JP2002152890A - Ultrasonic wave probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic wave probe the focus of a vibrator of which in the length direction is enhanced. SOLUTION: An acoustic matching layer 56 interposed between a piezoelectric vibrator 52 (acoustic impedance Z0) and a packing member 54 (acoustic impedance ZB) is divided into a middle region 70 (acoustic impedance ZC) and an end region 72 (acoustic impedance ZE) in the length direction of the piezoelectric vibrator 52 and a relation of ZB<Z0 and ZC<ZE<Z0 holds. Thus, the absorption of an ultrasonic wave by the packing member 54 is weaker than that by the end region 72 in the middle region 70, the acoustic power is directed toward a subject, and the absorption to the packing member 54 is promoted in the end region 72, the side lobe of the ultrasonic wave beam is reduced, the power of the main beam is increased and the beam width is narrowed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ultrasonic probe, and more particularly to an improvement in resolution of the ultrasonic probe.

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus employing an electronic scanning system, an electronic scanning array probe having an array-type vibrator section in which a number of small rectangular piezoelectric vibrators are arranged is used. .

FIG. 3 is a schematic perspective view showing a schematic structure of a conventional linear array probe. In this conventional linear array probe, a plurality of piezoelectric vibrators 2 are fixed on a backing material (back load material) 4 in an array direction. An acoustic matching layer 6 is provided between the piezoelectric vibrator 2 and the backing material 4.

Each piezoelectric vibrator 2 has a strip-like planar shape, and adjacent piezoelectric vibrators 2 are arranged in parallel with their long sides facing each other. Each of the piezoelectric vibrators 2 has a structure in which a positive electrode 10 and a negative electrode 12 are provided on the front and back surfaces of a piezoelectric body 8 made of a material such as piezoelectric ceramics, respectively. Lead wires (not shown) are connected to the positive electrode 10 and the negative electrode 12, and when a voltage pulse is applied to the piezoelectric vibrator 2 via these lead wires, the piezoelectric body 8 vibrates and vibrates. Ultrasonic waves are emitted to the subject located in front of the child array. On the other hand, when the ultrasonic wave reflected by the subject enters the front surface of the vibrator array, a voltage corresponding to the distortion due to the vibration is generated in the piezoelectric body 8 which resonates with the ultrasonic wave,
This is extracted as a voltage signal between the positive electrode 10 and the negative electrode 12.

[0005] The backing material 4 is made of a material such as rubber, supports the back surface of the piezoelectric vibrator 2, damps the vibration of the piezoelectric vibrator 2, absorbs unnecessary ultrasonic waves, and allows the probe to be tailed. It has the function of enabling transmission and reception of short pulse signals with little noise.

Here, the backing material 4 and the piezoelectric vibrator 2 generally have different acoustic impedances from each other, and reflection of ultrasonic waves occurs at the boundary. This reflection causes multiple reflections inside the piezoelectric vibrator 2 and contributes to the trailing of the pulse waveform. The acoustic matching layer 6 between the backing material 4 and the piezoelectric vibrator 2 is provided in order to reduce the reflection at this boundary surface, and the tailing becomes longer but the ultrasonic radiation to the front surface is reduced. It may be provided to increase.

[0007] The ultrasonic beam generated from the piezoelectric vibrator 2 is not formed in a perfect linear shape but is formed with a certain width. Further, not only the main beam but also side lobes which are radiated in directions other than the desired direction although the intensity is weaker than that are generated. As for the scanning direction of the vibrator array orthogonal to the long side of the piezoelectric vibrator 2, the beam can be satisfactorily focused in a desired direction by electronic focusing. However, the long side direction (elevation direction) of the piezoelectric vibrator 2 is Since electronic focusing is not performed, there is a problem that the resolution in this direction is low.

As a countermeasure against this problem, an acoustic lens 16 is conventionally provided on the front surface of the piezoelectric vibrator 2 via an acoustic matching layer 14.
Is provided.

[0009]

There is a problem that the suppression of the beam width in the elevation direction is not always sufficient with the acoustic lens 16 alone.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides an ultrasonic probe capable of suppressing side lobes, further narrowing the beam width of the transducer in the elevation direction, and improving resolution. The purpose is to do.

[0011]

In an ultrasonic probe according to the present invention, an acoustic matching layer interposed between a piezoelectric vibrator and a back load member has a central portion in the longitudinal direction of the piezoelectric vibrator. It is characterized in that the closer to the region, the lower the acoustic impedance of the back load material in acoustic absorption.

According to the present invention, the acoustic matching layer interposed between the piezoelectric vibrator and the back load material weakens the ultrasonic absorption effect of the back load material near the center of the piezoelectric vibrator, and conversely. The absorption effect becomes stronger near the end. In accordance with the spatial modulation of the absorption action by the back load material, the degree of concentration of the acoustic power on the front surface at the center increases. That is, in the distribution of the ultrasonic beam according to the present invention, the side lobe is suppressed, while the main beam component in the normal direction of the piezoelectric vibrator is increased.

[0013]

Next, a preferred embodiment of an ultrasonic probe according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic perspective view showing a schematic structure of a linear array probe according to the present invention. In this linear array probe, a vibrator portion including a piezoelectric vibrator 52 is provided on a backing material 54. An acoustic matching layer 56 is provided between the piezoelectric vibrator 52 and the backing material 54.
Is provided.

The vibrator portion has an array structure in which a large number of piezoelectric vibrators 52 are one-dimensionally arranged as shown in the figure. The piezoelectric vibrators 52 are configured to be driven independently of each other. The piezoelectric vibrators 52 are separated from each other, for example, as in the prior art, by initially integrating the piezoelectric body 58, the positive electrode 60, and the negative electrode 6.
2 is formed on the backing material 54 and then sliced in a direction orthogonal to the array direction. This can be realized by making each of the rectangular piezoelectric vibrators 52 an adjacent piezoelectric vibrator. 52 and the long sides thereof are arranged in parallel with each other. Incidentally, the width of the gap formed by the slices between the piezoelectric vibrators 52 is, for example, 0.2 mm.

The piezoelectric body 58 is formed using a piezoelectric ceramic plate such as PZT. The positive electrode 6
The negative electrode 62 is formed, for example, by depositing a metal film having a thickness of several thousand angstroms on both surfaces of the piezoelectric body 58 by a sputtering method.

A lead wire (not shown) is connected to the positive electrode 60 and the negative electrode 62, and a voltage pulse is applied to the piezoelectric vibrator 52 through these lead wires,
The piezoelectric body 58 vibrates, and ultrasonic waves are radiated to the subject located on the front surface of the vibrator array. On the other hand, when the ultrasonic wave reflected by the subject enters the front surface of the vibrator array, a voltage corresponding to the distortion caused by the vibration is generated in the piezoelectric body 58 which resonates with the ultrasonic wave, and this voltage is generated between the positive electrode 60 and the negative electrode 62. It is taken out as a voltage signal between them.

An acoustic lens 66 for converging an ultrasonic beam is provided on the front surface of the vibrator portion via an acoustic matching layer 64 for matching acoustic impedance with a living body as a subject, as in the prior art. As a result, acoustic coupling with a living body as a subject is improved, and beam focusing in the elevation direction is achieved.

In this probe, in order to further improve the focus in the elevation direction, the acoustic matching layer 56 on the back side is constituted by the central region 70 and the end region 72 having different acoustic impedances. Has features.

The acoustic impedance of the central region 70 and the end region 72 is determined such that the backing material 54 absorbs ultrasonic waves more in the end region 72 than in the central region 70. Also, here, the central region 70,
The two end regions 72 are provided symmetrically with respect to the center plane of the piezoelectric vibrator 52 in the elevation direction.

More specifically, the piezoelectric body 58 is made of a material such as piezoelectric ceramics as described above, has a relatively large acoustic impedance Z0, and the backing material 54 is a material such as rubber as in the conventional case. An acoustic impedance Z that is made of an integral and uniform material and is smaller than the piezoelectric body 58
Has B When ZB <Z0, the acoustic matching layer 56
When the acoustic impedance of each of the central region 70 and the end region 72 is represented by ZC and ZE, the acoustic impedance is smaller in the central region 70 than in the end region 72.
That is, the configuration is such that ZB <Z0 and ZC <ZE <Z0.

Ultrasonic waves generated by the piezoelectric vibrator 52 are less likely to enter the central region 70 than to the end region 72, and the acoustic power is directed toward the front of the probe in this region. That is, the acoustic power in the direction perpendicular to the center of the piezoelectric vibrator 52 in the elevation direction increases. On the other hand, the ultrasonic waves generated by the piezoelectric vibrator 52 are more likely to enter the end region 72 into the central region 70, and the absorption component of the acoustic power to the backing material 54 increases. That is, side lobes emitted from the piezoelectric vibrator 52 are suppressed. Thus, in the present probe, the directivity in the direction perpendicular to the center in the elevation direction is enhanced, and the focus in the elevation direction is improved.

The central region 70 and the end region 72 of the acoustic matching layer 56 are made of, for example, epoxy resin. The difference in acoustic impedance between the central region 70 and the end region 72 is realized by using different types of resins or by using different materials mixed with the resins. The acoustic matching layer 56 has a thin thickness on the order of the wavelength of the ultrasonic wave, and is formed by applying and solidifying a resin on the surface of the backing material 54. It is also easy to form a plurality of regions including a partial region 70 and an end region 72.

Adjusting the degree of absorption by the backing material 54 on the surface of the acoustic matching layer 56 which is in close contact with the back surface of the piezoelectric vibrator 52 is intended to direct the acoustic power in the central region 70 forward. In that the accompanying spread of the pulse in the time direction is suppressed, it is excellent in keeping the waveform of the ultrasonic pulse better than performing the adjustment on the surface of the backing material 54 that is separated from the piezoelectric vibrator 52. .

FIG. 2 is a schematic front view showing a schematic structure of a linear array probe according to another embodiment of the present invention, viewed from the array direction. This figure shows the acoustic matching layer 56
Is a first region 8 which is a central region in the elevation direction.
0 (acoustic impedance Z1), a third region 82 (acoustic impedance Z3) which is an end region, and a second region 84 (acoustic impedance Z2) located between the first and third regions. Have been. And, between these acoustic impedances, ZB <Z0 and Z1 <Z2
<Z3 <Z0, that is, the more the center of the piezoelectric vibrator 52 in the elevation direction, the more the backing material 54
The relationship is set so as to weaken the absorption of the ultrasonic wave into the light. With this configuration also, the effect of improving the focus of the ultrasonic beam in the elevation direction can be obtained. Similarly, the acoustic matching layer 56 may be divided into more regions such that the region closer to the center in the elevation direction weakens the absorption of ultrasonic waves into the backing material 54.

[0026]

According to the ultrasonic probe of the present invention, the acoustic impedance of the acoustic matching layer close to the piezoelectric vibrator is made different between the central region and the end region, and the acoustic impedance of the acoustic matching layer is changed to the backing material in the end region. By promoting the absorption of the ultrasonic wave and diverting the acoustic power forward in the central region, the effect of improving the directivity of the ultrasonic beam in the elevation direction with a good pulse waveform can be obtained. . In addition, since the acoustic matching layer is formed of a thin resin layer, it is easy to manufacture the acoustic matching layer separately in a plurality of regions having different acoustic impedances.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a schematic structure of a linear array probe according to a first embodiment of the present invention.

FIG. 2 is a schematic front view showing a schematic structure of a linear array probe according to a second embodiment of the present invention.

FIG. 3 is a schematic perspective view showing a schematic structure of a conventional linear array probe.

[Explanation of symbols]

52 piezoelectric vibrator, 54 backing material, 56, 64
Acoustic matching layer, 58 piezoelectric body, 60 positive electrode, 62 negative electrode, 66 acoustic lens, 70 central region, 72 end region.

Continued on the front page (72) Inventor Moriyuki Ishikawa 6-22-1, Mure, Mitaka-shi, Tokyo Aloka Inc. F-term (reference) 2G047 AC13 CA01 DB02 EA01 GB02 GB13 GB23 GB28 GB35 4C301 AA02 EE02 GB04 GB20 GB22 GB23 GB27 GB33 5D019 AA02 AA06 BB02 BB18 GG01 GG06

Claims (1)

[Claims] 1. A plurality of piezoelectric vibrators each having a strip shape and arranged in parallel with each other, and a back load member as an ultrasonic absorber provided on a side of the piezoelectric vibrator opposite to a side in contact with a subject. An ultrasonic probe having an acoustic matching layer interposed between the piezoelectric vibrator and the back load member, wherein the acoustic matching layer is located near a center in the longitudinal direction of the piezoelectric vibrator. An ultrasonic probe having an acoustic impedance that reduces the ultrasonic absorption effect of the back load member.