JPS6321501B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention Industrial Field of Application The present invention relates to an ultrasonic diagnostic apparatus, in particular, an ultrasonic diagnostic apparatus having an electroacoustic mutual conversion means for transmitting ultrasonic waves in a pulsed manner and receiving the reflected waves. The present invention relates to a sector scanning ultrasonic diagnostic apparatus that scans the area in a fan shape and obtains a display based on the reflected waves.

Prior Art Conventional sector-scanning ultrasonic diagnostic apparatuses include a mechanical scanning method in which sector scanning is performed by mechanically moving an ultrasound transducer, and an electronic scanning method in which sector scanning is performed electronically without moving parts. Mechanical scanning methods in which the vibrator is rotated use slipping contacts for electrical connection of the vibrator, resulting in poor electrical stability, and methods in which the vibrator is moved back and forth have the disadvantage of uneven scanning speed. There is.

Although there are no moving parts in the electronic scanning method, a very large number of transducers are used, and the cross-sectional shape of each transducer in the scanning plane becomes nearly square in the direction of propagation of the ultrasonic waves. In other words, the thickness and width of the vibrator become close in value. For this reason, the vibration in the width direction influences the thickness vibration corresponding to the direction of propagation of the ultrasonic wave, so that the vibration of each vibrator is far from the ideal piston motion. Therefore, side lobes may occur in directions other than the direction in which ultrasonic waves are intended to be transmitted and received.
These transducers control the phase of each transmitted and received signal in order to control the ultrasound beam, but in order to obtain a large sector angle over a wide scanning range, it is necessary to widen the phase delay range with high precision. There must be. Therefore, the configuration of the phase control circuit becomes complicated, and in reality it is difficult to increase the sector angle, which is 80 degrees at most.

OBJECTS OF THE INVENTION The present invention eliminates the drawbacks of the sector scanning ultrasonic diagnostic apparatus of the prior art, enables sector scanning over a wide sector angle without requiring a complicated circuit, and eliminates side lobes. without occurring,
An object of the present invention is to provide an ultrasonic diagnostic apparatus that can perform stable sector scanning.

These objects are achieved by the ultrasonic diagnostic apparatus according to the present invention as described below. That is, in this device, the electroacoustic mutual conversion means has an ultrasonic transducer that uniformly transmits and receives ultrasonic waves over at least the fan-shaped scanning area, and in this device, the side surface of the cylinder completely transmits the ultrasonic waves in the fan-shaped scanning area. It has a cylindrical rotating body that crosses the ultrasonic transducer and surrounds the ultrasonic transducer, and a driving means for rotating the rotating body,
The cylindrical rotating body has a first portion having an acoustic impedance that substantially blocks, reflects or absorbs the ultrasound transmitted from the transducer, and an acoustic impedance that substantially transmits the ultrasound generated by the transducer. and a second part forming an acoustic aperture for forming an ultrasound beam by the transmitted ultrasound, thereby scanning a fan-shaped scanning area as the driving means continuously rotates the cylindrical rotating body. It scans in a fan shape with an ultrasonic beam.

According to one aspect of the invention, the apparatus includes scanning area defining means defining a fan-shaped scanning area and having an acoustic impedance that substantially transmits ultrasound waves only in the fan-shaped scanning area.

According to one aspect of the invention, the second portion forms an acoustic lens that focuses the ultrasound beam on a predetermined point within the object.

According to another aspect of the present invention, the inner surface of the first portion of the cylindrical rotating body has an acoustic absorption layer that absorbs ultrasonic waves.

Structure of the Invention FIG. 1 shows a cross-sectional view of an embodiment of a sector scanning ultrasonic diagnostic apparatus according to the present invention. 2 is a partially cutaway sectional view of the device shown in FIG. 1, viewed from the left side. The probe 100 shown in FIG.
For example, it is filled with a liquid 104 such as a substance that has a relatively similar acoustic impedance to the human skin and has low absorption of ultrasonic waves, such as silicone oil, and a cylindrical rotating body 106 is arranged therein so as to be rotatable by a driving source such as a motor 108. has been done. Therefore, the motor 108 is fixed to the housing 102 by means not shown. The cylindrical rotating body 106 includes a first portion 106A made of a material having a significantly different acoustic impedance from the liquid 104, such as metal or a foam material containing a large amount of air, so as not to transmit ultrasonic waves; A second portion, ie, acoustic aperture 1, made of, for example, silicone rubber, having substantially equal acoustic impedance.
06B. An acoustic absorption layer 110 made of rubber or epoxy resin that absorbs ultrasonic waves is attached to the inner surface of the first portion 106A.

At the center of the rotating body 106, an electroacoustic interconversion element, that is, an ultrasonic vibrating body 112 is fixed relative to the housing 102. As shown in FIG. 3, the vibrating body 112 has a cylindrical shape, for example, and is made of, for example, a ceramic piezoelectric element. Electrodes are attached to both sides of the vibrating body 112, and ultrasonic waves are connected to terminals 118 and 120 by leads 114 and 116, respectively. A matching layer 302 is attached to the lower surface of the vibrator 300 to match the acoustic impedance of the liquid 104; It is composed of a backing material 304 that attenuates or reflects ultrasonic waves.

The probe 100 is for example a subject 1 such as a human body.
The subject 12 is placed on top of the subject 12 as shown in the figure.
The lower surface of the casing 102 in contact with the
As shown in the figure, a slit 124 is provided as scanning area defining means, and this slit is covered with a membrane made of a material that transmits ultrasonic waves, such as silicone rubber. This material is preferably selected to have an acoustic impedance substantially equal to or close to the geometric mean of the acoustic impedance of the liquid 104 and the acoustic impedance of the subject 122. The length of the film 124 in the lateral direction in FIG. 1 determines the sector angle θ at which the object 122 is scanned in sectors, so the sector angle can be freely changed by changing the length.

The acoustic aperture 106B has a curvature such that the ultrasound transmitted by the vibrating body 112 travels through the acoustic aperture 106B, the liquid 104, and the membrane 124 into the subject 122 and is focused at a predetermined point therein. It constitutes an acoustic lens.

By the way, when the cylindrical rotating body 106 is rotated by the motor 108 in the direction of the arrow 126 shown in FIG. The sound waves propagate into the object 122 through the acoustic aperture 106B and the membrane 124, and the reflected waves within the object 122 travel through the opposite path to the vibrating body 112.
received at Therefore, as the acoustic aperture 106B moves within the range of the sector angle θ in the direction of the arrow 126, the object 122 is sector-scanned by ultrasonic waves.

Next, FIG. 4 shows a signal processing circuit for driving and controlling the device shown in FIG. This circuit includes a transmitting unit 400 that generates a pulse that drives the vibrating body 112 to transmit ultrasonic waves, and a transmitting unit 400 that generates a pulse that drives the vibrating body 112 to transmit ultrasonic waves. While the receiving section 402 receives and generates a brightness modulation signal according to the received signal, and the transmitting section 400 generates a transmission pulse, the vibrating body 1
12 is connected to the transmitting section 400, and a transmitting/receiving switching section 404 connects the vibrating body 112 to the receiving section 402 during periods when there is no transmission pulse, and generates a clock for causing the operation of each of these sections in response to a reference clock. and a display section 408 that visually displays echoes on the subject 122 in accordance with the luminance modulation signal generated by the receiving section 402.
The display section 408 is composed of, for example, a conventional cathode ray tube, and its vertical polarization signal is supplied from a vertical deflection section 410 responsive to the clock 406, and its horizontal polarization signal is supplied from a horizontal deflection section 412. The synchronization of horizontal deflection is performed by the scan start pulse generator 414, and the input 4 of the scan start pulse generator 414
16 is connected to a horizontal synchronization sensor 128 through a terminal 127 in FIG.

The horizontal synchronization sensor 128 is composed of a light emitting element and a light receiving element, and a reflector 130 that reflects light is attached to the cylindrical rotating body 106 at a position immediately behind the acoustic aperture 106B in the rotation direction of the cylindrical rotating body 106. When the reflector 130 comes directly below, the light generated by the light emitting element of the sensor is reflected by the reflector 130, the light receiving element detects this light, and the scanning start pulse generator 41
Send a detection signal to 4. The horizontal deflection unit 412 starts horizontal deflection in response to this signal.

Functions and Effects of the Invention Next, the operation of the present device will be explained. Cylindrical rotating body 106 is rotated in the direction of arrow 126 (FIG. 1) by motor 108 as previously described.
One acoustic aperture 106B is located within the sector angle θ.
When entering from the right side in the figure, the reflector 130 is directly below the synchronization sensor 128, so the light receiving element of the sensor 128 receives the light generated by the light emitting element, and thereby the scan start pulse generator 414 starts scanning. The pulses are supplied to the horizontal deflection section 412. Accordingly, the display unit 408 starts one horizontal scanning line. On the other hand, the transmitting section 400 excites the vibrating body 112 in a pulsed manner through the transmitting/receiving switching section 404 in response to the clock 406. As a result, the vibrating body 112
generates ultrasonic waves over a wide range in the downward direction in FIG. It is designed to focus on one point, and can improve spatial resolution. When the pulse excitation of the vibrating body 112 by the transmitting unit 400 is finished, the transmission/reception switching unit 404
is connected to the receiving section 402, and the reflected wave reflected within the subject 122 returns to the vibrating body 112 through a path opposite to that of the transmission. The receiving unit 402 modulates the brightness of the display unit 408 in accordance with the reception signal received by the vibrating body 112 to visually display an echo on the current horizontal scanning line. As the rotating body 106 further rotates in the direction of the arrow 126, the clock 406 also advances, and the vertical deflection section 410 generates a vertical deflection signal to prepare for forming the next horizontal scan line. The transmitting section 400 and the transmitting/receiving switching section 404 are operated by a clock 406.
In response to this, the vibrating body 112 is again excited in a pulsed manner to repeat the transmission operation. In this way, the horizontal deflection unit 412 and the reception unit 402 again perform brightness modulation in accordance with the received echo on the display unit 408 for the next scanning line, thereby visually displaying the echo on the subject 122. Note that the recording unit 418 is a recording device such as a camera that takes a hard copy of the echo displayed on the display unit 408.

In this embodiment, the vibrator 300 has a disk shape with a diameter of 0.5 mm or less, thereby realizing a sector angle θ of approximately 90°. In the conventional electronic sector scanning method, the limit is 80 degrees, so a wider sector angle can be achieved. Further, the vibrating body 112 uniformly generates ultrasonic waves in the direction of the lower half in FIG. 1, and is non-directional over the range of the sector angle θ. The acoustic absorption layer 110 mounted inside the cylindrical rotating body 106 has a first portion 106 thereof.
This is provided to prevent the reflected wave reflected by A from being received by the vibrating body 112 and displaying a virtual image on the display unit 408.

In the embodiment shown in FIG. 1, the sector angle θ is approximately 90°, and the two acoustic apertures 106B are arranged with a phase difference of 180°, so there is a 90° play in the scanning interval of the 90° sector angle. I have time. In order to eliminate this idle time and increase scanning efficiency, the rotating body 106 is
The circumference of No. 6 is divided into four equal parts of 90 degrees each, and one acoustic aperture 106B and one reflector 130 are arranged at each point as shown in the figure. By doing this, it is possible to continuously scan a sector angle θ of 90° without idle time. Note that the number of acoustic apertures arranged on one rotating body is not limited to two or four as in the embodiments of the present invention described here, but it is clear that any number greater than or equal to one may be used. It is.

With this configuration, the ultrasonic diagnostic apparatus according to the present invention does not require a complex array of multiple transducers or a complex phase control circuit, essentially produces fewer side lobes, and can operate at a wide sector angle. A sector scan can be performed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the sector scanning ultrasonic diagnostic device according to the present invention, FIG. 2 is a partially cutaway cross-sectional view of the device shown in FIG. 1 as seen from the left side, and FIG. A perspective view of a vibrating body used in the device shown in
FIG. 4 is a block diagram of a signal processing circuit for driving and signal processing the apparatus of FIG. 1, and FIG. 5 is a cross-sectional view showing another embodiment of the cylindrical rotating body used in the apparatus of the present invention. Explanation of symbols of main parts, 100...probe,
106... Cylindrical rotating body, 106A... First part, 106B... Second part, acoustic aperture, 108
...Motor, 110...Acoustic absorption layer, 112...
Vibrating body, 124... slit-shaped membrane.

Claims (1)

[Scope of Claims] 1. A sector scanning ultrasonic diagnostic apparatus that scans a subject over a predetermined fan-shaped scanning area and obtains a display based on reflected waves, wherein the diagnostic apparatus uniformly scans an object over a predetermined fan-shaped scanning area. an ultrasonic transducer that transmits and receives ultrasonic waves; a cylindrical rotating body whose cylindrical side surface crosses the ultrasonic waves in the fan-shaped scanning area and surrounds the ultrasonic transducer; and the cylindrical rotating body is rotated. a first portion having an acoustic impedance that substantially blocks the ultrasound transmitted from the ultrasound transducer; and a first portion that substantially blocks the ultrasound generated by the ultrasound transducer. a second portion forming an acoustic aperture that has an acoustic impedance that allows the transmitted ultrasonic waves to pass therethrough and forms an ultrasonic beam by the transmitted ultrasonic waves, and the driving means continuously rotates the cylindrical rotating body. An ultrasonic diagnostic apparatus characterized by scanning a fan-shaped scanning area in a fan-shaped manner with an ultrasonic beam as the ultrasound beam moves. 2. The ultrasonic wave according to claim 1, characterized in that it includes a scanning area defining means that defines the fan-shaped scanning area and has an acoustic impedance that substantially transmits the ultrasonic waves only in the fan-shaped scanning area. Diagnostic equipment. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the second portion of the cylindrical rotating body forms an acoustic lens that focuses the ultrasonic beam on a predetermined point within the subject. 4. The ultrasonic diagnostic apparatus according to claim 1, wherein the inner surface of the first portion of the cylindrical rotating body includes an acoustic absorption layer that absorbs ultrasonic waves.