JP4024914B2 - Ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an impedance matching circuit incorporated in a probe together with a vibrator, which is used for the purpose of reducing a loss caused by a cable or the like in a reception signal generated by the vibrator.
[0002]
[Prior art]
The ultrasonic diagnostic apparatus is roughly composed of an apparatus main body and an ultrasonic probe connected to the apparatus main body with a cable. The ultrasonic probe generates mechanical vibrations by a transmission signal (also called a drive pulse or an excitation pulse) from the device body, generates ultrasonic waves, receives reflected waves from the body, and converts them into electrical signals. Built-in transducers for multiple channels for conversion.
[0003]
By the way, in the reception state, the vibrator functions to receive an ultrasonic reflected wave and convert it into an electric signal, so that it can be regarded as a kind of signal generation source from the apparatus main body side. From the general principle of the voltage transmission path, the lower the output impedance on the signal source side, the better the signal loss, but the higher the output impedance of the vibrator, the higher the capacitive component on the voltage transmission path including the cable. As a result, there is a problem that the loss of the received signal is increased, the S / N ratio (signal to noise ratio) is lowered, and the image quality of the ultrasonic image is lowered.
[0004]
In order to solve this problem, conventionally, as disclosed in Japanese Patent Application No. 60-252437, Japanese Patent Application Laid-Open No. 62-112537, and Japanese Patent Publication No. 6-96005, reception from an ultrasonic transducer is performed. In order to reduce the loss of the signal in the signal transmission path, an impedance conversion circuit is built in the probe.
[0005]
[Problems to be solved by the invention]
Conventionally, this impedance conversion circuit has been integrated into an integrated circuit (IC) so as to be built in the probe. However, there is a current limit to the high voltage IC technology suitable for the purpose. In addition, the amplitude of the ultrasonic transmission signal could not be sufficiently increased. In addition, there is a parasitic current flowing into a parasitic transistor peculiar to IC, and this is a major factor of heat generation. Furthermore, the circuit configuration of the impedance conversion circuit with a high breakdown voltage element is an obstacle to miniaturization because the high breakdown voltage element is generally large in size.
An object of the present invention is to provide an ultrasonic diagnostic apparatus having a high-voltage impedance conversion circuit that can be constructed at low cost and in a small size.
[0006]
[Means for Solving the Problems]
The present invention relates to an ultrasonic diagnostic apparatus comprising: an ultrasonic probe including a vibrator and an impedance conversion circuit; an apparatus main body; and a cable that electrically connects the ultrasonic probe and the apparatus main body. The impedance conversion circuit transmits a high-voltage transmission signal from the device main body to the transducer in parallel with the transistor element having a base side connected to the vibrator and an emitter side connected to the cable, and the transistor element. A first diode element provided so as to perform, a second diode element for discharging the charge accumulated in the vibrator by the transmission signal, and a resistor for suppressing an excessive current to the transistor element High impedance when the transmission signal is applied to the element and the collector side of the transistor element, A high breakdown voltage element having a low impedance when the transmission signal is not applied to the collector side of the transistor element side, and the transistor element, the first diode, the second diode, and the resistor are integrated in an integrated circuit. The high-voltage element is externally attached to the integrated circuit, the substrate of the integrated circuit is connected to the output side, and the integrated circuit is formed by a low-voltage process .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to embodiments. FIG. 1 shows the configuration of one channel of the main part of the ultrasonic diagnostic apparatus according to this embodiment. This ultrasonic diagnostic apparatus includes an ultrasonic probe 1, an apparatus main body 3, and a cable 2 for electrically connecting the ultrasonic probe 1 and the apparatus main body 3. The ultrasonic probe 1 incorporates a vibrator 4 and an impedance conversion circuit 5. In the case of a multi-channel type probe, impedance conversion circuits 5 are provided for the number of channels.
[0009]
The impedance conversion circuit 5 transmits a high-voltage, high-frequency transmission signal (drive pulse) supplied from the apparatus main body 3 via the cable 2 to excite the vibrator 4 to the vibrator 4 with low loss. Is received with a high impedance, and the received reception signal is output to the cable 2 side with a low impedance.
[0010]
In order to realize such a function, various circuit configurations are conceivable. In the present embodiment, a circuit composed mainly of a collector-grounded transistor (bipolar transistor) Tr is employed. In other words, the reception signal (reception echo) from the transducer 4 is transmitted to the base “B” of the transistor Tr, and the output of the emitter “E” of the transistor Tr passes through the resistor 3 and the cable 3. Is transmitted to the apparatus body 3. Resistors R1 and R2 are adjusted and provided to determine the potential at point (B). Diodes D1, D2, and D3 are provided between the point (A) and the point (B), and the transmission signal is applied to the vibrator 4 via the diodes D1, D2, and D3. The Zener diode D4 is provided to play a role of preventing the transistor Tr from being destroyed by making the Zener voltage equal to or lower than the withstand voltage of the transistor Tr.
[0011]
The diode D5 is a high voltage element (high withstand voltage element) having a withstand voltage equal to or higher than the peak value of the transmission pulse, and plays a role of preventing the transmission pulse from flowing into the power supply voltage V1. Since this diode D5 is electrically separated from the external power source V1, other elements (Tr, R1, R2, R3, D1, D2, D3, D4) are constructed in the integrated circuit 6 by a low-voltage process. Can do. Independently of this, the diode D5 is externally attached to the integrated circuit 6.
[0012]
The apparatus body 3 includes a current circuit for causing the emitter current of the transistor Tr to flow, a transmission circuit for generating a transmission signal, a reception circuit for capturing a reception signal, a signal processing circuit for processing the received reception signal, and a processing signal thereof However, since the configuration of the apparatus main body 3 is the same as that of the prior art, detailed description thereof is omitted.
[0013]
Next, the effect | action by the above structures is demonstrated.
(Send)
In FIG. 2, a signal path at the time of transmission is indicated by a thick line. A drive pulse output from the transmission circuit in the apparatus main body 3, specifically, a pulser, is transmitted to the impedance conversion circuit 5 through the cable 3. The transmitted drive pulse passes through the transmission signal passing diode D 3 and is applied to the vibrator 4. The electric charge stored in the vibrator 4 is discharged through the diodes D1 and D2. Thereby, an ultrasonic wave is transmitted from the vibrator 4.
[0014]
The potential of the drive pulse is usually about several + to several hundred + volts, and the power supply voltage V1 is about several volts. For this reason, during transmission, the drive pulse reversely biases the emitter and collector of the transistor Tr, the transistor Tr is turned off, and passes through the diodes D1 and D2 when the drive pulse falls. Therefore, the forward voltage (about 1.4 V) of the diodes D1 and D2 is not applied between the base and the emitter of the transistor Tr, and the transistor Tr can be prevented from being damaged.
[0015]
Further, since charges are accumulated in the parasitic capacitance C1 existing on the terminal side of the collector “C” of the transistor Tr, a reverse voltage is applied between the collector and the emitter of the transistor Tr when the drive pulse falls, but the Zener voltage of the Zener diode D4 Is set to be equal to or lower than the withstand voltage of the transistor Tr to prevent the transistor Tr from being damaged.
[0016]
In the above transmission operation, the drive pulse passes through the diodes D1, D2, D3 and is applied to the vibrator 4, so that the loss of the drive pulse (transmission signal) is extremely small. Also, by using a high-voltage diode D5 externally attached, the elements (Tr, R1, R2, R3, D1, D2, D3, D4) can be integrated by a low-voltage process, and a high-voltage drive pulse can be applied. The sensitivity can be improved.
(Receive)
In FIG. 3, a signal path at the time of reception is indicated by a thick line. Reflection of the ultrasonic wave transmitted from the transducer 4 is received again by the transducer 4, and a reception signal (reception echo) due to reception of this ultrasonic wave is taken into the impedance conversion circuit 5. In a period in which the drive pulse is not applied to the vibrator 4, the bias potential is determined by the power supply voltage V1 and the resistors R1 and R2, and the transistor Tr is in a class A operation state. That is, since the transistor Tr operates as an emitter follower, the emitter current changes according to the received reception signal.
[0017]
The emitter follower is characterized by high input impedance (several tens of KΩ or more) and low output impedance (several to several tens of Ω). The voltage gain is approximately 1, but the current gain is large, and the base and the emitter are in phase. The change in the emitter current is converted into a change in voltage by the resistor R4 and transmitted to the apparatus main body 3 through the cable 3. The received signal transmitted with low impedance is taken into the receiving circuit in the apparatus main body 3 and used for signal processing in the signal processing circuit. The signal processing may form an ultrasonic image of the subject, or may perform arithmetic processing for tissue identification of the subject.
[0018]
In the above receiving operation, since the received signal is transmitted with low impedance, it is hardly affected by the capacitive component of the cable 3 or the like, and the signal loss is extremely small. For this reason, the S / N ratio is improved as compared with the conventional device that transmits the received signal with high impedance.
[0019]
The conductive path connecting the vibrator 4 and the input end of the impedance conversion circuit 5 is preferably as short as possible because of the high output impedance of the vibrator 4. For example, it is preferable to provide the impedance conversion circuit 5 in the ultrasonic probe. In this case, the ultrasonic probe needs to be miniaturized because the doctor or engineer always scans the subject, and the impedance conversion circuit 5 may be integrated into an IC (integrated circuit). In the case of IC, a high breakdown voltage process is required to increase the transmission voltage, but in this embodiment, a high breakdown voltage diode is used as an external component, so that the transmission / reception signal transmission means is integrated in a low breakdown voltage process. And further miniaturization becomes possible.
[0020]
In addition, it is preferable to reduce the impedance conversion circuit 5 and reduce the amount of heat generated in the ultrasonic probe 1 by providing the resistor R4 and the like on the apparatus body 2 side .
As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible.
[0021]
【The invention's effect】
According to the present invention, when a high-voltage transmission signal is applied to the collector side of the transistor element, the transistor element, the first diode element, the second diode element, and the resistor are electrically disconnected from the outside by the high-voltage device. In addition, since a high voltage is not applied to the transistor elements other than the high withstand voltage device, these transistor elements can be made into an IC by a low pressure process, and a high withstand voltage impedance conversion circuit can be constructed at low cost and in a small size. Further, since the withstand voltage performance is determined only by the high withstand voltage device, the amplitude of the transmission signal can be easily increased.
Further, since the substrate of the integrated circuit is connected to the output side, the substrate voltage becomes the same as the output voltage, and heat generation due to the parasitic current of the parasitic transistor can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a main part of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a signal path during transmission.
FIG. 3 is a diagram showing a signal path during reception.
[Explanation of symbols]
1 ... ultrasonic probe,
2 ... The device body,
3 ... Cable
4 ... vibrator,
5 ... impedance conversion circuit,
6: Integrated circuit (IC).

Claims (3)

In an ultrasonic diagnostic apparatus comprising an ultrasonic probe including a vibrator and an impedance conversion circuit, an apparatus main body, and a cable for electrically connecting the ultrasonic probe and the apparatus main body,
The impedance conversion circuit is
A transistor element having a base side connected to the vibrator and an emitter side connected to the cable;
A first diode element provided in parallel with the transistor element and for transmitting a high-voltage transmission signal from the apparatus main body to the vibrator;
A second diode element for discharging the charge accumulated in the vibrator by the transmission signal;
A resistance element for suppressing an excessive current to the transistor element;
A high withstand voltage element showing a high impedance when the transmission signal is applied to the collector side of the transistor element, and a high withstand voltage element showing a low impedance when the transmission signal is not applied to the collector side of the transistor element;
The transistor element, the first diode, the second diode, and the resistor are configured in an integrated circuit, the high-breakdown-voltage element is externally attached to the integrated circuit, and the substrate of the integrated circuit is connected to the output side. ,
The ultrasonic diagnostic apparatus, wherein the integrated circuit is formed by a low voltage process .   The ultrasonic diagnostic apparatus according to claim 1, wherein the high breakdown voltage element is a diode element. In the impedance conversion circuit inserted between the first electric circuit and the second electric circuit,
A transistor element having a base side connected to the first electric circuit and an emitter side connected to the second electric circuit;
A first diode element provided in parallel with the transistor element and for sending a high voltage signal from the second electric circuit to the first electric circuit;
A second diode element for discharging the charge accumulated in the first electric circuit by the high voltage signal;
A resistance element for suppressing an excessive current to the transistor element;
A high-voltage element that exhibits a high impedance when the high-voltage signal is applied to the collector side of the transistor element, and a high-voltage element that exhibits a low impedance when the high-voltage signal is not applied to the collector side of the transistor element;
The transistor element, the first diode, the second diode, and the resistor are configured in an integrated circuit, the high-breakdown-voltage element is externally attached to the integrated circuit, and the substrate of the integrated circuit is connected to the output side. ,
The integrated circuit is formed by a low voltage process .

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