JP3325305B2 - 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 for an ultrasonic diagnostic apparatus, and more particularly to a transducer in an electronic scanning ultrasonic probe in which a large number of rod-shaped piezoelectric transducers are arranged in an array. The present invention relates to a technique for improving the directivity of ultrasonic waves in a direction orthogonal to the arrangement direction.

[0002]

2. Description of the Related Art As is well known in various documents, an electronic scanning ultrasonic probe has an elongated rod-shaped piezoelectric vibrator arranged in an array on a sound absorbing material (also referred to as a backing material). In general, a plurality of acoustic matching layers are provided on the upper surface of the element, and the acoustic matching layer is covered with an acoustic lens.

[0003] Among the components of the above-mentioned probe, an acoustic lens is provided for the purpose of focusing ultrasonic waves in a direction perpendicular to the arrangement direction of the piezoelectric vibrators (hereinafter, referred to as a short axis direction).
Usually, the ultrasound is focused by the acoustic lens in the short axis direction using the propagation speed of the ultrasound, and the shape of the probe is easily adjusted because the probe is easily brought into close contact with the body surface of the subject. Is formed in a thick kamaboko shape at the center of the cross section. Due to this shape, ultrasonic waves from the end of the elongated rod-shaped piezoelectric vibrator are quickly propagated into the subject, and ultrasonic waves from the central part are slowly propagated into the subject, resulting in ultrasonic waves in the short axis direction. Beam focusing is performed.

[0004]

According to the above prior art, the ultrasonic beam is focused in the short axis direction, but on the other hand, in the short axis direction in the subject due to attenuation due to the thickness of the acoustic lens. The sound pressure distribution becomes concave in contrast to the convex shape of the acoustic lens, and it cannot be said that good results are obtained in terms of beam directivity.

The present invention has been made in view of the above, and has improved the sound pressure distribution in the short axis direction without changing the shape of a conventional convex acoustic lens which is easily adhered to a subject. It is an object of the present invention to provide an ultrasonic probe capable of improving the directivity of a sound beam and obtaining a good ultrasonic image.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a sound absorbing material and a sound absorbing material arranged on an upper surface of the sound absorbing material.
Piezoelectric vibrator group and the piezoelectric vibrator group
An acoustic matching layer, and the acoustic matching layer
Are both ends thin in the direction perpendicular to the direction of arrangement of the piezoelectric elements?
With an acoustic lens with a thick central part
In the vibrator, between the sound absorbing material and the piezoelectric vibrator group
In addition, a thin film material having a thickness of λ / 4 (where λ is the wavelength of the ultrasonic wave) is used.
The first thin film material having a predetermined acoustic impedance
At the center in the orthogonal direction, the same thickness as the first thin film material
The second thin film having a higher acoustic impedance
The film material is disposed so as to sandwich the film material in the orthogonal direction . Further, the first thin film material
And the second thin film material, and the thin film materials
Of the same acoustic impedance as that of the thin film material.
That it has at least one thin film material
It is a feature.

[0007]

When the backing material, the thin film material, and the piezoelectric vibrator are laminated, the effective impedance of the backing material viewed from the piezoelectric vibrator increases from the center to the end in the short-axis direction. Vibration efficiency of piezoelectric vibrator
(It may be said that the transmission efficiency is high) at the center, and decreases toward the end. Therefore, the concave shape at the center of the sound pressure distribution due to the convex shape of the acoustic lens at the center is compensated.

[0008]

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a partly omitted and cross-sectional view for explaining the internal configuration of the electronic scanning ultrasonic probe. FIG.
Where 1 is PZT and the acoustic impedance is 2
A vibrator portion in which a number of piezoelectric vibrators 11 of 0 × 10 ⁶ kg / m ² · sec are arranged in an array, 3 is a backing material, and an ultrasonic wave radiated to the back of the vibrator when the piezoelectric vibrator 11 is excited. intended to absorb and attenuate, as a material such as those acoustic impedance ferrite rubber ^{_{Z B = 7.5 × 10 6 kg}} / m 2 · sec is used, 4 the wavelength of the ultrasonic wave in the acoustic matching layer When λ is used, a plurality of layers having a film thickness of λ / 4 are laminated to facilitate penetration of ultrasonic waves into a living body. Reference numeral 5 denotes the acoustic lens described above. The above configuration is the same as the conventional probe.

Next, the features of the present invention will be described. In FIG. 1, reference numeral 2 denotes a thin film material composed of three kinds of materials, which changes the effective impedance of the backing material viewed from the piezoelectric vibrator according to the position in the short axis direction. The thin film material 2 has a thickness of λ / 4, a polyurethane resin portion 21 located at the center in the short axis direction, an epoxy resin portion 22 located on both sides thereof, and a ferrite rubber portion 2 located at both ends.
3. Their acoustic impedance Z
_21, Z _22, Z ₂₃ is such that _{Z 21 <Z 22 <Z 23} , for example, ^{_{Z 21 = 2.2 × 10 6 kg}} / m 2 · sec, Z 22 = 3.3 ×
10 ⁶ kg / m ² · sec, Z ₂₃ = 7.5 × 10 ⁶ kg / m ² · se
c.

In this case, the effective impedance of the backing material viewed from the piezoelectric vibrator 11 is (Z
₂₁ ) ² / Z _B , (Z ₂₂ ) ² / Z _B , and (Z ₂₃ ) ² / Z _B , where (Z ₂₁ ) ² / Z _B = 0.6 × 10 ⁶ kg / m ² · sec. , (Z
₂₂ ) ² = 1.5 × 10 ⁶ kg / m ² · sec, (Z ₂₃ ) ² = 7.5 ×
It is 10 ⁶ kg / m ² · sec. Thereby, the vibration efficiency of the piezoelectric vibrator in each part is 20 / (20
+0.6) = 0.97 = 97%, 20 / (20 + 1.5) = 0.93 = 93% at the portion adjacent to the center, and 20 / (20 + 7.5) = 0.727 = 72 at both ends. .7%.

Therefore, when a single elongated rod-shaped piezoelectric vibrator is excited, the sound pressure distribution is high at the center,
The sound pressure decreases toward the end. As a result, the sound pressure distribution of the ultrasonic wave that enters the subject from the acoustic lens 5 can be changed from a conventional concave shape to a convex shape. In other words, this is equivalent to the ultrasonic beam in the short-axis direction becoming thinner and sharper, and the directivity being improved.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be modified without departing from the scope of the invention. For example, in the above embodiment, the thin film material for changing the sound pressure distribution is a composite member of three kinds of different acoustic impedance members. However, in order to make the sound pressure distribution smoother, a composite material of four or more members may be used. good.

[0013]

As described above, according to the present invention, by providing a thin film material whose acoustic impedance changes in the short axis direction between the vibrator portion and the backing material, the ultrasonic wave from the probe can be obtained. Can be changed from a conventional concave shape to a convex shape in the short axis direction, thereby improving the directivity of the ultrasonic beam in the short axis direction. Therefore, an ultrasonic image having a small slice thickness of the subject is obtained, and the image quality is improved. Further, as an incidental effect, the side lobe is reduced, and the S / N ratio can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an internal structure of an ultrasonic probe according to an embodiment of the present invention in a partially sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillator part 2 Thin film material 3 Backing material 4 Acoustic matching layer 5 Acoustic lens

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshihiko Kono 2-1 Shinjyuyo, Kashiwa-shi, Chiba Investigator, Hiroshi Kadota, Hitachi Medical Corporation Osaka Plant Kashiwa Branch Plant (56) References JP-A-4-250799 ( JP, A) JP-A-61-210795 (JP, A) JP-A-4-352950 (JP, A) JP-A-3-254739 (JP, A) JP-A-59-138948 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) A61B 8/00-8/15

Claims (2)

(57) [Claims] 1. A sound absorbing material, and arranged on an upper surface of the sound absorbing material.
Piezoelectric vibrator group and the piezoelectric vibrator group
An acoustic matching layer, and the acoustic matching layer
Are both ends thin in the direction perpendicular to the direction of arrangement of the piezoelectric elements?
With an acoustic lens with a thick central part
In the vibrator, between the sound absorbing material and the piezoelectric vibrator group
In addition, a thin film material having a thickness of λ / 4 (where λ is the wavelength of the ultrasonic wave) is used.
The first thin film material having a predetermined acoustic impedance
At the center in the orthogonal direction, the same thickness as the first thin film material
The second thin film having a higher acoustic impedance
An ultrasonic probe, which is arranged so as to sandwich a film material in the orthogonal direction . 2. The first thin film material and the second thin film material
And the same thickness as those thin film materials
The acoustic impedance between these thin film materials is
2. The method according to claim 1, wherein the first and second thin film members are provided.
The described ultrasonic probe.