JP2012205828A - Ultrasonic probe and ultrasonic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic probe using piezoelectric ceramics, in which the resonance ability of the organic piezoelectric material is not decreased, a harmonic wave can be received, and the band of a reception signal can be widened when organic piezoelectric materials are accumulated and used as an acoustic matching layer and also receive the harmonic wave.SOLUTION: The ultrasonic probe includes: a groove filling member for filling a gap of the inorganic piezoelectric material and a gap of the acoustic matching layer, the groove filling member being formed with an organic material that has an acoustic impedance lower than the organic piezoelectric material; and a common electrode formed on the organic piezoelectric material and an individual electrode arranged across the organic piezoelectric material with the common electrode. The individual electrode is arranged being divided into an arrangement direction of the inorganic piezoelectric material, and formed covering at least the groove filling member.

Description

  The present invention relates to an ultrasonic probe used for transmitting and receiving ultrasonic waves in an ultrasonic diagnostic apparatus and an ultrasonic diagnostic apparatus using the same.

  Conventionally, in the medical field, an ultrasonic diagnostic apparatus using an ultrasonic image has been put into practical use. In general, this type of ultrasonic diagnostic apparatus has an ultrasonic probe (ultrasonic probe) having a built-in transducer array, and an apparatus main body connected to the ultrasonic probe. Ultrasound images are transmitted by transmitting ultrasonic waves from the probe to the subject, receiving ultrasonic echoes from the subject with the ultrasonic probe, and processing the received signals electrically with the device body Is generated.

In an ultrasonic probe, as an ultrasonic transducer for transmitting and receiving ultrasonic waves, a vibrator in which electrodes are formed on both surfaces of a material (piezoelectric body) that exhibits a piezoelectric effect is generally used.
As the piezoelectric body, a piezoelectric ceramic represented by PZT (lead zirconate titanate), a polymer piezoelectric element represented by PVDF (polyvinylidene fluoride), or the like is used.
When a pulsed or continuous wave voltage is applied to the electrodes of such a vibrator, the piezoelectric body expands and contracts. By this expansion and contraction, pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and an ultrasonic beam is formed by combining the ultrasonic waves. The vibrator expands and contracts by receiving propagating ultrasonic waves and generates an electrical signal. This electric signal is used as an ultrasonic reception signal.

  Here, there is a large difference in acoustic impedance between the piezoelectric ceramic used for the ultrasound probe and the subject (living body), and the ultrasound beam is reflected at the interface between the transducer and the subject, causing vibration. The ultrasonic beam emitted from the child cannot be efficiently propagated into the subject. Therefore, in the ultrasonic probe, an acoustic matching layer having an acoustic impedance between the piezoelectric ceramic and the subject is laminated on the piezoelectric ceramic, and the acoustic impedance matching is performed, so that the ultrasonic beam at the boundary is obtained. In order to reduce the reflection of light.

In order to obtain a high-definition image in ultrasonic diagnosis, it is necessary to use high-frequency ultrasonic waves that can be measured with high spatial resolution. However, if a high frequency ultrasonic wave is used when measuring a deep part of the subject, the ultrasonic wave is attenuated, and sufficient reception sensitivity cannot be obtained. Therefore, in order to measure a deep part, it is necessary to use a low frequency ultrasonic wave, and a high-definition image cannot be obtained.
Therefore, it has been difficult to measure a good signal simultaneously from a shallow part and a deep part of the subject with a single probe. For this reason, a method is used in which a probe is used separately for a shallow part and a deep part of a subject to obtain respective images.

  When using different probes for shallow and deep parts of the subject, it is difficult to obtain images of the same part by placing these probes on the same position of the subject. If the subject is a living body, it is difficult to obtain the same image in time and the examination efficiency also deteriorates if the subject is a living body. was there.

For this reason, various methods have been proposed to widen the reception band of the transducer (broadband) in order to simultaneously measure a good signal from a shallow part and a deep part of the subject with a single probe.
The broadening of the probe leads to higher resolution by utilizing harmonic imaging techniques, but the sensitivity of the single transducer using piezoelectric ceramics decreases. End up.
Therefore, in a probe using piezoelectric ceramics, an organic piezoelectric body having an acoustic impedance lower than that of the piezoelectric ceramic is used as an acoustic matching layer laminated on the piezoelectric ceramic, and this organic piezoelectric body functions as an acoustic matching layer. At the same time, the reception signal band is widened by receiving harmonics.

For example, Patent Document 1 discloses an ultrasonic probe including a base having a concave surface, a composite film of a piezoelectric ceramic material and an organic piezoelectric material laminated on the concave surface, and an organic piezoelectric film laminated on the composite film. Is described.
Patent Document 2 discloses a first piezoelectric element array in which first piezoelectric elements (inorganic piezoelectric elements) having electrodes on both sides are two-dimensionally arranged, and a first piezoelectric element array that is stacked on the first piezoelectric element array. A second piezoelectric element (organic piezoelectric element) having a first electrode on a surface opposite to the one piezoelectric element array and a second electrode on the surface on the first piezoelectric element array side is two-dimensionally arranged. A sound having a piezoelectric element array and an acoustic separation part provided between the arranged first piezoelectric elements, connected to the second electrode through the acoustic separation part, and substantially equal to the acoustic impedance of the acoustic separation part An ultrasonic probe having a signal line made of a conductive member having impedance is described.

Japanese Patent Laid-Open No. 9-215094 JP 2010-136807 A

  As described above, when an organic piezoelectric body is laminated on a composite film of a piezoelectric ceramic and an organic piezoelectric body as in Patent Document 1, or an acoustic matching layer laminated on a piezoelectric ceramic as in Patent Document 2. When an organic piezoelectric body is laminated on the organic piezoelectric body, the organic piezoelectric body also functions as an acoustic matching layer. Therefore, the acoustic impedance of the layer below the organic piezoelectric body (the side opposite to the transmission / reception surface) is larger than the acoustic impedance of the organic piezoelectric body. However, if the acoustic impedance of the layer below the organic piezoelectric body is larger than the acoustic impedance of the organic piezoelectric body, the resonance ability of the organic piezoelectric body is reduced, leading to a reduction in sensitivity.

  An object of the present invention is to solve the above-described problems of the prior art. In an ultrasonic probe using piezoelectric ceramics, an organic piezoelectric material is laminated, and the organic piezoelectric material is used as an acoustic matching layer and a harmonic. Therefore, it is an object of the present invention to provide an ultrasonic probe that can receive harmonics without reducing the resonance ability of the organic piezoelectric material and can widen the band of the received signal.

  In order to achieve the above object, the present invention is similar to the inorganic piezoelectric material that is laminated on the inorganic piezoelectric material and the ceramic inorganic piezoelectric material that is one-dimensionally arranged with a gap. Organic having lower acoustic impedance than an organic piezoelectric body, which fills the arranged acoustic matching layer, the organic piezoelectric material stacked on the acoustic matching layer, and the gap between the inorganic piezoelectric material and the acoustic matching layer A groove filling member formed of a material; a common electrode formed on the organic piezoelectric body; and an individual electrode disposed with the organic piezoelectric body interposed between the common electrode and the individual electrode. An electrode is provided that is divided and arranged in the arrangement direction of the inorganic piezoelectric bodies, and is formed so as to cover at least the entire surface of the groove filling member.

Here, it is preferable that the groove filling member is obtained by dispersing fine particles having a density lower than that of the organic material in the organic material.
Moreover, it is preferable that the fine particles whose density is lower than that of the organic material is a glass balloon.
Moreover, it is preferable that the said organic material contains a silicone resin.
The organic piezoelectric body preferably covers the acoustic matching layer.

  In order to achieve the above object, the present invention provides a ceramics inorganic piezoelectric material arranged one-dimensionally with a gap, and the inorganic piezoelectric material laminated on the inorganic piezoelectric material. Similarly arranged acoustic matching layers, an organic piezoelectric body laminated on the acoustic matching layer, a common electrode formed on the organic piezoelectric body, and the organic piezoelectric body sandwiched with the common electrode The individual electrodes are divided and arranged in the arrangement direction of the inorganic piezoelectric bodies, and cover the gaps of the arranged acoustic matching layers. An ultrasonic probe is provided, which is characterized in that it is disposed in

Moreover, it is preferable to input a potential change generated by the organic piezoelectric body upon receiving an ultrasonic echo to the receiving amplifier without using a cable having a capacitance.
In order to achieve the above object, the present invention provides an ultrasonic diagnostic apparatus having the ultrasonic probe.

  According to the ultrasonic probe of the present invention having the above-described configuration, a ceramics inorganic piezoelectric material arranged with a gap, and an acoustic matching arranged on the inorganic piezoelectric material in the same manner as the inorganic piezoelectric material. An organic material that has an acoustic impedance lower than that of the organic piezoelectric body, and is formed of an organic material that fills the gap between the inorganic piezoelectric body and the acoustic matching layer. The groove filling member thus formed, a common electrode and an individual electrode sandwiching the organic piezoelectric material, and the individual electrodes on the acoustic matching layer side are divided and arranged in the arrangement direction of the inorganic piezoelectric material, and at least the groove Since it is formed so as to cover the filling member, even when the organic piezoelectric body receives harmonics, harmonics can be received without lowering the resonance capacity of the organic piezoelectric body, and the received signal Can be widened.

It is a figure which shows notionally an example of the ultrasound diagnosing device using the ultrasound probe of this invention. It is a block diagram which shows the structure of the ultrasonic diagnosing device shown in FIG. It is a perspective view which shows typically the internal structure of the ultrasonic probe of this invention. (A) is the front view which expanded a part of ultrasonic probe shown in FIG. 3, (B) is the top view of the ultrasonic probe shown in FIG. It is the schematic which expands and shows a part of other example of an ultrasonic probe. (A)-(C) are schematic which shows the structure of the element for an experiment. (A) is a graph which shows the relationship between a frequency and an electrical impedance, (B) is a graph which shows the relationship between a frequency and a phase. (A) is a graph which shows the relationship between a frequency and an electrical impedance, (B) is a graph which shows the relationship between a frequency and a phase.

  Hereinafter, the ultrasonic probe of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a diagram conceptually showing an example of an ultrasonic diagnostic apparatus using the ultrasonic probe of the present invention, and FIG. 2 is a block conceptually showing the configuration of the ultrasonic diagnostic apparatus 40 shown in FIG. FIG.
In the illustrated ultrasonic diagnostic apparatus 40, the individual electrodes on the acoustic matching layer side of the pair of electrodes arranged with the organic piezoelectric material interposed therebetween are formed in the gap of the inorganic piezoelectric material and the gap of the acoustic matching layer. This is basically a known ultrasonic diagnostic apparatus except that it has an ultrasonic probe formed so as to cover the groove filling member.
The ultrasonic diagnostic apparatus 40 includes a probe main body 42 having the ultrasonic probe 10 and a diagnostic apparatus main body 46 to which the probe main body 42 is connected via a communication cable 44.

The probe main body 42 includes an ultrasonic probe 10, a plurality of first reception signal processing units 48 connected to the plurality of first electrodes 24 of the ultrasonic probe 10, respectively, and an ultrasonic probe. A plurality of second reception signal processing units 50 connected to each of the plurality of individual electrodes 28, a transmission driving unit 52 connected to the first electrode 24, a first reception signal processing unit 48, a second A probe control unit that controls the reception signal processing unit 50 and the transmission drive unit 52;
The first received signal processing unit 48 is in the first data storage unit 56 of the diagnostic device main body 46, the second received signal processing unit 50 is in the second data storage unit 58, the probe control unit 54 is in the main body control unit 64, Each is connected via a communication cable 44.

  3 is a perspective view schematically showing the internal structure of the ultrasonic probe 10, and FIG. 4A is a front view in which a part of the ultrasonic probe 10 shown in FIG. 3 is enlarged. 4B is a top view of the ultrasonic probe 10 shown in FIG. In FIG. 4B, in order to show the internal structure of the ultrasound probe 10, the acoustic lens 20 and the common electrode 30 are not shown in the region indicated by a, and in the region indicated by b, The illustration of the organic piezoelectric body 18 and the individual electrode 28 is omitted. The ultrasonic probe 10 is used when performing extracorporeal scanning while abutting on the subject, or when inserting into the body cavity of the subject and performing intracorporeal scanning.

  The ultrasonic probe 10 shown in FIG. 3 includes a backing material 12, a plurality of inorganic piezoelectric bodies 14 arranged and stacked on the backing material 12, and an acoustic matching layer 16 stacked on the inorganic piezoelectric body 14. A groove filling member 22 filled in the gap between the inorganic piezoelectric body 14 and the acoustic matching layer 16, an organic piezoelectric body 18 stacked on the acoustic matching layer 16 and the groove filling member 22, and an organic piezoelectric body 18 An acoustic lens 20 stacked on top of each other, a first electrode 24 and a second electrode 26 constituting an electrode pair disposed with the inorganic piezoelectric member 14 interposed therebetween, and an electrode pair disposed with the organic piezoelectric member 18 interposed therebetween. It has the individual electrode 28 and the common electrode 30 which comprise.

  The backing material 12 is formed of a material having a large acoustic attenuation, such as an epoxy resin containing ferrite powder, metal powder, PZT powder, or rubber containing ferrite powder, and is not required to be generated from the inorganic piezoelectric body 14. It accelerates the attenuation of ultrasonic waves.

  The inorganic piezoelectric body 14 is made of an inorganic piezoelectric material such as ceramics, generates ultrasonic waves based on a drive signal supplied from the diagnostic apparatus main body 44, and receives ultrasonic echoes propagating from the subject. An electric signal corresponding to the intensity of the received ultrasonic echo is generated. A plurality of inorganic piezoelectric bodies 14 are arranged one-dimensionally with a gap in the azimuth direction (X direction in the figure) and stacked on the backing material 12. The ratio of the length of the inorganic piezoelectric body 14 in the azimuth direction to the length of the gap is about 3: 1.

A piezoelectric ceramic is used as the material of the inorganic piezoelectric body 14. Piezoelectric ceramics have a high electrical / mechanical energy conversion capability, and therefore can generate powerful ultrasonic waves that can reach the deep part of the body and have high reception sensitivity. Specific examples of the material include PZT (lead zirconate titanate: Pb (Ti, Zr) O3), a modified composition material having a similar perovskite crystal structure, and a material generally referred to as a relaxor material. Can be used.
When PZT is used as the inorganic piezoelectric body 14, the acoustic impedance of the inorganic piezoelectric body 14 is 30 to 34 Mrayl.

  A first electrode 24 and a second electrode 26 are formed on the surface of the inorganic piezoelectric body 14 on the backing material 12 side and the surface facing the surface, respectively. The inorganic piezoelectric element 14 and the first electrode 24 and the second electrode 26 form an inorganic piezoelectric element. In the illustrated example, the first electrode 24 is switchably connected to a transmission drive unit 52 and a first reception signal processing unit 48, and the second electrode is grounded. The first electrode 24 and the second electrode 26 form a pair of electrodes, and when transmitting an ultrasonic wave, the first electrode 24 is connected to the transmission drive unit 52 and an ultrasonic transmission signal is supplied. Further, at the time of reception of ultrasonic waves, the first electrode 24 is connected to the reception signal processing unit 48, and an electrical signal generated by the inorganic piezoelectric body 14 receiving ultrasonic echoes is acquired and supplied to the reception signal processing unit 48. To do.

The acoustic matching layer 16 is a member for matching acoustic impedance between the inorganic piezoelectric body 14 and the organic piezoelectric body 18, and a gap is formed on the inorganic piezoelectric body 14 in the same manner as the inorganic piezoelectric body 14. A plurality of them are arranged and stacked. The acoustic matching layer 16 has an acoustic impedance between the inorganic piezoelectric body 14 and an organic piezoelectric body 18 described later.
As the material of the acoustic matching layer 16, various known materials that can achieve acoustic impedance matching between the inorganic piezoelectric body 14 and the organic piezoelectric body 18 can be used.

The groove filling member 22 is formed in the gap between the inorganic piezoelectric bodies 14 and the gap between the acoustic matching layers 16 so that sound propagates between the plurality of inorganic piezoelectric bodies 14 and does not interfere with each other. Is for separating. The groove filling member 22 has a lower acoustic impedance than the inorganic piezoelectric body 14 and the acoustic matching layer 16 in order to separate the propagation of sound between the individual inorganic piezoelectric bodies 14.
Further, the groove filling member 22 is formed below the individual electrode 28 formed on the lower surface of the organic piezoelectric body 18 to be described later, has a lower acoustic impedance than the organic piezoelectric body 18, and has a backing against the organic piezoelectric body 18. It also has a function as a material. This will be described in detail later.

As the material of the groove filling member 22, various known materials that can have an acoustic impedance lower than that of the organic piezoelectric body 18 can be used. For example, a resin such as a silicone resin or a urethane resin can be used.
Moreover, it is preferable to disperse fine particles having a lower density than the resin, such as a glass balloon, in the resin. The acoustic impedance can be further reduced by dispersing fine particles having a low density in the resin.

The organic piezoelectric body 18 is adapted to match the acoustic impedance between the acoustic matching layer 16 and the acoustic lens 20 and generate an electrical signal by receiving harmonics of an ultrasonic echo propagating from the subject. . The organic piezoelectric body 18 is laminated on the acoustic matching layer 16.
An organic piezoelectric material such as PVDF (polyvinylidene fluoride) is used as the material of the organic piezoelectric body 18. Further, the acoustic impedance of the organic piezoelectric body 18 is smaller than that of the acoustic matching layer 16 and larger than that of the groove filling member 22 and the acoustic lens 20. When PVDF is used as the organic piezoelectric body 18, the acoustic impedance of the organic piezoelectric body 18 is 3 to 4 Mrayl.

  The organic piezoelectric body 18 functions as an acoustic matching layer that matches the acoustic impedance between the acoustic matching layer 16 and the acoustic lens 20 by having an acoustic impedance larger than that of the acoustic matching layer 16 and smaller than that of the acoustic lens 20. To do.

  In addition, the organic piezoelectric member 18 functions as an element that receives harmonics of ultrasonic echoes that propagate from the subject when generating an ultrasonic image using the harmonic imaging technique. Therefore, the individual electrode 28 is formed on the surface of the organic piezoelectric body 18 on the acoustic matching layer 16 side, and the common electrode 30 is formed on the opposite surface. As shown in FIGS. 4A and 4B, a plurality of individual electrodes 28 are arranged one-dimensionally with a gap in the X direction, and each individual electrode 28 has a corresponding groove filling member 22. Are arranged so as to cover the entire surface and a part of the acoustic matching layer 16. On the other hand, the common electrode 30 is uniformly formed over the entire organic piezoelectric body 18. Each individual electrode 28 is connected to the reception signal processing unit 48, and the common electrode 30 is grounded. At the time of reception of ultrasonic waves, the individual electrode 28 acquires an electrical signal generated when the organic piezoelectric body 18 receives harmonics of the ultrasonic echo, and supplies the electrical signal to the reception signal processing unit 48.

  Since the organic piezoelectric body 18 made of an organic piezoelectric material such as PVDF has small vibration coupling in the lateral direction (X direction) and does not easily propagate sound, the portion where the individual electrode 28 is disposed receives an ultrasonic echo. Functions as an element. Therefore, by arranging a plurality of individual electrodes 28 with a gap, the organic piezoelectric body 18 can be separated as a plurality of elements, and the organic piezoelectric body 18 and the individual electrodes 28 in the region where the individual electrodes 28 are disposed. And the common electrode 30 form an organic piezoelectric element.

As described above, the ultrasonic probe of the present invention has the ceramic inorganic piezoelectric element 14 arranged with a gap and the acoustics arranged on the inorganic piezoelectric element 14 in the same manner as the inorganic piezoelectric element 14. An organic material having a lower acoustic impedance than the organic piezoelectric body 18 filling the gap between the matching layer 16, the organic piezoelectric body 18 laminated on the acoustic matching layer 16, and the gap between the inorganic piezoelectric body 14 and the acoustic matching layer 16. And the common electrode 30 and the individual electrode 28 sandwiching the organic piezoelectric material 18, and the individual electrode 28 on the acoustic matching layer 16 side is divided in the arrangement direction of the inorganic piezoelectric material 14. Since it is arranged and is formed so as to cover at least the groove filling member 22, the ultrasonic probe 10 has a configuration in which an organic piezoelectric body 18 is laminated in addition to the ceramic inorganic piezoelectric body 14. Body 14 is examined Even when measuring the deep part of the subject by transmitting the ultrasonic beam to the organic piezoelectric element 18 and receiving the harmonics of the ultrasonic echo, the ultrasonic wave is not attenuated and the measurement is performed with high spatial resolution. And a high-definition image can be obtained.
At this time, by disposing the individual electrode 28 on the groove filling member 22, the lower layer of the organic piezoelectric body 18 as an organic piezoelectric element that receives the harmonics of the ultrasonic echo has an acoustic impedance higher than that of the organic piezoelectric body 18. Since the groove filling member 22 is low, the groove filling member 22 functions as a backing material for the organic piezoelectric body 18 and can prevent the resonance ability of the organic piezoelectric body 18 from being lowered, thereby reducing the sensitivity of the organic piezoelectric element. Can receive high harmonics of ultrasonic echoes with high sensitivity, and can widen the bandwidth of the received signal, thereby obtaining a high-definition image even when measuring deep parts Can do. Further, it is not necessary to use different ultrasonic probes for the shallow and deep portions of the subject.

Here, in the illustrated example, the individual electrode 28 is disposed so as to cover the entire surface of the groove filling member 22 and a part of the acoustic matching layer 16, but the present invention is not limited to this, and the individual electrode 28 The individual electrode 28 may be formed so that 28 covers only the groove filling member 22. That is, in the present invention, the groove filling member 22 is formed in the gap between the inorganic piezoelectric bodies 14 and the gap between the acoustic matching layers 16, and the individual electrodes 28 are arranged so as to cover the entire upper surface of the groove filling member 22. Various configurations are available.
Note that the larger the size of the individual electrode 28, the more preferable the capacitance is. However, the larger the portion covering the acoustic matching layer 16, the larger the acoustic impedance of the lower layer of the individual electrode 28, and the organic piezoelectric body 18. There is a possibility that the resonance ability is lowered. Therefore, the size of the individual electrode 28 may be appropriately determined according to the configuration of the ultrasonic probe 10, required performance, and the like.

  In the illustrated example, the organic piezoelectric body 18 is integrally formed so as to cover the entire surface of the acoustic matching layer 16, and only the individual electrodes 28 are separated and arranged. However, the present invention is not limited to this. The organic piezoelectric bodies may be arranged one-dimensionally with a gap in the X direction.

FIG. 5 shows an example of the ultrasonic probe of the present invention in which a plurality of organic piezoelectric bodies are arranged one-dimensionally with gaps in the X direction.
The ultrasonic probe 100 shown in FIG. 5 is the same as the ultrasonic probe 10 shown in FIG. 4 except that it has an organic piezoelectric body 102 and a second groove filling member 104 instead of the organic piezoelectric body 18. Since they have the same configuration, the same parts are denoted by the same reference numerals, and different parts will be mainly described below.

  The ultrasonic probe 100 includes a backing material 12, a plurality of inorganic piezoelectric bodies 14 arranged and stacked on the backing material 12, an acoustic matching layer 16 stacked on the inorganic piezoelectric body 14, and an inorganic piezoelectric element. The groove filling member 22 filled in the gap between the body 14 and the acoustic matching layer 16, the organic piezoelectric body 102 stacked on the acoustic matching layer 16 and the groove filling member 22, and the gap between the organic piezoelectric bodies 102 are filled The second groove filling member 104 to be formed, the first electrode 24 and the second electrode 26 constituting the electrode pair disposed with the inorganic piezoelectric member 14 interposed therebetween, and the electrode pair disposed with the organic piezoelectric member 18 interposed therebetween. The individual electrode 28 and the common electrode 30 are provided. Although not shown, the acoustic lens 20 is laminated on the organic piezoelectric body 102 as in the case of the ultrasonic probe 10.

The organic piezoelectric body 102 is adapted to match the acoustic impedance between the acoustic matching layer 16 and the acoustic lens 20 and generate an electrical signal by receiving harmonics of an ultrasonic echo propagating from the subject. . A plurality of organic piezoelectric bodies 102 are arranged one-dimensionally with a gap in the azimuth direction (X direction) and stacked on the acoustic matching layer 16 and the groove filling member 22. Here, the organic piezoelectric body 102 is disposed so that the individual electrode 28 formed on the surface of the organic piezoelectric body 102 on the acoustic matching layer 16 side covers the entire surface of the groove filling member 22 and a part of the acoustic matching layer 16. ing.
At the time of reception of ultrasonic waves, an electrical signal generated by the organic piezoelectric body 102 receiving harmonics of ultrasonic echoes is supplied to the reception signal processing unit 48 via the individual electrodes 28.

  The second groove filling member 104 is formed in the gap between the organic piezoelectric bodies 102 and separates the individual organic piezoelectric bodies 102. The second groove filling member 104 preferably has a lower acoustic impedance than the organic piezoelectric body 102 in order to separate the propagation of sound between the individual organic piezoelectric bodies 102. As a material of the groove filling member 104, for example, a resin such as a silicone resin or a urethane resin can be used.

  As described above, even when the organic piezoelectric body 102 is formed separately, the individual electrodes 28 formed on the acoustic matching layer 16 side of the organic piezoelectric body 102 are arranged so as to cover the entire surface of the groove filling member 22. The lower layer of the organic piezoelectric body 102 as an element for receiving ultrasonic echoes becomes the groove filling member 22 having an acoustic impedance lower than that of the organic piezoelectric body 102, and the groove filling member 22 functions as a backing material for the organic piezoelectric body 102. Further, it is possible to prevent the resonance ability of the organic piezoelectric body 102 from being lowered, receive harmonics without lowering the sensitivity, and widen the band of the received signal.

  The acoustic lens 20 is formed of, for example, silicone rubber, and focuses an ultrasonic beam transmitted from the inorganic piezoelectric body 14 and propagated through the acoustic matching layer 16 and the organic piezoelectric body 18 at a predetermined depth in the subject. .

  The transmission drive unit 52 includes, for example, a plurality of pulsers, and based on the transmission delay pattern selected by the probe control unit 54, the ultrasonic waves transmitted from the ultrasonic probe 10 are transmitted to the tissue in the subject. The delay amount of each drive signal is adjusted so as to form a wide ultrasonic beam covering the area, and supplied to the plurality of first electrodes 24.

The reception signal processing unit 48 receives a reception signal output from the first electrode 24 when taking a normal ultrasonic image under the control of the probe control unit 54 in accordance with an instruction from the main body control unit 64. When an ultrasonic image is acquired by the harmonic imaging technique, a reception signal output from the individual electrode 28 is acquired.
The reception signal processing unit 48 of each channel generates a complex baseband signal by subjecting the reception signal output from the corresponding first electrode 24 or individual electrode 28 to orthogonal detection processing or orthogonal sampling processing, thereby generating a complex baseband signal. By sampling the band signal, sample data including information on the area of the tissue is generated. The reception signal processing unit 48 may generate sample data by performing data compression processing for high-efficiency encoding on data obtained by sampling a complex baseband signal.

The probe control unit 54 controls each part of the probe main body 42 based on various control signals transmitted from the diagnostic apparatus main body 46.
Here, based on the control signal supplied from the main body control unit 64, the probe control unit 54 receives the reception signal from the first electrode 24 when the reception signal processing unit 48 captures a normal ultrasonic image. The reception signal processing unit 48 is controlled to acquire the received signal processing so that the reception signal processing unit 48 acquires the reception signal from the individual electrode 28 in the case of imaging an ultrasonic image by the harmonic imaging technique. The unit 48 is controlled.

Next, the diagnostic device main body 46 will be described.
The diagnostic device main body 46 sends an ultrasonic transmission instruction signal to the probe main body 42 connected via the communication cable 44 and based on the ultrasonic reception data (sample data) transmitted from the probe main body 42. An ultrasonic image is generated and displayed.
In addition, as the communication cable 44, it is preferable to use a cable having no (small) capacitance. Since the organic piezoelectric body 18 has a small electrostatic capacity, if the electrostatic capacity of the cable is large, the received voltage decreases and the sensitivity decreases. On the other hand, signal sensitivity is greatly improved by using a cable having no capacitance.

  The diagnostic apparatus main body 46 has a data storage unit 56, and an image processing unit 60 is connected to the data storage unit 56. Further, a display unit 62 is connected to the image processing unit 60. A main body control unit 64 is connected to the image processing unit 60 and the display unit 62. Furthermore, an operation unit 66 for an operator to perform an input operation is connected to the main body control unit 64.

The operation unit 66 is a part that sets an imaging menu, imaging conditions, and the like and instructs imaging of the subject. The operation unit 66 is provided with input means such as an input key for setting a shooting menu, shooting conditions, and the like, a dial button, a trackball, and a touch panel.
In the present invention, the operation unit 66 is for performing an input for instructing either generation of a normal ultrasonic image or generation of an ultrasonic image using a harmonic imaging technique.

  The data storage unit 56 includes a memory, a hard disk, or the like, and stores at least one frame of sample data transmitted from the probe main body 42 via the communication cable 44.

  The image generation unit 60 performs necessary image processing such as reception focus processing on the sample data for each frame read from the data storage unit 56 to generate an image signal representing an ultrasound diagnostic image. The image generation unit 60 supplies the generated image signal to the display unit 62.

The display unit 62 includes, for example, a display device such as an LCD, and displays an ultrasound diagnostic image under the instruction of the main body control unit 64 based on the image signal generated by the image generation unit 60.
The main body control unit 64 controls each unit in the diagnostic apparatus main body 46. The main body control unit 64 is connected to the probe main body 42 via the communication cable 44 and supplies a control signal for controlling the operation of the probe main body 42.
Here, when generation of an ultrasonic image by the harmonic imaging technique is instructed by an input instruction, a signal to that effect is supplied to the probe control unit 54.

Next, the operation of the ultrasonic diagnostic apparatus 40 will be described.
First, the operator inputs to the operation unit 66 whether to pick up a normal ultrasonic image or an ultrasonic image by a harmonic imaging technique, and abuts the probe body 42 on the surface of the subject. In this state, an ultrasonic wave is transmitted from the inorganic piezoelectric body 14 according to a drive signal supplied from the transmission drive unit 52 of the probe main body 42, and is output from the ultrasonic probe 10 that has received an ultrasonic echo from the subject. The received signal is supplied to the received signal processing unit 48 to generate sample data, which is transmitted to the diagnostic apparatus main body 46 via the communication cable 44 and stored in the data storage unit 56. At this time, in the case of normal ultrasound image capturing, the reception signal processing unit 48 acquires the reception signal output from the first electrode 24 (inorganic piezoelectric body 14), and captures the ultrasound image by the harmonic imaging technique. In this case, the reception signal processing unit 48 acquires the reception signal output from the individual electrode 28 (organic piezoelectric body 18), and generates sample data. Sample data for each frame is read from the data storage unit 56, an image signal is generated by the image generation unit 60, and an ultrasound diagnostic image is displayed on the display unit 62 based on this image signal.

  Here, in the illustrated ultrasonic probe 10, the gap filling member 22 formed of an organic material having an acoustic impedance lower than that of the organic piezoelectric body 18 is formed in the gap of the inorganic piezoelectric body 14 and the gap of the acoustic matching layer 16. However, the present invention is not limited to this, and the air is interposed in the gap between the inorganic piezoelectric body 14 and the gap between the acoustic matching layers 16 without arranging the groove filling member 22. Also good. That is, by using air as the backing material of the organic piezoelectric body (individual electrode), it is possible to prevent the resonance ability of the organic piezoelectric body from further decreasing, and thus it is possible to prevent the sensitivity of the organic piezoelectric element from decreasing. Accordingly, it is possible to receive the harmonics of the ultrasonic echo with high sensitivity, and to widen the band of the received signal, thereby obtaining a high-definition image even when measuring a deep part. .

Reference example

Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.
In this reference example, an element for element experiment was created and measured, and a model corresponding to the element experiment element was created for simulation.

[Reference Example 1]
FIG. 6A shows a schematic diagram of the created element experimental element 200.
The element experiment element 200 includes a base 202, an intermediate layer 204, and an organic piezoelectric element 206.

The base 202 is a substantially rectangular plate-shaped member, made of glass epoxy, and has an acoustic impedance of 6.9 Mrayl.
The intermediate layer 204 is a member disposed on one surface of the base 202, and the material is silicone, the width is 20 mm, the length is 20 mm, the thickness is 500 μm, and the acoustic impedance is 1.2 Mrayl.
The organic piezoelectric element 206 is a plate-like member disposed on the surface of the intermediate layer 204 opposite to the base 202, and electrodes are formed on both surfaces of the organic piezoelectric body. The organic piezoelectric body is PVDF, the width is 20 mm, the length is 20 mm, the thickness is 240 μm, and the acoustic impedance is 4.0 Mrayl.

In addition, a Φ30 mm PZT probe was used as a probe for transmitting ultrasonic waves to the element experiment element 200. The center frequency of the ultrasonic wave transmitted by the PZT probe was 3.5 MHz.
Water is interposed between the element experimental element 200 and the PZT probe, ultrasonic waves are transmitted from the PZT probe, ultrasonic waves are received by the element experimental element 200, and an impedance analyzer. Using 4294A (manufactured by Agilent), the relationship between frequency, electrical impedance, and phase was determined.
The acoustic impedance of water is 1.5 Mrayl.

In addition, a model similar to the element experiment element 200 was created, and the relationship between the frequency, electric impedance, and phase was calculated by simulation.
In the simulation, the acoustic impedance of the base glass epoxy is 8 Mrayl, the acoustic impedance of the silicone of the intermediate layer is 1.2 Mrayl, the acoustic impedance of the organic piezoelectric PVDF is 6.0 Mrayl, and the resonance frequency is 5 MHz. The simulation was performed with the electromechanical coupling coefficient of the piezoelectric body being 0.25 and the capacitance being 40 pF.

[Reference Example 2]
As Reference Example 2, measurement was performed using an element experimental element 210 shown in FIG.
The element experiment element 210 includes a base 212 and an organic piezoelectric element 206.
The base 212 has the same shape as the base 202 except that an area corresponding to the area where the organic piezoelectric element 206 is disposed is opened. The length of the opening of the base 212 was 20 mm, and the length of the organic piezoelectric element 206 was 24 mm. That is, Reference Example 2 has a configuration in which the back surface side of the organic piezoelectric element is an air layer. The acoustic impedance of air is 0.0001 Mrayl. In Reference Example 2 as described above, the relationship between frequency, electrical impedance, and phase was determined.

Also in Reference Example 2, a model similar to the element experiment element 210 was created, and the relationship between frequency, electrical impedance, and phase was calculated by simulation.
In the simulation, the acoustic impedance of air was set to 0.01 Mrayl, and the other numerical values similar to those in the simulation of Reference Example 1 were used.

[Reference Example 3]
As Reference Example 3, measurement was performed using an element experimental element 220 shown in FIG.
That is, the relationship between the frequency, electrical impedance, and phase was determined in the same manner as in Reference Example 1 except that the intermediate layer 204 was not provided.

Also in Reference Example 3, a model similar to the element experiment element 220 was created, and the relationship between frequency, electrical impedance, and phase was calculated by simulation.
In the simulation, the same numerical values as in the simulation of Reference Example 1 were used.

  The electrical impedance calculated by the simulation is shown in FIG. 7A, and the phase is shown in FIG. 7B. The measured electrical impedance is shown in FIG. 8A, and the phase is shown in FIG. 8B. Here, in FIGS. 7A and 8A, the vertical axis represents electrical impedance [ohm], the horizontal axis represents frequency [MHz], Reference Example 1 is indicated by a solid line, and Reference Example 2 is indicated by a broken line. Reference Example 3 is indicated by a one-dot chain line. 7B and 8B, the vertical axis is the phase [deg], the horizontal axis is the frequency [MHz], Reference Example 1 is indicated by a solid line, Reference Example 2 is indicated by a broken line, and Reference Example 3 is indicated by a one-dot chain line.

As shown in FIGS. 7 and 8, in Reference Examples 1 and 2 in which the acoustic impedance of the backing material disposed on the back side of the organic piezoelectric element is smaller than the acoustic impedance of the organic piezoelectric element, resonance occurs at around 4.5 MHz. It can be seen that the piezoelectric performance is high.
On the other hand, in Reference Example 3 in which the acoustic impedance of the backing material disposed on the back surface side of the organic piezoelectric element is larger than the acoustic impedance of the organic piezoelectric body, no resonance is observed, indicating that the piezoelectric performance is low.

Further, it can be seen from Reference Examples 1 to 3 that the lower the acoustic impedance of the backing material (groove filling member) of the organic piezoelectric element, the higher the resonance performance of the organic piezoelectric body, which is preferable. Further, it is understood from the simulation result (FIG. 7) and the actual measurement result (FIG. 8) that the acoustic impedance of the backing material (groove filling member) of the organic piezoelectric element needs to be lower than predicted by the simulation. Therefore, it can be seen from the measured value graph (FIG. 8) that the acoustic impedance of the backing material (groove filling member) of the organic piezoelectric element is preferably 1 Mrayl or less, and more preferably 0.1 Mrayl or less. By dispersing fine particles having a lower density than the resin, such as a glass balloon, in a resin such as silicone, the acoustic impedance can be reduced to 1 Mrayl or less.
From the above results, the effect of the present invention is clear.

The present invention is basically as described above.
Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and modifications may be made without departing from the gist of the present invention.

  For example, in the illustrated ultrasonic diagnostic apparatus 40, the probe main body 42 and the diagnostic apparatus main body 46 are connected via the communication cable 44, but the present invention is not limited to this, and the probe main body 42 and the diagnostic apparatus main body 46 are not limited thereto. And may be connected by wireless communication.

DESCRIPTION OF SYMBOLS 10,100 Ultrasonic probe 12 Backing material 14 Inorganic piezoelectric material 16 Acoustic matching layer 18 Organic piezoelectric material 20 Acoustic lens 22 Groove filling member 24 1st electrode 26 2nd electrode 28 Individual electrode 30 Common electrode 40 Ultrasonic diagnostic apparatus 42 Probe main body 44 Communication cable 46 Diagnostic device main body 48 Received signal processing section 52 Transmission drive section 54 Probe control section 56 Data storage section 60 Image generation section 62 Display section 64 Main body control section 66 Operation section 102 Organic piezoelectric body 104 Second groove filling member 200, 210, 220 Element experimental element 202, 212 Base 204 Intermediate layer 206 Organic piezoelectric element

Claims (8)

Ceramic inorganic piezoelectric materials arranged one-dimensionally with a gap,
An acoustic matching layer arranged on the inorganic piezoelectric material and arranged in the same manner as the inorganic piezoelectric material;
An organic piezoelectric body laminated on the acoustic matching layer;
A groove filling member formed of an organic material having a lower acoustic impedance than the organic piezoelectric body, filling the gap of the inorganic piezoelectric body and the gap of the acoustic matching layer;
A common electrode formed on the organic piezoelectric member, and an individual electrode disposed with the organic piezoelectric member sandwiched with the common electrode,
Furthermore, the individual electrodes are divided and arranged in the arrangement direction of the inorganic piezoelectric bodies, and are formed so as to cover at least the groove filling member.   The ultrasonic probe according to claim 1, wherein the groove filling member is obtained by dispersing fine particles having a density lower than that of the organic material in an organic material.   The ultrasonic probe according to claim 2, wherein the fine particles having a density lower than that of the organic material are glass balloons.   The ultrasonic probe according to claim 1, wherein the organic material includes a silicone resin.   The ultrasonic probe according to claim 1, wherein the organic piezoelectric body covers the acoustic matching layer. Ceramic inorganic piezoelectric materials arranged one-dimensionally with a gap,
An acoustic matching layer arranged on the inorganic piezoelectric material and arranged in the same manner as the inorganic piezoelectric material;
An organic piezoelectric body laminated on the acoustic matching layer;
A common electrode formed on the organic piezoelectric member, and an individual electrode disposed with the organic piezoelectric member sandwiched with the common electrode,
Furthermore, the individual electrodes are divided and arranged in the arrangement direction of the inorganic piezoelectric bodies, and are arranged so as to cover the gaps of the arranged acoustic matching layers. Transducer.   The ultrasonic probe according to claim 1, wherein a potential change generated when the organic piezoelectric body receives an ultrasonic echo is input to a reception amplifier without passing through a cable having a capacitance.   An ultrasonic diagnostic apparatus having the ultrasonic probe according to claim 1.

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