, transmitting ultrasonic waves for destroying the microballoons in the imaging range at once is a normal transmission for driving the ultrasonic probe. Instantaneous power of wave driver
(power) There is a problem that it is difficult to realize because it exceeds the limit of ability.

Further, as described above, in the method in which the microballoon is destroyed for each sound ray and the imaging operation is repeated, the sound ray scanning conditions before and after the destruction of the microballoon are not the same. There has been a problem that the obtained difference image is not always appropriate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to destroy microballoons in an imaging range within a very short time within the limit of the instantaneous power capability of a normal transmission driver. To realize an ultrasonic imaging method and apparatus for performing contrast imaging.

[0008]

Means for Solving the Problems (1) According to a first aspect of the present invention, an object in which a microballoon contrast medium is injected is scanned with an ultrasonic beam to generate an image based on an echo. An imaging method, comprising: setting a first imaging range having an instantaneous sound pressure that destroys a shell of the micro balloon.
With the ultrasonic beam of, the wavefront of the ultrasonic beam transmitted in one direction scans in the order of sound rays in relation to transmitting the ultrasonic beam in the next direction while the wavefront of the ultrasonic beam is traveling in the planned imaging range, Next, a range scanned by the first ultrasonic beam is scanned by a second ultrasonic beam in a sound ray sequence, and an image is generated based on an echo.

(2) A second invention for solving the above-mentioned problems is an ultrasonic imaging apparatus which scans a subject into which a microballoon contrast medium is injected with an ultrasonic beam and generates an image based on an echo, The planned imaging range is changed while the wavefront of the ultrasonic beam transmitted in one direction is traveling through the planned imaging range by the first ultrasonic beam having the instantaneous sound pressure that destroys the shell of the microballoon. Ultrasonic scanning means for scanning in the order of sound rays in order to transmit the ultrasonic beam in the next direction, and scanning the area scanned with the first ultrasonic beam in the order of sound rays with the second ultrasonic beam. An ultrasonic imaging apparatus comprising: an ultrasonic transmitting / receiving unit that receives an echo; and an image generating unit that generates an image based on the echo.

In the first invention or the second invention, it is preferable that the planned imaging range is obtained by dividing one frame of the imaging screen into a plurality of regions, and the scanning time of the ultrasonic beam for destroying the micro balloon is reduced. It is preferable in terms of shortening.

(Function) In the present invention, the imaging range is set to be the wavefront of the ultrasonic beam transmitted in one direction by the first ultrasonic beam having the instantaneous sound pressure that destroys the shell of the microballoon. Scanning is performed in the order of sound rays in order to transmit an ultrasonic beam in the next direction while moving through the range. Thereby, the scanning time of the ultrasonic wave for micro-balloon destruction in the imaging range is reduced.

[0012]

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 an ultrasonic scanning unit in the present invention. Moreover, it is an example of the embodiment of the ultrasonic transmitting / receiving means in the present invention.

FIG. 2 shows a block diagram of the transmitting / receiving section 6. As shown in FIG. 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 performs transmission beamforming based on the transmission timing signal.
ming) signal, i.e., a plurality of drive signals for driving a plurality of ultrasonic transducers constituting a transmitting aperture in the ultrasonic transducer array with a time difference, and input to the transmission / reception switching circuit 606. I have.

The drive signal has variable amplitude and waveform. As a result, as will be described later, a large-amplitude drive signal for transmitting an ultrasonic wave with a high instantaneous sound pressure that destroys the microballoon shell and an ultrasonic wave with a low instantaneous sound pressure that does not destroy the microballoon shell are transmitted. And a small-amplitude drive signal to be generated.

The transmission / reception switching circuit 606 inputs a plurality of drive signals to the ultrasonic transducer array. A plurality of ultrasonic transducers constituting a transmitting aperture in the array respectively generate 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 transmission of the ultrasonic beam is repeatedly performed at predetermined time intervals by the 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 beamformer 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. 4, 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.

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 harmonic processing unit 130, for example, as shown in FIG. The output signal of the reception beamformer 610 is commonly input to the fundamental wave processing unit 110 and the harmonic processing unit 130.

The fundamental wave processing unit 110 has a filter (not shown) for passing a fundamental wave echo, that is, an echo reception signal having the same frequency as the center frequency of the transmitted ultrasonic wave. The harmonic processing unit 130 has a filter (not shown) that passes a second harmonic echo, that is, an echo reception signal having the same frequency as the second harmonic of the center frequency 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 harmonic processing unit 130 converts the input signal
By performing logarithmic amplification and envelope detection of the second harmonic 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 amplitude of each instant of the A scope signal is determined. B-mode image data is formed as the luminance value. That is, the harmonic processing unit 130 generates B-mode image data based on the second 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 systems of B-mode image data input from the B-mode processing unit 10.

As shown in FIG. 7, the image processing unit 14 includes 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 image data based on the fundamental echo and the second harmonic echo input from the B-mode processing unit 10 for each sound ray are 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.

First, an ultrasonic wave for breaking the shell of the microballoon is transmitted. FIG. 8 shows such an ultrasonic wave.
As shown in (a), an ultrasonic wave in which the first half cycle is negative pressure is used. Such an ultrasonic wave can be generated, for example, by a drive signal or the like in which the first half cycle has a negative electrode name.

When such an ultrasonic wave is applied to the microballoon, its shell is broken by a cavitation effect due to a negative pressure. A shell having a relatively high hardness is easily broken by a negative pressure. Due to the non-linearity of the propagation of ultrasonic waves in the subject, for example, as shown in FIG. 8B, the instantaneous sound pressure waveform tends to have a longer negative period as it progresses. The extension of the negative period increases the application time of the negative pressure, and more and more favorably destroys the microballoon shell. Therefore, the shell can be destroyed even at a relatively low instantaneous sound pressure, and the efficiency is good. Also, the steepness of the positive portion of the instantaneous sound pressure waveform is advantageous in that destruction is promoted.

On the other hand, as shown in FIG. 9A, when a positive ultrasonic wave is used in the first half cycle, it is shown in FIG. As shown in FIG. 8, the positive portion becomes steep, but the interval between them does not change, and the period of negative pressure does not increase.
The effect of breaking the shell of the microballoon is inferior to the case of
Therefore, when the first half cycle uses a positive ultrasonic wave, it is necessary to increase the instantaneous sound pressure level of the transmitted ultrasonic wave so as to obtain a sufficient destruction effect.

Here, it is assumed that the ultrasonic wave as shown in FIG. 8A is transmitted by the transmission / reception unit 6 to break the shell of the micro balloon, and the contrast imaging is performed using the released bubbles. Needless to say, the shell of the microballoon may be broken by using an ultrasonic wave as shown in FIG. Hereinafter, the destruction of the shell of the microballoon is simply referred to as the destruction of the microballoon.

The destruction of the microballoon is performed by scanning the two-dimensional area 206, which is the imaging range, with an ultrasonic beam. At this time, the transmission of the ultrasonic beam is performed in rapid succession while switching the direction at high speed.
As shown in (1), the wavefronts of a plurality of ultrasonic beams having different directions are sequentially translated with a slight delay. These ultrasonic beams are an example of an embodiment of the first ultrasonic beam in the present invention. FIG. 10 shows the case of the sector scan, but the cases of the linear scan and the convex scan are as shown in FIGS. 11 and 12, respectively.

In this way, the transmission of the ultrasonic wave in the last direction can be completed within the time when the wavefront of the ultrasonic wave reaches the deepest part of the two-dimensional area 206 in the direction transmitted first. For example, assuming that the depth of the two-dimensional region 206 in the z direction is 10 cm, the time required for the ultrasonic wave front to reach the deepest part is about 100 μs. The wave ends. In addition,
It is preferable to make the thickness of the ultrasonic beam as large as possible in order to scan the two-dimensional area 206 with a small number of sound rays.

The above time corresponds to half of the time required for transmitting ultrasonic waves for the two-dimensional area 206 for one sound ray and receiving the echo of the two-dimensional area 206 at the time of ordinary ultrasonic imaging of sound rays. Therefore, the two-dimensional region 206 is shorter than the ultrasonic transmission / reception time for one sound ray in normal ultrasonic imaging.
The transmission of the ultrasonic waves for microballoon destruction for the whole can be terminated. That is, it is possible to destroy the micro-balloons in the imaging range in a very short time. Moreover, since the microballoons are destroyed one sound ray at a time, it is possible to transmit such ultrasonic waves sufficiently within the range of the instantaneous power capability of the transmission driver in the transmission / reception unit 6.

Subsequent to the scanning of the ultrasonic beam for destruction, ordinary ultrasonic imaging is performed in the order of sound rays. That is, for example, a sector scan as shown in FIG. 3 is performed in a sound ray sequence, an ultrasonic beam for imaging is transmitted for each sound ray, the echo is received, and a B-mode image is generated based on the echo reception signal. Generate Of course, the linear scan and the convex scan shown in FIGS. 4 and 5 may be performed. The ultrasonic beam transmitted at this time is
The instantaneous sound pressure may be lower than that of the ultrasonic beam for micro-balloon destruction. This ultrasonic beam is an example of an embodiment of the second ultrasonic beam in the present invention.

Since the microballoons within the imaging range are destroyed in a time period of, for example, about 100 μs as described above, bubbles having a lifetime of, for example, about several milliseconds released from the shell during the imaging period by sound ray sequential Continue to exist without extinction. Therefore, stable contrast imaging using bubbles can be performed.

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 the fundamental echo and the second harmonic echo, respectively, and 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.
A composite image with the harmonic echo image 162 is displayed. When the same imaging range is imaged beforehand by ultrasonic waves that do not destroy the microballoon before the microballoon is destroyed, the fundamental echo images or the second harmonic echo images before and after the microballoon are destroyed, respectively. The difference between the images may be obtained, and the difference image may be displayed. In this case, the sound ray scanning conditions before and after the destruction of the microballoon are the same, and an appropriate difference image can be obtained.

The difference image between the fundamental wave echo images indicates a bubble image, and a contrast image can be obtained. In the difference image between the second harmonic echo images, a common component irrelevant to the bubble echo due to the non-linearity in ultrasonic transmission and reception is canceled out, and an image showing only the bubble image, that is, a precise contrast image can be obtained.

The above is an example in which a micro-balloon in an imaging range corresponding to one frame of the display screen is destroyed by one scan. One frame is divided into a plurality of regions, and the micro-balloon is divided for each region. May be performed one after another. This is preferable in that the scanning time of the ultrasonic wave for destruction is reduced. At this time, the plurality of regions may be set along the azimuth direction, or may be set for each focal zone along the depth direction. Alternatively, they may be combined. It should be noted that the images of the divided areas are finally synthesized and displayed.

The difference image is not limited to the image stored in the image memory, but may be applied to the sound ray data in the sound ray data memory.

[0051]

As described above in detail, according to the present invention, contrast imaging is performed by destroying microballoons within the imaging range within a very short time within the limit of the instantaneous power capability of the ordinary transmitting transmitter. An ultrasonic imaging method and apparatus 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 conceptual diagram of sound ray scanning performed by the apparatus according to the embodiment of the present invention;

FIG. 4 is a conceptual diagram of sound ray scanning performed by 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 block diagram of a B-mode processing unit in the device according to an example of the embodiment of the present invention.

FIG. 7 is a block diagram of an image processing unit in the apparatus according to the embodiment of the present invention;

FIG. 8 is a waveform diagram showing an example of a transmission signal for destroying microballoons in the apparatus according to an embodiment of the present invention.

FIG. 9 is a waveform chart showing an example of a transmission signal for destroying microballoons in the apparatus according to an embodiment of the present invention.

FIG. 10 is a conceptual diagram of ultrasonic scanning for breaking a microballoon by an apparatus according to an embodiment of the present invention.

FIG. 11 is a conceptual diagram of ultrasonic scanning for breaking a microballoon by an apparatus according to an embodiment of the present invention.

FIG. 12 is a conceptual diagram of ultrasonic scanning for breaking a microballoon by an apparatus according to an embodiment of the present invention.

FIG. 13 is a schematic diagram of a display image in the device according to an 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 processing unit 14 Image processing unit 16 Display unit 18 Control unit 20 Operation unit 602 Transmission timing generation circuit 604 Transmission beamformer 606 Transmission / reception switching circuit 610 Reception Wave beamformer 110 Fundamental wave processing unit 130 Harmonic processing unit

Claims (2)

[Claims] 1. An ultrasonic imaging method for scanning a subject injected with a microballoon contrast medium with an ultrasonic beam and generating an image based on an echo, wherein an imaging range is destroyed by a shell of the microballoon. The first ultrasonic beam having the instantaneous sound pressure transmits the ultrasonic beam in the next direction while the wavefront of the ultrasonic beam transmitted in one direction travels in the planned imaging range. Scanning by a sound ray sequence, and then scanning the area scanned by the first ultrasonic beam with a second ultrasonic beam in a sound ray sequence and generating an image based on an echo. Method. 2. An ultrasonic imaging apparatus which scans a subject injected with a microballoon contrast medium with an ultrasonic beam and generates an image based on an echo, wherein an imaging range is destroyed by a shell of the microballoon. The first ultrasonic beam having the instantaneous sound pressure transmits the ultrasonic beam in the next direction while the wavefront of the ultrasonic beam transmitted in one direction travels in the planned imaging range. Ultrasonic scanning means for scanning in the order of sound rays, ultrasonic transmitting and receiving means for scanning the area scanned by the first ultrasonic beam in the order of sound rays by the second ultrasonic beam and receiving echoes, Image generation means for generating an image based on the image,
An ultrasonic imaging apparatus comprising: