JPH0723960A - Ultrasonographic device - Google Patents

Abstract

PURPOSE:To eliminate image distortion by making the bearing resolution and distance resolution of an ultrasonogram obtained approximately equal. CONSTITUTION:A wave-transmission weighting control circuit 16 for adjusting the signal band of a signal indicating transmission of an ultrasonic wave for a transmitter driver 2 is provided, and the bearing resolution and distance resolution of an ultrasonogram obtained are made roughly equal by the action of the wave-transmission weighting control circuit 16. As a result, distortion of the ultrasonogram can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnosis in which ultrasonic waves are used to obtain a tomographic image of a diagnostic region of a subject and to perform so-called weighting on either or both of ultrasonic wave transmission and reception. More specifically, the present invention relates to an ultrasonic diagnostic apparatus capable of eliminating distortion of an image by substantially equalizing the azimuth resolution and the distance resolution of the obtained ultrasonic image.

[0002]

2. Description of the Related Art A conventional ultrasonic diagnostic apparatus of this type is shown in FIG.
As shown in FIG. 2, a wave transmitting means (1, 2, 3) for transmitting an ultrasonic pulse or an ultrasonic continuous wave into the subject, and a reflected wave from a diagnostic site in the subject are received and amplified. A wave receiving means (4,5), a focus circuit (6, 7) for focusing the beam by inputting the wave received signal amplified by the wave receiving means, and a signal compression and an envelope for the wave received signal from the focus circuit. A post-processing circuit 8 for performing line detection, an image processing means (9, 10, 11) for inputting an output signal from the post-processing circuit 8 to perform A / D conversion and processing for image display, and this image. It comprises display means (12, 13) for inputting the image signal from the processing means and displaying it as an image, and reception weighting means (14) for changing the amplitude of the reception signal in units of each channel or a plurality of channels. Was there. In FIG. 7, reference numeral 15 indicates a controller that controls the operation of each of the above components.

Here, in FIG. 7, a weight control circuit 1 as a received wave weighting means is used as a weighting means.
Only 4 is shown. The weight control circuit 14 inputs a signal obtained by switching the probe 1 output from the controller 15 according to, for example, the depth, and reads a prestored weight function according to the type of the probe 1. And
It comprises a storage means such as a ROM for storing the weighting function and a latch for holding the data for distributing the weighting function to each channel of the received signal. Then, the weight control circuit 14
The weighting function output from the above was sent to the preamplifier 5 of each channel for amplifying the received signal.
Incidentally, as a conventional ultrasonic diagnostic apparatus having a weighting function for transmitting or receiving waves, there are JP-A-3-222945 and JP-A-3-222945.
There is one described in the publication of 3-261466.

[0004]

However, in the conventional ultrasonic diagnostic apparatus shown in FIG. 7, only the relationship between the weighting function of transmitting or receiving weighting and the lateral resolution of the obtained ultrasonic image is considered. However, no consideration was given to the balance between the azimuth resolution and the range resolution in an ultrasonic pulse having a frequency band. That is, when the band is narrowed, the ultrasonic beam becomes thin and the lateral resolution is improved. However, if the azimuth resolution is further improved to a certain extent, the distance resolution tends to decrease accordingly. On the other hand, conventionally, since the balance between the azimuth resolution and the distance resolution is not considered as described above, only the azimuth resolution may be improved. As a result, for example, the image of a round dot does not look round, and the image is distorted, so that the situation of the diagnosis site may not be recognized correctly.

Therefore, the present invention addresses such problems and provides an ultrasonic diagnostic apparatus capable of eliminating image distortion by making the azimuth resolution and distance resolution of the obtained ultrasonic image substantially equal. With the goal.

In order to achieve the above-mentioned object, the ultrasonic diagnostic apparatus according to the present invention comprises a transmitting means for transmitting an ultrasonic pulse or an ultrasonic continuous wave into a subject, and reflection from a diagnostic site in the subject. A wave receiving means for receiving and amplifying a wave, a focus circuit for inputting the wave receiving signal amplified by the wave receiving means to focus the beam, and a signal compression and envelope detection for the wave receiving signal from the focus circuit. A post-processing circuit for performing the following, an image processing means for inputting an output signal from the post-processing circuit, performing A / D conversion and processing for image display, and an image signal for inputting an image signal from the image processing means. And a display weighting means for changing the amplitude of the transmission pulse for each channel or a plurality of channels, or a reception weighting means for changing the amplitude of the reception signal, or both. In the wave diagnostic apparatus, the means for adjusting the signal band of the ultrasonic wave transmission signal or reception signal provided to the lateral resolution and distance resolution of the ultrasound image obtained is obtained so as to substantially equal.

The signal band adjusting means narrows the signal band of the transmitted signal or the received signal.

Further, the signal band adjusting means is provided with a means for varying the wave number of the transmitted ultrasonic pulse to narrow the signal band of the transmitted signal.

Furthermore, the signal band adjusting means is provided with a band pass filter for the received signal to narrow the signal band of the received signal.

The means for adjusting the signal band of the transmitted signal or the received signal has a plurality of means having different adjustment conditions, and the adjustment condition of the signal band depends on the type of the probe used. Is provided with a means for switching.

[0011]

The ultrasonic diagnostic apparatus thus constructed is provided with means for adjusting the signal band of the transmitted signal or the received signal so that the azimuth resolution and the distance resolution of the obtained ultrasonic image are substantially equal. To work. As a result, the distortion of the obtained ultrasonic image can be eliminated.

[0012]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus obtains a tomographic image of a diagnostic region of a subject using ultrasonic waves, and performs so-called weighting with either or both of ultrasonic wave transmission and reception, and in FIG. The probe 1 electronically performs beam scanning to transmit and receive ultrasonic waves into the subject, and although not shown, the probe 1 is a source of ultrasonic waves and reflects the ultrasonic waves. A multi-channel transducer element that receives the echo is provided. The wave transmission driver 2 supplies the pulse necessary for driving each transducer element in the probe 1 to transmit an ultrasonic wave to the probe 1 at a predetermined timing. There are provided as many channels as the transducer elements.
The transmission weight control circuit 16 controls the generation timing of the transmission pulse transmitted from the transmission driver 2 to the probe 1, and focuses the ultrasonic wave transmitted from the probe 1. In addition to giving a phase difference between the respective channels, the transmission driver 2 is controlled in gain and delay time according to a predetermined weighting function and focus. The probe 1, the transmission driver 2, and the transmission weight control circuit 16 constitute a transmission means for transmitting an ultrasonic pulse or an ultrasonic continuous wave into the subject.

The limiter 4 serves as an entrance for taking in the received wave signal received by the probe 1, and is composed of, for example, a diode to limit a high voltage signal from the wave sending side. The preamplifier 5 amplifies the received signal of the probe 1 input via the limiter 4, and its gain is a variable gain amplifier that changes according to a control signal from the outside. There are provided as many channels as the transducer elements. And the limiter 4
The preamplifier 5 and the preamplifier 5 constitute a wave receiving unit that receives and amplifies the reflected wave from the diagnosis site in the subject.

The focus circuit 6 receives the received signal amplified by the above-mentioned receiving means and focuses the beam. For example, the focus circuit 6 includes an analog delay element such as an LC delay line or an A / D converter and a storage element. It is composed of a combination of digital delay means and the like, and is provided by the number of channels of the transducer elements of the probe 1, and there is a delay time difference between the channels in order to focus the received signal into a beam. It is like this. The deflection circuit 7 deflects the received signal output from the focus circuit 6,
For example, it is composed of an LC delay line or the like, and has a delay time difference between the respective channels so as to appropriately deflect the received signal. The focus circuit 6 is A /
When the D converter and the storage element are combined, the focus circuit 6 and the deflection circuit 7 are generally configured so that their functions are combined.

The post-processing circuit 8 performs signal compression and envelope detection on the received signal processed by the focus circuit 6 and output through the deflection circuit 7, and is composed of, for example, a LOG compression circuit and a detection circuit. .

The A / D converter (ADC) 9 converts the output signal from the post-processing circuit 8 into a digital signal. The buffer memory 10 temporarily stores the image signal output from the ADC 9, and stores the image signal in units of ultrasonic scanning lines.
Further, the image memory 11 reads out the image signal once stored in the buffer memory 10 and stores the image signal for image display, so that the image signals in units of ultrasonic scanning lines are sequentially fetched and written in time series. It has become. Then, the ADC 9, the buffer memory 10, and the image memory 1
1 and inputs the output signal from the post-processing circuit 8 to A
An image processing unit configured to perform D / D conversion and image display is configured.

The image display circuit 12 receives the signal read from the image memory 11 and processes the signal so as to match the format of the next display unit 13. Further, the display 13 is the image display circuit 12 described above.
The image signal output from the device is input to display an ultrasonic image, and is composed of, for example, a television monitor. The image display circuit 12 and the display 13 constitute a display means for inputting the image signal from the image processing means and displaying it as an image. In FIG. 1, reference numeral 15 indicates a controller that controls the operation of each of the above components.

Here, the present invention is characterized in that the transmission weight control circuit 16 is connected to the transmission driver 2. The transmission weight control circuit 16 serves as means for adjusting the signal band of the ultrasonic transmission signal, and by narrowing the signal band of the transmission signal, the azimuth resolution of the obtained ultrasonic image is obtained. And the distance resolution are substantially equal to each other, and the internal configuration is as shown in FIG.
Probe ROM 17, focus control circuit 18, and wave number control circuit 1 as means for varying the wave number of the transmitted pulse
9, a plurality of latches 20a to 20n, and a frequency divider circuit 21.
, First and second selection circuits 22a and 22b, first and second shift registers 23a and 23b, first and second array switches 24a and 24b, a launch period setting circuit 25, and a wave number And a setting circuit 26. The transmission control signal output from the transmission weight control circuit 16 is transmitted to the transmission driver 2 of each channel.

Next, the operation of the ultrasonic diagnostic apparatus configured as described above will be described. First, in FIG. 1, the probe 1 is brought into contact with the surface of the subject, and ultrasonic waves are transmitted to the diagnosis site. At this time, the ultrasonic waves to be scanned are controlled by the wave transmission weight control circuit 16 so as to form a thin beam at the diagnosis site, and then the wave transmission driver 2 searches for a pulse required to drive each transducer element. Supply to the tentacle 1. The reflected wave from the living body of the transmitted beam is received by the probe 1. Then, the limiter 4 limits the unnecessary high voltage signal from the transmitting side, and the preamplifier 5 amplifies the received signal. At this time, each channel of the preamplifier 5 has a certain gain and delay time. And
From the probe 1, ultrasonic wave transmission / reception directions are sequentially changed at a predetermined cycle and ultrasonic wave transmission / reception is repeatedly performed so as to ultrasonically scan a diagnostic region, or continuous ultrasonic waves are transmitted. It is transmitted.

Next, the received signal amplified by the preamplifier 5 is sequentially input to the focus circuit 6 and the deflection circuit 7. The signal that has been focused by the focusing circuit 6 and deflected by the deflection circuit 7 is LOG-compressed and envelope-detected by the post-processing circuit 8, and the ADC 9
Is converted into a digital signal and stored in the buffer memory 10 in units of ultrasonic scanning lines. Next, the data for each scanning line is sent to the image memory 11, and written and read so that one ultrasonic tomographic image is formed by making the transmitting and receiving directions correspond to each ultrasonic beam. Then, the image display circuit 12 performs analog conversion by an internal D / A converter adjusted to the timing necessary for the display 13 and the image signal is displayed on the display 13. It should be noted that the controller 15 adjusts the ultrasonic transmission / reception timing,
It controls transmission such as transmission focus, reception control such as reception focus, and writing / reading control of each memory.

Next, the operation of the transmission weight control circuit 16 will be specifically described with reference to FIGS. First, from among the focus data and pulse width data stored in the internal probe ROM 17 as initial settings, and wave number data previously obtained by calculation or experiment so that the azimuth resolution and the distance resolution are substantially equal, As shown in FIG. 1, the data corresponding to the probe 1 connected to the apparatus is read out and sent to the focus control circuit 18 and the wave number control circuit 19. Each of the focus control circuit 18 and the wave number control circuit 19 has a built-in storage device such as a RAM. The focus data and the pulse width data are held in the focus control circuit 18, and the wave number data is the wave number control circuit 19. Retained within.

On the other hand, a clock signal is sent from the controller 15 shown in FIG. 1, and this clock signal is input to the internal frequency dividing circuit 21 and the first and second shift registers 23a and 23b. The cycle of this clock signal is the minimum unit of the delay difference of each channel required for transmission focusing. The frequency dividing circuit 21 divides the frequency of the clock signal to generate a signal having the same period as the launching period of the transmitted wave. At this time, the launch cycle may be different for each mode such as the frame rate of the ultrasonic image, the B mode, and the PW mode, so a plurality of types of signals are created and sent to the first selection circuit 22a. Then, the first selection circuit 22a
Selects a clock signal that matches a predetermined launch cycle with an internal selector and sends it to the first shift register 23a. In the first shift register 23a, the m number of signals obtained by shifting the clock signal sent from the controller 15 in units of one cycle are used in the first array switch 2
Output to 4a. The first array switch 24a is
The switching signals of the switches coming from the plurality of latches 20a to 20n set a launch period for launching the transmission pulse, and select 2n signals so as to have a delay difference according to the focus data. The next launch period setting circuit 25 is composed of, for example, an AND circuit and an inverter, and produces an H (high) signal during the launch period and an L (low) signal during the other periods.

The second selection circuit 22b selects a signal whose transmission pulse width matches the desired pulse width from the output of the frequency dividing circuit 21, and the second shift register 23b.
Send to. The second shift register 23b and the second array switch 24b connected thereto operate similarly to the first shift register 23a and the first array switch 24a to set the pulse width of the transmission pulse. And n signals are selected so as to have a delay difference according to the focus data.

Next, the output signals from the second array switch 24b and the launch period setting circuit 25 are, for example, A
It is input to the wave number setting circuit 26 composed of an ND circuit, processed by this wave number setting circuit 26, and sent out to the wave transmission driver 2 shown in FIG. 1 as a desired wave transmission control signal. The timing diagram of these operations is shown in FIG.
In this example, the pulse wave number of the transmission control signal output from the wave number setting circuit 26 is "3" (see FIG. 3 (h)).

In this state, since the delay difference information of each channel is sent to the focus control circuit 18 shown in FIG. 2, for example, the delay start information of each center channel of the probe 1 is used as a reference. The launch time of the channel can be calculated. Thus, which switch in the first array switch 24a should be selected is represented by the clock cycle from the controller 15 shown in FIG. 1 as the delay difference unit. Of the shift register 23a and the pin of the first array switch 24a. Therefore, indexing the selected data as the choice of switches in the first array switch 24a, odd channel ch ₁ of a plurality of latches 20 a to 20 n, ch _3, ch _5, sends ... to. Then
Since the wave number control circuit 19 stores the width and wave number data of the transmitted pulse, it is possible to calculate how long the wave should be transmitted from the transmission start time, and based on the result, the second array Selection data indicating which switch of the switches 24b is selected can be calculated. Then, the data is transferred to the even channels ch ₂ of the plurality of latches 20a to 20n,
Send to ch ₄ , ch ₆ , ... In this way, by changing the switching signals of the switches from the plurality of latches 20a to 20n, the wave number of the transmission pulse can be made variable as shown in FIG. In this example, the pulse wave number of the wave transmission control signal output from the wave number setting circuit 26 is "6" (see FIG. 4 (h)).

By weighting, the azimuth resolution is improved by reducing the deviation of the wavelength λ by decreasing the deviation of the directivity function by the wavelength λ. Then, if the wave number of the ultrasonic pulse for transmission is changed by control, the signal band changes, and when the pulse wave number is small, the band is wide, and when the pulse wave number is large, the band is narrow. Further, in the narrow band, the deviation of the wavelength λ is smaller than that in the wide band. For this reason,
The lateral resolution is improved by controlling the wave number of the transmission pulse.
On the other hand, the distance resolution is determined by the wave number and wavelength of the ultrasonic pulse. As the number of waves increases, the range resolution decreases.
Since the distance resolution is superior to the azimuth resolution and the distance resolution, these two resolutions can be made substantially equal by adjusting the wave number. Then, if the azimuth resolution and the distance resolution are substantially equal, the apparent distortion of the obtained ultrasonic image in the azimuth direction and the distance direction can be eliminated.

In the above description, the wave number of the transmitted pulse is controlled. However, the present invention is not limited to this, and the pulse duty, pulse width, pulse amplitude, etc. are used alone or in combination, and the signal band is narrowed. It may be banded. Further, although the weighting of the transmitted wave is described in the above description, the case of receiving the wave or a combination of weighting of both the transmitted wave and the received wave may be used.

FIG. 5 is a block diagram of an essential part showing a second embodiment of the present invention. This embodiment narrows the signal band of the transmitted signal by varying the wave number of the transmitted pulse in the embodiment shown in FIG. 1, whereas the embodiment of FIG. The signal band of the wave signal is narrowed. The band pass filter 27 inputs the received signal amplified by the preamplifier 5 and limits the pass band of the signal. The band pass filter 27 is provided by the number of channels of the transducer elements of the probe 1 and its output signal. Are sent to the focus circuit 6 of each channel.
The internal circuit configuration for one channel (see reference numeral 27a) of the bandpass filter 27 includes an operational amplifier 28, a resistor 29, and a capacitor 30, as shown in FIG. 6, for example. Here, the constants of the resistor 29 and the capacitor 30 may be set so that the same band as the signal band when the wave number is determined in the embodiment shown in FIG. 1 passes. Further, the other resistances r ₁ , r ₂ , ..., Ri have different resistance values, but these resistances r _{1 to} r i
Is switched by the selector 31, the pass band width can be changed while the center frequency is constant.

A pass band controller 32 is connected to the band pass filter 27 as shown in FIG. The pass band controller 32 controls the pass band of the band pass filter 27, and although not shown in the figure, a storage means for storing pass band data obtained by calculation or experiment, and a band pass filter. Storage means for storing a table showing the relationship between the pass band data of the pass band of the filter determined by the circuit constant of the filter 27 and the selection data of the selector 31 shown in FIG. 6, and the passages read out from these two storage means respectively. It has a built-in comparison circuit for comparing whether or not the band data match, and sends a selection signal to the selector 31 only when the band is a desired band.

Next, the operation of the second embodiment thus constructed will be described. In FIG. 5, first, the output of the limiter 4 is sent to the preamplifier 5, and the preamplifier 5 weights it in the same manner as in the embodiment of FIG. Next, the output of the preamplifier 5 is input to the bandpass filter 27,
The band is limited by the band pass filter 27. Then, the output is input to the focus circuit 6, focused by the focus circuit 6, and output to the next deflection circuit 7. The band pass filter 27 is shown as being placed after the preamplifier 5, but the present invention is not limited to this, and it is provided after the focus circuit 6 and the signal after addition of several channels is input in the focus circuit 6. You may do it. Further, when the focus circuit 6 and the deflection circuit 7 are digitized, it suffices to perform a calculation corresponding to the above filter processing.

Furthermore, as a third embodiment of the present invention, the means for adjusting the signal band of the transmitted signal or the received signal is:
There may be a plurality of devices having different adjustment conditions, and a means for switching the adjustment condition of the signal band depending on the type of the probe 1 used may be provided. For example, in the second embodiment shown in FIG. 5, a plurality of band pass filters 27 as means for adjusting the signal band of the received signal are provided with different adjustment conditions, and as shown in FIG. A switch 33 is provided commonly to the pass filters 27, and each band pass filter 27 is switched according to the type of the plurality of probes 1 used. In addition to the above example,
In the embodiment shown in FIG. 1, a plurality of transmission weight control circuits 16 are provided as means for adjusting the signal band of the transmission signal,
These may be switched by a switch 33 similar to that shown in FIG. 6 according to the type of the plurality of probes 1.

Although not shown, means (16, 27) for adjusting the signal band of the ultrasonic transmission signal or the ultrasonic reception signal by an input device such as a rotary switch connected to the controller 15 shown in FIG. ), In order to make the azimuth resolution and the distance resolution of the obtained ultrasonic image substantially equal, the operator may arbitrarily adjust the azimuth resolution and the distance resolution by operating the input device. .

[0033]

Since the present invention is constructed as described above,
By providing means for adjusting the signal band of the ultrasonic transmission signal or the reception signal, the azimuth resolution and the distance resolution of the obtained ultrasonic image can be made substantially equal, and the resulting ultrasonic image can be obtained. The distortion of can be eliminated. Therefore, it is possible to improve the azimuth resolution without considering the balance between the azimuth resolution and the distance resolution as in the conventional art. The situation of the part can be correctly recognized.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an internal configuration of a transmission weight control circuit in the above embodiment.

FIG. 3 is a timing diagram for explaining the operation of the transmission weight control circuit.

FIG. 4 is a timing diagram for explaining the operation of the transmission weight control circuit.

FIG. 5 is a block diagram of an essential part showing a second embodiment of the present invention.

FIG. 6 is a block diagram showing an internal circuit configuration for one channel of the bandpass filter in the second embodiment.

FIG. 7 is a block diagram showing a conventional ultrasonic diagnostic apparatus of this type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Probe 2 ... Transmission driver 4 ... Limiter 5 ... Preamplifier 6 ... Focus circuit 7 ... Deflection circuit 8 ... Post-processing circuit 9 ... ADC 10 ... Buffer memory 11 ... Image memory 12 ... Image display circuit 13 ... Display 15 ... controller 16 ... transmission weight control circuit 27 ... band pass filter 32 ... pass band controller 33 ... switcher

Claims (5)

[Claims] 1. A wave transmitting means for transmitting an ultrasonic pulse or an ultrasonic continuous wave into a subject, a wave receiving means for receiving and amplifying a reflected wave from a diagnostic site in the subject, and the receiving means. A focus circuit for inputting the received signal amplified by the wave means to focus the beam, a post-processing circuit for performing signal compression and envelope detection on the received signal from the focus circuit, and an output signal from the post-processing circuit , Image processing means for A / D converting and processing for image display, display means for inputting an image signal from the image processing means and displaying it as an image, and transmitting for each channel or in units of a plurality of channels. In an ultrasonic diagnostic apparatus comprising either one or both of a transmission weighting means for changing the amplitude of a wave pulse or a reception weighting means for changing the amplitude of a reception signal, an ultrasonic transmission signal or reception signal Signal of An ultrasonic diagnostic apparatus, characterized in that means for adjusting a band is provided so that the obtained ultrasonic image has substantially the same azimuth resolution and distance resolution. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the signal band adjusting means narrows the signal band of the transmitted signal or the received signal. 3. The signal band adjusting means is provided with means for varying the wave number of the transmitted ultrasonic pulse, and is adapted to narrow the signal band of the transmitted signal.
The ultrasonic diagnostic apparatus described. 4. The ultrasonic diagnostic apparatus according to claim 2, wherein said signal band adjusting means is provided with a band pass filter for the received signal to narrow the signal band of the received signal. . 5. The means for adjusting the signal band of the transmitted signal or the received signal has a plurality of different adjustment conditions, and the adjustment condition of the signal band depends on the type of the probe used. 5. The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic diagnostic apparatus is provided with a means for switching.