JPH0696005B2 - Ultrasonic diagnostic equipment - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention is used for diagnosing a subject by processing a received signal based on a reflected wave of an ultrasonic wave transmitted toward the subject from the subject. The present invention relates to an ultrasonic diagnostic device.

[Technical Background of the Invention and Problems Thereof] In an ultrasonic diagnostic apparatus, an ultrasonic probe having a vibrator for transmitting and receiving ultrasonic waves, and a transmission signal (driving pulse) applied to the vibrator of the ultrasonic probe. Alternatively, it is also referred to as an excitation pulse), and is connected to a device main body that processes a reception signal (reception echo) from the vibrator by a cable (conductive wire).

By the way, since the transducer in the receiving state of the device functions to receive the reflected wave of the ultrasonic wave and convert it into an electric signal, it can be regarded as a kind of signal source from the device body side. From the general principle of the voltage transmission path, the lower the output impedance on the signal source side from the point of view of signal loss, the better, but the output impedance of the oscillator is relatively high, and therefore the distributed capacitance on the voltage transmission path including the cable is high. As a result, the received signal loss is large and the S / N ratio (signal-to-noise ratio) tends to decrease. Needless to say, the decrease in the S / N ratio causes deterioration in the image quality of the visualized ultrasonic image.

Therefore, conventionally, in order to improve the S / N ratio, (1) the reflected wave intensity of ultrasonic waves is increased by increasing the voltage of the transmission signal applied to the transducer, and (2) the cable is used by taking resonance. Measures such as increasing the signal level by canceling out the capacitance of the oscillator and the capacitance of the oscillator are taken.

However, in the case of the above (1), the power of the ultrasonic wave transmitted toward the subject, especially the living body becomes large, and there is a problem in terms of the safety of the living body. Regarding the power of ultrasonic waves, legal regulations have been strengthened in recent years. In the case of the above (2), (a) the pulse width of the ultrasonic wave is inevitably widened, which lowers the resolution in the depth of field direction. (B) Resonance impairs the original waveform, so tissue Identification (Ti
It becomes inappropriate when performing ssue characterization, etc. (c) The resonance coil must be changed for each ultrasonic probe used, (d) Q of the resonance circuit is required to obtain the desired S / N ratio. (Sharpness)
However, if this is done, the high and low frequencies of the frequency spectrum will be suppressed, so the azimuth resolution (scan direction resolution) will decrease, and the penetration (S / N ratio at a large depth of field) There are various problems such as deterioration.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reception signal having a good S / N ratio without increasing the voltage of the transmission signal or taking resonance. An object of the present invention is to provide an ultrasonic diagnostic apparatus that can be incorporated in the apparatus body.

[Summary of the Invention] The present invention transmits and receives an ultrasonic probe having an oscillator for transmitting and receiving ultrasonic waves, a transmission signal for exciting the oscillator, and a reception signal from the oscillator via a signal transmission path. In an ultrasonic diagnostic apparatus, comprising: a transmitter / receiver for processing the received signal for diagnosis, a collector-grounded transistor having a base side connected to the transducer and an emitter side connected to the transmitter / receiver, and the transistor connected in parallel to the transistor. And a first diode provided so as to transmit a transmission signal from the transmitting / receiving means to the oscillator and a base side and an emitter side of the transistor, respectively, to prevent the transmission signal from sneaking into the transistor. A transmission / reception signal transmission means including a first diode and a second diode for transmitting the transmission signal from the transmission / reception means. Through said first diode transmits to the vibrator, and is characterized in that inputs the received signal from the transducer to the transmitting and receiving means via said transistor.

[Examples of the Invention] Hereinafter, the present invention will be specifically described with reference to Examples.

FIG. 1 is a circuit diagram showing a main part of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. Reference numeral 1 is a vibrator in an ultrasonic probe, 2 is a transmission / reception signal transmitting means, 3 is an apparatus body, 4 is a cable. Is.

The ultrasonic probe is composed of a plurality of transducers arranged in an array, and FIG. 1 shows only one of them.

The transmission / reception signal transmitting means 2 is provided corresponding to the transducer in the ultrasonic probe, allows the transmission signal (drive pulse) used for exciting the transducer 1 to pass with low loss, and It has a function of taking in the received signal from the device with high impedance and outputting the received signal with low impedance. Various circuit configurations are conceivable for realizing such a function, but in the present embodiment, a transistor (bipolar) Tr whose collector is grounded is mainly configured. That is, the reception signals (reception echoes) from the vibrator 1 are diodes connected in series with each other.
It is adapted to be transmitted to the base of the transistor Tr via D1 and D2, and the emitter output of the transistor Tr is adapted to be transmitted to the device body 3 via the diode D3 and the cable 4. The resistors R1 and R2 are for determining the potential at the point B, and the diodes D1 and D2 are turned on by the current flowing through the resistors R1 and R2. Diodes D4 and D5 connected in parallel with each other are provided between the cathodes of the diodes D1 and D3. Transmit signal is diode D
It is applied to the vibrator 1 via 5. The diode D4 is for promptly discharging the electric charge charged in the capacitive component of the vibrator 1. The resistor R3 connected to the cathode of the diode D3 is for flowing the emitter current of the transistor Tr.

Further, the device body 3 is configured to include a transmission circuit that generates a transmission signal, a reception circuit that captures a reception signal, a signal processing circuit that processes the captured reception signal, a display device that displays the processing result, and the like. Has been done. The structure of the apparatus main body is the same as the conventional one, and thus detailed description thereof will be omitted.

The operation of the embodiment apparatus having the above configuration will be described.

<Transmission> The drive pulse output from the transmission circuit of the apparatus main body 3, specifically, the pulser is transmitted to the transmission / reception signal transmission means 2 via the cable 4. The transmitted drive pulse passes through the transmission signal passing diode D5 and is applied to the vibrator 1,
As a result, ultrasonic waves are transmitted from the vibrator 1. The potential of the driving pulse is usually several tens to one hundred and several tens of volts, and V _CC , V
_DD1 and V _DD2 are about several volts. Therefore, at the time of transmission, the diodes D1 and D3 are reverse-biased by the drive pulse to be in the off state. Therefore, no drive pulse is applied between the base and emitter of the transistor Tr, and damage to the transistor Tr is prevented. In this sense, the diodes D1 and D3 are called protection diodes.

In the above transmission operation, the drive pulse passes through the diode D5 in the forward direction and is applied to the vibrator 1, so that the loss of the drive pulse (transmission signal) is extremely small.

<Reception> The reflected wave of the ultrasonic wave transmitted from the oscillator 1 is again transmitted to the oscillator 1.
The received signal (reception echo) by this ultrasonic wave reception is taken into the transmission / reception signal transmission means 2. During the period when the drive pulse is not applied to vibrator 1, V _CC
And V _DD1 and V _DD2 are biased, and the transistor Tr is turned on. Therefore, the diodes D1 and D2 are forward biased by the currents flowing through the resistors R1 and R2 to be in the ON state, and the diode D3 is forward biased by the emitter current of the transistor Tr to be in the ON state. With reference to the base of the transistor Tr, the potential at the point B becomes lower by the voltage drop of the diodes D1 and D2, and the potential at the point A becomes lower by the voltage drop between the base and emitter of the transistor Tr and the diode D3. Since the voltage drop between the base and the emitter of the transistor Tr is almost equal to the voltage drop of the diode D3, the points A and B become equipotential, and the diodes D4 and D5 are turned off. That is, since the transistor Tr operates as an emitter follower, the emitter current changes according to the received signal received. The feature of the emitter follower (grounded collector) is its high input impedance (tens of KΩ).
Above), the output impedance is low (several to several tens Ω). The voltage gain is almost 1, but the current gain is large, and the base and emitter are in phase. The change of the emitter current is converted into the change of the voltage by the resistor R3, and the cable 4
Is transmitted to the apparatus main body 3 via. The received signal transmitted with low impedance is taken into the receiving circuit in the apparatus main body 3 and provided for signal processing in the signal processing circuit. The signal processing may form an ultrasonic image of the subject, but may also perform arithmetic processing for tissue identification of the subject.

In the above receiving operation, since the received signal is transmitted with low impedance, it is unlikely to be adversely affected by the distributed capacitance of the cable 4 and the like, and the signal loss is extremely small. Therefore, compared to conventional devices that transmit received signals with high impedance, S /
The N ratio is improved.

The conductive path connecting the vibrator 1 and the input end of the transmission / reception signal transmitting means 2 is preferably as short as possible because the output impedance of the vibrator 1 is high. For example, it is preferable to provide the transmission / reception signal transmitting means 2 in the ultrasonic probe. In this case, in order to reduce the size of the ultrasonic probe, the transmission / reception signal transmission means 2 should be IC
(Integrated circuit) is recommended. Further, it is preferable that the resistance R3 and the like be provided on the apparatus main body 3 side to reduce the size of the transmission / reception signal transmitting means 2 and reduce the amount of heat generated in the ultrasonic probe.

Next, another embodiment of the present invention will be described with reference to FIG.

2 is different from that shown in FIG. 1 in that the diode D2 serially connected to the diode D1 is omitted and the diode D6 is serially connected to the diode D4.

When diodes D1 and D2 are connected in series as shown in Fig. 1, temperature compensation can be performed because the PN junction between the base and emitter of transistor Tr, diode D3 and diodes D1 and D2 are balanced. However, the parasitic capacitance of the diode is the anode of each of the diodes D1 and D2,
It exists in the cathode, the anode of the diode D4, and the cathode of the diode D5. On the other hand, if the diode D2 is omitted and only the diode D1 is used as shown in FIG. 2, the parasitic capacitance is reduced by the amount of the diode D2. Therefore, when prioritizing temperature compensation, use the circuit configuration shown in FIG.
In order to further improve the S / N ratio, it is preferable to adopt the circuit configuration shown in FIG. In the receiving state, all of the diodes D4, D5, D6 are off, so
The parasitic capacitance existing on the anode and cathode sides of D4 does not matter.

Although the embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to the above embodiments and various modifications can be made.

For example, although the bipolar transistor is applied in the above embodiment, a field effect transistor (FET) or an operational amplifier may be applied.

[Effects of the Invention] As described in detail above, according to the present invention, an ultrasonic wave capable of capturing a reception signal having a good S / N ratio into the apparatus body without raising the voltage of the transmission signal or taking resonance. A diagnostic device can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a main part of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram for explaining another embodiment of the present invention. 1 ... Oscillator 1, 2 ... Transmitting / receiving signal transmitting means, Tr ... Transistor, D1, D3 ... Protecting diode, D5 ... Transmitting signal passing diode.

Claims (3)

[Claims] 1. An ultrasonic probe having an oscillator for transmitting and receiving ultrasonic waves, and a transmitting and receiving means for transmitting and receiving a transmission signal for exciting the oscillator and a reception signal from the oscillator through a signal transmission path. In an ultrasonic diagnostic apparatus for processing the received signal for diagnosis, a collector-grounded transistor having a base side connected to the transducer and an emitter side connected to the transmission / reception means, and the transmission / reception in parallel with the transistor. A first diode provided to transmit a transmission signal from the means to the vibrator; and a first diode connected to the base side and the emitter side of the transistor to prevent the transmission signal from sneaking into the transistor. A transmission / reception signal transmission unit including a second diode is provided in the signal transmission path, and a transmission signal from the transmission / reception unit is transmitted to the first transmission line. An ultrasonic diagnostic apparatus, which transmits to a transducer via a diode and inputs a reception signal from the transducer to the transmitting / receiving means via the transistor. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the transmission / reception signal transmitting means is integrated circuit. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the transmission / reception signal transmitting means is provided inside the probe head.