JPH11216143A - Ultrasonic diagnostic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic equipment using a strict aperture combined method by taking the frequency dependency of sonic speed in a medium or a sound field into account. SOLUTION: This equipment comprises device 10 to memory the position of ultrasonic probe 1 driven by a scanner 5, a device 6 to memorize reflection signals received by a sending and receiving circuit 2, a device 7 to adjust the amount of group delay by giving a prescribed delay to signals, a device 8 to adjust phase of signals' carrier waves, and a device 9 to add signals. When reconstructing an image of a cross section using the aperture combined method, a positive-phase-sequence method of receiving signals is done by adjusting the amount of group delay of received reflection signals and by adjusting the amount of phase delay of carrier waves.

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 perpendicular to a traveling direction of an ultrasonic wave. FIG. 7 shows a block diagram of a conventional aperture synthesizing method using a single vibrator, which includes a vibrator 101, a vibrator scanning mechanism 102, a transmitting / receiving circuit 103, an open synthesizing processing unit 104, and a screen display unit 109. The open synthesis processing 104 includes a reception waveform memory 105, a position information memory 106, a signal delay unit 107,
It comprises a signal synthesis unit 108. In the aperture synthesis method, the transmitting and receiving circuit 1 is moved by moving the vibrator 101 by the scanning mechanism 102.
At 03, transmission and reception are performed to obtain a plurality of received signals. The received signal is given an appropriate delay by the signal delay unit 107 and synthesized by the signal synthesizing unit 108 (phasing addition) to obtain a synthesized signal having a good azimuth resolution independent of the distance from the transducer 101. be able to. Conventionally, the signal delay unit 10
In step 7, the amount of delay given to the received signal is constant at the speed of sound, and is determined from the positional relationship between the position of the target to be determined and the transducer that has transmitted and received.

[0003]

However, it is known that, in a general medium or a sound field, the speed of sound has a frequency dependence, and is formed by sound waves radiated from a probe of an ultrasonic diagnostic apparatus. In the sound field, the frequency dependence of the sound speed is particularly recognized due to the influence of diffraction and the like. Further, the waveform of the sound wave is a pulse, not a single frequency. Therefore, when performing strict aperture synthesis, it is necessary to provide a delay amount in consideration of the frequency dependence of the sound speed.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an ultrasonic diagnostic apparatus using a strict aperture synthesis method in consideration of the frequency dependence of the speed of sound in a medium or a sound field. .

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problem, the present invention provides a method of performing phasing addition using both a group speed which is a speed at which a pulse is transmitted and a phase speed which is a speed at which a carrier is transmitted. It is a characteristic. As described above, strict aperture synthesis taking into account the frequency dependence of the speed of sound in a medium or a sound field is obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention comprises an ultrasonic probe, means for controlling the position of the ultrasonic probe, and means for storing a received reflected signal. Means for correcting a group delay by giving a predetermined delay to a signal, means for correcting the phase of a carrier of the signal, and means for adding the signal, and ultrasound diagnosis for reconstructing a tomographic image by aperture synthesis In the apparatus, the phasing method of the received signal in the aperture synthesis is characterized by performing both the correction of the group delay amount of the received reflected signal and the correction of the phase delay amount of the carrier wave, and the sound velocity of the medium or the sound field in the aperture synthesis. Has the effect that strict aperture synthesis with the frequency dependence of the correction can be realized.

[0007] The invention described in claim 2 of the present invention provides
The means for correcting the phase of a carrier wave according to claim 1 is characterized in that the correction is performed by orthogonally transforming the received signal, and has an effect that the correction of the phase delay amount of the carrier wave can be realized by the orthogonal transform.

[0008] The invention described in claim 3 of the present invention provides:
A means for arbitrarily switching whether or not to correct the phase delay amount of the carrier according to claim 1;
If there is no frequency characteristic of the sound velocity or it is known in advance that the frequency characteristic can be neglected, there is an effect that the correction of the phase delay amount of the carrier wave can be prevented.

Further, the invention according to claim 4 of the present invention provides:
A means for switching whether or not to correct the phase delay amount of the carrier wave according to claim 1 during aperture synthesis processing, wherein the region where the frequency characteristic of the sound velocity is large and the frequency characteristic of the sound velocity do not exist at all or are ignored. In the case where there are areas where the correction can be performed, it is possible to switch whether or not to correct the phase delay amount even during the aperture synthesis processing.

The invention according to claim 5 of the present invention provides:
5. The ultrasonic diagnostic apparatus according to claim 4, further comprising an ultrasonic probe having a wavefront control unit, wherein whether or not to correct the phase delay amount of the carrier wave is determined by a positional relationship between a position to be obtained and the probe. Characterized by having means for switching,
An ultrasonic diagnostic apparatus having an ultrasonic probe having a wavefront control means has an effect that strict aperture synthesis can be realized with a small amount of calculation.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to Embodiment 1 of the present invention. The probe 1 performs transmission and reception while changing the position by the scanning mechanism 5. The transmission / reception unit 2 supplies a drive pulse to the probe 1 and amplifies and digitizes a signal received from the probe 1. The aperture synthesis processing unit 3 includes a reception waveform memory 6, a position information memory 10, a sound field information memory 11, a group delay amount correction unit 7, and a phase correction unit 8.
And a signal adder 9. The reception waveform memory 6 stores a high-frequency reception signal from the transmission / reception unit 2, the position information memory 10 stores the position information of the probe, and stores the sound field information memory 1.
Reference numeral 1 stores sound field information such as a phase delay and a group delay of a sound wave emitted from the probe 1. The position information of the probe 1 is 1
It corresponds to the received signal obtained by the first transmission and reception. The group delay amount correction unit 7 corrects the group delay amount by giving a predetermined delay to the received signal. The carrier phase corrector 8 corrects the phase of the carrier of the received signal. The signal adding unit 9 adds the received signal after the correction of the group delay amount and the phase of the carrier. The image display unit 4 converts the synthesized signal output from the aperture synthesis processing unit 3 into
The video signal is converted into a video signal such as TV and displayed on a display device such as a monitor.

The operation of the ultrasonic diagnostic apparatus configured as described above will be described with reference to FIG. FIG. 2 illustrates a case where aperture synthesis is performed using the received signals A to C obtained by transmitting and receiving the synthesized signal at each point on the synthesized scanning line 23 while changing the position of the probe. . First, based on the group delay characteristics of the sound field, a predetermined delay is given to the received signals A to C to correct the group delay amount. As a result, the phases of the reflected pulses from the reflector 21 on the to-be-combined scanning line 23 to be determined match, and the phases of the reflected pulses from the reflector 22 at positions deviated from the to-be-combined scanning line 23 do not match. Next, the phase of the carrier of the pulse included in each received signal is corrected. By adding these three signals, a combined signal on the combined scanning line 23 is obtained. Thereby, the combined scanning line 2
The signal from the reflector 21 above 3 is amplified because both the phase of the pulse and the phase of the carrier coincide with each other, and the signal from the reflector 22 that is shifted from the combined scanning line 23 is attenuated.

As described above, according to the first embodiment of the present invention, it is possible to perform strict aperture synthesis in consideration of the frequency dependence of the speed of sound in a medium or a sound field, and to obtain a good azimuth resolution. .

(Embodiment 2) FIG. 3 is a block diagram showing an ultrasonic diagnostic apparatus using FFT for carrier phase correction according to Embodiment 2 of the present invention. The probe 1 includes a scanning mechanism 5
The transmission and reception are performed while changing the position. Transceiver 2
Supplies a drive pulse to the probe 1 and amplifies and digitizes a signal received from the probe 1. The aperture synthesis processing unit 3 includes a reception waveform memory 6, a position information memory 10, a sound field information memory 11, a group delay correction amount calculation unit 16, a carrier wave phase correction amount calculation unit 17, a delay circuit 12, an FFT circuit 13, and a multiplication circuit 14. And an IFFT circuit 15 and a signal adder 9. The reception waveform memory 6 stores a high-frequency reception signal from the transmission / reception unit 2, the position information memory 10 stores the position information of the probe 1, and the sound field information memory 11 radiates from the probe 1. Sound field information such as phase delay and group delay of sound waves is stored. The position information of the probe 1 corresponds to a received signal obtained by one transmission / reception. Group delay correction amount calculator 16
Calculates the correction amount of the group delay amount of the received signal, and
2 is to delay the received signal by the group delay correction amount,
Correct the group delay amount. FFT circuit 13 converts the received signal into a complex frequency component. Carrier phase correction amount calculator 17
Calculates the frequency component of the phase correction amount of the carrier of the received signal, and multiplies the frequency component of the received signal by the multiplication circuit 14 by the multiplication circuit 14. The IFFT circuit 15 converts the complex received signal that has been subjected to the delay processing into a time axis signal. The signal adding unit 9 adds the received signal after the correction of the group delay amount and the phase of the carrier. The image display unit 4 converts the synthesized signal output from the aperture synthesis processing unit 3 into a video signal such as a TV and displays the video signal on a display device such as a monitor.

As described above, according to the second embodiment of the present invention, the received signal is converted into a complex frequency signal using the FFT, so that the phase of the carrier wave is not changed without changing the waveform of the pulse of the received signal. Can be corrected.

In the above description, the FFT is used for the orthogonal transform. However, the present invention is not limited to this.

(Embodiment 3) FIG. 4 is a block diagram showing an ultrasonic diagnostic apparatus according to Embodiment 3 of the present invention. The probe 1 performs transmission and reception while changing the position by the scanning mechanism 5. The transmitting and receiving unit 2 supplies a driving pulse to the probe 1,
Then, the signal received from the probe 1 is amplified and digitized. The aperture synthesis processing unit 3 includes a reception waveform memory 6, a position information memory 10, a sound field information memory 11, a group delay amount correction unit 7, a carrier phase correction unit 8, a signal addition unit 9, and switches 18 and 19. The reception waveform memory 6 stores a high-frequency reception signal from the transmission / reception unit 2, and the position information memory 10
The sound field information memory 11 stores position information of the probe, and stores sound field information such as a phase delay and a group delay of a sound wave radiated from the probe 1. The position information of the probe 1 corresponds to a received signal obtained by one transmission / reception. The group delay amount correction unit 7 corrects the group delay amount by giving a predetermined delay to the received signal. The carrier phase corrector 8 corrects the phase of the carrier of the received signal. The control unit 20 is a control unit of the entire ultrasound diagnostic apparatus, and switches the switches 18 and 19 when there is no frequency characteristic of the sound velocity of the sound field produced by the selected probe 1 and there is no frequency characteristic of the sound velocity of the medium. By operating, the carrier phase correction unit 8 is separated. The signal adder 9 adds the received signals after the correction of the group delay amount and the phase delay amount. The image display unit 4 converts the synthesized signal output from the aperture synthesis processing unit 3 into a TV signal.
And the like, and display on a display device such as a monitor.

As described above, according to the third embodiment of the present invention, the switches 18 and 19 are provided before and after the carrier phase correction unit 8, and these are controlled by the control unit 20, so that the frequency characteristic of the sound velocity is improved. When it is known in advance that there is no or negligible, the carrier phase correction unit can be separated, and the amount of calculation for correcting the phase delay amount can be reduced. When the carrier phase correction unit is separated, the configuration is exactly the same as that of the conventional aperture synthesis unit.

(Embodiment 4) FIG. 5 is a block diagram showing an ultrasonic diagnostic apparatus according to Embodiment 4 of the present invention. The probe 1 performs transmission and reception while changing the position by the scanning mechanism 5. The transmitting and receiving unit 2 supplies a driving pulse to the probe 1,
Then, the signal received from the probe 1 is amplified and digitized. The aperture synthesis processing unit 3 includes a reception waveform memory 6, a position information memory 10, a sound field information memory 11, a group delay amount correction unit 7, a carrier phase correction unit 8, a signal addition unit 9, and a switch control unit 2.
1 and switches 18 and 19. The reception waveform memory 6 stores a high-frequency reception signal from the transmission / reception unit 2, the position information memory 10 stores the position information of the probe 1, and the sound field information memory 11 radiates from the probe 1. Sound field information such as phase delay and group delay of sound waves is stored. The position information of the probe 1 corresponds to a received signal obtained by one transmission / reception. The group delay amount correction unit 7 corrects the group delay amount by giving a predetermined delay to the received signal. Carrier phase correction unit 8
Corrects the phase of the carrier of the received signal. During the aperture synthesis processing, the switch control unit 21 determines whether the frequency characteristic of the sound velocity at the position to be obtained from the sound field information and the position information of the probe 1 is completely or negligible.
Operate 8 and 19 to disconnect the carrier phase corrector. The signal adder 9 adds the received signals after the correction of the group delay amount and the phase delay amount. The image display unit 4 converts the synthesized signal output from the aperture synthesis processing unit 3 into a video signal such as a TV and displays the video signal on a display device such as a monitor.

As described above, according to the fourth embodiment of the present invention, the switches 18 and 1 are provided before and after the phase delay correction unit 8.
9 are controlled by the switch control unit 21 so that a region where the frequency characteristic of the sound velocity is large and a region where the frequency characteristic of the sound speed is completely absent or negligible are mixed. Whether or not to correct the amount can be switched, and the amount of calculation for correcting the amount of phase delay can be reduced.

(Embodiment 5) FIG. 6 shows a probe 1 having a wavefront control means according to Embodiment 5 of the present invention and characteristics of a sound field generated by a sound wave radiated from the probe 1. .
The probe 1 has an acoustic lens 25 as wavefront control means, and converges emitted ultrasonic waves to a focal point 26. At this time, the sound field generated by the ultrasonic wave is divided into a main lobe region 27 where the sound wave converges to the focal point 26 and a side lobe region 28 where the sound wave diffuses in all directions. The sound wave in the main lobe region 27 can be regarded as a spherical wave centered on the focal point, and the frequency dependence of the sound velocity can be ignored. Therefore, when the position to be obtained is in the main lobe area 27, only the group delay amount is corrected, and the calculation of the carrier phase correction amount can be omitted. The sound waves in the side lobe region 28 differ in the degree of diffusion depending on the frequency, so that the sound speed has frequency dependence. Therefore, the position to be obtained is determined by the side lobe region 28.
In this case, it is necessary to correct both the group delay amount and the carrier phase delay amount.

As described above, according to Embodiment 5 of the present invention, when a probe having wavefront control means is used,
Since a region where the frequency dependence of the sound velocity is negligible and a region where the frequency dependence is not negligible occur, from the positional relationship between the position to be obtained and the probe, if the position to be obtained is within the side lobe region 28, the group delay amount If both the phase delay amounts are corrected and the position to be obtained is within the main lobe area 27, the amount of calculation for phase correction can be reduced by disconnecting the carrier phase correction unit.

In the above description, the acoustic lens is used as the wavefront control means. However, the present invention is not limited to this. A wavefront control means using a convex vibrator or a concave vibrator, and further controlling the wavefront by electronic means. The same can be applied to those which have been implemented.

[0024]

As described above, according to the present invention, it is possible to perform strict aperture synthesis close to the characteristics of the sound field created by the medium or the ultrasonic probe actually used. Good azimuth resolution independent of distance can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram for explaining the operation of the ultrasonic diagnostic apparatus according to the first embodiment of the present invention.

FIG. 3 is a block diagram of an ultrasonic diagnostic apparatus according to Embodiment 2 of the present invention.

FIG. 4 is a block diagram of an ultrasonic diagnostic apparatus according to Embodiment 3 of the present invention.

FIG. 5 is a block diagram of an ultrasonic diagnostic apparatus according to Embodiment 4 of the present invention.

FIG. 6 is a block diagram of an ultrasonic diagnostic apparatus according to Embodiment 5 of the present invention.

FIG. 7 is a block diagram of a conventional ultrasonic diagnostic apparatus using the aperture synthesis method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 probe 2 transmission / reception circuit 3 reception waveform memory 4 signal processing unit 5 screen display unit 6 scanning mechanism 7 group delay correction unit 8 phase delay correction unit 9 signal addition unit 10 position information memory 11 sound field information memory 12 delay circuit 13 FET Circuit 14 Multiplying circuit 15 IFFT circuit 16 Group delay correction amount calculation unit 17 Carrier phase correction amount calculation unit 18, 19 Switch 20 Control unit 21 Switch control unit

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

Claims (5)

[Claims] 1. An ultrasonic probe, means for controlling the position of the ultrasonic probe, means for storing a received reflected signal, and correction of a group delay by giving a predetermined delay to the signal Means, a means for correcting the phase of the carrier of the signal, and a means for adding the signal, in an ultrasonic diagnostic apparatus that reconstructs a tomographic image by aperture synthesis, the phase adjustment method of the received signal in aperture synthesis, An ultrasonic diagnostic apparatus that performs both correction of a group delay amount of a received reflected signal and correction of a phase delay amount of a carrier wave. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the means for correcting the phase of the carrier wave performs the correction by performing orthogonal transformation processing on the received signal. 3. The ultrasonic diagnostic apparatus according to claim 1, further comprising means for arbitrarily switching whether or not to correct the phase delay amount of the carrier. 4. The ultrasonic diagnostic apparatus according to claim 1, further comprising means for switching whether to correct the phase delay amount of the carrier during the aperture synthesis processing. 5. An ultrasonic diagnostic apparatus having an ultrasonic probe having a wavefront control means, which determines whether or not to correct a phase delay amount of a carrier wave according to a positional relationship between a position to be obtained and a probe. 5. The ultrasonic diagnostic apparatus according to claim 4, further comprising switching means.