JPS6366218B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic tomographic examination apparatus, and relates to an inexpensive and small fan-shaped electronic scanning type that scans an ultrasonic beam in a fan-shaped manner using simple means to obtain a fan-shaped ultrasonic tomographic image. We aim to provide an ultrasonic tomography system (hereinafter abbreviated as ESU).

One method of constructing an ESU using simple means is disclosed in Japanese Patent Application Laid-Open No. 52-68492, which will be explained with reference to FIG. In FIG. 1, 101 is an object to be examined such as a human body, and 102 is an object to be examined.
A phase array piezoelectric vibrator group (hereinafter abbreviated as PAL) for ESU, 103 is an analog variable delay line device,
It is composed of an acoustic propagation medium 105 and a linear array piezoelectric vibrator group (hereinafter abbreviated as LA) 106 arranged in a concave shape. In the LA 106, a predetermined number of adjacent groups 107 are excited by a selection switch connected to each piezoelectric vibrator, and the LA 106 becomes an ultrasonic beam 108 and propagates through the propagation medium 105.
After passing through PAL104 and PAL102, subject 1
Ultrasonic beam is sent into 01. On the other hand, the reflected beam from the subject 101 is received by the group 107 at the LA 106 via the same route as in the case of transmission, and is then subjected to normal signal processing to be displayed as an image. Deflection of the ultrasonic waves in the subject 101 is performed by selecting an element of the LA 106.

In the conventional configuration described above, the variable delay unit is significantly simplified as shown in FIG. 1, compared to the ESU currently in use. Traditional ESU
Considering that the main reason for the high price and large size of the equipment case was the variable delay section, the above configuration can be used to reduce the cost and size of the ESU.
It can be seen that it has the potential to provide the following.

On the other hand, the above configuration has the drawback that multiple reflections occur between the LA 106 and the PAL 104 within the analog variable delay line device 103, and the multiple reflection signals are superimposed on the true signal, degrading the image. There is. This multiple reflection occurs as follows. When a transmitted ultrasound beam is radiated to the PAL 104 at an angle θ from a group of adjacent transducers 107 in the LA, if that ultrasound beam is expressed as A-0, a portion of the ultrasound beam incident on the PAL is ,
It is reflected by the PAL 104, reaches point B, which is diagonal to point A, centered on point 0, is reflected again at point B, and returns to point A along the opposite path. That is, in the variable delay device in the apparatus shown in FIG. 1, there is a multiple reflection system of A→←O→←B, and the quality of the image is degraded by this multiple reflection signal. The above explanation is about the transmitted signal, but if the received signal is PAL
The same problem occurs when the light is emitted from the LA 104 to the LA 106. In the conventional example, the levels of this multiple reflection signal are -8 dB and -8 dB relative to the true signal when θ = 0° and θ = 20°, respectively.
27dB, which means that only images with an extremely narrow dynamic range can be obtained. The present invention aims to eliminate such multiple reflected signals.

The present invention takes advantage of the advantages of the variable delay device described above, while also preventing the disadvantages seen in the conventional example, that is, multiple reflections within the variable delay device 103.
The present invention provides a fan-shaped electronic scanning ultrasonic tomographic inspection device that is high-performance, compact, and inexpensive.

Figures 2a and 2b show the overall configuration of the tomographic inspection apparatus according to the present invention, where a shows the overall configuration when used for both LA transmission and reception, and b shows the overall configuration when LA is used only for reception. It is something that First, a first embodiment of the overall configuration will be described with reference to FIG. In FIG. 2a, 201 is a subject such as a human body, and 202 is a variable delay device. 203
204 is a selection switch; 205 is a receiver; 206 is an image display device;
207 is PAL.

The drive pulse generated by the transmitter 203 is LA
a selection switch 204 for selecting a predetermined group of transducers;
A variable delay device 20 having a structure to be described later
The voltage is applied to a predetermined group of adjacent piezoelectric vibrators of LA constituting LA. The ultrasonic beam emitted from this piezoelectric vibrator group passes through the propagation path explained based on FIG. 206
The image is displayed and used for diagnosis, etc.

Next, FIG. 2b, which shows the overall configuration when LA is used only for reception, will be described. Figure 2 b a
The difference is that the transmitter is a fan-shaped electronic scanning ultrasonic tomography device transmitter 209 for emitting ultrasound beams from the PAL 207 in a fan shape.
Also, a transmission/reception changeover switch 208 is provided to prevent the transmission signal from being applied to the PAL of the variable delay device 202. The entire operation begins with the transmitter 20
9, the transmission signal corresponding to the predetermined deflection angle is
Apply to PAL207. Note that at this time, the transmission/reception selector switch 208 is in an open state, so that no transmission signal is applied to the variable delay device 202. Note that this transmission/reception selector switch 208 is closed after sending out the transmission signal, and operates to guide the transmission signal to the variable delay device 202. Subject 201
The echo signal obtained from
Selected by the selection switch 204 in accordance with the deflection angle of the ultrasonic beam emitted from the PAL 207.
The signal is received by a predetermined group of adjacent piezoelectric vibrators in the LA, and is input to the receiver 205. This received signal is input to the image display device 206 after being subjected to received signal processing such as detection and amplification, and is used for diagnosis.
Although the overall configuration shown in Figure 2 has a slightly more complicated transmitter than the device shown in Figure 2a, the drive signal with a high signal level is not radiated to the variable delay device, so multiple reflections of the transmitted signal occur. It is possible to prevent
This has the advantage that the system sensitivity is higher than when there is one LA and two PALs, as in the case of . The variable delay device described below is a
The explanation will focus on the case with the overall configuration of b, but it goes without saying that it is basically applicable to the case with the overall configuration of b.

Next, the structure of the variable delay device 202, which is a feature of the present invention, will be explained based on a specific example.
The variable delay device in this embodiment can eliminate or suppress the occurrence of multiple reflections, which is a disadvantage of the conventional example.

FIG. 3 shows the variable delay device in the first embodiment. FIG. 3 shows a cross section parallel to the scanning direction of the ultrasound beam. The feature of the structure shown in Figure 3 is that the LA4 is about half that of the conventional example.
The reason is that only 01 is used. To be more specific, about half of this LA401 is PAL40
2, α is set so that the ultrasonic beam transmitted in the normal direction of PAL402 does not reach LA401.
It is installed at an angle of .
By adopting the structure shown in FIG. 3, for example, the multiple reflection system along the path A→←O→←B described above in FIG. 1 is removed by the sound wave absorber 403, and the multiple reflection signal level is significantly reduced. . According to experiments, θ=
In the case of 20 degrees, the multiple reflection signal level, which was -27 dB in the conventional example, could be lowered to about -60 dB.

Note that the setting of the inclination angle α is determined by taking into consideration the aperture diameter of the PAL 402, the beam width, the distance between the LA 401 and the PAL 402, and the like.

Although various embodiments have been described above, it is clear that the effects can be further improved by using a combination of these embodiments.

As explained above, according to the present invention, the basic advantages of the fan-shaped electronic scanning ultrasonic tomography apparatus are:
In other words, in addition to being able to transmit and receive ultrasonic beams in a fan shape with a simple method, it also eliminates the fatal disadvantage of conventional devices, which is the deterioration of tomographic images due to multiple reflections.
The improvement can be achieved by more than 30 dB, and a high-quality, compact, and inexpensive fan-shaped electronic scanning type ultrasonic tomographic inspection device can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a conventional variable delay device, FIG. 1 is a cross-sectional view showing an example of the configuration of a variable delay device used in the invention. 102, 104, 207, 402... Phase array piezoelectric vibrator group, 101, 102... Subject, 10
6,107,401... Linear array piezoelectric vibrator group,
103, 202...Variable delay device, 108...Ultrasonic beam, 105...Sound wave propagation medium, 403...
...Sound wave absorber, 204...Selection switch, 20
5, 203...transmitter/receiver, 206...display device.

Claims (1)

[Scope of Claims] 1. A first piezoelectric vibrator group arranged in an arc shape, a second piezoelectric vibrator group arranged in a straight line, and between the two piezoelectric vibrator groups. a variable delay device having a sound wave transmission medium interposed therein;
In the scanning plane of the ultrasound beam in the variable delay device, the first piezoelectric transducer group is located outside the area defined by the width of the ultrasound beam transmitted in the normal direction of the second piezoelectric transducer group. An ultrasonic tomographic examination apparatus characterized in that: 2. Claims characterized in that a transmitting/receiving switch and a transmitter for a fan-shaped electronic scanning ultrasonic tomographic examination device are provided between the variable delay device and the phased array piezoelectric vibrator group used in contact with the subject. 2. The ultrasonic tomographic examination apparatus according to item 1.