JP2012142880A - Ultrasonic vibrator, ultrasonic probe and ultrasonic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic vibrator having excellent electrical characteristics and acoustic characteristics, an ultrasonic probe equipped with the ultrasonic vibrator and ensuring production of a high resolution image, and an ultrasonic diagnostic apparatus equipped with the ultrasonic probe.SOLUTION: A plurality of layers of a monolithic piezoelectric material composed of a piezoelectric ceramic veneer and a composite piezoelectric material composed of a plurality of pillars of piezoelectric ceramic and a resin filling the gaps between the pillars are laminated alternately.

Description

  The present invention relates to an ultrasonic probe for acquiring an ultrasonic image by transmitting / receiving ultrasonic waves to / from a subject and an ultrasonic diagnostic apparatus including the ultrasonic probe.

  Ultrasound generally refers to sound waves of 16000 Hz or higher, and can be examined non-destructively, harmlessly and in substantially real time, and thus is applied to various fields such as defect inspection and disease diagnosis. For example, an ultrasound that scans the inside of the subject with ultrasound and images the internal state of the subject based on a reception signal generated from the reflected wave (echo) of the ultrasound coming from inside the subject. There is a diagnostic device. This ultrasonic diagnostic apparatus is smaller and less expensive for medical use than other medical imaging apparatuses, has no radiation exposure such as X-rays, is highly safe, and has a blood flow utilizing the Doppler effect. It has various features such as display capability. For this reason, an ultrasonic diagnostic apparatus includes a circulatory system (eg, coronary artery of the heart), a digestive system (eg, gastrointestinal), an internal system (eg, liver, pancreas, and spleen), and a urinary system (eg, kidney and bladder). Widely used in obstetrics and gynecology.

  An ultrasonic probe that transmits and receives ultrasonic waves to and from a subject is used in the ultrasonic diagnostic apparatus. An ultrasonic probe uses a piezoelectric phenomenon to generate an ultrasonic wave by mechanical vibration based on an electric signal transmitted, and receives an ultrasonic reflected wave caused by an acoustic impedance mismatch inside the subject. The plurality of piezoelectric elements (ultrasonic transducers) for generating received electrical signals are arranged, and the plurality of piezoelectric elements are arranged in an array, for example.

  Currently, ultrasonic probes arranged in only a one-dimensional direction are the mainstream, but an ultrasonic beam can be formed only in one plane with a one-dimensional array, so a beam is formed in an arbitrary direction. There is a need for a two-dimensional array of ultrasound probes that can be used.

  On the other hand, the frequency band of the ultrasonic probe is required to have a wide band in which a shorter ultrasonic pulse can be formed due to the demand in the time direction, that is, the distance resolution.

JP 2002-112397 A JP 2008-22266 A

  In order to obtain an ultrasonic probe in which the above-described plurality of piezoelectric elements are arranged in a 2D matrix array type, it is necessary to focus the ultrasonic beam not only in the conventional azimuth direction but also in the elevation direction. It is necessary to form a small-area vibrator by dividing a vibrator that has a rectangular parallelepiped shape into elements in the elevation direction.

  However, if the transducer area is small, the capacitance of the transducer decreases and the impedance increases, and it becomes impossible to obtain a received signal with a sufficient S / N ratio due to the stray capacitance of the transmission line and impedance mismatching. There was a problem.

  In order to solve this problem, a method such as incorporating a signal amplifier near the transducer of the probe is also used. However, since these cause new problems such as heat generation, these are used in the same manner as the conventional one-dimensional array type. There is a demand for a 2D matrix array type ultrasonic probe that can be used without any problems.

  As one of the methods, Patent Document 1 and Patent Document 2 disclose means for solving this problem by stacking piezoelectric materials. However, this is made of the same kind of piezoelectric material and obtains wide-band acoustic characteristics. However, there was a problem that good distance resolution could not be obtained.

  The present invention has been made in order to solve the above-described problems. An ultrasonic transducer excellent in not only electrical characteristics but also broadband acoustic characteristics, and an ultrasonic probe including the ultrasonic transducer are provided. It is an object of the present invention to provide a probe and an ultrasonic diagnostic apparatus including the ultrasonic probe.

  The above object is achieved by the invention described below.

1. An ultrasonic transducer that transmits or receives ultrasonic waves and can alternately convert electrical signals and ultrasonic waves,
Three layers of alternating layers of a monolithic piezoelectric material made of a piezoelectric ceramic single plate and a composite piezoelectric material layer comprising a plurality of pillar parts made of piezoelectric ceramic and a resin part filled with a gap between the pillar parts A layered stack, and
Electrodes provided on the interlayer and both ends of the laminate,
An ultrasonic vibrator, wherein electrodes on the separation side in layers of piezoelectric materials adjacent to each other are connected and connected.

  2. 2. The ultrasonic transducer according to item 1, wherein the layer made of the monolithic piezoelectric material and the layer made of the composite piezoelectric material can resonate.

  3. An ultrasonic probe comprising the ultrasonic transducer according to 1 or 2 above.

  4). 4. An ultrasonic probe comprising a plurality of the ultrasonic transducers according to claim 3 and a vibrating section that arranges the ultrasonic transducers one-dimensionally or two-dimensionally on the same plane. .

  5). An ultrasonic diagnostic apparatus comprising the ultrasonic probe according to 3 or 4 above.

  According to the present invention, a monolithic piezoelectric material layer made of a piezoelectric ceramic single plate and a composite piezoelectric material layer made up of a plurality of pillar portions made of piezoelectric ceramic and a resin portion filled with a gap between the pillar portions are alternately arranged. An ultrasonic transducer that is excellent in electrical characteristics and acoustic characteristics by forming multiple layers, an ultrasonic probe that includes an ultrasonic transducer and can obtain a high-resolution image, and the ultrasonic probe It is possible to obtain an ultrasonic diagnostic apparatus including

  In addition, by alternately laminating monolithic and composite materials, while taking advantage of the broadband properties of composite piezoelectric materials, it has stable characteristics without causing performance variations due to slight misalignment as in the case of laminating composite materials. An ultrasonic probe can be obtained.

1 is a schematic diagram showing an external configuration of an ultrasonic diagnostic apparatus. It is a block diagram which shows the electrical structure of an ultrasonic diagnosing device. 3 is a perspective view of a vibrating unit 40. FIG. It is a perspective view of the laminated vibrator 40a. It is sectional drawing of PZT composite 40a4. It is a figure showing the manufacturing method of PZT composite 40a4. It is a table | surface of the confirmation result of Examples 1-3. It is a graph of the check result of Examples 1 to 3.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments described below. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

  FIG. 1 is a schematic diagram illustrating an external configuration of an ultrasonic diagnostic apparatus according to an embodiment. FIG. 2 is a block diagram illustrating an electrical configuration of the ultrasonic diagnostic apparatus according to the embodiment.

  As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S transmits ultrasonic waves to a subject H such as a living body (not shown) and receives reflected ultrasonic waves reflected by the subject H. The ultrasonic probe 2 is connected to the ultrasonic probe 2 via the cable 3, and an ultrasonic probe is transmitted by transmitting a transmission signal of an electrical signal to the ultrasonic probe 2 via the cable 3. The child 2 transmits an ultrasonic wave to the subject H, and an electrical signal generated by the ultrasonic probe 2 in response to the reflected ultrasonic wave from the subject H received by the ultrasonic probe 2 And an ultrasonic diagnostic apparatus body 1 that images the internal state of the subject H as an ultrasonic image into a medical image based on the received signal.

  The ultrasonic diagnostic apparatus main body 1 is provided with an ultrasonic probe folder 4 for holding the ultrasonic probe 2 when the ultrasonic probe 2 is not used.

  For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, a reception signal processing unit 14, an image processing unit 15, and a display unit 16. , A control unit 17, a storage unit 19, and a transmission signal processing unit 18.

  The operation input unit 11 inputs data such as a command instructing the start of diagnosis and personal information of the subject H, for example, and is an operation panel or a keyboard provided with a plurality of input switches, for example.

  The transmission signal processing unit 18 is a circuit having a function of generating a transmission signal of an electrical signal that drives the vibration unit 40 under the control of the control unit 17. The vibration unit 40 has a plurality of ultrasonic transducers arranged two-dimensionally, and transmission signals are successively generated sequentially with a certain delay time in adjacent transducers.

  The transmission unit 12 amplifies the electrical signal generated by the transmission signal processing unit 18, supplies the transmission signal to the vibrating unit 40 in the ultrasonic probe 2 via the cable 3, and supplies the ultrasonic probe 2 to the ultrasonic probe 2. Generate ultrasound. The transmission unit 12 includes, for example, a high voltage pulse generator that generates a high voltage pulse.

  The receiving unit 13 is a circuit that receives a reception signal of an electrical signal from the vibration unit 40 in the ultrasonic probe 2 via the cable 3 according to the control of the control unit 17, and this reception signal is received by the reception signal processing unit 14. Output to. The receiving unit 13 includes, for example, an amplifier that amplifies the received signal with a predetermined amplification factor set in advance, an analog-digital converter that converts the received signal amplified by the amplifier from an analog signal to a digital signal, and the like. Configured.

  After the ultrasonic transducer of the vibration unit 40 oscillates the ultrasonic wave by the transmission signal from the transmission unit 12, the reflected wave is received by the adjacent transducer and the reception signal is output to the reception unit 13. This operation is sequentially executed for each row in a short time with respect to the ultrasonic transducers in which the vibration unit 40 is arranged, and the ultrasonic transducers can sequentially convert ultrasonic waves and electric signals.

  The reception signal processing unit 14 is a circuit that performs predetermined signal processing on the electrical signal from the reception unit 13 under the control of the control unit 17, and outputs the reflected reception signal subjected to the signal processing to the image processing unit 15.

  The image processing unit 15 generates an ultrasonic image of the internal state in the subject H using a harmonic imaging technique or the like based on the reflected reception signal processed by the reception signal processing unit 14 under the control of the control unit 17. Circuit. Further, for example, by performing envelope detection processing on the reflected reception signal, a B-mode signal corresponding to the amplitude intensity of the reflected ultrasonic wave is generated.

  The storage unit 19 includes a RAM and a ROM, and stores a program used for the control unit 17 and also records various image templates to be displayed on the display unit 16.

  The control unit 17 includes, for example, a microprocessor, a storage element, and peripheral circuits thereof. The operation input unit 11, the transmission unit 12, the reception unit 13, the reception signal processing unit 14, the image processing unit 15, a display unit, and the like. 16 is a circuit that performs overall control of the ultrasound diagnostic apparatus S by controlling the transmission signal processing unit 18 and the storage unit 19 in accordance with the function.

  The display unit 16 is a device that displays the ultrasonic image generated by the image processing unit 15 under the control of the control unit 17. The display unit 16 is, for example, a display device such as a CRT display, LCD, EL display, or plasma display, or a printing device such as a printer.

  From here on, a plurality of monolithic piezoelectric materials composed of a single plate of the piezoelectric ceramic of the present invention and composite piezoelectric materials composed of a plurality of pillar portions made of piezoelectric ceramic and a resin portion filled with a gap between the pillar portions are alternately arranged. A description will be given of a laminated ultrasonic transducer having electrodes laminated on and between the laminated layers and at both ends, and a probe using the laminated ultrasonic transducer.

  FIG. 3 is a perspective view of the vibration unit 40 in which the laminated vibrator 40a is two-dimensionally arranged on the same plane.

  On the backing layer 40a8, which is a support member, a plurality of stacked vibrators 40a are arranged in a matrix at regular intervals.

  The backing layer 40a8 is a flat plate member made of a material that absorbs ultrasonic waves, and absorbs ultrasonic waves radiated from the laminated vibrator 40a toward the backing layer 40a8.

  Although a 4 × 7 matrix is shown in the drawing, the present invention is not limited to this arrangement.

  FIG. 4 is a perspective view of the laminated vibrator 40a. From the top, second acoustic matching layer 40a1, first acoustic matching layer 40a2, first electrode 40a3, PZT composite 40a4, second electrode 40a6, PZT monolithic 40a5, first electrode 40a3, PZT composite 40a4, second electrode 40a6, reflection layer 40a7 is laminated. There may also be a protective layer (not shown).

  The PZT composite 40a4, which is a composite piezoelectric material, and the PZT monolithic 40a5, which is a monolithic piezoelectric material, have the same resonance frequency and can resonate with each other, whereby each electrode portion becomes a node portion or an abdomen portion of ultrasonic vibration. Large output can be obtained by taking advantage of the structure.

  If the difference in acoustic impedance Z (density x speed of sound) of the medium at the interface is large, the sound wave is reflected and the sound wave is not radiated. The first acoustic matching layer 40a2 is provided with an acoustic matching layer for changing the acoustic impedance to increase the sound wave transmittance. By adding tungsten to the resin (increasing density and sound speed), the acoustic impedance slightly closer to the piezoelectric material is obtained. The second acoustic matching layer 40a1 on the upper layer (living body side) is formed of only a resin, and is connected in a staircase pattern to a living body-oriented acoustic impedance.

  The first electrode 40a3 and the second electrode 40a6 have a structure in which they are alternately stacked in the thickness direction of the PZT composite 40a4 and the PZT monolithic 40a5 that are piezoelectric materials.

  The first electrode 40a3 is in contact with the upper surface of the PZT composite 40a4 that is the first layer of the piezoelectric material, and is in contact with the lower surface of the second layer PZT monolithic 40a5. Similarly, the second electrode 40a6 is in contact with the upper surface of the second-layer PZT monolithic 40a5 and in contact with the lower surface of the third-layer PZT composite 40a4.

  In this way, the structure has a structure in which electrodes are provided between the layers and both ends of the piezoelectric material stack, and the electrodes on the separation side are connected and connected in the stack of adjacent piezoelectric materials.

  The piezoelectric member upper member (matching layer is equivalent to this) and the lower member (backing layer is equivalent to this) have an acoustic impedance lower than that of the piezoelectric material, and the resonance mode of the piezoelectric material is λ / 2 resonance (both upper and lower parts are free ends) Vibration). Therefore, by providing a reflective layer 40a7, which is a tungsten carbide material having an acoustic impedance higher than that of the piezoelectric material, between the third PZT composite 40a4 and the backing layer 40a8, which is a piezoelectric material, the resonance mode is λ / 4 resonance ( In addition to becoming the upper free end and the lower fixed end), much of the energy of the sound wave that has been radiated to the backing side and absorbed by the backing layer and discharged as heat is radiated to the front surface. The strength (sensitivity) is approximately doubled.

  FIG. 5A is a horizontal cross-sectional view from the A direction shown in FIG. 4 of the PZT composite 40a4 provided in the first layer and the third layer. FIG. 5b is a vertical cross-sectional view.

  The PZT column portion 40a41 has a columnar shape, and a space in which each of the PZT column portions 40a41 is adjacent is filled with a resin portion 40a42 made of an epoxy resin, thereby forming a plate-like piezoelectric material.

  By stacking the piezoelectric parts in this manner, the capacitance can be secured, and the transmission between the probe (vibrator) and the diagnostic device causes the capacity to decrease due to the reduction in area of the 2D matrix array type piezoelectric part viewed from the subject. Problems that are easily affected by the stray capacitance can be avoided.

  FIG. 6 is a diagram showing an example of a manufacturing method of the PZT composite 40a4.

  As shown in FIG. 6, the PZT single plate 200 is temporarily bonded to the cutting substrate 100, and the cutting lines y 1, y 2, y 3 and cutting lines x 1, x 2 to x 5 are diced with a diamond cutter, etc. Fill and solidify. Thereafter, the temporarily bonded cutting substrate is removed to obtain the piezoelectric material of the PZT composite 40a4.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this.

Example 1
The second acoustic matching layer 40a1 is made of an epoxy resin and has a thickness of 180 μm, and the first acoustic matching layer 40a2 is a laminate of epoxy resin added with tungsten having a thickness of 120 μm. The piezoelectric material of the first layer and the third layer is a PZT composite in which the space factor, which is the ratio of the cross-sectional area of PZT to the entire cross-sectional area of the cross section shown in FIG. PZT monolithic with a space factor of 100% is laminated with a thickness of 280 μm. The reflective layer 40a7 is made of tungsten carbide, laminated with a thickness of 50 μm, and ferrite rubber (spinel ferrite mass 85%) is used for the backing layer as a support member.

(Example 2)
A PZT monolithic with a PZT space factor of 100% is used for the first and third layers of the piezoelectric material layer, and a PZT composite with a PZT space factor of 76% is used for the second layer of the piezoelectric material layer. The thickness of the piezoelectric material layer is the same as in Example 1.

  The materials and thicknesses of the second acoustic matching layer 40a1, the first acoustic matching layer 40a2, the reflective layer 40a7, and the backing layer are the same as those in the first embodiment.

(Example 3)
A PZT composite with a PZT space factor of 68% was used for the first and third layers of the piezoelectric material layer, and a PZT monolithic with a space factor of 100% was used for the second layer PZT. The thickness of the piezoelectric material layer is the same as in Examples 1 and 2.

  The materials and thicknesses of the second acoustic matching layer 40a1, the first acoustic matching layer 40a2, the reflective layer 40a7, and the backing layer are the same as those in the first and second embodiments.

  Hereinafter, the confirmation results of Examples 1 to 3 of the laminated ultrasonic transducer are shown in the table of FIG. 7 and the graph of FIG.

  For comparison and confirmation, PZT monolithic with a PZT space factor of 100% was used for the first, second, and third layers of the piezoelectric material layer. The thickness of the piezoelectric material layer is the same as in the example, and the materials and thicknesses of the second acoustic matching layer 40a1, the first acoustic matching layer 40a2, the reflective layer 40a7, and the backing layer are the same as in the example.

  As a measuring method, transmission / reception sensitivity was measured by reflection on a mirror surface iron plate.

  Although the maximum sensitivity was -48 dB in the comparative example, the sensitivity was increased by 3 dB in Examples 1 and 2, and the sensitivity was decreased by 1 dB in Example 3.

  Further, the peak values of the comparative example of FIG. 8 and the graphs of Examples 1 to 3 are expressed as fL (lower limit frequency), fH (upper limit frequency), and (fL + fH) / 2 in a frequency range of −6 dB or more. When the effective bandwidth is compared from the calculated fC (center frequency), 1.79 MHz (5.34 to 3.55) in Examples 1 and 3 and 1.53 MHz (5.22 to 3.69) in Example 2 are compared. ), Which is a wider band than the 1.37 MHz (5.12-3.75) of the comparative example.

  Similarly, the frequency bandwidth ratio BW (%) = (fH−fL) / fC × 100 is 40% in Examples 1 and 3 and 34% in Example 2 compared to 31% in the comparative example. Obtained.

  As described above, the laminated ultrasonic transducer in which the composite piezoelectric material and the monolithic piezoelectric material are alternately laminated is excellent in sensitivity and frequency band. In particular, the composite piezoelectric material having a PZT space factor of 76% is used in the first layer and the third layer. In addition, it was confirmed that the ultrasonic vibrator provided with the monolithic piezoelectric material in the second layer can greatly improve. The PZT space factor is not limited to 76%.

  Such a laminated ultrasonic transducer in which a composite piezoelectric material and a monolithic piezoelectric material are alternately laminated is excellent in electrical characteristics and acoustic characteristics. By providing a laminated ultrasonic transducer, a super-resolution image can be obtained. It is possible to obtain an ultrasonic probe and an ultrasonic diagnostic apparatus including the ultrasonic probe.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 3 Cable 4 Ultrasonic probe folder 11 Operation input part 12 Transmission part 13 Reception part 14 Reception signal processing part 15 Image processing part 16 Display part 17 Control part 18 Transmission signal processing part 19 Storage unit 40 Vibrating unit 40a Multilayer transducer 40a1 Second acoustic matching layer 40a2 First acoustic matching layer 40a3 First electrode 40a4 PZT composite 40a5 PZT monolithic 40a6 Second electrode 40a7 Reflective layer 40a8 Backing layer 40a41 PZT column part 40a42 Resin part H Subject S Ultrasonic diagnostic equipment

Claims (5)

An ultrasonic transducer that transmits or receives ultrasonic waves and can alternately convert electrical signals and ultrasonic waves,
Three layers of alternating layers of a monolithic piezoelectric material made of a piezoelectric ceramic single plate and a composite piezoelectric material layer comprising a plurality of pillar parts made of piezoelectric ceramic and a resin part filled with a gap between the pillar parts A layered stack, and
Electrodes provided on the interlayer and both ends of the laminate,
An ultrasonic vibrator, wherein electrodes on the separation side in layers of piezoelectric materials adjacent to each other are connected and connected.   2. The ultrasonic transducer according to claim 1, wherein the layer made of the monolithic piezoelectric material and the layer made of the composite piezoelectric material can resonate.   An ultrasonic probe comprising the ultrasonic transducer according to claim 1.   An ultrasonic probe comprising a plurality of the ultrasonic transducers according to claim 3, and comprising a vibrating section that arranges the ultrasonic transducers one-dimensionally or two-dimensionally on the same plane. Child.   An ultrasonic diagnostic apparatus comprising the ultrasonic probe according to claim 3.

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