JPS633618B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in ultrasonic diagnostic equipment.

Conventionally, in ultrasonic diagnostic equipment that obtains tomographic images of a subject using the ultrasonic pulse echo method, a large level of reflected signal from a shallow part of the subject (signal attenuation is determined by the distance between the probe and the target part). (corresponding to ), and the small level reflected signal from the deep part is controlled by adjusting the gain in the variable gain amplifier in the middle stage of the circuit so that it becomes a signal of approximately constant magnitude. However, in order to prevent the signal from being saturated, the amplifier in the previous stage before the variable gain amplifier had a restriction that the dynamic range had to be extremely wide.

In view of these points, it is an object of the present invention to provide an ultrasonic diagnostic apparatus that has a relatively simple configuration and can maintain an almost constant level of echo signals at the stage of inputting them to the first-stage amplifier.

The present invention will be explained in detail below using the drawings. FIG. 1 is a diagram showing the configuration of essential parts of an embodiment of an ultrasonic diagnostic apparatus according to the present invention. In the figure, TR is a probe that transmits and receives ultrasonic waves, and the obtained echo signal is guided to the first stage amplifier AMP via a series circuit consisting of a capacitor _C1 and a resistor _R1 . A clamp diode D ₁ ′D ₂ connected in antiparallel is connected between the input terminal of the amplifier AMP and the common line. Also, connect a series circuit of inductance L and capacitor _C2 in parallel with this diode,
It is designed to cut off low frequency components in the echo signal. 10 is means for generating a voltage that changes from negative potential to zero potential. In this means 10, Q ₁ to Q ₅ are transistors,
PNP type transistor Q ₁ is connected to + via resistor R ₂ ′R ₃
They are pulled up to 5V and -5V, respectively, and a trigger signal TRIG that determines the probe drive timing is applied to the pace. The collector of Q ₁ is connected to the base of the next stage transistor Q ₂ ,
The potential is -5V when TRIG is "1" and OV when TRIG is "0". The emitter of Q ₂ is connected to -5V potential, while the collector of Q ₂ is connected to the common line via a variable resistor VR ₁ . The divided voltage of variable resistor VR ₁ is led to the base of transistor Q ₃ in the next stage. The collector of Q ₃ is connected to -5V potential, and the emitter is connected to the next stage transistor Q ₄ .
connected to the base of. Furthermore, the emitter of _Q4 is commonly connected to the collector of _Q5 , and is connected to +5V potential via a resistor _R4 . The collector of _Q4 is connected to the base of _Q5 , and the emitter of _Q5 is connected to -5V potential. In addition, a parallel circuit of capacitor C and variable resistor VR ₂ is connected to the base of Q ₄ , and when Q ₃ changes from ON to OFF,
It is configured to start charging C ₃ and increase the base potential of Q ₄ exponentially from -5V. and
The collector of _Q5 is connected via a resistor _R5 to the common connection point of the inductance L and the capacitor _C2 .

In such a configuration, a trigger signal as shown in Fig. 2 A is sent from a controller (not shown).
When TRIG is given, Q ₁ is ON, Q ₂ is ON, therefore Q ₃ is ON, and the base of Q ₄ is -5V when VR ₁
The partial pressure is reduced by . This gives Q ₄ ′Q ₅
is turned on, and the collector of _Q5 becomes as shown in Figure 2 (c). Then the trigger signal changes from “L” to “H”
, Q ₁ ′Q ₂ ′Q ₃ are both turned off, and the base current of Q ₄ flows to capacitor C ₃ and resistor VR ₂ .
At this time, the terminal voltage of capacitor _C3 increases exponentially, and accordingly, the collector potential of _Q5 also increases to the second level.
As shown in C of the figure, it increases exponentially. On the other hand, the probe TR is excited by a drive pulse generated when TRIG reverses to "H" as shown in FIG. 2B (the probe drive circuit is not shown). An echo signal is received by the probe TR at time t after excitation, and after the DC component is cut off by _C1 , it is guided to a series load of a resistor _R1 and a diode _D1 . Diode D ₁ is a voltage clamp (the normal level echo signal is a minute level and will not be clamped by diode D ₁ )
It also acts as a voltage dividing resistor. Therefore, a voltage (negative voltage) divided by the resistor _R1 and the resistor of the diode _D1 is input to the amplifier AMP. And in this case, at the same time as the arrival of the echo signal, the resistor R ₅ is removed from the collector of the transistor Q ₅
Current begins to flow into the diode _D1 via the inductance L (the direct current resistance is small). As described above, this current gradually approaches zero as time passes, and therefore the resistance of the diode changes from a small value to a large value as time passes.

Therefore, an echo signal with a large level (but a negative voltage signal) at the initial point of echo arrival will cause a diode exhibiting a small resistance value at that time.
The echo signal, which is divided by D ₁ to a moderately low signal level and input to the amplifier AMP, and whose level then decreases as time elapses, is generated by the resistance value increasing as time elapses, as described above. Diode _D1 divides the voltage to the same level as the moderately small level mentioned above, and the amplifier AMP
is input.

Therefore, by appropriately adjusting the collector voltage of the transistor _Q5 using the capacitor _C3 and the resistor _VR2 , a substantially constant echo signal is always input to the amplifier AMP. In this way,
Echo signals from shallow and deep parts of the object can be input to the amplifier AMP at approximately the same level, and as a result, this amplifier AMP and subsequent amplifiers do not require a wide dynamic range at all.

Note that the diode _D2 is added to prevent excessive input in the reverse direction to the AMP. On the other hand, the means 10 may have other configurations, and the change in collector voltage may not be an exponential change as in the embodiment.

As explained above, according to the present invention, a voltage that gradually increases from a negative potential over time is applied to the diode, and the resistance of this diode is used to divide the echo signal, so that the echo signal has different magnitudes in relation to the arrival time. It is possible to realize an ultrasonic diagnostic device that can correct the echo signal to a nearly constant magnitude and input it to the first stage amplifier, and there is no need for each amplifier used to have a large dynamic range, making it suitable for practical use. The effect is great.

[Brief explanation of the drawing]

FIG. 1 is a main part configuration diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 2 is an operational waveform diagram. TR……Probe, C ₁ ′C ₂ ′C ₃ ……Capacitor, R ₁
~R ₅ ……Resistance, VR ₁ ′VR ₂ ……Variable resistor,
D ₁ ′D2... Clamp diode, AMP... Amplifier, Q ₁ ~ _{Q 5} ... Transistor.

Claims (1)

[Claims] 1. In an ultrasonic diagnostic apparatus that obtains a tomographic image of a subject by receiving echo signals from the subject using the ultrasonic pulse echo method, in relation to the elapsed time after exciting the probe. means for generating a voltage that changes from negative potential to zero potential; a fixed resistor to which an echo signal from the probe is applied at one end; and a fixed resistor connected in series to the fixed resistor with the other end connected to a common line. means for voltage-dividing the input echo signal by applying a current to the clamp diode in accordance with the output of the voltage generating means to cause the clamp diode to act as a resistive element; and a voltage generated in the clamp diode. and a first-stage amplifier that receives an echo signal from the terminal contact whose level decreases with elapsed time by the voltage dividing means to supply an echo signal of a substantially constant level to the amplifier. An ultrasonic diagnostic device characterized by: