JP3034809B2 - Ultrasound diagnostic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus having a plurality of reception phasing addition circuits, and more particularly, to an ultrasonic diagnostic apparatus in which an output signal has a plurality of reception phasing and signal-to-noise ratios (S / N ratios). The present invention relates to preventing deterioration due to switching noise of a switch for switching an addition circuit.

[0002]

2. Description of the Related Art The reception dynamic focus method conventionally used is a method for obtaining a high-resolution image over the entire area of a transducer array from a short distance to a long distance. According to this method, the focus point is sequentially switched from a short distance to a long distance at the time of reception with respect to one transmission of the ultrasonic wave, and thus one point is received.
Obtain scan data.

FIG. 3 is a block diagram of a conventional ultrasonic diagnostic apparatus that performs dynamic reception focusing. This device has two systems of receiving and phasing addition circuits 2 and 4, and obtains one-way scanning data while switching these circuits by a switching circuit 6. That is, one of the reception phasing addition circuits is set at a certain focus point, and the switching circuit 6 converts the reception signal subjected to the phasing addition processing in the one reception phasing addition circuit into a B-mode signal processing circuit 8 and a spectrum Doppler signal. While outputting to the signal processing circuits such as the processing circuit 10 and the color Doppler signal processing circuit 12, the other reception phasing addition circuit adjusts the amount of delay of the reception signal between the respective vibrators to a longer distance. Control is performed to set a focus point. As described above, the reception phasing addition circuits 2 and 4 perform the phasing addition processing on the received signal when selected by the switching circuit 6 and output the signals, and when not selected, perform the focus point setting change operation. By alternately selecting the wave receiving and phasing addition circuits 2 and 4, the focus points are sequentially taken at deep positions, and one scan data is formed.

[0004] Here, the switching circuit 6 generates switching noise when switching the plurality of reception phasing addition circuits 2 and 4, which causes deterioration of the S / N ratio of the received signal and the image quality of the tomographic image. It causes deterioration. For this reason, consideration is given to suppressing switching noise in the switching circuit 6.

[0005] Now, an ultrasonic reception signal handled by an ultrasonic diagnostic apparatus has a very wide dynamic range.
TGC (Time Gain Compensation) circuit, STC (Sens)
Even if a circuit such as an iterative time control circuit is used to correct the difference in attenuation due to the perspective difference of the reflection point, the dynamic range is as large as 50 to 60 dB. On the other hand, CRT
Since it has only a dynamic range of about 20 to 26 dB, it is not possible to faithfully reproduce a tomographic image of a received signal having the wide dynamic range. Further, even if the image is faithfully reproduced, the contrast is too strong for the naked eye, and it is difficult to substantially recognize a target object from a bright portion to a dark portion. Therefore, in processing for generating a tomographic image based on the intensity of a received signal such as a B-mode tomographic image, logarithmic compression of the received signal using a logarithmic converter has been conventionally performed, that is, a signal of a higher level signal has a higher level than a lower level signal. Reduction of the amplification factor has been performed. In the apparatus of FIG. 3, the LOG amplifier 14 between the switching circuit 6 and the B-mode signal processing circuit 8 is provided for performing the logarithmic compression on the received signal.

[0006]

As described above, the switching circuit 6 suppresses switching noise. However, even though the switching noise is suppressed in the switching circuit 6, it is amplified in the LOG amplifier 14, so that conventionally, a sufficient S / N ratio cannot be secured, and this noise appears on the tomographic image and the image quality is reduced. There was a problem of deterioration.

In order to solve this problem, the rise of a control signal for switching an electronic switch (switch) in the switching circuit 6 is moderated, and the capacitance and inductance distributed to each part of the switching circuit are adjusted to perform switching. Measures have been taken to suppress overshoot and electrical vibration. However, there is a problem that these adjustments are delicate and difficult, and are inefficient because they must be performed for each device. There is a problem that a switch with less noise is expensive and increases the cost of the device. In addition, a high-speed switch is used to shorten the noise generation period to reduce the influence of the noise. However, the high-speed switch is expensive, and there is a problem that the cost of the device increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an ultrasonic diagnostic apparatus in which the influence of switching noise of a switching circuit is suppressed easily and at low cost and the S / N ratio of a received signal is improved. The purpose is to provide.

[0009]

An ultrasonic diagnostic apparatus according to the present invention comprises a plurality of transducers for transmitting and receiving ultrasonic waves, and a plurality of circuits arranged in parallel and selectively used, each of which is provided with a respective one of the above-mentioned respective oscillators. A plurality of reception phasing addition circuits for phasing addition of the reception signals output from the
A switch for selecting one of the outputs and the output from the switch
Eco that performs echo signal processing based on the received signal input
-An ultrasonic diagnostic apparatus including a signal processing circuit,
Provided each of said received wave phasing addition circuit to an input side of the switching device, have a plurality of logarithmic converter for converting a logarithmic received signal based on an output of the reception delay-and-sum circuit logarithmically
Is what you do .

According to the present invention, the logarithmic converter is provided before the switch, that is, for each reception phasing addition circuit. As a result, the switching noise of the switch is superimposed on the received signal after the small signal range is extended. That is, for example, as a received signal before the logarithmic converter,
Considering a small signal that is about the same as switching noise,
After passing through the switch, i.e. the logarithmic converter,
This small signal has a larger amplitude than the switching noise, that is, the switching noise is relatively compressed. On the other hand, a large signal range of the received signal is compressed as compared with a small signal range because it is a logarithmic transformation rather than a simple amplification. Therefore, for example, there is no change in other circuits of the device such as expansion of the input range of the switch, and the conventional circuit can be used as it is.

An ultrasonic diagnostic apparatus according to the present invention includes an exponential converter for converting a logarithmic reception signal output from the switch based on an exponential function. In the ultrasonic diagnostic apparatus according to a preferred aspect of the present invention, the echo signal processing circuit has a Doppler signal processing circuit that performs Doppler processing , and the exponential converter is arranged on an input side of the Doppler signal processing circuit. Is done.

According to the present invention, for example, when performing Doppler processing or the like that does not require compression of the dynamic range of a received signal, which is processing using phase information of the received signal,
After the conversion by the logarithmic converter, one of the plurality of reception phasing and adding circuits, that is, the logarithmic reception signal is selected by the switch, and then the logarithmic reception signal is returned to the linear reception signal by the exponential converter. As a result, a linear reception signal in which the switching noise of the switching device is compressed is supplied to a signal processing circuit using a linear reception signal, for example, a Doppler signal processing circuit, and signal processing with little influence of the switching noise can be performed. Becomes In addition, other than the present invention
In a preferred embodiment, the echo signal processing circuit is a B-mode
A B-mode signal processing circuit for performing the processing.
This is an ultrasonic diagnostic apparatus.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to the present invention that performs reception dynamic focus. This device is the same as the above-mentioned conventional device in a fundamental point that one-way scanning data is obtained by switching two systems of the wave receiving and phasing circuit by a switching circuit. However, the present apparatus differs from the conventional apparatus in that the present invention is implemented and the S / N ratio is not deteriorated by the switching noise of the switching circuit. Hereinafter, the configuration of the present apparatus will be described in detail focusing on this difference.

Transducer array 30 arranged in probe
Transmits and receives ultrasonic waves while being pressed against an object to be inspected, for example, a living body. That is, the transducer array 30 receives the transmission signal generated by the transmission circuit 32 and emits an ultrasonic pulse into the living body. The ultrasonic pulse generates a reflection having an intensity corresponding to a change in the acoustic impedance of the tissue in the living body. The reflected wave is detected by the transducer array 30 and becomes a reception signal of a plurality of channels. The reception signal is amplified by the preamplifier 34. Thereafter, the received signal is input to two reception phasing addition circuits 36 and 38 provided in parallel with each other, and the reception processing phasing addition circuits 36 and 38 perform an addition process between the transducers. The reception phasing addition circuit can perform reception focusing by shifting the reception signal between the transducers and performing the addition processing. The position of the reception focus can be changed by adjusting the amount of delay for the reception signal between the transducers.

As in the conventional apparatus, two reception phasing addition circuits 36 and 38 are provided to perform reception dynamic focus. In other words, while one of the reception phasing addition circuits performs addition processing corresponding to a certain focus point, while the reception signal is selected by the switching circuit 40 and output to a signal processing circuit such as tomographic image generation, the other reception phasing addition circuit performs the addition processing. Performs the operation of changing the delay amount corresponding to each transducer to set a focus point at a longer distance than the currently selected one of the reception and phasing addition circuits. When the response time of the reflected wave, that is, the time from transmission to reception is within the range according to the focus point of the other reception phasing addition circuit, the switching circuit 40 is switched, and the output on the other side is selected. And outputs it to the signal processing circuit. Thus, in the reception dynamic focus, the reception phasing addition circuit 3
Reference numerals 6 and 38 denote phasing addition processing of the received signal when selected by the switching circuit 40 and output the same. When the selection signal is not selected, the focus point setting is changed, and the switching circuit 40 alternates the reception phasing addition circuits 36 and 38. , The focus point is gradually changed to a position far from the transducer array, and one scan data is formed. With this reception dynamic focus, high-resolution scanning data and images can be obtained over the entire area from a short distance to a long distance of the transducer array.

A major feature of this apparatus is that LOG amplifiers 42 and 44 each having a function as a logarithmic converter are connected to the outputs of the wave receiving and phasing addition circuits 36 and 38, respectively. The purpose is to select and output one of the logarithmic reception signals output from 42 and 44. This operation will be described later.

The B-mode signal processing circuit 50 includes a switching circuit 4
A logarithmic received signal is input from 0, tomographic image data corresponding to the received signal strength is generated, and output to the image display 52.
In this B-mode signal processing circuit, as described in the related art, processing is performed using the logarithmic reception signal without inversion.

On the other hand, the spectral Doppler signal processing circuit 54 and the color Doppler signal processing circuit 56 perform processing based on phase information in the received signal. In the processing using these phase information, a circuit that extracts the phase information from the logarithmic reception signal and performs the processing is also possible. However, in this apparatus, an inverse LOG signal is provided before the spectral Doppler signal processing circuit 54 and the color Doppler signal processing circuit 56 so that a circuit having the same configuration as the conventional one can be used for the spectral Doppler signal processing circuit 54 and the color Doppler signal processing circuit 56. An amplifier 58 was provided.
This inverse LOG amplifier has a function as an exponential converter,
The logarithmic reception signal from the switching circuit 40 is returned to a linear reception signal by the inverse LOG amplifier. Incidentally, the spectrum Doppler signal processing circuit 54 analyzes the frequency of the received signal. Further, the color Doppler signal processing circuit 56 performs an autocorrelation process to form a Doppler image. The image data generated by the spectral Doppler signal processing circuit 54, the color Doppler signal processing circuit 56, and the B-mode signal processing circuit 50 are transmitted to the image
digital scan converter) and displayed on a CRT at a predetermined frame rate.

Next, the operation of the part relating to the switching of the reception phasing addition circuit, which is a feature of the present apparatus, will be described. FIG. 2 is a schematic diagram illustrating an example of a relationship between a received signal level and a switching noise level in each unit of the present device. The vertical line segment located on the left side of FIG. 2 indicates the dynamic range of the received signal at the input of the LOG amplifier. The dynamic range of the received signal is, for example, 100 μV to 1 V (−80 d
B to 0 dB). That is, the maximum value of the received signal is 1
V, the noise level contained in the received signal is 100 μV. The signal compression ratio of the LOG amplifiers 42 and 44 is set to 0.1 V /
Assuming 10 dB, the dynamic range of the logarithmic received signal obtained corresponding to the amplitude range of the received signal is 0.2 V to 1 V as shown by the vertical line segment located in the center of FIG.
Is converted to In this apparatus, the logarithmic reception signal is input to the switching circuit 40, and in this switching circuit 40, switching noise of a switch for switching the path of the reception signal is superimposed. Assuming that the amplitude of the control signal for turning on / off the switch is, for example, 5 V, the amplitude of the switching noise is, for example, about 0.1 V. That is, in this example, the switching noise has a noise signal level 0.2 in the logarithmic reception signal.
Below V.

On the other hand, conventionally, a LOG amplifier 14 is provided after the switching circuit 6 as shown in FIG. Therefore, the switching noise is superimposed on the received signal represented by the left vertical line in FIG. 2, and the switching noise level of 0.1 V exceeds the noise level of the received signal of 100 μV, and the S / N ratio is increased. Had deteriorated. On the other hand, in the present device, as described above, the switching noise level is lower than the noise level of the received signal, so that it is intuitively understood that the S / N ratio is improved as compared with the conventional device. I have.

This improvement will be concretely shown based on the numerical values exemplified above. The vertical line segment located on the right side of FIG.
5 shows the dynamic range of the received signal at the output of the amplifier 58. To facilitate comparison, the reverse LOG amplifier 58
Is 10 dB / 0.1V. That is, the dynamic range of the received signal represented by the vertical segment on the right in FIG. 2 has the same scale as the dynamic range of the received signal represented by the vertical segment on the left. Due to the exponential conversion by this inverse LOG amplifier, 0.1 V in the level diagram at the center of FIG.
2 is converted to 10 μV, that is, −90 dB, as shown in the level diagram on the right side of FIG. 2, and is suppressed from the noise level of the received signal −80 dB, so that the S / N ratio of the received signal does not deteriorate. . On the other hand, in the conventional device, as described above, the switching noise level is set to 0.
1V, that is, −20 dB, which is much higher than the noise level of the received signal −80 dB. In the example described here,
This device has 70dB less switching noise than the conventional device.
Can be suppressed.

The present apparatus is characterized in that signal compression is performed using LOG amplifiers 42 and 44. The received signal has a dynamic range smaller than the upper limit of the input range of the electronic switch as a switch by logarithmic conversion by a LOG amplifier.
And it is converted to a range larger than the switching noise level, and then passes through the switching circuit 40. Therefore, in the switching circuit 40, S / N due to switching noise
Neither the deterioration of the ratio nor the distortion for large signals due to the influence of the input range of the switch occurs. In general, simply amplifying a received signal should satisfy both the condition that the upper limit of the dynamic range does not exceed the upper limit of the input range of the switch and the condition that the lower limit of the dynamic range does not fall below the switching noise. Is difficult. On the other hand, the signal compression of the present apparatus differs from simple amplification in that it is not subject to such restrictions. That is, according to the present device, as a switch for switching between the two reception phasing and adding circuits, it is not necessary to increase the upper limit of the input range as compared with the related art, and the condition regarding the level of the switching noise is also higher than the upper limit of the input range. Thus, for example, it can be set gently to about -20 dB, and an inexpensive switch can be employed.

In the present apparatus, the reception phasing addition circuit is 2
However, three or more systems may be used.

[0024]

According to the ultrasonic diagnostic apparatus of the present invention, even if a low-cost switch is used, the received signal is not affected by the switching noise of the switch, and the S / N ratio of the received signal is improved. The effect is obtained. Further, since the cost of the switching device can be reduced, the cost of the device can be reduced. Furthermore, since it is less susceptible to switching noise, it is not necessary to adjust the circuit to reduce switching noise only by incorporating normal components as a switch, thereby improving the production efficiency of the equipment and facilitating maintenance. Also, effects such as performance stabilization can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to the present invention which performs reception dynamic focus.

FIG. 2 is a schematic diagram illustrating an example of a relationship between a received signal level and a switching noise level in each unit of the device.

FIG. 3 is a block diagram of a conventional ultrasonic diagnostic apparatus that performs reception dynamic focus.

[Explanation of symbols]

30 transducer array, 32 transmission circuit, 36, 38 reception and phasing addition circuit, 40 switching circuit, 42, 44 LOG amplifier, 50 B mode signal processing circuit, 54 spectrum Doppler signal processing circuit, 56 color Doppler signal processing circuit,
58 Reverse LOG amplifier.

Claims (4)

(57) [Claims] 1. A plurality of transducers for transmitting and receiving ultrasonic waves, and a plurality of circuits arranged in parallel and selectively used, and phasing and adding reception signals output from the respective transducers. A plurality of reception phasing addition circuits, and these reception phasing addition circuits
A switch for selecting one of the outputs of the adding circuit;
Signal processing based on the received signal output from the converter
And an echo signal processing circuit for performing
There are, the switching the input side of the exchanger is provided for each received wave phasing addition circuit, a plurality of logarithmic converter for converting a logarithmic received signal based on an output of each of the received wave phasing addition circuit logarithmically
Ultrasonic diagnostic apparatus characterized by having a. 2. The ultrasonic diagnostic apparatus according to claim 1, further comprising an exponential converter that converts a logarithmic reception signal output from said switch based on an exponential function. 3. The Doppler signal processing circuit according to claim 2, wherein the echo signal processing circuit includes a Doppler signal processing circuit that performs Doppler processing , and the exponential converter is disposed on an input side of the Doppler signal processing circuit. Ultrasonic diagnostic equipment. 4. An echo signal processing circuit, comprising :
A B-mode signal processing circuit for performing
The ultrasonic diagnostic apparatus according to claim 1.