JPS6321500B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention Industrial Application Field The present invention relates to an ultrasonic diagnostic apparatus, particularly an electroacoustic mutual conversion means that transmits ultrasonic waves in a pulsed manner and receives reflected waves thereof, and is capable of detecting a subject. The present invention relates to a linear scanning ultrasonic diagnostic device that scans in a straight line and obtains a display based on reflected waves.

BACKGROUND OF THE INVENTION Conventional linear scanning ultrasonic diagnostic devices include mechanical scanning and electronic scanning, each of which has its own drawbacks.

The mechanical scanning method is a method in which a single or multiple ultrasonic transducers are mechanically scanned, and therefore the stability and reliability of the electrical connection between the mechanically moving transducers and the signal processing circuit is important. lacking in sex. Furthermore, in a device that performs linear scanning by reciprocating a vibrator, it is difficult to obtain a uniform scanning speed at high speeds due to the inertia of the vibrator system. However, in general, mechanical scanning methods have better scanning reproducibility than manual scanning methods, and scanning speeds can range from low to high speeds, so they can be used in a wide range of applications, from static images for precise diagnosis to dynamic images for real-time observation. It can be applied to

Since the electronic scanning method inherently allows high-speed scanning, it is suitable for real-time dynamic observation. However, in order to obtain an effective number of scanning lines, a very large number (eg, 200 to 300) of transducers must be arranged linearly within a given scanning range (eg, 100 mm). Therefore, in order to drive these individual vibrators independently, a correspondingly large number of switching circuits are required. Further, the cross-sectional shape of each transducer in the scanning plane is close to a square in the direction of propagation of the ultrasonic waves. In other words, the thickness and width of the vibrator are close in value. For this reason, the vibration in the width direction affects the thickness vibration corresponding to the direction of propagation of the ultrasonic wave, so when the transducer is driven, the ideal piston movement is not achieved in the direction of propagation of the sound wave, resulting in a complex vibration pattern. This will have a negative impact on the ultrasound field. Furthermore, when the distance between the transducers becomes more than half a wavelength, a so-called grating globe occurs, causing a virtual image in the image.

In this type of device, a so-called quantized electron focus technique is used to improve the spatial resolution in a direction perpendicular to the direction of ultrasound propagation (ie, in the azimuthal direction). However, this requires a complicated circuit for controlling the phase of the transmitted or received signal, and furthermore, sidelobes occur due to the quantized phase.

As described above, the electronic scanning method has a limit in the number of scanning lines due to limitations due to the mechanical arrangement of the transducers, and is therefore not suitable for precise diagnosis that requires high-quality still images.

Purpose of the present invention The present invention solves the drawbacks of the prior art,
Selectively obtains dynamic images suitable for real-time observation and high-quality static images suitable for precise diagnosis without the need for complex circuit configurations and essentially without creating virtual images due to grating globe and sidelobes. The purpose of the present invention is to provide a linear scanning ultrasonic diagnostic device that can perform

This object is achieved by the ultrasonic diagnostic apparatus according to the present invention as follows. That is, in this apparatus, the diagnostic device includes at least one ultrasonic transducer that transmits and receives ultrasonic waves in a predetermined direction over at least the scanning area; The band-shaped circulating body is configured to include a first portion having an acoustic impedance that substantially blocks ultrasonic waves, and a driving means for causing the band-shaped circulating body to continuously travel. a second portion forming at least one acoustic aperture that has an acoustic impedance that substantially transmits sound waves and forms an ultrasound beam by the transmitted ultrasound waves; The ultrasonic beam linearly scans the linear scanning area as the means continuously circulates.

According to one aspect of the invention, the second part of the circulatory band forms an acoustic lens that focuses the ultrasound beam to a predetermined point.

According to another aspect of the present invention, the drive means in the present apparatus includes a scanning speed setting means for setting the running speed of the band-shaped circulating body to a desired speed. According to yet another aspect of the invention, the first portion of the band-shaped circulating body has an acoustic absorption layer that absorbs ultrasonic waves.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of an ultrasonic diagnostic apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. In the figure, the present device includes a probe 100 and a signal processing circuit 200. The probe 100 has a driving pulley 106 and a driven pulley 108 in a housing 104 filled with a liquid 102, and a loop-shaped belt 110 that extends around these pulleys. Drive pulley 10
The drive shaft 112 of No. 6 is connected to an external drive source such as a motor 300, thereby rotating in the direction of arrow 114. When the belt 110 is driven by this, a guide roller 116 is provided as shown in the figure in order to eliminate instability in belt running due to centrifugal force or the like.

Inside the belt 110, a linear ultrasonic transducer 118 is disposed as shown in the figure so as to extend over a linear effective scanning area L. The transducer 118 is made of, for example, a ceramic piezoelectric element. , with electrodes 120 and 122 mounted on its upper and lower surfaces and connected to terminals 128 and 13 by electrical connection leads 124 and 126, respectively.
Connected to 0. The vibrator 118 is the electrode 120
It is an electro-acoustic interconversion element that generates ultrasonic waves by piezoelectric effect in response to electric signals applied to electrodes 120 and 122, and converts the received ultrasonic waves into electric signals through electrodes 120 and 122. liquid 1
02 is a substance with low absorption, such as silicone oil, which is relatively close to the acoustic impedance of the human skin, and a matching layer 13 is provided on the lower surface of the electrode 122 to match the acoustic impedance of the liquid 102.
2 is installed. Also, the electrode 1 of the vibrator 118
A backing material 134 is attached to the upper side of the vibrator 118 to attenuate the vibration of the vibrator 118 for a predetermined time or reflect it downward.
When 8 is pulse-excited, secondary reflections are substantially eliminated, so it is possible to obtain ultrasonic pulses with a short transmission time. Note that in this embodiment, the vibrator 118,
Although one set of the matching layer 132 and the bucking material 134 is arranged, a plurality of sets of these may be arranged linearly across the effective scanning area L.

The belt 110 includes a first portion 110A made of a material whose acoustic impedance is significantly different from that of the liquid 102, such as a metal or a foamed material containing a large amount of air (such as polyurethane);
and a second part, namely an acoustic aperture 11, made of a material, such as silicone rubber, having an acoustic impedance approximately equal to that of the liquid 102.
Consists of 0B.

Therefore, although the ultrasonic waves generated by the transducer 118 travel downward in the figure, the ultrasonic waves generated by the transducer 118
At 0A, virtually all of the light is reflected and the aperture 1
At 10B, virtually everything is transmitted.
Ultrasonic beam transmission film 104B corresponding to the effective scanning area in the housing 104 of the probe 100
is made of a material such as silicone rubber, which has an acoustic impedance that is substantially equal to or close to the geometric mean of the acoustic impedances of the liquid 102 and the object 138;
Most of the ultrasound transmitted through 0B is transmitted through the transmission membrane 104.
B, and progresses into the interior of the subject 138, such as a human body. Further, the transmission film 104B has approximately the same width as the rectangular vibrator 118. Housing 10
The portion other than the transparent film 104B of No. 4 forms an acoustic insulating layer having an acoustic impedance that substantially blocks ultrasonic waves. The acoustic aperture 110B is circular, for example, and forms an acoustic lens with a certain radius of curvature as shown in the figure, so the ultrasonic beam that passes through it passes through the transparent film 104B to the subject 13.
It is designed to focus on a certain point inside 8, and can improve spatial resolution.

In this embodiment, the openings 110B are arranged at two locations at points that divide the entire length of the belt into two, so when the pulley 106 is driven in the direction of the arrow 114, one of the openings 110B opens the scanning area L from the right. Pass to the left, and after a certain time, open the other opening 110
B passes through the scanning area L in the same manner. In this way, the transducer 118 transmits and receives ultrasonic pulses only while one aperture 110B is within the scanning area L, and the object 138 is thereby linearly scanned.

If the curvature of the pulley 106 is small, the opening 110B
Although this is desirable because the mechanical deformation experienced by the opening 110B is reduced, the time between the time when one opening 110B leaves the scanning area L and the time when the other opening 110B enters the scanning area L becomes longer, and scanning efficiency deteriorates. In such a case, for example, as shown in FIG. 2, a total of four openings 110B are arranged, one at each point where the entire length of the belt is divided into four, and adjacent openings 110B are arranged.
The distance between them is at least equal to or longer than the length L of the scanning area L. By doing so, the scanning area L can be scanned substantially continuously in a straight line. Note that the number of openings 110B in the belt 110 may be any number greater than or equal to one, and is not limited to the number shown in this embodiment.

Returning to FIG. 1 again, the signal processing circuit 200
Reference clock 20 that generates a reference clock for scanning.
2, and a transmitting section 204 that generates a transmitting signal that pulse-excites the vibrator 118 in response to this clock.
, a transmission/reception switching section 206 that switches transmission and reception operations by the transducer 118, and a transducer 118.
The apparatus includes a received signal processing section 208 that processes a received signal received by the subject 138 into a luminance modulated signal, and a display section 210 that visually displays reflected echoes of ultrasound inside the subject 138 using the luminance modulated signal. This visual display section is composed of, for example, a common cathode ray tube, whose vertical deflection signal is generated by a vertical deflection signal generator 212 in response to a reference clock 202, and whose horizontal deflection signal is generated by a horizontal deflection signal generator 212.
Occurs at 14. By the way, a light reflector 140 is attached to the inside of the belt 110 as shown in the figure immediately after the opening 110B with respect to the running direction of the belt, and a horizontal synchronization sensor 142 having a light emitting element and a light receiving element is provided at the position shown in the figure. When the reflector 140 comes directly below the sensor 142, the light emitted by the light emitting element is reflected by the light reflector 140, which is detected by the light receiving element and the signal is sent to the scan start detection section 216 through the terminal 144. It will be done. Horizontal deflection signal generator 2
14, a horizontal deflection operation is started by this scanning start detection section 216. Note that in this embodiment, the storage control unit 2 is provided between the received signal processing unit 208 and the display unit 210.
18 and a storage section 220 are provided, but these are not necessarily necessary as will be explained later. The display unit 210 may also be provided with a recording unit 222 that creates a hard copy of the visible display on the display unit 210, such as a camera. Further, in this embodiment, a speed control section 302 that controls the rotational speed of the motor 300 may be provided. This will be explained later.

Operation of the Invention Next, the operation of the present device will be explained. belt 110
The drive reel 106 is rotated by the motor 300 to run at a predetermined speed. On the other hand, the transmitting section 204 generates a pulse-shaped transmission signal in response to the reference clock 202, and the transmitting/receiving switching section 206 also switches to send the pulses generated by the transmitting section 204 to the vibrator 118 in response to the reference clock 202. It will be done. Therefore, when the vibrator 118 is excited in a pulsed manner, ultrasonic pulses are generated over the entire surface of the vibrator 118, that is, at least over the scanning area L in FIG. 1 and downward in the figure. Ultrasonic waves transmitted toward a portion other than the aperture 110B, that is, the first portion 110A, are reflected by its inner surface, but ultrasonic pulses transmitted toward the aperture 110B are reflected by the aperture 11 forming an acoustic lens.
0B, the ultrasonic wave travels downward in the figure as a beam-like ultrasonic wave, passes through the liquid 102 and the transparent membrane 104B, and travels inside the subject 138, where it is focused at a predetermined point. On the other hand, during the period when the transmitting section 204 is not generating a transmitting pulse, the transmitting/receiving switching section 206
18 to be connected to the reception signal processing unit 208, and when the previously transmitted ultrasound is reflected inside the subject 138, a part of it passes through the opposite path of the transmitted ultrasound to the belt from the acoustic aperture 110B. The signal propagates inside the oscillator 118 and is received by the transducer 118, and the received signal is processed by the received signal processing unit 208. The processing unit 208 modulates the brightness of the visible display on the display unit 210 using this received signal, and displays the subject 138.
Display the echo generated inside the .

By the way, when one opening 110B enters the right end of the scanning area L as the belt 110 runs, the sensor 142 detects this as described above and sends a signal to the scanning start detection section 216, causing the horizontal deflection of the display section 210. is started by the horizontal deflection signal generator 214. Therefore, while the aperture 110B is at a certain position within the scanning area L, the transducer 118 is excited by one transmitted pulse, and then the horizontal deflection occurs while the transducer 118 receives the reflected wave from this transmitted pulse. The signal generation unit 214 generates one horizontal scanning line on the display unit 21.
Form to 0. Next, when the opening 110B comes to the next position as the belt 110 travels, the vertical deflection signal generator 212 performs vertical deflection by one scanning line in response to the reference clock 202, and the next transmission/reception operation is performed at this position. repeat. In this way, the echoes of the reflected waves are sequentially visually displayed on the display section 210. Therefore, it can be seen that the scanning line density in the scanning area L can be changed by changing the rotational speed of the motor 300. A speed control section 302 is provided for this purpose. As a result, when it is desired to observe the dynamics of a living body, for example, by increasing the rotational speed of the motor 300, the scanning line density becomes coarser, but the pattern inside the living body, which changes from moment to moment, can be displayed in real time. Can be done. Furthermore, if it is desired to obtain a high-quality static image for precise observation, the rotation speed of the motor 300 may be slowed down to increase the density of scanning lines in the scanning area L. In this case, in order to prevent the scanning speed of the entire screen from slowing down and making it difficult to observe the entire screen, the storage control section 218 temporarily stores one frame of the image in the storage section 220. The display unit 21 is refreshed at a speed higher than the flicker limit frame speed, for example, at a speed higher than 50 fields/second.
Display it at 0. Therefore, as described above, when performing only real-time high-speed scanning, the circuits of the storage control section 218 and the storage section 220 are not required.

For example, considering real-time observation, the frame rate needs to be 50 fields/second or more, so the time for one field is 20 milliseconds or less. If the length of scanning area L is 100mm, this is 20
To scan in milliseconds, the linear velocity of the belt 110 is
100mm/20ms = 5m/sec. Assuming that the reception depth of one scanning line in the living body is 150mm,
The average speed of sound in a living body is approximately 1500 m/s, so 150
The time required to go back and forth mm is 0.2 milliseconds.
Since the belt moves 1 mm during this 0.2 millisecond period, 100 scanning lines are obtained over a total scanning area of 100 mm. In fact, if you use 2:1 interlaced scanning like in regular television, you can obtain 200 scanning lines at a rate of 25 frames/second (2 fields/frame at 50 fields/second). .

Since the transducer 118 generates ultrasonic waves on its entire surface, the ultrasonic waves reflected from the inner surface of the first portion 110A of the belt 110 may be received by the transducer 118 and produce a virtual image on the display section 210. In order to prevent this, the first portion 110A of the belt 110
An ultrasonic absorbing layer 146 made of rubber or the like is provided on the inside of the first portion 110A, or the cross-sectional shape of the reflective layer on the inside surface of the first portion 110A is made into a chevron shape as shown in FIG. 3, so that the reflected ultrasonic waves are dispersed in all directions. This is desirable.

Effects of the Invention Due to the above-described configuration of the present invention, there is no instability in the mechanical contact portion, unlike in the conventional vibrator movable mechanical scanning system, and there is no variation in scanning speed. Furthermore, compared to the electronic scanning method, it does not require a large number of complex switching circuits, and since the shape of the transducer is long in the direction perpendicular to the direction of propagation of the ultrasonic wave, there is no complicated vibration pattern, making it ideal. A sound field can be obtained. Further, grating lobes and side lobes, which are characteristic of electronic scanning methods, essentially do not occur, and a complicated circuit for phase control is not required. Therefore, a high-quality screen can be obtained with a simple and inexpensive device configuration, and an ultrasonic diagnostic device suitable not only for real-time observation but also for precise diagnosis can be provided.

Although the present invention has been described with respect to the specific embodiments shown, various modifications may be made within the scope of the appended claims without departing from the spirit of the invention.
For example, it is clear that the transducer 118 does not need to be a single transducer across the linear scanning region L, and that a plurality of transducers may be arranged along the scanning direction. Although the belt 110 is configured to surround the vibrator 118 in the scanning plane (the plane in FIG. 1), it is not necessarily limited to this, and the Any configuration may be used as long as the first portion 110A completely traverses and blocks sound waves. For example, a configuration in which a portion of the belt 110 other than the scanning area L runs and circulates in a direction perpendicular to the surface of the figure, or an acoustic aperture 1
It is clear that the concept of the present invention also includes a disk configuration that rotates in a plane perpendicular to the plane of FIG. 1 so that the slit corresponding to 10B travels in a straight line across the linear scanning area L.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a part of the ultrasonic diagnostic apparatus according to the present invention in a sectional view and other parts in a block diagram, and FIG. 2 is a schematic diagram showing another example of the probe used in the ultrasonic diagnostic apparatus according to the present invention. The cross-sectional view shown in FIG. 3 is an enlarged cross-sectional view showing an example of the chevron-shaped cross-sectional shape of the first portion of the belt used in the ultrasonic diagnostic apparatus of the present invention. Explanation of symbols of main parts, 100...probe,
110...Loop-shaped belt, 110A...First part, 110B...Second part, acoustic aperture, 11
8... Ultrasonic transducer, 146... Ultrasonic absorption layer,
200...Signal processing circuit, 300...Motor, 3
02...Speed control unit, L...Scanning area.

Claims (1)

[Scope of Claims] 1. A linear scanning ultrasonic diagnostic device that scans a subject over a predetermined linear scanning area and obtains a display based on reflected waves, wherein the diagnostic device scans a subject over a predetermined linear scanning area and obtains a display based on reflected waves. at least one ultrasonic transducer that transmits and receives ultrasonic waves, a band-shaped circulating body that circulates ultrasonic waves in a predetermined direction across the scanning area, and a drive means that continuously runs the band-shaped circulating body. The band-like circulation body includes a first portion having an acoustic impedance that substantially blocks ultrasonic waves, and a first portion having an acoustic impedance that substantially transmits the ultrasonic waves, and the first portion having an acoustic impedance that substantially transmits the ultrasonic waves. at least one forming a sound wave beam
and a second portion forming two acoustic apertures, and as the driving means continuously circulates the band-shaped circulating body, the linear scanning area is linearly scanned by the ultrasonic beam. Ultrasound diagnostic equipment. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the second portion of the band-shaped circulation body forms an acoustic lens that focuses the ultrasonic beam on one predetermined point. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the driving means includes a scanning speed setting means for setting the running speed of the band-shaped circulating body to a desired speed. 4. The ultrasonic diagnostic apparatus according to claim 1, wherein the first portion of the band-shaped circulating body includes an acoustic absorption layer that absorbs ultrasonic waves.