JPH0160254B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a mechanical fan-shaped scanning type ultrasound probe used in connection with a medical ultrasound diagnostic apparatus. Conventional configuration and its problems In order to emit an ultrasound beam toward a living body and mechanically scan the ultrasound beam in a fan shape for the purpose of ultrasonic tomographic diagnosis of a living body, a piezoelectric vibrator must be mounted on a suitable support. The support is vibrated reciprocally with a certain point at the midpoint. Alternatively, a method is known in which a piezoelectric vibrator is provided on a suitable rotary support and the ultrasonic beam is mechanically scanned in a fan shape by rotating the rotary support, that is, the piezoelectric vibrator. The ultrasonic probes shown in FIGS. 1A to 1C are known as ultrasonic probes that mechanically scan an ultrasonic beam in a fan shape by rotating a piezoelectric vibrator. Here, FIG. 1A is a schematic configuration diagram showing an example of a conventional mechanical fan-shaped scanning ultrasonic probe, FIG. 1B is a schematic side view of the rotary support of the same probe, and FIG. This is a circuit diagram showing the general operating principle of the probe, and the portion surrounded by dotted lines indicates rotation. In FIGS. 1A, B, and C, 1 is a rotating support;
2a, 2b, 2c are piezoelectric vibrators, 3a, 3b, 3
c is a reed switch, 4 is a bearing, 5 is a container filled with ultrasonic propagation medium liquid, 6 is a rotary transformer,
6a is the primary coil of the rotary transformer, 6b
is the same secondary coil, 7 is a fixed permanent magnet, 8 is a belt, 9 is a motor, 10 is a rotation control detector, 11
12 shows a probe case, and 12 shows a connection cable with the main device. In the conventional probe shown in FIGS. 1A, B, and C, a rotating support 1 has three piezoelectric vibrators 2a, 2b, 2c arranged at equal intervals on its outer surface, and three piezoelectric vibrators 2a, 2b. , 2c, and a secondary coil 6b which is provided on the rotating shaft of the rotating support 1 and forms a rotary transformer 6. The rotating support 1 is rotated by a motor 9 and a belt 8 as appropriate. On the other hand, the rotation of the motor 9 is controlled to be maintained at a constant rotation speed based on a rotation control detector 10. A rotary transformer 6 installed on the rotation shaft of the rotary support 1 is composed of a primary coil 6a and a secondary coil 6b, and is connected to piezoelectric vibrators 2a, 2b, 2 rotating together with the rotary support 1.
This is for connecting electrical signals with c in a non-contact manner. The operation of transmitting and receiving the ultrasonic pulse beam by this probe is performed by, for example, connecting the fixed permanent magnet 7 and the rotating support 1.
As the reed switch 3a rotates, the reed switch 3a is closed depending on the relative position of the reed switch 3a, and the piezoelectric vibrator 2a is selected. Needless to say, at this time, the piezoelectric vibrator 2a needs to face the living body at a desired position. Next, an electric pulse signal that energizes the piezoelectric vibrator 2a is applied to the primary coil 6a of the rotary transformer 6 through the connection cable 12 to the main device. The signal is immediately induced into the secondary coil 6b by electromagnetic induction,
The piezoelectric vibrator 2a is energized. and piezoelectric vibrator 2
An ultrasonic pulse beam is generated from a, which is emitted towards the living body through a container 5 filled with an ultrasonic propagation medium liquid. On the other hand, the reflected waves caused by the difference in acoustic impedance of the living body pass through the opposite path to the piezoelectric vibrator 2.
received at a. The signal is immediately transmitted to the primary coil 6a of the rotary transformer 6 by electromagnetic induction.
The signal is transmitted to the main unit via the connection cable 12, undergoes appropriate signal processing, and displays its strength as one scanning line on a cathode ray tube. As described above, the piezoelectric vibrator 2a is continuously rotated together with the rotary support 1, and the ultrasonic pulse beam is scanned one after another in a fan shape, thereby obtaining a fan-shaped ultrasound tomographic image of a living body. Here, reed switch 3a
must be kept closed until the piezoelectric vibrator 2a completes the fan-shaped scanning at the desired angle. it is,
This is done by forming the fixed permanent magnet 7 into a half-moon shape, for example, or by arranging a plurality of small magnets to form an appropriate shape, and forming a predetermined magnetic field. Based on the same principle, the piezoelectric vibrator 2b performs fan-shaped scanning by closing the reed switch 3b, and the piezoelectric vibrator 2c performs fan-shaped scanning by closing the reed switch 3c. As a result, each time the rotary support 1 rotates once, the three piezoelectric vibrators 2a, 2b, 2c are sequentially activated by the reed switch 3.
By opening and closing a, 3b, and 3c, they are selectively used to perform fan-shaped scanning at a desired angle (usually 90 degrees), thereby obtaining a fan-shaped ultrasonic tomographic image. By the way, the inductance of the primary coil 6a and the secondary coil 6b of the rotary transformer 6 used in this probe are made to be exactly the same. On the other hand, the piezoelectric vibrators 2a, 2b, and 2c are connected to the secondary coil 6b, and their electrical impedance acts as a load, and the voltage actually applied to the piezoelectric vibrator is the voltage applied to the primary coil. The voltage is considerably lower than the voltage applied to 6a. This voltage drop is
This can be improved by making the inductance of the secondary coil larger than that of the primary coil. However, during reception, the inductance relationship of the coils is reversed, and the received voltage taken out from the primary coil 6a decreases. In the end, in a conventional probe using a rotary transformer in which the primary coil 6a and the secondary coil 6b have the same inductance, or a rotary transformer 6 in which the secondary coil 6b has a large inductance, the rotary The voltage drop caused by the transformer 6, that is, the loss is large. That is, this conventional probe has a very serious drawback in that the rotary transformer 6 significantly reduces the sensitivity, S/N, and other characteristics of the probes 2a, 2b, 2c. Purpose of the Invention The present invention has been made in view of the above-mentioned drawbacks of the conventional ultrasonic probe. It is an object of the present invention to provide an ultrasonic probe that can have good characteristics such as: Structure of the Invention In order to achieve the above object, the present invention makes use of the boost effect caused by electromagnetic induction by making the inductance of at least one of the primary coil or the secondary coil of a rotary transformer different between transmission and reception. It is something. DESCRIPTION OF EMBODIMENTS FIG. 2 shows an embodiment of the ultrasonic probe of the present invention, and is a circuit diagram showing the general operating principle of the probe incorporating a rotary transformer. to show that In Fig. 2, 13a, 13b, 13c are piezoelectric vibrators, 14a, 14b, 14c are reed switches, 15a is a rotary transformer primary coil, and 15-1, 15-2, 15-3 are primary coils 15a. Each terminal, 15b is a secondary coil, 16
is a fixed permanent magnet, L ₁ is terminal 15-1, 15-2
, L ₃ is the inductance between the terminals 15-1 and 15-3, and L ₂ is the inductance of the secondary coil 15b. In the operation of the present invention shown in FIG. 2, for example, similar to the conventional example described above, when energizing the piezoelectric vibrator 13a, the reed switch 14a is closed by the fixed permanent magnet 16, and the energizing electric pulse signal is Terminals 15-1, 15-2 of the primary coil 15a of the transformer
applied in between. The signal is immediately induced in the secondary coil 15b by electromagnetic induction, energizing the piezoelectric vibrator 13a, and an ultrasonic pulse beam is generated and radiated to the living body. On the other hand, the reflected wave generated due to the difference in acoustic impedance of the living body is received by the piezoelectric vibrator 13a, and the signal is transmitted to the secondary coil 15b, and further by electromagnetic induction, induced in the primary coil 15a. The signal is transmitted to terminals 15-1 and 15- of the primary coil 15a.
The signal is guided to the receiving circuit system connected between
displayed on a cathode ray tube. Thereafter, fan-shaped scanning is performed in the same manner as in the conventional example, and a fan-shaped ultrasonic tomographic image is obtained. By the way, in FIG. 2, terminals 15-1 and 15- of the primary coil 15a of the rotary transformer are shown.
The inductance L ₁ between the secondary coil 15
The inductance L ₂ of the primary coil 15a is smaller than the inductance L 2 of the primary coil 15a, and the inductance L ₃ of the terminals 15-1 and 15-3 of the primary coil 15a is larger than the inductance L ₂ of the secondary coil 15b. Therefore, if the inductance of the primary coil 15a and the secondary coil 15b is the same as in the conventional example and no boosting effect of the induced voltage is obtained, or if the secondary coil 15b is made larger and the transmission Unlike the case where the voltage is increased only when the voltage is increased, in this embodiment, the ratio of the inductance of each coil 15a, 15b, that is, in the case of transmission, it is proportional to L ₂ /L ₁ , and in the case of reception, it is proportional to L ₃ /L ₂ . It is clear from the law of electromagnetic induction that the induced voltage increases accordingly. Table 1 shows piezoelectric vibrators 13a, 13b, 13c
An example of actual measurements of received voltages actually obtained by a probe using the rotary transformer according to this embodiment and a conventional rotary transformer will be shown below. In addition, ultrasonic waves are emitted into the water, and the received voltage is
This is due to reflected waves from the aluminum block in the water.

[Table] As can be seen from Table 1, it is clear that by using the rotary transformer of this embodiment, the received voltage can be obtained higher by about 11.4 dB (20 log ₁₀ 3.2/0.86≈11.4) than the conventional one. In the case of this embodiment, the inductance of each coil 15a, 15b of the rotary transformer is
Needless to say, the impedances are set so as to match the electric impedances of the electric circuits for driving the piezoelectric vibrators 13a, 13b, and 13c. That is, by simply setting the inductance of each coil 15a, 15b, there is no need to take the trouble of providing circuit means for improving sensitivity and S/N in the electrical circuit system of the main unit, as in the conventional case. Note that in this embodiment, the piezoelectric vibrators 13a, 13
Although an example is shown in which a rotary transformer is used as a contactor for scanning an ultrasonic beam in a fan shape by rotating piezoelectric vibrators 13a, 13c,
Needless to say, the present invention can also be applied to a contactor that performs fan-shaped scanning by reciprocating vibrations of 13b and 13c. Furthermore, in this embodiment, the primary coil 15a is a coil with an intermediate tap, but in addition, two coils for transmission and reception are made separately, and these are combined into one coil.
It is also possible to combine them into a primary coil. In addition to this embodiment, the secondary coil 15b is divided into a transmitting coil and a receiving coil, and a reed switch means for switching between transmitting and receiving is provided on the rotary support 1, and a transmitting coil and a reed switch means for controlling the switching means are provided. It is also possible to form a receiving electromagnet on the inner wall of the container 5 and control the electromagnet to switch between transmitting and receiving from the main unit. Effects of the Invention As explained above, in configuring the coil of a rotary transformer, the present invention makes the inductance of the primary coil smaller than the inductance of the secondary coil during transmission, and conversely increases during reception. Since the inductance of the primary or secondary coil is made different during transmission and reception, a boosting effect due to electromagnetic induction is obtained during both transmission and reception, resulting in improved sensitivity and S/N.
It is possible to further improve various characteristics such as Further, according to the present invention, since the coil of the rotary transformer can be configured for transmission and reception, the electrical impedances of the piezoelectric vibrator, the transmission circuit system, and the reception circuit system are best matched. It is extremely easy to design and manufacture, and it is possible to improve the sensitivity, S/N, and other characteristics of the entire device.

[Brief explanation of drawings]

Fig. 1A is a schematic configuration diagram of a conventional mechanical fan-shaped scanning type ultrasonic probe, Fig. 1B is a schematic side view of the rotary support of the same probe, and Fig. 1C is a schematic diagram of the same probe. FIG. 2 is a circuit diagram showing the general operating principle of an embodiment of the ultrasonic probe of the present invention. 1...Rotating support body, 9...Motor, 13a, 1
3b, 13c...piezoelectric vibrator, 14a, 14b,
14c... Reed switch, 15a... Primary coil of rotary transformer, 15b... Secondary coil of rotary transformer, 16... Fixed permanent magnet, 15-1, 15-2, 15-3... Primary coil terminal.

Claims (1)

[Scope of Claims] 1. A support body provided with a piezoelectric vibrator that transmits and receives an ultrasonic beam, and a rotary transformer that connects an electric signal for transmitting and receiving the ultrasonic beam to the piezoelectric vibrator in a non-contact manner. , further comprising a drive means for rotating or reciprocating the support body, and the inductance of at least one of the primary coil and the secondary coil constituting the rotary transformer is made different between the time of transmission and the time of reception. Ultrasonic probe. 2. The ultrasonic probe according to claim 1, wherein the inductance of the primary coil of the rotary transformer is smaller than the inductance of the secondary coil during transmission and larger during reception. 3. The inductance of the primary coil of the rotary transformer during transmission and reception, and the inductance of the secondary coil facing the primary coil are determined by each of the piezoelectric vibrator and the electric circuit means for driving the piezoelectric vibrator. The ultrasonic probe according to claim 1, wherein the ultrasonic probe is set to a value that matches the electric impedance of the ultrasonic probe.