JPH0339145A - Filter for controlling automatically quality of picture in ultrasonic diagnosis apparatus - Google Patents

Abstract

PURPOSE:To make it possible to obtain always and automatically an image with good quality to various examinee with different physical constitutions by furnishing such a control device as an auto gain control automatically controlling a filter characteristics in accordance with the physical constitution of the examinee. CONSTITUTION:A signal RF1 as an output signal of an amplifier 18 amplifying a receiving signal after addition is input in the 2nd filter circuit 101. A signal RF2 of time series output from the filter circuit 101 is input into a dynamic band path filter (D.B.P.F) 19 as the 1st filter circuit. In addition, a transmitting trigger signal Y from a transmitting trigger circuit 16 and a detective smoothing signal Z from a detective smoothing circuit 20 are input into a filter characteristic controlling circuit 102. Characteristics of the filter circuit 101 becomes controllable by an output signal of the filter characteristic controlling circuit 102. The difference in a frequency spectrum of a receiving signal changeable due to attenuation of an ultrasonic wave of each examinee to which only the conventional D.B.P.F can not correspond can be automatically covered.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an automatic image quality adjustment filter for an ultrasonic diagnostic apparatus, and more specifically, an analog part C of an electronic circuit of a medical ultrasonic diagnostic apparatus, hereinafter referred to as an analog electronic circuit. ) relates to an analog filter for automatic image quality adjustment used when receiving ultrasonic echoes from within a human body as a subject and subjecting the received signals to analog processing.

(Conventional technique wf) A medical ultrasound diagnostic device emits an ultrasound beam into a human body and receives the ultrasound reflected from the interface of internal organs with different acoustic impedances between human tissues. This device diagnoses the internal state of the body by displaying these received signals as images.

This ultrasonic diagnostic apparatus is equipped with an analog electronic circuit for converting the reception signal (a) into a digitally processable image signal with approximately 64 gradations.The configuration of this analog electronic circuit will be explained with reference to FIG. do.

In the same figure, reference numeral 11 denotes a probe, inside which is provided an ultrasonic transducer block (hereinafter simply referred to as a transducer block) consisting of a large number of microscopic pieces. The transducer block assembly is configured to emit ultrasonic waves into the human body and to receive ultrasonic echoes from within the human body. Also, 12
is a matrix switch, which selects and switches which set of transducer blocks in the probe 11 transmits or receives ultrasonic waves; scans the order in which these transducer block sets are scanned pitch by pitch; The selection signal from the line selection signal generation circuit 22 is used for selection and switching.

Next, I3 is a transmission circuit, which generates a high-voltage energizing transmission pulse for electrically energizing the vibrator block. Further, 14 is a receiving circuit that receives and amplifies ultrasonic echoes from within a human body. Furthermore, 15 is a delay circuit which operates according to a delay pattern to focus the ultrasonic waves in the human body by phase synthesis when transmitting ultrasonic waves, and also to focus by phase synthesis when receiving them. The delay amount constituting the delay pattern is determined by the delay 1 selection signal generation circuit 23.
It is selected by

Further, 16 is a transmission trigger circuit, which uses a timing pulse for energizing the transducer block in the probe 11 as a transmission trigger signal Y.Delay circuit 15.degree. scanning line selection signal generation circuit 22, delay amount selection signal generation circuit 23. Receiving dynamic band pass filter C described below,
D, B, P, F)19. 1, which is designed to output to a time gain control circuit (hereinafter referred to as 1 circuit, G, C circuit) 21 and a digital circuit 24;
Reference numeral 7 denotes an adder, which adds the received signals of each transducer block after being amplified by the receiving circuit 14 and focused by the delay circuit 15. This addition is performed to convert one ultrasonic beam corresponding to a video signal for each scanning line of an image into time-series signals (hereinafter referred to as R and F signals).

Next, 18 is an amplifier, and the received A signal after addition is amplified in order to effectively operate the subsequent stages, B, P, and F 19. In addition, D, B, P, and F 19 correct the frequency spectrum that changes in the depth direction inside the body by filtering it using filter characteristics that change in the direction of time. It consists of

Next, 20 is a detection and smoothing circuit, which detects the R and F signals as video signals so that the main signal becomes a child signal so that it can be easily A/D converted by the digital circuit 24 at the subsequent stage, and smoothes harmonic components. Output as detected smoothed signal Z.

Furthermore, the T, G, C circuit 21 converts the R and F signals into L due to the brightness of the image on the TV monitor and human visibility.
It is compressed using the OG scale and amplified to a maximum of about 60 dB, and the degree of amplification is determined so that the R and F signals, which attenuate depending on the depth inside the body, have a constant amplitude regardless of the depth inside the body. ing. And T,G.

The digital circuit 24 after the C circuit 21 includes T, G, C
The output signal of the circuit 21 is A/D converted and processed as a video signal.

Next, a series of operations of this analog electronic circuit will be explained.

First, the transmission trigger circuit 16 generates a transmission trigger signal Y.
is generated, and the transmission trigger signal Y is delayed through the delay circuit 15 for focusing of the ultrasonic waves. This transmission trigger signal Y is input to the transmission circuit 13, which generates a high-voltage energizing transmission pulse at a predetermined timing, and this energizing transmission pulse is input to the matrix switch 12 to After selecting which transducer block aggregate to transmit and selecting the scanning order of these aggregates, the probe 11 emits ultrasonic waves into the human body.

At the same time that ultrasound is emitted into the human body, reception of ultrasound echoes from within the human body begins, and the matrix switch 12 selects which transducer block assembly in the probe 11 to receive this received signal and receives it. It is amplified by the circuit 14. Then, an adder 17 is added via a delay circuit tS.
The received signals are added together and one ultrasonic beam corresponding to the video signal for each scanning line of the image is converted into time-series R and F signals.

These R, F signals pass through amplifier I8, and D, B, P, F
The signal passes through a 19° detection and smoothing circuit N20 and a T, G, C circuit 21, is A/D converted by a digital circuit 24, and is processed as a video signal for each scanning line of an image on a television monitor.

Here, the functions of B, P, and F 19 will be briefly explained.

First, ultrasonic waves emitted into the human body are attenuated by scattering and absorption depending on the frequency, and the frequency spectrum shifts to lower frequencies depending on the depth of the body part due to nonlinear distortion and the like. FIG. 6 shows a frequency spectrum that changes depending on the depth inside the body.

In the figure, an arrow d indicates movement from a shallow to a deep part of the body, and as is clear from this figure, as the body part moves deeper, the frequency spectrum approaches lower frequencies.

Therefore, the frequency spectrum of the received chord and wave signals reflected from the human body changes in the time progression direction corresponding to the depth direction of the human body, so the analog circuit of the conventional ultrasound diagnostic device described above Well then.

The filter characteristics are controlled in the direction of time, and B, P, and F 19 are used.

In addition, B, P, F 19 are ultrasonic transmission 1-
It has a filter characteristic that extends continuously over time from the rigger to a frequency region with a low gain of approximately constant value. The filter characteristics are determined based on electronic circuit constants based on the internal attenuation of the person to be diagnosed, who has a constitution similar to that of JR.

(Problems to be Solved by the Invention) As described above, the characteristics of the conventional pastes B, P, and F 19 are set in advance based on a test subject with a substantially standard constitution. For this reason, if the person to be diagnosed does not have a standard constitution, for example, IN! In a full-bodied or muscular person, the received signal input to the analog electronic circuit will have many low-frequency components, so images of both shallow and deep parts of the body may become blurred and unreadable for diagnosis. .

In other words, conventionally, 8.
I), the effect of the filter characteristics of F 19 is different, and this filter characteristic! l! The problem was that no means were provided to correct the situation.

The present invention has been made to solve the above problems,
The purpose of this is to improve the image quality of the ultrasonic diagnostic equipment so that even for various patients with different constitutions, the same good image quality as that for patients with sub-41 constitutions can be automatically obtained. Our goal is to provide self-adjusting filters.

(Means for Solving the Problems) In order to achieve the above object, the present invention automatically adjusts the filter characteristics of D, B, P, and F according to the constitution of the diagnostician.
The analog electronic circuit is equipped with adjustment means such as automatic gain control. More specifically, D.

By adding a filter circuit of a tuned circuit with a variable capacitance diode as a second filter circuit that feeds back the output voltages of B, P, and F and changes the filter characteristics depending on the voltage value, it is possible to improve the constitution of the person to be diagnosed. The filter characteristics are automatically controlled according to the

(Function) Glue in the analog electronic circuit, in front of B, P, and F.

The second filter characteristic changes depending on the output voltage of B, P, and F.
When a filter circuit is installed, the output terminals of D, B, P, and F are connected to the second filter circuit.

The filter characteristics of P and F are like a two-stage single tuning circuit like the staggered tuning method, and the overall characteristics have the required 11'4 wave number band according to the ultrasonic attenuation of the human body. You will get it automatically.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an analog electronic circuit of an ultrasonic diagnostic apparatus including an automatic image quality adjustment filter according to the present invention, and the same components as in FIG. , the following will mainly explain the different parts.

In Figure 1, an amplifier 1 that amplifies the received signal after addition
The R and F signals RF as the output signals of 8 are input to the second filter circuit 101, and this filter circuit 101
The R and F signals RF2 outputted from the transmitter are inputted to the first filter circuit and are input to the B, P, and F signals 19. Also, the transmission trigger signal Y from the transmission trigger circuit 16 and the detection smoothing signal from the detection smoothing circuit 20 The signal Z is input to the filter characteristic control circuit 102, and the characteristics of the filter circuit lot can be controlled by the output signal of the filter characteristic control port m102.
D, B, P, F 19 and filter characteristic control circuit 10
Image quality automatic adjustment filter 10 according to the present invention according to 2
0 is configured.

In this embodiment, the image quality automatic 11-section filter 1 is designed to achieve filter characteristics Q as shown in FIG.
00 works. That is, this characteristic has a required frequency band as a whole, like a staggered tuning system in which the frequency characteristic j+k of a single tuning circuit is two-staged.

In other words, in this embodiment, to briefly explain, the output voltage (detection smoothing signal Z) of the detection smoothing circuit 20 is set to the filter characteristic #
By feeding back to the filter circuit 101 via the control circuit 102, D.8. The output filter characteristics of P and F1a are changed to follow changes in the frequency spectrum due to attenuation of ultrasonic waves within the human body.

Here, the filter times M 101 are D, B, P, F
This filter is a tuned circuit configured with a variable capacitance diode and an inductance similar to No. 19, and the filter characteristics are changed by the output voltage of the filter characteristics control circuit 102. Filter characteristic control circuit 10
2 uses the detection smoothed signal 2 obtained by converting the Tsuchiyama force signal of D, B, P, F 19 into a child signal via the detection smoothing circuit 20 as an input voltage, and outputs the filter circuit 101 at the timing of the transmission trigger signal Y. For the control voltage, the input voltage is integrated from the CR open circuit and converted into a DC voltage to generate the output voltage. Note that the waveform of the output voltage of the filter characteristic control circuit 102 with respect to the time axis versus the amplitude has a sawtooth shape at the timing interval of the transmission trigger signal.

With this configuration, the filter circuit 101
and B, P, and F 19, the required filter characteristics as a whole like the staggered tuning method as shown in FIG. 2 are obtained.
The information can be automatically obtained depending on the constitution of the person to be diagnosed and the attenuation of the ultrasonic waves within the human body.

Next, FIG. 3 shows a specific example of the filter circuit 101 and the filter characteristic control circuit 102.

In the figure, as mentioned above, the R, F signal RF is the output signal of the amplifier 18, the R, F signal RF is the output signal of the filter circuit 101, and the timing interval of the transmission trigger signal Y is the ultrasonic diagnosis This corresponds to the depth direction of the display area of the device. Furthermore, the voltage of the detected smoothed signal 2 has a ten-fold alternating waveform, and its amplitude becomes smaller as the attenuation of the ultrasonic wave becomes larger.

In addition, in the same figure, R4~R are resistors, OF~O
P is an operational amplifier, Trl, Tr2 is F''ET
D, , D are variable capacitance diodes, D, , D are diodes, L, , L2 are inductances, C~C1 are capacitors, VR is a variable resistor (volume), M□, J are The first and second circuit blocks are shown respectively.

Among these, in the first circuit block M□.

Every time the transmission trigger signal Y is input, the transistor switch Tri is turned on and the capacitor C2 is shorted.
After that, the detected smoothed signal 2 is CR by the operational amplifier OP□.
It is integrated. To explain the role of this CR integral,
Simultaneously with the transmission trigger signal Y, ultrasonic waves are emitted in the depth direction inside the body, and ultrasonic echoes corresponding to the detected smoothed signal 2 begin to be received, but the time lapse after this trigger signal corresponds to the depth direction inside the body. , the detected smoothed signal Z becomes smaller as time passes, and the frequency spectrum shifts toward lower frequencies. Therefore, in order to match this phenomenon with the filter characteristics, CR integration is performed to determine the CR constant. be.

Further, the second circuit block M2 operates in exactly the same manner as the first circuit block M1. In this circuit block M2, a variable resistor VR is set in advance assuming a change in the frequency spectrum due to attenuation of ultrasonic waves within the body of a subject with a standard constitution, and integrated by an operational amplifier oP4. The subsequent output voltage is differentially amplified with the output voltage of the first circuit block M in the operational amplifier OP. Here, the output voltage of the operational amplifier ○P is the difference between the detected smoothed signal Z corresponding to the person to be diagnosed and the attenuation of the ultrasound in the normal human body, that is, the actual attenuation of the ultrasound in the person to be diagnosed. This is the difference between the attenuation of ultrasonic waves in a hypothetical standard human body.

The output voltage of this operational amplifier OP, that is, the output voltage of the filter characteristic control circuit 102, is the output voltage of the variable capacitance diode D1.
．． In addition to D, these capacitances change, and the resonance frequency due to the inductance L, , L2 changes, and the relationship between the frequency and the gain ratio of the R and F signals RF, , RF, changes. As a result, as shown in Figure 4,
Changes in frequency spectrum due to attenuation within the human body,
The output filter characteristics of B, P, and F 19 can be tracked, and the image quality of the ultrasound image can be automatically adjusted by automatically covering changes in the frequency spectrum for each patient.

(Effects of the Invention) As described above, according to the present invention, the second filter circuit is provided before the circuits B, P, and F in the analog electronic circuit, and the output voltage of the detection smoothing circuit is fed back to the filter characteristic control circuit. Since the characteristics of the second filter are automatically controlled by the above, conventional glues B, P, and F cannot be used alone.

Differences between patients in the frequency spectrum of received signals that change due to attenuation of ultrasound waves can be automatically covered.

Therefore, for example, it is possible to obtain the same image quality for an obese person or a muscular person who have a constitution that causes high attenuation of ultrasound waves as for a person with a normal constitution, and it is possible to improve the image quality of ultrasound images. can.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram of an analog electronic circuit including an embodiment of the present invention, Fig. 2 is a filter characteristic diagram showing the principle of the invention, and Fig. 3 is a diagram showing the filter characteristics of a second embodiment of the present invention. 4 is a diagram of the filter characteristics in this embodiment, FIG. 5 is a diagram of the configuration of an analog electronic circuit for explaining the conventional technology, and FIG. 6 is a diagram of the filter circuit in the human body. FIG. 3 is a filter characteristic diagram showing changes in frequency spectrum due to attenuation of ultrasonic waves. 12... Matrix switch 14... Receiving circuit 16... Transmission trigger circuit 18... Amplifier 20... Detection smoothing circuit 11... Probe 13... Transmission circuit 15... Delay circuit 17... - Adder 19...D, B, P, F 21...T, G, C circuit 22...Scanning line selection signal generation circuit 23...Delay amount selection signal generation circuit 24...Digital Circuit 100... Image quality automatic adjustment filter 101... Filter circuit 102... Filter characteristic control circuit R□~R□7 Resistor OP~OP5... Operational amplifier T r, , T r2... Transistor switch D D2...Variable capacitance diode D, D4...Diode L, L,...Inductance C0-C3...Capacitor VR...Variable resistance M
,,M2...Circuit block

Claims (2)

[Claims] (1) An ultrasonic diagnostic apparatus equipped with a first filter circuit that filters an analog reception signal of an ultrasonic echo by temporally tracking changes in the frequency spectrum due to attenuation of ultrasonic waves within the subject. In the analog electronic circuit, a voltage signal corresponding to the attenuation of the ultrasound according to the constitution of the subject is transmitted from the output side of the first filter circuit to a second filter connected to a stage preceding the first filter circuit. An image quality automatic adjustment filter for an ultrasonic diagnostic apparatus, characterized in that the characteristics of the second filter circuit are made variable by feeding back to the circuit via a filter characteristics control circuit. (2) The filter characteristic control circuit includes a first circuit unit that integrates a voltage signal corresponding to the attenuation of ultrasound according to the constitution of the subject at the timing of the ultrasound transmission trigger signal, and a a second circuit unit that integrates a voltage signal corresponding to the attenuation of the ultrasonic wave at the timing of the transmission trigger signal; and a second filter circuit that amplifies the difference between the output voltages of the first and second circuit units. The automatic image quality adjustment filter for an ultrasonic diagnostic apparatus according to claim 1, further comprising an amplifier circuit for adding an amplifier circuit.