JPH0716280B2 - Ultrasonic probe - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic probe used in a medical ultrasonic diagnostic apparatus.

2. Description of the Related Art Recently, ultrasonic probes have been widely used in the fields of ultrasonic diagnostic equipment and the like. As a conventional ultrasonic probe, for example, the configuration described in Japanese Patent Laid-Open No. 55-35654 is known. Hereinafter, a conventional ultrasonic probe will be described with reference to FIG. A plurality of piezoelectric vibrators 101 divided into elongated rectangles are arranged on the surface of the back load material 102. The piezoelectric vibrator 101 is provided with an electrode (not shown), and the electrode is an electric terminal (not shown). Connected to the drive circuit via (). An acoustic matching layer 103 made of a glass material having a quarter wavelength thickness is adhered to the surface of the piezoelectric vibrator 101 divided into a plurality of pieces with an epoxy adhesive. At the time of this adhesion, the epoxy-based adhesive 104 flows into the gap formed by the side surface of each piezoelectric vibrator 101 and the surface of the back load material 102 sufficiently so that the adhesive 10
The acoustic matching layer 103 is adhered on the surface 4.

In this way, the gap between the piezoelectric vibrators 101 is filled with the epoxy resin adhesive 104 that is smaller than the acoustic impedance value of the acoustic matching layer 103, so that the piezoelectric vibrators 101 are acoustically discontinuously coupled. This prevents leakage of sound waves (acoustic crosstalk) to improve the lateral resolution of ultrasonic images.

The ideal for almost completely preventing acoustic crosstalk is that the acoustic impedance of each piezoelectric vibrator 101 has an extremely large difference in the acoustic impedance of the gap. That is, it is ideal that the air between the piezoelectric vibrators 101 has a very small acoustic impedance.

However, in forming the ultrasonic probe, it is very difficult to make the gap between the piezoelectric vibrators 101 to be air, and therefore some material is filled. Therefore, it is difficult to prevent acoustic crosstalk almost completely.
Therefore, in order to increase the difference between the acoustic impedance of each piezoelectric vibrator 101 and the acoustic impedance of the material with which the gap of each piezoelectric vibrator 101 is filled, this material has an acoustic impedance of about 3 × 10 ⁵ g / cm ² · S. The present situation is to use an epoxy adhesive that is small to some extent to reduce acoustic crosstalk.

As another method for reducing the acoustic crosstalk, a material having an extremely large sound wave attenuation coefficient is filled in the gap between the piezoelectric vibrators 101, and the acoustic crosstalk to the adjacent piezoelectric vibrators 101 is prevented by this filling material. It is considered that the piezoelectric vibrator 101 is attenuated so that the adjacent piezoelectric vibrator 101 does not leak. Thus, in order to prevent acoustic crosstalk, desirable characteristics of the material with which the gap of the piezoelectric vibrator 101 is filled are (1) a large difference from the acoustic impedance of the piezoelectric vibrator, that is, a small acoustic impedance value. (2) The sound wave attenuation coefficient is large.

Problems to be Solved by the Invention However, when an epoxy adhesive is used as a material for filling the gap of the piezoelectric vibrator 101, the acoustic matching layer 103 made of a glass material or the like is provided on the piezoelectric vibrator 101. At the same time as the bonding, the epoxy adhesive is applied to the piezoelectric vibrator.
Although there is an advantage in the manufacturing process that the gap of 101 can be filled, it is insufficient to prevent acoustic crosstalk between the piezoelectric vibrators 101. That is, the difference in acoustic impedance of the piezoelectric vibrator 101 (generally 20 × 10 ^{5 to} 35 × 10 ⁵ g / cm ² · S in the case of a piezoelectric ceramic vibrator such as PZT) is about one digit. The transmission coefficient related to the acoustic crosstalk from the piezoelectric vibrator 101 to the epoxy adhesive is approximately 15
It will be ~ 26%. Moreover, since the acoustic wave attenuation coefficient of the epoxy adhesive is as small as around 1 dB / mm at 3.0 MHz, the transmitted acoustic waves (crosstalk) can hardly be attenuated and propagate to the adjacent piezoelectric vibrator 101. Therefore, there is a problem that a predetermined ultrasonic beam pattern cannot be formed and characteristics such as lateral resolution required for the image quality of an ultrasonic image are deteriorated.

Therefore, in order to solve the above problems, the present invention intends to provide an ultrasonic probe capable of eliminating acoustic crosstalk and preventing characteristic deterioration such as lateral resolution of an ultrasonic image. It is a thing.

Means for Solving Problems The technical means of the present invention for solving the above problems are a piezoelectric vibrator, a back load material provided on one surface side of the piezoelectric vibrator, and the piezoelectric vibration. At least one of the piezoelectric vibrators is divided into a plurality of acoustic matching layers provided on the other side of the child, and a metal powder or a base material such as a rubber material or a synthetic resin is provided in the gap between the piezoelectric vibrators. It is a filler filled with powder such as insulating powder and plastic microballoons.

Effect With the above-described structure of the present invention, the material for filling the gap between the piezoelectric vibrators can be arbitrarily selected within a range of acoustic impedance smaller than that of the conventional epoxy adhesive, and the sound wave attenuation coefficient is 35%. It will be more than twice as large. Therefore, the difference in the acoustic impedance between the piezoelectric vibrator and the filling material can be increased, and the acoustic crosstalk with the adjacent piezoelectric vibrator can be reduced. Further, even if there is a slight amount of acoustic crosstalk, the acoustic wave attenuation coefficient of the filling material is large and can be attenuated by this filling material.

Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of the ultrasonic probe of the present invention. The piezoelectric vibrator 1 has electrodes (not shown) on both sides, and an electric terminal is taken out from one of the electrodes. The back load material 2 is provided on one surface side of the piezoelectric vibrator 1 by means such as pouring or adhesion. The piezoelectric vibrator 1 is divided into a plurality of pieces by machining or the like. The gap between the piezoelectric vibrators 1 is filled with the filler 3, and the two acoustic matching layers 4 and 5 are provided on the other surface side of the piezoelectric vibrator 1 by pouring or bonding means. An acoustic lens 6 is provided on the acoustic matching layer 5 as needed.

As the filler 3 to be filled in the gap of the piezoelectric vibrator 1, a rubber material mixed with two kinds of powder such as metal powder or insulating powder and microballoon is used. For example, if silicon rubber is used as the rubber material and tungsten powder and plastic microballoons are mixed in the weight ratio of 200% and 1.5% with respect to the base silicon rubber, respectively, and the filler 3 is manufactured, the acoustic impedance is At 1.06 × 10 ⁵ g / cm ² · S, the sound wave attenuation coefficient is about 40 dB / mm at 3 MHz.

Thus, due to the difference in acoustic impedance between the adjacent piezoelectric vibrators 1 as described above, propagation of sound waves to the adjacent piezoelectric vibrators 1 can be prevented and crosstalk can be reduced. Material 3 with an acoustic impedance of 1.06 × 10 ⁵ g / cm ² · S is used, while piezoelectric transducer 1 has an acoustic impedance of 20 × 10 ^{5 to} 35 × 10 ⁵ g / cm 2.
^{By using the 2} · S PZT ceramic material, the acoustic transmission coefficient between the piezoelectric vibrator 1 and the filler 3 is approximately 6 to
It becomes 10%, and it becomes 15 to 26% when the conventional epoxy adhesive is used as the filler. Therefore, it is clear that the acoustic crosstalk can be greatly reduced according to the present embodiment. Further, the acoustic attenuation coefficient of the filler 3 of the above-mentioned embodiment is 40 dB / mm at 3 MHz, which is about 40 times larger than the acoustic attenuation coefficient of 1 dB / mm of the filler using the conventional epoxy adhesive. Transmission coefficient of crosstalk 6-10%
The minutes can be almost completely damped with the filler 3.
Therefore, by using the filler 3 of the above-described embodiment, it is possible to almost eliminate acoustic crosstalk between the adjacent piezoelectric vibrators 1 and obtain an ultrasonic image with high lateral resolution.

The acoustic impedance and sound wave attenuation coefficient are 0.7 × 10 ⁵ g / cm 2 when the weight ratio of tungsten powder to silicon rubber is 100% and that of plastic micro-balloon is 2% in the same weight ratio. ²
S, 50 dB / mm (3 MHz), and the acoustic impedance and sound attenuation coefficient when tungsten powder and plastic microballoons were mixed in the silicone rubber at a weight ratio of 400% and 0.8%, respectively, were 2 × 10 ⁵ g / cm ²・ S,
The value is 35 dB / mm. In this way, for silicone rubber,
By varying the amount of tungsten powder and plastic microballoons mixed, the sound wave attenuation coefficient is 35 ~.
50dB / mm, acoustic impedance 0.7 × 10 ⁵ to 2 × 10 ⁵ g / cm
The filler 3 in the range of ² · S can be obtained, and in the present invention, it may be appropriately selected in this range.

Further, in the above-mentioned embodiment, the case where the silicone rubber is used as the base material of the filler 3 has been described. In addition to this, urethane rubber, butyl rubber, neoprene rubber or synthetic resin epoxy resin, urethane resin or the like may be used. What can be done is clear from their properties.

Further, in the above embodiment, the case where the tungsten powder is used as the powder such as the metal powder or the insulating powder is described.
In addition to these, it is clear from those characteristics that tantalum powder, ferrite powder, zinc powder, silicon carbide powder, tungsten carbide powder, iron powder and the like can be used. Of course, it is also clear that two or more kinds of metal powder or insulating powder can be used.

Further, the acoustic matching layer 4 on the piezoelectric vibrator 1 side in the above embodiment
It is also possible to divide into a plurality of parts together with the piezoelectric vibrator and fill the gap with the filling material 3 similarly to the piezoelectric vibrator 1.

Further, in the above-mentioned embodiment, the so-called array type ultrasonic probe in which the piezoelectric vibrators 1 are linearly arranged has been described.
In addition to the above, the present invention can be applied to various types such as arranging the piezoelectric vibrators in an arc shape, arranging two-dimensionally, or arranging in a ring shape.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, the piezoelectric vibrator, the back load material provided on one side of the piezoelectric vibrator, and the other side of the piezoelectric vibrator are provided. One or more acoustic matching layers are provided, at least the piezoelectric vibrator is divided into a plurality of pieces, and a rubber material, a base material such as a synthetic resin, a powder such as a metal powder or an insulating powder, and a plastic are provided in the gap. The filling material is filled with microballoons. Since the acoustic impedance of the filling material is small in this way, the difference from the acoustic impedance of the piezoelectric vibrator is large, and because the sound wave attenuation coefficient is also large, acoustic crosstalk between the piezoelectric vibrators divided into a plurality of parts. Can be extremely small. Therefore, it becomes possible to form a predetermined ultrasonic beam pattern, it is possible to improve the characteristics of lateral resolution required for ultrasonic image quality, and it is possible to obtain an ultrasonic probe having high-resolution characteristics. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the ultrasonic probe of the present invention, and FIG. 2 is a sectional view of a conventional ultrasonic probe. 1 ... Piezoelectric vibrator, 2 ... Back load material, 3,4 ... Acoustic matching layer, 5 ... Filling material, 6 ... Acoustic lens.

 ─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-56-160196 (JP, A) JP-A-57-87298 (JP, A) JP-A-58-206732 (JP, A) JP-A-59- 171296 (JP, A) JP-A-55-151894 (JP, A) JP-A-59-226600 (JP, A)

Claims (4)

[Claims] 1. A piezoelectric vibrator for transmitting and receiving ultrasonic waves, a back load material provided on one side of the piezoelectric vibrator, and one or more acoustic matching layers provided on the other side of the piezoelectric vibrator. At least the piezoelectric vibrator is divided into a plurality of, in the gap between the rubber or synthetic resin as a base material, a metal powder or insulating powder having a large specific gravity with respect to the base material is 100 by weight ratio. ~ 400%, 0.8 to 2 by weight of plastic microballoons with a small specific gravity relative to the base material.
% An ultrasonic probe characterized by being filled with a mixed material. 2. The ultrasonic probe according to claim 1, wherein the rubber material as the base material is any one of silicon rubber, urethane rubber, butyl rubber and neoprene rubber. 3. The ultrasonic probe according to claim 1, wherein the synthetic resin as the base material is either an epoxy resin or a urethane resin. 4. The ultrasonic probe according to claim 1, wherein the powder is any one of tungsten powder, tantalum powder, ferrite powder, zinc, silicon carbide, tungsten carbide or iron powder, or a plurality thereof. Child.