JP3305117B2 - 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, and more particularly to a Doppler type ultrasonic probe in which the insulation resistance to the outside is increased and the ratio of noise to signal (S / N ratio) is increased. A probe (referred to as a Doppler probe).

[0002]

2. Description of the Related Art A Doppler probe is used as a probe for measuring the velocity of a fluid, for example, in medical applications, for measuring blood flow. In such a device, the influence of external noise and the like is great, and an improvement in the S / N ratio at the time of reception is required.

[0003]

2. Description of the Related Art FIG. 4 is a diagram of a Doppler probe for explaining a conventional example of this type, wherein FIG. 4A is a sectional view and FIG.
Is a rear view of the piezoelectric element. The Doppler probe is formed by arranging semi-circular transmitting and receiving piezoelectric elements 1 (ab) in a disk shape. Specifically, for example, the outer periphery of a disk-shaped piezoelectric plate is fixed to the distal end side (opening end) of the cylindrical resin container 2 with an insulating adhesive. The open end of the resin container 2 has an L-shaped step (holding portion). Although the piezoelectric plate is a flat plate for convenience, it is actually a slightly concave surface. Then, the center of the plate surface is cut to be divided into the respective piezoelectric elements 1 (ab).
Each piezoelectric element 1 (ab) has, for example, an excitation electrode “reference electrode” 3 (ab) for reference potential on the front surface, and a folded electrode 4 (ab) and an excitation electrode for signal “signal electrode” on the rear surface. 5 "(ab). In addition, a metal shielding plate 7 having rubber-based elastic bodies 6 on both surfaces is provided in the dividing groove of the piezoelectric plate. Then, on the rear surface of each piezoelectric element 1 (ab), two lead wires 8 (ab), 9 for the reference potential and for the signal are provided.
(Ab) and connected to the outside from the rear end face of the resin container 2 together with the metal shielding plate 7. Then, the resin container 2 is housed in the shield case 10, and the acoustic matching layer 11 is formed on the front surface of the piezoelectric element 1 (ab).

In such a device, a transmitting piezoelectric element 1 is used.
A burst signal is applied to a, and an ultrasonic wave having a frequency f ₀ is transmitted to a blood flow in a blood vessel (not shown), and the reflected wave is received by the receiving piezoelectric element 1b. Then, the frequency change Δf of the reflected wave f ₀ ′ due to the Doppler effect is detected, and the speed of the blood flow is measured. At that time, in the above configuration, the piezoelectric plate element 1 (ab) is
And a piezoelectric element 1 (ab) for transmission and reception
Since the metal shielding plate 7 is provided therebetween, noise signals at the time of reception are reduced both externally and internally (between transmission and reception). The rubber-based elastic body 6 prevents acoustic coupling between the transmitting and receiving piezoelectric elements 1 (ab).

[0005]

However, in the Doppler probe having the above structure, each of the piezoelectric elements 1 (ab) has a folded electrode 4 (ab). Therefore, no excitation occurs in this portion, and the aperture area for transmission and reception is reduced, and the sensitivity is reduced. The smaller the contact area of the wave transmitting / receiving surface with the living body, the better, and there is a restriction (within about 0.8 mm) in increasing the plate surface area. From this, the folded electrode 4
As shown in FIG. 5, there is also a method in which the lead wire 8 (ab) is directly connected to the reference electrode 3 (ab) on the front face without providing (ab), and the lead wire 8 (ab) is derived.

However, in this case, the lead 8 (a
At the diameter of b) (about 0.25 mm), the surface limit is reached, as compared with the thickness of the acoustic matching layer 11 (0.35 mm, provided that there are two layers at 5 MHz). Therefore, while the insulation resistance value with the human body increases year by year, the resistance value decreases. Also, lead wires 8 may be worn due to wear during use.
(Ab) may be exposed and pose a danger to the human body.

Also, a transmitting / receiving piezoelectric plate element 1 (ab)
Is fixed to the open end of the resin container 2. Therefore, although it is accommodated in the shield case 10, as shown in FIG. 6, external noise N from surrounding electronic devices and the like reaches the signal electrode 5 (ab) from its surface. In particular, in the Doppler type, since the burst signal applied to the transmitting piezoelectric element 1a is about 30 V, the receiving voltage at the receiving piezoelectric element 1b is considerably small. Even low-level noise has a very large effect on the received signal. From this,
In particular, there is a problem that the S / N ratio at the time of reception is deteriorated.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic probe which increases insulation resistance to the outside and improves the S / N ratio at the time of reception.

[0009]

A basic solution is that a conductive layer is provided on an open end surface of a resin container to which a piezoelectric element is fixed, and the conductive layer and an excitation electrode on the front surface of the piezoelectric element are connected by a conductive foil. I do. Hereinafter, an embodiment of the present invention will be described as an operation.

[0010]

1 and 2 are views of a Doppler probe for explaining an embodiment of the present invention. FIG. 1 is a sectional view and FIG. 2 is a view of a resin case. The same parts as those in the prior art are denoted by the same reference numerals, and description thereof will be omitted. The Doppler probe is, as described above, a piezoelectric element 1 for transmission and reception.
(Ab), the metal shielding plate 7 is fitted between them, and is fixed to the holding portion at the open end of the resin container 12 with the adhesive 13. In this embodiment, the resin container 12 has a conductive layer 14 (ab) formed by metallization on the opening end face, and extends as a connection electrode 15 (ab) in a groove provided on the outer surface.
The reference electrode 3 (ab) and the signal electrode 5 (ab) of the piezoelectric element 1 (ab) are all formed with electrodes on the entire surface. Then, the conductive layer 14 (ab) and the reference electrode 3 (ab)
Are bonded by using, for example, solder by a silver foil 16. Also,
A lead wire 8 (ab) is connected to the connection electrode, and is led out through the lower side hole 16 of the resin container 12. And
An insulating tube 17 is placed over the outer periphery of the resin container 12 and housed in the shield case 10.

With such a configuration, the reference electrode 3 (a
b) and the piezoelectric element 1 (ab) for both the signal electrode 5 (ab)
Is provided on the entire surface, so basically all of the plate surface can be excited,
The sensitivity is improved as compared with the case where the folded electrode is provided. In this embodiment, the conductive layer 14 (ab) is provided on the open end surface of the resin container 12 and the silver foil 1 is connected to the reference electrode 3 (ab).
6, the thickness can be reduced. Specifically, for a conventional lead wire having a diameter of 0.25 mm,
Its thickness becomes 0.15 mm or less. Therefore, the acoustic matching layer can be reliably embedded in the matching layer 11, and the insulation resistance with the outside can be increased.

Further, as shown in FIG.
The second conductive layer 14 (ab) enlarges the front electrode to prevent intrusion of external noise and also prevents the signal electrode 5 (ab) from reaching the signal electrode 5 (ab) even after passing through the insulating cylinder 17. In this figure, the thickness of the adhesive is neglected. Therefore, the S / N ratio is improved.

[0013]

[Other Matters] In the above embodiment, a Doppler type probe has been described. However, basically, a split type in which transmission and reception are operated independently of each other is not a split type but a simple single plate. Can be applied. Then, the piezoelectric element 1 (a
Although b) is semicircular, it may be rectangular, and its shape can be set arbitrarily. Further, the conductive layer 14 (ab) and the reference electrode 3 (ab) are joined by soldering silver foil, but may be made of another conductive foil or may be joined by thermocompression bonding or the like. Further, the entire boundary surface between the conductive layer 14 (ab) and the reference electrode 3 (ab) may be joined by a conductive foil to shield external noise that enters the adhesive 13 part.

[0014]

According to the present invention, an ultrasonic probe is provided, in which a conductive layer is provided on the open end face of a resin container to which a piezoelectric element is fixed, and this conductive layer and an excitation electrode on the front surface of the piezoelectric element are connected by a conductive foil. Can be increased in insulation resistance to the outside and the S / N ratio at the time of reception can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a Doppler probe explaining an embodiment of the present invention.

FIG. 2 is a view of a resin container in one embodiment of the present invention.

FIG. 3 is a partially enlarged cross-sectional view illustrating the operation of one embodiment of the present invention.

FIG. 4 is a diagram of a Doppler probe for explaining a conventional example, wherein FIG. 4 (a) is a sectional view and FIG. 4 (b) is a rear view of a piezoelectric element.

FIG. 5 is a partial cross-sectional view illustrating another conventional example.

FIG. 6 is a partial sectional view for explaining a problem of the conventional example.

[Explanation of symbols]

1 piezoelectric element, 2,12 resin container, 3 reference electrode, 4
Folded electrode, 5 signal electrode, 6 rubber elastic body, 7 metal shielding plate, 8, 9 lead wire, 10 shield case, 1
1 acoustic matching layer, 13 adhesive, 14 conductive layer, 15
Connection electrode, 16 silver foil, 17 insulating tube.

Claims (1)

(57) [Claims] 1. A provided a piezoelectric element having a whole surface excitation electrodes on both main surfaces to the open end of the cylindrical container made of resin, the tubular container
Is housed in a shield case where the open end faces are the same,
In the ultrasonic probe having an acoustic matching layer on the front surface, a conductive layer provided on the entire periphery of the opening end surface of the cylindrical vessel, and excitation electrodes for reference potential to be a front surface of the said conductive layer piezoelectric element
Connected by conductive foil on all of the boundary
An ultrasonic probe, wherein an electrode foil is embedded in the acoustic matching layer .