JPH0993698A - Ultrasonic wave probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the azimuth resolution and the penetration degree of an ultrasonic wave image from a near distance to a remote distance by emitting a non-diffracting beam (sound field not diffused) with an amplitude distribution of a Bessel function form without large scale and complicated structure. SOLUTION: A piezoelectric element 11 of the ultrasonic wave probe has a piezoelectric section 31 whose lower face is a flat face to form a flat plane which is polarized in the saturation in the broadwise direction. On the other hand, An upper face of the piezoelectric element section 31 is formed to be a 0-th Bessel function form to form a Bessel function surface 32. The Bessel function surface 32 is a form of revolutional body revolved around a center axis 33. A dielectric material 34 having a dielectric constant nearly equal to that of the piezoelectric element section 31 is packed in the recessed part of the Bessel function surface 32. The piezoelectric element 11 forming integrally the piezoelectric element section 31 and the dielectric material 34 has a uniform thickness equal to the thickest part of the piezoelectric element section 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe, and more particularly to an ultrasonic probe characterized by an ultrasonic wave irradiation portion for acquiring information inside a subject.

[0002]

2. Description of the Related Art Conventionally, a generally used ultrasonic probe uses a piezoelectric element having a constant polarization intensity and a uniform thickness, as disclosed in Japanese Patent Laid-Open No. 4-336798. ing. Electrodes formed by baking silver paste or the like are added to both surfaces of the piezoelectric element. The core wire and the shield wire of the coaxial cable are electrically connected to the electrodes on both surfaces. An ultrasonic observation device is connected to the opposite side of the coaxial cable. An acoustic matching layer and an acoustic lens are added to the acoustic radiation surface side of the piezoelectric element. Further, a backside damping layer that absorbs and scatters ultrasonic waves is added to the side opposite to the acoustic radiation surface.

In such an ultrasonic probe, a drive pulse is applied from an ultrasonic observation device to a piezoelectric element via a coaxial cable. Ultrasonic pulses are emitted from the piezoelectric element. The ultrasonic waves emitted to the back side of the piezoelectric element are absorbed by the back damping layer. On the other hand, the ultrasonic waves emitted to the acoustic emission surface side of the piezoelectric element are emitted into the subject through the acoustic matching layer and the acoustic lens.

A part of the ultrasonic wave is reflected at the discontinuity of acoustic impedance in the subject. The reflected ultrasonic waves, that is, ultrasonic echoes are received by the piezoelectric element via the acoustic lens and the acoustic matching layer and converted into electric signals. The electric signal is transmitted to the ultrasonic observation device via the coaxial cable. Signal processing is performed in the ultrasonic observation device to visualize internal information of the subject.

However, in the ultrasonic probe described in the above-mentioned prior art, the ultrasonic lens can converge the ultrasonic beam at a certain distance from the probe. If a thin ultrasonic beam can be obtained, the lateral resolution can be improved in that portion. However, the ultrasonic beam spreads away from the probe. As a result, the lateral resolution, which depends on the beam thickness, also deteriorates. Furthermore, if the ultrasonic waves are diffused, the intensity of the ultrasonic waves will be weakened, so that the depth of penetration will be lowered.

In order to solve such a problem, therefore, US Pat. No. 4,961,252 proposes an ultrasonic probe which emits ultrasonic waves having a Bessel function-like amplitude distribution. Several methods can be considered as a method of generating an ultrasonic wave having a Bessel function-like amplitude distribution. For example, configuration 1): the electrodes of the piezoelectric element are divided into concentric circles, and driving pulses of different voltages are simultaneously applied to the respective electrodes, so that ultrasonic waves emitted by the driving voltage applied to each of the concentric electrodes are emitted. By changing the amplitude of each of the electrodes and controlling the voltage applied to each electrode, an ultrasonic pulse having a Bessel function-like amplitude distribution is emitted.

Structure 2): The polarization intensity of the piezoelectric element is distributed in a Bessel function form. That is, when a drive pulse is applied to the electrodes of the piezoelectric element, an ultrasonic wave having an amplitude corresponding to the polarization intensity is emitted from each part of the surface of the piezoelectric element, and an ultrasonic pulse having a Bessel function-like amplitude distribution is emitted as a whole.

Such US Pat. No. 4,961,2
In 52 ultrasonic probe, “Jian-Yu LU and Jam
es F. Greenleaf, "Ultrasonic nondiffracting transd
ucerfor medical imaging ", IEEE Trans. Ultrason., Fe
rroelec., Freq. Contr., vol.37, no.5, pp438-447,19
As pointed out by "90", ultrasonic waves radiated with a Bessel function-like amplitude distribution form a non-diffraction beam, that is, an ultrasonic beam of uniform thickness that does not spread far away. It has been known. The fact that the beam does not spread in the distance means that the lateral resolution does not deteriorate even in the distance when the B-mode image is formed. Also,
Since the ultrasonic energy does not diffuse, the depth of penetration also improves.

[0009]

However, in the configuration 1) of the ultrasonic probe of US Pat. No. 4,961,252, it is necessary to connect a large number of drive pulse generators and coaxial cables. Therefore, the size and complexity of the probe and the size and complexity of the ultrasonic observation device connected to the probe are inevitable. In particular, if the probe is enlarged, it cannot be used for inspections inside body cavities or inside thin pipes, which limits the field of application.

Further, in the configuration 2), since the polarization intensity of the piezoelectric element is controlled, the polarization intensity of most parts of the element does not reach saturation. A piezoelectric element can relatively easily obtain stable polarization intensity when it is polarized up to the maximum polarization intensity obtained with the material, that is, when it is polarized up to saturation. It is difficult to accurately control the polarization intensity of the. Therefore, it is difficult to stably manufacture piezoelectric elements having the same polarization distribution characteristics.

The present invention has been made in view of the above circumstances, and can emit a non-diffractive beam (a sound field that does not diffuse) due to a Bessel function type amplitude distribution without increasing the size and complexity, and from a short distance. It is an object of the present invention to provide an ultrasonic probe capable of improving the lateral resolution and the depth of penetration of an ultrasonic image up to a long distance.

[0012]

An ultrasonic probe of the present invention is an ultrasonic probe in which an ultrasonic beam is generated by longitudinal vibration of thickness of a symmetric piezoelectric layer, wherein the piezoelectric layer is A non-piezoelectric dielectric having a thickness that varies as a function of distance from an axis, the non-piezoelectric dielectric being provided on the surface of the piezoelectric layer and having a dielectric constant substantially the same as the piezoelectric layer. It has a dielectric layer that makes the total thickness of the layers uniform.

In the ultrasonic probe of the present invention, the piezoelectric layer has a thickness that changes as a function of the distance from the axis,
By making the total thickness of the dielectric layer, which is a non-piezoelectric dielectric provided on the surface of the piezoelectric layer and having substantially the same dielectric constant as the piezoelectric layer, uniform with the piezoelectric layer. Emitting a non-diffractive beam (non-diffusing sound field) with Bessel function type amplitude distribution without increasing size and complexity, improving the lateral resolution and depth of penetration of ultrasonic images from short distance to long distance It is possible to

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 relate to a first embodiment of the present invention, and FIG. 1 is a configuration diagram showing a configuration of an ultrasonic endoscope,
2 is a sectional view showing the configuration of the ultrasonic probe of FIG. 1, FIG. 3 is a sectional view showing the configuration of the piezoelectric element of FIG. 2, and FIG. 3 is a configuration of a modification of the ultrasonic probe of FIG. It is sectional drawing shown.

(Structure) As shown in FIG. 1, an ultrasonic endoscope 1 using the ultrasonic probe according to the present embodiment has a flexible insertion portion 2 which is inserted into a body cavity of a subject. An acoustic window 3 that transmits ultrasonic waves is provided at the tip, and an ultrasonic probe 4 is incorporated inside the acoustic window 3. An auxiliary operation unit 5 and an operation unit 6 are provided on the upper portion of the insertion unit 2.

A motor (not shown) is built in the sub-operation section 5, and it is mechanically connected to a soft shaft (not shown) which is inserted into the insertion section 2 and has an ultrasonic probe 4 fixed at the tip thereof. ing.

A connector 8 and an electric connector 9 are connected to the operation portion 6 via a cord 7. The connector 8 is connected to a light source device (not shown) necessary for optically observing the inside of the body cavity, and the electrical connector 9 is connected to an ultrasonic observation device (not shown).

A coaxial cable 15, which will be described later, connected to the ultrasonic probe 4 is connected to the ultrasonic observation apparatus through the inside of the flexible shaft, the cord 7 and the electric connector 9.

As shown in FIG. 2, the ultrasonic probe 4 has an insulating layer 12 made of an insulating material with the piezoelectric element 11 side facing up.
Is held in. The outside of the insulating layer 12 is surrounded by a metallic housing 13. The upper electrode 14 of the ultrasonic probe 4 is electrically connected to the housing 13 by a conductive wire 20, and is connected to the ultrasonic observation device.
The shield wire 16 of the coaxial cable 15 that transmits a signal for driving and controlling is also electrically connected to the housing 13. The core wire 17 of the coaxial cable 15 is electrically connected to the lower electrode 14 of the ultrasonic probe 4.

An acoustic matching layer 18 made of epoxy resin is attached to the upper side of the ultrasonic probe 4, and the thickness of the acoustic matching layer 18 is 1/4 of the center frequency of the piezoelectric element 11. .

On the other hand, the cylindrical space formed by the lower surface of the ultrasonic probe 4 and the insulating layer 12 is filled with a back braking layer 19 formed by dispersing tansten powder in epoxy. ing.

As shown in FIG. 3, the piezoelectric element 11 has a piezoelectric element portion 31 having a flat lower surface and a flat surface 30.
Is polarized to the saturated state in the thickness direction. On the other hand, the upper surface of the piezoelectric element portion 31 has a shape of a 0th-order Bessel function and forms a Bessel function surface 32. The Bessel function surface 32 has the shape of a rotating body rotated about the central axis 33. The piezoelectric element portion 31 is formed so as to fill the concave portion of the Bessel function surface 32.
A dielectric 34 having a dielectric constant substantially equal to is filled. The piezoelectric element 11 formed by integrally forming the piezoelectric element portion 31 and the dielectric 34 has a uniform thickness equal to the thickest portion of the piezoelectric element portion 31. The electrodes 14 are formed on both surfaces of the piezoelectric element 11 in which the piezoelectric element portion 31 and the dielectric 34 are integrated by baking silver paste or the like.

The method for producing the piezoelectric element 11 will be described below.

Electrodes 14 are attached to both surfaces of a disk-shaped piezoelectric element having a uniform thickness, and polarized to a saturated state. The laser processing machine is used to form the Bessel function surface 32 while paying attention to the temperature so as not to depolarize. With this, the piezoelectric element portion 31 can be created. On the other hand, a disk-shaped piezoelectric element made of the same material is prepared. The electrode 14 is formed on one surface. The surface to which the electrode 14 is not added is processed into a shape in which the Bessel function surface 32 of the piezoelectric element portion 31 and the unevenness are inverted without polarization. With this, the dielectric 34 can be formed.

The piezoelectric element portion 31 and the dielectric body 34 formed by the above method are bonded together with an adhesive. Thereby, the piezoelectric element 11 can be manufactured.

(Operation) By the control of the ultrasonic observation device (not shown), the motor inside the sub-operation section 5 rotates and the ultrasonic probe 4 inside the acoustic window 3 rotates. At the same time, an electric pulse is applied to the coaxial cable 15. The electric pulse is applied to the electrodes 14 on both surfaces of the piezoelectric element 11 of the ultrasonic probe 4 via the coaxial cable 15.

The piezoelectric element portion 31 of the piezoelectric element 11 and the dielectric 3
Since it has substantially the same dielectric constant as 4, the electric field between the electrodes 14 on both surfaces of the piezoelectric element 11 becomes uniform. The dielectric 34 does not generate distortion due to the electric field, but the piezoelectric element portion 31 generates uniform distortion like the electric field due to the inverse piezoelectric effect. Therefore, the amount of displacement of the surface of the piezoelectric element portion 31 is proportional to the thickness of each portion. That is, in each portion of the surface of the piezoelectric element portion 31, a displacement proportional to the thickness of that portion occurs.

Since the thickness of the piezoelectric element portion 31 is distributed in a Bessel function shape, the displacement distribution is also in a Bessel function shape. Since the time required for displacement is constant, the deformation speed of the piezoelectric element portion 31 eventually becomes a Bessel function. Therefore, the amplitude of the emitted ultrasonic wave also shows a Bessel function-like amplitude distribution.

As described above, the piezoelectric element 11 radiates an ultrasonic pulse having a Bessel function-like amplitude distribution.

The ultrasonic waves emitted to the back side of the piezoelectric element 11 are absorbed by the back braking layer 19. On the other hand, the piezoelectric element 11
Of the ultrasonic waves radiated to the acoustic radiation surface side of the acoustic matching layer 1
8. The sound is radiated into the subject through the acoustic window 3.

In the subject, a part of ultrasonic waves is reflected by the discontinuity of acoustic impedance. The reflected ultrasonic waves, that is, ultrasonic echoes are transmitted to the acoustic window 3 and the acoustic matching layer 18.
The piezoelectric element 11 receives the signal via and converts it into an electric signal.
The electric signal is transmitted to the ultrasonic observation device via the coaxial cable 15. Performs signal processing in the ultrasonic observation device,
Visualize the internal information of the subject.

(Effect) As described above, in the ultrasonic probe 4 of the present embodiment, the piezoelectric element 11 radiates an ultrasonic pulse having a Bessel function-like amplitude distribution. This ultrasonic pulse becomes a non-diffracted beam, and hardly diffuses even if it is separated from the piezoelectric element 11. Therefore, ultrasonic beams of almost the same width are emitted from the vicinity of the ultrasonic probe 4 to the distance. As a result, there is no reduction in azimuth resolution or depth of penetration even at a distance. That is, high azimuth resolution and depth of penetration can be obtained from a short distance to a long distance. Moreover, the ultrasonic probe 4
The ultrasonic diagnostic apparatus does not become large or complicated.

As the dielectric 34, the piezoelectric element portion 31 is used.
You may use the material different from what was used for. That is, as long as the dielectric constant is the same as that of the piezoelectric element portion 31, a cheaper material than that used for the piezoelectric element portion 31 or a material that can be easily processed may be selected. By doing so, the configuration can be made inexpensively.

Further, as the backside braking layer 19, a material such as silicon or latex rubber may be selected instead of epoxy. Also, instead of tungsten powder, zirconia,
Alumina and other powders or fibers of metal or metal oxide may be used. By using a material having a high braking effect in this way, the waveform of the emitted ultrasonic wave can be shortened and the distance resolution can be increased.

Further, instead of placing the motor for rotating the ultrasonic probe 4 close to the operating portion 6, a small pulse motor is arranged near the ultrasonic probe 4 and used. May be configured to rotate. At this time, the step ratio of the pulse motor / the speed reduction ratio N of the speed reducer to be interposed between the ultrasonic vibrator and 360 ° / the ultrasonic probe 4 is 1
Match the number of ultrasonic pulses emitted during rotation.

By doing so, an ultrasonic pulse is radiated each time one pulse is input to the pulse motor, so the angle during which the ultrasonic pulse is radiated becomes constant. Therefore, even if the rotation angle is not detected by an encoder or the like, ultrasonic pulses can be radiated at regular angular intervals to perform radial scanning, and an ultrasonic image without distortion can be obtained. Further, it is possible to avoid image shake and distortion due to uneven rotation of the flexible shaft.

Further, as shown in FIG. 4, the ultrasonic probe 4
The outer surface may be covered with a coat film 41 made of a material having low moisture permeability. As the material, a Teflon film or rubber is used.

The coating film 41 penetrates the acoustic matching layer 18 and the housing 3 from the acoustic medium or water that fills the periphery of the ultrasonic probe 4 and propagates ultrasonic waves, and the acoustic matching layer 18 and the piezoelectric element. The interface 11 can be prevented from peeling off, and the durability of the ultrasonic probe 4 can be improved.

5 and 6 relate to the second embodiment of the present invention, FIG. 5 is a perspective view showing the shape of the piezoelectric element, and FIG. 6 is the shape of the linear array element constituted by the piezoelectric element of FIG. FIG.

Since the second embodiment is almost the same as the first embodiment, only different points will be described, the same components will be denoted by the same reference numerals, and description thereof will be omitted.

(Structure) In the ultrasonic probe of the second embodiment, instead of the piezoelectric element 11 of the first embodiment, as shown in FIG. 5, a zero-order Bessel function type columnar body is used. As shown in FIG. 6, the piezoelectric element 51 having a shape is used.
A linear array element 52 formed by arranging a large number of the elements is used.
Other configurations are the same as those of the first embodiment.

(Function) The thickness of the ultrasonic beam in the scanning direction is electronically controlled by the time difference between the timings at which the respective elements are driven. The thickness of the ultrasonic beam in the thickness direction, which is orthogonal to the scanning direction, is obtained by the ultrasonic probe of the second embodiment as a non-diffracted sound field that does not spread over a long distance. Other operations are the same as those of the first embodiment.

(Effect) Conventionally, the ultrasonic beam is converged by using an acoustic lens in the thickness direction. However, in that method, the ultrasonic beam is diffused rapidly beyond the focal length of the acoustic lens, resulting in deterioration of lateral resolution.

However, according to the ultrasonic probe of the second embodiment, it is possible to keep the thickness of the ultrasonic beam in the thickness direction constant and reduce the deterioration of the lateral resolution even at a distance.

FIG. 7 is a sectional view showing the structure of the piezoelectric element according to the third embodiment of the present invention.

Since the third embodiment is almost the same as the first embodiment, only different points will be described, the same components will be denoted by the same reference numerals, and description thereof will be omitted.

(Structure and Operation) In the piezoelectric element 11 of the ultrasonic probe of the third embodiment, as shown in FIG. 7, the Bessel function surface 32 on the upper surface of the piezoelectric element section 31 has a zero-order Bessel function. It is formed in the shape of the absolute value of. The positive portion of the Bessel function value is polarized by the upward arrow, and the negative portion of the Bessel function value is polarized by the downward arrow.

The procedure for manufacturing the piezoelectric element 11 will be described below.

Electrodes 14 are attached to both surfaces of two disk-shaped piezoelectric elements having a uniform thickness and polarized to a saturated state. Using a laser processing machine, paying attention to the temperature so as not to depolarize,
Process into the shape of the Bessel function surface. At this time, for one sheet, only the shape of the positive portion of the Bessel function is created. The other one has the polarization direction reversed and only the shape of the negative part of the Bessel function is created. The piezoelectric element portion 31 is formed by the processed two disk-shaped piezoelectric elements.

On the other hand, a disk-shaped piezoelectric element made of the same material is prepared. The electrode 14 is formed on one surface. The surface without the electrode 14 is processed into a shape in which the absolute value of the Bessel function and the unevenness of the piezoelectric element portion 31 are inverted without polarization.
With this, the dielectric 34 can be formed.

Two processed disk-shaped piezoelectric elements formed by the above method, that is, the piezoelectric element portion 31 and the dielectric 34.
And are glued together. Thereby, the piezoelectric element 11 can be manufactured.

The other structure is the same as that of the first embodiment.

(Operation) In a portion where the polarization directions are opposite, ultrasonic waves having mutually opposite phases are radiated. Other operations are the same as those of the first embodiment.

(Effect) As described above, in the third embodiment, the sound pressure distribution of the Bessel function can be accurately obtained. That is, since a Bessel function-like sound pressure distribution can be obtained with high accuracy, a non-open ultrasonic beam that does not spread over a longer distance can be obtained. Therefore, a high lateral resolution can be obtained over a wider range.

[Appendix] (Appendix 1-1) In an ultrasonic probe that generates an ultrasonic beam by thickness longitudinal vibration of an axially symmetric piezoelectric layer, the piezoelectric layer is a function of the distance from the axis. A non-piezoelectric dielectric having a thickness that varies as the piezoelectric layer is provided on the surface of the piezoelectric layer and has substantially the same dielectric constant as the piezoelectric layer, and the total thickness of the piezoelectric layer. An ultrasonic probe characterized by having a dielectric layer for uniforming the temperature.

(Appendix 1-2) The thickness of the piezoelectric layer is t, the distance from the axis is x, a and b are non-negative real numbers, and J0
Is a zero-order Bessel function, the thickness t of the piezoelectric layer is t = J0 (bx) + a.

(Appendix 1-3) The above a is the J0
The ultrasonic probe according to appendix 1-2, wherein the ultrasonic probe is larger than the absolute value of the minimum value of (bx).

(Additional remarks 1-4) Additional remarks 1-1 and 1-2, wherein one surface of the piezoelectric layer is a flat surface.
Alternatively, the ultrasonic probe according to any one of 1-3.

(Additional Item 1-5) The ultrasonic probe according to Additional Item 1-4, wherein the plane of the piezoelectric layer is an acoustic radiation surface.

By the way, in the ultrasonic probe 4 of the conventional ultrasonic endoscope, as shown in FIG.
Is connected to the shaft 104 via the holder 102 and the joint 103. On the other hand, the coaxial cable (not shown) electrically connected to the piezoelectric element (not shown) is the holder 1
02, joint 103, and shaft 104 are inserted. The shaft 104 is formed of a double contact coil and is bendable. The other end (not shown) of the shaft 104 is connected to the motor.

The periphery of the ultrasonic transducer 101 is covered with a sealing body 105 enclosing an acoustic medium that propagates ultrasonic waves. In addition, a connecting portion between the sealing body 105 and the main body 106 of the insertion portion of the ultrasonic endoscope is watertightly and airtightly joined by an adhesive material and a packing 107.

The sealing body 105 is made of thin hard polyethylene and also serves as an acoustic window through which ultrasonic waves pass. Further, the tip of the sealing body 105 is closed by a screw portion of the stopper 108 and an O-ring 109 inserted at the base of the stopper 108.

The shaft tube 110 covering the shaft 104 is also filled with the acoustic medium. Sealing body 10
The inside of 5 and the inside of the shaft tube 110 are separated by an O-ring 111.

Such a conventional ultrasonic endoscope is used by being connected to an ultrasonic observation device (not shown). Then, the electric pulse is applied to the piezoelectric element in the ultrasonic transducer 101, and the ultrasonic pulse is generated. The ultrasonic pulse passes through the acoustic medium and the sealing body and is emitted into the subject. The ultrasonic waves reflected by the discontinuous portion of the acoustic impedance in the subject again pass through the sealing body and the acoustic medium again, and the ultrasonic transducer 10
It is received by the piezoelectric element in 1, converted into an electric signal and sent to the ultrasonic observation apparatus.

A motor (not shown) rotates the shaft 104 under the control of the ultrasonic observation apparatus. The ultrasonic transducer 101 also rotates due to the rotation of the shaft 104. Scanning is performed by transmitting and receiving ultrasonic pulses while rotating to generate an ultrasonic image.

The acoustic medium in the encapsulant 105 is filled with great care so as not to contain bubbles inside. However, with the use of the ultrasonic endoscope, air bubbles from various routes are mixed in the sealed body. As an example of a bubble mixing route, minute bubbles adhering to the screw part of the stopper 108, the holder 102, and the like are released and aggregate to form a large bubble, and between the strands of the shaft 104 formed by a close contact coil. It is conceivable that some of the bubbles remaining in the gap may move over the sealing portion of the O-ring 111 and into the sealing body 105.

By the way, ultrasonic waves have a characteristic of being reflected at a portion where the acoustic impedance changes. If air bubbles having extremely low acoustic impedance exist inside the acoustic medium and the sealing body 105 that have an acoustic impedance relatively close to the subject, most of the ultrasonic waves are reflected at the interface. That is, it becomes impossible to radiate the ultrasonic pulse into the subject in the portion where the bubbles are present. As a result, when the bubbles are small, the image quality of the ultrasonic image deteriorates and artifacts that are false information are generated. When the bubbles are large, the ultrasonic image cannot be generated inside the subject.

In such a case, the stopper 108 is emptied and the air bubbles are removed and the acoustic medium is refilled by using the injection needle. However, it takes time and labor, and the injection needle is inserted in the acoustic window of the sealing body made of thin resin. There was also the possibility of making a hole in.

Therefore, it is possible to prevent or suppress the generation of air bubbles in the sealed body, and to obtain a clear ultrasonic image without deterioration of the image quality of the ultrasonic image and generation of artifacts while eliminating the trouble of removing the air bubbles. The ultrasonic probe will be described.

FIGS. 8 and 9 relate to the first embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.
Is a configuration diagram showing a configuration of an ultrasonic probe, and FIG. 9 is a configuration diagram showing a configuration of a modified example of the ultrasonic probe of FIG.

(Structure) In the ultrasonic probe 4 of the present embodiment, as shown in FIG.
2. It is connected to the shaft 64 via the joint 63. On the other hand, the coaxial cable (not shown) electrically connected to the piezoelectric element (not shown) includes the holder 62 and the joint 6.
3, the shaft 64 is inserted. Shaft 64 is 2
It is made of a heavy contact coil and can be bent. The other end (not shown) of the shaft 64 is connected to the motor.

The periphery of the ultrasonic transducer 61 is covered with a sealing body 65 enclosing an acoustic medium that propagates ultrasonic waves. Further, the connecting portion between the sealing body 65 and the main body 66 of the insertion portion of the ultrasonic endoscope is watertightly and airtightly joined by an adhesive and packing 67.

The sealing body 65 is made of thin hard polyethylene and also serves as an acoustic window for transmitting ultrasonic waves. Further, the tip of the sealing body 65 is closed by a threaded portion of the stopper 68 and an O-ring 69 inserted at the base of the stopper 68.

The acoustic medium is also filled in the shaft tube 70 that covers the shaft 64. An O-ring 71 separates the inside of the sealing body 65 from the inside of the shaft tube 70.

A pressure chamber 73 is formed inside the sealing body 65 by a partition 72 fixed to the holder 62. A capsule 74 is enclosed in the pressurizing chamber 73. The pressure chamber 73 and the space inside the sealing body 65 are separated from each other by the partition 72 and the sealing body 6.
5 is in communication with the gap, but the gap is capsule 74
Is so small that it cannot pass through.

The capsule 74 is a hollow hard polyethylene resin sphere. At the time of assembling the ultrasonic probe, the capsule 74 is cooled down to about zero degrees Celsius, and the encapsulation work is quickly performed.

(Operation) The ultrasonic endoscope is used by being connected to an ultrasonic observation device (not shown). The electric pulse is applied to the piezoelectric element in the ultrasonic transducer 61, and the ultrasonic pulse is generated. The ultrasonic pulse penetrates the acoustic medium and the encapsulant,
Emitted into the subject. The ultrasonic wave reflected by the discontinuous portion of the acoustic impedance in the subject is transmitted through the sealing body and the acoustic medium again, is received by the piezoelectric element in the ultrasonic transducer 61, is converted into an electric signal, and is ultrasonic wave. It is sent to the observation device.

A motor (not shown) rotates the shaft 64 under the control of the ultrasonic observation apparatus. The ultrasonic transducer 61 also rotates due to the rotation of the shaft 64. Scanning is performed by transmitting and receiving ultrasonic pulses while rotating to generate an ultrasonic image.

The capsule 74 contracts in a state where it is cooled to a temperature of about zero degrees Celsius. Therefore, at room temperature, the volume of the capsule 74 is larger than that at the time of encapsulation.
However, since the volume of the pressurizing chamber 73 and the space inside the sealing body 65 that communicates with the pressurizing chamber 73 is limited, the acoustic medium filled in the space is in a pressurized state.

As a result, it is difficult for air bubbles to be mixed from the inside of the shaft tube 70, and the generation of bubbles in the sealing body 65 can be reduced. Furthermore, since pressure is applied to the generated bubbles, the volume of the bubbles can be suppressed.

(Effect) It is possible to prevent or suppress the generation of air bubbles in the sealing body 65, thereby saving time and effort of removing air bubbles, and clear ultrasonic image without deterioration of image quality of ultrasonic image and generation of artifacts. Can be obtained.

The capsule 74 may be made of a resin material other than hard polyethylene, such as Teflon, silicon, or vinyl chloride.

With this structure, the cost can be reduced by using a material that is easily available. Moreover, when a material having high chemical resistance such as Teflon is used, the capsule 74 can be prevented from being damaged by the acoustic medium, and the life of the ultrasonic probe can be extended.

When the capsule 74 and the acoustic medium are sealed, not only the capsule 74 but also the acoustic medium may be cooled to carry out the sealing work.

By doing so, it is possible to prevent the temperature of the capsule 74 from returning to the normal temperature during the sealing operation. Therefore,
The pressurizing effect due to the thermal expansion of the capsule 14 after the encapsulation work can be increased.

Further, a metal sphere may be used as the capsule 74. The material of the metal sphere itself expands and contracts due to temperature changes. Metal spheres are cheaper and easier to obtain than hollow resin spheres.

The capsule 74 may be filled with zinc particles and dilute hydrochloric acid. Zinc dissolves in dilute hydrochloric acid to generate hydrogen. As a result, the capsule 74 expands and pressurizes the inside of the sealing body 65. As a result, it is possible to more strongly pressurize the inside of the sealing body 65 and suppress the generation of bubbles.

Further, what is enclosed in the capsule 74 is, in addition to the above zinc and dilute hydrochloric acid, a combination of a metal having a higher ionization tendency than hydrogen and an acidic liquid, and a combination of any other substance generating a gas. Can be selected.

Further, as shown in FIG. 9, if the partition 72 is formed on the main body 66 of the ultrasonic endoscope, the same effect as that of the present embodiment can be obtained.

Further, in FIG. 8, the ultrasonic transducer 61
The piezoelectric element therein may be connected to the power amplifier via a coaxial cable (not shown). The piezoelectric element in the ultrasonic transducer 61 has a spherical shell shape, and an acoustic matching layer (not shown) having a thickness of ¼ wavelength is added.

With this structure, the burst wave is applied from the power amplifier to the piezoelectric element. A burst wave of ultrasonic waves is emitted from the piezoelectric element and converges at a position somewhat closer to the piezoelectric element than the geometrical focus of the spherical shell of the piezoelectric element. By applying a sufficiently high sound pressure and generating and converging an ultrasonic wave with a high sound pressure, it is possible to crush the calculi existing at the converging position of the ultrasonic wave or burn the living tissue.

That is, if air bubbles are present inside the sealing body 65, the convergence position of ultrasonic waves may be displaced or convergence may be weakened. However, by the same operation as this embodiment,
The generation of bubbles in the sealing body 65 can be prevented or suppressed. Therefore, the ultrasonic waves are accurately focused on the target site,
It is possible to destroy stones and burn living tissue.

FIG. 10 is a structural diagram showing the structure of the ultrasonic probe according to the second embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.

The second embodiment in which the generation of bubbles in the sealed body is blocked or suppressed is almost the same as the first embodiment in which the generation of bubbles in the sealed body is blocked or suppressed. Only different points will be described, and the same components will be denoted by the same reference symbols and description thereof will be omitted.

(Structure) In the present embodiment, as shown in FIG. 10, the sealing body 65 is airtightly and watertightly bonded and fixed to the sealing body stopper 75. The inner surface of the sealing body stopper 75 and the main body 66 of the ultrasonic endoscope insertion portion are engaged with each other by screws. In addition, even if the ultrasonic endoscope is closer to the base side than the screw part,
It is fitted and fixed in a watertight and airtight manner via a ring 76. Other configurations are the same as those of the first embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.

(Operation) When air bubbles are generated in the sealing body 65, the sealing body stopper 75 is rotated. Then
The threaded portion between the closure 75 and the body 66 is tightened.
As a result, the sealing body stopper 75 and the sealing body 5 move to the right, and the volume of the space inside the sealing body 65 is reduced. Sealing body 6
The space inside 5 includes a stopper 68, a stopper 75 for the sealing body, and a sealing body 6
Since it is kept watertight and airtight by the O-ring 76, the pressure increases due to volume reduction. As a result, not only the volume of the capsule 74 in the pressurizing chamber 73 but also the volume of bubbles generated in the sealing body 65 is reduced. Other functions are the same as those of the first embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.

(Effect) Even when the structure of the first embodiment in which the generation of bubbles in the sealed body is prevented or suppressed is used,
Further, a means is provided for allowing the user to relatively easily reduce the air bubbles generated in the sealing body 65 during use to prevent deterioration of the ultrasonic image and the like. As a result, it is possible to reduce costs by reducing the number of regular inspections and maintenance.

FIG. 11 is a constitutional view showing the constitution of the ultrasonic probe according to the third embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.

Since the third embodiment in which the generation of bubbles in the sealed body is prevented or suppressed is almost the same as the second embodiment in which the generation of bubbles in the sealed body is prevented or suppressed, Only different points will be described, and the same components will be denoted by the same reference symbols and description thereof will be omitted.

(Structure) As shown in FIG.
The sealing body stopper 75 is integrated with the main body 66, and several rows of recesses 77 are formed on the circumference of the body 66. The end of the sealing body 65 is thick, and a protrusion 78 is formed. An O-ring 79 is fixed inside the protrusion 78. The recess 77 and the protrusion 78 are fitted together. Other configurations are the same as those of the second embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.

(Operation) When air bubbles are generated in the sealing body 65, the sealing body 65 is pushed to the right. Then, the fitting position between the protrusion 78 at the end of the sealing body 65 and the recess 77 of the main body 66 moves to the right by one recess 77. Therefore, the volume of the space inside the sealing body 65 is reduced. Since the space inside the sealing body 65 is kept watertight and airtight by the plug 68 and the O-ring 79, the pressure increases due to the volume reduction. As a result, not only the volume of the capsule 74 in the pressurizing chamber 73 but also the volume of bubbles generated in the sealing body 65 is reduced.

(Effect) By integrating the sealing body 65 and the sealing body stopper 75, the number of parts can be reduced and the cost can be reduced.

FIG. 12 is a structural diagram showing the structure of an ultrasonic probe according to the fourth embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.

Since the fourth embodiment in which the generation of bubbles in the sealed body is prevented or suppressed is almost the same as the first embodiment in which the generation of bubbles in the sealed body is prevented or suppressed, Only different points will be described, and the same components will be denoted by the same reference symbols and description thereof will be omitted.

(Structure) As shown in FIG. 12, a cylinder 80, which is a rectangular and cylindrical space, is provided in the main body 66. A small motor 81 is fixed in the cylinder 80. A DC motor is used as the motor 81. A power cable (not shown) is connected to the motor 81. The drive shaft of the motor 81 is connected to a shaft 82 having screws (not shown) formed over substantially the entire length. A piston 83 is screwed onto the shaft 82. The outer shape of the piston 83 matches the cross-sectional shape of the cylinder 80. In addition, cylinder 8
A mesh mesh 84 is fixed to the end portion of 0. Other configurations are the same as those of the first embodiment in which the generation of bubbles in the sealed body is prevented or suppressed.

(Operation) When air bubbles are generated in the sealing body 65, power is supplied to the motor 81 to rotate the shaft 82. Since the piston 83 has the same shape as the rectangular cylinder 80, it does not rotate together with the shaft 82. Therefore, as the shaft 82 rotates, it moves leftward along the thread groove of the shaft 82. As a result, the volume of the space inside the sealing body 65 is reduced. Since the space inside the sealing body 65 is kept watertight and airtight, the pressure increases due to the volume reduction. As a result, in addition to the volume of the capsule 74 in the pressurizing chamber 73,
The volume of bubbles generated in the sealing body 65 is also reduced.

(Effect) It is possible to reduce the internal volume of the sealing body and to reduce the bubbles inside the sealing body without requiring the arm strength. In addition, the bubbles can be reduced without removing the ultrasonic endoscope from the subject during the diagnosis.

The motor 81 is not limited to the DC motor, and a stepping motor can be used. By using the stepping motor, the movement amount of the piston 83 can be easily controlled.

The motor 81 is not limited to the DC motor, but an ultrasonic motor can be used. A linear actuator can also be used. As with the stepping motor, the movement amount of the piston 83 can be easily controlled.

[Additional remarks] (Additional remark 2-1) An ultrasonic transducer for applying an electric signal to a piezoelectric element to emit an ultrasonic wave and the ultrasonic probe are sealed, and at least a part of the ultrasonic wave is In an ultrasonic probe having a sealing body having a transparent acoustic window and an acoustic medium sealed in the sealing body, a pressure chamber communicating with the sealing body is provided, and the pressure chamber is provided. An ultrasonic probe, wherein a volume is increased after disposing a capsule having a size that cannot pass through a communication path between the pressurizing chamber and the sealing body.

(Additional Item 2-2) The additional item 2 characterized in that the capsule is a hollow plastic ball.
The ultrasonic probe described in -1.

(Additional Item 2-3) The ultrasonic probe according to Additional Item 2-1 is characterized in that the capsule is a hollow metal sphere.

(Additional Item 2-4) In any one of the additional items 2-1, 2-2 or 2-3, the capsule is sealed in the acoustic medium in a cooled state. The ultrasonic probe described.

In the ultrasonic probe of the additional items 2-1 to 2-4, the tip of the ultrasonic probe is applied to a living body to be examined. An ultrasonic image is acquired by emitting ultrasonic waves while rotating an ultrasonic transducer inside the ultrasonic probe. Since the capsule is cooled and enclosed in the pressurizing chamber in a reduced volume state, the capsule thermally expands at room temperature to apply pressure to the pressurizing chamber. Therefore, mixing of bubbles from the shaft tube is less likely to occur, and the generation of bubbles in the sealed body can be reduced. Furthermore, since pressure is applied to the generated bubbles, the volume of the bubbles can be suppressed.

(Additional Item 2-5) The additional item 2-1, 2-2 or 2-3, wherein the capsule contains a plurality of materials which generate a gas by a chemical reaction.
The ultrasonic probe according to any one of 1.

In the ultrasonic probe of Supplementary Note 2-5, after encapsulating the capsule in the pressure chamber, bubbles are generated inside,
Expand the volume. Thereby, pressure is applied to the pressurizing chamber. Therefore, mixing of bubbles from the shaft tube is less likely to occur, and the generation of bubbles in the sealed body can be reduced. Furthermore, since pressure is applied to the generated bubbles, the volume of the bubbles can be suppressed.

(Additional remarks 2-6) Additional remarks 2-1 and 2 are provided with a pressurizing means for pressurizing the inside of the sealed body.
The ultrasonic probe according to any one of -2, 2-3, 2-4, and 2-5.

(Supplementary Note 2-7) The pressurizing means reduces the volume of the sealant by changing the position at which the sealant is fixed to the main body, and the sealant and the pressurizing chamber 7. The ultrasonic probe according to item 2-6, wherein the ultrasonic probe is pressurized.

(Additional Item 2-8) The pressurizing means includes a cylinder communicating with the sealing body, a piston adapted to the cylinder, and an actuator for operating the piston in the cylinder. 7. The ultrasonic probe according to appendix 2-6, wherein the sealing body and the pressure chamber are pressurized by the operation of.

In the ultrasonic probe of Supplementary Notes 2-6 to 2-8, since pressure is mechanically applied to the pressurizing chamber, pressure is also applied to the bubbles inside the sealing body, and the volume is reduced.

[0122]

As described above, according to the ultrasonic probe of the present invention, the piezoelectric layer has a thickness that changes as a function of the distance from the axis and is provided on the surface of the piezoelectric layer. Since the dielectric layer, which is a non-piezoelectric dielectric having substantially the same dielectric constant as the body layer, makes the total thickness with the piezoelectric layer uniform,
Emitting a non-diffractive beam (non-diffusing sound field) with Bessel function type amplitude distribution without increasing the size and complexity, improving the lateral resolution and depth of penetration of ultrasonic images from short distance to long distance The effect is that you can.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an ultrasonic endoscope according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the ultrasonic probe shown in FIG.

FIG. 3 is a cross-sectional view showing the configuration of the piezoelectric element shown in FIG.

FIG. 4 is a cross-sectional view showing a configuration of a modified example of the ultrasonic probe of FIG.

FIG. 5 is a perspective view showing the shape of a piezoelectric element according to a second embodiment of the present invention.

6 is a perspective view showing the shape of a linear array element composed of the piezoelectric element of FIG.

FIG. 7 is a sectional view showing the configuration of a piezoelectric element according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram showing a configuration of the ultrasonic probe according to the first embodiment in which generation of bubbles in a sealed body is prevented or suppressed.

9 is a configuration diagram showing a configuration of a modified example of the ultrasonic probe of FIG.

FIG. 10 is a configuration diagram showing a configuration of an ultrasonic probe according to a second embodiment in which generation of bubbles in a sealed body is prevented or suppressed.

FIG. 11 is a configuration diagram showing a configuration of an ultrasonic probe according to a third embodiment in which generation of bubbles in a sealed body is prevented or suppressed.

FIG. 12 is a configuration diagram showing a configuration of an ultrasonic probe according to a fourth embodiment in which generation of bubbles in a sealed body is prevented or suppressed.

FIG. 13 is a configuration diagram showing a configuration of a conventional ultrasonic probe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ultrasonic endoscope 2 ... Insertion part 3 ... Acoustic window 4 ... Ultrasonic probe 5 ... Sub-operation part 6 ... Operation part 7 ... Cord 8 ... Connector 9 ... Electrical connector 11 ... Piezoelectric element 12 ... Insulating layer 13 ... Housing 14 ... Electrode 15 ... Coaxial cable 16 ... Shield wire 17 ... Core wire 18 ... Acoustic matching layer 19 ... Back damping layer 30 ... Flat surface 31 ... Piezoelectric element part 32 ... Bessel function surface 33 ... Central axis 34 ... Dielectric material

Claims (1)

[Claims] 1. An ultrasonic probe that generates an ultrasonic beam by axially vibrating the thickness of a symmetric piezoelectric layer, wherein the piezoelectric layer has a thickness that varies as a function of distance from the axis. A dielectric layer provided on the surface of the piezoelectric layer, the dielectric layer having a dielectric constant substantially the same as that of the piezoelectric layer and having a uniform total thickness with the piezoelectric layer. An ultrasonic probe having: