JPH06181925A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To improve the beam shape by changing the product of the potential applied to a piezoelectric vibrator and the electrode area in the preset direction. CONSTITUTION:A piezoelectric vibrator 1 is divided into five in the short-axis direction and the arrangement direction respectively into a lattice shape. A resistor 11 is stuck on the back face of the piezoelectric vibrator 1. The resistance value of the resistor 11 is changed in steps in the short-axis direction. When voltage is applied across a front electrode 1a and a back electrode 1b, the potential changed in steps in the short-axis direction is applied to the piezoelectric vibrator 1. Only the electrodes 1a of oblique line portions are used in the region having the depth of 50mm or below in a testee, and the electrodes 1a of both the oblique line portions and net line portions are used in the deeper region. The product of the potential and the electrode area is made large at the center in the short-axis direction and made smaller toward the end, and the beam shape in the short-axis direction is sharply improved as compared with the conventional one. The shape of the product is changed on the near side and the far side in the testee in particular, thereby the beam shape is further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe which converts an input electric signal into an ultrasonic wave and transmits the ultrasonic wave and converts the received ultrasonic wave into an electric signal and outputs the electric signal.

[0002]

2. Description of the Related Art An ultrasonic wave is transmitted to a subject, especially a human body, an ultrasonic wave reflected by a tissue in the human body is returned to obtain a reception signal, and an image inside the human body based on the reception signal is obtained. An ultrasonic diagnostic apparatus that facilitates diagnosis of diseases such as internal organs of the human body by displaying has been conventionally used.
In this ultrasonic diagnostic apparatus, an ultrasonic probe is used as a transducer that converts an electric signal into an ultrasonic wave and transmits the ultrasonic wave into the subject and receives an ultrasonic wave reflected in the subject and converts it into an electric signal. ing.

FIG. 5 is a perspective view schematically showing an example of a conventional ultrasonic probe, and FIG. 6 is a block diagram showing a circuit connected to the ultrasonic probe. A large number of piezoelectric vibrators 1 made of, for example, piezoelectric ceramics (PZT) are arranged in a strip shape in the lateral direction (x direction) of FIG. 5, and a common front electrode 1a electrically connected to each other is formed on the front surface side thereof. And is grounded. Further, back electrodes 1b that are independent of each other are formed on the back side of each piezoelectric vibrator 1, and each lead wire 2 is connected to each back electrode 1b. In addition, a matching layer 3 made of epoxy resin or the like corresponding to each piezoelectric vibrator 1 is formed below each piezoelectric vibrator 1 in the drawing. An acoustic lens 4 made of silicone rubber or the like is attached to converge the ultrasonic waves transmitted from the ultrasonic probe in the y direction (short axis direction) perpendicular to the (x direction). Further, above the piezoelectric vibrator 1 in the figure, a backing 5 is provided for the purpose of shortening the ultrasonic wave duration and absorbing the ultrasonic waves transmitted to the back side.
Are coupled to the piezoelectric vibrator 1 with the back electrode 1b interposed therebetween.

In order to transmit an ultrasonic wave into an object (not shown) such as a human body using the ultrasonic probe constructed as described above, each piezoelectric vibrator is transmitted from the transmission circuit 6 shown in FIG. 1, each pulse signal is transmitted to each piezoelectric vibrator 1
The ultrasonic waves are transmitted in a pulse form. Here, the transmission timing of each pulse signal transmitted from the transmission circuit 6 is controlled so that the ultrasonic wave transmitted from each piezoelectric vibrator 1 is focused at a predetermined depth in the subject.

Further, the ultrasonic waves transmitted from this ultrasonic probe and reflected in the subject are received by the respective piezoelectric vibrators 1 and converted into respective received signals. Each received signal is appropriately amplified by each amplifier 7 and then input to the delay adder circuit 8 where the focus is focused on a fixed or sequentially changed depth position in the subject. Delay addition is performed so that they are connected.

The reception signal delayed and added by the delay and addition circuit 8 is input to a signal processing circuit (not shown), and an image signal representing an image inside the subject by ultrasonic waves is generated based on the reception signal. An image is displayed on, for example, a CRT display device based on this image signal. Figure 7
Is a diagram showing a schematic structure of an ultrasonic probe and a sound pressure distribution of ultrasonic waves emitted from the ultrasonic probe. FIG.
FIG. 8 is a diagram showing a beam diameter in a short axis direction of an ultrasonic beam in the case of the radiation sound pressure distribution shown in FIG. 7.

As shown in FIG. 7, this ultrasonic probe is provided with a plurality of piezoelectric vibrators 1 arranged and a plurality of these piezoelectric vibrators 1.
Front electrode 1a and back electrode 1b respectively formed on the front surface for transmitting and receiving the ultrasonic waves and the back surface facing the front surface.
Is equipped with. In addition, the ultrasonic probe is provided with a piezoelectric vibrator 1, a front electrode 1a, a back electrode 1b, lead wires as shown in FIG. 5, an acoustic lens, a backing, and the like. In addition, their illustration is omitted in the drawings described below.

As shown in FIG. 7, when an ultrasonic wave having a uniform radiated sound pressure is transmitted to both the central portion and the end portion of the piezoelectric vibrator, a large side lobe is generated in the ultrasonic beam in the subject, which causes As shown in FIG. 8, the ultrasonic beam can be narrowed down only in the vicinity of the focal point of the acoustic lens (see FIG. 5), and the beam diameter becomes considerably wide as a whole. Therefore, various methods for improving the beam diameter in the minor axis direction have been proposed. Hereinafter, some of these methods will be outlined.

FIG. 9 is a diagram showing a schematic structure of an ultrasonic probe in which the beam diameter in the minor axis direction is improved and the distribution of the potential applied to the piezoelectric vibrator, and FIG. 10 is shown in FIG. It is a figure showing the beam diameter of the short axis direction of the ultrasonic beam in the case of radiation sound pressure distribution. A resistor 11 is attached to the back surface of the piezoelectric vibrator 1 forming the ultrasonic probe, and the back electrode 1b is formed on the back surface side of the resistor 11.

The resistor 11 is made of a material whose resistance value gradually increases from the central portion of each piezoelectric vibrator 1 toward the end portion in the short axis direction. Therefore, the front electrode 1a and the back electrode 1b are formed. When a voltage is applied between the
The electric potential applied to the element changes stepwise as shown in FIG. 9 (b), and therefore the radiated sound pressure also changes. Here, instead of the resistor 11, a dielectric whose impedance changes stepwise may be provided.

When the ultrasonic probe having such a structure is used, the beam diameter in the minor axis direction can be narrowed to some extent as a whole as shown in FIG. FIG. 11 is a diagram showing a second example in which the beam diameter in the minor axis direction is improved. The piezoelectric vibrator 1 constituting this ultrasonic probe is shown in FIG.
As shown in (b), in the minor axis direction, the polarization intensity is large at the central portion of the piezoelectric vibrator 1 and is small toward the ends, thereby obtaining a radiated sound pressure distribution (Japanese Patent Publication No. 1-24479). See the bulletin).

FIG. 12 is a diagram showing a third example in which the beam diameter in the minor axis direction is improved. As shown in FIG. 12 (b), each piezoelectric vibrator 1 constituting this ultrasonic probe is formed in a diamond shape whose area gradually decreases from the center to the end in the short axis direction, Ultrasonic waves that are strong in the central portion and weaker toward the edges are emitted, which improves the beam diameter in the minor axis direction (Japanese Patent Publication No. 1-24480).
(See Japanese Patent Publication).

FIG. 13 is a diagram showing a fourth example for improving the beam shape in the short axis direction. Each piezoelectric vibrator 1 constituting this ultrasonic probe is divided into a plurality in the short axis direction. Thus, similarly to the array direction, the signal timing of the pulse signal applied to the piezoelectric vibrator 1 can be adjusted and the delay addition can be performed in the minor axis direction as well, and the beam shape can be improved in the minor axis direction.

The above is an example of a phased array or linear array type ultrasonic probe in which a plurality of piezoelectric vibrators are arranged. The above method for improving the shape of the beam is basically one piezoelectric element. It can also be applied to an ultrasonic probe of the type that mechanically scans using a vibrator. FIG. 14 is a diagram showing an example of beam shape improvement of the ultrasonic probe of the type that performs mechanical scanning.

This ultrasonic probe is a disk-shaped piezoelectric vibrator 1
And a resistor 11 having a resistance value gradually increasing from the center 0 in the diametrical direction on the back surface thereof.
Is attached. A front electrode 1a and a back electrode 1b are formed sandwiching the piezoelectric vibrator 1 and the resistor 11. In this case, if a predetermined voltage is applied between the front electrode 1a and the back electrode 1b, the piezoelectric vibrator 1 will be shown in FIG.
As shown in, the central part is stronger and a stronger potential is applied to the surroundings.
Radiant sound pressure with a similar distribution is obtained, and the beam shape is improved. When such a circular piezoelectric vibrator 1 is divided into a plurality of pieces, a grid-like division and a concentric division can be considered.

[0016]

By adopting the above-mentioned various ultrasonic probes, the beam shape can be improved in the short axis direction, but the beam shape is sufficiently improved up to the required level. There is a problem that is not done. To further improve this, for example, it is necessary to increase the number of divisions of the piezoelectric vibrator in the minor axis direction shown in FIG. 13, and the number of lead wires 2 (see FIG. 5) increases too much.
There is a problem that the scale of the circuit connected to is too large to be realistic.

In view of the above circumstances, it is an object of the present invention to provide an ultrasonic probe whose beam shape is further improved as compared with the conventional one.

[0018]

A first ultrasonic probe of the present invention which achieves the above object, converts an input electric signal into an ultrasonic wave and transmits the ultrasonic wave, and at the same time, converts the received ultrasonic wave into an electric signal. In the ultrasonic probe that outputs by, the piezoelectric vibrator, which transmits and receives ultrasonic waves from the front side, is divided into a plurality of piezoelectric vibrators,
A resistor or a dielectric attached to a back surface of the piezoelectric vibrator that faces the front surface, the resistance value or impedance of which changes as a function of position in a predetermined direction along the surface of the piezoelectric vibrator; And a piezoelectric vibration element which is formed on the front surface of the piezoelectric vibrator so as to sandwich the resistor or the dielectric material and on the back surface of the resistor or the dielectric material and whose area changes in the predetermined direction as a function of the position. It is characterized in that the product of the electric potential applied to the piezoelectric vibrator and the area of the corresponding portions of the child and the electrode changes in the predetermined direction as a function of position.

Further, the second ultrasonic probe of the present invention which achieves the above object converts the input electric signal into an ultrasonic wave and transmits the ultrasonic wave and converts the received ultrasonic wave into an electric signal and outputs the electric signal. In an ultrasonic probe, a piezoelectric vibrator that transmits and receives ultrasonic waves from the front side, is divided into a plurality, and the polarization intensity changes as a function of the position along the surface, and a piezoelectric vibration that sandwiches the piezoelectric vibrator. Electrodes formed on the front surface and the back surface of the child, the area of which changes as a function of position in the predetermined direction, and the polarization strength of the piezoelectric vibrator and the area of the electrode at the corresponding portions of the piezoelectric vibrator and the electrodes. Is configured so that it changes as a function of position in the predetermined direction.

Here, the piezoelectric vibrator of the first ultrasonic probe or the second ultrasonic probe has a shape in which the piezoelectric vibrator has a gradually smaller area as the piezoelectric vibrator moves away from the center of the piezoelectric vibrator in the predetermined direction. It may be formed in. Alternatively, there is also a mode in which a piezoelectric vibrator formed in a disc shape is used. This piezoelectric vibrator is divided into a plurality of grids, including the case of having a disc shape, or is divided into a plurality of concentric circles in the case of a disc shape.

The product is large at the central portion of the piezoelectric vibrator and changes so as to become smaller as the distance from the central portion in the predetermined direction increases. A plurality of the piezoelectric vibrators may be arranged in a predetermined arrangement direction, and in this case, the product of the arranged piezoelectric vibrators is arranged in the arrangement direction and / or
Or, it changes as a function of position in a direction orthogonal to the arrangement direction.

As a function of this change, for example, a triangle,
Any one selected from a trapezoid, a step, a Gaussian function, a Hamming function, a Hanning function, a Blackman function, and a COS ² function is adopted.

[0023]

In the first ultrasonic probe of the present invention, a resistor or an insulator whose resistance value or impedance changes as a function of position is attached to the back surface of the piezoelectric vibrator, and the electrode also functions as a function of position. A shape with a changing area,
With these, the product of the electric potential applied to the piezoelectric vibrator and the area is also changed as a function of position. Therefore, the effect of improving the beam shape by pasting a resistor or a dielectric whose resistance value or impedance changes as a function of position and the piezoelectric vibrator or electrode having an area that changes as a function of position are provided. The effect of improving the beam shape due to the shape is superimposed, and the beam shape in the minor axis direction is further improved as compared with the conventional case.

Further, in the second ultrasonic probe of the present invention, both the polarization intensity and the area change as a function of the position, and thus the product of the polarization intensity and the area also changes as a function of the position. Since the oscillator is provided, both the improvement of the beam shape by changing the conventional polarization intensity and the improvement of the beam shape by changing the area are achieved as in the case of the first ultrasonic probe. The effect of is superposed, and the beam shape in the minor axis direction is further improved as compared with the conventional case.

[0025]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a schematic diagram (a) showing one piezoelectric vibrator of an embodiment of the first ultrasonic probe of the present invention, and a potential distribution (b) applied to the piezoelectric vibrator. ), An electrode area (c) of the piezoelectric vibrator, and a product (d) of the potential and the electrode area.

The piezoelectric vibrator 1 shown here is, for example, one of a plurality of piezoelectric vibrators 1 arranged in FIG. 5, and is divided into five in a lattice form in the minor axis direction and the arrangement direction. There is. A resistor 11 is attached to the back surface of the piezoelectric vibrator 1. The resistance value of the resistor 11 changes stepwise in the minor axis direction. Therefore, the front electrode 1a and the rear electrode 1b are
When a voltage is applied between the
A potential that changes stepwise in the minor axis direction as shown in (b) is applied.

The front electrode 1a is formed in a shaded portion and a shaded portion in the drawing. The shaded portions are connected to each other, and the shaded portions are connected to each other. Are connected. When obtaining an image of a shallow area inside the subject, only the shaded portion is used, and when obtaining an image of the deep area of the subject, both the shaded portion and the shaded portion are used. .

The area of this electrode is shown in FIG.
It changes like a broken line (hatched portion) and a solid line (hatched and halftone portion) shown in (c). Also,
The product of the electric potential of FIG. 1B and the electrode area of FIG. 1C changes as shown in FIG. FIG. 2 is a diagram showing the beam shape in the short axis direction of the ultrasonic beam emitted from the ultrasonic probe provided with the piezoelectric vibrator shown in FIG.

The region within a depth of 50 mm within the subject is
Only the electrode in the shaded portion in FIG. 1 is used, and in the deeper region, both the shaded portion and the shaded portion in FIG. 1 are used. As described above, in this embodiment, the product of the electric potential and the electrode area is configured such that it is large at the center of the minor axis direction and becomes smaller toward the end as shown in FIG. The beam shape has been greatly improved. In particular, in this embodiment, the shape of the product is changed on the short distance side and the long distance side in the subject, and therefore the beam shape is further improved.

In the embodiment shown in FIG. 1, the resistor 11 is attached to the back surface of the vibrator 1. However, the impedance is changed so that the resistor 11 is replaced by the resistor 11 so as to have the same function. You may stick the changed dielectric. Further, the piezoelectric vibrator 1 in which the polarization strength of the piezoelectric vibrator 1 is changed as shown in FIG. 1B may be provided without attaching the resistor 11 and the dielectric.

FIG. 3 is a diagram showing one piezoelectric vibrator of another embodiment of the present invention. The piezoelectric vibrator 1 has a rhombus that is thick at the center in the short axis direction and becomes thinner toward the ends, and is divided into a plurality of grids. Instead of changing the area of the electrodes as in the embodiment shown in FIG.
The shape of the piezoelectric vibrator itself may be changed as shown in FIG.

FIG. 4 is a diagram showing a change in the short axis direction of the product of the potential applied to the piezoelectric vibrator and the electrode area or the product of the polarization strength of the piezoelectric vibrator and the electrode area. As shown in these figures, this product can take various functional forms that become large at the center in the short axis direction and become smaller toward the ends. Although an example of a disk-shaped piezoelectric vibrator is not shown here, it is similar to the above-described embodiment, and the product of the potential applied to the piezoelectric vibrator and the electrode area or the polarization of the piezoelectric vibrator is used. The same effect can be obtained by changing the product of the strength and the electrode area as the distance from the center of the disk increases. When the disk-shaped piezoelectric vibrator is divided, it may be divided into concentric circles in addition to being divided into a lattice shape.

Further, the focal point of the acoustic lens of the ultrasonic probe constructed according to the present invention is set to ⅔ or more of the maximum diagnostic depth of the ultrasonic diagnostic apparatus equipped with this ultrasonic probe. Is good. The beam shape shown in FIG. 2 is for an ultrasonic probe in which the ultrasonic frequency is 3.5 MHz and the focus of the acoustic lens is approximately 120 mm. The maximum diagnostic depth of the ultrasonic diagnostic apparatus equipped with this 3.5 MHz ultrasonic probe is about 16
Since it is 0 mm, the focus of the acoustic lens is approximately 3/4 of the maximum diagnostic depth. In the case of an ultrasonic probe of another frequency constructed according to the present invention, for example, 2.5
Since the maximum diagnostic depth is about 220 mm in the case of MHz, the acoustic lens focus is about 150 mm or more, the maximum diagnostic depth is about 110 mm in the case of 5 MHz, and the acoustic lens focus is about 150 mm or more and 7.5 MHz. Since the maximum diagnostic depth is about 75 mm, the acoustic lens focus is about 5 mm.
It may be set to 0 mm or more.

[0034]

As described above, in the ultrasonic probe of the present invention, the product of the electric potential applied to the piezoelectric vibrator and the electrode area or the product of the polarization strength of the piezoelectric vibrator and the electrode area is calculated. Since the beam shape is changed in the predetermined direction, the beam shape can be further improved as compared with the conventional case, and a high-resolution ultrasonic image can be obtained.

Further, by combining the resistance value of the resistor, the impedance or polarization intensity of the dielectric and the electrode area, it is possible to construct an ultrasonic probe in which the radiated acoustic intensity is changed in various ways.

[Brief description of drawings]

FIG. 1 is a schematic diagram (a) showing one piezoelectric vibrator of an embodiment of a first ultrasonic probe of the present invention, and a potential distribution (b) applied to the piezoelectric vibrator. ), An electrode area (c) of the piezoelectric vibrator, and a product (d) of the potential and the electrode area.

FIG. 2 is a diagram showing a beam shape in a short axis direction of an ultrasonic beam emitted from an ultrasonic probe including the piezoelectric vibrator shown in FIG.

FIG. 3 is a diagram showing one piezoelectric vibrator according to another embodiment of the present invention.

FIG. 4 is a diagram showing a change in a minor axis direction of a product of a potential applied to a piezoelectric vibrator and an electrode area or a product of a polarization strength of the piezoelectric vibrator and an electrode area.

FIG. 5 is a perspective view schematically showing an example of a conventional ultrasonic probe.

6 is a block diagram showing a circuit connected to the ultrasonic probe shown in FIG.

FIG. 7 is a diagram showing a schematic structure of an ultrasonic probe and a radiation sound pressure distribution of ultrasonic waves radiated from the ultrasonic probe.

8 is a diagram showing the beam diameter in the short axis direction of the ultrasonic beam in the case of the radiated sound pressure distribution shown in FIG.

FIG. 9 is a diagram showing a schematic structure of an ultrasonic probe in which a beam diameter in a minor axis direction is improved, and a distribution of a potential applied to a piezoelectric vibrator.

10 is a diagram showing the beam diameter in the short axis direction of the ultrasonic beam in the case of the radiation sound pressure distribution shown in FIG.

FIG. 11 is a diagram showing a second example in which the beam diameter in the minor axis direction is improved.

FIG. 12 is a diagram showing a third example for improving the beam diameter in the minor axis direction.

FIG. 13 is a diagram showing a fourth example in which the beam diameter in the minor axis direction is improved.

FIG. 14 shows an ultrasonic probe of a mechanical scanning type,
It is a figure showing an example of beam shape improvement.

[Explanation of reference numerals] 1 piezoelectric vibrator 1a front electrode 1b back electrode 2 lead wire 11 resistor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Hara, 1015 Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Kiyoto Matsui, 1015, Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited

Claims (9)

[Claims] 1. An ultrasonic probe that converts an input electric signal into an ultrasonic wave and transmits the ultrasonic wave and converts a received ultrasonic wave into an electric signal and outputs the ultrasonic wave. A plurality of ultrasonic waves are transmitted and received from the front side. And a resistor attached to the back surface of the piezoelectric vibrator, the resistance value or impedance changing in a predetermined direction along the surface of the piezoelectric vibrator as a function of position. Alternatively, a dielectric and the piezoelectric vibrator, and the front surface of the piezoelectric vibrator so as to sandwich the resistor or the dielectric, and the rear surface of the resistor or the dielectric are formed, and the area is located in the predetermined direction. An electrode that changes as a function, and the product of the potential applied to the piezoelectric vibrator and the area of the corresponding portions of the piezoelectric vibrator and the electrode in the predetermined direction Ultrasonic probe characterized by comprising vary as a function of location. 2. An ultrasonic probe which converts an input electric signal into an ultrasonic wave and transmits the ultrasonic wave and converts a received ultrasonic wave into an electric signal and outputs the ultrasonic wave, wherein a plurality of ultrasonic waves are transmitted and received from the front side. A piezoelectric vibrator whose polarization intensity changes as a function of the position along the surface and is formed on the front surface and the back surface of the piezoelectric vibrator so as to sandwich the piezoelectric vibrator, and the area is located in the predetermined direction. An electrode that changes as a function of, and the product of the polarization intensity of the piezoelectric vibrator and the area of the electrode in the corresponding portions of the piezoelectric vibrator and the electrode changes as a function of the position in the predetermined direction. An ultrasonic probe characterized by being formed. 3. The ultrasonic wave according to claim 1, wherein the piezoelectric vibrator is formed in a shape having a gradually smaller area as the piezoelectric vibrator moves away from the central portion of the piezoelectric vibrator in the predetermined direction. Probe. 4. The ultrasonic probe according to claim 1, wherein the piezoelectric vibrator has a disc shape. 5. The ultrasonic probe according to claim 1, wherein the piezoelectric vibrator is divided into a plurality of grids. 6. The ultrasonic probe according to claim 4, wherein the piezoelectric vibrator is divided into a plurality of concentric circles. 7. The product changes in such a manner that the product is large at the central portion of the piezoelectric vibrator and becomes small as the distance from the central portion in the predetermined direction increases.
The ultrasonic probe according to claim 1. 8. A plurality of the piezoelectric vibrators are arranged in a predetermined arrangement direction, and the product of each of the arranged piezoelectric vibrators changes as a function of position in the arrangement direction and / or a direction orthogonal to the arrangement direction. The ultrasonic probe according to claim 1 or 2, wherein 9. The product has a shape selected from one of a triangle, a trapezoid, a step, a Gaussian function, a Hamming function, a Hanning function, a Blackman function, and a COS ² function. 9. The ultrasonic probe according to claim 1, wherein the ultrasonic probe changes.