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Researchers Submit Patent Application, "Ultrasound Probe, Ultrasound Diagnostic Imaging Apparatus and Manufacturing Method of Ultrasound Probe", for...

August 29, 2014



Researchers Submit Patent Application, "Ultrasound Probe, Ultrasound Diagnostic Imaging Apparatus and Manufacturing Method of Ultrasound Probe", for Approval

By a News Reporter-Staff News Editor at Health & Medicine Week -- From Washington, D.C., NewsRx journalists report that a patent application by the inventor OKUDA, Shuhei (Tokyo, JP), filed on January 29, 2014, was made available online on August 14, 2014 (see also Konica Minolta, Inc.).

The patent's assignee is Konica Minolta, Inc.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to an ultrasound probe which includes a composite piezoelectric layer which realizes high sensitivity and wider bandwidth, an ultrasound diagnostic imaging apparatus and a manufacturing method of the ultrasound probe.

"Ultrasound diagnostic imaging apparatuses of high image quality are desired, and making ultrasound probes realize high sensitivity and wider bandwidth is suggested as a method for realizing high image quality.

"An ultrasound probe makes an piezoelectric material excite elastic vibration whose thickness corresponds to 1/4) and emits ultrasound generated by the elastic vibration to a subject. With respect to the ultrasound energy emitted in the direction opposite to the direction in which a subject is positioned, since the ultrasound is reflected in the direction opposite to the direction toward a subject by an acoustic reflection layer having high acoustic impedance, which is disposed on the side opposite to the side of the subject, the ultrasound energy to be emitted is increased and high sensitivity can be realized.

"Further, a composite piezoelectric layer is used as a member for generating ultrasound. A composite piezoelectric layer is formed of a piezoelectric material such as lead zirconate (PZT) and a polymer material such as resin wherein the materials are arranged alternately in the direction orthogonal to the direction toward a subject who is to be emitted and the materials are integrated. The composite piezoelectric layer is made to have low acoustic impedance by being provided with a polymer material and is made to have acoustic impedance close to that of a subject which is low comparing to the acoustic impedance of the piezoelectric material. Thereby, high sensitivity and wider bandwidth can be realized.

"However, taking the above measures is not enough to realize high sensitivity and wider bandwidth. FIG. 11 shows that the thickness of an adhesion layer between the piezoelectric material and the acoustic reflection layer has relevance with the frequency band width. The horizontal axis shows frequency (MHz) and the vertical axis shows response sensitivity (Loop Gain) of piezoelectric material with respect to frequency in decibel (dB). The curve A shows the case where the thickness of the adhesion layer between the piezoelectric material alone and the acoustic reflection layer is 1.5 .mu.m, the curve B shows the case where the above thickness is 1.0 .mu.m and the curve C shows the case where the above thickness is 0.5 .mu.m. As it is clear from the curves, as the thickness of the adhesion layer that attaches the piezoelectric material and the acoustic reflection layer is thinner, the frequency band at the desired response sensitivity of the piezoelectric material is wider. Therefore, in a composite piezoelectric layer in which a piezoelectric material and a polymer material are arranged alternately in the direction orthogonal to the direction toward a subject to be irradiated, the frequency band also becomes wider if the thickness of the adhesion layer which attaches the piezoelectric material parts in the composite piezoelectric, layer and the acoustic reflection layer becomes thinner. That is, making the thickness of the adhesion layer which attaches the piezoelectric material parts in the composite piezoelectric layer and the acoustic reflection layer thinner is important in order to realize even wider bandwidth.

"In order to realize this, the adhesion layer between the piezoelectric material parts in the composite piezoelectric layer and the acoustic reflection layer needs to be made thin by performing the bonding by the adhesion layer after performing mirror polishing on the bonding surfaces of the composite piezoelectric layer, which is to be bonded with the acoustic layer by the adhesion layer, and smoothen the bonding surfaces before the bonding.

"However, because the hardness of the piezoelectric material such as PZT which forms the piezoelectric material and the hardness of the polymer material formed of a resin differ from each other, when mirror polishing is to be performed on the bonding surface of the composite piezoelectric layer, the piezoelectric material will be polished more comparing to the polymer material. As a result, the bonding surface of the piezoelectric material and the polymer material will be bumpy and the piezoelectric material parts cannot be smoothened sufficiently causing a problem that the thickness of the adhesion layer cannot be uniformly and sufficiently thin.

"In view of such problem, JP 2009-61112 discloses a technique for manufacturing a composite piezoelectric layer by cutting out the piezoelectric material to their midpoint and not all the way to the bottom and filling the polymer material in the spaces formed by cutting out the piezoelectric material. It is described that because the entire bonding surface that bonds with the acoustic reflection layer is the piezoelectric material in the composite piezoelectric layer formed by the above method, bumps due to difference in hardness between the piezoelectric material and the polymer material does not occur even if mirror polishing is performed; and thus, the adhesion layer can be thin."

As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventor's summary information for this patent application: "However, in the technique described in JP 2009-61112, there is a problem that the advantageous effect as a composite piezoelectric layer is reduced because the piezoelectric material is not cut out to the bonding surface with the acoustic reflection layer. Therefore, in order to improve the advantageous effect, it is necessary to cut out the piezoelectric material at the parts where the material needs to be cut out to the extent almost reaching the bonding surface with the acoustic reflection layer. Therefore, cracks can easily occur in the bonding surface and there are problems in maintaining durability and stability of the composite piezoelectric layer; thus, desired ultrasound cannot be generated stably.

"The present invention is made in view of the above problems and an object of the present invention is to provide an ultrasound probe provided with a composite piezoelectric layer which realizes high sensitivity and wider bandwidth and which has high durability and stability, an ultrasound diagnostic imaging apparatus and a manufacturing method of the ultrasound probe.

"To realize the above object, according to a first aspect of the present invention, an ultrasound probe outputs ultrasound on a basis of a drive signal which is to be received, and the ultrasound probe includes a composite piezoelectric layer in which a piezoelectric material and a polymer material are arranged alternately in a one-dimensional array or in a two-dimensional array, an acoustic reflection layer which has an acoustic impedance higher than an acoustic impedance of the composite piezoelectric layer and an adhesion layer which bonds the composite piezoelectric layer and the acoustic reflection layer, and in a bonding surface of the composite piezoelectric layer that bonds with the acoustic reflection layer, a polymer material part is concaved in a direction opposite to an acoustic reflection layer side comparing to an piezoelectric material part.

"Preferably, a thickness t m) of the adhesion layer between a bonding surface of the piezoelectric material part of the composite piezoelectric layer and the acoustic reflection layer is 0
"Preferably, a surface roughness Ra (.mu.) of a surface of the piezoelectric material in the composite piezoelectric layer opposite to the acoustic reflection layer side is Ra.ltoreq.0.4.

"To realize the above object, according to a second aspect of the present invention, an ultrasound diagnostic imaging apparatus includes an ultrasound probe, a transmission unit which generates the drive signal and an image generation unit which generates ultrasound image data for displaying an ultrasound image on a basis of the received signal output by the ultrasound probe.

"Preferably, the drive signal is a rectangular wave including a plurality of pulses, a pulse width of at least one pulse among the plurality of pules being different from pulse widths of other pulses.

"Preferably, the drive signal includes a first pulse signal, a second pulse signal whose polarity is different from the first pulse signal and a third pulse signal whose polarity is same as the first pulse signal, and a pulse width of the first pulse signal, the pulse width of the second pulse signal and the pulse width of the third pulse signal are different from one another.

"To realize the above object, according to a third aspect of the present invention, a manufacturing method of an ultrasound probe which outputs ultrasound on a basis of a drive signal which is to be received, the ultrasound probe comprising a composite piezoelectric layer in which a piezoelectric material and a polymer material are arranged alternately in a one-dimensional array or in a two-dimensional array and an acoustic reflection layer which has an acoustic impedance higher than an acoustic impedance of the composite piezoelectric layer and the composite piezoelectric layer and the acoustic reflection layer being bonded by an adhesion layer, the manufacturing method includes forming the composite piezoelectric layer in which the piezoelectric material and the polymer material are arranged alternately, removing parts of polymer material parts in a bonding surface of the composite piezoelectric layer which bonds with the acoustic reflection layer so that the polymer material parts concave in a direction opposite to an acoustic reflection layer side comparing to piezoelectric material parts, polishing a bonding surface of the composite piezoelectric layer after the removing and bonding of the bonding surface of the composite piezoelectric layer and the acoustic reflection layer by the adhesion layer.

"Preferably, removing of the parts of the polymer material parts in the removing is performed by etching.

"Preferably, removing of the parts of the polymer material parts in the removing is performed by dicing.

"To realize the above object, according to a fourth aspect of the present invention, a manufacturing method of an ultrasound probe which outputs ultrasound on a basis of a drive signal which is to be received, the ultrasound probe comprising a composite piezoelectric layer in which a piezoelectric material and a polymer material are arranged alternately in a one-dimensional array or in a two-dimensional array and an acoustic reflection layer which has an acoustic impedance higher than an acoustic impedance of the composite piezoelectric layer and the composite piezoelectric layer and the acoustic reflection layer being bonded by an adhesion layer, the manufacturing method includes filling the polymer material in spaces formed in the piezoelectric material with a predetermined interval therebetween to form the composite piezoelectric layer, polishing the bonding surface of the composite piezoelectric layer after the filling, and bonding of the bonding surface of the composite piezoelectric layer and the acoustic reflection layer by the adhesion layer, and in the filling, the polymer material is filled so that a polymer material part in the bonding surface of the composite piezoelectric layer that bonds with the acoustic reflection layer is concaved in a direction opposite to an acoustic reflection layer side comparing to an piezoelectric material part.

BRIEF DESCRIPTION OF THE DRAWINGS

"The present invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein:

"FIG. 1 shows an outer configuration of an ultrasound probe;

"FIG. 2A shows an outline of the ultrasound probe;

"FIG. 2B shows an outline of the ultrasound probe;

"FIG. 3A shows an outline of a composite piezoelectric layer;

"FIG. 3B shows another example of an outline of the composite piezoelectric layer;

"FIG. 4 shows a flow of a manufacturing method of the ultrasound probe;

"FIG. 5 shows rough positions of an electrode layer and a flexible printed board;

"FIG. 6 shows an outer configuration of an ultrasound diagnostic imaging apparatus;

"FIG. 7 is a block diagram showing an outline configuration of the ultrasound diagnostic imaging apparatus;

"FIG. 8 is a block diagram showing an outline configuration of a transmission unit;

"FIG. 9 is an explanatory diagram of a drive waveform of a pulse signal;

"FIG. 10 is an explanatory diagram of a waveform of a pulse signal which is to be transmitted; and

"FIG. 11 shows a relation between thickness of an adhesive layer and a band to be irradiated."

For additional information on this patent application, see: OKUDA, Shuhei. Ultrasound Probe, Ultrasound Diagnostic Imaging Apparatus and Manufacturing Method of Ultrasound Probe. Filed January 29, 2014 and posted August 14, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=1786&p=36&f=G&l=50&d=PG01&S1=20140807.PD.&OS=PD/20140807&RS=PD/20140807

Keywords for this news article include: Diagnostic Imaging, Konica Minolta Inc.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Health & Medicine Week


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