JP2000350294A - Ultrasonic probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic probe which has a wide directional angle and is easy to manufacture. SOLUTION: An ultrasonic transducer 2 is constituted by providing a wave transmitting and receiving element 10 which has plural circular electrodes 13 and 14 formed on the top and reverse surfaces of a piezoelectric ceramic element plate in the circumferential direction opposite each other, performing polarization between a couple of opposite circular electrodes 13 and 14, and forming a piezoelectric vibration part between the electrodes, arranging a sound matching layer 3 on the wave transmission and reception surface of the wave transmitting and receiving element 10, and the ultrasonic wave transducer 2 is fitted into the tip part of a metallic probe thin pipe 5; and lead wires led out of each of the electrodes are connected to a connection cable 21 penetrating a metallic main pipe 7, whose tip is joined with the rear end of the metallic probe cylinder 5 to lead the connection cable 21 out of the metallic main pipe 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe used for medical and industrial ultrasonic endoscopes.

[0002]

2. Description of the Related Art Ultrasound diagnostics, and in particular, ultrasound image information, have become indispensable examination methods in all fields of clinical medicine today. For example, in blood vessels, arteriosclerosis caused by blood clots due to cholesterol accumulation is a serious disease, but in order to diagnose abnormalities inside such blood vessels, it is better to observe them directly from the inside instead of from the outside. Can be expected to be high and effective. In this case, it is impossible to obtain an image by optical means since the blood vessel is filled with blood. Under such circumstances, ultrasound imaging is an effective visualization method. For this reason, a diagnostic method of inserting an ultrasonic probe into a blood vessel and imaging the blood vessel has been performed.

However, most of the conventional methods transmit an ultrasonic beam in a radial direction of a blood vessel to obtain a two-dimensional image (for example, US Pat. No. 4,917,097).
No. 5,603,327;
00 etc.). However, from a medical point of view, it is preferable to obtain a three-dimensional image in real time. On the other hand, JP-A-10-
Japanese Patent Laid-Open No. 82852/1996 discloses an array structure of piezoelectric elements for forming a three-dimensional image using an ultrasonic probe.
No. 852. By the way, this method is a method of arranging the conversion elements on a plurality of concentric circular grids, and arranging the piezoelectric elements on the grid,
In order to position the ultrasonic wave transmitting / receiving surfaces of a plurality of piezoelectric elements on the same plane, high accuracy is required in the thickness accuracy of the grid.

Therefore, for example, a plurality of piezoelectric elements are arranged along the circumferential direction at the tip of the probe, a spherical wave is transmitted forward from one of the piezoelectric elements, and received by all the remaining elements. A method has been proposed in which a three-dimensional image is obtained by sequentially converting elements for transmitting waves.

In order to obtain a three-dimensional image by this method, a probe capable of transmitting a spherical wave in a forward direction is used. At the tip of the probe, a plurality of fine elements made of a material having piezoelectricity for transmitting and receiving ultrasonic waves are arranged.

[0006] As a material for this element, a piezoelectric polymer such as PVDF (polyvinylidene fluoride), which can be easily microfabricated, has been put to practical use. However, in terms of sensitivity and the like, it is preferable to use ceramics having a higher electromechanical coupling coefficient as the element. Therefore, a piezoelectric ceramic such as PT (lead titanate) or PZT (lead zirconate titanate) is used as a material, electrodes are formed on the front and back surfaces of the piezoelectric ceramic processed into a ring shape, and the electrodes are formed by a dicing saw. There has been proposed an ultrasonic probe used for an ultrasonic endoscope or the like, which is divided into individual pieces and arranged in the circumferential direction.

[0007]

By the way, as described above, when elements are manufactured by dividing ring-shaped ceramics, as shown in FIG. 10, each element x is formed as a part of a sector. Since the shape is complicated, the directivity angle θ is small, a spherical wave cannot be obtained, and the range A to be visualized is far and narrow. Further, since the shape of each element is complicated, the vibration mode becomes complicated, and signal processing becomes difficult. In this case, each piezoelectric element may have a circular shape.However, since the magnitude of the directivity angle in the near field is inversely proportional to the diameter of the sound source, a very fine element must be manufactured to increase the directivity angle. Must. However, ceramics generally have problems such as difficulty in fine processing and, when the size is reduced, handling becomes poor.

On the other hand, the ultrasonic probe must be inserted into a blood vessel, and the diameter of the ultrasonic probe must be minimized. Electrical connection between the electrodes to be connected and the external instrument must be ensured, and a major problem remains to be solved in an assembly structure that enables the required electrical connection.

An object of the present invention is to provide an ultrasonic probe which can solve the problems of the conventional configuration.

[0010]

According to the present invention, a plurality of circular electrodes are formed in the circumferential direction on the front and back surfaces of a piezoelectric ceramic element plate, the circular electrodes are opposed on the front and back surfaces, and a pair of circular electrodes facing each other. A transmitting / receiving element that polarizes between the electrodes and serves as a piezoelectric vibrating portion between the circular electrodes; an acoustic matching layer is disposed on a transmitting / receiving surface of the transmitting / receiving element; A transducer is constructed, the ultrasonic transducer is fitted inside the distal end of a metal probe tube, and a lead wire drawn from each circular electrode is connected to a connection cable inserted through a metal main tube, and An ultrasonic probe characterized in that a front end of a main pipe is joined to a rear end of a metal search tube, and the connection cable is drawn out of the metal main pipe. In such a configuration, the transmitting / receiving element is provided with a plurality of piezoelectric vibrating portions along the circumferential direction.

In this configuration, only the piezoelectric vibrating portion of the piezoelectric ceramic element plate has piezoelectricity. And since this piezoelectric vibrating part is arranged along the circumferential direction,
A spherical wave is transmitted forward from one of the piezoelectric vibrating parts,
A three-dimensional image can be obtained by receiving the waves by all the remaining piezoelectric vibrating sections and sequentially converting the transmitting piezoelectric vibrating sections. Therefore, for example, when used for intravascular diagnosis,
3D images of blood vessels can be obtained in real time,
Conventionally, a three-dimensional image that has been assembled in the head by a doctor based on a two-dimensional image can be visualized, and the accuracy of the ultrasonic diagnostic method can be improved.

In such a configuration, a wave transmitting / receiving element can be manufactured only by forming circular electrodes on the front and back surfaces of the piezoelectric ceramic element plate and performing a polarization process between the circular electrodes. There is no need to form a plurality of independent unit transmitting / receiving sections on the same plane.

Further, the directivity angle is inversely proportional to the area of the transmitting and receiving surface, so that it is necessary to reduce the diameter of the transmitting and receiving surface in order to realize a wide directivity angle. Since it is only necessary to form a circular electrode serving as a wavefront on the front and back sides and polarize it, a small-diameter piezoelectric vibrating part can be easily formed without complicated mechanical processing of the piezoelectric ceramic element, and a wide directivity angle characteristic is obtained. Can be provided.

Further, in the above-described configuration, the ultrasonic transducer is carried by the metal probe thin tube inserted into the blood vessel, and the cable connected to the external instrument is inserted through the large-diameter metal main tube. Since each cable is connected in the main metal pipe, the inner diameter of the metal detection thin pipe may be any diameter as long as the piezoelectric ceramic element plate can be fitted. It can be. That is, it is possible to make the distal end into an extremely small diameter that can be inserted into a blood vessel while securing electrical connection.

[0015]

FIG. 1 shows an ultrasonic probe 1 according to one embodiment of the present invention. This ultrasonic probe 1
Forming an acoustic matching layer 3 on the transmitting / receiving surface side of the transmitting / receiving element 10;
The damper layer 4 is bonded to the back side to make the piezoelectric transducer 2
Is composed. The piezoelectric transducer 2 is tightly fitted in a thin metal probe tube 5, and a mounting flange 6 of the small probe tube 5 is fixed to an end of a large-diameter metal main tube 7 to be integrated with the tube case 8. Is configured. A collective cable 20 is inserted into the metallic main pipe 7 and held by a resin tube 22 at a rear end of the metallic main pipe 7. As will be described later, a coaxial connection cable in the collective cable 20 is formed in the metallic main pipe 7. 21 is connected to lead wires 17 and 18 drawn out from each electrode of the wave transmitting / receiving element 10.

Here, the acoustic matching layer 3 is made of epoxy resin or the like, and is formed of a material that matches the acoustic impedance of blood so that sound waves travel straight. Also, the damper layer 4
Is to restrict the sound wave from radiating to the back side of the wave transmitting and receiving element 10, a ceramic material, a resin material,
Aggregate and metal powder are mixed, and the incident sound waves are converted into heat energy and eliminated. For example, an epoxy resin mixed with tungsten powder is proposed.

Next, the configuration of the transmitting / receiving element 10 will be described.
As shown in FIGS. 2 to 4, the wave transmitting and receiving element 10 is based on a piezoelectric ceramic element 11 made of a ferroelectric material having a diameter of 3 mm and a thickness of 0.4 mm containing lead zirconate titanate as a main component. , For example, a diameter of 0.6 mm
A plurality of circular electrodes 13 and 14 having the same diameter are formed in the circumferential direction, respectively, and the circular electrodes 13 and 14 are opposed to each other on the front and back surfaces. It becomes the piezoelectric vibrating part 12. Thereby, the circular electrode 1
Only the region between 3 and 14 has piezoelectricity, and circular electrodes 13 and
When a voltage is applied to the ultrasonic wave 14, ultrasonic waves are sequentially transmitted from the respective piezoelectric vibrators 12, and the reflected waves generate output signals from the respective piezoelectric vibrators 12. Here, the circular electrode 13 is used as a ground electrode, and the circular electrode 14 is used as an input / output electrode.

Next, means for forming the wave transmitting / receiving element 10 having a plurality of piezoelectric vibrating portions 12 in the circumferential direction will be described. First, using a screen printing mask, a silver paste is printed on the surface of the piezoelectric ceramic element plate 11 containing lead zirconate titanate as a main component, and then heat treatment is performed. Then, eight pairs of circular electrodes 13 and 14 are fixed. At this time, the earth circular electrode 1
The reference numeral 3 extends the connection end 13a over the side edge as shown in FIG. Electrode patterns corresponding to the circular electrodes 13 and 14 were previously formed on the front and back surfaces of the large plate-like raw ceramic element plate by screen printing, and a large number of piezoelectric ceramic element plates 11 were cut out from this element plate. The transmitting and receiving element 10 may be mass-produced by firing later.

Thereafter, the circular electrodes 13 and 14 are sandwiched between metal plates, and a polarization process is performed by applying a high DC voltage in silicon oil, so that only the regions where the circular electrodes 13 and 14 are formed have a piezoelectric effect. To the piezoelectric vibrating part 1
Let it be 2.

Next, a ground side lead wire 17 is connected to the connection end 13a of the ground circular electrode 13 at the periphery of the wave transmitting / receiving element 10 by soldering, and an input / output side lead wire 18 is connected to the input / output electrode 14 by soldering. (See FIG. 4).

Further, as shown in FIG.
Then, the acoustic matching layer 3 is disposed integrally with the wave transmitting / receiving element 10 by mounting the epoxy resin or the like on the front surface thereof. Further, the damper layer 4 is bonded to the back surface of the wave transmitting / receiving element 10. Thus, the piezoelectric transducer 2 is configured.

Here, a ground-side lead wire 17 is drawn out from the peripheral surface of the damper layer 4, and an input / output-side lead wire 18 is inserted through the lead wire. Here, in order to easily pull out the input / output side lead wire 18, the damper layer 4 may be integrally formed on the back surface of the transmitting / receiving element 10 similarly to the acoustic matching layer 3 after the connection of the input / output side lead wire 18. good.

This piezoelectric transducer 2 is shown in FIG.
As indicated by the dashed line, the metal probe 5 is fitted to the metal probe 5 so that the end face of the acoustic matching layer 3 and the metal probe 5 are flush.

Next, means for connecting the leads 17 and 18 to the connection cable 21 will be described. First, as shown in FIG.
The lead wires 17 and 18 are pulled out from the rear end of the probe thin tube 5 and are connected to the coaxial connection cable 21 in the collective cable 20 through which the metal main tube 7 is inserted. That is, as shown in FIG. 7, the lead wire 17 is connected to the core wire 21a, and the lead wire 18 is connected to the covered wire 21b. After making the same connection for each of the eight pairs of circular electrodes 13 and 14, as shown in FIG. 1, the front edge of the large-diameter metal main pipe 7 is attached to the mounting flange 6 of the metal exploration thin tube 5. Is bonded using an epoxy resin adhesive, and the collective cable 20 is held on the metal main pipe 7 using an epoxy resin coating tube 22. A connector 23 is fixed to the end of the coaxial connection cable 21 pulled out from the end of the collective cable 20, so that connection with an external instrument can be easily performed.

As described above, the metal probe 5 inserted into the blood vessel and the collective cable 20 for connecting to the external instrument
Since the tube case 8 is constituted by the metal main tube 7 through which the tube is inserted, the diameter of the insertion end into the blood vessel can be reduced without causing inconvenience in the electrical wiring. Thus, the 8-channel ultrasonic probe 1 is assembled.

A measurement example using the ultrasonic probe 1 having the following configuration will be described with reference to FIG. In the measurement device, the ultrasonic probe 1 was installed in a water tank, and a pulse voltage was applied from a pulser receiver (Model 5900PR, manufactured by Panatrix) to emit an ultrasonic beam. In addition, a hydrophone (manufactured by Panametrics) is set at a position facing the ultrasonic probe 1 and received by the ultrasonic beam emitted from the ultrasonic probe 1, and is then transmitted to an oscilloscope (manufactured by HP) via a pulsar receiver. ; 54522A). By such measurement, it was confirmed that the ultrasonic beams were independently emitted from all eight channels.

Next, in order to examine the reception characteristics of the ultrasonic probe 1 of the present invention, a reflection echo was measured from a stainless steel plate by a water immersion reflection method. The measurement system used was a measurement system based on the hydrophone method shown in FIG. 8, and a stainless steel plate was installed instead of hydrophone. As a result, it was confirmed that the reflected echo could be captured, and that transmission and reception of ultrasonic waves was possible.
As a result of such measurement, it has been confirmed that the ultrasonic probe 1 can appropriately perform both transmitting and receiving.

By the way, the directivity angle θ indicating the angle at which the sound pressure attenuates to に 対 し with respect to the center axis sound pressure is given by sin θ = 0.704λ / d in the case of a distant sound field. λ: wavelength of sound wave, d: diameter of sound source) (1) Here, the sound source of the wave transmitting and receiving element 10 is the piezoelectric vibrating part 12, which can be obtained by applying a DC voltage between the circular electrodes 13 and 14, so that the diameter d of the sound source is equal to that of the circular electrodes 13 and 14. Equal to the diameter.

As described above, the diameter of the sound source is the circular electrode 13,
14, and each circular electrode 13, 14
Is formed into an arbitrary shape by screen printing or the like.
Therefore, as described above, the diameter D can be reduced,
As is clear from equation (1), the smaller the diameter of the sound source is, the larger the directional angle is. Therefore, good directional angle characteristics can be secured.

In the ultrasonic probe 1 having such a configuration,
The ultrasonic transducer 2 is carried by a metal probe 5 inserted into a blood vessel, and a cable 21 connected to an external instrument is inserted through a large-diameter metal main pipe 7, and each cable 21 is inserted into the metal main pipe 7. Because it is made to connect with
The inner diameter of the metal probe tube 5 is the piezoelectric ceramic element plate 11
Any diameter can be used as long as it can fit, and the diameter can be made as small as possible. For this reason, it is possible to make the distal end into an extremely small diameter that can be inserted into a blood vessel while securing electrical connection.

The ultrasonic probe 1 is inserted into the blood vessel 40 and penetrates deeply into the blood vessel 40 as conceptually shown in FIG. Then, a spherical wave is transmitted forward from one piezoelectric vibrating section 12 and received by all the remaining piezoelectric vibrating sections 12. Next, a three-dimensional image of the inside of the blood vessel 40 can be obtained in real time by sequentially converting the transmitting piezoelectric vibrating units 12 and performing image processing on the received signals. Also,
Direction angle θ of spherical wave radiated by each piezoelectric vibrating part 12
Can be easily widened by reducing the diameter d of the circular electrodes 13 and 14, thereby making the visible range A close and wide. In addition, since the piezoelectric vibrating section 12 is circular, the vibration mode is uniform and simple, the signal processing is simple, the three-dimensional image projected inside the blood vessel 40 is wide and clear, the examination is easy, and the appropriate Diagnosis can be performed reliably.

The use of such an ultrasonic probe is not limited to such medical uses, but is widely used for an ultrasonic endoscope for a factory for detecting cracks and distortion in a pipeline. obtain.

[0033]

According to the ultrasonic probe of the present invention, a circular electrode is formed on the front and back surfaces of a piezoelectric ceramic element plate, and a piezoelectric vibrating portion serving as a sound source is formed in a circumferential direction by polarizing the opposed circular electrodes. Since a plurality of transmitting and receiving elements are provided, a spherical wave is transmitted forward from one of the piezoelectric vibrating parts, and the remaining piezoelectric vibrating parts receive and transmit the piezoelectric vibrating parts to be transmitted in order. By performing the conversion, a three-dimensional image can be easily obtained.

Further, a small-diameter sound source can be easily formed simply by setting the electrode shape, and it is possible to provide a wide directivity angle characteristic by a normal processing method without minimizing the size of the ceramics. The production of the acoustic probe can be facilitated.

Further, the ultrasonic transducer is carried by a metal probe inserted into a blood vessel, and a cable connected to an external instrument is inserted through a large-diameter metal main tube, and each cable is inserted into the metal main tube. Since the inner diameter of the metal exploration thin tube may be any diameter as long as the piezoelectric ceramic element plate can be fitted, the diameter can be made as small as possible. For this reason, it is possible to make the distal end into an extremely small diameter that can be inserted into a blood vessel while securing electrical connection.

As described above, the above-described ultrasonic probe can transmit a spherical wave having a large directivity angle in the forward direction by using the piezoelectric vibrating portion as a transmitting / receiving element of the ultrasonic probe. Therefore, the range that can be visualized is near and wide, and the vibration mode is uniform and simple, so that signal processing is simplified, and wide and clear three-dimensional ultrasonic image information can be obtained. it can. Thus, for example,
When used for intravascular diagnosis, a three-dimensional image of the inside of a blood vessel can be obtained in real time, the accuracy of the ultrasonic diagnostic method can be improved, and further, in various fields such as confirmation of a crack in a conduit. Applicable.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing an example of an ultrasonic probe 1 of the present invention.

FIG. 2 is a perspective view of the wave transmitting / receiving element 10. FIG.

FIG. 3 is a plan view of the transmitting / receiving element 10. FIG.

FIG. 4 is a vertical sectional side view of the wave transmitting / receiving element 10.

5 is a vertical side view of the piezoelectric transducer 2. FIG.

FIG. 6 is a vertical sectional side view showing an assembling step of the ultrasonic probe 1 of the present invention.

FIG. 7 is an enlarged view showing the connection between the lead wires 17 and 18 and the coaxial cable 21.

FIG. 8 is a conceptual diagram showing a measurement example of the ultrasonic probe 1.

FIG. 9 is a conceptual perspective view showing the directional angle of the ultrasonic probe 1 inserted into the blood vessel 40.

FIG. 10 is a conceptual perspective view showing a directional angle of a conventional configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic probe 2 Piezoelectric transducer 3 Acoustic matching layer 4 Damper layer 5 Metal probe thin tube 7 Metal main tube 10 Transmitting / receiving element 11 Piezoelectric ceramic element plate 12 Piezoelectric vibrating part 17, 18 Lead wire 19 20 Collective cable 21 Coaxial Connection cable

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Yasuyuki Okimura 14-18 Takatsuji-cho, Mizuho-ku, Nagoya Japan Special Ceramics Co., Ltd. (72) Yoshinobu Ohara 4-273-1, Omiyacho, Nara, Nara 512 (72) Inventor Fumitaka Ishimori 13-103, 476, Hieda-cho, Yamatokoriyama-shi, Nara Pref.

Claims (1)

[Claims] 1. A plurality of circular electrodes are formed on the front and back surfaces of a piezoelectric ceramic element plate in a circumferential direction, each circular electrode is opposed on the front and back surfaces, and a pair of opposed circular electrodes is polarized.
A wave transmitting / receiving element serving as a piezoelectric vibrating portion between the circular electrodes; an acoustic matching layer provided on a wave transmitting / receiving surface of the wave transmitting / receiving element; and a damper layer provided on a back surface to form an ultrasonic transducer. The acoustic transducer is fitted inside the distal end of the metal probe tube, and the lead wire drawn from each circular electrode is connected to a connection cable inserted into the metal main tube, and the distal end of the metal probe is connected to the metal probe. Joined to the rear end of the tube,
An ultrasonic probe, wherein the connection cable is drawn from a metal main pipe.