JP2007124220A - Ultrasonic probe and ultrasonic diagnostic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To give sound pressure weighting in a short axis direction of a piezo-electric layer, and to adjust sound pressure distribution of the short axis direction which is input into a specimen to be desired sound pressure weighting. <P>SOLUTION: The sound pressure distribution of the short axis direction which is input into the specimen is adjusted to be desired sound pressure distribution; by forming a vibrator 2 which transceives an ultrasonic wave with the specimen comprising a piezo-electric layer 5 which transceives the ultrasonic wave, an acoustic matching layer 6 arranged in an ultrasonic radiation side of the piezo-electric layer, and a backing layer 7 arranged in a back face side of the piezo-electric layer; giving the sound pressure weighting in the short axis direction of the piezo-electric layer; and forming sound impedance of the acoustic matching layer 6 and the backing layer 7 with the distribution along the short axis direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe and an ultrasonic diagnostic apparatus in which a plurality of transducers for transmitting and receiving ultrasonic waves to and from a subject are arranged, and in particular, an ultrasonic transducer having transducers weighted with sound pressure in the minor axis direction. It relates to an acoustic probe.

  The ultrasonic probe is formed by arranging a plurality of transducers that convert drive signals into ultrasonic waves and enter the subject, and receive reflected echoes generated from the subject and convert them into received signals. Yes.

  As such an ultrasonic probe, one in which sound pressure is weighted in the minor axis direction of a transducer is known (for example, see Patent Document 1). According to this, the piezoelectric layer of the vibrator for transmitting and receiving ultrasonic waves is divided into a plurality of piezoelectric bodies, a filler is disposed between the piezoelectric bodies, and the piezoelectric body area distribution on the ultrasonic radiation surface Are formed so as to become smaller from the center in the minor axis direction toward both ends. Thereby, according to the area distribution of the piezoelectric body, the sound pressure of the ultrasonic wave incident on the subject can be weighted, and the side lobe can be suppressed to obtain a high quality image.

JP 2005-502437 A

  However, when the sound pressure distribution is provided in the minor axis direction of the piezoelectric layer as in the above-described conventional technique, the acoustic impedance of the piezoelectric layer varies along the minor axis direction accordingly. As a result, the sound pressure distribution of the ultrasonic wave incident on the subject does not correspond to a desired sound pressure weighting, and there is a problem that side lobes cannot be sufficiently suppressed.

  It is an object of the present invention to provide sound pressure weighting in the minor axis direction of a piezoelectric layer and adjust the sound pressure distribution in the minor axis direction incident on the subject to a desired sound pressure weighting.

  In order to solve the above-described problem, the ultrasonic probe of the present invention includes a plurality of transducers that transmit and receive ultrasonic waves to and from a subject, and the transducer includes a piezoelectric layer that transmits and receives ultrasonic waves; And an acoustic matching layer disposed on the ultrasonic radiation side of the piezoelectric layer, and the acoustic matching layer is formed with different acoustic impedances along the minor axis direction.

  That is, since the acoustic impedance of the piezoelectric layer is higher than the acoustic impedance of the subject, an acoustic matching layer is provided in order to make the ultrasonic wave radiated from the piezoelectric layer efficiently enter the subject. Therefore, if the acoustic impedance of the piezoelectric layer varies along the minor axis direction by weighting the sound pressure distribution in the minor axis direction of the piezoelectric layer, the acoustic impedance of the acoustic matching layer in the minor axis direction is adjusted. Thus, the sound pressure distribution in the minor axis direction incident on the subject can be adjusted to a desired sound pressure weighting.

  In this case, the acoustic matching layer is composed of a first matching layer on the piezoelectric layer side and a second matching layer on the subject side of the first matching layer, and the acoustic impedance of each matching layer in the minor axis direction. It is desirable to vary along. According to this, the ultrasonic wave can be incident on the subject more efficiently and adjusted to the desired sound pressure weighting.

  In addition, a plurality of transducers that transmit and receive ultrasonic waves to and from the subject are arranged, and the transducers have a piezoelectric layer that transmits and receives ultrasonic waves and a backing layer disposed on the back side of the piezoelectric layer. And the said subject can be solved also by making the acoustic impedance of a backing layer differ along a short-axis direction. That is, the ultrasonic wave generated in the piezoelectric layer is also radiated to the back side, and the reflectance of the ultrasonic wave radiated to the back side depends on the acoustic impedance of the backing layer. For example, if the acoustic impedance of the backing layer is reduced, the reflectance of the ultrasonic wave is increased, and the sensitivity of the piezoelectric layer is increased. In other words, the sound pressure of the ultrasonic wave radiated from the piezoelectric layer increases. Therefore, by adjusting the acoustic impedance in the short axis direction of the backing layer, it is possible to adjust the sound pressure distribution in the short axis direction incident on the subject to a desired sound pressure weighting.

  Further, it is preferable to combine the acoustic impedance in the minor axis direction in the acoustic matching layer and the acoustic impedance in the minor axis direction in the backing layer.

  According to the present invention, sound pressure weighting can be provided in the minor axis direction of the piezoelectric layer, and the sound pressure distribution in the minor axis direction incident on the subject can be adjusted to a desired sound pressure weighting.

Embodiments of an ultrasonic probe to which the present invention is applied will be described below with reference to the drawings.

  FIG. 1 is a perspective view showing the configuration of the ultrasonic probe according to the first embodiment of the present invention. Here, in the following embodiments, the arrangement direction of the vibrators is referred to as a major axis direction, and a direction orthogonal to the major axis direction is referred to as a minor axis direction. In addition, the direction in which ultrasonic waves are radiated from the vibrator toward the subject is referred to as an ultrasonic radiation direction, and the direction on the back side of the vibrator is referred to as a back direction.

  The ultrasonic probe 1 includes a plurality of transducers 2 that transmit and receive ultrasonic waves to and from the subject, and each transducer 2 is substantially separated by a separating material 3 that suppresses ultrasonic crosstalk. Has been. A common acoustic lens 4 is disposed on the subject side of the vibrator 2 and the separating material 3. The vibrator 2 includes a piezoelectric layer 5 that transmits and receives ultrasonic waves, an acoustic matching layer 6 that is disposed on the ultrasonic radiation side of the piezoelectric layer 5, and a backing layer 7 that is disposed on the back side of the piezoelectric layer 5. Composed. The backing layer 7 has a portion separated by the separating material 3 so as to correspond to each vibrator 2 and a base portion provided in common to all the vibrators 2.

  FIG. 2 shows a longitudinal sectional view of the piezoelectric layer 5 in the short axis direction, and FIG. 3 shows a view of the piezoelectric layer 5 viewed from the ultrasonic radiation surface side. As shown in these drawings, the piezoelectric layer 5 is divided into a plurality of piezoelectric bodies 11 (11-1 to 11-m) that transmit and receive ultrasonic waves. A filler 12 is disposed between the divided columnar piezoelectric bodies 11. Each piezoelectric body 11 is formed to have a distribution such that the area of the ultrasonic radiation surface decreases from the center in the short axis direction toward both ends. For example, the width of the filler 12 at both ends in the minor axis direction is 60 μm, and the width of the piezoelectric body 11 is 40 μm. In addition, the width of the filler 12 in the central portion in the minor axis direction is 40 μm, and the width of the piezoelectric body 11 is 60 μm. That is, the width of the filler 12 and the width of the piezoelectric body 11 are set to 40 μm to 60 μm along the short axis direction so that the total value of the width of the pair of adjacent fillers 12 and the piezoelectric body 11 becomes 100 μm. To do. A material such as piezoelectric ceramics PZT, PZLT, piezoelectric single crystal PZN-PT, PMN-PT, or organic piezoelectric material PVDF can be used for the piezoelectric body 11. Further, epoxy, silicon, or the like can be used for the filler 12.

  The acoustic lens 4 has a convex surface that bulges toward the subject side, and focuses ultrasonic waves transmitted and received between the piezoelectric layer 5 and the subject. The acoustic lens 4 is formed using a material (for example, silicon rubber) whose acoustic impedance is close to that of the subject and whose sound speed is slower than that of the subject.

  Next, the acoustic matching layer 6 which is a feature of the present embodiment will be described with reference to FIG. FIG. 5 is a longitudinal sectional view of the acoustic matching layer 6, the piezoelectric layer 5, and the backing layer 7 in the minor axis direction. As described above, the area distribution of the piezoelectric body 11 on the ultrasonic radiation surface is formed so as to decrease from the central portion in the short axis direction toward both ends. In accordance with this area distribution, the acoustic matching layer 6 is provided with a plurality of columnar ceramics 13 having an area corresponding to the area of each piezoelectric body 11 on the ultrasonic radiation side of the piezoelectric body 11. A resin 14 is disposed between them. The thickness of the acoustic matching layer 6 is ¼ of the wavelength of the center frequency of the ultrasonic wave to attenuate the reflected wave in the piezoelectric layer 5 to realize a wide band. For the ceramic 13, alumina, silicon, zirconia, or the like, or a material obtained by mixing these materials can be used. The resin 14 can be made of polyurethane, epoxy, silicon, or a mixture of these.

  The operation of the first embodiment configured as described above will be described next. According to the piezoelectric layer 5 of the present embodiment, the area of the ultrasonic radiation surface of each columnar piezoelectric body 11 has a distribution that decreases from the center in the minor axis direction toward both ends. The distribution becomes smaller from the center in the minor axis direction toward both ends. As a result, if the electric energy applied to the piezoelectric layer 5 is constant in the minor axis direction, the sound pressure distribution of the ultrasonic wave radiated from the piezoelectric layer 5 is convex along the minor axis direction as shown in FIG. Become weighted. When ultrasonic waves having this sound pressure distribution are incident on the subject, side lobes can be reduced and image quality can be improved.

  By the way, in general, the acoustic impedance of the piezoelectric layer 5 is very high compared to the acoustic impedance of the subject. Therefore, the ultrasonic wave radiated from the piezoelectric layer 5 is reflected on the subject surface due to the difference in acoustic impedance, and the subject is efficiently covered. It will not enter the specimen. Therefore, the acoustic matching layer 6 is provided between the piezoelectric layer 5 and the subject, impedance matching is performed, and ultrasonic waves are efficiently incident on the subject. Therefore, the acoustic impedance of the conventional acoustic matching layer is selected to be, for example, a value between the piezoelectric layer and the acoustic impedance of the subject, and has a constant acoustic impedance in the minor axis direction as shown in FIG. It was adjusted to.

  However, if there is an acoustic impedance distribution in the minor axis direction of the piezoelectric layer 5, the acoustic impedance matching is lost, and the sound pressure distribution incident on the subject is different from the sound pressure distribution weighted by the piezoelectric layer 5.

  Therefore, in this embodiment, the acoustic matching layer 6 is composed of a plurality of columnar ceramics 13 and a resin 14 disposed between the ceramics 13. In particular, the columnar cross section of each ceramic 13 has an area corresponding to the area of each piezoelectric body 11 of the piezoelectric layer 5. Thereby, as shown in FIG. 7, the acoustic impedance in the minor axis direction of the acoustic matching layer 6 can be matched with the acoustic impedance distribution in the minor axis direction of the piezoelectric layer 5. That is, the acoustic impedance of the acoustic matching layer 6 is formed so as to decrease from the center in the short axis direction toward both ends. As a result, the sound pressure distribution incident on the subject can be matched with the sound pressure distribution weighted by the piezoelectric layer 5, and the sound pressure distribution in the short axis direction incident on the subject is adjusted to a desired sound pressure weighting. be able to.

  A second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a longitudinal sectional view of the acoustic matching layer 6, the piezoelectric layer 5, and the backing layer 7 in the minor axis direction. Except for the acoustic matching layer, the description is omitted because it is the same as that of the first embodiment.

  In this example, the acoustic matching layer 6 of Example 1 is arranged on the first matching layer 6-1 arranged on the piezoelectric layer 5 side and the second arranged on the subject side of the first matching layer. This is a two-layer structure with the matching layer 6-2. In the first matching layer 6-1, a plurality of columnar ceramics 13 having an area corresponding to the area of each piezoelectric body 11 is disposed on the ultrasonic radiation side of the piezoelectric body 11, and a resin is interposed between the ceramics 13. 14 is formed. In the second matching layer 6-2, a plurality of columnar ceramics 17 having an area corresponding to the area of each ceramic 13 is arranged on the subject side of the ceramic 13, and a resin 18 is arranged between the ceramics 17. It is formed.

  Also in the present embodiment, it is possible to adjust the sound pressure distribution in the minor axis direction to a desired sound pressure weighting as in the first embodiment. Furthermore, since the acoustic matching layer has a two-layer structure as in this embodiment, ultrasonic waves can be incident on the subject more efficiently.

  A third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a longitudinal sectional view of the acoustic matching layer 6, the piezoelectric layer 5, and the backing layer 7 in the minor axis direction. In this embodiment, the backing layer has a feature. Except for the backing layer, the structure is the same as that of the embodiment 1, and the description is omitted.

  As described above, the area distribution of the piezoelectric body 11 on the ultrasonic radiation surface is formed so as to decrease from the central portion in the short axis direction toward both ends. In accordance with this, the backing layer 7 is provided with a plurality of columnar rubber members 19 having an area corresponding to the area of each piezoelectric member 11 on the back side of the piezoelectric member 11, and a resin 20 between the rubber members. Is formed.

The operation of the third embodiment configured as described above will be described next. The piezoelectric layer 5 of the present embodiment is weighted in a convex manner along the minor axis direction as in the first embodiment, and the acoustic impedance is not uniform along the minor axis direction as shown in FIG. In accordance with the convex sound pressure weighting, an acoustic impedance distribution is generated in the minor axis direction.
By the way, in general, the acoustic impedance of the piezoelectric layer 5 is very high compared to the acoustic impedance of the subject. Therefore, the ultrasonic wave radiated from the piezoelectric layer 5 is reflected on the subject surface due to the difference in acoustic impedance, and the subject is efficiently covered. It will not enter the specimen. Since the reflected ultrasonic waves continue to vibrate inside the piezoelectric layer 5, the pulse width of the ultrasonic waves becomes long, and the distance resolution in the subject decreases. Even if the acoustic matching layer 6 is provided between the piezoelectric layer 5 and the subject, impedance matching is performed, and ultrasonic waves are efficiently incident on the subject, the distance resolution is not sufficient. Therefore, the backing layer 7 having a constant acoustic impedance in the minor axis direction is provided on the back side of the piezoelectric layer 5, and the ultrasonic wave radiated in the back direction is adjusted by adjusting the value of the acoustic impedance.

  However, if there is an acoustic impedance distribution in the minor axis direction of the piezoelectric layer 5, the acoustic impedance matching is lost, and the sound pressure distribution incident on the subject is different from the sound pressure distribution weighted by the piezoelectric layer 5.

  Therefore, in this embodiment, the backing layer 7 is composed of a plurality of columnar rubber materials 19 and a resin 20 disposed between the rubber materials 19. In particular, the columnar cross section of each rubber material 19 has an area corresponding to the area of each piezoelectric body 11 of the piezoelectric layer 5. Thereby, the acoustic impedance of the backing layer 7 decreases from the center in the minor axis direction toward both ends, so that it can be matched with the acoustic impedance in the minor axis direction of the piezoelectric layer 5. As a result, the sound pressure distribution incident on the subject can be matched with the sound pressure distribution weighted by the piezoelectric layer 5, and the sound pressure distribution in the short axis direction incident on the subject is adjusted to a desired sound pressure weighting. be able to.

  A fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a longitudinal sectional view of the acoustic matching layer 6, the piezoelectric layer 5, and the backing layer 7 in the minor axis direction. This example has a structure in which the acoustic matching layer of Example 1 and the backing layer of Example 3 are combined. Except for the acoustic matching layer and the backing layer, the description is omitted because it is the same as that of the first embodiment.

  As in this embodiment, the acoustic impedance in the minor axis direction of the acoustic matching layer 6 and the backing layer 7 is matched with the acoustic impedance distribution in the minor axis direction of the piezoelectric layer 5 so that it can be incident on the subject more easily. It is possible to adjust the sound pressure distribution in the minor axis direction to a desired sound pressure weighting.

  Of course, since the principle of the invention is the same between the first embodiment and the second embodiment, the problem of the present invention can be solved by the combination of the second embodiment and the third embodiment.

  As described above, in the first to fourth embodiments of the present invention, the piezoelectric layer 5 is so-called 1 in which the columnar piezoelectric bodies 11 are arranged in the major axis direction and the minor axis direction, and the filler 12 is disposed between the piezoelectric bodies 11. It demonstrated using -3 type | mold composite structure. However, the present invention is not limited to this. For example, a plurality of plate-like piezoelectric bodies extending over the entire length in the major axis direction are arranged in the minor axis direction, and a filler is disposed between the piezoelectric bodies, so that each piezoelectric substance is substantially separated. A so-called 2-2 type composite structure may also be used. The present invention can also be applied to a so-called 0-3 type composite structure in which a piezoelectric layer is integrally formed by blending a powdery piezoelectric material with a base material. Sound pressure weighting in the case of this 0-3 type composite structure can be realized by changing the concentration of the piezoelectric material along the minor axis direction. That is, regardless of the structure, the present invention can be applied if the piezoelectric layer is formed so that the acoustic impedance becomes smaller from the central part in the minor axis direction toward both ends.

  Further, the acoustic matching layer 6 is not limited to the structure of the embodiment. For example, a metal powder (for example, tungsten) may be blended with a resin (for example, epoxy) so that the blend ratio increases from both ends in the minor axis direction toward the center. In other words, the effect of the present invention can be exhibited if the acoustic impedance is different along the minor axis direction.

  Similarly, the structure of the backing layer 7 may be formed so that the acoustic impedance varies along the minor axis direction. For example, by blending resin (for example, epoxy), microballoon, and metal powder (for example, tungsten) and increasing the metal powder from both ends in the minor axis direction toward the center, acoustic impedance and attenuation factor can be reduced. adjust.

  Next, an outline of an ultrasonic diagnostic apparatus configured using an ultrasonic probe to which the present invention is applied will be described with reference to FIG.

  The ultrasonic diagnostic apparatus 24 receives a transmission circuit 25 that supplies a pulse signal for driving the ultrasonic probe 1 via a signal line, a reception signal output from the ultrasonic probe 1, and the reception signal. Are provided with a receiving circuit 26 for forming an ultrasonic image and an image display 27 for displaying an ultrasonic image output from the receiving circuit 26.

  The operations of the ultrasonic probe 1 and the ultrasonic diagnostic apparatus 24 configured as described above will be described. First, the acoustic lens 4 side of the ultrasonic probe 1 is brought into contact with the body surface of the subject. When a pulse signal for driving the ultrasound probe 1 is output from the transmission circuit 25, the pulse signal is supplied to the piezoelectric layer 5, for example. When the supplied pulse signal is input to the piezoelectric body 11 through a pair of electrodes sandwiching the ultrasonic radiation side and the back surface side of the piezoelectric layer 5, the piezoelectric body 11 moves in the ultrasonic radiation direction and the back surface direction of the piezoelectric layer 5. It expands and contracts. Thereby, an ultrasonic wave is generated and emitted toward the subject. The reflected echo generated from the subject is received by the piezoelectric body 11 through the electrode and converted into a received signal. The converted received signal is output to the receiving circuit 26 through the signal line, and the receiving circuit 26 performs an ultrasonic image forming process such as amplification and phasing addition. The ultrasonic image output from the receiving circuit 26 is displayed on an image display 27 that is a monitor.

It is a figure which shows the structure of the ultrasonic probe to which this invention is applied. It is a figure which shows the longitudinal cross-section of the short axis direction of the piezoelectric layer of the ultrasonic probe of FIG. It is the figure which looked at the piezoelectric layer of FIG. 2 from the ultrasonic radiation surface side. It is a figure which shows the sound pressure distribution of the ultrasonic wave radiated | emitted from the piezoelectric layer of FIG. It is a figure which shows Example 1 of the ultrasonic probe to which this invention is applied. It is a figure which shows the acoustic impedance distribution of the piezoelectric layer and acoustic matching layer before applying this invention. It is a figure which shows the acoustic impedance distribution of the piezoelectric layer and acoustic matching layer after applying this invention. It is a figure which shows Example 2 of the ultrasonic probe to which this invention is applied. It is a figure which shows Example 3 of the ultrasonic probe to which this invention is applied. It is a figure which shows Example 4 of the ultrasonic probe to which this invention is applied. It is a figure which shows the structure of the ultrasonic probe and ultrasonic diagnostic apparatus to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic probe 2 Vibrator 3 Separation material 4 Acoustic lens 5 Piezoelectric layer 6 Acoustic matching layer 7 Backing layers 11-1 to 11-m Piezoelectric body 12 Filling material 13, 17 Ceramics 14, 18, 20 Resin 19 Rubber material 24 Ultrasonic Diagnostic Device 25 Transmission Circuit 26 Reception Circuit 27 Image Display

Claims (11)

A plurality of transducers that transmit and receive ultrasonic waves to and from the subject are arranged, and the transducer includes a piezoelectric layer that transmits and receives the ultrasonic waves and an acoustic matching disposed on the ultrasonic radiation side of the piezoelectric layer. An ultrasonic probe in which the acoustic matching layer is formed with different acoustic impedances along the minor axis direction. The acoustic matching layer includes a first matching layer on the piezoelectric layer side and a second matching layer on the subject side of the first matching layer, and the first matching layer and the second matching layer include The ultrasonic probe according to claim 1, wherein the ultrasonic probes are formed with different acoustic impedances along the minor axis direction. A plurality of transducers that transmit and receive ultrasonic waves to and from the subject are arranged, and the transducer includes a piezoelectric layer that transmits and receives the ultrasonic waves, and a backing layer disposed on the back side of the piezoelectric layer. And an ultrasonic probe in which the backing layer is formed with different acoustic impedances along the minor axis direction. A plurality of transducers that transmit and receive ultrasonic waves to and from a subject are arranged, and the transducers are disposed on the ultrasonic radiation side of the piezoelectric layer that transmits and receives the ultrasonic waves, and have a short axis An acoustic matching layer formed by varying the acoustic impedance along the direction, and a backing layer disposed on the back side of the piezoelectric layer and formed by varying the acoustic impedance along the minor axis direction. An ultrasonic probe. The piezoelectric layer has an acoustic impedance that decreases from the central portion in the short axis direction toward both ends, and the acoustic matching layer has an acoustic impedance that decreases from the central portion in the short axis direction toward both ends. The ultrasonic probe according to claim 4. The piezoelectric layer has an acoustic impedance that decreases from the center in the minor axis direction toward both ends, and the acoustic matching layer includes a first matching layer on the piezoelectric layer side and a subject side of the first matching layer. 5. The acoustic impedance of each of the first matching layer and the second matching layer decreases from the center in the minor axis direction toward both ends. The ultrasonic probe described in 1. The ultrasonic probe according to claim 6, wherein the backing layer has an acoustic impedance that decreases from the center in the minor axis direction toward both ends. The piezoelectric layer is formed of a plurality of columnar piezoelectric bodies and a filler disposed between the piezoelectric bodies, and the area distribution of the piezoelectric body on the ultrasonic radiation surface is from the center in the minor axis direction to both ends. The ultrasonic probe according to claim 7, wherein the ultrasonic probe becomes smaller as it goes. The first matching layer is formed of a first ceramic disposed on the ultrasonic radiation side of the piezoelectric body and a first resin disposed on the ultrasonic radiation side of the filler, The second matching layer is formed of a second ceramic disposed on the subject side of the first ceramic and a second resin disposed on the subject side of the first resin. The ultrasonic probe according to claim 8, wherein: The ultrasonic wave according to claim 9, wherein the backing layer is formed of a rubber material disposed on a back surface side of the piezoelectric body and a resin disposed on a back surface side of the filler. Transducer. An ultrasonic diagnostic apparatus comprising the ultrasonic probe according to any one of claims 1 to 10.

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