JPH0679608B2 - Ultrasonic diagnostic equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus that scans by an electronic scanning method using a transducer array having a plurality of transducer elements.

(Prior Art) An ultrasonic diagnostic apparatus is an apparatus that irradiates an ultrasonic signal into a subject and forms a tomographic image by a reflected wave from a reflector inside the subject to perform diagnosis. In this ultrasonic diagnostic apparatus, an ultrasonic beam is swung to obtain a tomographic image, and a tomographic image of a plane crossed by the ultrasonic beam is obtained. As a method of oscillating the ultrasonic beam, there are a method of performing manually, a method of mechanically moving, etc., but an electronic scanning ultrasonic diagnostic apparatus using a transducer array having a large number of transducer elements is used in real time. Moreover, since an image can be obtained at high speed, it is often used recently.

An outline of the electronic scanning type ultrasonic diagnostic apparatus is shown in FIG.
In the figure, reference numeral 1 is a high-frequency oscillator that receives a transmission trigger and generates a high-frequency signal for ultrasonic transmission. The output signal is subjected to delay processing so as to form a beam in a transmission beamformer 2, and a transmission / reception circuit 3 Is input to the ultrasonic probe 4. The ultrasonic probe 4 converts an input electric signal into an ultrasonic signal and transmits the ultrasonic wave into the subject, receives a reflected wave from the inside of the subject, and converts it into a high frequency electric signal. The output signal of the ultrasonic probe 4 is amplified by the transmission / reception circuit 3, subjected to delay processing by the receiving beam former 5 and subjected to phasing addition.
This output signal is detected by the detector 6, converted into a television format signal by a digital scan converter (hereinafter referred to as DSC) 7, and displayed on the TV monitor 8. The tomographic image obtained by this ultrasonic diagnostic apparatus is a tomographic image that is sliced in the direction of the ultrasonic signal, that is, in the depth direction, so that the image is clear at the place where the ultrasonic beam is focused, It lacked clarity at depths that were out of focus. This focus position is the receiving beamformer 5.
In, the delay amount is given to each element of the vibrator.

As described above, when the focus position is fixed with respect to the depth, a clear image cannot be obtained. Therefore, the focus position is temporally changed by the dynamic focus method to improve the resolution. However, in the above-mentioned dynamic focus, the depth of the focal point is not continuous, for example, a depth of 2 cm,
Since it is scattered like 4 cm and 6 cm, it is not possible to obtain an image with good image quality. Therefore, a method called continuous dynamic focus is used in which the focal position is continuously changed by using a variable length delay line.

(Problems to be Solved by the Invention) FIG. 3 shows a conventional continuous dynamic focus circuit. This circuit is a part of the circuit of the receiving beamformer 5 in FIG. 2, and one circuit is attached to each transducer element, but since all operate in the same manner, only one circuit will be described below. To do. In the figure, 11 is a variable-length delay line that changes the LC type L or C continuously to equivalently change the delay time τ, and 12 is the impedance of the input circuit and the characteristic impedance Z _O of the delay line 11. Matching resistor for impedance matching, 13 is the characteristic impedance of delay line 11
It is a matching resistor that terminates with an impedance equal to Z _O. The time length τ of the delay line 11 is controlled and changed by the delay line control circuit 14. Further, the matching resistances 12 and 13 can be changed in resistance value R by the matching resistance control circuit 15. By the way, in the continuous dynamic focus, the delay time τ of the delay line 11
Is changed by an external control signal. Specifically, L or C is continuously changed by the output signal of the delay line control circuit 14 which receives the external control signal to change the focal position of the ultrasonic beam. Be moved. At this time, the characteristic impedance Zo
Also changes at the same time, so the matching resistance 12 before and after
13 must also be controlled by the matching resistance control circuit 15 so that R = Zo. Conventionally, the delay time τ and the matching resistance (impedance) R are controlled by the delay line control circuit 14 and the matching resistance control circuit 15 which receive external control signals, respectively.
It was done by and completely independently. For this reason, two independent control loops are required: a control loop for receiving the external control signal to control the delay time τ and a control loop for receiving the external control signal to control the impedance R. Therefore, hardware and There was a problem that the firmware increased.

The present invention has been made in view of the above points, and an object thereof is to realize an ultrasonic diagnostic apparatus that can favorably control delay time and impedance with a simple configuration.

(Means for Solving the Problems) The present invention for solving the above problems is an ultrasonic diagnostic apparatus for scanning by an electronic scanning method using a transducer array having a plurality of transducer elements, wherein the vibration LC ladder type delay line with variable delay time for phasing addition of received signals at child elements, impedance matching means provided at the input side and termination of the delay line, and circuit of delay time forming element constituting the delay line An ultrasonic diagnostic system including delay time control means for generating a bias voltage for changing a constant and impedance control means for outputting a signal for changing the impedance of impedance matching means provided at the input side and the termination of the delay line. In the device, as the impedance control means, a signal obtained by linearizing the output voltage of the delay time control means is used as the impedance matching means. It is characterized by using a linearizer that outputs to stages.

(Operation) The impedance of the impedance matching means at the input side and the termination of the delay line is changed by a signal obtained by linearizing the delay time controlling output voltage of the delay time controlling means to match the impedance with the delay line. .

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing one element of a receiving beam former in one embodiment of the present invention. In the figure, reference numeral 21 is a variable-length delay line in which the delay time τ is changed by connecting a wire ring and a capacitor in a ladder shape and changing the capacitance of the capacitor. The capacitance of the capacitor changes depending on the bias voltage. A variable capacitance diode is used. Reference numeral 22 denotes an impedance matching circuit (hereinafter simply referred to as matching circuit) in which four diodes provided on the input side of the delay line 21 are connected in a ring shape, and the dynamic resistance value thereof changes according to a bias current. Match the characteristic impedance Z _{O of} line 21. 23 is a delay line
21 is connected to the output side and the delay line 21 has a characteristic impedance
It is a matching circuit that terminates at Z _O. Reference numeral 24 is a delay time control signal generating circuit that outputs a bias voltage V _T (t) that changes with time in order to change the delay time of the delay line 21, and 25 is composed of an operational amplifier, a diode, and a resistor. This is a linearizer that outputs the voltage V _R by approximating the function of equation (1) with respect to V _T with a broken line.

V _R = f (V _T ) ... (1) 26 has the emitter connected to the DC voltage V _CC through a resistor,
PNP transistor collector ground that V _R (t) is a base time varying voltage, 27 are input time-varying emitter voltage by the base voltage V _R of the PNP transistor 26 (t) to a base, an emitter resistor Inversely proportional to R _I , V
_An NPN transistor that allows a collector current i = V _R (t) / R _I proportional to _R (t) to flow through the matching circuit 22 connected to the collector, and 28 operates the NPN transistor 27 in the same manner, and the matching circuit 2
It is an NPN transistor that passes the same collector current through 3.

Next, the operation of the embodiment configured as described above will be described.
First, the principle of operation will be described. When the inductance per stage of the LC circuit of the delay line 21 is L _O and the capacitance is C _O , the total delay amount τ of the delay line 21 of length n stages is Further, the characteristic impedance Z _O of this delay line 21 is, if the resistance and leakage conductance in the circuit are ignored, In the above equation, the delay time τ can be changed by changing either L _O or C _O , but the characteristic impedance Z _O also changes at the same time.

The total inductance of the delay line 21 consisting of LC circuit in n stages L, if the total capacitance and C, L = nL _O, a C = nC _O.
Substituting this into equations (2) and (3), From equation (3) Therefore, from the expressions (4) and (5), Z _O = L / τ (6) Therefore, when the delay time τ of the delay line 21 is changed, the characteristic impedance Z _O changes according to the expression (6). Here, the resistance value R of the matching circuits 22 and 23 may be changed according to the following equation.

_{R = Z O = L / τ} ... (7) resistance R NPN transistor of the formula through the matching circuits 22 and 23
It is controlled by the collector current of 27,28.

i = V _R (t) / R _I = f {V _T (t)} / R _I (8) where the output voltage V _R (t) of the linearizer 25 is the output voltage V of the delay time control signal generation circuit 24. It is a function showing the following expression of _T (t).

V _R (t) = f {V _T (t)} Therefore, by appropriately selecting R _I , the resistance value R of the matching circuits 22 and 23 can be always matched with the characteristic impedance Z _O of the delay line 21.

The operation of the receiving circuit of the ultrasonic diagnostic apparatus including the delay circuit of the receiving beam former of the embodiment that operates according to the above principle will be described with reference to FIG. The reception signal received by the ultrasonic probe 4 and converted into an electric signal and input to the reception beamformer 5 through the transmission / reception circuit 3 is matched by the matching circuit 22 with the characteristic impedance Z _O of the delay line 21, Delay line 21
Entered in. Output voltage of delay time control signal generator 24
The capacitance of the variable capacitance diode to V _T the bias voltage (t) is varied by changing the V _T (t), the delay time of the delay line 21 is set to a predetermined delay time tau. The linearizer 25 is a delay time control signal generation circuit 24
Output V _R (t) that is a function of the output voltage V _T (t) of
Via P-transistor 26 to NPN transistors 27 and 28 (8)
The expression current is passed. The matching circuits 22 and 23 perform impedance matching by setting the resistance value R equal to the characteristic impedance Z _O of the delay line 21 shown in equation (7) by the current of equation (8) flowing through the diodes forming the circuits. ing.

The received signal that has been delayed by the delay line 21 through the matching circuit 22 having the resistance value R equal to the characteristic impedance Z _O is
It is terminated by the matching circuit 23 and input to the detector 6 in a substantially distortion-free state for detection. The detected output signal is converted into a television format signal by the DSC 7 and displayed on the TV monitor 8.

As described above, according to this embodiment, when the delay time τ is controlled, the linearizer automatically adjusts the impedance of the input circuit and the termination impedance to be equal to the changed characteristic impedance of the delay line. In this configuration, as the control for receiving the control signal from the outside, only the delay time τ may be controlled, and the impedance control is not directly required. Then, impedance control can be achieved by inputting a control signal with a delay time τ to the linearizer and giving an output signal of the linearizer to the matching circuit.
Therefore, the configuration of software and firmware required for control can be greatly simplified. Here, the relationship between the delay time τ and the characteristic impedance Z _O will be described. These correspond one to one. Therefore, even if a linearizer using a voltage for controlling τ as an input signal is used, R, which is the impedance of the matching circuit, can be easily and accurately tracked to Z _O.

The present invention is not limited to the above embodiment. For example, the delay line 21 changes the capacitance C, but may change the inductance L. Further, although a variable capacitance diode is used as the variable capacitance and a matching circuit is constituted by a diode is used, any element may be used as long as the same effect can be obtained. Further, the linearizer 25 is not limited to the example.

(Effects of the Invention) As described in detail above, according to the present invention, in order to control continuous delay time change for dynamic focus by a command from the outside, it is assumed to be controlled by software or firmware. Controls only the delay time, while the matching impedance is controlled by the output of the linearizer that uses the delay time control voltage as the input signal, regardless of the direct command from the outside. Even though both the control of 1 and the control of the delay time are performed, the configuration of software and firmware for performing the control according to the continuous change of the focus position is simplified. Further, since the delay time and the impedance of the delay line have a one-to-one correspondence, the matching means can be satisfactorily controlled even if a linearizer using a voltage for controlling the delay time as an input signal is used. The above effect is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing one element of a receiving beamformer according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an ultrasonic diagnostic apparatus, and FIG. 3 is one element of a conventional receiving beamformer. It is a block diagram. 1 ... High frequency oscillator, 2 ... Transmission beamformer 3 ... Transceiver circuit, 4 ... Ultrasonic probe 5 ... Receiving beamformer 6 ... Detector, 7 ... DSC 8 ... TV monitor, 11,21 …… Delay line 12,13 …… Matching resistor 14 …… Delay line control circuit 15 …… Matching resistance control circuit 22,23 …… Matching circuit 24 …… Delay time control signal generating circuit 25 …… Linearizer 26… … PNP transistor 27,28 …… NPN transistor

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Claims (1)

[Claims] 1. An ultrasonic diagnostic apparatus for scanning by an electronic scanning method using a transducer array having a plurality of transducer elements, wherein a delay time variable LC for phasing and adding received signals at the transducer elements. A ladder-type delay line, impedance matching means provided at the input side and termination of the delay line, and delay time control means for generating a bias voltage for changing the circuit constant of the delay time forming element forming the delay line, In an ultrasonic diagnostic apparatus comprising an impedance control means for outputting a signal for changing the impedance of the impedance matching means provided at the input side and the termination of the delay line, the output of the delay time control means as the impedance control means A linearizer for outputting a signal obtained by linearizing a voltage to the impedance matching means is used. Wave diagnostic apparatus.