JPH10277042A - Ultrasonic diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge an effective opening width in opening synthesis even at the time of using a probe provided with a wave front convergence means and to perform the opening synthesis in a state close to the phase characteristics of ultrasonic waves. SOLUTION: This device is provided with the probe 1 provided with the wave front convergence means, a scanning mechanism 2 for controlling the relative position to a reflector 13 of the probe 1, a memory 4 for storing reception signals after converting the ultrasonic waves reflected from the reflector 13 to electric signals in the probe 1 and a signal synthesis part 5 for performing opening synthesis computation by supplying prescribed delay time to the reception signals stored in the memory 4 and performing addition based on the wave front phase information of the ultrasonic waves. An opening synthesis method is changed correspondingly to the positions in a spherical wave area for converging the ultrasonic wave energy of the probe 1 at a focus 12 and the spherical wave area for diffusing the ultrasonic wave energy of the reception signals and synthesis signals opening-synthesized in the signal synthesis part 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus using an aperture synthesis method.

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus, an aperture synthesizing method is known as a means for increasing a resolution (azimuth resolution) in a direction orthogonal to a traveling direction of an ultrasonic wave.

FIG. 7 is a block diagram showing a schematic configuration of a conventional ultrasonic diagnostic apparatus using a single transducer. In the same figure, 71 is a vibrator, 72 is a scanning mechanism for scanning the vibrator 71 in a one-dimensional direction with respect to a reflector 73 as an object,
74 supplies a high-frequency signal for generating ultrasonic waves from the vibrator 71 to the vibrator 71, and converts the ultrasonic waves reflected by the reflector 73 and returned to the vibrator 71 into electric signals from the vibrator 71. The signal received by the transmission / reception circuit 74 is amplified and detected, and then subjected to a predetermined digital signal processing.
5 is stored.

The signal synthesizing section 76 includes a wavefront phase information memory 7
7 based on the phase information of the ultrasonic beam stored in
An aperture synthesis operation is performed by giving a predetermined delay time to the high-frequency reception signal from the memory 75 obtained by each transmission and reception and adding them. Reference numeral 78 denotes a screen display unit that converts the combined signal output from the signal combining unit 76 into a video signal for television and displays the video signal.

As described above, in the aperture synthesizing method, a plurality of reception signals are obtained by repeatedly transmitting and receiving while scanning the vibrator 71 by the scanning mechanism 72. In this case, the ultrasonic beam transmitted from the vibrator 71 can be regarded as a spherical wave from the vibrator 71, and the reception signal is synthesized by giving an appropriate delay in the reception synthesis unit 76. A synthesized signal having a good azimuth resolution independent of distance can be obtained.

However, in this aperture synthesis method, as shown by the dotted line, the broken line and the solid line in FIG. 7, the transmission and reception are performed while the ultrasonic beam is expanded, so that the obtained reception signal becomes weak and a sufficient SN ratio is obtained. There is a problem that it cannot be obtained. In order to solve this problem, there is a method of performing aperture synthesis by using a vibrator having a wavefront converging means as described in Japanese Patent Application Laid-Open No. Sho 62-47348 and considering a convergence point of an ultrasonic beam as a sound source.

[0007]

However, in the method disclosed in Japanese Patent Application Laid-Open No. Sho 62-47348, the approximation that a convergence point is regarded as a sound source is established only at a portion where the ultrasonic beam converges. There is a problem that the effective opening width cannot be increased.

For example, as shown in FIG. 8, when the transducer 81 is scanned rightward with respect to the reflector 82 to obtain a signal of the position of the reflector 82, a problem occurs at the positions of the openings i and j of the transducer 81. However, the ultrasonic beam k transmitted and received from the position of the aperture k of the transducer 81 cannot be used for aperture synthesis.

The present invention has been made to solve the above-mentioned problem. Even if a probe having a wavefront converging means is used, the effective aperture width in aperture synthesis can be made large and can be used in practice. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of performing aperture synthesis in a state close to the phase characteristics of ultrasonic waves.

[0010]

In order to solve the above-mentioned problems, an ultrasonic diagnostic apparatus according to the present invention comprises an ultrasonic probe having a wavefront converging means and a relative position of the ultrasonic probe with respect to a subject. Scanning means for controlling the ultrasonic wave reflected from the subject and the like, a storage means for storing a received signal after converting the ultrasonic wave into an electric signal by the ultrasonic probe, based on the wavefront phase information of the ultrasonic wave Signal synthesizing means for performing an aperture synthesizing operation by giving a predetermined delay time to the received signal stored in the storage means and adding the resultant signal. The aperture synthesis method is changed in accordance with the position in the spherical wave region where the ultrasonic energy of the ultrasonic probe converges at the focal point and the position in the spherical wave region where the ultrasonic energy is diffused.

According to the present invention, even when a probe having a wavefront focusing means is used, the effective aperture width in aperture synthesis can be made large, and the aperture is close to the phase characteristic of the ultrasonic wave actually used. Can be synthesized.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to an ultrasonic probe having a wavefront focusing means, and a scanning means for controlling a relative position of the ultrasonic probe with respect to a subject. A storage unit for storing a received signal after converting an ultrasonic wave reflected from the subject or the like into an electric signal by the ultrasonic probe, and stored in the storage unit based on wavefront phase information of the ultrasonic wave. Signal synthesizing means for performing aperture synthesizing operation by giving a predetermined delay time to the received signal and adding the signals, and a synthesized signal aperture-synthesized by the signal synthesizing means and an ultrasonic probe The aperture synthesizing method is changed in accordance with a position in a spherical wave region in which acoustic energy converges to a focal point and a position in a spherical wave region in which the ultrasonic energy is diffused. By changing It may take a large effective aperture width in the synthesis.

According to the first aspect of the present invention, the aperture synthesis method comprises:
Aperture synthesis is performed by assuming the focal point where the spherical wave emitted from the probe converges as a virtual sound source, and spherical synthesis where ultrasonic energy is diffused as spherical waves emitted from the end of the probe. It is possible to perform good aperture synthesis with a simple calculation.

According to a third aspect of the present invention, there is provided a wavefront amplitude information memory for storing amplitude information of an ultrasonic beam for designating a range for performing aperture synthesis, and a main lobe of the ultrasonic beam stored in the wavefront amplitude information memory. It further includes an aperture control unit that determines the aperture width of aperture synthesis according to information, and can adjust the number of received signals to be synthesized according to the thickness of the main lobe of the ultrasonic beam and the presence or absence of side lobes, thereby achieving an efficient aperture. Compositing becomes possible.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram illustrating a configuration of an ultrasonic diagnostic apparatus according to Embodiment 1 of the present invention, FIG. 2 is a conceptual diagram of a phase characteristic of an ultrasonic beam for explaining an operation of the ultrasonic diagnostic apparatus, and FIG. FIG. 4 is a conceptual diagram for explaining the operation of the ultrasonic diagnostic apparatus, and FIG. 4 is an operation explanatory diagram of the ultrasonic diagnostic apparatus.

In FIG. 1, reference numeral 1 denotes a probe constituted by a piezoelectric vibrator such as a zinc oxide crystal film. An acoustic lens 11 constituting wavefront focusing means is provided on the lower surface of the probe 1. The acoustic lens 11 converges an ultrasonic beam generated from the probe 1 to a focal point 12. Reference numeral 2 denotes a scanning mechanism that scans the probe 1 including the acoustic lens 11 in a one-dimensional direction (Y direction) with respect to the reflector 13 as an object, and 3 generates an ultrasonic wave from the probe 1. A high-frequency pulse is supplied to the probe 1 for causing the
A transmission / reception circuit that receives a signal from the probe 1 that converts the ultrasonic wave reflected back to the probe 1 and returned to the probe 1 into an electric signal. The signal received by the transmission / reception circuit 3 is amplified and detected. Thereafter, predetermined digital signal processing is performed and the memory 4
Is stored.

The signal synthesizing section 5 gives a predetermined delay time to the high frequency reception signal from the memory 4 obtained by each transmission and reception based on the phase information of the ultrasonic beam stored in the wavefront phase information memory 6. Aperture synthesis operation is performed by adding the signals, and is composed of a digital delay circuit for giving a predetermined delay time to the received signal, a digital adding circuit for adding the delayed processed received signal, and the like. The wavefront phase information memory 6 stores the phase information of the ultrasonic wave for performing aperture synthesis.
The ultrasonic phase information memories 6A, 6B, and 6C corresponding to the areas A, B, and C shown in FIG. 3 are stored, and the ultrasonic phase information memories 6A, 6B, and 6C are selected based on the positional relationship between the synthesized signal and the received signal. Then, it is taken into the signal synthesizing unit 6. 7
Is a screen display unit for converting a synthesized signal output from the signal synthesizing unit 6 into a video signal for television and displaying it.

The operation of the ultrasonic diagnostic apparatus configured as described above will be described with reference to FIGS.

First, as shown in FIG. 2, the probe 1 generates a convergent ultrasonic beam in the Z direction, and most of the acoustic energy converges on the focal point 12 through the region A by the acoustic lens 11. The convergence state of the ultrasonic wave in this area A is the focus 1
It can be considered that a sound wave is emitted using 2 as a virtual sound source. However, some ultrasonic energy diffuses into regions B and C. The state in which the ultrasonic beam diffuses in this area B is as follows.
It can be considered that a sound wave is emitted spherically from the probe surface end 1a. In addition, the state in which the ultrasonic beam is diffused in the region C can be regarded as that the sound wave is emitted spherically from the probe surface end 1b.

FIG. 3 shows the state of a plurality of ultrasonic beams when the probe 1 is repeatedly transmitted and received while moving in the Y direction. The beam i corresponding to the aperture i of the probe 1 is a solid line. And a beam j corresponding to the aperture j of the probe 1
Is represented by a dotted line, and a beam k corresponding to the aperture k of the probe 1 is represented by a broken line. Here, a case will be described in which aperture synthesis of a reception signal at the position of the reflector 21 is performed using the beams i to k.

Since the reflector 21 is in the region A for the beams i and j, the aperture synthesis is performed by regarding the beams i and j as spherical waves whose focal points are virtual sound sources. Further, since the beam k is in the region C, the beam k is applied to the probe surface end 1b.
Aperture synthesis assuming spherical waves radiated from.

FIG. 4 is an explanatory diagram in the case where aperture synthesis is performed on the synthesized signal at each point on the virtual scanning line 24 in FIG. 3 using the beam i, the beam j, and the beam k.

First, when the virtual scanning line 14 is compared with the beam i, all points on the virtual scanning line 14 are in the region C of the beam i.
It is in. Therefore, the beam i is regarded as a spherical wave radiated from the probe surface end 1b, and aperture synthesis is performed. As a result, the received signal from the reflectors 21 and 22 by the beam i has the waveform shown on the left side of FIG. 4A, and the received signal after the delay processing has the waveform on the right side of FIG. 4A.

For beam j, the first half is area A
The second half is the area C. Therefore, the virtual scanning line 14
In the case of obtaining the combined signal of the upper first half, aperture synthesis is performed by regarding the beam j as a spherical wave having the focal point 12 as a virtual sound source, and in the case of obtaining the combined signal of the latter half, the probe surface Aperture synthesis is performed assuming the spherical wave radiated from the end 1b. As a result, the received signal from the reflectors 21 and 22 by the beam j has the waveform shown on the left side of FIG. 4B, and the received signal after the delay processing has the waveform on the right side of FIG. 4B.

Similarly, for the beam k, the first half is the area A and the second half is the area B. Therefore, when obtaining the composite signal of the first half point on the virtual scanning line 14, the beam k is regarded as a spherical wave having the focal point 12 as a virtual sound source and aperture synthesis is performed. Performs aperture synthesis on the assumption that the wave is a spherical wave radiated from the probe surface end 1a. As a result, the reception signal from the reflectors 21 and 22 by the beam k has a waveform shown on the left side of FIG. 4C, and the reception signal after the delay processing has a waveform on the right side of FIG. 4C.

When the composite signal at each point on the virtual scanning line 14 is obtained in this manner, the received signals after the delay processing by the beam i, the beam j, and the beam k are added, and the waveform shown in FIG. A composite signal is required.

In FIG. 4, the reflector 22 on the virtual scanning line 13 is
It is shown that the signal received from the reflector 21 located outside the virtual scanning line 14 is attenuated.

As described above, according to the first embodiment of the present invention, even when the probe 1 having the acoustic lens 11 as the wavefront focusing means is used, the effective aperture width in aperture synthesis can be widened. In addition, since aperture synthesis can be performed in a state close to the phase characteristics of the ultrasonic waves actually used, a good azimuth resolution can be obtained.

In the first embodiment, the phase characteristics of the ultrasonic wave are a spherical wave whose focal point is a virtual sound source and a spherical wave whose sound source is a probe surface end, but more suitable for an actual wavefront. If so, the performance can be further improved.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 5 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to Embodiment 2 of the present invention, and FIG. 6 is a conceptual diagram of an amplitude characteristic of a main lobe of an ultrasonic beam for explaining an operation of the ultrasonic diagnostic apparatus. .

In FIG. 5, the same or similar components as those in FIG. 1 are denoted by the same reference numerals and described. Reference numeral 1 denotes a probe constituted by a concave piezoelectric vibrator. The wavefront converging means is constituted, and the ultrasonic beam generated from the probe 1 is converged on the focal point 12. Reference numeral 2 denotes a scanning mechanism that scans the probe 1 in a one-dimensional direction (Y direction) with respect to the reflector 13 as an object. Reference numeral 3 denotes a high-frequency pulse for generating ultrasonic waves from the probe 1. Is supplied to the probe 1 and receives a signal from the probe 1 obtained by converting the ultrasonic wave reflected by the reflector 13 and returning to the probe 1 to an electric signal. The signal received by the circuit 3 is amplified and detected, subjected to predetermined digital signal processing, and stored in the memory 4.

The wavefront amplitude information memory 8 stores ultrasonic amplitude information for designating a range in which aperture synthesis is performed. The aperture control unit 9 determines the aperture width of aperture synthesis according to the main lobe information of the ultrasonic beam stored in the wavefront amplitude information memory 8.

The signal synthesizing section 5 gives a predetermined delay time to the high frequency reception signal from the memory 4 obtained by each transmission and reception based on the phase information of the ultrasonic beam stored in the wavefront phase information memory 6. Aperture synthesis operation is performed by adding the signals, and is composed of a digital delay circuit for giving a predetermined delay time to the received signal, a digital adding circuit for adding the delayed processed received signal, and the like. The wavefront phase information memory 6 stores the phase information of ultrasonic waves for performing aperture synthesis.
The ultrasonic phase information memories 6A, 6B, and 6C corresponding to the areas A, B, and C shown in FIG. 3 are stored, and the ultrasonic phase information memories 6A, 6B, and 6C are selected based on the positional relationship between the synthesized signal and the received signal. Then, it is taken into the signal synthesizing unit 6. 7
Is a screen display unit for converting a synthesized signal output from the signal synthesizing unit 6 into a video signal for television and displaying it.

The ultrasonic diagnostic apparatus configured as described above will be described with reference to FIG.

As in the case described above with reference to FIG. 2, most of the ultrasonic beam generated from the probe 1 converges on the focal point 12, but does not converge completely on one point near the focal point. 6
It has a spread as shown. A significant part of this spread is occupied by the main lobe. In addition, the aperture synthesis method is a method of creating one beam having a higher azimuth resolution from a plurality of beams by calculation. However, since most of the ultrasonic energy is collected in the main lobe, the amplitude is large, and the synthesis is performed. The effect on the signal is also large.

Therefore, in the present embodiment, the wavefront amplitude information is stored in the wavefront amplitude information memory 8 so that the aperture control section 9 eliminates the combining process in the side lobe regions D or E other than the main lobe. Adjust the opening width. This makes it possible to adjust the number of received signals to be combined depending on the thickness of the main lobe of the ultrasonic beam and the presence / absence of side lobes, thereby enabling efficient aperture synthesis. Other operations are the same as those in FIG. In the above embodiment, the case where the wavefront converging means is constituted by an acoustic lens or a concave vibrator has been described. However, the present invention is not limited to this. It is possible. Although the scanning mechanism has been described by way of example of performing parallel movement, the present invention can be similarly applied to a case where the scanning mechanism has an arbitrary moving direction such as rotational movement or manual operation. Further, although an example has been described in which aperture synthesis is performed on the probe surface end side from the focal point, aperture synthesis at a location far from the focal point can also be performed.

[0037]

As described above, according to the ultrasonic diagnostic apparatus of the present invention, the effective aperture width in aperture synthesis can be increased by changing the synthesizing method depending on the positional relationship between the synthesized signal and the received signal. Aperture synthesis can be performed in a state close to the phase characteristics of the ultrasonic wave used for the above, and good azimuth resolution can be obtained.

Further, according to the present invention, aperture synthesis is performed by regarding the focal point at which the spherical wave radiated from the probe converges as a virtual sound source, and the spherical wave at which the ultrasonic energy is diffused is converted from the probe surface end. By performing aperture synthesis on the assumption that the sphere is a radiated spherical wave, it is possible to perform good aperture synthesis with a simple calculation.

Further, according to the present invention, by changing the aperture width according to the amplitude characteristics of the wavefront, it is possible to adjust the number of received signals to be synthesized depending on the thickness of the main lobe of the ultrasonic beam and the presence or absence of the side lobe, Efficient aperture synthesis can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an ultrasonic diagnostic apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a conceptual diagram of a phase characteristic of an ultrasonic beam for describing an operation of the ultrasonic diagnostic apparatus according to the first embodiment of the present invention.

FIG. 3 is a conceptual diagram for explaining the operation of the ultrasonic diagnostic apparatus according to the first embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of the ultrasonic diagnostic apparatus according to the first embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a conceptual diagram of an amplitude characteristic of a main lobe of an ultrasonic beam for describing an operation of the ultrasonic diagnostic apparatus according to the second embodiment of the present invention.

FIG. 7 is a block diagram showing a schematic configuration of a conventional ultrasonic diagnostic apparatus.

FIG. 8 is a diagram for explaining the operation of aperture synthesis of a conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Probe 11 Acoustic lens (wavefront convergence means) 2 Scanning mechanism 3 Transmission / reception circuit 4 Memory (storage means) 5 Signal synthesis part 6 Wavefront phase information memory 7 Screen display part 8 Wavefront amplitude information memory 9 Aperture control part 12 Focus 13, 21, 22 reflector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Hagiwara 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside Matsushita Communication Industrial Co., Ltd. Matsushita Communication Industrial Co., Ltd.

Claims (3)

[Claims] An ultrasonic probe having wavefront focusing means;
Scanning means for controlling the relative position of the ultrasonic probe with respect to the subject, and storage for storing a reception signal after converting the ultrasonic wave reflected from the subject or the like into an electric signal by the ultrasonic probe; Means, signal synthesizing means for performing aperture synthesis operation by adding a predetermined delay time to the received signal stored in the storage means based on the wavefront phase information of the ultrasonic wave and adding the signal, the signal synthesizing means The aperture synthesis method is changed according to the positions of the synthesized signal to be subjected to aperture synthesis and the spherical wave region where the ultrasonic energy of the ultrasonic probe of the received signal converges to the focal point and the spherical wave region where the ultrasonic energy is diffused. An ultrasonic diagnostic apparatus comprising: 2. The aperture synthesis method performs aperture synthesis by regarding a focal point at which a spherical wave emitted from a probe converges as a virtual sound source, and radiates a spherical wave in which ultrasonic energy is diffused from a probe surface end. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein aperture synthesis is performed assuming the obtained spherical wave. 3. A wavefront amplitude information memory for storing amplitude information of an ultrasonic beam for designating a range for performing aperture synthesis, and an aperture corresponding to main lobe information of the ultrasonic beam stored in the wavefront amplitude information memory. 3. The ultrasonic diagnostic apparatus according to claim 1, further comprising an aperture control unit that determines a synthetic aperture width.