JPH06197894A - Doppler diagnostic ultrasonic probe - Google Patents

Abstract

PURPOSE:To eliminate a stand-off member which has been conventionally required for a conventional ultrasonic probe in the case of Doppler measurement. CONSTITUTION:The upper surface of a piezoelectric material 30 is sectioned into an electrode area and a waveguide area, and comb-shaped electrodes 34a, 34b meshed with each other are formed in the electrode area, and an absorbing cover 36 is formed on the upper surface thereof. An elastic surface wave generated at an electrode part 32 is transmitted to a wave guide part 33 abutting against an acoustic transmission medium from which the elastic wave is radiated in one oblique direction.

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 Doppler diagnosis used when measuring a blood flow velocity and the like by an ultrasonic Doppler method.

[0002]

2. Description of the Related Art An ultrasonic wave is transmitted into a living body, a reflected wave subjected to a Doppler shift by a moving reflector (for example, blood flow) in the living body is received, and the movement reflection is performed from the Doppler information included in the received signal. An ultrasonic Doppler diagnostic device that measures body speed and the like is used. Here, transmission and reception of ultrasonic waves are performed by an ultrasonic probe having an ultrasonic transducer.

Generally, a conventional ultrasonic transducer has a structure in which a piezoelectric material is sandwiched between two electrodes, and when a high frequency signal is applied between the two electrodes, the piezoelectric material is periodically distorted, and as a result, Ultrasonic waves, which are elastic waves, are emitted from the surface of the piezoelectric material in the vertical direction.

By the way, in order for an ultrasonic wave to undergo a Doppler shift, in principle, the ultrasonic beam direction should not be orthogonal to the direction of motion of the blood flow, which is a motion reflector, and the crossing angle of a certain degree or more. is necessary.

Therefore, conventionally, when an ultrasonic probe is brought into contact with the body surface to measure the blood flow velocity in a blood vessel flowing under the body surface and parallel to the body surface, the ultrasonic beam is applied to the body surface. Since it is necessary to set the ultrasonic transducer obliquely with respect to the surface, it is necessary to dispose the ultrasonic transducer obliquely with respect to the body surface. Therefore, conventionally, as shown in FIG. 6, it is necessary to interpose a wedge-shaped standoff material 12 having substantially the same acoustic impedance as that of the living body between the ultrasonic transducer 10 and the body surface 100. . As shown in FIG. 7, this is a blood vessel 1 in a living body.
The same applies to the intraoperative ultrasonic probe that directly contacts the blood vessel 02 to measure the velocity of the blood flow 104 and the ultrasonic probe that is placed in the living body after the operation, and the stand-off member 12 was necessary. .

On the other hand, in an ultrasonic probe inserted into a body cavity or a blood vessel, the Doppler shift becomes the largest when an ultrasonic beam is formed parallel to the blood flow. It is desirable to place an ultrasonic transducer.

However, as shown in FIG. 8, in the ultrasonic probe in which the insertion tube 14 has a tubular structure and the guide wire 16 is passed through the internal cavity, an opening is formed in the front surface of the tip. Therefore, an opening must be formed in the center of the ultrasonic transducer 18, which is difficult to process and manufacture.
Further, there is a disadvantage that the effective area of the ultrasonic transducer 18 is reduced and the characteristics are deteriorated.

On the other hand, in order to avoid the formation of the opening of the ultrasonic transducer, when the ultrasonic transducer 20 is obliquely arranged on the side of the insertion tube 14 as shown in FIG. This causes the problem of difficulty in insertion and manufacturing.

[0009]

As described above, in the conventional Doppler measurement, a stand-off material is required in the body surface contact type and blood vessel contact type Doppler diagnostic ultrasonic probes. The ultrasonic probe of the body cavity insertion type has a problem that the structure is difficult to manufacture.

The present invention has been made in view of the above conventional problems, and an object thereof is an ultrasonic probe for Doppler diagnosis capable of performing Doppler measurement without obliquely disposing an element for generating ultrasonic waves. To provide a child.

[0011]

In order to achieve the above object, the present invention provides a surface acoustic wave element (hereinafter SAW (Surf) as an element for transmitting and receiving ultrasonic waves in an ultrasonic probe.
ace Acoustic Wave) element)
Is used.

That is, according to the first aspect of the invention, a surface acoustic wave element having electrodes formed on the upper surface of the piezoelectric element and surface acoustic waves generated on the upper surface of the piezoelectric element is disposed in the ultrasonic probe, The surface acoustic wave element is brought into contact with an acoustic propagation medium.

According to a second aspect of the present invention, there is provided a Doppler diagnostic ultrasonic probe having a surface acoustic wave element, wherein the surface acoustic wave element has an upper surface divided into an electrode region and a waveguide region. A piezoelectric material and an electrode portion formed on the electrode region, the electrode portion includes one comb-shaped electrode, the other comb-shaped electrode that meshes with the comb-shaped electrode, and an absorption cover that covers both electrodes. It is characterized by being constituted by.

[0014]

According to the structure of the first aspect, since the SAW element is in contact with the acoustic propagation medium, when a surface acoustic wave is generated on the upper surface of the SAW element, the leaky surface acoustic wave causes the SAW element.
The light is obliquely radiated into the acoustic propagation medium at an angle according to the ratio of the acoustic velocity in the acoustic propagation medium to the acoustic velocity of the element.
Here, the acoustic propagation medium is a biological tissue or a biological equivalent substance. When the acoustic propagation medium contacted with the SAW element is biological tissue, the leaky surface acoustic waves are directly radiated into the living body, and when the acoustic propagation medium contacted with the SAW element is a biological equivalent substance. , Surface acoustic waves are radiated into the living body through the biological equivalent substance. On the other hand, conversely to the above, the reflected wave subjected to the Doppler shift by the motion reflector in the living body is S
Received by the AW element.

As described above, S is used as an element for Doppler diagnosis.
By using the AW element, it becomes possible to radiate ultrasonic waves (elastic waves) obliquely from the element surface without tilting the element.

According to the structure described in claim 2, surface acoustic waves are generated in the electrode portion. In this case, however, if there is no absorbing cover, surface acoustic waves are generated in two oblique directions, front and rear, from the electrode portion. To do. However, those oblique surface acoustic waves are absorbed by the absorbing cover. Therefore,
If the surface acoustic wave is transmitted from the electrode part to the waveguide area in the horizontal direction and the acoustic propagation medium is in contact with the waveguide area at that time, the surface acoustic wave is emitted in the oblique direction as described above. become. However, in this case, the surface acoustic waves are radiated obliquely only in the propagation direction of the surface acoustic waves. That is, the emission of the surface acoustic waves in the front and rear two oblique directions is avoided, and the surface acoustic waves are obliquely emitted only in the front direction (the direction in which the waveguide region is seen from the electrode portion). In addition, the wave reception is also performed by the waveguide region.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

(A) Description of Principle First, as a premise, the principle of the SAW element will be described. FIG. 3 shows a top view of a general SAW element 20. The SAW element 20 is provided on the upper surface of the piezoelectric material 22,
Comb-shaped one electrode 24a and the other electrode 2 that mesh with each other
4b is formed. Incidentally, conventionally, this S
The AW element is also used as an analog delay line or the like.

In a general use mode of this SAW element, when a high frequency signal is applied between the electrodes, a surface acoustic wave is generated on the upper surface (electrode surface) of the piezoelectric material.

However, as shown in FIG. 4, when the electrode surface is brought into contact with the acoustic propagation medium 106 such as a living body, the piezoelectric material 22
Acoustic medium 10 for sound velocity of SAWA device in
The leaky surface acoustic waves are obliquely radiated into the acoustic propagation medium at an angle according to the ratio of the sound velocities in 6.

That is, as shown in FIG. 5, when the angle at which the surface acoustic wave is radiated with respect to the normal to the electrode surface is θ, θ = Sin ^-1 ((sound velocity V1 of acoustic propagation medium) / (SAW The sound velocity of the element V2)) (1). Therefore, by using this SAW element, it is possible to solve the problem when the ultrasonic transducer is obliquely arranged as in the conventional case.

However, the SAW element 20 shown in FIG.
Since two surface acoustic waves are radiated obliquely in the front-back direction (left-right direction on the paper surface), Doppler shift may occur in both positive and negative directions without doing so, and it may be difficult to perform Doppler measurement. Therefore, it is necessary to generate elastic waves diagonally in only one direction.

(B) Description of Embodiment FIG. 1 shows a preferred embodiment of the ultrasonic probe for Doppler diagnosis according to the present invention. FIG. 1 (A) is a top view,
(B) is a side sectional view.

As shown, the upper surface 3 of the piezoelectric material 30.
One side of 0a is a waveguide region, and the other side is an electrode region. In this embodiment, the waveguide region is exposed to the outside and serves as a waveguide portion 33 that transmits and receives elastic waves. Of course, a layer of a tissue-equivalent substance having the same acoustic impedance as that of the biological tissue may be formed on the waveguiding region and used as the waveguiding section 33.

The electrode portion 32 on the electrode region is composed of an electrode 34 and an absorption cover 36. The electrode 34 is composed of two electrodes 34a and 34b, and these electrodes are formed in a comb shape and face each other and mesh with each other. A high frequency signal is applied between these two electrodes. Although not shown, a signal line is connected to each electrode and electrically connected to an external circuit.

The entire surface of the electrode 34 is the absorption cover 3
Covered with 6. Here, the absorption cover 36 blocks and absorbs the leaking surface acoustic waves directly in the oblique direction from the electrode portion 32 without hindering the generation of the surface acoustic waves. For example, an adhesive tape or a urethane foam material. Is used.

With the above structure, when a surface acoustic wave is generated in the electrode portion 32 by applying a high frequency signal, the surface acoustic wave does not directly leak from the electrode portion 32 in an oblique direction and the surface acoustic wave is generated. The surface acoustic wave is transmitted from the electrode portion 32 to the waveguide portion 33, and the waveguide portion is in contact with the acoustic propagation medium here, so that the surface acoustic wave is radiated in an oblique direction at an angle according to the above-described first equation. In that case, there is no oblique radiation in the direction opposite to the transmission direction, and only radiation in the forward diagonal direction can be realized.

FIG. 2 shows a concept when the SAW element of this embodiment is used as an ultrasonic wave transmitting / receiving element. As shown, the SAW element 3 is arranged parallel to the living body surface 108.
If 1 is abutted, surface acoustic waves (ultrasonic waves) are radiated in an oblique direction, and it is not necessary to tilt the element itself. Therefore, it is not necessary to use a standoff material.

The example shown in FIG. 2 is of a living body surface contact type, but of course, the ultrasonic probe of this embodiment can be applied to a blood vessel contact type or a body cavity insertion type ultrasonic probe. Applicable.
In the ultrasonic probe for Doppler diagnosis of the body cavity insertion type,
The SAW element of this embodiment may be arranged on the side surface of the insertion tube.

[0030]

As described above, according to the present invention,
It is possible to perform Doppler measurement without arranging ultrasonic transducers that generate ultrasonic waves at an angle. Therefore, there is an effect that the stand-off material or the like which has been conventionally required can be eliminated.

[Brief description of drawings]

1A and 1B are a top view and a side cross-sectional view showing a configuration of a main part of an ultrasonic probe for Doppler diagnosis according to the present invention.

FIG. 2 is an explanatory diagram showing the concept of Doppler measurement using the SAW element according to the present invention.

FIG. 3 is a top view of a general SAW element.

FIG. 4 is an explanatory diagram showing a surface acoustic wave in an oblique direction when the surface acoustic wave is generated by contacting the SAW element shown in FIG.

FIG. 5 is an explanatory diagram showing radiation angles of two surface acoustic waves in an oblique direction from the SAW element.

FIG. 6 is an explanatory view showing a conventional body surface contact type ultrasonic probe.

FIG. 7 is an explanatory view showing a conventional blood vessel contact type ultrasonic probe.

FIG. 8 is an explanatory view showing a conventional ultrasonic probe inserted into a body cavity.

FIG. 9 is an explanatory diagram showing a conventional ultrasonic probe inserted into a body cavity.

[Explanation of symbols]

 30 Piezoelectric material 32 Electrode part 33 Waveguide part 34 Electrode

Claims (2)

[Claims] 1. A surface acoustic wave element having electrodes formed on the upper surface of the piezoelectric element and generating surface acoustic waves on the upper surface of the piezoelectric element is disposed in an ultrasonic probe, and the surface acoustic wave element propagates acoustically. An ultrasonic probe for Doppler diagnosis, which is brought into contact with a medium and obliquely emits a surface acoustic wave generated on the upper surface of the piezoelectric element to perform Doppler measurement. 2. A Doppler diagnostic ultrasonic probe having a surface acoustic wave element, wherein the surface acoustic wave element has a piezoelectric material whose upper surface is divided into an electrode region and a waveguide region, and the electrode region. And an electrode cover formed on the electrode part formed above, and the electrode part is composed of one comb-shaped electrode, the other comb-shaped electrode that meshes with the comb-shaped electrode, and an absorbing cover that covers both of the electrodes. An ultrasonic probe for Doppler diagnosis, characterized in that surface acoustic waves are radiated in one oblique direction from the abutting waveguide region.