JP2006334075A - Ultrasonic probe and ultrasonic diagnostic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe which can obtain a high-resolution diagnostic image by avoiding the attenuation of an ultrasonic wave by an acoustic lens and which can increase directivity by virtue of structural simplicity, and ultrasonic diagnostic equipment. <P>SOLUTION: An acoustic matching layer 2 is formed in such a manner that an acoustic impedance of the acoustic matching layer 2 is continuously changed in the direction of thickness to a value close to the acoustic impedance of a subject 15 from a value close to that of a piezoelectric element 1, and a subject-side surface 2s of the acoustic matching layer 2 is formed in a curved shape along the width direction and arrangement direction of the piezoelectric element 1. This enables ultrasonic beams to converge in the width direction so that the acoustic lens 13 can fall into disuse, and enables the ultrasonic beams to be diffused in the arrangement direction so that the directivity can be increased. The thickness of the acoustic matching layer 2 is set equal to/greater than half the wavelength of an ultrasonic frequency, so that a change in thickness, caused by the curved shape, cannot affect frequency characteristics. When a subject-side sonic velocity of the acoustic matching layer 2 is lower than the sonic velocity of the subject, the curved shape is convexly formed in the width direction and concavely formed in the arrangement direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe used for obtaining diagnostic information of a subject by transmitting ultrasonic waves to a subject such as a living body, and an ultrasonic diagnostic apparatus using the ultrasonic probe About.

  An ultrasonic diagnostic apparatus transmits ultrasonic waves into a subject, detects echo signals reflected in the living body, and displays a tomographic image of the tissue in the living body on a monitor, which is necessary for diagnosis inside the living body. Provide information. The ultrasonic diagnostic apparatus uses an ultrasonic probe to transmit an ultrasonic wave into the subject and receive an echo signal from the subject.

  FIG. 10 shows an example of a conventional ultrasound probe. In the figure, an ultrasonic probe 20 includes a piezoelectric element 11 that transmits and receives a plurality of ultrasonic waves arranged in a certain direction, and two layers provided on the front surface (upper side in the drawing) of the piezoelectric element 11 on the subject side. The acoustic matching layer 12 (12a, 12b), the acoustic lens 13 provided on the surface of the acoustic matching layer 12 on the subject side, and the back surface of the piezoelectric element 11 on the opposite side of the acoustic matching layer 12 with respect to the piezoelectric element 11 It is comprised from the back surface load material 14 provided in this. Electrodes (not shown) are arranged on the front and back surfaces of the piezoelectric element 11, and transmit and receive electrical signals to and from the piezoelectric element 11.

  The piezoelectric element 11 is formed of a piezoelectric ceramic such as a PZT system, a single crystal, or a composite piezoelectric body in which the material and the polymer are combined. The piezoelectric element 11 converts the voltage into an ultrasonic wave and transmits the ultrasonic wave into the subject, or the subject. The echo reflected inside is converted into an electrical signal and received. In the illustrated example, a plurality of piezoelectric elements 11 are arranged in the X direction. Such a plurality of arrangements of the piezoelectric elements 11 can be deflected or focused by electronically scanning ultrasonic waves, which enables so-called electronic scanning.

  The acoustic matching layer 12 is provided in order to efficiently transmit and receive ultrasonic waves into the subject, and specifically, plays a role of making the acoustic impedance of the piezoelectric element 11 close to the acoustic impedance of the subject stepwise. In the illustrated example, two acoustic matching layers 12a and 12b are provided, but this may be one layer or three or more layers. Further, a configuration is also used in which the acoustic matching layer 12 is divided and arranged corresponding to each of the plurality of piezoelectric elements 11 to widen the directivity of the ultrasonic waves (see, for example, Patent Document 1).

  The acoustic lens 13 plays a role of refracting and narrowing the ultrasonic beam using the difference in sound velocity with the subject in order to increase the resolution of the diagnostic image. In the illustrated example, it is formed in a semi-cylindrical shape that is convex along the Y direction, and the ultrasonic beam is focused in the Y direction. Further, the back load member 14 is coupled to and holds the piezoelectric element 11 and further plays a role of attenuating unnecessary ultrasonic waves. In the present specification, the X direction in the figure is also referred to as “(piezoelectric element) arrangement direction”, the Y direction as “(piezoelectric element) width direction”, and the Z direction as “(piezoelectric element) thickness direction”. Shall.

  In contrast to the above-described acoustic matching layer 12 composed of a plurality of layers, the conventional technology further discloses an acoustic matching layer as shown in FIG. 11 having a structure in which acoustic impedance is continuously changed in the thickness direction. (For example, refer to Patent Document 2). In FIG. 11, the acoustic matching layer 22 includes a first acoustic matching material 22 a having a cone shape or a quadrangular pyramid shape having an acoustic impedance substantially equal to that of the piezoelectric element 11, and a remaining portion having an acoustic impedance substantially equal to the subject. The second acoustic matching material 22b that occupies is combined in the thickness direction.

Specifically, the first acoustic matching material 22a is formed of a material such as glass, aluminum, ceramic, or silicon single crystal having a large acoustic impedance (similar to the acoustic impedance of the piezoelectric element 11), and the acoustic impedance is small in the gap. It is formed by filling a second acoustic matching layer 22b made of epoxy resin, urethane resin, silicone rubber or the like (close to the acoustic impedance of the subject). The acoustic impedance can be continuously changed in the thickness direction by arranging the lower side of FIG. 11 on the piezoelectric element 11 side and the upper side on the subject side (acoustic lens 13 side). By configuring the acoustic matching layer 22 as described above, the use frequency can be widened, and the efficiency of ultrasonic diagnosis can be increased.
JP-A-9-238399 Japanese Patent Application Laid-Open No. 11-89835

  An electronic scanning type ultrasonic diagnostic apparatus is configured to drive a piezoelectric element into an arbitrary group by giving a certain delay time to each piezoelectric element, and to transmit ultrasonic waves from each piezoelectric element into the subject. The echo signal from is received. By giving the delay time, the ultrasonic beam is focused or deflected, and a wide field width or high resolution ultrasonic image can be obtained. This is already known as a general system. As an ultrasonic probe, in order to obtain such a high-resolution ultrasonic image, what is important is that a plurality of individual piezoelectric elements that are electronically scanned are covered by an acoustic matching layer and further through an acoustic lens. The directivity of the ultrasonic beam emitted to the specimen is excellent, that is, the directivity is wide.

  As one measure for widening the directivity, an acoustic matching layer is divided corresponding to a plurality of arranged piezoelectric elements as shown in Patent Document 1, and acoustic coupling between adjacent piezoelectric elements is performed. For example, the configuration may be reduced. However, in this configuration, there is a problem that it is difficult to widen the directivity beyond that because the directivity is determined by the interval between the arranged piezoelectric elements or the width and drive frequency of the piezoelectric elements.

  On the other hand, in order to improve the resolution of the diagnostic image of the ultrasonic diagnostic apparatus, a configuration in which the above-described acoustic lens 13 is provided as a measure for converging and thinning the ultrasonic beam is generally used. As a material of the acoustic lens 13, generally used is a silicone rubber having a sound speed slower than that of the subject and having an acoustic impedance close to that of the subject. The material whose sound speed is slower than that of the subject is selected because the acoustic lens 13 can have a convex shape as shown in FIG. 10 when the ultrasonic beam is converged. This is because it is easier to obtain adhesion. However, it is possible to make the acoustic lens 13 concave by using a material whose sound speed is faster than that of the subject, and the acoustic lens 13 can be used in the same manner by bringing it into close contact with the subject.

  However, in the ultrasonic probe including the acoustic lens according to the related art described above, when silicone rubber having an acoustic impedance close to the subject is used as the material of the acoustic lens 13 so that the surface facing the subject has a convex shape, There was a problem that sensitivity and frequency characteristics deteriorated as attenuation of ultrasonic waves increased. On the other hand, if silicone rubber with low attenuation is selected in order to avoid this, another problem arises that this time the acoustic impedance is away from the value of the subject and the ultrasound is reflected at the boundary, adversely affecting the image. It was.

  In recent years, the frequency of use of ultrasonic probes has tended to be wider, and since there are many cases where multiple frequencies are used, it is important to increase the bandwidth. There is a demand to widen the directivity of the probe and to obtain a high-resolution ultrasonic image. For this reason, there is a need for a technique for avoiding obstacles to high resolution such as the above-described improvement in directivity and avoidance of ultrasonic attenuation.

  Therefore, the present invention eliminates all the problems of the prior art as described above, avoids attenuation of ultrasonic waves as much as possible, prevents deterioration of sensitivity and frequency characteristics, and provides directivity with respect to the arrangement direction of piezoelectric elements. An object of the present invention is to provide an ultrasonic probe that can be widened and obtain a high-resolution diagnostic image, and an ultrasonic diagnostic apparatus including the ultrasonic probe.

  The present invention focuses on the fact that the thickness of the acoustic matching layer is not related to the frequency characteristics of the ultrasonic wave when an acoustic matching layer whose acoustic impedance continuously changes from the piezoelectric element side to the subject side is used. The acoustic lens is removed and the acoustic matching layer is used to narrow and converge the ultrasonic wave in the width direction of the piezoelectric element on the one hand, and to spread the directivity by diffusing the ultrasonic wave in the arrangement direction of the piezoelectric element on the other hand. The above-mentioned problem is solved at the same time, and specifically includes the following contents.

  That is, according to one aspect of the present invention, a plurality of piezoelectric elements arranged and transmitting / receiving ultrasonic waves to / from a subject, an acoustic matching layer provided on the subject-side front surface of the piezoelectric elements, and the piezoelectric elements An ultrasonic probe comprising a back load material provided on the back surface of the piezoelectric element on the opposite side of the acoustic matching layer, and a pair of electrodes provided on the front surface and the back surface of the piezoelectric element. The acoustic impedance of the acoustic matching layer continuously changes in the thickness direction from a value close to the piezoelectric element in the piezoelectric element side portion to a value close to the subject in the object side portion, A surface shape on the subject side of the acoustic matching layer corresponding to each of the plurality of piezoelectric elements is formed in a curved shape along the arrangement direction of the plurality of piezoelectric elements and a width direction orthogonal thereto, and the acoustic matching Layer arranged ultrasonic beam said array Is diffused into direction, an ultrasonic probe, characterized in that to converge in the width direction.

  The acoustic matching layer has a thickness of at least a half wavelength or more of a use frequency band of ultrasonic waves generated by the piezoelectric element.

  When the sound velocity of the subject side portion of the acoustic matching layer is Cml and the sound velocity of the subject is Cb, when Cml <Cb, the curved surface along the arrangement direction with respect to the subject is concave, and along the width direction. Each curved surface is formed in a convex shape, and when Cml> Cb, the curved surface along the arrangement direction with respect to the subject is formed in a convex shape, and the curved surface along the width direction is formed in a concave shape.

  The curved surface along the arrangement direction can be composed of a combination of curved surfaces having a plurality of curvature radii, and the plurality of curvature radii can be changed along the arrangement direction. In this case, the change in the plurality of radii of curvature is such that the radius of curvature is relatively large at a position corresponding to the center of each voltage element in the arrangement direction, and the radius of curvature progresses from the center to both ends in the arrangement direction. It is preferable to form so that becomes relatively gradually smaller.

  The shape of the curved surface along the arrangement direction can be changed along the width direction. In this case, the radius of curvature is relatively small at a position corresponding to the center portion in the width direction, and the radius of curvature gradually increases gradually from the center portion to both ends in the width direction. preferable.

  The curved surface along the width direction can be composed of a combination of curved surfaces having a plurality of curvature radii, and the plurality of curvature radii can be changed along the width direction. In this case, the change in the plurality of radii of curvature is such that the radius of curvature is relatively small at the center in the width direction, and the radius of curvature gradually increases gradually from the center to both ends in the width direction. It is preferable to form such a shape.

  The acoustic matching layer includes a first layer in which a plurality of conical or polygonal cone-shaped first acoustic matching materials having an acoustic impedance substantially equal to that of the piezoelectric element are arranged densely so that the cones are in the same direction. The second layer in which the void portion of the first layer is filled with the second acoustic matching material having an acoustic impedance substantially equal to that of the subject can be formed in combination in the thickness direction. Alternatively, the acoustic matching layer is formed by filling a resin having an acoustic impedance close to a subject with a powder having an acoustic impedance substantially equal to the piezoelectric element, and inclining the degree of powder filling in the resin in the thickness direction. can do.

  According to another aspect of the present invention, an ultrasonic probe that transmits / receives ultrasonic waves to / from a subject is electrically connected to the ultrasonic probe, and a drive signal is transmitted to the ultrasonic probe. An ultrasonic diagnostic apparatus configured to transmit, process an electrical signal from the ultrasonic probe, and output a diagnostic result, wherein any one of the ultrasonic probes described above The present invention relates to an ultrasonic diagnostic apparatus to be used.

  By implementing the present invention, it is possible to converge the ultrasonic beam in the width direction of the piezoelectric element using the acoustic matching layer, and avoid attenuation of the ultrasonic wave by the acoustic lens, and at the same time, arrange the ultrasonic beam into the arrangement of the piezoelectric element. An ultrasonic probe capable of widening directivity by diffusing in a direction and obtaining a high-resolution diagnostic image, and an ultrasonic diagnostic apparatus using the ultrasonic probe are realized. it can.

  Hereinafter, an ultrasonic probe according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an ultrasonic probe according to the present embodiment. In the figure, an ultrasonic probe 10a includes a plurality of piezoelectric elements 1 arranged in the X direction (arrangement direction) in the figure, and a front surface in the Z direction (upward in the figure) on the subject side with respect to each piezoelectric element 1. And a back load material 4 disposed on the back surface in the thickness direction opposite to the acoustic matching layer 2 with respect to the piezoelectric element 1. The functions of these components are basically the same as those described in the prior art. As is apparent from the figure, the ultrasonic probe 10a according to the present embodiment excludes the acoustic lens (reference numeral 13 in FIG. 10) that is used in the prior art.

  A ground electrode 6 is provided on the front surface of the piezoelectric element 1 in the thickness direction, and a signal electrode 7 is provided on the back surface. Both electrodes 6 and 7 are formed on the front surface and the back surface of the piezoelectric element 1 by vapor deposition of gold or silver, sputtering, or baking of silver, respectively. The signal electrode 7 of each piezoelectric element 11 is individually connected to a signal electrical terminal 8 and is electrically connected to an ultrasonic diagnostic apparatus (not shown) through a cable together with the ground electrode 6. Using both electrodes 6 and 7, a regular pulse voltage generated by the ultrasonic diagnostic apparatus is applied to the piezoelectric element 1, and conversely, an echo reception wave converted into an electric signal by the piezoelectric element 1 is transmitted to the ultrasonic diagnostic apparatus body. The

  The acoustic matching layer 2 according to the present embodiment has a characteristic that acoustic impedance continuously changes in the thickness direction. That is, the portion of the acoustic matching layer 2 located on the ground electrode 6 side of the piezoelectric element 1 has an acoustic impedance close to that of the piezoelectric element 1, and the portion of the acoustic matching layer 2 located on the subject side is close to the subject. Between which the acoustic impedance slopes continuously. More specifically, the acoustic impedance of the acoustic matching layer 2 on the installation electrode 6 side is about 30 megarail (when the piezoelectric element 1 is a piezoelectric ceramic such as a PZT system), and the acoustic impedance on the subject side is about 1.5 megarail ( When the subject is a human body), the acoustic impedance of the acoustic matching layer 2 continuously changes during that time.

  For example, as shown in the section of the prior art with reference to FIG. 11, such a continuous change in the acoustic impedance causes the acoustic matching layer 2 to have a conical or quadrangular pyramid having an acoustic impedance substantially equal to that of the piezoelectric element 1. Obtained by combining the first acoustic matching material having a polygonal pyramid shape and the like and the second acoustic matching material occupying the remaining portion having an acoustic impedance substantially equal to the subject in the thickness direction (see FIG. The barbed stripe pattern of the acoustic matching layer 2 shown in FIG. 1 schematically shows a state in which both members are combined. In addition to this method, a resin having an acoustic impedance close to the subject 15 is filled with a powder having a high specific gravity (high acoustic impedance) such as tungsten powder, and the degree of powder filling in the resin in the thickness direction is determined. Continuous changes in acoustic impedance, such as tilting, can also be obtained by other alternative methods.

  By using the acoustic matching layer 2 in which the acoustic impedance is continuously inclined as described above, a wide frequency band can be realized. In addition, according to the experiments of the inventors of the present application, when the acoustic matching layer 2 that continuously changes the acoustic impedance as described above is used, the thickness of the acoustic matching layer 2 is about ½ of the used frequency band. If it is longer than the wavelength, its thickness and frequency characteristics are not so related.

  In the present embodiment, attention is paid to the fact that the thickness does not affect the frequency characteristics in the acoustic matching layer 2 in which the acoustic impedance is continuously inclined, and each piezoelectric element is actively utilized by using this as shown in FIG. The surface on the subject side of the acoustic matching layer 2 corresponding to the element 1 is formed in a curved shape along both the width direction (Y direction) and the arrangement direction (X direction) of the piezoelectric element 1, thereby using an acoustic lens. It is assumed that the function of converging and diffusing the ultrasonic beam without being performed is provided. In the example shown in FIG. 1, a convex curved surface is formed in the width direction and a concave curved surface is formed in the arrangement direction. This situation will be described in more detail with reference to FIGS.

  FIG. 2 shows a cross section in the width direction parallel to the Y-axis of the ultrasonic probe 10 shown in FIG. For example, when silicone rubber is used as one acoustic matching material (reference numeral 22b in FIG. 11) constituting the acoustic matching layer 2, the sound velocity Cml on the subject 15 side of the acoustic matching layer 2 is about 1.0 km / sec. . On the other hand, if the subject 15 is a living body, the speed of sound Cb is about 1.53 km / second, so that a relationship of Cml <Cb is established between the two. In this case, if the shape of the surface 2s of the acoustic matching layer 2 is convex with respect to the subject 15 as shown in FIG. 2, the ultrasonic wave is refracted using the difference in sound speed to arbitrarily set the surface of the subject 15 It is possible to focus on the position of and to converge. As a result, the acoustic matching layer 2 performs the same function as the acoustic lens, and the effect of increasing the resolution is obtained. The convex surface at this time can be, for example, a convex shape having a single radius of curvature.

  Here, since the acoustic matching layer 2 functions as an original acoustic matching layer, a thickness of ½ wavelength or more of the used frequency band is secured even in the thinnest portion. If the surface as described above is curved based on this thickness, an acoustic matching layer that can simultaneously perform the functions of both the acoustic matching layer and the acoustic lens can be obtained, and as a result, the acoustic lens can be removed. it can.

  The curved surface shape of the surface 2 s of the acoustic matching layer 2 is a curved surface having a radius of curvature with respect to the width direction of the piezoelectric element 1, but is not limited to this, for example, a trapezoid or a part of a polygon. Other shapes may be used as long as the ultrasonic beam can be converged.

  On the other hand, FIG. 3 shows a cross section in the arrangement direction parallel to the X-axis of the ultrasonic probe 10 shown in FIG. The figure is a part thereof, and the illustrated shape is connected to the X direction (left and right direction) for a certain length to constitute the ultrasonic probe 10 shown in FIG. Here, as described in FIG. 2, the acoustic impedance of the acoustic matching layer 2 continuously changes in the thickness direction from a value close to the piezoelectric element 1 to a value close to the subject 15, and the acoustic matching layer 2 The relationship Cml <Cb is established between the sound velocity Cml on the subject side and the sound velocity Cb of the subject. In such a case, the surface of the acoustic matching layer 2 corresponding to each of the plurality of piezoelectric elements 1 is formed in a concave surface with respect to the subject 15 as shown in FIG. (Right and left directions) can be refracted and diffused to obtain the effect of widening the directivity of the ultrasonic probe 10.

  In this case as well, a thickness of 1/2 wavelength or more of the used frequency band is secured even in the thinnest portion in order for the acoustic matching layer 5 to perform its original function. In addition, the concave surface at this time can be, for example, a concave shape having a single radius of curvature, and the curved surface can be another shape such as a trapezoid or a part of a polygon.

  When the surface of the acoustic matching layer 2 has a curved shape along the width direction and the arrangement direction as described above, the thickness of the acoustic matching layer 2 is naturally not constant and varies. This means that if the acoustic matching layer is composed of a single layer or a plurality of layers having the conventional structure, the frequency characteristics greatly fluctuate due to the change in thickness, so that the desired characteristics cannot be obtained. Was. In other words, if the function of the acoustic lens is to be imposed with the acoustic matching layer of the conventional type, the acoustic lens function has to be prioritized or the frequency characteristic has to be prioritized. It was difficult to double as a lens.

  On the other hand, if the acoustic matching layer 2 according to the present embodiment has a continuously inclined acoustic impedance, the surface is formed into a curved surface by securing a thickness of at least 1/2 wavelength or more. This does not affect the frequency characteristics even if the frequency changes. For this reason, by constructing the surface of the acoustic matching layer 2 as described above into a curved surface, it is possible to achieve the function of an acoustic lens for converging the ultrasonic beam in the width direction at the same time as achieving a wide frequency band. In addition, the directivity can be widened by diffusing the ultrasonic beam in the arrangement direction.

  In the example shown in FIG. 3, the acoustic matching layer 2 is divided and arranged in the arrangement direction corresponding to each piezoelectric element 1. By dividing in this way, the acoustic coupling between the adjacent piezoelectric elements 1 can be reduced, and the effect of widening the directivity can be obtained. The divided groove portions may be filled with a material such as silicone rubber or urethane rubber having a small acoustic coupling. However, the same effect can be obtained even if the acoustic matching layer 2 is integrally arranged on the entire plurality of piezoelectric elements 1 without being divided in this way. In this case, the curved surface shape of the surface of the acoustic matching layer 2 is formed corresponding to each piezoelectric element 1.

  Next, FIG. 4 shows an ultrasonic probe 10b of another aspect according to the present embodiment. Here, the surface of the acoustic matching layer 2 with respect to the subject 15 is piezoelectric, contrary to FIG. The element 1 is formed into a concave curved surface along the width direction (Y direction) and a convex curved surface along the arrangement direction (X direction). This is a case where a relationship of Cml> Cb is established between the sound velocity Cml on the subject side of the acoustic matching layer 2 and the sound velocity Cb of the subject.

  That is, when a material mainly composed of epoxy resin or the like is used as the material of the acoustic matching layer 2, the sound velocity Cml on the subject side of the acoustic matching layer 2 is about 2 to 2.6 km / sec. If the subject is also a living body, the sound velocity Cb of the subject is about 1.53 km / second, so the relationship of Cml> Cb is established. In this case, by forming the curved surface in the opposite direction to the above-described aspect, the ultrasonic beam can be converged in the width direction and diffused in the arrangement direction, just like the previous aspect. Details thereof will be described with reference to FIGS.

  FIG. 5 is a cross-sectional view in the width direction (Y direction) of the ultrasonic probe 10b shown in FIG. 4, and the surface 2s of the acoustic matching layer 2 is formed in a concave shape. Except for the shape of the surface, other structures are the same as those shown in FIG. That is, the acoustic impedance of the acoustic matching layer 2 continuously changes in the thickness direction from a value close to the piezoelectric element 1 to a value close to the subject 15 and a minimum thickness of 1/2 wavelength is secured. This concave surface can be, for example, a concave shape having a single radius of curvature.

  By configuring the acoustic matching layer 2 with such a curved surface shape, the ultrasonic wave can be refracted and narrowed in the width direction (left-right direction in FIG. 5) using the difference in sound velocity, and the ultrasonic wave can be focused on the subject 15. It is possible to converge to an arbitrary focal position within. It is the same as in the previous embodiment that the attenuation of ultrasonic waves can be eliminated by removing the acoustic lens.

  Next, FIG. 6 shows a cross section in the arrangement direction (X direction) of the ultrasonic probes 10b shown in FIG. 4, which is also the surface corresponding to each piezoelectric element 1 of the acoustic matching layer 2 in the same manner. However, the curved surface shape is convex, contrary to the previous aspect, due to the speed of sound. Except for this point, the other configuration is the same as that shown in FIG. By making the surface of the acoustic matching layer 2 with respect to the subject corresponding to each piezoelectric element 1 in such a convex shape, ultrasonic waves can be refracted and diffused in the arrangement direction, and the directivity can be widened. it can.

  As described above, in the ultrasonic probe 10b shown in FIG. 4, the surface of the acoustic matching layer 2 with respect to the subject is formed in a concave shape along the width direction and in a convex shape along the arrangement direction. The same effect as the ultrasonic probe 10a shown in FIG. 1 can be obtained.

  Next, an ultrasonic probe according to a second embodiment of the present invention will be described with reference to the drawings. In the previous embodiment, the surface shape of the acoustic matching layer 2 has been described as an example of a curved surface shape (concave surface, convex surface) having a single radius of curvature in both the width direction and the arrangement direction. In the present embodiment, the curved surface shape is constituted by a combination of curved surfaces having a plurality of curvature radii along one or both of the width direction and the arrangement direction, and by changing the curvature radii, the better An ultrasonic probe capable of obtaining directivity and resolution is provided.

  FIG. 7 is a side sectional view in the width direction of the ultrasonic probe 10a according to the present embodiment. Here, the surface of the acoustic matching layer 2 is the same as that of the ultrasonic probe 10a shown in FIG. When the curvature radius of the curved surface shape of the acoustic matching layer 2 is a single one, the resolution is improved near the focal length, that is, the distance where the ultrasonic beam is most narrowed and the beam diameter is narrowed, but deviated from the focal length. On the contrary, the region tends to diffuse the beam, increase the beam diameter and reduce the resolution.

  In the present embodiment, the acoustic matching layer 2 is configured to improve such a phenomenon and reduce the ultrasonic beam diameter in a wide region. That is, the surface portion 2c of the acoustic matching layer 2 corresponding to the center portion in the width direction of the piezoelectric element 1 in FIG. 7 decreases the radius of curvature to bring the focal length of the ultrasonic beam closer, and increases the radius of curvature as proceeding to both ends 2d. The focal length of the ultrasonic beam is gradually increased. As a result, although the beam is slightly thicker than the focused ultrasound beam as a whole, the beam can be prevented from being diffused and narrowed in a wide area, so that the resolution can be improved in a wide area. Is obtained. The change in the radius of curvature may be continuous or stepwise.

  In FIG. 7, the surface of the acoustic matching layer 2 has a convex shape. This is a shape when the sound velocity Cml of the acoustic matching layer 2 corresponding to FIG. 2 described above is slower than the sound velocity Cb of the subject. If the relationship between the sound speeds is reversed, the curved surface shape becomes a concave shape corresponding to FIG. Even in this case, the same effect can be obtained by changing the curved surface shape in the width direction.

  Next, FIG. 8 shows a part of a side sectional view in the arrangement direction (X direction) of the ultrasound probe 10b according to the present embodiment. Here, it is the same as the ultrasonic probe 10b shown in FIG. 6 except for the surface shape of the acoustic matching layer 2 with respect to the subject 15. In FIG. 8, the surface shape of the acoustic matching layer 2 is constituted by a curved surface having a plurality of radii of curvature. That is, the radius of curvature of the surface portion 2e corresponding to the center position of each piezoelectric element 1 in the arrangement direction (left-right direction in the figure) is maximized, and the curvature radius is gradually reduced as it proceeds to both ends 2f in the arrangement direction of each piezoelectric element 1. It is composed of curved surfaces. The change in the radius of curvature may be continuous or stepwise.

  In this way, by forming a curved surface in which the curvature radius of the surface shape of the acoustic matching layer 2 is changed along the arrangement direction, the ultrasonic beam at the center portion is not diffused so much, and the curvature radius increases toward the end portion. The diffusion becomes smaller and the diffusion of the ultrasonic beam gradually increases, and a wide directivity can be obtained. With this configuration, the thickness of the acoustic matching layer 2 can be changed less than the curved surface having a single radius of curvature, and the ultrasonic attenuation of the acoustic matching layer 2 can be reduced. The effect that a fall can be prevented can be acquired.

  In FIG. 8, the acoustic matching layer 2 is divided so as to correspond to each piezoelectric element 1. However, the same effect can be obtained even if the acoustic matching layer 2 is integrally formed so as to cover a plurality of piezoelectric elements 1 without being divided. Is the same as the previous embodiment. In FIG. 8, the surface of the acoustic matching layer 2 has a convex shape. This is a shape when the sound velocity Cml of the acoustic matching layer 2 corresponding to FIG. 6 described above is faster than the sound velocity Cb of the subject. If the relationship between the sound speeds is reversed, the curved surface shape is a concave surface corresponding to FIG.

  In addition to the above, regarding the curved surface shape of the acoustic matching layer 2 along the arrangement direction, in the width direction orthogonal to the arrangement direction (direction perpendicular to the drawings of FIGS. 3, 6, and 8, the Y direction of FIG. 1). The curved surface shape can be changed along. That is, the curvature radius is made the smallest so that the directivity is widened in the center part in the width direction (same as above) of the same curved surface shape, and the curvature radius is relatively increased as it goes to both ends of the same width direction so that the directivity from the center part It can be set as the structure which narrows.

  This is the same whether the curved surface shape is a curved surface having a single curvature radius or a curved surface having a plurality of curvature radii. By adopting a configuration in which the curved surface shape is changed in the width direction in this way, a region where the diagnostic depth is shallow by electronically deflecting or converging an ultrasonic beam using a plurality of piezoelectric elements 1 at the center in the width direction. On the other hand, since the region having a deep diagnosis depth is mainly used at the end portion in the width direction, the ultrasonic wave can be effectively used up to the end portion.

  In the present embodiment, the curved surface shape on the subject side of the acoustic matching layer 2 is configured by curved surfaces having a plurality of curvature radii in the width direction and the arrangement direction, and the curvature radii are respectively in the width direction and the arrangement direction. Although the mode of changing along the direction is also shown, it is possible to change the radius of curvature only along one of the width direction and the arrangement direction, or simultaneously change along both directions. It is also possible.

  Similarly, in the aspect in which the curved surface shape along the arrangement direction is changed along the width direction orthogonal thereto, either alone or between changes in the curvature radius of the curved surface along the width direction of the surface shape. Even if it exists, it can apply even if both are combined. These changes in the curved surface shape can be selected according to the purpose of use.

  As mentioned above, although each embodiment of the ultrasonic probe concerning this invention has been described, this invention also includes the ultrasonic diagnostic apparatus which uses these ultrasonic probes. FIG. 9 shows an outline thereof. In the figure, the ultrasonic diagnostic apparatus 50 is configured such that the ultrasonic probe 10 described in each embodiment is electrically connected to the diagnostic apparatus main body 30 via the cable 25. Yes. The ultrasonic probe 10 is applied to the surface of the subject 15, and a voltage pulse drive signal is sent from the diagnostic apparatus main body 30 to the ultrasonic probe 10. This drive signal is transmitted to the piezoelectric element 1 via the electrode 7 (see FIG. 1) of the ultrasonic probe 10 and converted into ultrasonic waves. The ultrasonic wave transmitted to the subject 15 is reflected inside the body, and a part of the reflected echo is received by the piezoelectric element 1. Here, the reflected wave is converted into an electric signal and input to the ultrasonic diagnostic apparatus main body 30. The input reception signal is subjected to signal processing in the ultrasonic diagnostic apparatus main body 30 and output to a display device 35 such as a CRT as a tomographic image, for example.

  The subject 15 is not limited to a human body, and may be a living body such as another animal, and the ultrasonic diagnostic apparatus 50 can be used for the purpose of internal flaw detection for materials and structures.

  The ultrasonic probe according to the present invention can be used in various medical fields for performing ultrasonic diagnosis of a subject such as a human body, and in industrial fields for the purpose of internal flaw detection of materials and structures.

It is a perspective view which shows the ultrasonic probe of embodiment concerning this invention. FIG. 2 is a partial enlarged cross-sectional view in the piezoelectric element width direction of the ultrasonic probe shown in FIG. 1. FIG. 2 is a partial enlarged cross-sectional view of the ultrasonic probe shown in FIG. 1 in the direction in which piezoelectric elements are arranged. It is a perspective view which shows the other aspect of the ultrasonic probe of embodiment concerning this invention. FIG. 5 is a partial enlarged cross-sectional view of the ultrasonic probe shown in FIG. 4 in the piezoelectric element width direction. FIG. 5 is a partial enlarged cross-sectional view of the ultrasonic probe shown in FIG. 4 in the direction in which the piezoelectric elements are arranged. It is a partial expanded sectional view of the piezoelectric element width direction of the ultrasonic probe of other embodiment concerning this invention. It is a partial expanded sectional view of the piezoelectric element arrangement | positioning direction of the ultrasonic probe of other embodiment concerning this invention. 1 is a schematic view of an ultrasonic diagnostic apparatus using an ultrasonic probe according to the present invention. It is a schematic perspective view which shows the structure of the ultrasonic probe by a prior art. It is a schematic perspective view which shows the structure of the acoustic matching layer which the acoustic impedance by a prior art inclines continuously.

Explanation of symbols

1. 1. piezoelectric element, 2. acoustic matching layer; Acoustic lens, 4. 5. Back load material, 6. ground electrode; 7. Signal electrode 10. signal electrical terminal; 10. Ultrasonic probe, Piezoelectric element, 12. 12. acoustic matching layer; Acoustic lens, 14. Back load material, 15. Subject, 20. Ultrasonic probe, 22. Acoustic matching layer, 22a. A first acoustic matching material, 22b. 25. second acoustic matching material; Cable, 30. 35. diagnostic device body Display device, 50. Ultrasonic diagnostic equipment.

Claims (12)

A plurality of arranged piezoelectric elements that transmit and receive ultrasonic waves to and from the subject;
An acoustic matching layer provided on the subject-side front surface of the piezoelectric element;
A back load material provided on the back surface of the piezoelectric element on the opposite side of the acoustic matching layer with respect to the piezoelectric element;
In the ultrasonic probe composed of a pair of electrodes provided on the front surface and the back surface of the piezoelectric element,
The acoustic impedance of the acoustic matching layer continuously changes in the thickness direction from a value close to the piezoelectric element in the piezoelectric element side portion to a value close to the subject in the subject side portion, The object-side surface shape of the acoustic matching layer corresponding to each of the piezoelectric elements is formed in a curved shape along the arrangement direction of the plurality of piezoelectric elements and the width direction orthogonal thereto, and the acoustic matching layer includes An ultrasonic probe characterized in that an ultrasonic beam is diffused in the arrangement direction and converged in the width direction.   The ultrasonic probe according to claim 1, wherein the acoustic matching layer has a thickness of at least a half wavelength or more of a use frequency band of an ultrasonic wave generated by the piezoelectric element.   When the sound velocity of the subject side portion of the acoustic matching layer is Cml and the sound velocity of the subject is Cb, when Cml <Cb, the curved surface along the arrangement direction with respect to the subject is concave, and along the width direction. Each curved surface is formed in a convex shape, and when Cml> Cb, the curved surface along the arrangement direction with respect to the subject is formed in a convex shape, and the curved surface along the width direction is formed in a concave shape. The ultrasonic probe according to claim 1 or 2.   The curved surface along the arrangement direction is composed of a combination of curved surfaces having a plurality of curvature radii, and the plurality of curvature radii vary along the arrangement direction. Sonic probe.   The change in the plurality of radii of curvature is such that the radius of curvature is relatively large at a position corresponding to the central portion of each voltage element in the arrangement direction, and the radius of curvature is relative to each other in the arrangement direction. The ultrasonic probe according to claim 4, wherein the ultrasonic probe is formed so as to gradually become smaller.   The ultrasonic probe according to claim 3, wherein the shape of the curved surface along the arrangement direction changes along the width direction.   The curved surface along the arrangement direction is composed of a curved surface having a single radius of curvature or a combination of curved surfaces having a plurality of curvature radii, and the change in the shape of the curved surface along the width direction is at the center in the width direction. The radius of curvature is relatively small at a corresponding position, and the radius of curvature gradually increases gradually from the center to both ends in the width direction. The described ultrasonic probe.   The curved surface along the width direction is composed of a combination of curved surfaces having a plurality of curvature radii, and the plurality of curvature radii vary along the width direction. Sonic probe.   The change in the plurality of radii of curvature is formed such that the radius of curvature is relatively small at the center in the width direction, and the radius of curvature gradually increases gradually from the center to both ends in the width direction. The ultrasonic probe according to claim 8, wherein the ultrasonic probe is provided.   The acoustic matching layer includes a first layer in which a plurality of conical or polygonal cone-shaped first acoustic matching materials having an acoustic impedance substantially equal to that of the piezoelectric element are arranged densely so that the cones are in the same direction; A second acoustic matching material having an acoustic impedance substantially equal to that of the subject and a combination of the first layer and the second layer in which the gap portion of the first layer is filled in the thickness direction, or an acoustic close to the subject An impedance resin is filled with powder having an acoustic impedance substantially equal to that of the piezoelectric element and the powder filling degree is inclined in the thickness direction in the resin. The ultrasonic probe according to any one of Items 1 to 9.   The ultrasonic probe according to any one of claims 1 to 10, wherein the acoustic matching layer is divided in correspondence with each of the plurality of piezoelectric elements. An ultrasound probe that transmits and receives ultrasound to and from the subject;
A diagnostic apparatus that is electrically connected to the ultrasound probe, transmits a drive signal to the ultrasound probe, processes the electrical signal from the ultrasound probe, and outputs a diagnosis result In an ultrasonic diagnostic apparatus composed of a main body,
The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic probe is the ultrasonic probe according to claim 1.

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