JPS6311015B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention emits ultrasonic waves into a test object such as a human body, and detects the damage caused by emitting ultrasonic waves from inside the test object based on the intensity, traveling direction, generation time, etc. of the reflected waves from inside the test object. An electronic scanning ultrasonic tomography system (hereinafter referred to as "electronic scanning ultrasonic tomography system") that obtains tomographic image information regarding the internal structure and composition of the specimen in real time.
(abbreviated as ESNDT device).

Prior Art Currently, there are roughly two types of ESNDT devices. One is a sector-scanning ESNDT device (hereinafter abbreviated as sector device) based on the principle of a phase-synthesizing antenna. This system generates ultrasonic waves in a predetermined direction by controlling the phase of the ultrasonic waves generated by multiple ultrasonic generating elements, such as piezoelectric vibrators.By changing this phase control amount, ultrasonic waves The bundle is deflected and scanned in a fan shape. This sector device is capable of scanning a wide fan-shaped area even though the size of the ultrasound transmission/reception wave surface is small, so it is mainly used in cases where ultrasound must be emitted from between the ribs, such as when observing the heart. .

The other is a linear device. In this method, a large number of piezoelectric vibrators arranged in a straight line are electronically switched and driven one after another, and an ultrasonic beam is emitted in a direction perpendicular to the array plane of the piezoelectric vibrators and scanned in parallel.

Problems to be Solved by the Invention Since the linear device can scan an ultrasonic beam more easily than the sector device, it can be realized at low cost and with relatively high resolution. However, in order to obtain a wide test area, it is necessary to increase the length of the probe, which means that the probe must be brought into close contact over a wide range of surfaces with curvatures or irregularities. This becomes difficult.

Figure 6a shows this pattern, where probe 1
00 can be brought into close contact with the living body surface 101, for example, since the only effective test area is the shaded area in the figure. Furthermore, if a bone or an organ with a large air content is present in the test region, the organ on the back side (in the depth direction) of the organ cannot be observed with respect to the sound wave propagation direction.

Although this drawback can sometimes be eliminated by moving the probe, this is often not possible due to anatomical constraints. One way to avoid the above drawback is to use a probe 100 as shown in FIG. 6b.
By making the beam incident at an angle, it is possible to observe the object 103 blocked by the bone 102, but in this case, only the shaded area in figure b can be observed. A sector device was developed to eliminate these drawbacks.

The size of the probe 104 of the sector device is 2 to 3 cm.
This alleviates drawbacks such as unobservability due to the surface or internal structure of the living body or narrowing of the test area. However, in principle, the detection range near the biological surface becomes narrow, as shown in Figure 6c, and there are problems with the phase delay element required to deflect the ultrasound beam over a wide angle with good directionality. However, there are disadvantages such as the equipment is complicated and expensive.

On the other hand, a problem common to both devices is that
Ultrasonic probe for ESNDT (hereinafter referred to as the probe section)
There were major problems, especially in the probe section for linear equipment. The probe section for linear equipment uses a tanzaku-shaped piezoelectric vibrator at a length of about 50 to 200 mm.
Approximately 50 to 200 piezoelectric vibrators must be arranged, and if the ultrasonic frequency is several hundred K to several MHz, the width w to thickness t (w/t) of one piezoelectric vibrator will be less than 3. When using a conventional single resonator (w/t≧
10) It is possible that the probe section operates differently. For example, this different operation means that the vibration surface of the piezoelectric vibrator does not perform a simple piston movement, but performs a complex vibration in which higher-order vibration modes are superimposed.
Alternatively, it means that various data displayed in the data table, such as coupling coefficients, become different. If the piezoelectric vibrator does not perform a simple piston motion, the sound field of the ultrasonic waves transmitted and received from the piezoelectric vibrator will not be in the shape of the Fourier transform of the aperture shape, but will be abnormal. Figure 7 shows that w/t is
The sound field pattern of the probe section is a collection of two elements using 2.5 PCM-5 piezoelectric ceramics.The solid line is the theoretical value from the piston sound source, and the circle mark is the experimental value obtained with this element. If we calculate backwards from Figure 7, the PCM-
5 The velocity distribution on the surface of the ceramic element is the 8th
As shown in the figure, it can be seen that it is distorted, proving that there is no piston movement. It is thought that these occur as a result of the combination of various vibrational modes.

As mentioned above, unless special consideration is given to the w/t ratio, the transducer surface will not perform a simple piston movement, resulting in disturbances in the sound field pattern and theoretically determining the level and shape of the side ropes. Make it abnormally larger and have a different shape than the normal one. As a result, the accuracy of the detected information is significantly reduced, and the image quality (resolution, gradation, etc.) of the tomographic image is deteriorated.
deteriorate. Furthermore, various signal processing methods are available to improve resolution, operability, and functionality, such as weighted drive to keep sidelobe levels low, ultrasonic beam focusing and manipulation functions to improve resolution. When deflecting an ultrasonic beam for expansion, etc., it is impossible to accomplish this unless the transducer is performing ideal piston motion. Therefore, it can be said that it is virtually impossible to obtain high-quality diagnostic information or expand the functionality with ESNDT devices that use a probe section based on the conventional concept.

The present invention solves the above-mentioned drawbacks of the conventional probe section, and maintains the advantage of the linear device, which is that the device configuration is simple and good tomographic images can be obtained over a wide test range. The purpose of the present invention is to provide an ESNDT device that alleviates the narrowing of the test range due to biological structural limitations, which is an advantage of the sector device.

Means for Solving the Problems The present invention achieves the above object, and its technical means include a probe section that performs ideal piston vibration, and an ultrasonic beam that is deflected in a predetermined direction for transmission and reception. The device is equipped with a deflection transmitting/receiving signal processing section for scanning, a selection drive control section for scanning an ultrasonic beam at a predetermined pitch, a tomographic image display section, and a reference signal generation section for controlling the overall operation.

Effects In such a configuration, the present invention performs linear scanning while deflecting the sound wave in an arbitrary or preset angular direction within a plane defined by the traveling direction of the sound wave and the arrangement direction of the transducers. By doing this, if the defects that cannot be detected due to the object surface or internal structure of the object to be tested are resolved, and there are no obstacles mentioned above, the test range defined by the length of the probe is expanded and the equivalent In addition to expanding the field of view,
So-called composite scanning, such as linear scanning while performing sector scanning, becomes possible.

Example Examples of the present invention will be described below.

First, we will discuss a specific example of the configuration of the probe section for the CESNDT device used this time. FIG. 1 shows an example of the configuration of this probe section.

FIG. 1a is a sectional view, and FIG. 1b is a plan view.

In FIG. 1a, 401 is a piezoelectric vibrator that uses two- or three-component ceramics such as PZT and PCM, one-component ceramics such as LTT, or crystalline materials such as quartz and LiNbO ₃ . 402 and 403 are metal electrodes made of Ag,
It is made by vapor deposition or baking coating of Al, Au, Cu, In, etc. 404 and 405 are a matching layer and a back load, respectively. The back load 405 may or may not be used.

The matching layer 404 may be a single layer or a multilayer such as a double layer or a triple layer. 406 is an acoustic insulation space for eliminating acoustic coupling between each piezoelectric vibrator. Figure 1b is Figure 1a
FIG. For simplicity, the back load is omitted. Since the electrode 402 on the matching layer 404 side is used as a common electrode, an inter-electrode connection line 407 is provided thereon. 408 is a lead wire for a common electrode, and 409 is a lead wire from each piezoelectric vibrator.

The dimensions of each part are the generated ultrasonic frequency, w/t ratio,
It is set in consideration of insertion gain, differential phase characteristics, test range, etc. (The basic concept for setting and basic calculation materials are published by the same applicant in October 1975.
(Refer to Japanese Patent Publication No. 56-17026, filed on the 25th) As an example, in the case of a generated ultrasonic frequency of 2.5MHz,
Specific dimensions and materials are shown below. In the case of this embodiment, two piezoelectric vibrators are electrically connected in parallel to form one unit vibrator.

Piezoelectric vibrator Material PCM-5 〃 Dimensions (w) 0.4 x (t) 0.6 mm 〃 Number of pieces 128 Unit oscillators Number of pieces 64 Acoustic insulation layer Material Air 〃 Dimensions Width 0.1 mm Matching layer Material 1st layer fused silica glass 2nd Layer epoxy resin back load Not used Figure 2 shows the sound field pattern when the probe section manufactured according to the above specifications is vibrated across the width, and 16 piezoelectric vibrators (8 unit vibrators) are simultaneously vibrated. Shows when it works. In the figure, the vertical axis shows the normalized echo signal, and the horizontal axis shows the angle. The solid line is the theoretical value when the sound source is in piston motion, and the circle is the experimental value. From FIG. 2, it can be seen that this probe section is vibrating in an ideal manner.

Before entering into a detailed explanation of the device, we will explain the basic principle for performing ultrasonic beam deflection. FIG. 3 is an explanatory diagram thereof. Using n unit transducers 500 (hereinafter referred to as transducers) arranged on a straight line at a distance d, the ultrasonic beam is deflected by Θ from the normal direction of the plane on which the transducers are arranged. If you want to make each oscillator (i-1)d sin Θ/
If driven with a time difference of v (i: transducer number, d: transducer interval, Θ: deflection angle, v: sound wave propagation velocity), the composite wavefront 501 of the ultrasonic waves generated by each transducer will be , from Huygens' principle,
This occurs in a direction shifted by Θ from the vibrator array surface 502. For example, if you want to deflect an ultrasound beam by Θ = 30°, assuming that the number of transducers n = 8, the transducer spacing 1 mm, and the underwater propagation velocity v = 1.5 × 10 mm/sec, the time required to drive the first transducer is If it is 0 seconds, the oscillator with the 8th oscillator number only needs to be driven with a delay of 2.33 μsec. The driving timing of the vibrator number 7 and 6 is 2.0 μ sec and 1.67 μ sec, respectively.
sec.

Based on the above explanation as a basic principle, a specific example of a CESNDT device according to an embodiment of the present invention will be described. FIG. 4 shows a block diagram of a specific example of the device, and FIG. 5 shows a signal waveform diagram of each part.

This CESNDT device can be roughly classified by function.
As shown in the figure, the UP controls the transmission and reception of ultrasonic waves.
section 200, a selection drive control section 201 that controls a large number of piezoelectric vibrators constituting the UP section so that they can be selectively driven in a predetermined order, and a deflection transmission/reception signal processing section that deflects ultrasonic waves and processes transmission/reception signals. 20
2, a display section 203 that displays tomographic images, and a reference signal generation section 204 that controls the overall operation of each section. UP section 200 and selection drive control section 201
are loaded in the same probe housing, and the other three parts are loaded in the main body housing.

The probe section 200 is composed of a unit vibrator 300 having the configuration shown in FIG. However, in this case, the unit frequency is 64 unit oscillators (number of oscillators = 64 ×
2 = 128 sheets). It is assumed that the ultrasonic beam deflection is performed using eight unit transducers. There are eight drive signal generation circuits 301 that generate impulses or RF pulses in order to drive eight unit oscillators with predetermined time delays. This drive signal generation circuit 301 generates a drive signal in synchronization with a drive timing signal 302 from the outside. The drive time delay amount for ultrasonic beam deflection is determined by the drive timing signal 30.
It is controlled by the application timing of step 2. This drive timing signal is supplied to the reference clock signal generator 30.
The drive timing controller 305 generates the clock signal using the reference clock signal 304 (FIG. 5a) of No. 3 as a reference. This drive timing control section 305 is an 8-bit shift register (in this case, TI's SN74164 is used) that operates in synchronization with the reference clock signal.
It generates eight drive timing signals with time differences corresponding to the beam deflection angle. The shift register performs the transfer based on the delay timing signal 307 (FIG. 5b) generated from the deflection angle designation signal generator 306. When the unit transducer spacing d=1 mm, the deflection angle Θ=30 degrees, and the propagation speed v=1.5 Km/S, the frequency of this delay timing signal is 3 MHz. The delayed timing signal, depending on the predetermined deflection angle,
For example, by changing the oscillation frequency of the CR oscillator, a delay timing time corresponding to an arbitrary deflection angle can be obtained. In addition, since the delay timing signal is deflected by 8 unit elements in this case, 8 unit elements are used for each pulse of the reference clock signal.
Generate only one.

The drive timing signal 302 generated by the drive timing control section 305 in response to this delayed timing signal controls the eight drive circuits 3 having the same configuration.
The drive signal 308 generated at 01 is input to each of the eight 8-channel multiplexers (MPX) 309 mounted inside the probe housing.
Applied to the OUTPUT terminal. In this case, this
MPX309 uses Siliconix DG508. This drive signal is
A predetermined vibrator is driven through a channel selected by a 3-bit MPX address counter 310 installed corresponding to MPX. An output 313 of an 8-bit shift register 312 that operates in synchronization with a reference clock signal 304 is connected to a clock terminal 311 of this address counter. As a result, each time one reference clock signal 304 is sent, the 8-bit shift register shifts by one bit, and the MPX address counter 310 whose bit has changed is incremented by one address. In addition,
The frequency of the reference clock signal is set taking into account the predetermined depth of inspection and the time required to compose one screen, and in this case, for example, it is approximately 3 to 4 KHz to obtain a depth of inspection of approximately 20 cm. .

How to connect each channel of MPX to the probe section is as follows.
As shown in Figure 4, P1 is the first channel of No.1MPX (hereinafter abbreviated as 1ch), and P2 is the first channel of No.2MPX.
1ch, P3 to 1ch of No.3MPX...P8 to No.
8MPX 1ch, P9 to No.1MPX 2ch, P1
0 to 2ch of No.2MPX...P63 to No.7MPX
8ch, and P64 is connected to No.8MPX's 8ch. As a result, one of the eight channels of each MPX is always on, and one group (eight units) of unit oscillators adjacent to each other can transmit and receive waves, and the output of the 8-bit shift register 312 Each time it changes, the combination of unit oscillators in this group changes, that is, it can be scanned.

Through the circuit operation described above, the ultrasonic beam 314 generated in the direction of the predetermined deflection angle Θ is reflected by different structures inside the body, and the reflected sound wave excites the transducer group that controls the wave transmission. , and guides the resulting reflected electrical signal 315 to a received signal selector 316 consisting of one MPX of eight channels. Here, for example, only the channel controlling the left end of the emitted sound wave is selected and applied to the receiver 317. The channel control of this received signal selector is performed using the reference clock signal 304.
A 3-bit counter 31 whose clock input signal is
This is done using the channel selection signal 319 generated at 8.

In this example, we adopted a method in which only one channel is used as a received signal, but it is also possible to use an analog or digital memory to add the same amount of delay to each received signal as when transmitting. be.

The receiver 317 performs detection and amplification on the received signal 320 and applies it to the brightness modulation section of the tomographic image display device 321 .

On the other hand, the high-speed deflection of this display device 321 is achieved by the sawtooth deflection signal 32 in synchronization with the reference clock signal.
3 (Fig. 5d)
22. Also, for low-speed deflection, a frequency divider 3 divides the reference clock signal by the number of scanning lines.
This is done by a slow deflection signal 327 (FIG. 5e) generated by a deflection signal generator 326 in synchronization with a slow clock signal 325 whose frequency is divided by 24.

With the above device operation, a so-called diamond-shaped tomographic image can be obtained by scanning in the same manner as linear scanning while deflecting the ultrasound beam by 30 degrees.

The above explanation has been based on an example in which the ultrasonic beam is scanned while driving eight unit transducers as a group and shifting them by the width of one unit transducer. The number of oscillators is not limited to 8, but may be 7 or 9 to 10, and generally this number can be any integer multiple of the unit oscillator. Furthermore, the amount of lateral shift pitch is not limited to one unit transducer width; for example, if the transducer is driven with a shift of more than the width of a group of drive transducers, the clock frequency exceeds the limit clock frequency of the pulse reflection method due to propagation time limitations. It is also possible to emit sound wave pulses to speed up the completion time. Scanning can be performed in both forward and reverse directions by using the counter 310 as an addition/subtraction counter.

Effects of the Invention In summary, the present invention includes a probe section that performs ideal piston vibration, a deflection transmitting/receiving signal processing section that deflects an ultrasound beam in a predetermined direction and transmits and receives it, and scans the ultrasound beam at a predetermined pitch. The present invention is equipped with a selection drive control section for controlling the operation, a tomographic image display section, and a reference signal generation section for controlling the overall operation, and has the following effects.

(1) It is possible to obtain tomographic images of a wide examination area while avoiding obstacles for diagnosis.

(2) As a result of (1), diagnosis becomes possible regardless of biological structure, improving diagnostic accuracy and efficiency.

(3) When linear electronic scanning (when there is no time delay of the drive clock signal used in the present invention) and the scanning mode of the present invention are used together, a wider field of view can be achieved than in the case of linear electronic scanning.

(4) By changing the polarity of the deflection angle each time one tomographic image is completed, a trapezoidal tomographic image can be obtained and a wider field of view can be achieved compared to linear electronic scanning.

(5) Since the deflection angle can be set arbitrarily, for example, it is possible to obtain a tomographic image by overlapping sector-shaped tomographic images obtained while scanning a sector, which allows for the observation of internal organs. This solves the problem of incomplete imaging of organ morphology (specular effect), which occurs because the incident angle of the ultrasound beam is fixed. This effect is due to (3) above,
It is also obtained in (4).

(6) The probe section is configured to perform ideal piston motion and to achieve high sensitivity.
The deflection of the ultrasonic beam according to items 1 to 5 above can be performed ideally and with high sensitivity, and a high-quality tomographic image can be obtained.

(7) By mounting the selection drive control section and the probe section in the same housing, the number of connection lines with the main body section can be significantly reduced, improving the operability of the probe.

[Brief explanation of the drawing]

FIG. 1 shows a probe section of an electronic scanning ultrasonic tomographic examination apparatus according to an embodiment of the present invention, where a is a sectional view, b is a plan view, and FIG. 2 is a probe of the present invention. Figure 3 is a diagram of the basic principle of ultrasonic beam deflection of the present invention; Figure 4 is a block diagram of the apparatus of the present invention; Figures 5a to 5e are waveform diagrams of each part in Figure 4. , Fig. 6 a and b are diagrams showing an example of a tomographic image of a conventional linear device, c is a diagram showing an example of a tomographic image of a conventional sector device, and Fig. 7 is a sound field pattern diagram when w/t is 2.5. , FIG. 8 is a plan view of the vibrator when w/t is 2.5. 200... Probe section, 201... Selection drive control section, 202... Deflection transmission/reception signal processing section, 203...
...Display section, 204...Reference signal generation section, P1 to P
64... Probe section, 301... Drive signal generation circuit, 303... Reference clock signal generator, 309
... Analog multiplexer, 310 ... Counter, 312 ... 8-bit shift register, 305
... Drive timing control section, 306 ... Deflection angle designation signal generator, 317 ... Receiver, 321 ...
Tomographic image display device.

Claims (1)

[Claims] 1. N pieces (N is plural) of piezoelectric vibrators having a ratio w/t of width w to thickness t of 0.8 or less are arranged, and electrodes are placed on the upper and lower surfaces of the piezoelectric vibrators in the thickness direction. The probe part has a matching layer closely attached to one surface of the electrode, and the probe part is excited by width stretching vibration with an electromechanical coupling coefficient k33, and the direction of the ultrasonic wave is ,
a deflection transmission/reception signal processing unit that generates a drive signal for deflecting the ultrasound beam in a predetermined direction within a plane defined by the arrangement direction of the piezoelectric vibrators, and performs reception signal processing of the reception electric signal; Of the N piezoelectric vibrators that make up the probe section, n piezoelectric vibrators (N>n) are grouped together, and the ultrasonic beam is directed to a predetermined level while driving the n piezoelectric vibrators at the same drive signal level. a selection drive control section loaded in the same housing as the probe section, the selection drive control section configured to perform scanning in a predetermined direction while shifting the piezoelectric vibrator spacing or an integer multiple of the spacing; The present invention is characterized by comprising a display section that displays a tomographic image of the received signal obtained by the deflection transmission/reception signal processing section according to the scanning order, and a reference signal generation section that controls the overall operation of each of the above sections. Electronic scanning ultrasonic tomography device. 2. The electronic device according to claim 1, wherein the selection drive control section includes one or more analog multiplexers and a counter that controls opening and closing of the analog multiplexers based on a reference signal. Scanning ultrasonic tomography device.