U.S. patent application number 12/029801 was filed with the patent office on 2008-06-26 for ultrasonic probe for intra-cavity diagnosis and manufacturing method thereof.
This patent application is currently assigned to FUJINON CORPORATION. Invention is credited to Koichi Kimura, Toshizumi Tanaka.
Application Number | 20080154135 12/029801 |
Document ID | / |
Family ID | 36668331 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080154135 |
Kind Code |
A1 |
Kimura; Koichi ; et
al. |
June 26, 2008 |
ULTRASONIC PROBE FOR INTRA-CAVITY DIAGNOSIS AND MANUFACTURING
METHOD THEREOF
Abstract
A diagnostic ultrasonic probe for use in body cavities has at
its tip an ultrasonic transducer array, which has a layered
structure wherein a flexible circuit board, an electric circuit, a
backing material, a piezoelectric element array, an acoustic
impedance matching layer and an acoustic lens are formed atop
another on a supporting member. The electric circuit includes at
least one of amplifiers for amplifying echo signals from ultrasonic
transducers, switches for switching over between sending the echo
signals from the ultrasonic transducers and receiving drive signals
for exciting the ultrasonic transducers, a multiplexer for
selective-switching between the echo signals as well as between the
drive signals, an A/D converter for converting the echo signals
from an analog form to a digital form, and a D/A converter for
converting the drive signals from a digital form to an analog
form.
Inventors: |
Kimura; Koichi; (Kanagawa,
JP) ; Tanaka; Toshizumi; (Saitama, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJINON CORPORATION
FUJIFILM Corporation
|
Family ID: |
36668331 |
Appl. No.: |
12/029801 |
Filed: |
February 12, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11299766 |
Dec 13, 2005 |
|
|
|
12029801 |
|
|
|
|
Current U.S.
Class: |
600/463 |
Current CPC
Class: |
A61B 8/445 20130101;
A61B 8/12 20130101; A61B 8/4488 20130101 |
Class at
Publication: |
600/463 |
International
Class: |
A61B 8/12 20060101
A61B008/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2004 |
JP |
2004-360056 |
Claims
1. An ultrasonic probe for intra-cavity diagnosis comprising an
ultrasonic transducer array disposed at a tip of said probe, said
ultrasonic transducer array comprising a plurality of ultrasonic
transducers arranged in an array, and an electric circuit including
at least some of necessary electric elements for activating said
ultrasonic transducers, said electric circuit being formed as a
layer laid under said ultrasonic transducers.
2. An ultrasonic probe as claimed in claim 1, wherein said
ultrasonic transducers are piezoelectric elements.
3. An ultrasonic probe as claimed in claim 1, wherein said
ultrasonic transducers are capacitive micromachined ultrasonic
transducers.
4. An ultrasonic probe as claimed in claim 2, wherein said
ultrasonic transducer array has a layered structure having at least
a flexible substrate, said electric circuit, a backing material, an
array of said piezoelectric elements and an acoustic impedance
matching layer, which are formed atop another on a rigid supporting
member, and wherein said electric circuit and said piezoelectric
elements are connected electrically through wires which are
disposed in said backing material.
5. An ultrasonic probe as claimed in claim 4, wherein said flexible
substrate is a circuit board having a circuit pattern formed
thereon.
6. An ultrasonic probe as claimed in claim 3, wherein said
ultrasonic transducer array has a layered structure having at least
a flexible substrate, said electric circuit and an array of said
capacitive micromachined ultrasonic transducers, which are formed
atop another on a rigid supporting member.
7. An ultrasonic probe as claimed in claim 6, wherein a backing
material is provided between said supporting member and said
flexible substrate.
8. An ultrasonic probe as claimed in claim 6, wherein said
supporting member has an ultrasound absorbing function.
9. An ultrasonic probe as claimed in claim 6, wherein said flexible
substrate is a circuit board having a circuit pattern formed
thereon.
10. An ultrasonic probe as claimed in claim 1, wherein said
electric circuit comprises at least one of amplifiers for
amplifying echo signals from said ultrasonic transducers, switches
for switching over between sending said echo signals from said
ultrasonic transducers and receiving drive signals for exciting
said ultrasonic transducers, a multiplexer for selective-switching
between said echo signals and/or between said drive signals, an A/D
converter for analog-to-digital conversion of said echo signals,
and a D/A converter for digital-to-analog conversion of said drive
signals.
11. An ultrasonic probe as claimed in claim 1, wherein said
ultrasonic transducer array is of a radial electronic scanning type
wherein said ultrasonic transducers are arranged radially in a
concentric circle.
12. An ultrasonic probe as claimed in claim 1, wherein said
ultrasonic transducer array is of a convex electronic scanning type
wherein said ultrasonic transducers are arranged
semi-cylindrically.
13. An ultrasonic probe as claimed in claim 11, further comprising
a wiring cable for connecting said electric circuit to an
ultrasound observing device that generates drive signals for
exiting said ultrasonic transducers and produces ultrasound images
from echo signals received from said ultrasonic transducers, said
wiring cable being connected to a terminal that is provided at an
end portion of a flexible substrate that is electrically connected
to said electric circuit.
14. An ultrasonic probe as claimed in claim 12, further comprising
a wiring cable for connecting said electric circuit to an
ultrasound observing device that generates drive signals for
exiting said ultrasonic transducers and produces ultrasound images
from echo signals received from said ultrasonic transducers, said
wiring cable being connected to a terminal that is provided at an
end portion of a flexible substrate that is electrically connected
to said electric circuit.
15-16. (canceled)
17. An ultrasonic probe as claimed in claim 1, wherein said
ultrasonic probe is mounted with an imaging device comprising an
objective optical system for forming an optical image of an
internal body part to investigate, and imaging elements for taking
said optical image to output image signals.
18-20. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an ultrasonic probe for
intra-cavity diagnosis having an ultrasonic transducer array, which
is inserted into body cavities to emit ultrasonic waves toward a
necessary internal body part and receive echo signals from the body
part, and a manufacturing method of the ultrasonic probe.
BACKGROUND ARTS
[0002] Medical diagnosis that utilizes ultrasound imaging has
recently been widely used in medical fields. The ultrasonic image
is obtained by emitting ultrasound from an ultrasonic probe toward
a necessary body part and detecting echo from the body part as
electric echo signals by use of an ultrasound observing device that
is connected to the ultrasonic probe through a connector. The
ultrasonic probes may be classified roughly into an intra-cavity
diagnostic type that is inserted in a body cavity, and an
extra-cavity diagnostic type that is moved on the body surface. As
a known driving methods for the intra-cavity diagnostic ultrasonic
probe, there is an electronic scanning method, wherein a plurality
of ultrasonic transducers are selectively driven to send and
receive the ultrasound, while being switched over by electronic
switches or the like.
[0003] The electronic scanning type ultrasonic probes may be
classified into a convex electronic scanning type and a radial
electronic scanning type. In the convex electronic scanning type,
the ultrasonic transducers, e.g. 94 to 128 transducers, are
arranged on a semi-cylindrical surface of a probe tip. In the
radial electronic scanning type, the ultrasonic transducers, e.g.
360, are arranged around a periphery of a probe tip.
[0004] In those types of ultrasonic probes using a plurality of
ultrasonic transducers, such as the convex electronic scanning type
and the radial electronic scanning type, it is necessary to provide
wiring cables for sending and receiving many kinds of signals,
including drive signals for exciting the individual transducers and
the echo signals, between the ultrasound observing device and an
electric circuit disposed in the ultrasonic probe. Therefore, the
cables take up a certain thickness in the ultrasonic probe, and
hinder making the ultrasonic probe finer, although it is desirable
to make the intra-cavity type probe as fine as possible in order to
ease the pain of the patient.
[0005] Since the available number of ultrasonic transducers to one
probe is limited by the permissible thickness of the wiring cable,
the resolving power of the ultrasonic image has also been limited.
Beside that, if the wiring cable has a large capacitance, the echo
signal will damp. Mismatching of electric impedance will lower the
S/N ratio, and may also cause cross-talk between the wires, which
can result in malfunction.
[0006] To solve the above problems, U.S. Pat. No. 4,917,097
suggests an ultrasonic transducer device wherein ultrasonic
transducers are integrated with amplifies for the echo signals
without using a wiring cable, and Japanese Laid-open Patent
Application No. 2000-298119 suggests an ultrasonic transducer
device wherein an electric circuit is mounted on a silicon
substrate that is integrated with ultrasonic transducers made of
composite piezoelectric elements, so as to make the wiring cables
unnecessary for connecting the electric circuit and the ultrasonic
transducers.
[0007] Recently, an ultrasonic transducer device using capacitive
micromachined ultrasonic transducers, which utilize micro
electromechanical system (MEMS), has been suggested, for example,
in U.S. Pat. No. 6,246,158 and Oralken et al, "Volmetric Ultrasound
Imaging Using 2-D CMUT Arrays", November 2003, IEEE TRANSACTION ON
ULTRASONIC, FERROELECTRICS, AND FREQUENCY CONTROL, VOL. 50, NO.
11.
[0008] However, according to the prior arts disclosed in the above
first and second materials, the amplifiers and the electric circuit
are arranged in a lateral direction of the ultrasonic transducer.
In that case, if the ultrasonic transducers are arranged to set
their lateral direction in alignment with an inserting direction of
the ultrasonic probe, the ultrasonic probe will have a relatively
large hard portion including the ultrasonic transducers, increasing
the load on the patient that may be caused by inserting the
ultrasonic probe into the living body.
[0009] Furthermore, since the first and second prior arts refer to
an example where the ultrasonic transducers are arranged in a
linear array, if the amplifiers and the electric circuit are
arranged laterally to the ultrasonic transducers, the wiring
between these elements and the ultrasonic transducers will be
complicated.
[0010] On the other hand, in the ultrasonic transducer device of
the first prior art, U.S. Pat. No. 6,246,158, an electric circuit
is disposed as a layer under the ultrasonic transducers. However,
there is no concrete description about how to connect the electric
circuit to wiring cables, how to arrange the ultrasonic transducers
or how many ultrasonic transducers are available. Among all, there
are not any suitable embodiments for the convex electronic scanning
type or the radial electronic scanning type.
SUMMARY OF THE INVENTION
[0011] In view of the foregoing, a primary object of the present
invention is to provide a diagnostic ultrasonic probe for use in
body cavities, which permits making the probe tip finer, and lessen
the above mentioned problems caused by the use of the wiring
cable.
[0012] Another object of the present invention is to provide a
method of manufacturing the inventive diagnostic ultrasonic probe
for use in body cavities.
[0013] To achieve the above and other objects, an ultrasonic probe
for intra-cavity diagnosis of the present invention comprises an
ultrasonic transducer array disposed at a tip of the probe, the
ultrasonic transducer array comprising a plurality of ultrasonic
transducers arranged in an array, and an electric circuit including
at least some of necessary electric elements for activating the
ultrasonic transducers, the electric circuit being formed as a
layer laid under the ultrasonic transducers.
[0014] The ultrasonic transducers may be piezoelectric elements. In
that case, the ultrasonic transducer array preferably has a layered
structure having at least a flexible substrate, the electric
circuit, a backing material, an array of the piezoelectric elements
and an acoustic impedance matching layer, which are formed atop
another on a rigid supporting member, wherein the electric circuit
and the piezoelectric elements are connected electrically through
wires which are disposed in the backing material. The flexible
substrate is preferably a circuit board having a circuit pattern
formed thereon.
[0015] The ultrasonic transducer may also be capacitive
micromachined ultrasonic transducers. In that case, the ultrasonic
transducer array has a layered structure having at least a flexible
substrate, the electric circuit and an array of the capacitive
micromachined ultrasonic transducers, which are formed atop another
on a rigid supporting member. It is more preferable to provide a
backing material between the supporting member and the flexible
substrate. The supporting member preferably has an ultrasound
absorbing function. The flexible substrate is a circuit board
having a circuit pattern formed thereon.
[0016] The electric circuit comprises at least one of amplifiers
for amplifying echo signals from the ultrasonic transducers,
switches for switching over between sending the echo signals from
the ultrasonic transducers and receiving drive signals for exciting
the ultrasonic transducers, a multiplexer for selective-switching
between the echo signals and/or between the drive signals, an A/D
converter for analog-to-digital conversion of the echo signals, and
a D/A converter for digital-to-analog conversion of the drive
signals.
[0017] According to a preferred embodiment, a wiring cable is
provided for connecting the electric circuit to an ultrasound
observing device that generates drive signals for exiting the
ultrasonic transducers and produces ultrasound images from echo
signals received from the ultrasonic transducers, the wiring cable
being connected to a terminal that is provided at an end portion of
a flexible substrate that is electrically connected to the electric
circuit.
[0018] Forming the electric circuit, including at least some of
necessary electric elements for the ultrasonic probe, as a layer
under the ultrasonic transducers permits reducing the thickness or
size of a hard portion, including the ultrasonic transducers, so
the load on the patient is relieved.
[0019] Including the amplifiers in the electric circuit prevents
the echo signals from suffering damping that is caused by
transmission loss in the wiring cable or from noise interference.
So the S/N ratio of the echo signal is improved. Including the
multiplexer in the electric circuit permits reducing the requisite
number of signal lines for the drive signals and the echo signals
to merely two, so it is possible to reduce the diameter of the
wiring cable. Including the A/D converter in the electric circuit
permits sending the echo signals as digital signals through the
wiring cable, so the echo signals will not damp in the wiring
cable. Including the D/A converter in the electric circuit permits
sending the drive signals as digital signals through the wiring
cable, so the drive signals will not damp in the wiring cable.
[0020] As for the convex electronic scanning type ultrasonic probe,
the wiring cable may be introduced at a base end portion of a
supporting member on which the ultrasonic transducer array is
mounted. In that case, it is preferable to incline the ultrasonic
transducer array to an introducing direction of the wiring cable
from the ultrasound observing device, such that the base end
portion of the supporting material faces the wiring cable. This
configuration facilitates introducing and connecting the wiring
cable to the electric circuit.
[0021] A method of manufacturing an ultrasonic probe for
intra-cavity diagnosis comprising an ultrasonic transducer array
disposed at a tip of the probe, the ultrasonic transducer array
comprising a plurality of ultrasonic transducers arranged in an
array, the method comprising steps of:
[0022] forming an electric circuit on a silicon substrate, the
electric circuit including at least some of electric elements for
activating the ultrasonic transducers;
[0023] forming the ultrasonic transducers as a layer on the
electric circuit as formed on the silicon substrate;
[0024] removing the silicon substrate while leaving the electric
circuit; and
[0025] affixing a flexible substrate to a back side of the electric
circuit after the silicon substrate is removed.
[0026] The silicon substrate is preferably an SOI substrate where
an insulator layer is sandwiched between two silicon layers, and
the electric circuit is formed in an upper one of the two silicon
layers, and a lower one of the two silicon layers is removed off
the insulator layer after the ultrasonic transducers are formed on
the electric circuit.
[0027] The capacitive micromachined ultrasonic transducers are
superior to the piezoelectric elements, because the capacitive
transducer can be formed integrally on an electric circuit, so the
wires can be arranged more smartly as compared to a case using the
piezoelectric elements. The capacitive transducer has a wider
ultrasonic frequency band than the piezoelectric element, so that
it can send and receive the ultrasonic waves of a wider variety of
frequencies, enabling ultrasonic diagnosis in a deeper range of the
living body. Besides that, the capacitive transducer generates less
heat energy than the piezoelectric element, and is superior in
efficiency of heat radiation to circumstances, as it can be formed
directly on a silicon substrate. Therefore, the capacitive
transducer is effective to suppress heat generation, which is one
of the most important subjects of the ultrasonic probe for
intra-cavity diagnosis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The above and other objects and advantages will be more
apparent from the following detailed description of the preferred
embodiments when read in connection with the accompanied drawings,
wherein like reference numerals designate like or corresponding
parts throughout the several views, and wherein:
[0029] FIG. 1 is an enlarged sectional view of a tip of an
ultrasonic probe according to an embodiment of the present
invention;
[0030] FIG. 2A is a top plan view of a linear ultrasonic transducer
array;
[0031] FIG. 2B is a top plan view of a two-dimensional ultrasonic
transducer array;
[0032] FIG. 3 is an enlarged sectional view of an ultrasonic
transducer array using piezoelectric elements;
[0033] FIG. 4 is a circuit diagram illustrating an embodiment
wherein amplifiers and switches are included in an electric
circuit;
[0034] FIG. 5 is a circuit diagram illustrating another embodiment
wherein amplifiers, switches and a multiplexer are included in an
electric circuit;
[0035] FIG. 6 is a circuit diagram illustrating a still another
embodiment wherein an amplifier, a switch and a multiplexer are
included in an electric circuit;
[0036] FIG. 7 is a circuit diagram illustrating a further
embodiment wherein an amplifier, a switch, a multiplexer and an A/D
converter are included in an electric circuit;
[0037] FIG. 8 is a circuit diagram illustrating an embodiment
wherein an amplifier, a switch, a multiplexer, an A/D converter and
a D/A converter are included in an electric circuit;
[0038] FIG. 9 is a circuit diagram illustrating another embodiment
wherein a multiplexer is included in an electric circuit, and is
connected individually to each row of an ultrasonic transducer
array;
[0039] FIG. 10 is a tip of an ultrasonic probe according to another
embodiment of the present invention;
[0040] FIG. 10A is a partially magnified sectional view of the tip
of the ultrasonic probe shown in FIG. 10;
[0041] FIG. 11 is an enlarged sectional view of an ultrasonic
transducer array using capacitive micromachined ultrasonic
transducers;
[0042] FIG. 12 is a top plan view illustrating an arrangement of
the capacitance transducer array;
[0043] FIG. 13 is an enlarged top plan view of the capacitance
transducer array;
[0044] FIG. 14 is an enlarged sectional view of the capacitance
transducer array;
[0045] FIGS. 15A to 15H are explanatory diagrams illustrating a
sequence of manufacturing the ultrasonic transducer array using the
capacitance transducer array;
[0046] FIG. 16 is an enlarged sectional view of an ultrasonic
transducer array using capacitance transducers, according to
another embodiment of the present invention;
[0047] FIG. 17 is a fragmentary sectional view of an ultrasonic
probe, with a radial electronic scanning type ultrasonic transducer
array using piezoelectric elements; and
[0048] FIG. 18 is a fragmentary sectional view of an ultrasonic
probe, with a radial electronic scanning type ultrasonic transducer
array using capacitive micromachined ultrasonic transducers.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] As shown in FIG. 1, a body cavity diagnostic ultrasonic
probe, hereinafter called simply the ultrasonic probe 2, has an
ultrasonic transducer array 10 at its tip 2a. The ultrasonic
transducer array 10 has an external diameter of about 5 mm to 8 mm,
and is of a convex type which is constituted of a number of
ultrasonic transducers 12 arranged in an array on a
semi-cylindrical supporting member 11. The ultrasonic transducers
12 are arranged in a linear array as shown in FIG. 2A or in a
two-dimensional array as shown in FIG. 2B.
[0050] The ultrasonic transducer array 10 is connected to a sheath
13 that has an external diameter of about 7 mm to 10 mm. An imaging
device 16 is mounted in an upper portion of the sheath 13. The
imaging device 16 is provided with an objective optical system 14
for forming an optical image of an internal body part to
investigate, and a CCD 15 for capturing the optical image as an
image signal. A channel 18 for putting a piercing needle 17 through
it is formed through a center portion 18 of the sheath 13. On
opposite sides of the piercing needle channel 18, an array wiring
cable 19 and an imaging device wiring cable 20 are conducted
through a lower portion of the sheath 13, so as to connect a
not-shown ultrasound observing device and the ultrasonic transducer
array 10 to the imaging device 16.
[0051] The supporting member 11 is made of a rigid material such as
stainless steel. The ultrasonic transducer array 10 is inclined to
an introducing direction D1 of the array wiring cable 19 from the
ultrasound observing device through the sheath 13, so as to face a
base end 11b of a back side 11a of the supporting material 11 to
the array wiring cable 19. At the base end portion 11b of the
supporting member 11, the array wiring cable 19 is inserted into
the supporting member 11. A not-shown through-hole is formed
through the supporting member 11, to conduct the array wiring cable
19 through it, and permit electric connection of the array wiring
cable 19 to a flexible circuit board 30 and an electric circuit 31,
as will be described with reference to FIG. 3.
[0052] In an embodiment shown in FIG. 3, the ultrasonic transducer
array 10 has a layered structure wherein the flexible circuit board
30 of 50 .mu.m to 1 mm thick, the electric circuit 31, a backing
material 32, a piezoelectric element array 33, an acoustic
impedance matching layer 34 and an acoustic lens 35 are formed atop
another on the supporting member 11. The electric circuit 31
usually consists of a single or a number of semiconductor chips,
and the acoustic lens 35 is 0.5 mm to 1.0 mm thick and has a radius
of curvature of 5 mm to 10 mm. The flexible substrate 30 is
provided with a not-shown circuit pattern, and is connected
electrically to the electric circuit 31. Although it is not shown
in detail, the flexible substrate 30 and the electric circuit 31
are electrically connected to the array wiring cable 19 that is
inserted into the supporting member 11 through the base end portion
11b.
[0053] As shown in FIGS. 4 to 9, the electric circuit 31 comprises
at least one of amplifiers 40 for amplifying echo signals from the
ultrasonic transducers 12, switches 41 for switching over between
sending the echo signals from the ultrasonic transducers 12 and
receiving drive signals for exciting the ultrasonic transducers 12,
a multiplexer 42 for selective-switching between the echo signals
as well as between the drive signals, an A/D converter 43 for
converting the echo signals from an analog form to a digital form,
and a D/A converter 44 for converting the drive signals from a
digital form to an analog form.
[0054] In an embodiment shown in FIG. 4, amplifiers 40 and switches
41 are included in the electric circuit 31, whereas other elements
are disposed in the not-shown ultrasound observing device. The
switches 41 are, for example, semiconductor switches such as
MOSFET, or electromechanical switches that switch their contacts
electromechanically, and switch over between sending the echo
signals and receiving the drive signals in accordance with
switching signals that are sent through the array wiring cable 19
from the ultrasound observing device.
[0055] The embodiment shown in FIG. 4 is effective particularly to
a case having a relatively small number of ultrasonic transducers
12, like those arranged in the linear array, and the array wiring
cable 19 may have a certainly large diameter. Besides, since the
amplifiers 40 are included in the electric circuit 31 in FIG. 4,
the signals do not suffer from damping or noise that may occur
because of transmission loss in the wiring cables. So the echo
signals are improved in S/N ratio. Furthermore, because the
switches 41 disconnect the signal lines for the drive signals from
ones for the echo signals, the amplifiers 40 can be driven at a low
voltage, which provides a special effect of saving the part cost
and the power consumption.
[0056] In an embodiment shown in FIG. 5, not only amplifiers 40 and
switches 41 but also a multiplexer 42 are included in the electric
circuit 31, and other elements are provided in the ultrasound
observing device. The multiplexer 42 selectively switches over
between the drive signals or between the echo signals in accordance
with a MP (multiplexer) control signal sent through the array
wiring cable 19 from the ultrasound observing device.
[0057] The embodiment of FIG. 5 is effective particularly to a case
having a large number of ultrasonic transducers 12, like those
arranged in the two-dimensional array, and the array wiring cable
19 may not be thick. This is because the multiplexer 42 permits
reducing the requisite number of signal lines for the drive signals
and the echo signals to merely two on the side of the array wiring
cable 19, so it is possible to reduce the diameter of the array
wiring cable 19. This embodiment is applicable to a case where the
number of ultrasonic transducers 12 is relatively small. In that
case, the array wiring cable 19 can be made still finer, relieve
the stress on the patients.
[0058] FIG. 6 shows another embodiment, wherein the electric
circuit 31 includes the same elements as in the embodiment of FIG.
5, but a switch 41 and an amplifier 40 are disposed on the output
side of a multiplexer 42. Because this embodiment needs only one
amplifier 40 and one switch 41, the parts cost, power consumption
and heat generation from the driven elements are reduced. Among
all, suppressing heat generation from the tip 2a of the ultrasonic
probe 2, a typical example of which is an ultrasonic endoscope, is
especially important.
[0059] In an embodiment shown in FIG. 7, an amplifier 40, a switch
41, a multiplexer 42 and an A/D converter 43 are included in the
electric circuit 31, and other elements are provided in the
ultrasound observing device. The A/D converter 43 converts the echo
signals from analog to digital form in accordance with an A/D
control signal sent through the array wiring cable 19 from the
ultrasound observing device. In this embodiment, the echo signals
are treated as digital signals on the side of the array wiring
cable 19, the echo signals will not damp in the array wiring cable
19.
[0060] In an embodiment shown in FIG. 8, an amplifier 40, a switch
41, a multiplexer 42 and an A/D converter 43 are included in the
electric circuit 31, and other elements are provided in the
ultrasound observing device. A D/A converter 44 converts the drive
signals from digital to analog form in accordance with a D/A
control signal sent through the array wiring cable 19 from the
ultrasound observing device. In this embodiment, the drive signals
are treated as digital signals on the side of the array wiring
cable 19, the drive signals will not damp in the array wiring cable
19. Furthermore, because the echo signals are also digitalized
through the A/D converter 43, it becomes possible to send the drive
signals and the echo signals in the same digital transmission
system using optical fibers.
[0061] In an embodiment shown in FIG. 9, a multiplexer 42 is
disposed on each row of an ultrasonic transducer array 10
consisting of N rows and M columns of ultrasonic transducers, and
the multiplexers 42 are included in the electric circuit 31. This
embodiment is especially effective to a case where there are a
large number of ultrasonic transducers 12, like in a
two-dimensional array, or where such a scanning sequence is adopted
that the ultrasonic transducers 12 are grouped into several blocks
so as to send and receive the drive signals and the echo signals
separately block by block. It is to be noted that other appropriate
circuits may be included in the electric circuit 31 in addition to
the multiplexer 42.
[0062] The present invention is not limited to the embodiments
shown in FIGS. 4 to 9, but there may be variations in the
combinations among the amplifiers 40, the switches 41, the
multiplexers 42, the A/D converter 43 and the D/A converter 44. For
example, the switches 41 may be omitted in some cases. Where the
influence of the noise is negligible, the amplifiers 40 as well as
the switches 41 are unnecessary. In order to suppress the noise and
reduce the influence of the noise, the signal lines for sending and
receiving the drive signals and the echo signals may be gathered
with an analog earth line to make a coaxial cable. It is also
possible to gather the digital signal lines for the switching
signals and the MP control signals and shield them with a digital
earth line. Furthermore, it is possible to insert a phase delay
circuit in the drive signal line on the side of the ultrasonic
transducer array 10. A coil or a filter circuit may be disposed for
impedance matching with the array wiring cable 19.
[0063] Referring back to FIG. 3, the backing material 32 is formed
with through-holes 36 that extend from the electric circuit 31 to
the piezoelectric element array 33. Wires 38 for connecting the
electric circuit 31 to the piezoelectric element array 33 are put
through the through-holes 36. Each wire 38 is soldered to a
terminal 37 on the electric circuit 31, and is connected to a pair
of electrodes which are not shown but sandwich the piezoelectric
element array 33. In order to save the part cost, it is possible
serve the backing material 32 as a flexible circuit board, and omit
the flexible circuit board 30.
[0064] The piezoelectric element array 33 consists of an array of
piezoelectric elements 33a arranged linearly or two-dimensionally,
and a filling material 33b filled in gaps between the piezoelectric
elements 33b. The acoustic impedance matching layer 34 is provided
for reducing a difference in acoustic impedance between the
piezoelectric elements 33a and the living body. The acoustic lens
35 is made of a silicon resin or the like, and converges ultrasound
toward the body part to observe, as the ultrasound is emitted from
the ultrasonic transducer array 10. The acoustic lens 35 may be
omitted, and a protective layer may be provided instead of the
acoustic lens 35.
[0065] To take an ultrasonic image of an internal part of a living
body, the ultrasonic probe 2 is inserted into the living body, to
search the aimed internal part, while observing on the ultrasound
observing device optical images as obtained through the imaging
device 16. When the tip 2a of the ultrasonic probe 2 reaches the
aimed internal part of the body, and a command to capture an
ultrasonic image is entered, the switches 41 are activated to
switch over sending and receiving of the ultrasonic waves from the
ultrasonic transducers 12. Simultaneously, the multiplexer 42
selectively switches between the drive signals and/or the echo
signals, as the ultrasonic waves are emitted from the ultrasonic
transducer array 10 toward the body part, and then reflected from
the body part. The reflected ultrasonic waves are received as the
echo signals on the ultrasonic transducer array 10. The echo
signals are converted through the ultrasound observing device into
an ultrasonic image, which is displayed on a monitor or the like.
While observing the optical image or the ultrasonic image, the
piercing needle 17 is manipulated to sample the aimed internal body
part.
[0066] As described so far, the electric circuit 31, including at
least some of necessary electric elements for the ultrasonic probe
2, is formed as a layer under the ultrasonic transducers 12, so
that the thickness or size of a hard portion, including the
ultrasonic transducers 12, is reduced, and thus the load on the
patient is relieved. Because the wires 38 that connect the
ultrasonic transducers 12 to the electric circuit 31 are put
through the through-holes 36 which are formed through the backing
material 32, the wires 38 are assembled neatly, saving the mounting
cost of the ultrasonic transducers 12.
[0067] Because the ultrasonic transducer array 10 is inclined to
the intruducing direction D1 of the array wiring cable 19 from the
ultrasound observing device, so as to face the base end portion 11b
of the back side 11a of the supporting material 11 to the array
wiring cable 19, the array wiring cable 19 is smoothly introduced
at the base end portion 11b into the supporting member 11, so that
it is easy to connect the array wiring cable 19 to the electric
circuit 31. This permits making the tip 2a of the ultrasonic probe
2 finer, thereby to lessen the disadvantage of using the wiring
cables.
[0068] The array wiring cable 19 may be connected to the electric
circuit 31 in a manner as shown in FIG. 10A, wherein layers 31 to
35 are formed on a flexible circuit board 30 so as to expose an end
portion 30a of the flexible circuit board 30, and a terminal 30b is
provided on the end portion 30a, so that the array wiring cable 19
is connected electrically to the terminal 30b. This embodiment is
also effective for smart wiring.
[0069] The present invention has been described with respect to the
ultrasonic transducer array 10 constituted of the ultrasonic
transducers 12 using the piezoelectric elements 33a, the present
invention is applicable to an ultrasonic probe using an ultrasonic
transducer array 50 as shown in FIGS. 11 to 14, wherein capacitive
micromachined transducers 51a are used as ultrasonic
transducers.
[0070] Because the capacitive micromachined transducer 51a,
hereinafter called simply the capacitive transducer 51a, can be
formed integrally on an electric circuit, the wiring can be
arranged more smartly as compared to a case using the piezoelectric
elements 33a. The capacitive transducer 51a has a wider ultrasonic
frequency band than the piezoelectric element 33a, so that it can
send and receive the ultrasonic waves of a wider variety of
frequencies, enabling ultrasonic diagnosis in a deeper range of the
living body. Besides that, the capacitive transducer 51a generates
less heat energy than the piezoelectric element 33a, and is
superior in efficiency of heat radiation to circumstances, as it
can be formed directly on a silicon substrate. Therefore, the
capacitive transducer 51a is effective to suppress heat generation,
which is one of the most important subjects of the ultrasonic probe
for body cavity diagnosis.
[0071] In FIG. 11, the ultrasonic transducer array 50 has a layered
structure wherein a backing material 32, a flexible circuit board
30, an electric circuit 31, a capacitive micromachined ultrasonic
transducer array 51, hereinafter called simply the capacitive
transducer array 51, and an acoustic lens 35 or a protective layer
are formed atop another on a substrate 11. The electric circuit 31
and the capacitive transducer array 51 have a thickness of 20 .mu.m
to 30.mu.m in total, whereas the ultrasonic transducer array 50 as
the whole has a thickness of 6 mm to 8 mm.
[0072] As shown in FIG. 12, the capacitive transducer array 51 is
sectioned into four segments 52 arranged in 2 rows and 2 columns.
Referring to FIGS. 13 and 14 showing an partially enlarged top
plane view and a sectional view of the capacitive transducer array
51, the capacitive transducer array 51 is constituted of an
insulating layer 60, e.g. SiO.sub.2, a bottom electrode 61, e.g.
Al, an insulating layer 62, e.g. SiNx, vacuum-sealed gaps 63, a
movable insulating layer 64, e.g. SiNx, a top electrode 65, e.g.
Al, and a protective insulating layer 66, e.g. SiO.sub.2. From the
bottom electrode 61 through the insulating layer 60, a terminal 61a
extends to connect the electrode 61 electrically to the electric
circuit 31. In FIGS. 13 and 14, a portion bounded by a chain-dotted
line constitutes the individual capacitance transducer 51a.
[0073] Now a method of manufacturing the ultrasonic transducer
array 50 will be concretely described with reference to FIG. 15.
First, an SOI (Silicon On Insulator) substrate 73 is provided by
forming a silicon layer 72 on an insulating layer 71 of a silicon
substrate 70, as shown in FIG. 15A. Then, the electric circuit 31
is formed of semiconductors in the silicon layer 72, as shown in
FIG. 15B.
[0074] Thereafter, the capacitive transducer array 51 is formed on
the electric circuit 31, as shown in FIG. 15C. Then, a temporary
supporting member 74 is bonded on the top of the capacitive
transducer array 51, as shown in FIG. 15D. Next, the silicon
substrate 70 is taken away by electrochemical etching or the like,
while leaving the insulating layer 71, as shown in FIG. 15E. After
the silicon substrate 70 is removed, the flexible circuit board 30
is put on a back side of the insulating layer 71, as shown in FIG.
15F, and then the temporary supporting member 74 is separated from
the capacitive transducer array 51, as shown in FIG. 15G.
[0075] Thereafter, as shown in FIG. 15H, the acoustic lens 35 or
the protective layer is joined onto the capacitive transducer array
51. Finally, a sheet having the layered structure of FIG. 15H is
put on the supporting member 11, and the wiring for connecting the
array wiring cable 19 and other cables is made to complete the
ultrasonic probe having the ultrasonic transducer array 50 at its
tip. In this way, the ultrasonic probe is manufactured with
ease.
[0076] It is to be noted that the ultrasonic transducer array 50
may be manufactured in another method insofar as it includes the
steps of forming the electric circuit 31 in the silicon substrate,
taking the silicon substrate away except but the electric circuit
31, and bonding a flexible substrate on the back side of the
electric circuit 31.
[0077] In place of the supporting member 11 that is made of a rigid
material, a supporting member 81 made of an ultrasonic wave
absorbing material may be used in an ultrasonic transducer array
80, as shown in FIG. 16. Then, the backing material 32 becomes
unnecessary, so it contributes to miniaturizing and economizing the
ultrasonic probe.
[0078] Although the ultrasonic transducer arrays 10, 50 and 80 of
the above embodiments have been described as a convex electronic
scanning type, the present invention is applicable to ultrasonic
probes using a radial electronic scanning type ultrasonic
transducer array, as shown for example in FIGS. 17 and 18. In the
radial electronic scanning type, a plurality of ultrasonic
transducers are arranged radially by forming respective layers in
concentric circles.
[0079] Specifically, an ultrasonic transducer array 91 of an
ultrasonic probe 90 shown in FIG. 17 uses a piezoelectric element
array 33, whereas an ultrasonic transducer array 101 of an
ultrasonic probe 100 shown in FIG. 18 uses a capacitive transducer
array 51. Although it is not shown in the drawings, an imaging
device 16 is mounted in a center portion of a supporting member 11
in each of the ultrasonic transducer arrays 91 and 101. Like the
embodiment shown in FIG. 10A, layers 31 to 35 are formed on a
flexible circuit board 30 so as to expose an end portion 30a of the
flexible circuit board 30, and a terminal 30b is provided on the
end portion 30a, so that an array wiring cable 19 is connected
electrically to the terminal 30b. Otherwise, the ultrasonic
transducer arrays 91 and 101 have the same fundamental structure as
the above-described convex electronic scanning type, except that
the ultrasonic transducers are arranged radially. Therefore, the
equivalent elements are designated by the same reference numerals
as used in the above embodiments, and the description of these
elements will be omitted.
[0080] The present invention is not to be limited to the above
embodiment but, on the contrary, various modifications will be
possible without departing from the scope of claims appended
hereto.
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