JP4023909B2 - Ultrasonic imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic imaging method and apparatus, and more particularly to an ultrasonic imaging method and apparatus for a subject injected with a microballoon contrast agent.
[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. Such a microballoon is injected into the subject, irradiated with ultrasonic waves to break the shell, and bubbles released as a result are used for imaging.
[0003]
Bubbles generate the second harmonic echo of the transmitted ultrasound due to the non-linear echo source. By generating an image based on the second harmonic echo, the distribution of bubbles in the body is imaged. Is done. Alternatively, it is possible to obtain a bubble image, that is, a contrast image, by obtaining a difference between an image taken without a bubble before destroying the microballoon and an image taken with the bubble created by breaking the microballoon. Done.
[0004]
Bubbles released by the destruction of the shell dissolve in blood or the like and disappear, for example, in a few ms, so that the lifetime is extremely short. In order to image such a short-lived bubble, the transmission of an ultrasonic beam for destroying a microballoon, the transmission of an ultrasonic beam for imaging a bubble, and the echoes of each sound ray of ultrasonic beam scanning Receives waves.
[0005]
[Problems to be solved by the invention]
When a contrast image is obtained from the difference between images taken before and after the destruction of the microballoon, the destruction of the microballoon is performed at once on the imaging range, and the subsequent imaging is performed before and after the destruction of the microballoon. Although it is preferable in terms of making the sound ray scanning conditions the same, transmitting an ultrasonic wave that destroys the microballoon in the imaging range all at once is the instantaneous power of a normal transmission driver (driver) that drives the ultrasonic probe ( power) There was a problem that it was difficult to realize because it exceeded the capacity limit.
[0006]
Further, as described above, in the method of repeatedly performing the imaging operation by destroying the microballoon for each sound ray, since the sound ray scanning conditions for imaging before and after the destruction of the microballoon are not the same, the obtained difference There has been a problem that images are not necessarily appropriate.
[0007]
The present invention has been made in order to solve the above-mentioned problems, and its purpose is to destroy a microballoon in an imaging range within a very short time within the limit of the instantaneous power capability of a normal transmission triber and perform contrast imaging. It is to realize an ultrasonic imaging method and apparatus for performing.
[0008]
[Means for Solving the Problems]
(1) A first invention for solving the above-mentioned problem is an ultrasonic imaging method for scanning an object injected with a microballoon contrast agent with an ultrasonic beam and generating an image on the basis of an echo. , While the wavefront of the ultrasonic beam transmitted in one azimuth by the first ultrasonic beam having an instantaneous sound pressure that breaks the shell of the microballoon travels through the planned imaging range, Scans the sound beam sequentially in relation to the transmission of the ultrasonic beam, and then scans the range scanned by the first ultrasonic beam sequentially with the second ultrasonic beam to generate an image based on the echo. This is an ultrasonic imaging method characterized by that.
[0009]
(2) A second invention that solves the above-described problem is an ultrasonic imaging apparatus that scans a subject into which a microballoon contrast agent has been injected with an ultrasonic beam and generates an image based on an echo, the imaging scheduled range , While the wavefront of the ultrasonic beam transmitted in one azimuth by the first ultrasonic beam having an instantaneous sound pressure that breaks the shell of the microballoon travels through the planned imaging range, Ultrasonic scanning means for scanning in the order of sound rays in relation to transmitting an ultrasonic beam, and a range scanned by the first ultrasonic beam in the order of sound rays by a second ultrasonic beam and receiving echoes An ultrasonic imaging apparatus comprising: an ultrasonic transmission / reception unit configured to perform an image generation unit configured to generate an image based on the echo.
[0010]
In the first invention or the second invention, the scheduled imaging range is obtained by dividing one frame of the imaging screen into a plurality of regions, which shortens the scanning time of the ultrasonic beam for microballoon destruction. Is preferable.
[0011]
(Function)
In the present invention, the wavefront of the ultrasonic beam transmitted in one direction is traveling through the imaging planned range by the first ultrasonic beam having an instantaneous sound pressure that destroys the microballoon shell. In the meantime, the acoustic beam is sequentially scanned so as to transmit an ultrasonic beam in the next direction. Thereby, the scanning time of the ultrasonic wave for microballoon destruction about the imaging scheduled range is shortened.
[0012]
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.
[0013]
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.
[0014]
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 ultrasonic scanning means in the present invention. Moreover, it is an example of embodiment of the ultrasonic transmission / reception means in this invention.
[0015]
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.
[0016]
The transmission beamformer 604 drives a plurality of ultrasonic transducers constituting a transmission aperture in the ultrasonic transducer array with a time difference based on the transmission timing signal. A plurality of drive signals are generated and input to the transmission / reception switching circuit 606.
[0017]
The drive signal has variable amplitude and waveform. Thus, as described later, a large-amplitude driving signal that transmits ultrasonic waves with high instantaneous sound pressure that destroys the microballoon shell and ultrasonic waves with low instantaneous sound pressure that do not destroy the microballoon shell are transmitted. And a small-amplitude driving signal to be generated.
[0018]
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 generate a plurality of ultrasonic waves having phase differences corresponding to the time differences of the plurality of drive signals. An ultrasonic beam is formed by wavefront synthesis of these ultrasonic waves.
[0019]
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.
[0020]
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.
[0021]
The transceiver 6 having such a configuration performs scanning as shown in FIG. 3, 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.
[0022]
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. 4, 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.
[0023]
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.
[0024]
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 a fundamental wave processing unit 110 and a harmonic processing unit 130, for example, as shown in FIG. The fundamental wave processing unit 110 and the harmonic processing unit 130 receive the output signal of the receiving beam former 610 in common.
[0025]
The fundamental wave processing unit 110 has a filter (not shown) that allows a fundamental wave echo, that is, an echo reception signal having the same frequency as the center frequency of the transmitted ultrasonic wave to pass therethrough. 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.
[0026]
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.
[0027]
The harmonic 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 second harmonic 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 harmonic processing unit 130 generates B-mode image data based on the second harmonic echo.
[0028]
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.
[0029]
As shown in FIG. 7, 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. (processor) 148 is provided.
[0030]
The B-mode image data by the fundamental wave echo and the second harmonic echo input 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.
[0031]
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.
[0032]
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.
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
First, an ultrasonic wave for breaking the microballoon shell is transmitted. As such an ultrasonic wave, an ultrasonic wave having a negative pressure in the first half cycle is used as shown in FIG. Such an ultrasonic wave can be generated, for example, by a drive signal having the first half cycle as a negative electrode.
[0037]
When such ultrasonic waves are applied to the microballoon, the shell is destroyed by a cavitation effect caused by negative pressure. The higher the hardness of the shell, the easier it is to break by negative pressure. Due to the nonlinearity of ultrasonic wave propagation within the subject, for example, as shown in FIG. 8B, the instantaneous 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, which has an advantageous effect on the destruction of the microballoon shell. For this reason, the shell can be broken even with a relatively low instantaneous sound pressure, and the efficiency is high. In addition, it is advantageous in that the positive portion of the instantaneous sound pressure waveform is steep in that the destruction is accelerated.
[0038]
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). Although the portion becomes steep, the interval between them does not change. Therefore, the period of negative pressure does not increase, so that the destruction effect of the microballoon shell is inferior to that in the case of FIG. 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.
[0039]
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 microballoon, and the contrast imaging is performed using the released bubbles. Of course, the shell of the microballoon may be destroyed by using ultrasonic waves as shown in FIG. Hereinafter, destruction of the shell of the microballoon is simply referred to as destruction of the microballoon.
[0040]
The destruction of the microballoon is performed by scanning the two-dimensional region 206, which is a planned imaging range, with an ultrasonic beam. At that time, transmission of the ultrasonic beam is performed quickly while switching the direction at high speed. For example, as shown in FIG. 10, the wave fronts of a plurality of ultrasonic beams having different directions are sequentially translated with little delay. To do. These ultrasonic beams are an example of an embodiment of the first ultrasonic beam in the present invention. FIG. 10 shows the case of sector scanning. In the case of linear scanning and convex scanning, for example, the scanning is as shown in FIGS. 11 and 12, respectively.
[0041]
In this way, the ultrasonic wave transmission for the last direction can be completed within the time when the ultrasonic wavefront reaches the deepest part of the two-dimensional region 206 in the first wave transmission direction. For example, if the depth of the two-dimensional region 206 in the z direction is 10 cm, the time for the ultrasonic wavefront to reach the deepest part is about 100 μs, and within this time, the two-dimensional region 206 is transmitted in all directions. The wave ends. Note that it is preferable to make the thickness of the ultrasonic beam as thick as possible from the viewpoint of scanning the two-dimensional region 206 with few sound rays.
[0042]
The above time corresponds to ½ of the time required to transmit an ultrasonic wave for one sound ray and receive the echo in the two-dimensional region 206 during normal sound ray sequential ultrasonic imaging. Therefore, the transmission of ultrasonic waves for breaking the microballoon for the entire two-dimensional region 206 can be completed in a time shorter than the ultrasonic transmission / reception time for one sound ray in normal ultrasonic imaging. That is, it is possible to destroy the microballoon within the imaging scheduled range in an extremely short time. In addition, since the microballoons are destroyed one sound ray at a time, such ultrasonic waves can be transmitted sufficiently within the range of the instantaneous power capability of the transmission driver in the transmission / reception unit 6.
[0043]
Subsequent to the scanning of the destructive ultrasonic beam, normal ultrasonic imaging is performed by sound ray sequential. That is, for example, sector scanning as shown in FIG. 3 is performed in order of sound rays, an ultrasonic beam for imaging is transmitted for each sound ray, the echo is received, and the B-mode image is received based on the echo reception signal. Is generated. 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 may have an instantaneous sound pressure lower than the ultrasonic beam for destroying the microballoon. This ultrasonic beam is an example of an embodiment of the second ultrasonic beam in the present invention.
[0044]
As described above, the microballoon within the planned imaging range is destroyed in a time of, for example, about 100 μs, so that the bubbles discharged from the shell have a lifetime of, for example, about several ms, disappear during the imaging period by the sound ray sequential. Continue to exist. Therefore, stable contrast imaging using bubbles can be performed.
[0045]
B-mode image data is formed by the B-mode processing unit 10 based on the echo reception signal of each sound ray. B-mode image data is formed based on the fundamental wave echo and based on the second harmonic echo, and is stored in the sound ray data memory 142 of the image processing unit 14.
[0046]
The image processor 148 scan-converts a plurality of systems of B-mode image data in the sound ray data memory 142 by the digital scan converter 144 and writes them to the image memory 146 respectively.
[0047]
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 second harmonic echo image 162 is displayed. Before destroying the microballoon, when imaging the same imaging range with ultrasonic waves that do not destroy the microballoon in advance, the fundamental echo images or the second harmonic echo images, respectively, before and after the destruction of the microballoon A difference between images may be obtained and a difference image may be displayed. In this case, the sound ray scanning conditions for imaging before and after the destruction of the microballoon are the same, and an appropriate difference image can be obtained.
[0048]
The difference image between the fundamental wave echo images shows a bubble image, and a contrast image can be obtained. In the difference image between the second harmonic echo images, common components irrelevant to the bubble echo due to nonlinearity in ultrasonic transmission and reception are canceled out, and an image showing only the bubble image, that is, a precise contrast image can be obtained.
[0049]
The above is an example in which the microballoon in the imaging range corresponding to one frame of the display screen is destroyed by one scan, but one frame is divided into a plurality of regions, and the microballoon is destroyed for each region. Subsequent imaging may be performed one by one. This is preferable in terms of shortening the scanning time of the ultrasonic waves for destruction. 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. Or you may make it combine them. Note that the image of the divided area is synthesized and displayed last.
[0050]
Needless to say, the difference image is not limited to the image in the image memory, and may be performed on the sound ray data in the sound ray data memory.
[0051]
【The invention's effect】
As described above in detail, according to the present invention, an ultrasonic imaging method for performing contrast imaging by destroying a microballoon in an imaging range within a very short time within the limit of the instantaneous power capability of a normal transmission triber and An apparatus can be realized.
[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 example apparatus according to 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 conceptual diagram of sound ray scanning by 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 block diagram of a B-mode processing unit in an apparatus according to an example of an embodiment of the present invention.
FIG. 7 is a block diagram of an image processing unit 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 for destroying a microballoon 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 for breaking a microballoon in the apparatus according to the embodiment of the present invention.
FIG. 10 is a conceptual diagram of ultrasonic scanning for microballoon destruction by an apparatus according to an example of an embodiment of the present invention.
FIG. 11 is a conceptual diagram of ultrasonic scanning for microballoon destruction by an apparatus according to an example of an embodiment of the present invention.
FIG. 12 is a conceptual diagram of ultrasonic scanning for microballoon destruction by an apparatus according to an example of an embodiment of the present invention.
FIG. 13 is a schematic diagram of a display image in an apparatus according to an example of an 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 Harmonic processing unit

Claims (1)

An ultrasound imaging apparatus that scans a subject injected with a microballoon contrast agent with an ultrasound beam and generates an image based on echoes,
While the imaging front range of the ultrasonic beam transmitted in one direction by the first ultrasonic beam having an instantaneous sound pressure that destroys the shell of the microballoon travels through the imaging target range. An ultrasonic scanning means for scanning in an acoustic ray sequence in relation to transmitting an ultrasonic beam in the next direction;
Ultrasonic transmission / reception means for receiving an echo by sequentially scanning a range scanned with the first ultrasonic beam with a second ultrasonic beam in an acoustic ray;
Image generating means for generating an image based on the echo;
An ultrasonic imaging apparatus comprising:

Images