JPH04193165A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To obtain a device without reduction of the detection precision of a low-level echo signal and no cost increase of parts by making two kinds of the high and low reference voltages of an A/D converter variable, making the difference between the reference voltage variable, and making the gain and dynamic range of a receiving circuit variable. CONSTITUTION:The low level reference voltage VL and the high level reference voltage VH are inputted to reference voltage terminals of an A/D converter 6 from reference voltage generators 71, 72 respectively. When analog signals S are inputted to the A/D converter 6, the signal within the voltage range (c) set by two kinds of the high and low reference voltages VL, VH in advance is converted into a digital code. When the reference voltages VL, VH and the voltage range (c) are correlated with the gain and dynamic range of a receiving circuit, the change of difference between the reference voltages VL, VH corresponds to the change of the dynamic range, thus indicating that the shift of the reference voltages VL, VH in DC while this difference is kept constant corresponds to the change of the gain.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ultrasonic diagnostic apparatus with variable gain and dynamic range.

(Prior Art) As is well known, in an ultrasonic diagnostic apparatus, a transmitting circuit is operated to emit ultrasonic waves from a probe to a subject, and echo signals from the subject are amplified and logarithmically compressed in a receiving circuit. After detection, convert it into a digital signal with an A/D converter,
This is stored in image memory. Then, the data in the image memory is read out via a D/A converter and displayed on the monitor television in synchronization with the synchronization signal of the monitor television, thereby obtaining an ultrasonic tomographic image of the subject, etc.

In such ultrasonic diagnostic equipment, the gain of the receiving circuit can be obtained by multiplying the echo signal and the gain control signal, and since a logarithmic amplifier is usually used as a high-frequency amplifier in the receiving circuit, the gain of the receiving circuit can be obtained by multiplying the echo signal and the gain control signal. Multiplication with the gain control signal can be treated as logarithmic addition.

Figure 3 shows the configuration of the main parts in the receiving circuit of a conventional ultrasound diagnostic device. In the figure, ■ is a logarithmic amplifier that amplifies and logarithmically compresses the echo signal; A detection circuit consisting of a diode that detects an envelope, and 3 indicates an attenuator. Also, S,, S,
are the output signals of logarithmic amplifier 1 whose phases are inverted, S,
is a gain control signal, and S4 is an output signal of the detection circuit 2.

Here, the output voltage value of the logarithmic amplifier l is V, the value of the echo signal is 6, and the value of the gain control signal S is V. , when the constant is A, V'=A-1og(V v, 'V J=A ・
(log(Vl:)+log(Vc)) −(])
The gain can be expressed as follows, and the gain was changed by changing the value (6) of the gain control signal. In this case, conventionally, the detection circuit 2 functions as a so-called slicer having a gain control signal S having a certain threshold level, thereby performing the gain control function.

On the other hand, changing the dynamic range in this type of ultrasonic diagnostic equipment corresponds to changing the constant A in equation (1) above, so conventionally, as shown in FIG. The dynamic range was adjusted by changing the amplitude of the output signal by connecting an attenuator 3 (or an amplifier) or the like.

Incidentally, FIG. 4 shows the signals S of each part in FIG.

An example of the waveform of ~S4 is shown.

(Problems to be Solved by the Invention) In the conventional gain variable means described above, the output signal S is distorted near the threshold level due to the nonlinearity of the detection diode, and the low-level echo signal is not accurate. There was a problem that it could not be detected. In addition, in the conventional dynamic range variable means, attenuator 3
Since the frequency-related transmission characteristics of the (or amplifier) etc. must be kept constant at any gain, there is a drawback that highly accurate components are required, leading to an increase in component costs.

The present invention has been made to solve the above problems,
The purpose is to provide an ultrasonic diagnostic apparatus in which the gain and dynamic range can be varied without reducing the detection accuracy of low-level echo signals or increasing component costs.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a logarithmic amplifier that amplifies and logarithmically compresses an echo signal from a subject to which ultrasound is emitted, and an output signal of the logarithmic amplifier. an ultrasonic diagnostic apparatus comprising a receiving circuit having a detection circuit for detecting a waveform, and an A/D converter for converting an analog output signal of the detection circuit into a digital signal; Each of the reference voltages is made variable, and the difference between the reference voltages is made variable to make the gain and dynamic range of the receiving circuit variable.

(Function) The present invention focuses on the function of an A/D converter and its reference voltage. That is, the analog signal input to the A/D converter has two types of reference voltages, high and low, V, , V
, converts signals within a preset voltage range into digital output codes. Therefore, VL and v8
The dynamic range of the output signal changes by changing the difference between VL and VH.
and V.

Shifting in direct current corresponds to changing the gain of the input/output signal.

That is, by providing means for making the reference voltages of the A/D converter variable, the gain and dynamic range of the receiving circuit can be made variable.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the configuration of the main parts of the ultrasonic diagnostic apparatus according to this embodiment. In the figure, 4 is a transmitting circuit that generates pulses to excite the ultrasonic probe 5, and 5 is a transmitting circuit that transmits and receives ultrasonic waves. The echo signal from the subject detected by the probe 5 is amplified and logarithmically compressed by the logarithmic amplifier 1 as in FIG. 3, and then detected by the detection circuit 2. Here, the logarithmic amplifier 1 and the detection circuit 2 constitute a receiving circuit 100.

The signal output from the detection circuit 2 is sent to the subsequent A/D converter 6.
is input to the analog signal input terminal of the A/D.
The converter 6 receives a low level reference voltage VL and a high level reference voltage ■ from reference voltage generators 71 and 72, respectively. is input to each reference voltage terminal. Here, the functions of the A/D converter 6 and its reference voltage will be explained based on FIG. 2. When an analog signal S as shown in FIG. 2(a) is input to the A/D converter 6, the A/D converter 6 converts a voltage preset by two types of high and low reference voltages V, , V11. For signals within range C, convert them to digital codes.

Therefore, these reference voltages "' L + "
'? Comparing the voltage range C and the gain and dynamic range of the receiving circuit, the reference voltage V
, , V corresponds to a change in the dynamic range, and while keeping this difference constant, the reference voltages VL and V
It can be seen that shifting H in a direct current manner corresponds to a change in gain. In other words, the reference voltage generator 71
．． 72 to change the reference voltages VL, VH, and the difference between them, the value of the digital code for the same analog input signal changes, so the gain and dynamic range of the receiving circuit 2 are made variable. I can do it.

The digital data output from the A/D converter 6 that operates in this manner is stored in the image memory 8, and the image data read out from the image memory 8 is converted into an analog signal by the D/A converter 9. monitor tv
The image will be displayed on O.

According to this embodiment, even if the level of the echo signal after detection is low, the echo signal It is possible to increase the gain without degrading the In addition, the dynamic range can be changed simply by using the reference voltages vL, Vl.
It is sufficient to simply change the difference in l, and the transmission characteristics relative to the frequency of the echo signal can be compensated without using a high-precision attenuator or the like.

(Effects of the Invention) As described above, according to the present invention, it is possible to change the gain and dynamic range of the receiving circuit simply by providing a means for varying the reference voltage of the A/D converter. There is an effect that there is no fear of deterioration and that it is possible to realize a low-cost ultrasonic diagnostic device.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, and FIG.
Figures (a) and (b) are explanatory diagrams of the operation of the A/D converter, and Figure 3 is a schematic configuration diagram of a receiving circuit in the conventional technology.
FIG. 4 is a signal waveform diagram of each part in FIG. 3. 1.Logarithmic amplifier 2..Detection circuit 4..Transmission circuit 5..Probe 6..A/D converter

Claims (1)

[Scope of Claims] A receiving circuit including a logarithmic amplifier that amplifies and logarithmically compresses an echo signal from a subject to which ultrasonic waves are emitted, and a detection circuit that detects an output signal of the logarithmic amplifier; A/A that converts analog output signals into digital signals
In the ultrasonic diagnostic apparatus equipped with a D converter, two types of high and low reference voltages of the A/D converter are made variable, and the difference between each reference voltage is made variable to make the gain and dynamic range of the receiving circuit variable. An ultrasonic diagnostic device characterized by: