JP2004089717A - Ultrasonic search unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic search unit which improves a resolution by forming a beam having a slender width and suppressing a decrease in sensitivity remotely in a long focal region. <P>SOLUTION: This ultrasonic search unit of an ultrasonic endoscope includes an insertion unit, a tip cap provided at a tip of the insertion unit, and an ultrasonic vibrator disposed at a predetermined position in the tip cap when inserting the tip cap. The tip cap exhibits a substantially pipe shape, and has a plurality of lens surfaces of a convex curved surface with a desired curvature at an outer surface side in an inserting direction or a direction perpendicular to the inserting direction in such a manner that the vicinity of a central axis passing the central part of the lens is formed lower than the peripheral surface of the lens. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an ultrasonic probe used for an ultrasonic diagnostic apparatus that images a tomographic image in a living body using an ultrasonic echo.

In recent years, by irradiating the living body with ultrasonic waves from an ultrasonic probe or an ultrasonic transducer, receiving reflected ultrasonic waves reflected at a portion where the acoustic impedance changes in the living body, converting the reflected ultrasonic waves into an electric signal, and forming an image. Ultrasonic diagnostic apparatuses for obtaining ultrasonic tomographic images have come to be widely used.

Conventional ultrasonic probes have a concave or convex curved radiation surface so that they have a geometrical focus on the central axis, or have a geometrical focus on the central axis of the transducer A focusing acoustic lens was provided.

However, in such an ultrasonic probe, the beam width is narrowed down near the focal point of the ultrasonic beam, but the ultrasonic beam spreads at a position outside the focal point, so that an image with high resolution can be obtained over a wide range. I couldn't get it.

To solve this problem, Japanese Patent Application Laid-Open No. 51-60491 discloses an ultrasonic probe which forms an effective and virtual annular sound source in front of or behind an ultrasonic probe. .

However, the ultrasonic probe forming this virtual toroidal sound source can obtain a main beam with a narrow beam width over a wide range. However, the sensitivity decreases as the arrival point moves farther, that is, as the measurement depth increases. For this reason, with this beam, it was not possible to obtain an ultrasonic diagnostic image having a resolution sufficient for diagnosis depending on the measurement depth.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an ultrasonic probe having a narrow beam width, forming a beam that suppresses a decrease in sensitivity at a long distance in a long focal range, and improving resolution. Is aimed at.

A first ultrasonic probe according to the present invention includes an insertion portion, a tip cap provided at a tip of the insertion portion, and an ultra-sonic probe inserted through the tip cap and arranged at a predetermined position in the tip cap. In the ultrasonic probe of the ultrasonic endoscope having the ultrasonic vibrator portion, the tip cap has a substantially pipe shape, and has a convex curved surface with a desired curvature on the outer surface side in the insertion direction or a direction orthogonal thereto. A plurality of lens surfaces are provided, and the vicinity of the central axis passing through the center of the lens is formed lower than the peripheral surface of the lens.

A second ultrasonic probe according to the present invention includes an insertion portion, a tip cap provided at a tip of the insertion portion, and an ultra-sonic probe inserted through the tip cap and arranged at a predetermined position in the tip cap. In the ultrasonic probe of an ultrasonic endoscope having an ultrasonic vibrator portion, the tip cap has a substantially pipe shape, and a lens having a concave curved surface with a desired curvature on an outer surface side in an insertion direction or a direction orthogonal thereto. A plurality of surfaces are provided, and the vicinity of the central axis passing through the lens center is formed higher than the lens peripheral surface.

According to the present invention, it is possible to provide an ultrasonic probe having improved resolution by forming a beam having a narrow beam width and suppressing a decrease in sensitivity in a distant place having a long focal range.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 relate to a first embodiment of the present invention. FIG. 1 is a perspective view showing a schematic configuration of an ultrasonic probe, and FIG. 2 is a cross-sectional view taken along a line AA in FIG.

As shown in FIG. 1, an ultrasonic probe (also referred to as an ultrasonic transducer) 1 according to the present embodiment includes a flat, substantially circular piezoelectric element 2 having piezoelectric characteristics as an ultrasonic conversion element, and radiates ultrasonic waves. Front electrode 3a provided on an ultrasonic wave emitting surface for transmitting or receiving ultrasonic waves or an ultrasonic wave transmitting / receiving surface (also simply referred to as a front surface) and a surface opposite to the ultrasonic wave emitting surface of the piezoelectric element 2 (a rear surface with respect to the front surface) The efficiency of sound is increased so as to eliminate the gap between the acoustic impedance of the piezoelectric element 2 and the acoustic impedance of the living body, which are stacked via the rear electrode 3b formed on the piezoelectric element 2 and the front electrode 3a of the piezoelectric element 2. A virtual ring-type combination serving as a focusing means for focusing ultrasonic waves radiated from the acoustic matching layer 4 and the piezoelectric element 2 on the central axis OO 'of the ultrasonic probe 1 and emitting a narrow ultrasonic beam having a long focal area. Lens 5), a backing material 6 formed of a ferrite-containing rubber or the like that attenuates ultrasonic waves to the rear side by being provided through the rear electrode 3b of the piezoelectric element 2; A protective film made of parylene (polyparaxylylene) or the like, which is excellent in water resistance and chemical resistance, covering the surfaces of the electrodes 3a, the back electrode 3b, the acoustic matching layer 4, the combination lens 5, and a part of the backing material 6. 7 mainly. The central axis OO 'is the central axis of the effective surface of the piezoelectric element 2, that is, the sound axis of the ultrasonic wave.

As shown in FIG. 2, the combination lens 5 is configured by combining two acoustic lenses 5a and 5b. Silicon rubber and polyether block amide are disposed on the tip side and constitute the lens on the emission end side. A first acoustic lens 5a formed by a first lens member for setting the sound velocity to v1 and the acoustic impedance to Z1 by using a curved surface having a center-side tip projecting from the peripheral surface, and a lower layer of the first acoustic lens 5a. A second lens member that sets the sound speed to v2 and the acoustic impedance to Z2 using polymethylpentene or the like that is placed on the side and becomes the ultrasonic wave incident side. Two acoustic lenses 5b are combined.

Then, between the sound speed v1 and the sound speed v2, v2> v1
The relationship has been set.
Further, between the acoustic impedance Z1 of the first lens material and the acoustic impedance Z2 of the second lens material, Z1 ≒ Z2 ≒ Zb (acoustic impedance of a living body)
Is set to prevent the sensitivity of the ultrasonic wave emitted to the living body through the two lenses from being lowered.

The acoustic matching layer 4 is a disc-shaped glass having a thickness of λ / 4 (λ is the wavelength of the operating frequency of the ultrasonic wave, the same applies hereinafter) disposed on the ultrasonic wave emitting surface side of the piezoelectric element 2. It is composed of the formed first matching layer 4a, and a second matching layer 4b made of epoxy resin having a thickness of λ / 4 and a disc shape laminated on the first matching layer 4a. A ground wire 8 is connected to the front electrode 3a, and a signal wire 9 is connected to the rear electrode 3b. A signal terminal of an observation device (not shown) is connected via a lead wire 10 in which these wires 8 and 9 are put together. And a ground terminal.

As described above, by disposing the acoustic matching layer for increasing sound efficiency and the virtual ring-type combination lens configured by combining two types of lens members having different sound speeds on the front electrode side of the piezoelectric element, radiation from the piezoelectric element is achieved. The ultrasonic beam pattern is narrowed by passing through the second lens and the first lens to reach the deep part of the living body along the central axis OO ′ in the figure, which is the central axis of the piezoelectric element, without lowering the sensitivity. It is possible to obtain a narrow beam with a long focal range that can be used. As a result, an ultrasonic beam with reduced resolution and a long focal length is emitted from the portion where the ultrasonic probe is disposed to a distant place and an improved ultrasonic image with high resolution can be obtained.

3 and 4 relate to a second embodiment of the present invention, FIG. 3 is a perspective view showing another configuration of the ultrasonic probe, and FIG. 4 is a cross-sectional view taken along the line BB of FIG.
As shown in FIGS. 3 and 4, in the ultrasonic probe 1 </ b> A of the present embodiment, instead of forming the combination lens 5 by combining two types of acoustic lenses 5 a and 5 b having different sound speeds in the first embodiment. A combination lens 5A is formed by combining three types of acoustic lenses 5c, 5d, and 5e having different sound velocities.

The combination lens 5A shown in FIG. 4 has a sound velocity v1 and an acoustic impedance Z1 using silicon rubber, polyether block amide, or the like which is disposed on the distal end side and constitutes the lens on the emission end side. Similarly to the first acoustic lens 5c which is formed in a curved surface shape with the center-side tip protruding from the peripheral surface by the first lens member to be set, and the first acoustic lens 5c disposed below the first acoustic lens 5c. Using a second acoustic lens 5d formed of a second lens member that sets the sound velocity to v2 and the acoustic impedance to Z2 using silicon rubber, polyether block amide, etc., and polymethylpentene forming the ultrasonic wave incident side A third acoustic lens 5 having a curved surface shape with a central portion depressed with respect to a peripheral portion by a third lens member for setting the sound speed to v3 and the acoustic impedance to Z3. It is a combination of the door. That is, the second acoustic lens 5d is filled in the central concave portion of the third acoustic lens 5e.

Then, between the sound speed v1, the sound speed v2, and the sound speed v3, v3>v2> v1 or v3>v1> v2.
The relationship has been set.
Further, between the acoustic impedance Z1 of the first lens material, the acoustic impedance Z2 of the second lens material, and the acoustic impedance Z3 of the third lens material, Z11Z2 ≒ Z3 ≒ Zb (acoustic impedance of a living body)
Is set to prevent the sensitivity of the ultrasonic wave emitted to the living body through the three lenses from decreasing. Other configurations are the same as those of the first embodiment, and the same members are denoted by the same reference numerals and description thereof will be omitted.

As described above, by disposing the acoustic matching layer for increasing sound efficiency and the virtual ring-type combination lens configured by combining three types of lens members having different sound speeds on the front electrode side of the piezoelectric element, radiation from the piezoelectric element is achieved. The ultrasonic beam pattern is narrowed by passing through the third lens, the second lens, and the first lens, thereby lowering the sensitivity along the central axis OO ′ in the figure, which is the central axis of the piezoelectric element, to the deep part of the living body. It is possible to obtain a thin beam with a long focal area that can be reached without any problem. As a result, an ultrasonic beam with reduced resolution and a long focal length is emitted from the portion where the ultrasonic probe is disposed to a distant place and an improved ultrasonic image with high resolution can be obtained. Other functions and effects are the same as those of the first embodiment.

In addition, when a transmission signal is applied to the piezoelectric elements constituting the ultrasonic probes of the above-described first and second embodiments, the ultrasonic intensity (amplitude or sound pressure) at the central portion where the polarization intensity is large. Is formed, and the amplitude weighting function or means that becomes smaller on the peripheral side is formed, so that the side lobes can be more effectively suppressed and the ultrasonic beam radiated from the piezoelectric element can be more effectively transmitted to the center axis OO ′ of the ultrasonic probe. Can emit a narrow beam with a long focal area to the deep part of the living body.

Also, when the shape of the lens on the emission end side is formed into a curved shape in which the central portion is depressed with respect to the peripheral portion, for example, and the ultrasonic beam emitted from the lens is a narrow beam having a long focal range, the lenses may be connected to each other. Is different from the above-mentioned relationship.

5 and 6 relate to a third embodiment of the present invention. FIG. 5 is a perspective view showing another configuration of the ultrasonic probe, and FIG. 6 is a cross-sectional view taken along the line CC of FIG.
As shown in FIG. 5, in the ultrasonic probe 1B of the present embodiment, instead of the flat circular piezoelectric element used in the first embodiment and the second embodiment, the thickness near the center is small and the peripheral portion is thin. The piezoelectric element 2B is used in which the thickness is made thicker and weighted as it goes. Thus, an ultrasonic wave having a high frequency component is output from the central portion, and an ultrasonic wave having a low frequency component is output from the peripheral portion.

In addition, by forming the piezoelectric element 2B as described above, the acoustic matching layer 4B for increasing the efficiency of sound laminated via the front electrode 3a of the piezoelectric element 2B of the ultrasonic probe 1B as shown in FIG. In accordance with the frequency component output from the weighted piezoelectric element 2B, as shown in the figure, the thickness is changed so that the thickness near the center is small and the thickness is increased toward the peripheral portion. ing. Then, the ultrasonic wave radiated from the piezoelectric element 2 is focused on the center axis OO 'of the ultrasonic probe 1B for the acoustic matching layer 4B having the changed thickness, and the ultrasonic beam having a long focal area is narrowed. The combination lens 5B is arranged to emit light.

The combination lens 5B is configured by combining a first acoustic lens 5f and a second acoustic lens 5g formed by two lens members having different sound velocities, respectively. The first acoustic lens 5f to be formed is formed into a curved shape such that the front end on the center side protrudes from the peripheral surface using silicon rubber, polyether block amide, or the like which is a first lens member for setting the sound speed to v1 and the acoustic impedance to Z1. are doing. Polymethylpentene, which is a second lens member for setting the sound speed to v2 and the acoustic impedance to Z2 in accordance with the characteristics of the piezoelectric element 2B and the acoustic matching layer 4B, is provided on the lower ultrasonic wave incident side of the first acoustic lens 5f. It is a combination with a second acoustic lens 5g having a continuous curved surface formed such that a convex curved surface is formed in the peripheral portion using the method described above, and the center is lowered with respect to the peripheral surface having a concave central portion. .

And, between the sound speed v1 and the sound speed v2, v2> v1
The relationship has been set.
Further, between the acoustic impedance Z1 of the first lens material and the acoustic impedance Z2 of the second lens material, Z1 ≒ Z2 ≒ Zb (acoustic impedance of a living body)
Is set to prevent the sensitivity of the ultrasonic wave emitted to the living body through the two lenses from being lowered. Other configurations are the same as those of the first embodiment, and the same members are denoted by the same reference numerals and description thereof will be omitted.

In this way, the piezoelectric element is weighted so that the thickness near the center is thinner and the thickness is increased toward the peripheral portion, and the main component of the ultrasonic wave output from the piezoelectric element is reduced in a living body at a long distance with little attenuation. A virtual ring-type combination lens composed of an acoustic matching layer for increasing the sound efficiency in accordance with the frequency characteristics and two types of lens members having different sound speeds is arranged on the front electrode side of the piezoelectric element in addition to the frequency component. As a result, an ultrasonic beam pattern mainly composed of a low-frequency component radiated from the piezoelectric element passes through the second lens and the first lens and is narrowed along a central axis OO ′ in the figure, which is the central axis of the piezoelectric element. As a result, it is possible to obtain a thin beam having a long focal range that can reach a deep part of a living body without lowering the sensitivity. Other functions and effects are the same as those of the first embodiment.

7 and 8 relate to a fourth embodiment of the present invention. FIG. 7 is a perspective view showing another configuration of the ultrasonic probe, and FIG. 8 is a cross-sectional view taken along the line DD of FIG. .
As shown in FIGS. 7 and 8, in the ultrasonic probe 1 </ b> C of the present embodiment, instead of forming the combination lens 5 </ b> B by combining two kinds of acoustic lenses 5 f and 5 g having different sound speeds in the third embodiment, A combination lens 5C is configured by combining three types of acoustic lenses 5h, 5j, and 5k having different sound velocities.

As shown in FIG. 8, the combination lens 5C according to the present embodiment is a first lens member which is disposed on the distal end side and sets the sound speed of the output end side lens to v1 and the acoustic impedance to Z1. Similarly to the first acoustic lens 5h, which is formed into a curved shape with the center-side tip projecting from the peripheral surface using ether block amide or the like, and the first acoustic lens 5h disposed below the first acoustic lens 5h. A second acoustic lens 5j formed by a second lens member that sets the sound speed to v2 and the acoustic impedance to Z2 using silicon rubber, polyether block amide, etc., the sound speed to constitute the ultrasonic wave incident side to v3, and the acoustic impedance to Using a third lens member such as polymethylpentene which is set to Z3, a convex curved surface is formed in the periphery and the center is depressed in the center. It has become a combination of the third acoustic lens 5k of the formed continuously curved shape so as to be lower. That is, the second acoustic lens 5j is filled in the central concave portion of the third acoustic lens 5k.

And, between the sound speed v1, the sound speed v2, and the sound speed v3, v3>v2> v1 or v3>v1> v2.
The relationship has been set.
Further, between the acoustic impedance Z1 of the first lens material, the acoustic impedance Z2 of the second lens material, and the acoustic impedance Z3 of the third lens material, Z11Z2 ≒ Z3 ≒ Zb (acoustic impedance of a living body)
Is set to prevent the sensitivity of the ultrasonic wave emitted to the living body through the three lenses from decreasing. Other configurations are the same as those of the third embodiment, and the same members are denoted by the same reference numerals and description thereof will be omitted.

As described above, by disposing the acoustic matching layer for increasing sound efficiency and the virtual ring-type combination lens configured by combining three types of lens members having different sound speeds on the front electrode side of the piezoelectric element, radiation from the piezoelectric element is achieved. The beam pattern of the ultrasonic wave through the third lens, the second lens, and the first lens to reduce the sensitivity to the deep part of the living body along the central axis OO ′ in the figure, which is the central axis of the piezoelectric element. It is possible to obtain a narrow beam with a long focal area that can be reached without any problem. Other functions and effects are the same as those of the third embodiment.

By the way, the ultrasonic probe arranged at the distal end of the ultrasonic endoscope is generally a vibrator with a concave acoustic lens having a concave front surface, and is formed of polyethylene or the like having an acoustic impedance close to that of a living body. The end cap is covered with water or the like as an acoustic medium. Since the ultrasonic focal point was fixed in this transducer with a concave acoustic lens, an ultrasonic endoscope with an improved resolution that emits a long and narrow ultrasonic beam with a long focal range and suppressed sensitivity at a distant place was developed. Was desired.

9 and 10 relate to an ultrasonic endoscope having a vibrator with a convex acoustic lens, FIG. 9 is a diagram showing a schematic configuration of an ultrasonic probe in which a virtual ring-type lens is arranged, and FIG. It is sectional drawing in the EE plane.
As shown in FIGS. 9 and 10, the ultrasonic probe 11 which is a vibrator with a convex acoustic lens according to the present embodiment has a concave shape in which the front surface has a concave shape in which the thickness near the center is small and the thickness increases toward the peripheral portion. The piezoelectric element 12, which is weighted such that the polarization at the central portion is large and the polarization at the peripheral portion is small, and which is disposed on the front electrode 13 side of the piezoelectric element 12 and has the same acoustic impedance as a living body, also serving as an acoustic matching layer The lens surface is made of a convex curved surface with epoxy resin, which is a lens member that can be set so that the sound speed v4 of the lens is higher than the sound speed v5 of water as an acoustic medium, so that the vicinity of the central axis is lower than the peripheral surfaces of these lenses. And a virtual ring type lens (hereinafter abbreviated as virtual lens) 14. Ferrite which attenuates ultrasonic waves is provided on the rear electrode 15 side of the piezoelectric element 12. A rubber backing material 16 is provided. A ground wire 17 and a signal wire 18 are connected to the front electrode 13 and the rear electrode 15, and are connected to a signal terminal and a ground terminal of an observation device (not shown) via a lead wire 19 in which the wires 17 and 18 are combined. ing. The area around the ultrasonic probe 11 is filled with water having a sound speed of v5 as an acoustic medium.

The virtual lens 14 has a plurality of convex curved surfaces formed on its surface, and is formed with a concave lens center portion 14a. The thickness dimension of the virtual lens 14 on the central axis corresponding to the lens center portion 14a is set to λ / 4. The curvature radii of the plurality of lens curved surfaces are uniformly formed by R1.

In this way, a virtual ring type lens in which a plurality of convex curved surfaces are formed on the surface by using a lens member faster than the sound speed of the ultrasonic medium on the front surface of the concave shape of the piezoelectric element by performing amplitude weighting on the piezoelectric element. By doing so, it is possible to provide an ultrasonic probe that emits a narrow ultrasonic beam having a long focal length while suppressing a decrease in sensitivity in a distant place.

11 and 12 relate to an ultrasonic endoscope having a vibrator with a concave acoustic lens, FIG. 11 is a diagram showing a schematic configuration of an ultrasonic probe in which a virtual ring-type lens is arranged, and FIG. It is sectional drawing in the FF surface.
As shown in FIGS. 11 and 12, the ultrasonic probe 11A, which is a vibrator with a concave acoustic lens of the present embodiment, has a large polarization at the central portion having a concave front surface and a small polarization at the peripheral portion. The piezoelectric element 12 weighted as described above, a first matching layer 20a formed of glass having a thickness of λ / 4 and arranged on the front electrode 13 side of the piezoelectric element 12, and the first matching layer 20a are laminated on the first matching layer 20a. An acoustic matching layer 20 composed of an epoxy resin second matching layer 20b having a thickness of λ / 4 and a lens member that can be set so that the lens sound speed v6 is lower than the sound speed v5 of water as an acoustic medium. A virtual lens 14A formed by using a silicone rubber to make the lens surface concavely curved so that the vicinity of the central axis is higher than the peripheral surface of the lens, and a Paris having excellent water resistance and chemical resistance covering the surface of the virtual lens 14A. Down is composed of a protective film 21 formed in (polyparaxylylene) or the like. The area around the ultrasonic probe 11 is filled with water having a sound speed of v5 as an acoustic medium.

The virtual lens 14A has a plurality of concave curved surfaces on its surface and is formed to have a shape in which the lens central portion 14a protrudes, and the curvature radii of the plurality of lens curved surfaces are uniformly formed by R2. Other configurations are the same as those of the vibrator with a convex acoustic lens shown in FIGS. 9 and 10.

As described above, the piezoelectric element is subjected to the amplitude weighting, and a virtual ring type lens having a plurality of concave curved surfaces formed on the surface thereof by using a lens member having a speed lower than the sound speed of the ultrasonic medium is disposed on the front surface of the concave shape of the piezoelectric element. Accordingly, it is possible to provide an ultrasonic probe that emits a thin ultrasonic beam having a long focal length while further suppressing a decrease in sensitivity at a distant place.

In the acoustic lens having the above-described shape, a convex (or concave) Teflon type corresponding to a desired lens shape is disposed on the piezoelectric element or the acoustic matching layer, and epoxy resin, silicon rubber, or the like is provided in the mold. This is formed into a desired shape by injecting and curing the acoustic lens member.

By the way, it is conceivable to provide an acoustic lens effect to the distal end cap in order to improve the resolution of the ultrasonic endoscope by radiating an ultrasonic beam having a long and narrow focus area and suppressing a decrease in sensitivity at a distant place.

13 and 14 relate to an ultrasonic endoscope having a distal end cap provided with a convex acoustic lens, FIG. 13 is an explanatory view showing a schematic configuration of a distal end portion of the ultrasonic endoscope, and FIG. 14 is an ultrasonic transducer. FIG. 3 is an explanatory diagram illustrating a configuration of a unit.
As shown in FIG. 13, the distal end portion 30 of the ultrasonic endoscope includes an insertion portion 31, a distal end cap 32 provided at a distal end of the insertion portion 31, and an inner end of the distal end cap 32 which is inserted through the insertion portion 31. It is mainly composed of an ultrasonic vibrator part 33 arranged at a predetermined position, and water 34 having a sound velocity of v5 is injected into the insertion part 31 and the tip cap 32 as an acoustic medium. The arrow G in the figure indicates the direction in which the ultrasonic endoscope distal end portion 30 is inserted.

The tip cap 32 has a substantially pipe shape, and is a cap member such as polyethylene or polymethylpentene, which is a cap member that can be set so that the sound speed v4 is higher than the sound speed v5 of water as an acoustic medium. A plurality of convexly curved lens surfaces 32a having a desired curvature are provided on the outer surface side in the direction in which the lens is to be formed, and the vicinity of the central axis is formed so as to be lower than the peripheral surfaces of these lenses. . Thus, the ultrasonic waves emitted from the ultrasonic vibrator section 33 are focused on the central axis OO 'passing through the lens center portion 32b, and a narrow ultrasonic beam having a long focal area is emitted.

As shown in FIG. 14, the ultrasonic vibrator unit 33 includes a flat-plate-shaped piezoelectric element 35 whose amplitude is weighted so that the polarization at the center is larger than that of the peripheral part, and an ultrasonic wave that emits ultrasonic waves or transmits and receives ultrasonic waves. A front electrode 36 provided on a radiation surface or an ultrasonic transmitting / receiving surface (also simply referred to as a front surface), a rear electrode 37 formed on a surface of the piezoelectric element 35 opposite to the ultrasonic radiation surface, and a front electrode of the piezoelectric element 35 An acoustic matching layer 38 made of a flat epoxy resin and having a thickness of λ / 4, which is laminated on the front surface through the front surface 36 to increase sound efficiency, and a rear side electrode 37 provided via the rear electrode 37 of the piezoelectric element 35 A rubber backing material 39 containing ferrite for attenuating ultrasonic waves to the ground, a ground wire 40 connected to the front electrode 36, a signal wire 41 connected to the rear electrode 37, and these wires 40, 41 It is composed of a lead wire 42 to the Summary and. The ground wire 40 and the signal wire 41 are connected to the ground terminal and the signal terminal of an observation device (not shown) via the lead wire 42.

Thus, the convex virtual lens in which the tip cap is provided with a plurality of convex curved lens surfaces formed of a resin in which the sound speed v4 is higher than the sound speed v5 of the water as the acoustic medium, the central polarization is larger than that of the peripheral portion. By providing the piezoelectric element in the shape of a flat plate that is weighted in such a way as to be amplitude-weighted, it is possible to provide an ultrasonic endoscope that further suppresses a decrease in sensitivity at a distant place and emits a thin ultrasonic beam having a long focal range.

Also, since the convex virtual lens provided on the tip cap starts the lens effect from the stage where the ultrasonic wave radiated from the piezoelectric element is incident on the inner peripheral surface of the tip cap, the focal point has moved by half the inner diameter of the tip cap. And sensitivity reduction at a distant place can be improved.

15 and 16 relate to an ultrasonic endoscope having a distal end cap provided with a concave acoustic lens, and FIG. 15 is an explanatory view showing a schematic configuration of a distal end portion of the ultrasonic endoscope. FIG. 16 is a diagram illustrating a schematic configuration of an ultrasonic probe, and FIG. 16 is an explanatory diagram illustrating a configuration of an ultrasonic transducer unit.
As shown in FIG. 15, the distal end portion 30 of the ultrasonic endoscope includes an insertion portion 31, a distal end cap 43 provided at a distal end of the insertion portion 31, and a distal end cap 43 inserted through the insertion portion 31. It is mainly constituted by an ultrasonic vibrator part 44 arranged at a predetermined position. Water 34 having a sound velocity of v5 is injected into the insertion part 31 and the tip cap 43 as an acoustic medium.

The tip cap 43 has a substantially pipe shape, and is a silicone rubber which is a cap member that can be set so that the sound speed v6 is lower than the sound speed v5 of water as an acoustic medium. A plurality of concave lens surfaces 43a having a desired curvature are provided at the center of the lens so that the vicinity of the central axis is higher than the peripheral surfaces of the lenses. Thus, the ultrasonic wave radiated from the ultrasonic vibrator portion 44 is focused on the central axis OO 'passing through the lens central portion 43b to emit a narrow ultrasonic beam having a long focal range.

As shown in FIG. 16, the ultrasonic vibrator portion 44 includes a piezoelectric element 45 having a convex curved surface in which the polarization at the center is amplitude-weighted so as to be larger than that at the periphery, and a front electrode provided on the front surface of the piezoelectric element 45. 46 and a rear electrode 47 formed on the rear surface of the piezoelectric element 45, and a flat plate-shaped epoxy resin having a thickness of λ / 4 which is laminated on the front surface via the front electrode 46 of the piezoelectric element 45 to increase sound efficiency. An acoustic matching layer 48, a ferrite-containing rubber backing material 49 provided through a rear electrode 47 of the piezoelectric element 45 to attenuate ultrasonic waves to the rear side, and a ground wire connected to the front electrode 46. 50, a signal line 51 connected to the rear electrode 47, and a lead wire 52 obtained by combining the electric wires 50 and 51 together. The ground wire 50 and the signal wire 51 are connected to the ground terminal and the signal terminal of an observation device (not shown) via the lead wire 52.

Thus, the concave virtual lens in which the tip cap is provided with a plurality of concave curved lens surfaces formed of silicon rubber whose sound speed v4 is lower than the sound speed v5 of the sound medium of water, the central polarization becomes larger than that of the peripheral portion. Is provided for the piezoelectric element having a convex curved surface shape weighted in such a manner as described above, so that an apparent aperture of the vibrator portion is enlarged to further suppress a decrease in sensitivity in a distant place and emit a thin ultrasonic beam having a long focal range. An ultrasonic endoscope can be provided.

In addition, the above-mentioned distal end cap is configured to be detachable from the distal end portion of the ultrasonic endoscope, and a plurality of types of distal end caps formed by changing the diameter or inner diameter of the distal end cap or the radius of curvature of the lens curved surface. Is prepared, it is possible to provide an ultrasonic endoscope having a different focal range by a simple operation of simply changing the tip cap as appropriate.

By the way, in the conventional acoustic lens focusing type probe, the beam width at the focal position could be narrowed, but the beam width was wide at a position other than the focal point. Further, in the virtual ring probe in which the virtual ring acoustic lens is arranged as described above, an ultrasonic beam having a substantially uniform beam width can be obtained from a near field to a distant field. Depending on the relationship between the radius of curvature of the curved surface and the imaginary ring radius, the beam width becomes almost uniform from near field to far field, but this beam width is radiated to near field away from wide field. Some were. For this reason, it is desired to construct a virtual ring-type acoustic lens of an ultrasonic probe that can irradiate an ultrasonic beam with high resolution from a near field to a far field by narrowing the beam width without fail. Had been rare.

17 and 18 relate to the configuration of an ultrasonic probe provided with a virtual ring-shaped acoustic lens, and FIG. 17 is an explanatory diagram showing a schematic configuration of an ultrasonic probe provided with a convex virtual ring-shaped acoustic lens. FIG. 18 is a cross-sectional view taken along the line HH in FIG. 17 and illustrates the relationship between the radius of curvature R of the virtual ring-type acoustic lens and the distance r from the central axis of the effective surface of the piezoelectric element to the center of the curved surface of the lens. FIG.
As shown in FIGS. 17 and 18, the ultrasonic probe 61 of this embodiment includes a flat-plate-shaped piezoelectric element 62 in which Bessel-type polarization weighting is performed so that the central polarization is larger than that of the peripheral part, and An acoustic matching layer 64 made of an epoxy resin having a thickness of λ / 4 disposed on the front electrode 63 side of the element 62, and a lens formed of a convex shape using an epoxy resin or the like having a lens sound speed v8 higher than the sound speed v7 of a living body; A virtual ring type acoustic lens 65 having a surface, a ferrite-containing rubber backing material 67 provided on the rear electrode 66 side of the piezoelectric element 62 for attenuating ultrasonic waves, and an earth wire 68 connected to the front electrode 63. , And a signal line 69 connected to the rear electrode 66, and a lead wire 70 obtained by integrating the electric wires 68, 69. The electric wires 68 and 69 are connected to a signal terminal and a ground terminal of an observation device (not shown) via a lead wire 70.

As shown in FIG. 18, the central axis of the virtual ring acoustic lens 65 coincides with the central axis of the effective plane of the piezoelectric element 62, and the surface of the virtual ring acoustic lens 65 has a plurality of uniform radiuses of curvature. A lens surface having a convex curved surface is formed, and the lens central portion 65a is formed in a concave shape so that the vicinity of the central axis is lower than the peripheral surfaces of these lenses. In this surface shape, when the radius of curvature of the lens curved surface is R and the distance from the center axis to the center of the curved surface of the lens is r, the following relationship is set between R and r.

2 <R / r <4
As a result, the ultrasonic waves radiated from the Bessel-type polarization weighted plate-shaped piezoelectric element 62 as shown by the solid line, the one-dot chain line, and the two-dot chain line in FIG. A long and narrow ultrasonic beam can be emitted. When the value of R / r is 6, for example, the beam is emitted from a near field to a far field with a wide beam width.

19 and 20 relate to the configuration of an ultrasonic probe provided with a virtual ring-shaped acoustic lens, and FIG. 19 is an explanatory diagram showing a schematic configuration of an ultrasonic probe provided with a concave virtual ring-shaped acoustic lens. FIG. 20 is a cross-sectional view taken along the II plane in FIG. 19, and illustrates the relationship between the radius of curvature R of the virtual ring type acoustic lens and the distance r from the center axis of the effective surface of the piezoelectric element to the center of the curved surface of the lens. FIG.
As shown in FIGS. 19 and 20, an ultrasonic probe 61A according to the present embodiment includes a flat-plate-shaped piezoelectric element 62 in which Bessel-type polarization weighting is performed so that the polarization at the center is larger than that at the peripheral portion. An acoustic matching layer 64 made of epoxy resin and having a thickness of λ / 4 disposed on the front electrode 63 side of the element 62, and a concave lens surface made of silicone rubber or the like whose lens sound speed v9 is lower than the sound speed v7 of a living body. And a virtual ring acoustic lens 65A having The other configuration is the same as the configuration of the ultrasonic probe provided with the virtual ring type acoustic lens shown in FIGS. 17 and 18, and the same members are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIG. 20, the central axis of the virtual ring acoustic lens 65A coincides with the central axis of the effective plane of the piezoelectric element 62, and the surface of the virtual ring acoustic lens 65A has a plurality of uniform radiuses of curvature. A lens surface having a concave curved surface is formed, and the lens central portion 65a is formed in a convex shape so that the vicinity of the central axis is higher than the peripheral surfaces of these lenses. In this surface shape, when the radius of curvature of the lens curved surface is R and the distance from the center axis to the center of the curved surface of the lens is r, the following relationship is set between R and r.

2 <R / r <4
As a result, the ultrasonic waves radiated from the Bessel-type polarization weighted plate-shaped piezoelectric element 62 as shown by the solid line, the one-dot chain line, and the two-dot chain line in FIG. A long and narrow ultrasonic beam can be emitted. When the value of R / r is 6, for example, the beam is emitted from a near field to a far field with a wide beam width.

Note that the present invention is not limited to only the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

[Appendix]
According to the above-described embodiment of the present invention as described in detail above, the following configuration can be obtained.

(1) In an ultrasonic probe that forms at least one effective / virtual annular sound source forward or rearward,
The sound source section is a flat or curved piezoelectric element,
A plurality of acoustic lenses formed of lens members having different sound speeds,
An ultrasonic probe comprising:

(2) The ultrasonic probe according to appendix 1, wherein a thickness dimension of the piezoelectric element having a curved surface shape changes from a sound axis toward the periphery.

(3) The ultrasonic probe according to Supplementary Note 1 or 2, wherein one of the plurality of acoustic lenses is formed on a distal end cap constituting an ultrasonic endoscope.

(4) A plurality of lens surfaces having a desired radius of curvature are provided on a lens surface constituting an emission end side of the ultrasonic wave radiated from the piezoelectric element,
2 <R / r <4 between the radius of curvature (described as R) forming the curved surface of the lens surface and the distance (described as r) from the center axis of the lens to the center forming the curved surface of the lens surface.
4. The ultrasonic probe according to any one of supplementary notes 1 to 3, wherein

(5) The ultrasonic probe according to any one of supplementary notes 1 to 4, wherein the piezoelectric element is weighted so as to decrease the polarization intensity from the center of the sound axis toward the periphery.

1 and 2 relate to a first embodiment of the present invention, and FIG. 1 is a perspective view showing a schematic configuration of an ultrasonic probe. FIG. 1 is a cross-sectional view taken along the line AA in FIG. 1. 3 and 4 relate to a second embodiment of the present invention, and FIG. 3 is a perspective view showing another configuration of the ultrasonic probe. FIG. 3 is a cross-sectional view taken along plane BB in FIG. 3. 5 and 6 relate to a third embodiment of the present invention, and FIG. 5 is a perspective view showing another configuration of the ultrasonic probe. 5 is a cross-sectional view taken along the line CC of FIG. 7 and 8 relate to a fourth embodiment of the present invention, and FIG. 7 is a perspective view showing another configuration of the ultrasonic probe. Sectional view on the DD plane of FIG. 9 and 10 relate to an ultrasonic endoscope having a vibrator with a convex acoustic lens, and FIG. 9 is a diagram showing a schematic configuration of an ultrasonic probe in which a virtual ring lens is arranged. Sectional view on the EE plane of FIG. 9 11 and 12 relate to an ultrasonic endoscope having a transducer with a concave acoustic lens, and FIG. 11 is a diagram showing a schematic configuration of an ultrasonic probe in which a virtual ring-type lens is arranged. Sectional view on the FF plane of FIG. 13 and 14 relate to an ultrasonic endoscope having a distal end cap provided with a convex acoustic lens, and FIG. 13 is an explanatory diagram showing a schematic configuration of a distal end portion of the ultrasonic endoscope. Explanatory drawing showing the configuration of the ultrasonic transducer unit 15 and 16 relate to an ultrasonic endoscope having a distal end cap provided with a concave acoustic lens, and FIG. 15 is an explanatory view showing a schematic configuration of a distal end portion of the ultrasonic endoscope. Diagram showing a schematic configuration of an acoustic probe Explanatory drawing showing the configuration of the ultrasonic transducer unit 17 and 18 relate to the configuration of an ultrasonic probe provided with a virtual ring-shaped acoustic lens, and FIG. 17 is an explanatory diagram showing a schematic configuration of an ultrasonic probe provided with a convex virtual ring-shaped acoustic lens. FIG. 17 is a cross-sectional view taken along the line HH in FIG. 17, illustrating the relationship between the radius of curvature R of the virtual ring-shaped acoustic lens and the distance r from the center axis of the effective surface of the piezoelectric element to the center of the curved surface of the lens. 19 and 20 relate to the configuration of an ultrasonic probe provided with a virtual ring-shaped acoustic lens, and FIG. 19 is an explanatory diagram showing a schematic configuration of an ultrasonic probe provided with a concave virtual ring-shaped acoustic lens. FIG. 19 is a cross-sectional view taken along a line II in FIG. 19, illustrating a relationship between a radius of curvature R of the virtual ring-shaped acoustic lens and a distance r from a central axis of the effective surface of the piezoelectric element to a center of the curved surface of the lens.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic probe 2 ... Piezoelectric element 5a ... 1st acoustic lens 5b ... 2nd acoustic lens OO '... Central axis Attorney Patent Attorney Susumu Ito

Claims (2)

An ultrasonic endoscope having an insertion portion, a distal end cap provided at the distal end of the insertion portion, and an ultrasonic vibrator portion inserted through the distal end cap and arranged at a predetermined position in the distal end cap. In the acoustic probe,
The tip cap has a substantially pipe shape, and a plurality of convexly curved lens surfaces with a desired curvature are provided on the outer surface side in the insertion direction or a direction perpendicular thereto, and the vicinity of the central axis passing through the lens center portion is the lens peripheral surface. An ultrasonic probe characterized by being formed lower. An ultrasonic endoscope having an insertion portion, a distal end cap provided at the distal end of the insertion portion, and an ultrasonic vibrator portion inserted through the distal end cap and arranged at a predetermined position in the distal end cap. In the acoustic probe,
The tip cap has a substantially pipe shape, and a plurality of concave curved lens surfaces with a desired curvature are provided on the outer surface side in the insertion direction or a direction perpendicular thereto, and the vicinity of the central axis passing through the lens center portion is closer to the lens peripheral surface than the lens peripheral surface. An ultrasonic probe characterized by being formed high.

Images