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JPH11285496

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DESCRIPTION JPH11285496
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic probe used in an ultrasonic diagnostic apparatus for imaging a tomographic image in a
living body by utilizing an echo of the ultrasonic wave.
[0002]
2. Description of the Related Art In recent years, a living body is irradiated with ultrasonic waves
from an ultrasonic probe or an ultrasonic transducer, and the reflected ultrasonic waves reflected
by the changed portion of acoustic impedance in the living body are received and converted into
electric signals. By imaging, an ultrasonic diagnostic apparatus for obtaining an ultrasonic
tomographic image has been widely used.
[0003]
The conventional ultrasonic probe has a concave or convex curved surface of the transducer so
as to have a geometric focus on the central axis, or has a geometric focus on the central axis of
the transducer. A focusing acoustic lens was provided.
[0004]
However, in such an ultrasonic probe, although the beam width is narrowed in the vicinity of the
focal point of the ultrasonic beam, the ultrasonic beam spreads at the position out of the focal
point, so a high resolution image is obtained over a wide area. I could not get it.
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1
[0005]
In order to solve this problem, Japanese Patent Application Laid-Open No. 51-60491 discloses an
ultrasonic probe which forms an effective virtual ring-shaped sound source in front of or behind
an ultrasonic probe. .
[0006]
However, although the ultrasonic probe forming this virtual toroidal source can obtain a main
beam with a narrow beam width over a wide range, the more distant the arrival point, ie the
measurement The deeper the depth, the lower the sensitivity.
Therefore, with this beam, an ultrasonic diagnostic image having sufficient resolution for
diagnosis can not be obtained depending on the measurement depth.
[0007]
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 with an improved resolution by forming a
beam with a narrow beam width and a reduction in sensitivity at a long distance in focus area.
The purpose is
[0008]
The ultrasonic probe according to the present invention is an ultrasonic probe which forms at
least one effective virtual imaginary annular sound source in front or rear, and the sound source
section is an ultrasonic probe. A piezoelectric element having a flat plate shape or a curved
surface shape and a plurality of acoustic lenses formed of lens members having different sound
speeds are provided.
[0009]
According to this configuration, the ultrasonic wave emitted from the piezoelectric element
passes through the plurality of acoustic lenses, converges along the central axis of the effective
surface of the ultrasonic probe, and becomes an ultrasonic beam having a long focusing area. I
will leave.
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2
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
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, and FIG. 2 is a cross-sectional view
taken along a plane AA of FIG.
[0011]
As shown in FIG. 1, an ultrasonic probe (also referred to as an ultrasonic transducer) 1 of the
present embodiment emits a ultrasonic wave as a flat plate having a piezoelectric characteristic
as a ultrasonic conversion element and a substantially circular piezoelectric element 2. Front
surface electrode 3a provided on an ultrasonic wave emitting surface for transmitting or
receiving ultrasonic waves or an ultrasonic wave transmitting / receiving surface (also referred to
simply as the front surface), and a surface opposite to the ultrasonic wave emitting surface of this
piezoelectric element 2 To increase the sound efficiency so as to eliminate the gap between the
acoustic impedance of the back surface electrode 3 b formed on the back surface electrode 3 b
and the piezoelectric element 2 stacked via the front surface electrode 3 a of the piezoelectric
element 2. A virtual ring type combination serving as focusing means for focusing the ultrasonic
wave emitted from the acoustic matching layer 4 and the piezoelectric element 2 on the central
axis OO0 of the ultrasonic probe 1 and emitting a thin ultrasonic beam having a long focus area
Lens (The following union Backing material 6 formed of ferrite-containing rubber or the like for
attenuating ultrasonic waves toward the rear side by providing through the rear surface
electrode 3b of the piezoelectric element 2), the piezoelectric element 2 and the front electrode
3a, a back electrode 3b, an acoustic matching layer 4, a combination lens 5 and a part of a
backing material 6 a protective film 7 made of parylene (polyparaxylylene) or the like excellent
in water resistance and chemical resistance And is mainly composed of.
The central axis OO 0 is the effective surface central axis of the piezoelectric element 2, that is,
the sound axis of ultrasonic waves.
[0012]
As shown in FIG. 2, the combination lens 5 is configured by combining two acoustic lenses 5a
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and 5b, and is a silicone rubber, polyether block amide, which is disposed on the tip end side and
constitutes a lens on the exit end side. The first acoustic lens 5a has a first lens member whose
velocity of sound is set to v1 and the acoustic impedance is set to Z1 with a curved surface in
which the tip on the center side protrudes from the peripheral surface and the lower layer of the
first acoustic lens 5a. A second lens member whose sound velocity is set to v2 and its acoustic
impedance is set to Z2 by using polymethylpentene or the like placed on the side and on the
ultrasonic incident side. The two acoustic lenses 5b are combined.
[0013]
Then, the relationship between the sound velocity v1 and the sound velocity v2 is set.
Further, a relationship of Z1 ≒ Z2 Z Zb (acoustic impedance of a living body) is set between the
acoustic impedance Z1 of the first lens material and the acoustic impedance Z2 of the second
lens material, and a living body is set via two lenses. It prevents that the sensitivity of the
ultrasonic wave emitted to the
[0014]
The acoustic matching layer 4 is a disc-shaped glass having a thickness dimension of λ / 4 (λ is
the wavelength of the operating frequency of the ultrasonic wave, the same applies hereinafter)
disposed on the ultrasonic radiation surface side of the piezoelectric element 2 The formed first
matching layer 4a and the second matching layer 4b made of epoxy resin in the shape of a disc
having a thickness of λ / 4 and laminated on the first matching layer 4a are formed.
Further, a ground wire 8 is connected to the front electrode 3a, and a signal wire 9 is connected
to the back electrode 3b, respectively, and a signal terminal of an observation device (not shown)
via a lead wire 10 which combines the electric wires 8 and 9 together. And are connected to the
ground terminal.
[0015]
As described above, since the virtual ring type combination lens configured by combining the
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acoustic matching layer that raises the efficiency of sound and the two types of lens members
having different sound speeds is disposed on the front electrode side of the piezoelectric element,
The beam pattern of the ultrasonic wave is narrowed by passing the second lens and the first
lens, and reaches 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 long narrow beam of focus that can be
As a result, it is possible to obtain an ultrasonic image with high accuracy by emitting an
improved ultrasonic beam with a high resolution and a long resolution in a focusing area with
little decrease in sensitivity from the portion where the ultrasonic probe is disposed to a distance.
[0016]
FIGS. 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, and FIG. 4 is a cross-sectional view
taken along the line B-B of FIG.
As shown in FIGS. 3 and 4, in the ultrasonic probe 1A of the present embodiment, the
combination lens 5 is configured instead of combining the two types of acoustic lenses 5a and 5b
different in sound velocity in the first embodiment. The combination lens 5A is configured by
combining three types of acoustic lenses 5c, 5d, and 5e different in sound velocity.
[0017]
The combination lens 5A configured as shown in FIG. 4 has a sound velocity of v1 and an
acoustic impedance of Z1 using silicone rubber, polyether block amide or the like which is
disposed on the tip side and constitutes the lens on the emission end side. Similarly to the first
acoustic lens 5c formed in a curved surface shape in which the tip on the center side protrudes
from the peripheral surface by the first lens member to be set, and the first acoustic lens 5c
disposed under the first acoustic lens 5c. Using a second acoustic lens 5d formed of a second
lens member setting the sound velocity to v2 and the acoustic impedance to Z2 using silicone
rubber, polyether block amide or the like, and polymethylpentene constituting the ultrasonic
incident side A third acoustic lens 5e formed in a curved shape with a central portion recessed
with respect to the peripheral portion by a third lens member for setting the sound velocity v3
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and the acoustic impedance Z3. It is a combination of.
That is, the second acoustic lens 5d is filled in the central recess of the third acoustic lens 5e.
[0018]
Then, a relationship of v3> v2> v1 or v3> v1> v2 is set between the sound velocity v1 and the
sound velocity v2 and the sound velocity v3. Further, the relationship 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 Z1 Z Z2 Z Z3 Z Zb (acoustic impedance
of the living body) Is set to prevent the sensitivity of the ultrasonic wave emitted to the living
body through the three lenses from being lowered. The other configuration is the same as that of
the first embodiment, and the same reference numerals are given to the same members and the
description will be omitted.
[0019]
As described above, since the virtual ring type combination lens configured by combining the
acoustic matching layer that raises the efficiency of sound and the three types of lens members
having different sound speeds is disposed on the front electrode side of the piezoelectric element,
By passing a third lens, a second lens and a first lens and narrowing the beam pattern of the
ultrasonic wave, the sensitivity is lowered to the deep part of the living body along a central axis
OO 'in the figure which is the central axis of the piezoelectric element It is possible to obtain a
long narrow beam of focus that can be reached without As a result, it is possible to obtain an
ultrasonic image with high accuracy by emitting an improved ultrasonic beam with a high
resolution and a long resolution in a focusing area with little decrease in sensitivity from the
portion where the ultrasonic probe is disposed to a distance. The other actions and effects are
similar to those of the first embodiment.
[0020]
In addition, when a transmission signal is applied to the piezoelectric element which comprises
the ultrasound probe of 1st Embodiment and 2nd Embodiment which were mentioned above, the
ultrasonic intensity (amplitude or sound pressure) in the center part side with large polarization
intensity By forming an amplitude weighting function or means which becomes larger at the
peripheral side and smaller at the peripheral side, the ultrasonic beam emitted from this
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piezoelectric element can be more effectively held down by the side lobe and the central axis OO
'of the ultrasonic probe. A long narrow beam of focus can be emitted along the depth of the living
body.
[0021]
The lenses on the emission end side are formed in a curved shape, for example, with the central
portion recessed with respect to the peripheral portion, and when ultrasonic beams emitted from
the lenses are thin beams having a long focal area, The relationship of the speed of sound of the
is different from the relationship described above.
[0022]
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, and FIG. 6 is a cross-sectional view taken
along the line C-C of FIG.
As shown in FIG. 5, in the ultrasonic probe 1B of this embodiment, the thickness in the vicinity of
the center is thin instead of the flat circular piezoelectric element used in the first and second
embodiments. The piezoelectric element 2 </ b> B is used in which the thickness is thickened and
weighted as it proceeds.
As a result, 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.
[0023]
Further, by forming the piezoelectric element 2B as described above, as shown in FIG. 6, an
acoustic matching layer 4B for enhancing the efficiency of the sound laminated through the front
electrode 3a of the piezoelectric element 2B of the ultrasound probe 1B. In accordance with the
weighted frequency component output from the piezoelectric element 2B, as shown in the figure,
with the thickness near the center being thinner and the thickness becoming thicker toward the
peripheral portion. ing. Then, the ultrasonic wave emitted from the piezoelectric element 2 is
focused on the central axis OO0 of the ultrasonic probe 1B with respect to the acoustic matching
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layer 4B whose thickness is changed, and a thin ultrasonic beam having a long focusing area is
obtained. The combination lens 5B is disposed to emit light.
[0024]
The combination lens 5B is configured by combining a first acoustic lens 5f and a second
acoustic lens 5g respectively formed by two lens members different in sound velocity, and the
emission end side disposed on the tip side is The first acoustic lens 5f to be formed is formed into
a curved surface in which the tip on the center side protrudes from the peripheral surface using
silicone rubber, polyether block amide, etc. which are the first lens members setting the sound
velocity v1 and the acoustic impedance Z1. doing. On the ultrasonic incident side on the lower
layer side of the first acoustic lens 5f, polymethylpentene as a second lens member for setting
the sound velocity to v2 and the acoustic impedance to Z2 in accordance with the characteristics
of the piezoelectric element 2B and the acoustic matching layer 4B. The convex curved surface is
formed in the peripheral part using a etc. and it is a combination with the 2nd acoustic lens 5g of
the continuous curved surface shape formed so that the center may become low to the surface of
the periphery which dented the central part. .
[0025]
And the relationship between the sound velocity v1 and the sound velocity v2 is set. Further, a
relationship of Z1 ≒ Z2 Z Zb (acoustic impedance of a living body) is set between the acoustic
impedance Z1 of the first lens material and the acoustic impedance Z2 of the second lens
material, and a living body is set via two lenses. It prevents that the sensitivity of the ultrasonic
wave emitted to the The other configuration is the same as that of the first embodiment, and the
same reference numerals are given to the same members and the description will be omitted.
[0026]
In this manner, the piezoelectric element is weighted so that the thickness in the vicinity of the
center is thin and the thickness is increased toward the peripheral portion, and the main
component of the ultrasonic wave output from the piezoelectric element is low with little
biological attenuation at long distances. A virtual ring type combination lens composed of an
acoustic matching layer for increasing the sound efficiency according to the frequency
characteristic and a combination of two kinds of lens members having different sound speeds is
03-05-2019
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used on the front electrode side of this piezoelectric element while providing a frequency
component The low frequency component radiated from the piezoelectric element passes the
second lens and the first lens through the second lens and the first lens to narrow it down along
the central axis OO 'in the figure which is the central axis of the piezoelectric element. Thus, it is
possible to obtain a thin beam with a long focal range that can be reached deep into the living
body without reducing the sensitivity. The other actions and effects are similar to those of the
first embodiment.
[0027]
FIGS. 7 and 8 relate to a fourth embodiment of the present invention, and FIG. 7 is a perspective
view showing still another configuration of the ultrasonic probe, and FIG. 8 is a cross-sectional
view of FIG. . As shown in FIGS. 7 and 8, in the ultrasonic probe 1C according to the present
embodiment, the combination lens 5B is configured instead of combining the two types of
acoustic lenses 5f and 5g having different speeds of sound in the third embodiment, A
combination lens 5C is configured by combining three types of acoustic lenses 5h, 5j, and 5k
different in sound velocity.
[0028]
As shown in FIG. 8, the combination lens 5C of this embodiment is a silicone rubber, poly, which
is a first lens member disposed on the tip end side to set the sound velocity v1 and the acoustic
impedance to Z1 constituting the lens on the emission end side. Similarly to the first acoustic lens
5 h formed into a curved surface shape in which the tip on the center side is protruded from the
peripheral surface using ether block amide or the like, and the first acoustic lens 5 h disposed in
the lower layer of the first acoustic lens 5 h The second acoustic lens 5j formed of a second lens
member that sets the sound velocity to v2 and the acoustic impedance to Z2 using silicone
rubber, polyether block amide, etc., the sound velocity v3 that constitutes the ultrasonic incident
side, the acoustic impedance A convex curved surface is formed on the periphery using
polymethylpentene, which is the third lens member set to Z3, and the center is concave with
respect to the peripheral surface. It has become a third combination of the acoustic lens 5k
continuous curved shape formed in Kunar so. That is, the second acoustic lens 5j is filled in the
central recess of the third acoustic lens 5k.
[0029]
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Further, a relationship of v3> v2> v1 or v3> v1> v2 is set between the sound velocity v1 and the
sound velocity v2 and the sound velocity v3. Further, the relationship 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 Z1 Z Z2 Z Z3 Z Zb (acoustic impedance
of the living body) Is set to prevent the sensitivity of the ultrasonic wave emitted to the living
body through the three lenses from being lowered. The other configuration is the same as that of
the third embodiment, and the same reference numerals are given to the same members and the
description will be omitted.
[0030]
As described above, since the virtual ring type combination lens configured by combining the
acoustic matching layer that raises the efficiency of sound and the three types of lens members
having different sound speeds is disposed on the front electrode side of the piezoelectric element,
The beam pattern of the ultrasonic wave is narrowed by passing 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 thin beam with a long focal length that can be reached without. The other
actions and effects are similar to those of the third embodiment.
[0031]
By the way, the ultrasound probe disposed at the tip of the ultrasound endoscope is generally a
transducer with a concave acoustic lens having a concave front surface, and is formed of
polyethylene or the like close to the acoustic impedance of a living body. The tip cap is covered
with water or the like as an acoustic medium. In this concave acoustic lens attached transducer,
since the ultrasonic focus is fixed, the sensitivity degradation in the distance is suppressed, and
the ultrasonic endoscope with improved resolution for emitting a thin ultrasonic beam with a
long focusing area is suppressed. It was desired.
[0032]
9 and 10 relate to an ultrasonic endoscope having a transducer with a convex acoustic lens, and
FIG. 9 is a view showing a schematic configuration of an ultrasonic probe in which a virtual ring
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type lens is disposed, and FIG. It is sectional drawing in an EE surface. As shown in FIGS. 9 and
10, the ultrasonic probe 11 which is a transducer with a convex acoustic lens according to this
embodiment has a thin thickness near the center and a thick thickness toward the peripheral
portion to make the front surface concave The piezoelectric element 12 is weighted such that the
polarization of the central part formed is large and the polarization of the peripheral part is
small, and the same acoustic impedance as the living body which is disposed on the front
electrode 13 side of the piezoelectric element 12 and serves as an acoustic matching layer The
lens surface is made of a convex curved surface with an epoxy resin that is a lens member that
can be set so that the lens sound velocity v4 is higher than the sound velocity v5 of water as an
acoustic medium, and the vicinity of the central axis is lower than these lens peripheral surfaces.
It is mainly composed of the virtual ring type lens (abbreviated as virtual lens hereinafter) 14,
and ferrite containing attenuating ultrasonic waves is included in the back electrode 15 side of
the piezoelectric element 12. A rubber backing material 16 is provided. In addition, an earth 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 an earth terminal of an observation device (not shown)
through a lead wire 19 which combines the electric wires 17 and 18 together. ing. Then, water of
the velocity of sound v5 is filled around the ultrasonic probe 11 as an acoustic medium.
[0033]
The virtual lens 14 has a plurality of convex curved surfaces formed on the surface thereof so
that the lens central portion 14a is recessed. The thickness dimension of the virtual lens 14 on
the central axis corresponding to the lens central portion 14a is λ / 4. The radius of curvature of
a plurality of lens curved surfaces is uniformly formed by R1.
[0034]
Thus, amplitude weighting is applied to the piezoelectric element, and a virtual ring type lens
having a plurality of convexly curved surfaces formed on the front surface of the concave surface
of the piezoelectric element using a lens member faster than the sound velocity of the ultrasonic
medium is disposed. By doing this, it is possible to provide an ultrasonic probe that emits a
narrow ultrasonic beam with a long focusing area while suppressing the decrease in sensitivity at
a distance.
[0035]
11 and 12 relate to an ultrasonic endoscope having a transducer with a concave acoustic lens,
and FIG. 11 is a view showing a schematic configuration of an ultrasonic probe in which a virtual
ring type lens is disposed, and FIG. It is sectional drawing in a FF surface.
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11
As shown in FIGS. 11 and 12, the ultrasonic probe 11A, which is a transducer with a concave
acoustic lens according to the present embodiment, has a large polarization in the central portion
with concave front surface and a small polarization in the peripheral portion. Piezoelectric
element 12 weighted as described above, a first matching layer 20a formed of glass having a
thickness of λ / 4 disposed on the front electrode 13 side of the piezoelectric element 12, and
the first matching layer 20a. Acoustic matching layer 20 consisting of a second matching layer
20b made of epoxy resin having a thickness dimension of λ / 4, and a lens member that can be
set so that the lens sound velocity v6 is lower than the sound velocity v5 of water as an acoustic
medium A virtual lens 14A formed of a silicon rubber with a concave curved lens surface so that
the vicinity of the central axis is higher than the peripheral surface of these lenses, and a Paris
excellent in water resistance and chemical resistance covering the surface of the virtual lens 14A
Down it is composed of a protective film 21 formed in (polyparaxylylene) or the like.
Then, water of the velocity of sound v5 is filled around the ultrasonic probe 11 as an acoustic
medium.
[0036]
The virtual lens 14A is provided with a plurality of concave curved surfaces on its surface to
form a convex lens central portion 14a, and the curvature radiuses of the plurality of lens curved
surfaces are uniformly formed by R2. The other configuration is the same as that of the convex
acoustic lens attached vibrator shown in FIGS.
[0037]
Thus, amplitude weighting is applied to the piezoelectric element, and a virtual ring type lens
having a plurality of concave curved surfaces formed on the surface by using a lens member
slower than the sound velocity of the ultrasonic medium is disposed on the front surface of the
concave surface of the piezoelectric element. Thus, it is possible to provide an ultrasonic probe
that emits a narrow ultrasonic beam with a long focus area by further suppressing the decrease
in sensitivity at a distance.
[0038]
In the acoustic lens of the shape as described above, a convex (or concave) Teflon type
corresponding to the desired lens shape is disposed with respect to the piezoelectric element or
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the acoustic matching layer, and an epoxy resin, silicone rubber, etc. It is formed in a desired
shape by pouring and hardening the member for acoustic lenses.
[0039]
By the way, in order to suppress the decrease in sensitivity at a distance and emit a thin
ultrasonic beam having a long focal range to improve the resolution of the ultrasonic endoscope,
it is considered that the tip cap has an acoustic lens effect.
[0040]
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 It is an explanatory
view showing composition of a part.
As shown in FIG. 13, the ultrasonic endoscope distal end portion 30 is inserted into the insertion
portion 31, the distal end cap 32 provided at the distal end of the insertion portion 31, and the
inside of the insertion portion 31. It is mainly composed of an ultrasonic transducer portion 33
disposed at a predetermined position, and water 34 having an acoustic velocity of v5 is injected
into the insertion portion 31 and the tip cap 32 as an acoustic medium.
The arrow G in the figure indicates the insertion direction of the distal end portion 30 of the
ultrasonic endoscope.
[0041]
The tip cap 32 is a substantially pipe shape, and is a cap member such as polyethylene,
polymethylpentene, etc., which can be set so that the sound velocity v4 becomes higher than the
sound velocity v5 of water as an acoustic medium. A so-called convex virtual lens equipped tip
cap is formed by providing a plurality of convexly curved lens surfaces 32a with a desired
curvature on the outer surface side in the direction to make the vicinity of the central axis lower
than the peripheral surfaces of these lenses. .
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As a result, the ultrasonic wave emitted from the ultrasonic transducer unit 33 is focused on a
central axis OO 'passing through the lens central portion 32b to emit a thin ultrasonic beam
having a long focal area.
[0042]
As shown in FIG. 14, the ultrasonic transducer unit 33 is a flat plate-shaped piezoelectric element
35 whose amplitude is weighted so that the polarization in the center is larger than that in the
peripheral portion, and ultrasonic waves that emit ultrasonic waves or transmit and receive
ultrasonic waves. A front electrode 36 provided on a radiation surface or an ultrasonic
transmission / reception surface (also referred to simply as a front surface), a back surface
electrode 37 formed on the 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 epoxy resin having a thickness of λ / 4 and having a thickness of λ / 4
laminated on the front face through the front face 36 to increase sound efficiency, and provided
on the rear face electrode 37 of the piezoelectric element 35 Backing material 39 made of ferritecontaining rubber for attenuating ultrasonic waves, the ground wire 40 connected to the front
electrode 36, the signal wire 41 connected to the back electrode 37, and the electric wires 40
and 41 It is composed of a lead wire 42 to the summary. The ground wire 40 and the signal wire
41 are connected to the ground terminal and the signal terminal of the observation device (not
shown) through the lead wire 42.
[0043]
As described above, a convex virtual lens provided with a plurality of convex curved surface lens
surfaces formed of a resin whose sound velocity v4 is higher than the sound velocity v5 of the
acoustic medium on the tip cap has a central polarization larger than that of the peripheral
portion. Thus, by providing for the amplitude-weighted flat plate-shaped piezoelectric element, it
is possible to provide an ultrasonic endoscope which emits a thin ultrasonic beam having a long
focusing area while further suppressing the decrease in sensitivity at a distance.
[0044]
In addition, since the convex virtual lens provided on the tip cap starts the lens effect when
ultrasonic waves emitted from the piezoelectric element enter the inner circumferential surface
of the tip cap, the focal point moves by half of the inside diameter of the tip cap. Can be
improved to reduce the sensitivity in the distance.
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[0045]
FIGS. 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
the distal end portion of the ultrasonic endoscope. FIG. 16 is a view showing a schematic
configuration of an acoustic wave probe, and FIG. 16 is an explanatory view showing a
configuration of an ultrasonic transducer unit.
As shown in FIG. 15, the ultrasonic endoscope distal end portion 30 is inserted into the insertion
portion 31, the distal end cap 43 provided at the distal end of the insertion portion 31, and the
inside of the insertion portion 31. Water 34 having a sound velocity v5 is injected into the
insertion portion 31 and the end cap 43 as an acoustic medium.
[0046]
The tip end cap 43 is a substantially pipe-shaped silicone rubber as a cap member which can be
set so that the sound velocity v6 is lower than the sound velocity v5 of water as an acoustic
medium, and the outer surface side in the insertion direction or the orthogonal direction A
plurality of concave curved lens surfaces 43a with a desired curvature are formed so that the
vicinity of the central axis is higher than those of the peripheral surfaces of these lenses.
As a result, the ultrasonic wave emitted from the ultrasonic transducer unit 44 is focused on a
central axis OO 'passing through the lens central portion 43b to emit a thin ultrasonic beam
having a long focal area.
[0047]
As shown in FIG. 16, the ultrasonic transducer unit 44 has a convex curved surface-shaped
piezoelectric element 45 whose amplitude is weighted so that the central polarization is larger
than that of the peripheral portion, and a front electrode provided on the front surface of the
piezoelectric element 45 46 and the back surface electrode 47 formed on the back surface of the
piezoelectric element 45 and the front surface electrode 46 of the piezoelectric element 45 are
laminated on the front surface to increase the sound efficiency. Acoustic matching layer 48, a
backing material 49 made of ferrite-containing rubber which is provided via the rear surface
03-05-2019
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electrode 47 of the piezoelectric element 45 to attenuate ultrasonic waves to the rear side, and
an earth wire connected to the front surface electrode 46 50, a signal line 51 connected to the
rear surface electrode 47, and a lead wire 52 obtained by putting the electric wires 50, 51
together. The ground wire 50 and the signal wire 51 are connected to the ground terminal and
the signal terminal of the observation device (not shown) through the lead wire 52.
[0048]
In this manner, the center of the concave virtual lens provided with a plurality of concave curved
surface lens surfaces formed of silicon rubber whose sound velocity v4 is lower than the sound
velocity v5 of the acoustic medium on the tip cap is larger than the peripheral portion By
providing for the piezoelectric element of convex curved surface shape weighted in amplitude as
described above, the aperture of the apparent transducer portion is enlarged to further suppress
the sensitivity drop in the distance, and a thin ultrasonic beam having a long focusing area is
emitted. An ultrasound endoscope can be provided.
[0049]
A plurality of types of tip caps formed by changing the diameter or the inner diameter of the tip
cap or the radius of curvature of the lens curved surface while the tip cap described above is
configured to be removable from the tip of the ultrasonic endoscope By preparing the above, it is
possible to provide an ultrasonic endoscope with different focal areas by a simple operation of
replacing the tip cap appropriately.
[0050]
By the way, in the conventional acoustic lens focusing probe, although the beam width at the
focal position can be narrowed, the beam width at the position other than the focal position is
wide.
In addition, in the virtual ring type probe in which the virtual ring type acoustic lens as described
above is arranged, an ultrasonic beam of substantially uniform beam width can be obtained from
near field to a far field, but the lens of the virtual ring type acoustic lens Depending on the
relationship between the radius of curvature of the curved surface and the virtual ring radius, the
beam width will be nearly uniform from near field to far field, but this beam width will only be
radiated from near field to wide field. There was also one.
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16
For this reason, it is desirable to construct a virtual ring-type acoustic lens of an ultrasonic probe
that narrows the beam width securely and enables the ultrasonic beam to emit a high-resolution
beam to the near field and far fields. It was rare.
[0051]
17 and 18 relate to the configuration of an ultrasound probe provided with a virtual ring type
acoustic lens, and FIG. 17 is an explanatory view showing a schematic configuration of the
ultrasound probe provided with a convex type virtual ring type acoustic lens FIG. 18 is a crosssectional view taken along the plane H-H in FIG. 17 and illustrates the relationship between the
radius of curvature R of the virtual ring acoustic lens and the distance r from the central axis of
the piezoelectric element effective surface to the center forming the curved surface of the lens. It
is a figure to do. As shown in FIGS. 17 and 18, the ultrasonic probe 61 according to the present
embodiment has a 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
portion, and this piezoelectric 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 lens convexly
formed of epoxy resin or the like whose lens sound velocity v8 is faster than the sound velocity
v7 of the living body A virtual ring type acoustic lens 65 having a surface, a backing material 67
made of ferrite-containing rubber provided on the back surface electrode 66 side of the
piezoelectric element 62 to attenuate ultrasonic waves, and a ground wire 68 connected to the
front surface electrode 63 , And a lead wire 70 in which the wires 68 and 69 are put together.
The electric wires 68 and 69 are connected to the signal terminal and the ground terminal of the
observation device (not shown) through the lead wire 70.
[0052]
As shown in FIG. 18, the central axis of the virtual ring type acoustic lens 65 coincides with the
central axis of the effective surface of the piezoelectric element 62, and the surface of the virtual
ring type acoustic lens 65 has a plurality of uniform radii of curvature. The lens surface of the
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 surface of the lenses. In this
surface shape, assuming that the curvature radius of the lens curved surface is R and the distance
from the central axis to the center forming the curved surface of the lens is r, the following
relationship is set between R and r.
03-05-2019
17
[0053]
2 <R / r <4 As a result, as shown by the solid line, the one-dot and dash line, and the two-dot and
dash line in the figure, the ultrasonic wave radiated from the plate-shaped piezoelectric element
62 subjected to polarization weighting of Bessel type is shown as the central axis OO. It can be
focused to emit a narrow ultrasonic beam with a long focal area. When the value of R / r is, for
example, 6, the beam width is wide, and the beam is emitted from the near field to the far field.
[0054]
19 and 20 relate to the configuration of an ultrasonic probe provided with a virtual ring type
acoustic lens, and FIG. 19 is an explanatory view showing a schematic configuration of an
ultrasonic probe provided with a concave virtual ring type acoustic lens. FIG. 20 is a crosssectional view taken along the line I-I in FIG. 19 and illustrates the relationship between the
radius of curvature R of the virtual ring acoustic lens and the distance r from the central axis of
the piezoelectric element effective surface to the center forming the curved surface of the lens.
FIG. As shown in FIGS. 19 and 20, the ultrasonic probe 61A of this embodiment has a flat plateshaped piezoelectric element 62 in which Bessel-type polarization weighting is performed so that
the central polarization is larger than that of the peripheral portion, and this piezoelectric 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 lens surface concavely formed of silicone rubber
or the like having a lower sound velocity v9 than the sound velocity v7 of a living body And a
virtual ring type acoustic lens 65A. 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 reference numerals are given to the same members and the description will be
omitted.
[0055]
As shown in FIG. 20, the central axis of the virtual ring type acoustic lens 65A coincides with the
central axis of the effective surface of the piezoelectric element 62, and the surface of the virtual
ring type acoustic lens 65A has a plurality of uniform radii of curvature. The lens surface of the
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 surface of these lenses. In this
surface shape, assuming that the curvature radius of the lens curved surface is R and the distance
from the central axis to the center forming the curved surface of the lens is r, the following
03-05-2019
18
relationship is set between R and r.
[0056]
2 <R / r <4 As a result, as shown by the solid line, the one-dot and dash line, and the two-dot and
dash line in the figure, the ultrasonic wave radiated from the plate-shaped piezoelectric element
62 subjected to polarization weighting of Bessel type is shown as the central axis OO. It can be
focused to emit a narrow ultrasonic beam with a long focal area. When the value of R / r is, for
example, 6, the beam width is wide, and the beam is emitted from the near field to the far field.
[0057]
The present invention is not limited to the embodiment described above, and various
modifications can be made without departing from the scope of the invention.
[0058]
[Appendix] According to the above-described embodiment of the present invention as described
above, the following configuration can be obtained.
[0059]
(1) In an ultrasonic probe forming at least one effective virtual virtual annular sound source
forward or backward, the sound source unit is formed of a flat plate-shaped or curved surfaceshaped piezoelectric element and a lens member different in sound velocity An ultrasonic probe
comprising: a plurality of acoustic lenses.
[0060]
(2) The ultrasonic probe according to appendix 1, wherein the thickness dimension of the
curved-surface shaped piezoelectric element changes from the sound axis toward the periphery.
[0061]
(3) The ultrasound probe according to Appendix 1 or 2, wherein one of the plurality of acoustic
lenses is formed on a tip cap constituting an ultrasound endoscope.
[0062]
03-05-2019
19
(4) A plurality of lens surfaces having a desired curvature radius are provided on the lens surface
constituting the emission end side of the ultrasonic wave emitted from the piezoelectric element,
and the curvature radius (described as R) forming the curved surface of the lens surface; The
ultrasound search according to one of Appendices 1 to 3 in which the relationship of 2 <R / r <4
is set between the distance from the lens central axis to the center (described as r) from the lens
central axis to the center forming the curved surface of the lens surface. Tentacle.
[0063]
(5) The ultrasound probe according to any one of appendices 1 to 4, wherein the piezoelectric
element is weighted to reduce the polarization intensity as it goes from the center of the sound
axis to the periphery.
[0064]
As described above, according to the present invention, it is possible to provide an ultrasonic
probe with improved resolution by forming a beam with a narrow beam width and a reduction in
sensitivity at a long distance in a focusing region. can do.
03-05-2019
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