JPH0226189B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the electrode arrangement of an electronic scanning ultrasound probe, particularly an electronic scanning ultrasound probe used for ultrasound diagnosis.

An ultrasonic pulse beam is emitted into the subject, and reflected echoes reflected from the boundaries of living tissues based on the difference in acoustic impedance are received and displayed on a display such as a cathode ray tube to display the desired tomographic image. 2. Description of the Related Art Ultrasonic diagnostic apparatuses for observing living tissue inside a subject are well known and are widely used because they can perform non-invasive diagnosis.

In order to transmit and receive ultrasonic pulse beams, an ultrasonic probe including an electroacoustic transducer is used.
By supplying an ultrasonic excitation signal of a desired frequency to the electroacoustic transducer, an ultrasonic beam is emitted from the excited element, and reflected echoes are converted into electrical signals by the electroacoustic transducer. A piezoelectric element made of lead zirconium titanate, barium titanate, or the like is suitable as the electroacoustic transducer.

In an ultrasound diagnostic system using a single beam ultrasound probe, the probe must be mechanically moved along the desired scanning direction in order to obtain a desired tomographic image inside the subject; The disadvantages are that the direction cannot be obtained, the scanning time is long, and real-time diagnosis is difficult to perform. For this reason, electronic scanning ultrasound probes have recently come into wide use. An electronic scanning ultrasonic probe arranges multiple vibrating elements in the electronic scanning direction, and achieves high-speed electronic scanning by sequentially switching and exciting one or more arbitrarily selected vibrating elements in synchronization with a trigger signal. It is being Therefore, according to this electronic scanning type ultrasound probe, when the probe is pressed against a subject, it is possible to almost instantaneously observe a tomographic image along the electronic scanning plane in real time.

FIG. 1 shows an example of a conventional electronic scanning type ultrasound probe. The electroacoustic transducer element 10 made of lead zirconium titanate or the like has a rectangular shape with its longitudinal direction in the electron scanning direction (X direction), and a plurality of divided electrodes are arranged along the electron scanning direction on one surface. Scanning electrodes 12-1 to 12-N are attached thereto, and a ground electrode 14 is attached to the other surface. A conventional ultrasonic probe has the above-mentioned configuration, and the electroacoustic transducer element 10, which has an integral structure, is divided into a plurality of vibrating elements along the electronic scanning direction by the scanning electrodes 12-1 to 12-N, and the ground electrode 1
4 and an arbitrarily selected scanning electrode 12 by an ultrasonic excitation signal supplied between the electrode 12 and the scanning electrode 12 selected arbitrarily.
The vibrating element corresponding to is excited, and an ultrasonic pulse beam is emitted from an arbitrary position in the electronic scanning direction.
Further, reflected echoes are received only from the vibrating elements selectively connected to the receiver. Therefore,
By sequentially switching the vibrating elements to the electronic scanning direction each time a trigger pulse that controls the ultrasonic excitation signal is supplied, it is possible to obtain the scanning action of the ultrasonic beam while the probe is fixed, and it is possible to obtain the scanning action of the ultrasonic beam while the probe is fixed. Ultrasonic tomographic images and the like can be displayed instantaneously in real time. Note that a sound wave absorbing material (not shown) is normally attached to the back surface of the vibrating element, and in the embodiment, by attaching the absorbent material to the scanning electrode 12 side, it is possible to prevent ultrasonic vibration from continuing for too long.

According to the conventional device shown in FIG.
Since it is divided into multiple vibrating elements by 2,
The electronic scanning control described above can be performed. That is, according to the electronic scanning ultrasonic probe, a plurality of adjacent vibrating elements can be used as one group for each wave transmission/reception. For example, when four vibrating elements are used as one group, 1 trigger pulse causes vibration element 1
- 4 is synthesized from four transducer elements by using transducer elements 2 to 5 at the time of the second trigger and shifting the transducer elements used one by one in the electronic scanning direction each time a trigger pulse is applied. The ultrasonic pulse beam is then electronically scanned.

Furthermore, according to the electronic scanning ultrasonic probe, the focusing characteristics of the ultrasonic pulse beam can be controlled by controlling the number of vibrating elements used for one wave transmission/reception.

FIG. 2 shows the focusing characteristics of a typical single beam ultrasonic pulse beam, where D is the diameter of the sound wave emission surface and λ is the wavelength of the sound wave propagating through the medium. As is clear from Fig. 2, the ultrasonic pulse beam can propagate up to a distance of D ² /4λ without substantially expanding its beam width, while maintaining the diameter D of the sound wave emission surface. It is understood that beyond a distance of D ² /4λ, the ultrasound beam diverges at an angle θ. This spread angle θ is determined by sin θ=1.22λ/D.

As is clear from Fig. 2, in an ultrasonic diagnostic device, the ultrasonic propagation velocity C in the subject is almost constant, and as a result, various focusing characteristics can be obtained by changing the radiation surface diameter D. can. In other words, in order to increase the resolution at short distances, it is sufficient to reduce the beam width by reducing the radiation surface diameter D, but in this case, the beam spread starts at a relatively short distance, and The divergence angle is large, and the resolution at long distances is significantly reduced. On the other hand, in order to increase the resolution at long distances, it is sufficient to set the radiation surface diameter D to a large value. In this case, the beam width at short distances increases, but the distance at which the beam starts to spread increases, and Since the divergence angle θ is reduced, the resolution at long distances will be significantly improved. In conventional ultrasonic probes, by changing the number of excited vibrating elements using the above-mentioned focusing characteristics,
Transmission and reception are performed optimally for the desired diagnostic distance. That is, in FIG. 1, the length D of the emitting surface in the electron scanning direction (here, since the emitting surface is rectangular,
Strictly speaking, it is different from D of the sound wave radiation surface in Fig. 2), where the pitch between the vibrating elements, that is, the scanning electrodes is d, and the number of elements used for one transmission/reception is n, the gap between each electrode is relative to the pitch d. If D=
nd, and from this, by changing the number n of vibrating elements used for one wave transmission/reception, it is possible to obtain a predetermined focusing characteristic. In conventional improved devices, the number of transducer elements n is set small when diagnosing short distances, and the number n of transducer elements is controlled to gradually increase as the diagnostic distance gets farther. An ultrasonic beam with a narrow beam width can be obtained over a wide range, and image resolution can be significantly improved.

However, in the conventional device, the length of the sound wave emitting surface in the Y direction perpendicular to the electronic scanning direction
There was a drawback that the resolution in the Y direction was reduced.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and its object is to provide an improved electronic scanning ultrasonic probe that can obtain desired ultrasound beam focusing characteristics even in a direction perpendicular to the electronic scanning direction. The purpose is to provide tentacles.

In order to achieve the above object, the present invention includes an electroacoustic transducer and a scanning electrode formed by arranging and pasting a plurality of divided electrodes on one surface of the electroacoustic transducing element, In an electronic scanning ultrasound probe that excites electrodes under electronic control to electronically control the scanning of the ultrasound beam in the arrangement direction of the divided electrodes and control the focusing characteristics, the scanning of the electroacoustic transducer element is performed. A ground electrode is attached on the surface opposite to the electrode attachment surface and has a plurality of divided electrodes arranged in a direction substantially perpendicular to the electronic scanning direction, and the number of connected plurality of divided electrodes of the ground electrode is measured using an ultrasonic beam. and a switching means for increasing or decreasing the distance of the focal point depending on whether the focal point distance is far or near.

Preferred embodiments of the present invention will be described below with reference to the drawings.

3 and 4 show an embodiment of an electronic scanning ultrasonic probe according to the present invention, and the same members as those of the conventional device shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. The probe of FIG. 3 is shown with the conventional device of FIG. 1 turned upside down, and the ground electrode, which is a feature of the present invention, is shown in detail.

As is clear from FIG. 3, the electronic scanning ultrasonic probe according to the present invention has a ground electrode attached to the other surface of the electroacoustic transducer 10 along a direction Y that is substantially perpendicular to the electronic scanning direction X. They are arranged in multiple columns. In other words, the ground electrode is M electrodes 14-1.
~14-M, and in the example, M=4
The case of is shown. If the width of the ground electrodes in FIG. 3 is W, and the gap between the ground electrodes is sufficiently small compared to the width W, then the number of divided electrodes of the ground electrodes 14 adjacent to each other can be set to m.
The width of the composite ground electrode 14 when connected (hereinafter referred to as the number of ground electrodes) is mW, and by arbitrarily changing the number of ground electrodes to be excited, the width of the ground side excitation electrode can be changed arbitrarily. Even in a direction substantially perpendicular to the electronic scanning direction, the length of the radiation surface corresponding to the radiation surface diameter D in FIG. 2 can be arbitrarily selected and adjusted.

Therefore, according to the present invention, by selecting the number of ground electrodes to be excited in the Y direction as well as in the electronic scanning direction according to the diagnostic distance, the focusing characteristics of the ultrasound beam along the Y direction can be arbitrarily adjusted. Can be set. That is, for short diagnostic distances, the number m of excited ground electrodes is reduced to narrow the ground electrode width, and as the diagnostic distance increases, the number m of excited electrodes is increased to widen the ground electrode width. By doing so, it is possible to obtain an optimal beam width from short distances to long distances, and it is possible to improve resolution over a wide range. The aforementioned selection of the number m of excitation ground electrodes is performed by switching the connection of each ground electrode 14 using a switch or the like as a switching means (not shown). That is, the operating width of the ground electrode is changed by selecting and connecting a predetermined number of ground electrodes that are divided into a plurality of pieces.
Connections are switched so that the number of connections is decreased at short distances and increased at long distances. This makes it possible to form an ultrasonic beam with optimal focusing characteristics for each distance.

In the embodiment shown in FIG. 3, the ground electrode 14
is set to four, but the number of divisions can be determined arbitrarily.

Further, although the electroacoustic transducer element 10 in the embodiment has a monolithic structure, it is also possible to divide and arrange the electroacoustic transducer element 10 by cutting or the like so as to face at least one of the scanning electrode 12 or the ground electrode 14.

Furthermore, in the embodiment shown in FIG. 3, the case where the shape of the electroacoustic transducer element is a rectangular flat plate was explained, but as shown in FIG. 4, the shape of the element is made concave or convex, and the curvature is It is also possible to improve the focusing characteristics of the ultrasonic beam by placing it in the direction or the X direction.

As explained above, according to the present invention, arbitrary ultrasound beam focusing characteristics can be obtained not only in the electronic scanning direction but also in a direction almost perpendicular to this direction, and high resolution can be achieved over a wide range of diagnostic distances. It becomes possible to obtain images of

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a conventional electronic scanning type ultrasound probe, Fig. 2 is an explanatory diagram showing the ultrasound beam focusing characteristics of a general ultrasound probe, and Fig. 3 is a diagram according to the present invention. FIG. 4 is a perspective view showing a preferred embodiment of the electronic scanning ultrasound probe; FIG. 4 is a perspective view showing another preferred embodiment of the electronic scanning ultrasound probe according to the invention. 10... Electroacoustic conversion element, 12-1 to 12-
N...Scanning electrode, 14-1 to 14-M...Grounding electrode.

Claims (1)

[Scope of Claims] 1. An electroacoustic transducing element, and a scanning electrode formed by arranging and pasting a plurality of divided electrodes on one surface of the electroacoustic transducing element, the scanning electrode being electronically controlled. In an electronic scanning ultrasound probe that performs electronic scanning control of an excited ultrasound beam in the arrangement direction of the divided electrodes and control of focusing characteristics, A ground electrode is attached to the side surface and has a plurality of divided electrodes arranged in a direction substantially perpendicular to the electronic scanning direction, and the number of connected plurality of divided electrodes of the ground electrode is determined by the distance of the focal point of the ultrasonic beam. We will increase the number in the near future.
An electronic scanning ultrasonic probe characterized by comprising: a switching means for reducing the amount of noise; 2. An electronic scanning ultrasonic probe according to claim 1, wherein the electroacoustic transducer has an integral structure. 3. An electronic scanning ultrasonic probe according to claim 1, wherein the electroacoustic transducer is divided and arranged to face at least one electrode. 4. The electronic scanning ultrasound probe according to claim 1, wherein the electroacoustic transducer has a convex or concave curvature in the scanning direction or in a direction perpendicular to the scanning direction.