JP3268907B2 - Ultrasonic probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe used in an ultrasonic diagnostic apparatus and the like, and more particularly to a technique suitable for transmitting and receiving high-frequency ultrasonic waves.

[0002]

2. Description of the Related Art An ultrasonic probe is constructed by accommodating a vibrator portion shown in FIG. 3 in a case and collectively pulling out each of lead wires 5 as a cable. The vibrator part is
A long and narrow rod-shaped piezoelectric vibrator 1a,
One or two acoustic matching layers 2a provided on the ultrasonic transmitting / receiving surface side of the piezoelectric vibrator 1a for acoustic matching with a living body, and provided on the acoustic matching layer 2a to transmit ultrasonic waves. It has an acoustic lens 3a for focusing in a plane (short axis direction) orthogonal to the arrangement direction of the piezoelectric vibrators 1a, and a back sound absorbing material 4a provided on the back of the piezoelectric vibrators 1a. Electrodes (not shown) are formed on both surfaces of the child 1a by baking or the like, and a lead wire 5 is connected to the electrodes.

Here, as the acoustic lens 5a, conventionally, a silicone rubber having substantially the same acoustic impedance as that of a living body and having a sound velocity lower than that of a living body in a cross-sectional shape with a convex central portion, that is, a semi-cylindrical shape, is often used. Have been.
As another method, a material having a higher sound velocity than a living body, an acoustic impedance almost equal to that of a living body, and a small propagation loss, for example, polymethylpentene (Polymethylepentene).
ne) is also known in which the central portion is formed in a concave shape in cross section.

[0004]

In the above acoustic lens, the former is made of silicon rubber, so that the propagation loss is slightly large because the material is silicon rubber. However, since the central part is convex, it is easy to adhere to the body surface of the subject. The latter has a concave shape at the center, making it difficult to adhere to the body surface of the subject, but has both advantages and disadvantages of small propagation loss. In the latter case, it is possible to improve the adhesion between the body surface of the subject and the acoustic lens by using an acoustic coupler formed by sealing degassed water or the like on the front surface of the probe.

On the other hand, in recent years, there has been a demand for an ultrasonic diagnostic apparatus to increase the frequency of an ultrasonic wave to be used to 5 MHz or more. Although an ultrasonic probe of 5 MHz or more is actually on the market, its sensitivity is low, and a good image cannot be obtained when compared with that of 3.5 MHz or less. Is a problem for improving the sensitivity. In terms of ultrasonic wave propagation loss, silicon rubber has a coefficient of 6 to 14 dB / cm · MHz, and is a material that is not suitable for higher frequencies.

[0006] The present invention has been made in view of the above,
It is an object of the present invention to provide an ultrasonic probe which has excellent adhesion to a subject and has low propagation loss of high-frequency ultrasonic waves, that is, a high-sensitivity ultrasonic probe.

[0007]

According to the present invention, there is provided an ultrasonic probe having at least a laminated structure of a back sound absorbing material, a piezoelectric vibrator, and an acoustic matching layer. Is formed in a concave shape, and an ultrasonic wave propagating member made of an ethylene-vinyl acetate copolymer resin and having a convex central portion is provided on the concave-shaped ultrasonic transmitting / receiving surface. Further, the present invention achieves the above object by forming the ultrasonic wave propagating body in an outwardly convex shape.

[0008]

The ultrasonic transmission / reception surface of a laminated body formed by laminating at least a back sound absorbing material, a piezoelectric vibrator, and an acoustic matching layer is formed in a concave shape, and a central portion of an ethylene-vinyl acetate copolymer resin is formed on the concave shape portion. When the ultrasonic propagator having a convex shape is provided, the sound velocity of the ethylene-vinyl acetate copolymer resin is almost the same as that of a living body. The space is equivalent to being filled with living tissue, and the loss of the ethylene-vinyl acetate copolymer resin is small even in high-frequency ultrasonic waves, so that the sensitivity of the probe can be increased.

Further, by making the ultrasonic wave propagating body outwardly convex at the center, the adhesion between the probe and the living body is improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of an ultrasonic transmission / reception unit of an ultrasonic probe according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes an ultrasonic vibrator in which a number of elongated rod-shaped vibrator elements are arranged. In this example, each element is formed to be curved in a direction orthogonal to the arrangement direction. 2 is an acoustic matching layer, which is also a piezoelectric vibrator 1
Is formed along the curved shape of. Reference numeral 4 denotes a back sound absorbing material which absorbs and attenuates ultrasonic waves to the back side of the vibrator.

In this embodiment, the acoustic matching layer 2
The sound propagation body 6 is provided on the upper surface of the. This sound propagating body 6
Has an acoustic impedance of 1.62 × 10 ³ kg / m ^-2 · s
^-1 , the sound speed (sound propagation speed) is 1708 m · s ⁻¹ , which is almost the same as that of a living body, and the center part is formed biconvex using an ethylene-vinyl acetate copolymer resin with small propagation loss. . One surface of the convex shape at the center is the acoustic matching layer 2
Is formed in the same shape as the curved surface of the acoustic matching layer 2.
Is joined to. The ethylene-vinyl acetate copolymer resin refers to a substance represented by the following chemical formula.

[0012]

Embedded image

In this embodiment, as understood from the above description, the acoustic lens provided in the conventional probe is not provided. The function of this acoustic lens is achieved by the curved shape of the piezoelectric vibrator 1. The role of the acoustic propagator 6 formed of the ethylene-vinyl acetate copolymer resin is that the acoustic impedance of the ethylene-vinyl acetate copolymer resin is almost equal to that of the living body, and the sound speed is about the same as that of the living body.
It is said to be 530m · s ^-1 . ), So that the probe can be brought into close contact with the surface of the subject by utilizing this property. In addition, the ethylene-vinyl acetate copolymer resin has a small loss. For example, when comparing the loss with an acoustic lens using a conventional silicone rubber, the average thickness of the silicone rubber acoustic lens is 3 mm, and the ultrasonic frequency used is low. When the frequency is set to 7.5 MHz, the ultrasonic wave passes through a 6 mm thick silicone rubber for transmission and reception, and the frequency is 27 to 63 d.
In contrast to the decrease in the sensitivity of B, in this embodiment, even if the thickness of the ethylene-vinyl acetate copolymer resin is set to 6 mm, the loss is about 12 dB, and a significant improvement in sensitivity can be achieved.

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment in that the piezoelectric vibrator 1A and the acoustic matching layer are linearly formed without being curved in the short axis direction 2A, and the acoustic matching layer 2A and the acoustic propagation body 6A are not curved. In that an acoustic lens 3A is provided between them.
The acoustic lens 3A uses polymethylpentene, which has a higher sound speed than a living body, and is formed in a concave lens shape because the sound speed is higher than that of a living body. A biconvex ultrasonic wave propagator 6A is fixed on the acoustic lens 3A as in the first embodiment. Comparing the loss in the second embodiment with that of the conventional silicone rubber method, the loss in the acoustic lens 3A of polymethylpentene is expected to be about 10 dB. It can be said that the effect of the improvement is more remarkable than the method.

In the first and second embodiments, since the ultrasonic wave propagating member formed of the ethylene-vinyl acetate copolymer resin does not bear the function of converging the ultrasonic wave, the shape is not changed. Can be arbitrarily set. In addition, ethylene-vinyl acetate copolymer resin has the property of hardly permeating ethylene oxide gas used when sterilizing an ultrasonic probe, and sterilization of conventional silicone rubber using an acoustic lens method is not possible. The problem of the oscillator deterioration which is the cause is also improved.

[0016]

As described above, according to the present invention, the ultrasonic wave propagating member made of ethylene-vinyl acetate copolymer resin is provided on the concave ultrasonic transmitting / receiving surface with the central portion being convex. Even if the transmitting and receiving surface of the ultrasonic wave is concave, the adhesion between the body surface of the subject and the probe is good, and the loss to the high-frequency ultrasonic wave is reduced, so that the sensitivity of the probe can be improved and good. A supersonic image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an ultrasonic transmission / reception unit of an ultrasonic probe according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an ultrasonic transmission / reception unit of an ultrasonic probe according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an ultrasonic transmission / reception unit of a conventional ultrasonic probe.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 piezoelectric vibrator 1A piezoelectric vibrator 2 acoustic matching layer 2A acoustic matching layer 3 acoustic lens 3A acoustic lens 4 back sound absorbing material 4a back sound absorbing material 6 ultrasonic wave propagator 6A ultrasonic wave propagator

Continuation of the front page (56) References JP-A-5-316595 (JP, A) JP-A-5-244695 (JP, A) JP-A-6-254100 (JP, A) JP-A-4-53544 (JP) JP-A-63-234949 (JP, A) JP-A-4-23596 (JP, A) JP-A-5-42141 (JP, A) Japanese Utility Model Laid-Open No. 57-23599 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) A61B 8/00-8/15

Claims (2)

(57) [Claims] 1. An ultrasonic probe having at least a laminated structure of a back sound absorbing material, a piezoelectric vibrator, and an acoustic matching layer, wherein the ultrasonic transmitting / receiving surface has a concave shape, and the concave ultrasonic transmitting / receiving surface has the concave shape. An ultrasonic probe characterized by comprising an ultrasonic wave propagating member made of ethylene-vinyl acetate copolymer resin and having a convex central portion formed thereon. 2. The ultrasonic probe according to claim 1, wherein said ultrasonic wave propagating body is formed in a convex shape outward.