JPS58112533A - Reflected wave receiving system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a reflected wave receiving system suitable for a medical ultrasound device. In particular, the present invention relates to improvements for improving the signal-to-noise ratio and resolution of reflected waves reflected inside an object.

[Description of prior art]

For example, a probe containing an electric sonic conversion element is brought into contact with the surface of a living body, and a short ultrasonic pulse is transmitted by this probe, and the reflected wave generated when this is reflected inside the living body is received by this probe. , a method is known in which the electrical signal is converted into an electrical signal and the electrical signal is visually displayed according to the passage of time from the transmission time of the ultrasonic pulse.

With this method, for example, tomographic images inside the body can be displayed visually, and are used for diagnosis and treatment.

As time elapses from the transmission time of the ultrasonic pulse as a starting point, the reflection point of the received reflected wave becomes deeper in the subject. When the reflection point is shallow, focusing on the high frequency component of the reflected wave will result in a high signal-to-noise ratio and resolution; when the reflection point is deep, focusing on the low frequency component of the KFi reflection technique will result in a high signal-to-noise ratio and resolution. It has been known. Japanese Patent Application Laid-Open No. 52-59975 utilizes this phenomenon, and includes a voltage-variable dynamic filter in the receiving device, and changes the passband of this filter starting from the transmission time of the ultrasonic pulse to detect the reflection point. A method for obtaining uniform resolution from shallow to deep areas is shown.

Although this method is an excellent method, it requires a circuit that includes a dynamic filter in the receiving device and controls many variable parameter elements all at once, making it difficult to obtain high stability with such a device. , the manufacture and maintenance of this device requires complex coordination.

[Object of the present invention]

The present invention eliminates the need for a dynamic filter with a large number of variable parameter elements and their control circuits, has a simple device configuration, has uniform resolution even with respect to the depth of the reflection point, and can obtain reflections with a high signal-to-noise ratio. The purpose is to provide a wave reception method.

[Key points of the invention]

The present invention provides oscillation means whose output frequency changes continuously over time starting from the transmission time of an ultrasonic pulse, means for multiplying the output of this oscillation means by an electrical signal of a received reflected wave, and this means. and low-frequency door wave means for passing the output signal of.

[Station distance according to example]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. The electroacoustic transducer T of the probe is brought into contact with the surface of the subject, transmits ultrasonic pulses into the subject, and receives the reflected waves. The electrical terminal is connected to the balsa P via a coupling circuit H.
The output of L8 is connected, and the receiving amplifier A10 is also connected via this coupling circuit Ht. Pulsar PL8 is synchronized with clock signal OLK.

The output of amplifier M1 is sent to level control circuit '1. It is applied to the second amplifier 2 via W'l. A sawtooth wave generation circuit WGN synchronized with the clock signal OLE is provided, and the output of the sawtooth wave generation circuit WGN controls the level control circuit LIT and the voltage controlled oscillator VCO. voltage controlled oscillator vCOFi,
This is a circuit that generates a frequency that is four times the repetition frequency of the transmitted ultrasonic pulse, and its output is added to a frequency divider V and divided by four to obtain two outputs whose phases differ by 90 degrees from each other.

The output of the second amplifier M2 is divided and guided to multipliers M1 and M2, respectively. The two outputs of the frequency divider DIV are supplied to the multipliers M1 and M2, and the multiplier outputs thereof are respectively the low-frequency F frequency filter LP? , and LPF
z and is applied to two inputs of a combining amplifier S. This composite amplifier As outputs a signal proportional to the sum Ial + lbl of the respective absolute values of the two inputs aS b. This output is input and displayed on a known visual display device DPL.

To explain the operation of the device configured in this way, the conversion element T receives an ultrasonic reflected wave, and the signal converted into an electric signal is amplified to a predetermined level by the amplifiers A1 and M2. Generally, when the reflection point depth of the ultrasonic reflected wave is shallow, the level of the reflected wave is high, and as it becomes deeper, the level becomes lower.
The level control circuit LIV controls the signal reflected from a deep reflection point to be amplified with a high gain depending on its depth.
I do.

In addition, the output of the voltage controlled oscillator VCO is controlled so that the frequency is high when the reflection point of the reflected wave is shallow and becomes low as the reflection point becomes deeper, so the output of each multiplier M1 and M2 is The electrical signal becomes a signal modulated by this frequency.

This is a fixed passband low-pass P-wave filter LPF, or L
It passes through PF2 and is subjected to so-called synchronous detection.

Figure 2 is a diagram explaining this situation.If the horizontal axis is the frequency and the vertical axis is the output level, the frequency spectrum of the received ultrasonic reflected wave is shown by the broken line, from #view fL to r
It is assumed that the distribution is up to H.

Assuming that the passband of the low-pass wave detector is from approximately zero frequency to fy t, when the output frequency of the voltage controlled oscillator VaO is high, that is, immediately after the transmitting ultrasonic pulse is transmitted, as shown in Fig. 2 (a). As shown, the band width f at the center frequency f,
y signal is being received. With the passage of time, this center frequency f gradually moves to the left as shown by the arrow in the figure, and at the time when the reflected wave from a deep reflection point is received, it becomes as shown in FIG. 2 (1,).

In the apparatus of this embodiment, these are each synchronously detected using local oscillation signals having a phase difference of 90 degrees, and the signals are combined by a combining amplifier S. As for the characteristics of the composite amplifier M, it is desirable to obtain a signal proportional to M2 + b2 for the two inputs a% b at its output, but as mentioned above, it is preferable to construct it with a simple circuit that obtains lal + lbl as a substitute. is practical.

[Explanation of effects]

As described above, according to the present invention, starting from the time when an ultrasonic pulse is transmitted, the receiving band at which the reflected waves are focused changes substantially as time passes, so that the reflected waves are reflected Depending on the depth of the point, it is possible to receive the signal with high resolution and a high signal-to-tone ratio. The circuit of the invention does not use so-called dynamic filters to achieve this.

The P-wave device of the present invention has a fixed passband, and there is no need to perform complicated change control during the time when reflected waves are being received. In the circuit of the present invention, this is achieved by applying a sawtooth wave to the control input of the voltage controlled oscillator, so its operation is stable and the circuit configuration is simple. Also, the manufacture and maintenance of this circuit does not require complicated adjustment fees.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. FIG. 2 is a frequency characteristic diagram for explaining operation. PLEI... Pulsar that generates ultrasonic pulses, T.
...Electroacoustic transducer, M1, M2...Amplifier, LII
iV: Level control circuit, DPL: Visual display device, WGN: Sawtooth wave generation circuit, VCO: Voltage controlled oscillator, DIV: Branch unit, Ml, M2: Multiplier, LPF, LPF2...Low p-wave device, MuS...
・Synthetic amplifier. Patent applicant: Yokogawa Electric Corporation - Agent: Patent attorney Nao Takashi Ide

Claims (2)

[Claims] (1) A means for converting the ultrasonic reflected wave generated within the subject by an ultrasound pulse transmitted into the subject into an electrical signal, a means for detecting and amplifying this electrical signal, and an output of this means. In the reflected wave receiving method, the reflected wave receiving method includes a means for visually displaying a time corresponding to the time elapsed from the time when the ultrasonic pulse was transmitted, and the means for detecting and amplifying the detected wave has a starting point at the time when the ultrasonic pulse was transmitted. oscillation means whose output frequency changes continuously as time passes; means for amplifying the electric signal obtained from the converting means and multiplying the good signal by the output signal of the oscillation means; A reflected wave receiving system comprising: low-frequency p-wave means for passing an output signal. (2) The oscillation means is configured to send out two outputs having a phase difference of 90 degrees from each other, two multiplying means are provided corresponding to these two outputs, and the low-frequency P wave means Two reflected waves are provided corresponding to the outputs of the multiplication means, and the reflected waves according to claim (1) are configured to combine the outputs of the two low MP wave means to form an output signal. Reception method.