JPS59103655A - 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 The present invention relates to an electronic scanning ultrasonic diagnostic device, and particularly to a probe? The present invention relates to an ultrasonic diagnostic system that corrects variations in the transmission and reception characteristics of the constituent ultrasonic transducers. FIG. 1 is a block diagram showing the electrical configuration of a conventional general electronic scanning ultrasound diagnostic apparatus. That is, in Fig. 1, (1) is a probe made of piezoelectric material such as PZT (zircon Φ, lead titanate porcelain), in which dozens of ultrasonic transducers 18 to JNk are arranged in an array. Perform bidirectional conversion, 28~
2N is a transmitter/receiver unit that sends a transmission pulse with a peak value of several tens to several hundreds of volts and a pulse width of several tens to several hundred n5ec to the probe 1, and amplifies the echo signal from the probe 1 by about 20 times. Reference numeral 3 denotes a transmission trigger generation section, which receives a transmission start signal from the control section 4 and sends out a transmission trigger pulse to each of the transmission/reception sections 211 to 2N. At this time, each transmit trigger pulse is usually 111i! Since the i delay 2Nk is sequentially selected and operated in chronological order, it is necessary to selectively apply the transmission trigger pulse to the transmitting/receiving sections 2R to 2N which are to be operated.

The transmission trigger generation section 3 performs all processing related to such transmission trigger pulses. 5 is to give the echo signal from each ultrasonic transducer the same delay as when transmitting K.
This is a delay adder that gives the directivity and focus of the receiving probe 1 during reception. Reference numeral 6 denotes a logarithmic amplification and detection section which logarithmically compresses the addition output of the received signal and extracts the low frequency range of this signal to obtain a video signal. 7 is a signal processing unit, which enables adjustment of gain, dynamic range, TGC (time gain compensation), etc., and also performs automatic adjustment of AGC (automatic gain compensation), etc. 8 is a digital scan converter; signal processing unit 7
9 is a TV monitor that displays an ultrasound tomographic image using this signal.

The operation of the electronic scanning ultrasonic diagnostic apparatus configured as described above will be described below.

In FIG. 1, a pulse indicating the start of transmission and an address signal indicating whether the transmission corresponds to the scanning line pressure on the TV monitor 9 are sent from the control section 4 to the transmission trigger generating section 3 and the digital scan converter 7. For example, in the case of sector scanning, the transmission trigger generating section 3 knows the inclination and focus of the ultrasonic beam to be applied from the received address signal, and adjusts the transmitting/receiving section 2s so as to satisfy them.
Send a transmission trigger pulse with a necessary delay of ~2NK%. Each of the transmitter/receivers 28 to 2N receives the transmission trigger pulse and at the same time transmits the corresponding ultrasonic transducer in the probe l.
Apply a transmission pulse to IN to emit ultrasonic waves. In this way, with an appropriate delay, the ultrasonic transducers 111~
When IN' is excited, a composite wave of ultrasonic waves emitted from them can be transmitted as an ultrasonic beam at an arbitrary inclination to a living body to be observed. The radiation surface of the probe I is brought into close contact with the living body, and the ultrasonic beam propagates through the living body, is reflected at interfaces with different acoustic impedances, and is received by the probe IK again. Ru. This received ultrasonic reception echo is converted into an electrical signal, and the transmitter/receiver parts 2s to 2N
The received signal is amplified several tens of times at n. On the other hand, the address signal from the control unit 4 is also input to the delay adder 5, and each of the received signals is delayed under the same conditions as when f' is given at the time of transmission. The image quality and focus are set to match the image quality and focus at the time of transmission. The received signals added here are logarithmically compressed and detected by a logarithmic amplification and detection section 6 to become a video signal. Furthermore, the signal processing unit 7 performs various processing, and the digital scan converter 8 converts the scanning method.
A B-mode tomographic image of the living body is formed on the TV monitor 9.

FIG. 2 is an enlarged perspective view showing the external appearance of the probe 1 of FIG. 1. Note that the same parts are denoted by the same reference numerals throughout FIGS. 2 to 10, and redundant explanation will not be given.

In FIG. 2, the ultrasonic transducers 18 to IN are currently mainly made of ferroelectric piezoelectric ceramics such as KPZT or the like, which are polarized as described above.

108 to ION are slits which can be cut into the cube-shaped piezoelectric ceramic with a wire saw or the like.

The ultrasonic transducers 1m to IN are electrically divided by the ultrasonic transducers 108 to IOH.

118NIIN, l2 is an electrode made of Ag, 11
8 to IIN are the hot side, and 12 is the common ground side. These electrodes 118~IIN, 12 are connected to each transmitter/receiver circuit 28~
2N via a cable (not shown).

Reference numeral 13 denotes a matching layer that efficiently propagates the ultrasonic waves generated by the ultrasonic transducer into the living body. Epoxy resin is often used for the simplest layer matching. 1
4 is a probe 1 with an A-acoustic lens made of silicone resin.
The cross section in the direction perpendicular to the longitudinal direction is shaped like an arc. This is to focus the ultrasonic beam in this direction. In addition, the ultrasonic transducer 18 ~ INIfi
In a free state, even if a pulsed voltage is applied, the natural vibration persists, so the ultrasonic wave with a long tail is emitted, degrading the resolution in the depth direction in the B-mode tomographic image.For this reason, a damping layer 15 is installed on the back surface. It is necessary to provide a damper to quickly damp vibrations. This damping layer 15 is made of vinyl chloride mixed with tungsten.

Now, the ultrasonic transducer 1 is usually made by mixing raw materials, molding them, and then sintering them at around 1000°C.In this high-temperature sintering process, lead (Pb) has a high vapor pressure, so the material The rate at which gas escapes from the surface increases. Therefore, in the crystal obtained after sintering, the composition of the material changes between the surface and the bulk part, and even within the same material, non-uniformity in piezoelectric constant, dielectric constant, etc. is observed. become.

Furthermore, since piezoelectric materials are non-electrostatic, charges are generated on the electrodes due to rapid temperature changes, and the electric field created by these charges impairs the spontaneous polarization of the piezoelectric material. Regarding this group, due to the poor thermal conductivity of PZT, a temperature difference occurs between the near surface and the bulk part, and due to the difference in the current n direction of the pyroelectric effect, the piezoelectric constant and elasticity of the heterogeneous kinetics deteriorate in polarization. Inconsistencies appear in constants and capacitances.

When the various constants of the ultrasonic transducer are different in this way, there is a problem in that the side ropes due to variations in the ultrasonic beam increase during emission of ultrasonic waves, making it impossible to obtain the desired fairly directivity characteristics. Furthermore, when receiving ultrasonic echoes, there is a problem in that unevenness in brightness contrast within a tomographic image occurs due to variations in received signal levels.

The present invention is not based on the above-mentioned problems.
The purpose of this is to detect variations in the transmission and reception characteristics of each ultrasonic transducer before diagnosis, and use the information obtained to equalize the level of ultrasonic waves during emission to eliminate side ropes. It is an object of the present invention to provide an ultrasonic diagnostic apparatus that suppresses the contrast, obtains sharp directivity characteristics, and does not cause contrast unevenness due to correction.

In order to achieve all of the above objects, the present invention transmits the same transmission pulse to each of the plurality of ultrasonic transducers constituting the probe.
The 11th order is given, and the wave is transmitted from the ultrasonic transducer by each transmission pulse! Completely reflects the ultrasonic wave f', and gives it to each of the ultrasonic transducers at the time of diagnosis based on the size of the received pulse obtained by completely receiving the completely reflected ultrasonic wave f'. It has an information detection means for obtaining peak value determination information for determining the pulse height value of the transmitted pulse and gain level determination information for determining the gain level of the received signal, and according to the pulse height determination information from the information detection means. The wave height value of the n transmission pulses supplied to each ultrasonic transducer is determined, and the gain of the received signal is controlled in accordance with the gain level determination information from the information detection means.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a diagram showing the ultrasonic transducer and the transmitting/receiving section in an all-pole type manner to explain the method for correcting the transmitting/receiving characteristics in the ultrasonic diagnostic apparatus according to the present invention. The figure I (b) shows the figure before, and I (b) shows the figure after correction.

N In Fig. 3(a), 1 is the probe, 2 is the transmitting/receiving section, and the upper row 2aa, 2ba, ... #2Na is the transmitting lower row 2ab, 2bb, ..., 2Nb is the receiving section. In the figure (b), 2/(, -r, correction coefficient 1 to l(n) indicate the transmitting and receiving parts that correct the transmitted and received signals, and the upper row 2' a a , 2' b s ,−,
2'NR is a transmitter, lower stage 2'ab.

2' h b , . . . , 2' Nb The Id receiving sections are each shown as follows. In addition, each ultrasonic transducer (hereinafter sometimes referred to as a transducer) 12 ~ IN ~ ξl ~ ξN of the probe l is given by each transducer and other conditions. Electrical sound I#l conversion coefficient for each transmission 8112ab
Jbb.

...2Nb and 2'Ilb, 2'bb
, -, rt written in 2'Nb, *α represents the gain when obtaining the received signal.

Now, for the sake of simplicity, the ultrasonic beams emitted from each ultrasonic transducer 1a to IN do not spread, and all the ultrasonic beams emitted from the i-th transducer are received by the i-th transducer.
- Absorption/scattering along that path and absorption/transmission by the reflector are not accepted. If it is assumed that the ξ quantity represents only the electroacoustic conversion coefficient specific to the i-th vibrator.

In the same figure (a), if a transmission pulse of wave peak value Vo is given to each transducer 1a-IN, the ultrasonic beam radiated by each transducer 18-IN is reflected by the perfect reflector 16. Almost 100% of the wave is reflected back to each vibrator. At this time, each vibrator is a receiver 2sb to 2N.
The magnitude of the signal output to b is ξi VO (1=J −n
) is expressed as -y t.

This signal is amplified by α times in the receiving sections 2ab to 2Nb lr
The received signal Vt=aξ1Vo(i=?~nl).

When the correction coefficient is multiplied by 1tl-the respective gains of the transmitting sections 20 to 2NB and the receiving sections 2ab to 2Nb of the transmitting/receiving section 2, the result is as shown in FIG. 3(b).

That is, in FIG. 3(b), if the magnitude of the transmission pulse given to each vibrator 18 to IN is K i Vo, the transmission pulse is corrected unique to each vibrator.

Here, the magnitude of the above transmission pulse is as follows. Therefore, the magnitude of the ultrasonic wave transmitted from each transducer with a wave length t'' is JT'
;; Since it is a constant determined by VO, all the vibrators will transmit ultrasonic waves of the same magnitude.

As can be seen from the figure, the signal obtained by each vibrator receiving the ultrasonic wave is ξI K I Vo. Therefore, this signal is amplified by K14 times and obtained (i! times signal ■+=αξiKi”Vo... (4)=
Since αξ−VO, n is also at a constant level, making it possible to obtain a received signal in which the dispersion elements of each vibrator have been corrected.

After that, the data is received by the transmitting/receiving section 2 in Fig. 3 (-).
When calibrating the overdetermined value obtained from the same signal vl, we will explain the case in which the gain of the transmitted pulse and received signal is corrected in the transmitting/receiving unit 2' in cycle (b) as the diagnosis time. FIG. 1 is a block diagram showing the electrical configuration of the ultrasonic diagnostic apparatus according to the present embodiment.

In FIG. 4, a microcomputer 17 controls the electronic circuit, stores data, sends calculation commands, etc. 1
A switch 19 is a demultiplexer for putting the 8d device into calibration mode, and a transmitter/receiver circuit that transmits a correction transmission trigger pulse output from the microcomputer 17 or an address key signature j output from the microcomputer 17. Select. Mysterious hand hanya≠－゛－－
20 is a data selector that selects the output of the demultiplexer 19 during calibration and the output of the transmission trigger generator 3 during diagnosis according to the instructions from the microcomputer 17. . Reference numeral 21 denotes an analog switch, which sends the received signal t to the next-stage multiplexer during calibration, and to the delay adder 4 during diagnosis, in accordance with the instructions from the microcomputer 17 as described above. The received signal from the i-th transducer selected by the multiplexer 22 is subjected to detection and linear amplification in the detection amplification section 23. 24 is a peak detecting section.
A sample and hold section (hereinafter abbreviated as peak 1 hold section) determines the arrival time of the echo to be captured from the sound speed of the transmission medium, and gates the received signal at that timing. Next, measure the maximum peak value of the Ijima that was taken and hold that value. 25 is an N-converter.

In the apparatus having the above configuration, the operation during calibration will be explained. First, when the switch 18 is pressed, the microcomputer 17
The command outputs the command, causes the data selector 20 and analog switch 21 to select the demultiplexer 19 and the multiplexer 22, and puts the device into the calibration mode. Next, the microcomputer 17 outputs the address signal (large=1) to the demultiplexer 19 and the multiplexer 22, and the first transmitter/receiver and vibrator are selected.

When the above preparations are completed, the microcomputer 17 outputs a transmission trigger pulse ST't for calibration, turns the demultiplexer 19 and data selector 20 red and white, and generates a transmission pulse VO from the first transmitting/receiving section. Vibrator 1
s% (excite.

This vibrator 1a faces the perfect reflector 16 as explained in FIG. The echo from the perfect reflector 16 is sent to the first transducer 18, the transmitter/receiver 2a, and the analog switch 2.
), passes through 22 multiplexers, and is extracted in the detection and amplification section 23 in the low frequency range to become an n5 received signal. Actually, in addition to the transmission pulse, the received signal output from the detection amplification section 23 includes the reflector 1
There are also multiple reflection echoes between the probe 1 and the probe 1. Therefore, the peak hold section 24 first multiplies the signal by f) to extract only the desired received signal, and then performs peak detection.・Perform sample and hold.The peak value of this received signal Vl width converter 25
After being converted and stored in the microcomputer 17. Thus, the above procedure side'1=1.2. ...,
If this is repeated for n, a sequence Vi (i=1 to n) of peak values of the received signals from each element will be obtained.

Various methods can be considered for performing calibration using Vil, and examples thereof will be explained based on FIGS. 5 to 10.

FIG. 5 shows the transmitting section 2'5 of the transmitting/receiving section 2'a in FIG.
2Ik is a circuit diagram showing the peak value of the transmission pulse given to each vibrator. In the same figure, SD+, S
D2 is a high-speed switching element that is turned ON only while a pulse is being applied to the GATE terminal. R1 is a charging resistance of the capacitor C, L is a tuning inductor of the vibrator element 1, and R2 is a damping resistance of the resonant circuit formed by the vibrator element 1 and the tuning inductor. Further, the peak value voltage VO of the transmission pulse explained in FIG. 3(a) is applied to terminals H and V in the figure. Usually, in an ultrasonic diagnostic apparatus, several white volts are used for this VO.

In the same figure, first, the charge accumulated in CK is zero and SD
2 is OFF, and the moment when SL)+ is turned ON, the potential V(RI) at point P rises from zero at a speed determined by the time constant T formed by R1 and C. The curve shown in FIG. 6 is illustrated.

That is, ■(su = Vo (1-exp('yf, 4) ・
-----・(When SDs is turned off at 5J time τ, the potential at point P is Vok = Vo (1-exp (-
”/Tth...keep n (6) (however, k=
1-n). Therefore, when τ is ≦1, SDz ′ is several tens of n5e.
cON and n is & A ([7> A transmission pulse of 1 Vok is applied to the vibrator 1a and 9 ultrasonic waves are emitted. Therefore, in order to transmit a transmission pulse with a peak value of Vok, the entire charge of the capacitor C must be After releasing, τ,, = T In (1-VOk/V0) ・-・
- It is sufficient to turn on SD+k only during (7). Therefore, the control signal Sc is applied to the gate of SDt.

The gain changes depending on the gain control voltage φj applied to the terminal. Now, if the maximum gain of this amplifier is α, then
The gain required to correct the vibrator 18 during reception is Kj
Since α, KJ α = f(φj)...
(8) is obtained. Therefore, the gain control voltage φj necessary for correction is φj=f−'(Kjα) (9).

As described above, the correction coefficient Ki% required for correction during transmission by the peak value of the transmission pulse and correction during reception by gain control is the pulse width 1tk of the control signal.
A flowchart for calculating the gain control voltage φj and the gain control voltage φj is shown in FIG. That is, in FIG. 7, (a) is a calculation with a correction coefficient of 1, and the peak value vi(1
= 1 to n), find the minimum value VgaR among them,
Each correction coefficient Kif is determined according to the above-mentioned equation (1).

In addition, the pulse width τk of the control signal SC of the Fi transmission pulse ((1) in the same figure) is calculated.

That is, the wave height of the transmission pulse is obtained by multiplying the wave height value VO of the transmission pulse at the time of calibration by Kk by 7, Vo k = K k Vo -=' (10). Therefore, from equations (7) and (107), the pulse width power of the control signal of the @th transmission pulse tk = -Tin
It is sufficient to use a pulse with a length of (1-Kk)--(11).

In addition, in the same figure (b), the obtained τkk is
8 to 2'H and sequentially stored in the next output interface Tok -8c'.

FIG. 8 shows a block diagram of the above Tok.

In FIG. 8, reference numeral 26 denotes a latch, which takes in τk in accordance with a command from the CPU in the microcomputer 17 when the calculation of τ is completed. 27 is a counter, and following the reset by the transmission trigger pulse during diagnosis, C″LoCKL
Number of oCK pulses It is appropriate that the CLOCK pulse be output from the microcomputer 17 and have synchronization of about 1 μsec. In addition, when the output of the counter 27 matches the latch 26 in the 28V matching circuit, it outputs one pulse. 29 is an RS flip-flop (hereinafter abbreviated as R8-FF), which transmits a transmission trigger pulse ST.
and is reset by the output pulse from the matching circuit 28. 30 is an OR circuit which outputs a p1 control output SC which is a combination of the output of R8-FF29 and a calibration signal 80 indicating that it is time for calibration. In addition, when calibrating the above calibration signal SCA Fi, VC at the time of H4gh% diagnosis
is set to be LOW.

Therefore, first, during calibration, the calibration signal SCA is High.
Therefore, regardless of the expansion side of the output of R8-FF29, O
The control output SC from the R circuit 30 is ) (high, and SDI in FIG. 5 is always ON. In other words, the peak value of the transmitted pulse output during calibration is V,
becomes.

- When the calculation is completed and tk is taken into all the output interfaces Tok, and the device enters the diagnostic mode, peak value control is performed using the control signal SC. Tip 9: As soon as transmission starts, control No. 16 S
C is) (igt+lc, and the transmission is completed. SO in Fig. 5)
2 opens, charging of the capacitor C starts. Also, the counter 270 count starts at the same time as n1
R8 is input into the latch 26 at the instant when
-Reset FF19. As a result, the OR circuit 30 outputs tV! Control No. 16 which becomes High only during this period is output. In this way, the voltage across the capacitor C in FIG. 5 can be set to Vok of 91st period. The above is the method for correcting the transmission pulse peak value during transmission.

On the other hand, in FIG. 7(C), the maximum gain α and the gain control voltage φ' determined by the amplifiers of the transmitter/receiver 15 sections 2'n to 2'H
Necessary gain level determination information φJ? using the relational expression f between j and gain and the already calculated Kj? Calculate this n in the RAM at address j in the microcomputer 17 (
It is housed in a place not shown.

Next, the entire operation for controlling the gain of the received pulse during diagnosis will be explained based on FIGS. 9 and 10 based on 1 and φj.

FIG. 9 is based on the obtained gain level determination information φj,
This is a circuit for outputting the actual gain control 1 torque φ'j.

In FIG. 9, 31 indicates each gain level determination information φj(
digital information)? Converting each gain control voltage φ'J (analog quantity) 4. Converters 328 to 32N are full hold parts that hold the respective gain control voltages φ corresponding to the respective receiving parts l' ab to 2' Nb, and 33 is a converter that receives the address signal j from the microcomputer 17 in FIG. Based on the above, the gain control voltage φ' from the D/A converter 31 is sequentially sampled in the bold part, '328~. This is a selection decoder for holding 92NK.

In other words, in FIG. 9, the microcomputer 17 in FIG. 4 receives an address signal j and a receiving section 2'I! corresponding to the address signal. The gain level determination information of b to 2'Nb is respectively input to the decoder 33 and the D/A converter 31.
ing. For reference, the D/A converter 3 outputs a gain control voltage φ'j based on the gain level determination information. This φ'j is held in the sample hold section 323 selected by the decoder 33 according to the address signal.

By repeating the above operation until J=1 to n, n pieces of φ'j are held.

This series of operations is shown in a waveform diagram as shown in FIG.

That is, in the LOW level period 1'Ml (rest period) of the frame signal of the TV monitor shown by SFK in FIG.
A/1) Conversion pot, sample hold, etc. are performed.

φ' is the output signal of the D/A K converter 31, φl' to φn'
are the gain control voltages held in each of the sample and hold sections 32a to 32N.

According to the above embodiment, the ultrasonic wave can be easily calculated by emitting and receiving ultrasonic waves toward a perfect reflector, and by comparing the wave center values of the received signals obtained at t'. , a correction coefficient Kit to equalize the variation in the electroacoustic conversion coefficient inherent to each transducer, etc., can be known, so this correction coefficient Kl'(r is used to calculate the radiation from each transducer at the time of diagnosis. It is possible to determine the peak value of the transmitting pulse given to each transducer to make the magnitude of the ultrasonic wave uniform, and the gain of the received signal in each receiving section to make the level of the received signal uniform. As a result, when transmitting, the emitted ultrasonic waves are uniform, side lobes are suppressed, and a sharp directional characteristic is obtained.At the same time, when receiving, the emitted ultrasonic waves are uniform. A received signal with suppressed variations can be obtained.

As described above, according to the present invention, it is possible to reduce the increase in side lobes of ultrasound beams caused by variations in electroacoustic conversion coefficients that originally occur in each transducer, and the brightness of tomographic images on a TV monitor due to variations in received signal levels. Since problems such as uneven contrast are resolved, clear tomographic images can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical components of a conventional ultrasonic diagnostic device, and FIG. 2 is a perspective view showing a probe consisting of an ultrasonic wave sensor with a number of filters. FIG. 10 is a diagram showing a simple embodiment of the present invention, FIG. A diagram schematically showing the transmitter/receiver section, FIG. 4 is a block diagram showing the electrical explanation of this embodiment, and FIG. 5 is a circuit showing a circuit that generates all the transmission pulses in the transmitter section of FIG. 4. -1 6th
The figure is a 1-waveform diagram showing the potential at point P in the circuit of Figure 5, and Figure 7 is a flow n diagram showing the arithmetic processing performed by the microcomputer. Same figure (b)
8 is a circuit diagram showing a flow chart for determining the pulse @ of a transmission pulse, a flow chart for determining gain level determination information of a received signal, and FIG. 8 is a circuit diagram showing a circuit for generating the control signal SC in FIG. 5. , FIG. 9 is a circuit diagram showing a circuit that holds a gain control voltage based on gain level determination information, FIG.
Probe, 18~IN...Super tracking transducer, 2s~2N
l 2'n ~2'N...transmission/reception unit, 1014~I
ON...Slit, 11R~11N, 12...11
41L 13... Matching layer, 14... Acoustic lens, 15... Damping layer, 16... Perfect reflector. Applicant's representative Patent attorney Takeki Suzue Figure 5 Figure 6 Figure C1 Folding (1) Figure 8 Sc Figure 10 Commissioner of the Patent Office Kazuo Wakasugi 1, Indication of Case Patent Application No. 1983-212149 No. 3, Amendment Relationship with the case of a person who does

Claims (1)

[Claims] Is the same transmission pulse sent to each of the multiple ultrasonic transducers that make up the entire probe? means for sequentially applying the ultrasonic waves; a reflecting means for completely reflecting the ultrasonic waves transmitted from each of the ultrasonic transducers in response to each of the transmitted pulses applied by the means; Based on the magnitude of the received signal obtained by receiving sound+21 waves, pulse height determination information and the 11th signal of the received signal are used to determine the peak value of the transmitted pulse given to each ultrasonic transducer at the time of diagnosis. information detection means for obtaining gain level determination information for determining the total gain level; and information detection means for obtaining gain level determination information for determining the total gain level; An ultrasonic diagnostic apparatus comprising: means for determining a wave sieve value; and a gain of a received signal obtained from the ultrasonic transducer (1) at the time of diagnosis is given from the information detecting means (rL6) to determine the gain level.