JPS61193648A - Doppler apparatus - 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 (Field of Industrial Application) The present invention relates to a medical ultrasound CW Doppler device or a pulse alignment device. This invention relates to a Doppler device that prevents harmful signals from being sent to an analysis system or other parts of the system.

(Prior technology) Conventionally, there has been a method of installing a noise blanker in a Doppler device, and when an unnecessary loud rattling sound is generated depending on the level of the Doppler signal, the signal is cut so that it is not sent to the speaker section. .

This technique is commonly used in CW Doppler fetal detectors, etc., and is used to prevent loud noises from the speaker that occur when applying jelly to the probe or touching it to the body surface. has been done.

(Problem to be Solved by the Invention) However, such techniques do not pay attention to the level of the RF echo signal before Dora detection, so when there is a strong echo (usually called clutter) that does not have a Doppler shift, There is a problem in that saturation and non-linear phenomena occur within the receiving system, and the system is powerless against modulation noise that is introduced onto the signal transmission path due to saturation and non-linear phenomena.

Such a phenomenon can occur not only in CW Doppler but also in pulsed Doppler when there is a strong echo source directly under the skin, but it is particularly disadvantageous in the pulsed Doppler method in which the signal energy appears concentrated on the time axis.

The present invention has been made in view of the above-mentioned problems, and its purpose is to eliminate artifacts derived from clutter by operating a noise blanker even when there is an RF echo signal that exceeds the acceptance limit of the receiving input as described above. An object of the present invention is to provide a Doppler apparatus that can prevent this from occurring in images.

(Means for Solving Problem 1!11) The present invention which solves the above problems includes level detection means for detecting input of a large echo signal that exceeds the normal operating level range of the receiving device, and The apparatus is characterized by comprising means coupled to the detection means for blocking the Doppler signal output when the received echo signal exceeds a normal operating level range.

(Example) Examples of the present invention will be described in detail below using the drawings. FIG. 1 is a block diagram of main parts showing an embodiment of a Doppler apparatus according to the present invention. This figure is a block diagram of the apparatus in the case of the pulse alignment method, and 1 is a probe that transmits and receives ultrasonic waves. The probe 1 generates ultrasonic waves when driven by pulses output from the balsa 2, and when it receives an echo, converts it into an electrical signal. The obtained electrical signal (echo signal) is sent to the preamplifier 5. The balsa 2 is energized by a signal obtained by dividing the frequency signal generated by the local oscillator 4 by 1/2'' by the divider 3, and generates a pulse for driving the probe.

The echo signal that has passed through the preamplifier 5 is input to the first amplifier 8 via an attenuator 6. 7 is time/gain/
A controller (TGC) controls the attenuation rate of the attenuator 6 as a function of time. TGC 7 is synchronized with balsa 2 and compensates for the fact that the strength of the received echo signal is attenuated according to the distance from the probe to the signal source (that is, the amount of attenuation increases in response to FRIll). , the attenuation rate of the attenuator 6 decreases in relation to time.

The output of the first amplifier 8 is sent to a coherent detector 9.10 and detected. The coherent detector 9 refers to the output signal of the local oscillator 4, and the other coherent detector 10
refers to the output of the local oscillator 4 with a 90° phase shift via a 90” phase shifter 11. Each coherent detector 9, 1
The outputs t and a of 0 are each led to a range gate 14.15 via an amplifier 12.13. range gate 14,
15 is a switch, and a range gate controller 16
This controls the timing and duration of the on state. The range gate controller 16 is capable of adjusting its timing (corresponding to the depth to be observed) and time width (corresponding to the depth width) in synchronization with the balsa 2. Each echo signal taken in through the range gate is passed through a Doppler filter 17, 18 to extract only signals in a predetermined band, and sent to an analysis system (including speakers, etc.), not shown, via a switch 19, 20. This switch 19.20
is controlled by a threshold circuit 21, which will be described later, so that it is turned off when unnecessary noise arrives.

22 is a level monitor circuit, which outputs the output of the amplifier 8, or the outputs of the amplifiers 12 and 13, or the amplifier 8.12.13.
Receive all outputs and detect their output signal levels.

The threshold circuit 21 turns off the switches 19 and 20 when the output signal level is above a certain threshold level (when it is above the permissible limit).

In addition, at that time, the warning lamp 23 is turned on to notify the operator of this fact.

According to such a configuration, received signals outside the specified depth range are cut off, and even if the echo signals are from within the specified depth range, modulation noise caused by echo signals exceeding a certain level can be cut off. can also be cut off. Therefore, it is possible to prevent artifacts caused by noise from occurring in the image.

FIG. 2 shows the case of the CW Doppler method. The probe 31 is 2
One transducer 31a is driven by the carrier signal from the carrier generator 32 to generate ultrasonic waves, and the other transducer 31b receives the echo and converts it into an electrical signal! 11.

This electrical signal is passed through an RF' amplifier 33 to a detector 34.
Detect the wave with The detection output passes through the Doppler filter 35 and is AF
After being amplified by an amplifier 36, it is sent to an analysis system and a first level monitor circuit 37. At the same time, the detected output is divided into voltages appropriately by a voltage divider 38 and then passed through a speaker amplifier 39 to a speaker 40.
given to. The speaker 40 allows the Doppler signal to be heard as sound.

41 is one of the circuits featuring the present invention, and the RF amplifier 3
This is a second level monitor circuit that detects the output level of No. 3. This output is input to the OR gate 42 together with the output of the first level monitor circuit 37. The output of the OR gate 42 is given to a noise blanker 43. noise blanker 4
3 is a speaker amplifier 39 according to the output of the OR gate 42.
control the gain of. In such a configuration, the RF amplifier 33 or AF amplification! When at least one output signal of 1It36 is above a predetermined level, OR gate 4
2 becomes active, the noise blanker 43 operates, and the gain of the speaker amplifier 39 is lowered to reduce the gain of the speaker 40.
Stop outputting.

(Effects of the Invention) As explained above, according to the present invention, when the echo signal from the target area exceeds the allowable limit, the noise blanker is activated to cut off the signal, and the analysis system and speaker are automatically It is possible to realize a Doppler device that can prevent the damage from occurring.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the pulsed Doppler system according to the present invention, and FIG. 2 is a block diagram of an embodiment of the CW Doppler system. 1.31... Probe 2... Balsa 3... Frequency divider 4... Local oscillator 5.8.12.1
3.33.36.39...Amplifier 6...Attenuator 7...TGC9,10.
... Coherent detector 11 ... Phase shifter

Claims (1)

[Claims] Level detection means for detecting input of a large echo signal exceeding the normal operating level range of the receiving device; and a Doppler signal coupled to the level detecting means and output when the received echo signal exceeds the normal operating level range. A Doppler device characterized by comprising means for preventing.