JPH0125252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image signal processing device for image processing in an ultrasonic diagnostic device or the like.

As an ultrasound diagnostic device, a probe emits ultrasound toward a subject, the probe receives the ultrasound signal reflected from the subject, and the display displays an ultrasound tomographic image of the subject. Devices for displaying are well known.

Such an ultrasonic diagnostic apparatus is shown in FIG. In the figure, the ultrasonic signal received by probe 1 is
The signal is amplified by a high frequency amplification circuit 2, and in order to improve the amplitude display characteristics, the amplified signal is logarithmically compressed by a logarithmic amplifier 3, and then detected by a detection circuit 4. The detected signal is converted from an analog signal to a digital signal by an analog-to-digital conversion circuit (hereinafter abbreviated as ADC) 5, and is stored in a storage circuit 6. The stored digital signal is converted to an analog signal again through a digital-to-analog conversion circuit (hereinafter abbreviated as DAC) 7, amplified by a video amplifier 8, and then applied to a display 9.

However, not all of the tomographic images obtained in this way are diagnostically useful information. In other words, the signal from a strong reflection site above a certain level is
This makes it difficult to clearly display the detailed information contained therein and the boundaries of reflection sites, making it difficult to obtain information useful for diagnosis. Several processing methods have been known to solve this difficulty.

One of these is a processing method called the FTC (Fast Time Constant) method. In this method, as shown in FIG. 2A, a part of the output of the detection circuit 4 is passed through a differentiating circuit 11 to depict the characteristics of the steep rising part, and after being amplified by an amplifier 12, this is converted back into the original analog signal. By mixing it with the signal and treating it as a composite signal, the ring interval can be clarified. In other words, the output amplitude of the differentiating circuit increases in proportion to the speed of the rise time, and the waveform attenuates with the time constant, so the original video signal (B) in Figure 2 is transformed as shown in Figure 2C. , it can be seen that it works as expected.

As a second conventional example, a method called a delay automatic gain control method (hereinafter abbreviated as DAGC) is also well known. In this method, a part of the output of the detection circuit 4 is integrated by an integrating circuit 13, as shown in FIG.
By applying the output as a negative feedback signal to the high frequency amplifier 2 via the feedback amount regulator 14, the gain of the high frequency amplifier 2 can be automatically controlled.
Similar to the FTC method, it is possible to emphasize the boundaries of reflective areas. In other words, the output signal of the integrator circuit becomes as shown in Figure 3C, and the amount of feedback near the rising edge is small, and the output from the high frequency amplifier (Figure 3D) has the maximum amplitude at the rising edge, and the feedback amount ( (depending on the time constant of the integrating circuit), it can be seen that the intended purpose is achieved.

Another conventional method, as shown in FIG. 4A, is to add a part of the output of the detection circuit 4 to a high-frequency cutoff video signal passed through a high-frequency cutoff inverting amplifier and the original video signal in an analog manner. It is known that by treating the signal obtained by this method as an input signal to a video amplifier, it is possible to emphasize the outline, as in the two methods described above. That is, the operating waveforms and circuit configuration of this method are as shown in FIG.

However, in the above-mentioned processing methods, there are limits to image processing due to their respective time constants. In the FTC method, a negative voltage is generated at the falling edge of the video signal, so a small signal in this portion is erased due to the negative voltage and is not displayed. Also,
In the DAGC method, as shown in Figure 3,
Since the feedback signal returns from the time of the falling edge of the video signal with the time constant of the integrating circuit, more negative feedback than necessary is applied to the adjacent small signals that enter this part, and as in the former case, the small signals are almost erased. There is a drawback that it can be done. Although this method allows adjustment of the time constant and feedback rate, there is a limit to the adjustment of the feedback rate in relation to oscillation. Furthermore, in the third method, because the output signal of the high-frequency cut-off inverting amplifier and the original video signal are added by analog, the output signal of the high-frequency cut-off inverting amplifier is connected to the negative feedback resistor from the falling edge of the video signal. R and bypass capacitor
This method has the disadvantage of causing the same inconvenience as the above two methods for the signal during recovery with a time constant determined by C.

An object of the present invention is to provide an image signal processing device for solving the above-mentioned conventional drawbacks, clarifying fine information and boundaries contained in signals from strong reflection sites, and obtaining information useful for diagnosis. This will be described below along with examples.

In FIG. 5, parts corresponding to those shown in FIG. 1 are given the same reference numerals. The difference is that a nonlinear analog-to-digital conversion circuit 15 is provided between the detection circuit 4 and the storage circuit 6 instead of the ADC 5.

Next, the operation of this embodiment will be explained. The ultrasonic signal received by the probe 1 is amplified by a high frequency amplifier 2 and a logarithmic amplifier 3, and a part of the video signal detected by the detection circuit 4 is passed through a filter that blocks high frequencies.
The obtained high-frequency cutoff video signal is processed using the nonlinear
The ADC 15 performs A/D conversion, and the resulting digital signal is sent to the storage circuit 6, DAC 7, and video amplifier 8.
The signal is sent to the display device 9 through.

By the way, it is known that by manipulating the reference voltage of the ADC 15, an analog signal can be converted into a digital signal with nonlinear conversion characteristics.
That is, as shown in FIG.
~115, an encoder, a latch 10, and a group of resistors. Taking a 4-bit ADC as an example, the transfer function H of the ADC is: H=16V _IN −V _RB /V _RT −V _RB …(1) Here, V _IN is the input analog signal, V _RT is the reference upper voltage, and V _RB is the reference lower voltage.

Here, the setting is normally made so that V _RT −V _RB =V _IN . Therefore, for example, if V _IN is positive with respect to O _V or
If it swings in the negative direction, V _RB =O can be set.

V _RT =aV _IN +V _BIAS (Here, a is a coefficient and V _BIAS is a bias voltage.) Then, equation (1) becomes H = 16V _IN /aV _IN +V _BIAS (2). This can be expressed as shown in Figure 7.

FIG. 8 is a block diagram of an image signal processing device for an ultrasonic diagnostic apparatus according to an embodiment of the present invention. Reference numeral 16 indicates a high-frequency cutoff filter, 17 indicates an operational amplifier, and 1
8 is an ADC, 19 and 21 are resistors, and 20 is a terminal to which the above-mentioned bias voltage V _BIAS is applied.

FIG. 9 shows a detailed configuration of the high-frequency cutoff filter 16 shown in FIG. 8, where Ca is a coupling capacitor, R ₁ ,
_C1 constitutes an RC filter. Further, the operational amplifier 17 forms the denominator of equation (2) by adding the output signal of the high-frequency cutoff filter 16 and the reference voltage 20 in analog form. The resistance value Ra of the resistor 19 corresponds to the coefficient a in the denominator of equation (2), and the degree of nonlinear conversion is adjusted by changing the voltage division ratio with the resistor 21. Note that the high cutoff frequency _C of the high cutoff filter can be expressed as _C = 1/2πR ₁ C ₁ .

The waveforms of each part of d ₁ to _{d 4} are the waveforms shown in FIG. 10 A to E. That is, the video signal is capacitively coupled to the RC filter by the capacitor Ca to remove the DC component, and the RC filter attenuates the high frequency component, and the video signal is output in the waveform shown in FIG. 10B. This signal is a constant bias voltage
Analog addition with V _BIAS 20 and as a reference voltage,
The waveform shown in FIG. 2 is sent to the ADC 18.
Using this signal as a reference voltage, the analog signal (digital) subjected to analog-to-digital conversion passes through the memory circuit 6 and DAC 7 and gives the waveform shown by _d4 as an analog signal again. The resulting waveform emphasizes the rising edge of the video signal, making it possible to clarify detailed information hidden in strong reflected signals. Note that in the above explanation, the operational amplifier 17
does not necessarily need to be used, and the reference voltage may be obtained by simply connecting the V _BIAS 20 and d ₂ signals. Further, a band pass filter may be used instead of the high cutoff filter 16.

This embodiment eliminates the drawbacks of conventional image processing methods and makes it possible to clarify the outline of a reflective site without losing ultrasound signals. Furthermore, it is possible to clarify information hidden in reflected signals from strong reflecting areas. Furthermore, not only is the circuit configuration for achieving the above-mentioned performance extremely simple, but it is also a major feature that high precision of the parts is not required.

As is clear from the above embodiments, the present invention detects an ultrasonic signal received by an ultrasonic probe with a detection circuit, and converts the signal of the detection circuit into a filter circuit, an attenuation circuit,
The ultrasonic signal is output to the A/D conversion circuit via the bias circuit, processed by the waveform, and converted into an analog signal again by the D/A conversion circuit and displayed on the display, so the ultrasonic signal is not lost. This has the effect that the outline of the reflective area can be made clear (outline enhancement), and the information hidden in the reflected signal from the strong reflective area can be made clear (contrast thinning).

[Brief explanation of drawings]

Figure 1 is a block diagram of the receiving circuit of a conventional ultrasonic diagnostic device, Figure 2 is a block diagram of the main parts of the conventional FTC processing method and waveform diagrams of each part, and Figure 3 is another conventional DAGC processing method. Fig. 4 is a block diagram of main parts of another conventional processing method and its operation waveform diagram, and Fig. 5 is a block diagram of an ultrasonic diagnostic apparatus using the present invention. , FIG. 6 is a circuit diagram of a conventional ADC, FIG. 7 is a conversion characteristic diagram thereof, FIG. 8 is a block diagram of an image signal processing device according to an embodiment of the present invention, and FIG. 9 is a diagram of a high-frequency cutoff filter. The circuit diagram and FIG. 10 are waveform diagrams of each part. 16... High frequency cutoff filter, 17... Arithmetic amplifier, 18... Analog-digital conversion circuit.

Claims (1)

[Claims] 1 A detection circuit that receives the reflected wave of the ultrasound signal emitted to the body tissue with an ultrasound probe and outputs a video signal, and a reference upper voltage divided by multiple series resistors is sequentially input to one input terminal. and a plurality of comparators that input the output signals of the detection circuit in common to the other input terminal and compare them, and an encoder latch circuit that inputs the output signals of these comparators and outputs a digital data signal.
a reference upper voltage generating means for cutting off and attenuating the high frequency component of the output signal of the detection circuit, adding a bias voltage and outputting it to the comparator as the reference upper voltage; and storing the output signal of the encoder latch circuit. An image signal processing device comprising a memory circuit and display means for converting the output signal of the memory circuit back into an analog signal and displaying a tomographic image on a display.