JP2001340339A - Ultrasonic diagnosing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extract the higher harmonic component of a receiving signal in an ultrasonic diagnosis by a comparatively simple means without increasing an imaging period of time. SOLUTION: The receiving signal (a) is output from a phasing circuit 3 which performs a receiving focus process for a receiving wave being output from an ultrasonic probe l. A delayed receiving signal (b) is obtained by delaying the receiving signal (a), e.g. by a period of time being equivalent to the 1/2 wavelength of a basic wave component by a delaying circuit 4. The receiving signal (a) and the delayed receiving signal (b) are added by an adding apparatus 5, and the basic wave component is eliminated or reduced, and thus, a receiving signal comprising the higher harmonic component is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an ultrasonic diagnostic apparatus.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus transmits an ultrasonic wave to a subject, receives a reflected wave thereof, and forms an image of each part of the subject based on acoustic characteristic information of the subject included in the received signal. It is widely known that a subject is diagnosed based on the image.

Conventionally, in such an ultrasonic diagnostic apparatus, in order to improve the azimuth resolution, a harmonic component corresponding to a fundamental frequency of a transmission wave is extracted from a received signal to generate a diagnostic image. Proposed. That is, since the harmonic component has a shorter wavelength than the fundamental component, the azimuth resolution can be improved.

As a method of extracting a harmonic component from a received signal, for example, a received signal is processed by a band-pass filter to extract a desired harmonic component. As another method, two ultrasonic waves whose phases are inverted are transmitted to the subject with a time lag, the reflected waves are received and added, and the fundamental wave component is canceled, thereby obtaining a harmonic component. (Japanese Patent Laid-Open No. 11-342130).

According to the above-mentioned prior art, there are the following problems. That is, the method of extracting a harmonic component using a bandpass filter requires a narrow and steep characteristic of the passband as the characteristic of the bandpass filter. Therefore, there are problems that the circuit configuration of the bandpass filter becomes complicated and the circuit scale increases. Also, due to the narrow band bandpass filter characteristics,
Range resolution may be reduced. Further, when the phasing circuit for performing the reception focusing is an analog ultrasonic diagnostic apparatus, desired characteristics may not be obtained in some cases.
On the other hand, if the pass band characteristics of the band-pass filter are poor, there is a problem that the removal of the fundamental wave component may be insufficient, and the quality of the generated image deteriorates.

On the other hand, in the case of a method in which two ultrasonic waves whose phases are inverted are transmitted to a subject with a time delay and the received signals of the reflected waves are added to cancel the fundamental wave component, one ultrasonic wave is used. In order to collect the acoustic characteristics on the sound beam, two transmissions and receptions of ultrasonic waves must be performed. Therefore, there is a problem that the measurement time or the photographing time is doubled, and the frame rate of the image is reduced.

An object of the present invention is to extract a harmonic component of a received signal by a relatively simple means without increasing the imaging time.

[0007]

In order to solve the above-mentioned problems, an ultrasonic diagnostic apparatus according to the present invention comprises: an ultrasonic probe for transmitting and receiving ultrasonic waves; and a transmission of a transmission wave to be transmitted to the ultrasonic probe. Transmitting means for performing a focus process, phasing means for performing a reception focus process of a reception wave output from the ultrasonic probe, and a time-shifted reception signal output from the phasing means, A harmonic extraction unit that extracts a harmonic of the received signal by adding or subtracting a signal that is not shifted, and an image processing unit that generates an image based on a signal output from the harmonic extraction unit. It is characterized by the following.

That is, utilizing the difference between the frequency of the harmonic component and the frequency of the fundamental wave component, the fundamental wave component is obtained by a simple process of adding or subtracting a time-shifted received signal and a non-shifted received signal. Can be reduced, so that harmonic components can be extracted. In addition, since the acquisition of acoustic characteristics on one ultrasonic beam can be performed by one ultrasonic transmission / reception, there is no need to increase the imaging time.

The harmonic extraction means adds or subtracts a reception signal output from the phasing means and a delayed reception signal obtained by variably adjusting the reception signal to add or subtract a harmonic component of the reception signal. May be extracted.

That is, when the received signal delayed by the delay means and the original signal not delayed are added or subtracted,
The fundamental wave component is canceled according to the delay time. Therefore, by adjusting the delay time, the fundamental wave component of the received signal can be substantially removed. Specifically, the delay time is variably adjusted so that the fundamental component of the received signal output from the harmonic extraction means is sufficiently small.

For example, it is desirable to delay the received signal output from the phasing means by a time corresponding to a half wavelength of the fundamental wave component of the received signal. That is, the phase of the fundamental wave component is shifted by 180 ° between the received signal output from the phasing means and the signal obtained by delaying the received signal by time corresponding to １ ／ wavelength of the fundamental wave component (center frequency). Become a relationship. Therefore, when the two received signals are added, the fundamental wave component is canceled and removed. On the other hand, for example, a double harmonic component has a phase shifted by 360 ° and signals of the same polarity are added, so that a harmonic component having a large amplitude can be extracted. As a result, it is possible to collect acoustic characteristics on one ultrasonic beam by one transmission and reception of ultrasonic waves, and it is not necessary to increase the photographing time. The signal delay means can be realized by a simple circuit or the like as compared with a means for extracting a harmonic component using a band-pass filter.

Here, it is known that the frequency of the ultrasonic reception signal changes depending on the reflection position (reception depth) of the ultrasonic wave in the subject. Further, the frequency that changes depending on the reception depth can be obtained in advance by measurement or the like. Therefore, it is desirable that the half wavelength of the fundamental wave component of the received signal be changed according to the reception depth.

On the other hand, when the frequency change due to the reception depth does not cause much problem, the above-mentioned delay time may be set to a time corresponding to a half wavelength of the fundamental wave component of the transmission ultrasonic wave.

According to another aspect of the present invention, there is provided a low-pass filter for receiving a signal output from a phasing means for performing a reception focusing process on a reception wave output from an ultrasonic probe. By passing only the fundamental wave component of the received signal through and providing a subtraction means for calculating the difference between the fundamental signal and the received signal output from the phasing means, only the harmonic component may be extracted.

According to another aspect of the present invention, it is possible to collect acoustic characteristics on one ultrasonic beam by one transmission and reception of ultrasonic waves, and it is not necessary to increase the photographing time.
Further, the low-pass filter can be realized by a simple circuit or the like as compared with the band-pass filter.

In the above description, the transmission focus processing is to transmit a drive signal to be transmitted to each of the ultrasonic transducers so that the times at which ultrasonic waves emitted from the plurality of ultrasonic transducers reach the set focal point are matched. It refers to a function of controlling time, and the reception focus processing refers to a function of matching and adding phases of reception waves output from a plurality of ultrasonic transducers.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention. As shown in FIG. 1, the ultrasonic diagnostic apparatus includes an ultrasonic probe 1, an ultrasonic transmitting / receiving circuit 2, a phasing circuit 3, a delay circuit 4, an adder 5,
, A signal processing unit 6, an image processing unit 7, and a monitor 8.

Although not shown, the ultrasonic probe 1 is formed by arranging a plurality of ultrasonic transducers in a strip shape, and is used in close contact with the surface of the subject. Each ultrasonic transducer generally has a function of converting a transmission wave signal (also referred to as a driving pulse) of an input pulse-like electric signal into an ultrasonic wave and emitting the ultrasonic wave to the subject, and reflecting from the inside of the subject. It is formed to have a function of receiving an ultrasonic wave (also called a reception echo), converting it into a reception signal of an electric signal, and outputting the signal.

The ultrasonic transmission / reception circuit 2 includes an ultrasonic transmitter,
It is formed to include an ultrasonic transmission processing circuit, an ultrasonic receiving circuit, and the like. Transmission processing circuit of the ultrasound has a function of transmitting the transmission wave signal of the fundamental frequency f ₀ output from the ultrasonic transmitter, in each of the plurality of ultrasonic transducers.
That is, as is well known, each ultrasonic wave emitted from a plurality of ultrasonic transducers arranged in a strip shape is adjusted so that the ultrasonic waves emitted from a plurality of ultrasonic transducers reach one focal point in the subject which is variably set. It has a function of controlling the transmission timing (phase) of the transmission wave signal transmitted to the vibrator. The ultrasonic receiving circuit has a function of receiving and amplifying a plurality of reception signals output from the plurality of ultrasonic transducers separately from a transmission wave signal. From the ultrasonic transmission / reception circuit 2, a number of reception signals corresponding to the number of channels of the ultrasonic transducer are output to the phasing circuit 3 as independent reception signals.

The phasing circuit 3 takes in the received signal output from the ultrasonic transmission / reception circuit 2 and converts it into a digital signal. Then, contrary to the above-described transmission processing circuit, the phasing circuit 3 receives the signal from one focal point in the subject. In order to eliminate the time lag between the reflected waves emitted and the ultrasonic transducers arranged in a strip,
It has a function to adjust the phases of the received signals output from the respective ultrasonic transducers by a delay circuit or the like to match them, and to add a plurality of matched received signals to obtain acoustic characteristic information from one focal point. are doing. In other words, the phasing circuit 3 is a circuit for performing a so-called focus process, and a process of matching the phases of reception waves output from a plurality of ultrasonic transducers, phasing and adding them, and forming a reception beam signal. Has a function.

The received signal a output from the phasing circuit 3 is
The signal is input to the delay circuit 4 and the adder 5. The delay circuit 4 delays the input reception signal a by a set time, and
Is output to the adder 5. This delay circuit
The high frequency extracting means is formed by the adder 4 and the adder 5.
The set delay time of this embodiment is the fundamental wave component of the received signal.
The time is set to a time corresponding to a half wavelength of (center frequency).

The adder 5 adds the received signal a output from the phasing circuit 3 and the delayed received signal b output from the delay circuit 4 to obtain a received signal c of a harmonic component from which a fundamental component has been removed. Output to the signal processing unit 6. The signal processing unit 6 subjects the received signal c of the harmonic component to filtering processing for removing unnecessary frequency components and signal processing such as necessary compression processing, detection processing, enhancement, and the like, and the image processing unit 7
Output to The image processing unit 7 has a function of a digital scan converter (DSC), converts a received signal of a higher harmonic component into image data, outputs the image data, and outputs the image data.
Is to be drawn.

Next, the operation of the harmonic extraction means comprising the delay circuit 4 and the adder 5 which is a feature of the embodiment of FIG. 1 constructed as described above will be described with reference to the waveforms shown in FIGS. This will be described with reference to the drawings. 2 to 4, the horizontal axis represents the depth of focus (time), and the vertical axis represents the amplitude of the received signal. The delay circuit 4 receives the received signal a (FIG. 2)
Is a half wavelength of the fundamental wave component of the received signal a (180
°). As a result, the delayed reception signal b (FIG. 3) output from the delay circuit 4 becomes the reception signal a
, The phase of the fundamental wave component is shifted by 180 °. Therefore, when the two received signals are added by the adder 5, the fundamental wave component is canceled out and removed, and a received signal c having a harmonic component as a main component is obtained as shown in FIG. That is, for example, the harmonic component having a frequency twice as high as the fundamental wave component is shifted in phase by 360 ° by the delay circuit 4, so that signals having the same polarity are added in the adder 5, so that a large amplitude is obtained. Can be extracted. The reason for using the harmonic component of the double frequency is as follows.
This is because the signal intensity is higher than the harmonic components of other orders.

As described above, according to the embodiment of FIG. 1, it is possible to collect acoustic data on one ultrasonic beam by transmitting and receiving ultrasonic waves once, and to reduce the photographing time. No need to increase. The delay circuit 4 can be realized by a simple circuit or the like as compared with a circuit that extracts a harmonic component using a bandpass filter. As a result, an image can be generated based on the harmonic components while maintaining the frame rate of the image, so that a high-quality ultrasonic image with high azimuth resolution can be captured.

FIG. 5 is a diagram for explaining a comparison between the frame rate of the present invention and that of the prior art. FIG. 1A is a time chart for collecting sound data according to the present invention, and FIG. 2B is a time chart for collecting sound data according to Japanese Patent Laid-Open No. 11-342130. As shown in FIG. 1A, according to the present invention, acoustic data on one ultrasonic beam can be collected by one launch and reception of ultrasonic waves, whereas in the related art, According to this, unless two ultrasonic waves having a normal phase and a negative phase are emitted and received with a time delay, acoustic data on one ultrasonic beam cannot be collected. As a result, according to the present invention, it is possible to perform imaging at twice the rate of the related art within the same time.

The delay circuit 4 of the above-described embodiment sets the set delay time to １ ／ of the fundamental wave component (center frequency) of the received signal a.
The example of setting the time corresponding to the wavelength has been described. Here, it is known that the frequency of the ultrasonic reception signal changes (shifts) depending on the reflection position (reception depth) of the ultrasonic wave in the subject. The frequency that shifts according to the reception depth can be obtained in advance by measurement or the like. Therefore, it is desirable that the half wavelength of the fundamental wave component of the received signal be changed according to the reception depth.

The delay time can be varied in response to a command from a control device for controlling the entire ultrasonic diagnostic apparatus. For example, the time from when the ultrasonic wave is emitted from the ultrasonic oscillator to the subject until the echo is received by the ultrasonic oscillator is counted by a counter or the like, and based on the relationship between the time and the frequency shift, The center frequency of the received signal can be obtained.

However, when the frequency shift due to the reception depth does not cause much problem, the above-mentioned delay time may be set to a time corresponding to a half wavelength of the fundamental wave component of the transmitted ultrasonic wave.

Further, the delay time of the delay circuit 4 can be varied, and the adder 5 has a function of adding or subtracting the delayed reception signal output from the delay circuit 4 and the reception signal output from the phasing circuit 3. It is preferable to replace with arithmetic means. According to this, the delayed reception signal b delayed by the delay circuit 4 and the reception signal a that is the original signal that has not been delayed
Is added or subtracted, the fundamental wave component is reduced according to the degree of the delay time. Therefore, by adjusting the delay time, the fundamental wave component of the received signal can be substantially removed. That is, the fundamental component of the received signal c output from the calculating means is detected, and the delay time is variably adjusted so that the fundamental component is sufficiently small. The detection of the fundamental wave component of the received signal c can be easily realized by a low-pass filter.

In short, according to the present invention, as described in the above embodiments and modifications, a signal obtained by temporally shifting the received signal output from the phasing means and a signal not shifted are added or subtracted. The purpose of the present invention is to extract the harmonics of the received signal by using simple means such as delay means and addition / subtraction means. 1 by launch and reception
Acquisition of acoustic data on two ultrasonic beams
Compared with the conventional technology by launching and receiving ultrasonic waves twice,
The frame rate can be improved. (Second Embodiment) FIG. 6 is a block diagram showing an ultrasonic diagnostic apparatus according to another embodiment of the present invention. As shown in FIG. 1, the ultrasonic diagnostic apparatus includes an ultrasonic probe 11, an ultrasonic transmission circuit 12, an ultrasonic reception circuit 13, and a phasing circuit unit 1.
4, a low-pass filter unit 15, a subtraction circuit unit 16,
Ultrasonic signal processing unit 17, image processing unit 18, monitor 1
9 is provided.

The probe 11 has the same functional configuration as the ultrasonic probe 1 of FIG. Also, the ultrasonic transmission circuit 12
The ultrasonic receiving circuit 13 corresponds to the ultrasonic transmitting / receiving circuit 2 in FIG. The phasing circuit 14, the ultrasonic signal processing unit 17, the image processing unit 18, and the monitor 19 have functional configurations corresponding to the phasing circuit 3, the signal processing unit 6, the image processing unit 7, and the monitor 8, respectively, of FIG. Have.

Here, the low-pass filter section 15 and the subtraction circuit 16 which are characteristic parts of the present embodiment will be described together with the operation. The low-pass filter unit 15 is set to have a frequency characteristic of passing a frequency component of a fundamental component of the received signal a and a frequency component lower than the fundamental component and cutting a harmonic component. As a result, the low-pass filter unit 15 removes harmonic components of the input received signal a (FIG. 7), and outputs a signal mainly composed of a fundamental wave component (referred to as a fundamental wave component) d (FIG. 8).
Is output to the subtraction circuit unit 16. The subtraction circuit 16 calculates the difference between the received signal a and the fundamental wave component signal d, thereby obtaining the received signal e of the harmonic component of the received signal a (FIG. 9).
Is input to the ultrasonic signal processing circuit 17. The following operation is the same as in the embodiment of FIG.

As described above, according to the embodiment shown in FIG.
Acquisition of acoustic data on one ultrasonic beam can be performed by one ultrasonic transmission / reception, and there is no need to increase the imaging time. The desired cut-off frequency characteristic of the low-pass filter section 15 can be realized by a simple circuit or the like as compared with a band-pass filter. As a result, an image can be generated based on the harmonic components while maintaining the frame rate of the image, so that a high-quality ultrasonic image with high azimuth resolution can be captured.

[0034]

As described above, according to the present invention, it is possible to extract a harmonic component of a reception signal for an ultrasonic diagnosis by a relatively simple means without increasing the imaging time. This has the effect.

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram of a reception signal a output from the phasing circuit of FIG. 1;

FIG. 3 is a waveform diagram of a delayed reception signal b output from a delay circuit 4 of FIG. 1;

FIG. 4 is a waveform diagram of a reception signal c as a result of addition output from the adder 5 of FIG. 1;

FIG. 5 is a time chart for explaining the difference between the frame rate of the present invention and that of the prior art.

FIG. 6 is a block diagram of another embodiment of the ultrasonic diagnostic apparatus of the present invention.

7 is a waveform diagram of a reception signal a output from the phasing circuit unit of FIG.

8 is a waveform diagram of a reception signal d output from the low-pass filter unit 15 in FIG.

9 is a waveform diagram of a reception signal e output from the subtraction circuit unit 16 in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ultrasonic probe 2 ultrasonic transmission / reception circuit 3 phasing circuit 4 delay circuit 5 adder 6 signal processing section 7 image processing circuit section 8 monitor 15 low-pass filter section 16 subtraction circuit section

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsuya Hayashi 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Medical Corporation (72) Inventor Akira Sasaki 1-14-1 Uchikanda, Chiyoda-ku, Tokyo No. F-term in Hitachi Medical Corporation (reference) 2G047 EA09 GF21 GF22 GG27 GG34 4C301 EE07 HH31 JB29 JB50

Claims (7)

[Claims] An ultrasonic probe for transmitting and receiving an ultrasonic wave, transmission means for performing transmission focus processing of a transmission wave transmitted to the ultrasonic probe, and a reception wave output from the ultrasonic probe Phasing means for performing reception focusing processing, and harmonics for extracting a harmonic of the received signal by adding or subtracting a temporally shifted received signal output from the phasing means and a non-shifted received signal. An ultrasonic diagnostic apparatus comprising: a wave extracting unit; and an image processing unit that generates an image based on a signal output from the harmonic extracting unit. 2. An ultrasonic probe for transmitting and receiving ultrasonic waves, transmission means for performing transmission focus processing of a transmission wave transmitted to the ultrasonic probe, and a reception wave output from the ultrasonic probe Phasing means for performing reception focusing processing, and adding or subtracting a reception signal output from the phasing means and a delayed reception signal obtained by variably adjusting the reception signal to obtain a harmonic of the reception signal. An ultrasonic diagnostic apparatus comprising: a harmonic extraction unit that extracts a component; and an image processing unit that generates an image based on a signal output from the harmonic extraction unit. 3. The apparatus according to claim 2, wherein the harmonic extracting means adjusts a delay time so as to reduce a fundamental component of the received signal output from the harmonic extracting means.
An ultrasonic diagnostic apparatus according to item 1. 4. The harmonic extracting means includes delay means for delaying the received signal, and the delay means corresponds to a half wavelength of a fundamental wave component of the received signal output from the phasing means. 3. The ultrasonic diagnostic apparatus according to claim 2, wherein the ultrasonic diagnostic apparatus delays the time. 5. The ultrasonic diagnostic apparatus according to claim 4, wherein a wavelength of a fundamental component of the received signal is adjusted according to a receiving depth. 6. The harmonic extraction means includes delay means for delaying the reception signal, and the delay means transmits a reception signal output from the phasing means to a transmission signal transmitted to the ultrasonic probe. The ultrasonic diagnostic apparatus according to claim 2, wherein a time delay corresponding to a half wavelength of a fundamental component of the wave is delayed. 7. An ultrasonic probe for transmitting and receiving ultrasonic waves, transmitting means for performing transmission focus processing of ultrasonic waves transmitted to the ultrasonic probe, and a reception wave output from the ultrasonic probe Phasing means for performing reception focus processing, a low-pass filter to which a reception signal output from the phasing means is input, and a reception signal output from the low-pass filter and a reception signal output from the phasing means. An ultrasonic diagnostic apparatus comprising: subtraction means for obtaining a difference; and image processing means for generating an image based on a signal output from the subtraction means.