JPH02147051A - Pulse compressing device for ultrasonic diagnosis - Google Patents

Abstract

PURPOSE:To always execute pulse compression with an optimum referring wave by checking mutual correlation between the referring wave, which is calculated by a referring wave calculating means, and an echo signal from a body to be checked by a correlating means. CONSTITUTION:An ultrasonic oscillator 1 is driven by a transmission/reception circuit 2 and an ultrasonic charp signal is projected. Then, as echo at such a time, a signal 10 to be reference is received by the ultrasonic oscillator 1, converted to an electric signal, supplied through the transmission/reception circuit 2, here, converted to a complex signal and taken into a matching filter 4. In the matching filter 4, the echo signal is taken as the data 11 for referring wave calculating into a referring wave setting part 8. In the referring wave setting part 8, the referring wave is calculated based on the taken data 11 for referring wave calculation and a calculated result is set as referring wave setting data 12 to a correlating circuit 7. By obtaining the mutual correlation between the set referring wave and the echo signal from the real body to be checked, the pulse compression of the echo signal from the body to be checked is executed in the matching filter 4. Then, this signal is supplied through an orthogonal modulating circuit 5 to a display device 6 and an ultrasonic picture is displayed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic diagnostic pulse compression device for diagnosing the characteristics of a subject such as a living body using ultrasonic chirp waves. .

[Conventional technology]

2. Description of the Related Art As a conventional ultrasonic diagnostic apparatus, one that employs a pulse compression method that has been put into practical use in radar has been proposed. This type of ultrasonic diagnostic equipment has a long detection distance,
It has the advantage of providing good distance resolution.
Conventionally proposed ultrasonic diagnostic apparatuses using a pulse compression method use a special SAW filter that uses surface acoustic waves as a matched filter for pulse compression, and therefore have the following problems.

In other words, since the ultrasonic diagnostic apparatus uses a low frequency and a wide bandwidth, it is difficult to manufacture a SAW filter that is compatible with the ultrasonic diagnostic apparatus. In addition, in ultrasonic diagnostic equipment, when measuring a subject with large attenuation using the pulse reflection method, it is necessary to dynamically vary and optimize the filter characteristics depending on the depth at which the reflected echo returns. , S.A.
In the W filter, the filter characteristics are fixed depending on the mechanical shape such as the pitch and length of the electrodes, and the dynamically variable filter characteristics as described above cannot be obtained.

In order to solve the above-mentioned problems, the applicant has
In Publication No. 233369, the echo signal is pulse-compressed by performing cross-correlation by convolving the echo signal waveform and the impulse response waveform (reference wave) of the matched filter in the time domain without using a SAW filter. A pulse compression device for ultrasonic diagnosis has already been proposed. According to this pulse compression device for ultrasonic diagnosis, cross-correlation is obtained by performing convolution integration of an echo signal waveform and a reference wave. Therefore, it is not affected by the frequency used or its bandwidth like a SAW filter, and dynamically variable filter characteristics can be effectively provided.Therefore, it is possible to easily create a high-resolution, high-sensitivity ultrasonic diagnostic device. It has the advantage of being achievable.

[Problem to be solved by the invention]

However, as a result of studies by the present inventor, it has been found that the above-mentioned ultrasonic diagnostic pulse compression device already proposed by the present applicant has the following points that should be improved.

That is, in this ultrasonic diagnostic pulse compression device, the reference wave for pulse compression is set and stored in advance based on the waveform of the impulse signal actually received by the ultrasonic transducer and passed through a matched filter. The reference wave data is stored in a circuit, and thereafter the reference wave data stored in this storage circuit is read to obtain a reference wave.

Therefore, even if the initially set reference wave is no longer optimal due to changes in the ultrasound transducer or circuit elements over time, and the quality of the ultrasound image deteriorates, the reference wave cannot be easily adjusted. be.

This invention was made by focusing on these problems, and provides pulse compression for ultrasonic diagnostics that is appropriately configured so that pulse compression can always be performed using the optimal reference wave according to changes in the ultrasonic transducer over time. The purpose is to provide equipment.

[Means and effects for solving the problem] In order to achieve the above object, the present invention is provided with a reference wave calculation means and a correlation means, and the reference wave calculation means and correlation means are provided to calculate the reference wave based on the echo signal from a predetermined reflecting object of the ultrasonic chirp wave. The reference wave for pulse compression is calculated by the wave calculating means, and the correlation means performs a cross-correlation between the calculated reference wave and the echo signal from the subject to pulse compress the echo signal.

〔Example〕

FIG. 1 shows a conceptual diagram of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention.
, a quadrature detection circuit 3, a matched filter 4, a quadrature modulation circuit 5, and a display device 6. Matched filter 4 is correlation circuit 7
and a reference wave setting section 8, the reference wave setting section 8
is controlled by the control section 9.

In this embodiment, the transmitter/receiver circuit 2 drives the ultrasonic transducer 1 to project an ultrasonic chirp signal whose frequency decreases over time as shown in FIG. A reference signal 10 is received by an ultrasonic transducer l, converted into an electrical signal, and supplied to a quadrature detection circuit 3 via a transmitter/receiver circuit 2, where it is converted into a complex signal and taken into a matched filter 4.

In the matched filter 4, the correlation circuit 7 performs convolution integration in order to correlate with the reference wave, but the echo signal immediately before the convolution integration is sent to the reference wave setting unit 8 as the reference wave calculation data 11. take in. The reference wave setting unit 8 receives reference wave calculation data 11. A reference wave is calculated based on , and the result is set in the correlation circuit 7 as reference wave setting data 12.

The above reference wave calculation and setting operations are controlled by the control section 9. In this way, by taking the cross-correlation between the set reference wave and the echo signal from the actual subject in the correlation circuit 7, the echo signal from the subject is pulse-compressed in the matched filter 4, and this is orthogonally compressed. It is supplied to a display device 6 via a modulation circuit 5 to display an ultrasound image.

With this configuration, the reference wave can be automatically reset by the observer controlling the control unit 9, so that changes in the characteristics of the ultrasonic transducer and circuit elements over time can be avoided. Corresponding calibration (optimization of reference waves) can be easily achieved.

FIG. 3 shows the specific configuration of FIG. 1.

This embodiment shows an ultrasonic endoscope device, in which an ultrasonic endoscope 21 is detachably connected to an observation device 23 via a connector 22. An ultrasonic transducer 25 is provided at the insertion tip of the ultrasonic endoscope 21, and a motor 2
6 through a flexible shaft 27. A signal line (not shown) of the ultrasonic transducer 25 is connected to the slip ring 2 through the flexible shaft 27, and signals are sent and received to and from the ultrasonic transducer 25 via the slip ring 28. There is.

The connector 22 also includes a transducer drive circuit 29, a ROM 30 that stores initial reference wave data set in advance, and a 5-RAM 3 that stores reference wave data calculated by the observation device 23.
1 and its backup circuit 32 are provided, a transmission rate signal is supplied from a transmission circuit 33 provided in the observation device 23 to the transducer drive circuit 29, and a ROM 30 and a 5-RA
The reference wave data (30a, 31a) of M31 is supplied to the D/A converter 34 in the observation device 23, and the reference wave data (C+
i D).

The echo signal received by the ultrasonic transducer 25 is transmitted to the observation device 23
The signal is supplied to a quadrature detection circuit 36 via an STC circuit 35, and is converted into a complex signal (A+iB). The real part of this complex signal is supplied to the delay line 37 and the imaginary part is supplied to the delay line 38 and sampled for each tap, and the sampling outputs Et and Ex are multiplied by the multipliers 39-1 to 39-n s40. −
1-40-n, 41-1-41n; 42 1-42-
are supplied to one input terminal of A/n, respectively, and
The signal is supplied to a D converter 43. Multiplying calculators 39-1 to 39-n; 401 to 40-n, 41-1 to
41-n; The reference wave from the D/A converter 34 is supplied to the other input terminal of 42-1 to 42-n, and the multiplication is performed by the multiplier 3.
The outputs of 9-1 to 39-n are sent to an adder 45, and the multiplication is sent to a multiplier 40.
The outputs of -1 to 40-n are sent to the adder 46, and the multiplication is done by the adder 41-
The outputs of 1 to 41-n are sent to the adder 47, and the multiplication is sent to the adder 42-1.
The outputs of .about.42-n are supplied to the adder 48, respectively. The outputs of adders 45 and 48 are supplied to a subtracter 49, the outputs of adders 46 and 47 are supplied to an adder 50, and the outputs of these subtracters 49 and adder 50 are supplied to a quadrature modulation circuit 51 and processed. , are supplied to the display device 52. Here, the delay line is 37°38, and the multiplication is by calculators 39-1 to 39-n.
, 4θ-1 to 40-n.

41-1 to 41-n, 42-1 to 42-n,
Adders 45-48.degree. 50 and subtracter 49 constitute a correlation circuit.

On the other hand, the output of the A/D converter 43 is supplied to a reference wave calculation circuit 53, and the output of this reference wave calculation circuit 53 is supplied to the 5-RAM 31 provided in the connector 22 of the ultrasound endoscope 21. It has become. Note that the operations of the reference wave calculation circuit 53 and the display device 52 are controlled by a control section 55, and the operation of the RO
Either M30 or 5-RAM31 is selected,
The reference wave data is supplied to the D/A converter 34.

Next, the operation of the ultrasonic endoscope apparatus shown in FIG. 3 will be explained.

In this embodiment, pulse compression is normally performed using initial reference wave data 30a previously stored in the ROM 30, and an ultrasound image is displayed on the display device 52. First, the transmitting circuit 33
The chirp signal is output from the vibrator drive circuit 29 according to the transmission rate signal from the slip ring 2.
8 to drive the ultrasonic transducer 25 into the subject.
Emit an ultrasonic wave pulse as shown in the figure.

The ultrasonic chirped pulse emitted from the ultrasonic transducer 25 is reflected from the subject by the ultrasonic transducer 25, which converts it into an electrical signal and sends it to the ST via the slip ring 28.
The signal is supplied to the C circuit 35, where the attenuation is corrected according to the depth within the subject, and the output thereof is supplied to the quadrature detection circuit 36. The quadrature detection circuit 36 complex-converts the frequency band of the ultrasonic echo signal from the STC circuit 35 to a low frequency band so as to facilitate signal processing, and converts the real part (A) of the complex signal (A+iB) into a delay line. 37 and the imaginary part (B) are respectively supplied to the delay line 38 and sampled for each tap. The output sampled for each tap by the delay line 37 is multiplied by multipliers 39-1 to 39-n and 40.
-1 to 40-n, and the output sampled for each tap by the delay line 38 is multiplied by multipliers 41-1 to 41-n and 42-1 to 42-n.
is supplied to one input terminal of n.

On the other hand, the control unit 55 controls the ROM 30 to generate initial reference wave data 3 stored in advance in the ROM 30.
Make sure to read 0a. This reference wave data 30a is supplied to the D/A converter 34 to obtain a reference wave (C+iD, where C; C+ to Cn, D; dl to d6), and the multiplier 39-1 multiplies the outputs 01 to c7. ~ 39n and the other input terminal of 41-1 ~ 41-n, the output d1
Multiply by ~d7 using calculators 40-1~40-n and 42-1~
42-n, respectively. In this way, each multiplier multiplies the echo signal and the reference wave signal in the time domain, and the adder 45 multiplies the sum (AC) of the multipliers 39-1 to 39-n. The multiplication in the adder 46 is the sum (AD) of the calculators 401 to 40-n.
, the adder 47 multiplies the total sum (BC) of the calculators 41-1 to 41-n, and the adder 48 multiplies the sum (BC) of the calculators 41-1 to 41-n.
~42-n, and calculate the sum (BD) of each of them, and subtracter 49
The difference between the outputs of adders 45 and 48 (AC-BD) is determined by the adder 50, and the sum of the outputs of adders 46 and 47 (AD+B) is determined by the adder 50.
By determining C), the ultrasonic echo signal converted into a complex signal (A+iB) and the reference wave (C1iD) are convolved and integrated to obtain cross-correlation and pulse compression is performed. The echo signal thus compressed by the correlation circuit is supplied to the orthogonal modulation circuit 51, modulated into a frequency band that can be easily processed by the display device 52, and displayed on the display device 52.

Here, if the initial reference wave data 30a stored in advance in the ROM 30 is in a state that cannot be said to be optimal due to changes in the characteristics of the ultrasonic transducer 25 over time, etc., the reference wave data 30a is can be reset. That is, a reflector 60 made of, for example, a stainless steel block with a reflectance l is placed opposite the ultrasonic transducer 25, and an ultrasonic chirped pulse is emitted from the ultrasonic transducer 25 toward the reflector 60 in the same manner as described above. is emitted, and the ultrasonic echo signal is supplied to a correlation circuit via an STC circuit 35 and a quadrature detection circuit 36. Further, the control unit 55 controls the operation of the reference wave calculation circuit 53, and the delay line 37° 38 of the correlation circuit is converted into a digital signal by the A/D converter 43.
A reference wave is calculated based on the outputs (Et, Ex), and the reference wave data is stored in the SRAM 31 backed up by the backup circuit 32 under the control of the control unit 55. Thereafter, in actual observation of ultrasound images, the control unit 55 selects the 5-RAM 31 and uses the 5-RAM
31, the latest reference wave data 31a stored in D/
After passing through the A converter 34, the multiplication is performed by calculators 39-1 to 39-n,
40-1 to 40-n, 41-1 to 41-n, 42-
1 to 42-n to perform pulse compression.

As a result of the above operations, if the initial reference wave stored in the ROM 30 becomes less than optimal due to changes in the characteristics of the ultrasonic transducer 25 over time, etc., the operator can use a reflector with a reflectance of 1. By using 60, the reference wave can be readjusted easily.

FIG. 4 shows the configuration of an ultrasonic diagnostic apparatus in a second embodiment of the present invention. The ultrasonic endoscope 71 is detachably connected to the observation device 72 as in the above embodiment. This ultrasonic endoscope 71 is, for example, a perspective endoscope having an observation optical system 73, an air/water supply tube 74, a forceps channel 75, an illumination optical system (not shown), etc. as shown in FIG. An ultrasonic transducer 77 is rotatably provided at the insertion tip of the probe, protected by a cap 76, and while this ultrasonic transducer 77 is rotated by a motor (not shown), ultrasonic waves are transmitted and received to and from the subject through the camp 76. Configure it to do so.

Note that the camp 76 is filled with an ultrasonic transmission medium 78 such as water in order to prevent ultrasonic waves from attenuating.

Here, the cap 76 is made of plastic, for example, which effectively transmits ultrasonic waves, but in reality, the ultrasonic transducer 7
The ultrasonic waves emitted from the cap 76 are reflected by the cap 76 and reflected by the ultrasonic transducer 77, so multiple echoes are generated between the ultrasonic transducer 77 and the cap 76, and the multiple echoes are converted into ultrasonic vibrations. The wave is received by the receiver 77. Therefore, when the ultrasonic transducer 77 emits ultrasonic waves toward the subject and receives the reflected waves, in addition to the echo signal 1 from the subject, as shown in FIG. A multiple echo signal (2) appears between the sound wave transducer 77 and the sound wave transducer 77.

In this embodiment, as described above, the ultrasonic wave emitted from the ultrasonic transducer 77 is reflected by the cap 76, and as described later, one of the multiple echo signals is extracted and a reference signal is generated. Calculate the data.

In FIG. 4, an ultrasonic transducer 77 is driven by a chirp signal sent from a transmission circuit 82 in synchronization with a transmission timing signal from a control circuit 81 provided in an observation device 72, and is thereby driven by a chirp signal sent toward the subject. Ultrasonic chirped pulses as shown in Figure 2 are emitted. Transmission circuit 82
A voltage control circuit 83 controlled by a voltage control signal from the control circuit 81 is connected to the , and voltage control from the control circuit 81 is performed by manually operating a switch on an operation panel (not shown) provided on the observation device 72. The ultrasonic transducer 77 is transmitted from the transmitting circuit 82 via the voltage control circuit 83 according to the signal.
It is possible to control the transmission power of the chirp signal sent to the chirp signal.

On the other hand, the echo signal received by the ultrasonic transducer 77 is amplified by a preamplifier 84 and then processed by a signal processing circuit 85 provided in the observation device 72 to be processed by a correlation circuit 86 and a gate circuit 8.
7. In the reference wave data calculation mode, the gate circuit 87 is supplied with a gate pulse as shown in FIG.
A predetermined echo signal as shown in FIG. 6C is extracted from the multiplex echo signal shown in FIG. 6A and supplied to the reference wave calculation circuit 88.

The reference wave calculation circuit 88 calculates reference wave data based on the echo signal extracted by the gate circuit 87, supplies this reference wave data to the correlation circuit 86, and outputs the reference wave data to the correlation circuit 86 in the ultrasonic image display mode. The echo signal from the signal processing circuit 85 and the reference wave data are cross-correlated to pulse-compress the echo signal. Note that the reference wave data calculated by the reference wave calculation circuit 88 is
8 or the correlation circuit 86 to store it in the RAM. The output of the correlation circuit 86 is supplied to a signal processing circuit 89, where it is modulated into a frequency band that can be easily processed by a display device 90, and then displayed as an ultrasonic image on a display device 90 under the control of a control device 81. do.

The operation of this embodiment will be explained below.

In this embodiment, in order to obtain reference wave data based on the echo signal from the cap 76 that protects the ultrasonic transducer 77, the reference wave data is calculated in the calculation mode prior to the ultrasonic image display mode. In this calculation mode, the voltage from the control circuit 81 is adjusted by manually operating the switch on the operation panel so that the amplitude of the multiplex echo signal from the cap 76 is large enough to prevent saturation in the preamplifier 84 and signal processing circuit 85. The control signal controls the transmission power of the chirp signal sent from the transmission circuit 82 via the voltage control circuit 83, thereby driving the ultrasonic transducer 77 to emit ultrasonic waves, and transmitting the echo signal to the preamplifier 8.
4 and a signal processing circuit 85 to a gate circuit 87 to extract a predetermined echo signal at the cap 76 as shown in FIGS. 6A to 6C, and a reference wave calculation circuit 88 calculates reference wave data. This is stored in the RAM of the reference wave calculation circuit 88 or the correlation circuit 86.

After calculating the reference wave data, when displaying the ultrasound image of the subject, operate the switch on the operation panel to switch to display mode, which will generate a chirp signal with a power that allows you to obtain an echo signal of sufficient amplitude from the subject. The ultrasonic vibrator 77 is driven to emit an ultrasonic chirp pulse to the subject, and the echo signal is supplied to the correlation circuit 86 via the preamplifier 84 and signal processing circuit 85 to be calculated in the calculation mode described above. The pulse is compressed by performing cross-correlation with the reference wave data obtained by
9 to a display device 90 to display it as an ultrasound image.

In addition, the previously calculated reference wave data is
If the condition is not optimal due to changes in the characteristics over time, etc., manually operate the switch on the operation panel to enter the calculation mode described above, and the reference wave data is calculated based on the echo signal from the cap 76. Calibrate.

As described above, according to this embodiment, since the cap 76 that protects the ultrasonic transducer 77 that the ultrasonic endoscope 71 is originally provided with is used as the target for calibrating the reference wave data, A special jig is not required, so the reference wave can be easily calibrated.

Note that this invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, this invention is not limited to the above-mentioned internal ultrasound endoscope,
It can also be effectively applied to external ultrasound diagnostic equipment. In addition, in the first embodiment, the initial reference wave data is stored in the ROM.
However, this ROM 30 is omitted and the reference wave data is obtained by calculation as described above and is stored in the 5-
It may be stored in the RAM 31 and used. Furthermore,
In the second embodiment, the transmission power of the chirp signal sent out from the transmission circuit 82 is controlled so that the amplitude of multiple echoes suitable for calculating reference wave data is obtained, but the transmission power is fixed. The timing of the gate pulse may be controlled to capture multiple echoes that have been sufficiently attenuated to an amplitude suitable for calculating reference wave data.

〔Effect of the invention〕

As described above, according to the present invention, the reference wave calculation means is provided to calculate the reference wave based on the received ultrasonic echo signal from a predetermined reflecting object, making it easy to adjust the reference wave. Therefore, the ultrasonic echo signal can be pulse-compressed with the optimal reference wave at all times in response to changes in the characteristics of the ultrasonic transducer and circuit elements over time. Furthermore, if the reference wave calculated by the reference wave calculation means is stored in the memory of the ultrasound endoscope as in the first embodiment, variations in the characteristics of the ultrasound transducer for each ultrasound endoscope can be avoided. It can also correspond to

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention, Fig. 2 is a diagram showing an example of an ultrasonic chirp signal, and Fig. 3 is a block diagram showing a specific configuration of the first embodiment. , FIG. 4 is a block diagram showing the configuration of an ultrasound diagnostic apparatus in a second embodiment of the present invention, FIG. 5 is a diagram showing the configuration of an example of an ultrasound endoscope, and FIG. 6A
-C is a signal waveform diagram for explaining the operation of the second embodiment. ■...Ultrasonic transducer 2...Transmission/reception circuit 3...
- Quadrature detection circuit 4... Matched filter 5... Quadrature modulation circuit 6... Display device 7... Correlation circuit
8... Reference wave setting section 9... Control section
21...Ultrasonic endoscope 23...Observation device
25... Ultrasonic transducer 29... Vibrator drive circuit 30... ROM31... 5-RAM
33... Transmission circuit 34... D/A converter 3
5... STC circuit 36... Quadrature detection circuit 37
．． 38...Delay line 39-1 to 39-n, 4
0-1 to 40-n, 41-1 to 41-n, 42-1
~42-n...Multiplication unit 43...A/D converter 49...Subtractor 52...Display device 55...Control unit 71...Ultrasonic endoscope 76... - Cap 81...Control circuit 83...Voltage control circuit 85, 89...Signal processing circuit 45 to 48.50...Adder 51...Orthogonal modulation circuit 53...Reference wave calculation circuit 60 ... Reflector 72 ... Observation device 77 ... Ultrasonic transducer 82 ... Transmission circuit 84 ... Preamplifier 86 ... Correlation circuit 87 ... Gate circuit 90 ... Display device 88.・Reference wave calculation circuit

Claims (1)

[Claims] 1. An ultrasonic diagnostic pulse compression device that pulse-compresses an echo signal of an ultrasonic chirp wave whose frequency changes, and means for calculating a reference wave for pulse compression based on an echo signal from a predetermined reflecting object. A pulse compression device for ultrasonic diagnosis, comprising: a correlation means for cross-correlating the reference wave calculated by the reference wave calculation means with an echo signal from a subject and compressing the echo signal into a pulse.