JPH05212037A - Ultrasonic diagnostic system - Google Patents

Abstract

PURPOSE:To correspond to the large diameter channel processing while increasing the connectable number for the same tap with the delay line of the reception signal from current-converted multiple vibrators in an ultrasonic diagnostic device displaying the sectional image of a testee by means of a focusing control of ultrasonic beam using a linear array with multiple ultrasonic vibrators. CONSTITUTION:A voltage/current conversion means 5 is provided with voltage/ current converters VI1 to VIn converting input voltage signals VSIG into current signals ISIG at its output with the constant bias current IDC supplied and constant current sources IG1 to IGn supplying the bias current IDC to the VI1 to VIn so as to prevent the bias current IDC from being outputted at a tap changeover means 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus for displaying a tomographic image of a subject by controlling the focus of an ultrasonic beam using a linear array having a plurality of ultrasonic transducers. In an ultrasonic diagnostic apparatus, high voltage pulses are applied to a plurality of ultrasonic transducers arranged as a linear array to drive them, and an ultrasonic beam is emitted into the subject to receive reflected waves from each tissue. Then, each received signal from the transducer is delayed by tap switching with respect to the delay line so that the ultrasonic beam is focused on a specific portion inside the subject. In order to facilitate the addition when switching a plurality of signals to the taps, the current signals are converted before the delay to simply add the currents and delay them, and output them as one scanning signal.

However, the current capacity of the output line with respect to one tap of the delay line is limited to, for example, 30 mA due to the IC, and a predetermined dynamic range (a distortion-free input voltage Output current includes the DC bias current flowing to obtain a range), and when multiple received signal currents are switched to one tap terminal, the number of signals that can be tap-connected by adding the bias currents even if there are no signals Is limited to 64 elements, 96 elements,
There is a problem that it cannot deal with a large-diameter channel such as 128 elements, and improvement of this point is desired.

[0003]

2. Description of the Related Art FIG. 4 is an explanatory view of a conventional ultrasonic diagnostic apparatus. In FIG. 4, a control means 1 sequentially sends a driving pulse to drivers DR _{1 to} DR _n of a transmission driver group 2 at a predetermined timing. The transmission drivers DR _{1 to} DR _n generate high voltage pulses based on the input drive pulse, and the ultrasonic transducer group 3
The corresponding ultrasonic transducers TR _{1 to} TR _n are driven to irradiate the subject with an ultrasonic beam.

The ultrasonic waves reflected by the tissue boundary surface in the subject are returned to the ultrasonic transducers TR _{1 to} TR _n and converted into electric signals. Received signal from each transducer TR ₁ to Tr _n is amplified by the corresponding amplifier of amplifier PR ₁ to PR _n preamplifier group 4, the current-voltage converter VI of the voltage-current converter group 5
_It is converted into a current signal by the corresponding converter of _{1 to} VI _n and connected to the tap selection switch group 6.

The tap selection switch group 6 is selectively connected to a plurality of input taps of the delay line 7 so that each of the current-converted received signals can be delayed by a predetermined time. Each received signal (current signal) receives a necessary delay while passing through the delay line 7, is added to each other, is output as one scanning signal, and a tomographic image of the subject is displayed on the CRT monitor.

In order to focus the ultrasonic beam on a specific portion in the subject, for example, the position F shown in FIG. 5, the distance difference between each transducer position 1, 2, ... depending depending on the ultrasonic arrival or reception time difference, the timing of the drive pulse transmission given to each transducer TR ₁ to Tr _n, also the delay time reception given to the received signals from each transducer TR ₁ to Tr _n The distribution may be controlled so as to have the distribution shown by the solid line in FIG.

Actually, however, the transmission drive timing or the reception delay distribution is within 1/16 of one cycle with respect to the center frequency of the ultrasonic signal transmitted and received by the ultrasonic transducer with respect to the solid line in FIG. Even if the error is positive or negative, there is substantially no problem, so the time distribution shown by the dotted line in FIG. 6 may be used.
Therefore, the taps of the delay line 7 may be arranged so as to be arranged with a time difference of ⅛ or less of one cycle.

The received signals from the transducers TR _{1 to} TR _n are current / voltage converters VI _{1 to} VI _n of the voltage / current converter group 5.
Since it is converted into a current signal by, the signals connected to the same tap of the delay line 7, and the signals passing through the delay line and the signals newly input from the taps can be added as a current, and the special adder There is an advantage that it is possible to add easily without the need to provide the like.

[0009]

By the way, the voltage-current converters VI _{1 to} VI _n of the voltage-current converter group 5 are usually composed of the circuit shown in FIG. 7 which uses transistors or the like. In order to operate the transistor Q1 that performs voltage-current conversion in this circuit, it is necessary to always supply the DC bias current I _DC . That is, when the voltage waveform V _SIG of the received signal from the oscillator obtained from the preamplifier is as shown in FIG. 8A, the output of the voltage-current converter VI, that is, the current waveform of the collector of the transistor Q1 is shown in FIG. As shown in (b), the current (I _DC + I) obtained by adding the signal current I _SIG to the DC bias current I _DC.
SIG ). Therefore, the DC bias I _DC is always flowing regardless of the input signal.

Therefore, when received signals from a plurality of vibrators are input to the taps of the same delay line, the current flowing through the output line of the tap changeover switch group 6 connected to the taps may be excessive. .. Usually, a semiconductor switch IC or the like is used as the tap changeover switch, but the passing current per switch or the output current of the terminal is about 30 mA or less at the maximum rating.

On the other hand, in the case of the voltage-current converter VI using the circuit of FIG. 4, the maximum input voltage amplitude that can be input to the voltage-current converter VI without distortion, the so-called dynamic range, must be (I _DC · R _e ) or less. I have to. Therefore, in order to increase the maximum input voltage amplitude (I _DC · R _e ), it is necessary to increase the DC bias current I _DC or the emitter resistance R _e that is AC-connected by the capacitor C2. However, the voltage gain from the input of the voltage-current converter VI to the output of the delay line 7 is approximately Z ₀ / (2 · R _e ), where Z ₀ is given by the characteristic impedance of the delay line, so the emitter resistance R _e is There is a limit to increasing the value because the voltage gain decreases.

For example, the maximum input voltage amplitude is 100 mV, the voltage gain is 1.0 times, and the characteristic impedance 10 of the delay line 7 is 10.
If it is 0Ω, then R _e = 50Ω and I _DC = 2 mA. Therefore, the number of signals from the vibrator that can be connected to the same tap of the delay line 7 is limited to 15 in this case. But,
In recent years, the demand for higher image quality has increased, and the number of ultrasonic transducers has increased to a large number of channels, for example, 64 elements, 96 elements, and 128 elements. In such a device, the number of transducers that can be connected to the same tap is 15. Being a degree is a very difficult limitation.

When signal currents from a plurality of oscillators are switched and connected to the same tap of the delay line 7, the tap changeover switch group 6 and the buffer amplifier used for the delay line 7 are saturated. Similarly, the number of oscillators that can be connected to the same tap is limited. FIG. 9 shows a switch matrix of the tap changeover switch group 6.
The output currents from the V converters IV _{1 to} IV _n are input to the input buffer amplifiers via BA _{1 to} IBA _n , and the signal currents selected by the switches are output buffer amplifiers OBA _{1 to} OBA _n.
Is output to the tap of the delay line 6 via.

FIG. 10 shows a specific circuit of the delay line 7. Since one delay line has a limited delay time, a plurality of delay lines 7a and 7b are connected in series and a buffer amplifier is provided between them. Connected via BA. Thus, the output buffer amplifier OBA of the tap changeover switch group 6
_{1 to} OBA _n and the buffer amplifier BA of the delay line 7, when an excessive current due to the addition of the bias currents flowing to obtain the dynamic range in the voltage-current converter VI flows, the buffer amplifier becomes saturated and the received signal is received. No current can be output, and as a result, the number of signals that can be switched to one tap is limited to 15, for example, and it is not possible to cope with a large diameter channel.

The present invention has been made in view of such conventional problems, and increases the number of connectable delay lines of reception signals from a plurality of current-converted oscillators to the same tap to increase the number of large-diameter channels. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of coping with the increase in the number of users.

[0016]

FIG. 1 illustrates the principle of the present invention. First, according to the present invention, as shown in FIG. 1A, a transmission drive in which a plurality of adjacent ultrasonic transducers TR _{1 to} TR _n are driven by applying a high voltage pulse to irradiate the inside of a subject with an ultrasonic beam. Means 2; reception amplification means 4 for receiving the reflected waves of the ultrasonic beam from each tissue inside the subject by the ultrasonic transducers TR _{1 to} TR _n , converting them again into electric signals and amplifying them.
The voltage-current conversion means 5 for converting the received signal voltage from the reception amplification means 4 into a current signal, the delay line 7 having a plurality of taps, and the ultrasonic beam are focused on a specific portion inside the subject. As described above, each tap of the delay line 7 is selectively connected to each of the reception signals whose current is converted by the voltage-current conversion means 5 corresponding to the ultrasonic transducers TR _{1 to} TR _n to give a predetermined delay, and It is intended for an ultrasonic diagnostic apparatus that includes a tap switching unit 6 that obtains one scanning signal by adding and that displays the scanning signal from the delay line 7.

In the present invention for such an ultrasonic diagnostic apparatus, the voltage / current converting means 5 inputs the input voltage signal V _{SIG in} the state where a constant bias current I _{DC is made} to flow for each received signal.
To current signal I _SIG for output
I ₁ to VI _n and the voltage-current converter VI ₁ to VI _n to a constant current source IG ₁ ~IG _n supplying the bias current I _DC, the bias current flowing through the voltage-current converter VI ₁ to VI _n It is characterized in that I _DC is prevented from being output to the tap switching means 6 side.

Here, each of the voltage-current converters VI _{1 to} VI _n has a first transistor Q1 for converting an input voltage into a current signal and outputting it, as shown in FIG. 1B, and a first transistor. A capacitor C1 for AC coupling the input voltage I _SIG to the base of Q1; a first DC bias circuit (R1, R2, R3) for flowing a constant DC bias current I _DC between the collector and emitter of the first transistor; AC bias circuit for supplying a signal current I _SIG corresponding to the input voltage V _SIG to the collector and the emitter of the first transistor Q1 (C2, R
e) and.

Each of the constant current sources IG _{1 to} IG _n has a second transistor Q2 for flowing a constant current I _SIG into the collector of the first transistor Q1 and a first DC bias circuit (R1, R2, R3). And a second DC bias circuit (R4, R5, R6) symmetrically arranged with. Further, each of the voltage-current conversion circuits VI _{1 to} VI _n includes an NPN transistor operating as a first transistor Q1 with a negative power source, and each of the constant current sources IG _{1 to} IG _n has a positive power source as a second transistor Q2. A PNP transistor that operates in

Furthermore, the voltage-current conversion circuits VI _{1 to} VI
Each of the _n includes a PNP transistor operating with a positive power source as the first transistor Q1, and a constant current source IG ₁
Each of ˜IG _n includes an NPN transistor that operates with a negative power supply as the second transistor Q2.

[0021]

According to the ultrasonic diagnostic apparatus of the present invention having such a configuration, the DC bias current I _DC is used for determining the range of the distortion-free input voltage by the voltage-current converter for converting the received signal voltage into the current signal. This direct bias current I
_{As a DC} supply source, a constant current source IG provided in parallel with the load on the tap switching means 6 side flows in, so that only the current I _SIG corresponding to the input voltage V _SIG flows in from the load side, and a DC bias is generated. The restrictions on the output line and the buffer amplifier due to the current I _DC are lifted, the number of vibrators that can be switched and connected to one tap is significantly increased, and it is possible to appropriately cope with a large-diameter channel having many elements.

[0022]

FIG. 2 is a block diagram of an embodiment showing one embodiment of the present invention. In FIG. 2, the ultrasonic diagnostic apparatus of the present invention includes a control unit 1, a transmission driver group 2 including transmission drivers DR _{1 to} DR _n , and an ultrasonic transducer group including ultrasonic transducers TR _{1 to} TR _n. 3, preamplifier group 4 including preamplifiers PR _{1 to} PR _n , voltage / current converter group 5 including voltage / current converters VI _{1 to} VI _n and constant current sources IG _{1 to} IG _n , tap switching means , And a delay line 7.

The control means 1 sends a drive pulse to the transmission drivers DR _{1 to} DR _n of the transmission driver group 2 at a predetermined timing, and each transmission driver DR _{1 to} DR _n generates a high voltage pulse based on the input drive pulse. Then ultrasonic transducer TR ₁
It drives the corresponding transducer of the to Tr _n, irradiating ultrasonic beams into the object. The ultrasonic waves reflected at the tissue boundary surface (acoustic discontinuity point) in the subject are again ultrasonic transducers T.
It returns to R _{1 to} TR _n , is converted into an electric signal, is amplified by the preamplifiers PR _{1 to} PR _n of the preamplifier group 4, and is then supplied to the voltage-current converter group 5.

In the voltage-current converter group 5 of the present invention,
In addition to the voltage-current converters VI _{1 to} VI _n , constant current sources IG ₁ to
IG _n is newly provided. Voltage-current converters VI _{1 to} VI
_n is always flowing a constant DC bias current I _DC to determine the undistorted input range of the input voltage. The DC bias current I _DC voltage current flowing through the converter VI ₁ to VI _n is supplied from the constant current source IG ₁ ~IG _n newly provided, does not flow DC bias current I _DC to the tap changeover switches 6 side I am trying.

The tap changeover switch group 6 has a time delay as shown in FIG. 6 in which each of the received signals (current signals) obtained from the voltage-current converter group 5 corresponds to a predetermined focus position of the subject. In order to be received, the delay line 7 is selectively connected to a plurality of input taps. The current signal supplied to the delay line 7 is added at the input taps when a plurality of signal currents are selectively connected to the same input tap, and the current flowing through the delay line 7 is newly input when passing through the taps. The signal current is added and finally output as one scanning signal to display a tomographic image of the subject on the CRT monitor.

FIG. 3 is a circuit diagram of an embodiment in which one circuit of the voltage / current converter and the constant current circuit provided in the voltage / current converter group 5 of FIG. 2 is taken out and shown. In FIG. 3, first, the current-voltage converter is an NPN transistor Q1, which functions as a first transistor, capacitors C1 and C2, and resistors R1 and R.
2 and R3. That is, the signal voltage V _SIG of the received signal from the preamplifier located in the previous stage is set to the capacitor C1.
AC coupled to the base of the transistor Q1 via. The transistor Q1 is driven by the negative power source V _EE , biases the base with the divided voltage of the series circuit of the resistor R2, and supplies a constant DC bias current I _DC determined by the resistor R3 connected to the emitter.

That is, the resistors R1, R2 and R3 constitute a first direct current bias circuit for supplying a constant bias current I _DC to the transistor Q1. This DC bias current I _DC is V
It determines the undistorted input region of the input voltage V _SIG to the I converter, the so-called dynamic range. Further, an emitter resistance R _e is connected in parallel to the emitter of the transistor Q1 via a capacitor C2, and a signal current I _SIG corresponding to the input voltage V _SIG flows through the emitter resistance R _e . Therefore, (I _DC + I _SIG ) obtained by adding the DC bias current I _DC and the signal current I _SIG flows through the collector of the transistor Q1.

For the voltage / current converter VI, a constant current source G
I is provided. The constant current source GI has a second transistor
PNP transistor Q2 and resistors R4, R5 and
And a constant power source Vcc including R6. Resistor R4
R5 and R6 are voltage-current converters equipped with transistor Q1
First direct current composed of resistors R1, R2, R3 on the VI side
A symmetrical circuit is constructed with respect to the bias circuit, and R1 = R
4, R2 = R5, and R3 = R6, and the resistance R
By the second DC bias circuit by 4, R5, R6
Transistor Q2 has the same constant direct current as transistor Q1
Bias current I _DCIs flowing.

The collector of the transistor Q2 is connected to the collector of the transistor Q1, and the output line for the tap selection switch group 6 in the next stage is taken out between the two connections. As the operation of the embodiment of FIG. 3, the constant current source G is applied to the collector of the transistor Q1 of the voltage-current converter VI.
The collector of the transistor Q2 of I and the tap selection switch group 6 functioning as a load are connected in parallel, and the constant current source GI
Supplies a constant bias current I _DC to the voltage-current converter VI, so that only the signal current I _SIG converted from the input voltage V _SIG from the preamplifier by the transistor Q1 is output from the output line to the tap selection switch group 6. Therefore, the DC bias current I _DC does not flow in the output line to the tap selection switch group 6.

Therefore, in the tap changeover switch means 6 shown in FIG. 2, the signal current I _SIG corresponding to the ultrasonic transducers TR _{1 to} TR _n output from the voltage-current converter group 5 is outputted.
Only the switch is switched and connected to the tap of the delay line 7. Since there is no DC bias current added and supplied, the current capacity is limited only by the signal current, so it can be connected to one tap of the delay line 7. The limitation on the number of received signals from various ultrasonic transducers can be greatly relaxed.

For this reason, the 6
Even an ultrasonic diagnostic apparatus using a 4-element, 96-element, 128-element linear array can appropriately switch taps with respect to a delay line and can appropriately display a tomographic image by focus control. In the above embodiment, the first transistor Q1 of the voltage-current converter VI is
Although an NPN transistor is used as an example and a PNP transistor is used as the second transistor Q2 of the constant current source GI, conversely, the transistor Q1 is a PNP transistor and the transistor Q2 is an N transistor.
The same applies to a PN transistor.

[0032]

As described above, according to the present invention, since no DC bias current is output to the tap changeover switch group side, an existing inexpensive semiconductor switch IC is used as a selection switch for tap changeover. In addition, the buffer amplifier can be configured by using an existing inexpensive semiconductor IC, and a circuit configuration suitable for a large-diameter channel with a large number of elements can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

3 is a circuit diagram of an embodiment of the voltage-current converter of FIG.

FIG. 4 is an explanatory diagram of a conventional device.

FIG. 5 is an explanatory diagram of a focal position of an ultrasonic beam.

FIG. 6 is an explanatory diagram of a delay time given to each reception signal of the ultrasonic transducer.

FIG. 7 is a circuit diagram of a conventional voltage-current converter.

FIG. 8 is a signal waveform diagram of the voltage-current converter of FIG.

FIG. 9 is a circuit diagram of a tap switching group.

FIG. 10 is a circuit diagram of a delay line

[Explanation of symbols]

1: Control means 2: Transmission drive means (transmission driver group) 3: Ultrasonic transducer group 4: Reception amplification means (preamplifier group) 5: Voltage-current conversion means (voltage-current converter group) 6: Tap switching means (Tap changeover switch group) 7: Delay line DR _{1 to} DR _n : Transmission driver TR _{1 to} TR _n : Ultrasonic transducer PR _{1 to} PR _n : Preamplifier VI _{1 to} VI _n : Voltage current converter IG ₁ to IG _n : constant current source Q1: first transistor (NPN transistor) Q2: second transistor (PNP transistor)

Claims (4)

[Claims] 1. A plurality of adjacent ultrasonic transducers (TR _{1 to} T).
R _n) by applying a high voltage pulse driven, the transmission driving means for irradiating an ultrasonic beam into the subject (2), ultrasonic vibrations reflected wave of the ultrasonic beam from each tissue inside the subject Reception amplification means (4) for amplifying a reception signal received by the child (TR _{1 to} TR _n ) and converted again into an electric signal, and a voltage for converting the reception signal voltage from the reception amplification means (4) into a current signal. A current converting means (5), a delay line (7) having a plurality of taps, and the transducers (TR _{1 to} TR) so that the ultrasonic beam is focused on a specific portion inside the subject.
_n ), each tap of the delay line (6) is selectively connected to each of the received signals current-converted by the voltage-current converter (5) to give a predetermined delay, and the respective sums are added. And a tap switching means (6) for obtaining a target signal on the scanning line according to the above, and in the ultrasonic diagnostic apparatus for displaying the scanning signal from the delay line (7), the voltage-current conversion means (5) is For each received signal, a DC bias current (I
A voltage-current converter (VI ₁ ) which converts an input voltage signal (V _SIG ) into a current signal (I _SIG ) and outputs the converted current signal (V _SIG ) in a state where _DC is applied.
And to VI _n), the bias current (I _DC) constant current source for supplying to said voltage current converter _{(VI 1 ~VI n) (IG} 1
˜IG _n ) and the voltage-current converter (VI _{1 to} V
An ultrasonic diagnostic apparatus characterized in that a bias current (I _DC ) flowing through I _n ) is prevented from being output to the tap switching means (6) side. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the voltage-current converter (VI).₁ ~ VI_n ) Each is input
Voltage (V_SIG ) Is converted into a current signal and output.
A transistor (Q1) and the first transistor (Q1)
Input voltage (V_SIG ) AC connection
(C1) and the collector of the first transistor.
A constant DC bias current (I _DC) Flow first
DC bias circuit (R1, R2, R3) of the
In the collector and emitter of the transistor (Q1) of
Power voltage (V_SIG Signal current (I_SIG )
Current bias circuit (C2, Re), the constant current source (IG₁ ~ IG_n ) Each of the first
A constant current (I_SIG )
And a second transistor (Q2) for pouring
Configured symmetrically with the DC bias circuit (R1, R2, R3)
The second DC bias circuit (R4, R5, R6)
An ultrasonic diagnostic apparatus characterized by being provided. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein
Each of the voltage-current conversion circuits (VI _{1 to} VI _n ) includes an NPN transistor operating with a negative power source as the first transistor (Q1), and the constant current sources (IG _{1 to} I).
The ultrasonic diagnostic apparatus is characterized in that each of G _n ) is provided with a PNP transistor operated by a positive power source as the second transistor (Q2). 4. The ultrasonic diagnostic apparatus according to claim 1, wherein:
Each of the voltage-current conversion circuits (VI _{1 to} VI _n ) includes a PNP transistor operated by a positive power source as the first transistor (Q1), and the constant current sources (IG _{1 to} I).
Each of G _n ) is provided with an NPN transistor that operates with a negative power source as the second transistor (Q2).