KR20070022291A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

Disclosed is a technique for providing a compact and inexpensive ultrasonic diagnostic apparatus having a high dynamic range with high sensitivity without requiring a high resolution A / D converter. According to the technique, an ultrasonic vibrator 1 for transmitting and receiving ultrasonic waves is provided. While driving with the generated driving circuit 2, the echo signal received by the ultrasonic vibrator is input to the analog low pass attenuator 3 to attenuate the low pass component, and the output signal of the analog low pass attenuator is converted into the A / D converter 4. Converts the digital signal into a digital signal, inputs the converted and output digital signal to the digital correction filter 5, augments the low frequency component attenuated by the analog low pass attenuator, and distributes a frequency that is almost equal to the echo signal received by the ultrasonic vibrator. Configure to output a digital signal having a.

Description

Ultrasonic diagnostic device {ULTRASONIC DIAGNOSTIC APPARATUS}

The present invention relates to an ultrasonic diagnostic apparatus for transmitting ultrasonic pulses toward a living body, synthesizing a received signal of reflected waves from the living body, and obtaining an ultrasonic tomographic image.

BACKGROUND ART Conventionally, as an ultrasonic diagnostic apparatus, a driving pulse is applied to an ultrasonic vibrator from a driving circuit to transmit ultrasonic waves from an ultrasonic vibrator to a target portion, and an echo signal from the target portion is received by the ultrasonic vibrator to amplify, It is disclosed to perform image processing such as addition and logarithmic compression to obtain image data, to send the image data to a monitor, and to display a desired diagnostic image on the monitor (examples). See, for example, Patent Document 1 below.

Further, in processing an echo signal, an ultrasonic signal processing apparatus for converting an analog received signal received by an ultrasonic vibrator into a digital signal and multiplying the digital signal by a reference signal of a predetermined frequency to convert a signal waveform ( For example, Patent Document 2) described below, or an ultrasonic diagnostic apparatus (see, for example, Patent Document 3 below) that obtains an ultrasound tomographic image by synthesizing digital data obtained by converting an analog received signal into a digital signal. It is.

Fig. 6 is a block diagram showing a schematic configuration of an ultrasonic transmitting and receiving unit and a signal converting unit in the ultrasonic signal processing apparatus and ultrasonic diagnostic apparatus for converting an analog received signal into a digital signal. The transmitting and receiving unit and the signal converting unit transmit ultrasonic waves and receive an echo signal, an ultrasonic vibrator 1, a drive circuit 2 for transmitting driving pulses to the ultrasonic vibrator 1 according to a trigger signal, and an ultrasonic vibrator 1 And an A / D converter 4 for converting the echo signal obtained by the < RTI ID = 0.0 >

In this case, the echo signal obtained by the ultrasonic vibrator 1 has a large amplitude in the shallow part and weak in the deep part, so that the resolution (number of bits) of the A / D converter 4 is reduced. You may run out of bits. Therefore, in the actual ultrasonic diagnostic apparatus, a preamplifier (not shown) and a variable gain amplifier (VCA) are connected between the ultrasonic vibrator 1 and the A / D converter 4. By controlling the amplitude of the echo signal, the dynamic range is suppressed and input to the A / D converter 4.

(Patent Document 1)

Japanese Patent Laid-Open No. 6-154210 (paragraph 0011, Fig. 1)

(Patent Document 2)

Japanese Patent Laid-Open No. 6-313764 (paragraph 0008, Fig. 1)

(Patent Document 3)

Japanese Patent Laid-Open No. 7-171152 (paragraph 0023, Fig. 1)

However, in the above-described ultrasonic signal processing apparatus or ultrasonic diagnostic apparatus, immediately after the driving circuit 2 transmits a large amplitude pulse to drive the ultrasonic vibrator 1, the ultrasonic vibrator 1 constitutes the ultrasonic vibrator 1. Under the influence of piezoelectric elements and cables, ringing with low frequency components occurs. For this reason, as shown in FIG. 7, since the ringing of a large amplitude pulse superimposes on the natural echo signal acquired immediately after driving by a transmission pulse, it is shown by the arrow without missing a natural echo signal. In order to input to the A / D converter 4 in the range of the input upper and lower limits shown, it is necessary to use the A / D converter 4 having a large number of bits in order to lower the gain at the top. However, since the resolution of the A / D converter realized at low cost in reality is about 12 bits, only a dynamic range of about 60 dB can be handled, and the variable gain amplifier has a gain variable width of about 40 to 60 dB, for example. For example, the 120dB ringing lacks the number of bits to handle overlapping echo signals. The above-mentioned ultrasonic signal processing apparatus and ultrasonic diagnostic apparatus improve this problem, but there is a problem that the configuration becomes complicated and becomes large and expensive.

The present invention has been made to solve the problems of the conventional apparatus, and an object thereof is to provide a compact and inexpensive ultrasonic diagnostic apparatus having a high dynamic range with high sensitivity without requiring a high resolution A / D converter.

In order to achieve the above object, the invention according to claim 1 drives an ultrasonic vibrator for transmitting and receiving ultrasonic waves with a driving circuit for generating a pulse signal, and simultaneously transmits an echo signal received by the ultrasonic vibrator to an analog low pass. Input the attenuator to attenuate the low-pass components, input the output signal of this analog low-pass attenuator to the A / D converter, convert it to a digital signal, and input the converted and output digital signal to the digital correction filter, The low-pass component attenuated by the low-pass attenuator is augmented to output a digital signal having a frequency distribution almost equal to the echo signal received by the ultrasonic vibrator.

This configuration makes it possible to provide a compact and inexpensive ultrasonic diagnostic apparatus having a high dynamic range with high sensitivity without requiring a high resolution A / D converter.

According to the second aspect of the present invention, the analog low pass attenuator amplifies the echo signal received by the ultrasonic vibrator in the preamplifier and then attenuates the low pass component by the low pass attenuation filter, and corrects the attenuation of the echo signal by the variable gain amplifier. Configure to

With this configuration, in the A / D conversion of the echo signal, the low-pass ringing component can be removed to reduce the dynamic range of the signal and input the A / D converter.

According to the present invention, it is possible to provide a compact and inexpensive ultrasonic diagnostic apparatus having a high dynamic range with high sensitivity without requiring a high resolution A / D converter.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing a schematic configuration of an ultrasonic transmitting and receiving unit and a signal converting unit in an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

2 is a block diagram showing a detailed configuration of an analog low pass attenuator constituting an embodiment of the present invention.

3 is a diagram showing an echo signal waveform applied to an A / D converter in order to explain the operation of the embodiment of the present invention.

4A is a diagram for explaining the operation of the embodiment of the present invention, showing the frequency characteristics of the low pass attenuation filter.

4B is a view for explaining the operation of the embodiment of the present invention, showing the frequency characteristics of the digital correction filter.

5A is a diagram showing an example of a frequency distribution of an echo signal received by an ultrasonic vibrator as an input of a low pass attenuator in order to explain the operation of the embodiment of the present invention.

5B is a diagram showing an example of a frequency distribution of an echo signal passing through an analog low pass attenuator as an output of a low pass attenuator for explaining the operation of the embodiment of the present invention.

5C is a diagram showing an example of a frequency distribution of an echo signal in which a low pass component is enhanced in a digital correction filter as an output of the digital correction filter, in order to explain the operation of the embodiment of the present invention.

5D is a diagram showing a signal waveform of an echo signal obtained by receiving from an ultrasonic vibrator for explaining the operation of the embodiment of the present invention.

5E is a diagram showing a signal waveform of an echo signal passed through an analog low pass attenuator in order to explain the operation of the embodiment of the present invention.

Fig. 5F is a view showing a signal waveform of an echo signal with a low pass component enhanced in a digital correction filter for explaining the operation of the embodiment of the present invention.

Fig. 6 is a block diagram showing a schematic configuration of a transmitting / receiving unit and a signal converting unit of an ultrasonic wave in a conventional ultrasonic signal processing apparatus or ultrasonic diagnostic apparatus.

Fig. 7 is a view showing an echo signal waveform applied to an A / D converter in order to explain the operation of a conventional ultrasonic signal processing apparatus or ultrasonic diagnostic apparatus.

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated in detail based on preferable embodiment shown in drawing.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows schematic structure of the ultrasonic transmission-reception part and signal conversion part in embodiment of the ultrasonic diagnostic apparatus which concerns on this invention. The transmitting and receiving unit and the signal converting unit include an ultrasonic vibrator 1 for transmitting an ultrasonic wave and receiving an echo signal, a driving circuit 2 for transmitting a driving pulse to the ultrasonic vibrator 1 in accordance with a trigger signal, and an ultrasonic vibrator ( The echo signal received in 1) is input, and the analog low pass attenuator 3 which attenuates and outputs the low pass component, and the echo signal passing through this analog low pass attenuator 3 are input, and A / D converted and outputted. The frequency characteristic opposite to the / D converter 4 and the analog low pass attenuator 3, i.e., the low pass component, is augmented and restored to a nearly flat frequency spectrum distribution characteristic from the low pass to the high pass of the echo signal. The digital correction filter 5 is provided.

FIG. 2 is a block diagram showing the detailed configuration of the analog low pass attenuator 3, the preamplifier 31 for amplifying the echo signal received by the ultrasonic vibrator 1, and the echo signal amplified by the preamplifier 31. FIG. Inputs a low pass attenuation filter 32 that attenuates and outputs a low pass component, and an echo signal output from the low pass attenuation filter 32, corrects and outputs the attenuation of the echo signal according to the propagation time. A variable gain amplifier 33 is provided.

The operation of the embodiment of the present invention configured as described above will be described below with reference to FIGS. 3 to 5.

When the ultrasonic vibrator 1 is driven by a large amplitude pulse by the drive circuit 2, a signal in which ringing is superimposed on an echo signal is applied to the analog low pass attenuator 3 as shown in FIG. Since the analog low pass attenuator 3 includes the low pass attenuation filter 32, ringing having a low frequency component shown in FIG. 7 is eliminated, and as shown in FIG. 3, within the upper and lower limits of the A / D conversion input. The suppressed echo signal is input to the A / D converter 4. Then, the A / D converter 4 converts the digital signal to the digital correction filter 5. The digital correction filter 5 augments and outputs the low pass attenuated by the low pass attenuation filter 32. As a result, a digital echo signal waveform having the same frequency distribution as the signal waveform input to the analog low pass attenuator 3 is obtained.

In this case, in the analog low pass attenuator 3, the echo signal received by the ultrasonic vibrator 1 is amplified by the preamplifier 31, and then the low pass component is attenuated by the low pass attenuation filter 32, and the variable gain amplifier ( 33) corrects the attenuation of the echo signal in accordance with the propagation time.

4A is a line showing the frequency characteristic of the low pass attenuation filter 32, that is, the relationship between the frequency and the gain. As shown by the curve P, it has a low gain that is almost constant in the low range and is in the intermediate frequency band. The gain increases at a predetermined change rate, and has a high gain which is almost constant in the high range. 4B is a diagram showing the frequency characteristics of the digital correction filter 5, that is, the relationship between the frequency and the gain. As shown by the curve Q, it has a high gain which is almost constant in the low range and a predetermined rate of change in the intermediate frequency band. The low gain decreases and is set to have a substantially constant low gain in the high range, and the digital correction filter 5 is an inverse filter with respect to the low pass attenuation filter 32.

FIG. 5A illustrates the frequency distribution of the echo signal received by the ultrasonic vibrator 1 and is assumed to be distributed like a curve R. FIG. When this echo signal passes through the analog low pass attenuator 3, as shown in Fig. 5B, the low pass component decreases and changes to a distribution such as curve S. FIG. Thereafter, by augmenting the low pass component in the digital correction filter 5, as shown in FIG. 5C, the low pass component is compensated and restored to the original frequency distribution as shown by the curve T. FIG. Thus, the signal waveform shown in FIG. 5D is deformed by the analog low pass attenuator 3 as shown in FIG. 5E, but when outputted from the digital correction filter 5, it is restored to the original signal waveform as shown in FIG. 5F. .

In the actual ultrasonic diagnostic apparatus, as described above, the preamplifier and the variable gain amplifier are provided between the ultrasonic vibrator 1 and the A / D converter 4, but in the present embodiment, the analog low pass attenuator 3 ), The preamplifier 31, the low pass attenuation filter 32, and the variable gain amplifier 33 are sequentially connected, whereby a good S / N ratio can be ensured. In addition, since the dynamic range of the signal after attenuating the low pass component is suppressed low, the advantage that the gain variable width of the variable gain amplifier 33 is also smaller than that of the signal without attenuating the low pass component can be obtained.

Thus, according to this embodiment, the low-pass ringing component is removed by passing the signal in which the echo signal and the large amplitude pulse are superimposed through the analog low pass attenuator 3 to subtract the dynamic range of the signal, thereby reducing the A / D converter 4. ) Can be entered.

In addition, by configuring the digital correction filter 5 to enhance the low-pass component of the echo signal of the digital data after passing through the A / D converter 4, the influence of the analog low-pass attenuator 3 is canceled out. Since it can be restored to a waveform and can be accepted by the A / D converter 4 without saturating the natural echo signal information, the natural image information is obtained using an A / D converter with a low resolution and a variable gain amplifier. It is possible to provide a compact and inexpensive ultrasonic diagnostic device with excellent output.

Since this invention is comprised as mentioned above, the ultrasonic diagnostic apparatus of this invention is useful in the technical field which acquires the ultrasonic tomographic image of a subject.

Claims (2)

An ultrasonic vibrator for transmitting and receiving ultrasonic waves, a driving circuit for generating a pulse signal to drive the ultrasonic vibrator, and an analog low pass attenuator for attenuating and outputting low frequency components of an echo signal received by the ultrasonic vibrator And an A / D converter for A / D converting and outputting the output signal of the analog low pass attenuator, and the low frequency component attenuated in the analog low pass attenuator of the digital signal converted and output from the A / D converter to enhance the echo. An ultrasonic diagnostic apparatus having a digital correction filter for outputting a digital signal having a frequency distribution almost equal to the signal. The analog low pass attenuator comprises: a preamplifier for amplifying the echo signal received by the ultrasonic vibrator; and an echo signal amplified by the preamplifier and attenuating a low pass component. And a variable gain amplifier for inputting a low pass attenuation filter and an echo signal output from the low pass attenuation filter, correcting and outputting the attenuation of the echo signal in accordance with a propagation time.

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