JPS62211049A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] A logarithmic amplifier for amplifying received waves in an ultrasonic diagnostic device is equipped with a bandpass filter at an input terminal with the highest amplification factor among its plurality of input terminals, It is configured to switch the pass characteristics according to the probe frequency, which can suppress the noise level and prevent the dynamic range from narrowing.

[Industrial Application Field] The present invention relates to an ultrasonic diagnostic apparatus that creates a diagnostic image of the inside of a subject based on reflected waves from inside the subject when ultrasound is emitted to the subject. It is related to wave signal processing.

[Prior art] In an ultrasonic diagnostic device, the level of the echo signal output by a piezoelectric element upon receiving an ultrasonic wave reflected from a subject has an extremely wide dynamic range, and the difference between the minimum signal and maximum signal is several seconds. It reaches over 10 dB (decibels).

Therefore, if the echo signal is applied to a display through a linear amplifier and displayed, the dynamic range is insufficient and saturation occurs, making it impossible to obtain good image quality.

Therefore, logarithmic amplification circuits have conventionally been used to amplify echo signals.

4 shows the configuration of a conventional logarithmic amplification circuit used in an ultrasonic diagnostic apparatus, and FIG. 5 shows its logarithmic amplification characteristics.

As shown in FIG. 4, the logarithmic amplifier circuit includes a logarithmic amplifier 1 having a plurality of input terminals 2a+2b, 2c+2d with different amplification factors, an attenuator 3a and linear amplifiers 3c, 3d connected to the input terminals. configured.

A plurality of input terminals with different amplification factors of logarithmic amplifier l, 2a
(-30dB), 2b (0dB), 2c (+
By inputting signals with different amplification factors to 30dB) and 2d (+60dB), logarithmically amplifying them according to their levels in logarithmic amplifier 1, and then adding them, the fifth
As shown in the figure, a wide range of logarithmic characteristics is obtained.

If there is a very low level echo signal, this will first occur.
Although it is amplified by the linear amplifiers 3c and 3d, the noise component is also amplified and then logarithmically compressed, so the noise component becomes relatively large and the noise level rises, as shown by the broken line in Figure 5. , the dynamic range was narrowed.

[Problems to be Solved by the Invention] The present invention aims to solve the above-described conventional problems and provide an ultrasonic diagnostic apparatus that can suppress the noise level to a low level.

[Means for Solving the Problems] FIG. 1 shows a block diagram of the principle of an ultrasonic diagnostic apparatus according to the present invention.

In FIG. 1, the same reference numerals as in FIG. 3 indicate the same objects.

4 is a band pass filter, which is inserted into the input circuit to the input terminal 2d of the logarithmic amplifier 1 having the highest amplification factor.

The bandpass filter 4 is configured such that its bandpass characteristics can be switched by external control.

Reference numeral 5 denotes a control circuit which receives a frequency switching signal from the probe and switches the bandpass characteristic of the bandpass filter 4 in response to the frequency switching signal.

In FIG. 1, the bandpass filter 4 is replaced by a linear amplifier 3d.
Although the bandpass filter 4 is inserted between the input terminal 2d of the logarithmic amplifier l and the input terminal 2d having the highest amplification factor, it is of course possible to insert the bandpass filter 4 before the linear amplifier 3d.

[Operation] Ultrasonic diagnostic equipment generally has several types of frequencies, and the frequencies are switched depending on the diagnosis target.

This is because the higher the ultrasound frequency, the better the resolution, but
This is because the attenuation inside the body increases, making it difficult to see deep parts.

In the configuration shown in FIG. 1, when the level of the echo signal input to the input point p is low, this signal is primarily amplified first by the linear amplifiers 3c and 3d, and the noise component is also amplified.

The output of the linear amplifier 3d is input to the bandpass filter 4,
Here, noise outside the signal band is removed and input to the logarithmic amplifier l.

The filtering characteristics of the bandpass filter 4 are switched depending on the frequency of the probe, and only the band necessary for the signal of the ultrasonic frequency being used is passed, so that noise can be removed with high efficiency.

In this way, even echoes with low signal levels are logarithmically amplified with noise components removed, and a high-quality image can be obtained without narrowing the dynamic range due to noise components as in the conventional method.

[Example] The present invention will be explained in more detail below with reference to the example shown in FIGS. 2 and 3.

FIG. 2 is a diagram showing logarithmic amplification characteristics according to an embodiment of the present invention.

As shown in the figure, the noise level does not reduce the upper m-L dynamic range as in the conventional case.

FIG. 3 is a diagram showing filtering characteristics of a bandpass filter in an embodiment of the present invention.

The probe frequency of ultrasound diagnostic equipment is usually 3.5M1l.
z, 5MIIz, 7Ml1z, and 10Ml1z, and the bandpass filter also has bandpass characteristics with the required bandwidth centered around these frequencies.

By switching the filtering characteristics of this bandpass filter in response to switching of the probe frequency, it is possible to remove noise and obtain a high-quality image without limiting the signal band.

[Effects of the Invention] As explained above, according to the present invention, it is possible to remove the noise of the ultrasonic reception signal as much as possible, so it is possible to obtain high-quality images without narrowing the dynamic range and without burying minute signals in noise. The practical effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a principle block diagram of the present invention; FIG. 2 is a diagram showing logarithmic amplification characteristics according to an embodiment of the present invention; FIG. 3 is a diagram showing filtering characteristics of a bandpass filter according to an embodiment of the present invention; FIG. 4 is a circuit configuration block diagram of a conventional logarithmic amplifier circuit, and FIG. 5 is a diagram showing logarithmic amplification characteristics of the conventional logarithmic amplifier circuit. In the drawing, ■ is a logarithmic amplifier, 2a, 2b, 2c, 2d are input terminals, 3a, 3
c, 3d are linear amplifiers, 3b is an attenuator, 4 is a band pass filter, 5 is a control circuit, Block diagram of the principle of the present invention Fig. 1 Fig. 2 Frequency Fig. 3 Fig. 4

Claims (1)

[Scope of claims] In an ultrasonic diagnostic apparatus equipped with a logarithmic amplifier that logarithmically amplifies an ultrasound reflected signal from a subject, an input terminal having the highest amplification factor among a plurality of input terminals having different amplification factors of the logarithmic amplifier. A bandpass filter (4) inserted into the input circuit to the probe, and a control circuit (5) for controlling switching of the bandpass characteristics of the bandpass filter (4), corresponding to switching of the operating frequency of the probe. An ultrasonic diagnostic apparatus characterized in that it is configured to switch the bandpass characteristics of the bandpass filter (4).