JPH0693891B2 - Ultrasonic blood flow imaging device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an ultrasonic blood flow imaging apparatus.

[Technical Background of the Invention] An ultrasonic blood flow imaging device is basically a technique that is an extension of the ultrasonic blood flow Doppler device. The blood flow Doppler device uses the fact that the ultrasonic echo undergoes a frequency shift due to the blood flow, and only one point is added in the depth direction, and frequency analysis is performed by FFT (Fast Fourier Transformation) for display. MTI (Moving Target Indicator)
In the device using, the frequency analysis is performed by adding at continuous points in the depth direction. Then, the result is displayed in a color corresponding to the direction of blood flow and the change in average velocity. Such a device has recently been attracting attention because it can diagnose a circulatory system, and particularly detect an abnormal flow of blood flow.

By the way, the ultrasonic echoes may have different amplitudes for various reasons. For example, due to the difference in the physical properties of the ultrasonic reflecting object such as myocardium, blood flow, liver, etc., due to the difference from the depth of the ultrasonic probe, the location such as the direction, etc.
There are differences due to differences in physical performance of the ultrasonic probe such as depth, frequency, number of transducers, aperture area, focal length, transmission / reception conversion efficiency, and transmission power.

In the past, the variation in the amplitude of these ultrasonic echoes was adjusted by the device so as to obtain the optimum gain. Then, for example, in the B-mode method, attention is paid to the difference due to the site from the ultrasonic probe, and the pre-STC
(Sensitivity Time Control), STC, and other technologies are used to suppress ultrasonic echoes from short distances and improve the sensitivity of ultrasonic echoes from long distances. But,
With such a method, the sensitivity characteristic can be set only artificially, and the sensitivity difference due to the difference in the physical properties of the ultrasonic reflecting object and the difference in the physical performance of the ultrasonic probe cannot be covered.

These factors have a great influence on the ultrasonic blood flow imaging apparatus. In particular, the influence of the above-mentioned difference in physical properties is remarkable, and the difference between the echoes of the myocardium, the blood vessel wall and the blood flow is very large.

[Problems of Background Art] FIG. 5 shows a configuration example of a conventional ultrasonic blood flow imaging apparatus. Amplifier 1 for ultrasonic echo signal by B mode
And the first and second mixers via the bandpass filter 2.
Input to 3a and 3d, and the reference signal in the first mixer 3a
Fref and the reference signal Fref−90 in the second mixer 3b.
After being mixed with .degree., They are input to the first and second low pass filters 4a and 4b, respectively. Then, high frequency components are removed from these two signals by the first and second low pass filters 4a and 4b, respectively, and the sensitivity characteristics are corrected by the first and second STC circuits 5a and 5b controlled by the STC controller 7. Further, the signals having phases different from each other by 90 ° are sent to the A / D converter (not shown) as real signals and imaginary signals through the first and second buffer amplifiers 6a and 6b.

However, in this device, if an attempt is made to sufficiently amplify the blood flow echo, there is a problem that the amplifier is saturated by a large echo signal from the myocardium or the like, its operating point is shaken with a large amplitude, and then the amplifier stops operating. is there. Also, especially
In the first and second mixers 3a and 3b, when a large-amplitude echo signal is mixed, the harmonic component becomes large and the output waveform is distorted.

Further, in the A / D converter, there is a problem that a large dynamic range and accuracy are required to extract the blood flow echo signal through the large amplitude echo signal.

[Object of the Invention] The present invention has been made in view of the above circumstances, and suppresses a large-amplitude echo signal based on a reflection echo signal from a myocardium, a cardiovascular wall, or the like to effectively generate a blood flow echo signal. It is an object of the present invention to provide an ultrasonic blood flow imaging apparatus in which each component such as a mixer, an amplifier, and an A / D converter can be kept normal functions while being taken out to improve its resolution.

[Outline of the Invention] An outline of the present invention for achieving the above object is to obtain a blood flow image of a subject on the basis of an echo signal subjected to frequency shift obtained by transmitting and receiving ultrasonic waves to and from the subject. In the ultrasonic blood flow imaging device configured to obtain, a means for suppressing the output of the echo signal is provided when the amplitude of the echo signal is larger than a signal obtained by inverting the envelope waveform signal of the echo signal. It is what

[Embodiment of the Invention] A first embodiment of the present invention will be described in detail below with reference to FIG. In the apparatus shown in FIG. 5, those having the same functions as those shown in FIG.
Detailed description thereof will be omitted.

The difference between the device shown in FIG. 1 and that shown in FIG.
The clutter removing circuit 8 is connected between the bandpass filter 2 and the first and second mixers 3a and 3b, and the STC controller 7 and the first and second STC circuits 5a and 5b are omitted.

The clutter removing circuit 8 takes in the output of the bandpass filter 2 and obtains its envelope waveform signal, and amplifies it, and an inverter (phase inversion) which inverts the phase of the envelope waveform signal and outputs it as a reference signal. 11), the echo signal from the bandpass filter 2 and the inverter
The reference signal from 11 is compared, and when the echo signal from the bandpass filter 2 is larger than the reference signal, the comparator (comparator) 12 that sends out a pulse signal and the echo signal from the bandpass filter 2 are compared. A delay circuit 13 for giving a constant delay time and a gate for inputting an echo signal from the bandpass filter 2 delayed by the delay circuit 13 and closing a gate based on the pulse signal to suppress an echo signal having a large amplitude. And a circuit 14.

The reason why the inverter 11 performs the phase inversion is to lower the reference potential of the comparator 12 at the next stage when the echo signal has a large amplitude and to raise the reference potential when the echo signal is a weak signal.

The delay circuit 13 is for correcting the phase delay of the pulse signal sent from the comparator 12.

Next, the operation of the device having the above configuration will be described.

The B-mode echo signal is amplified by the amplifier 1 and first input to the amplitude detector 10 via the bandpass filter 2.
Then, the envelope waveform signal of the echo signal is taken out here, amplified to a predetermined amplitude, and sent to the inverter 11. The inverter 11 performs a phase inversion process on this signal and sends it to the comparator 12 as a reference signal.

The comparator 12 compares the echo signal from the bandpass filter 2 with the reference signal, and when the echo signal is larger than the reference signal, sends a pulse signal corresponding thereto to the gate circuit 14.

On the other hand, the delay circuit 13 gives a constant delay time to the echo signal from the bandpass filter 2 and then sends it to the gate circuit 14. This delay time is set in advance so as to be a time required until the comparison process of the echo signal and the reference signal by the comparator 12 is completed.

The gate circuit 14 receives the echo signal to which a delay time has been added and, based on the pulse signal, closes the gate during the input period of this pulse signal to suppress the amplitude of the echo signal.

As a result, an echo signal having a large amplitude based on the reflection echo from the myocardium or the like is not sent to the first and second mixers 3a, 3b as it is, and therefore the waveform distortion due to the mixer is not generated as in the conventional device. Unstable operation of the amplifier is prevented. Further, as the A / D converter (not shown), a normal one can be used.

FIG. 2 shows a second embodiment of the present invention. still,
In the apparatus shown in the same figure, those having the same functions as those shown in FIG.

The apparatus shown in FIG. 2 is different from that shown in FIG. 1 in that the amplitude detector 10 in the clutter removing circuit 8 is omitted as the clutter removing circuit 8A and an ultrasonic wave is input as an input signal to the inverter 11. This is because the echo signal from the amplitude detector in the B-mode receiver provided separately in the diagnostic device was used.

The device of the second embodiment can also exert the same operation as the device shown in FIG.

FIG. 3 shows a third embodiment of the present invention, and in the apparatus of the present embodiment as well, those having the same functions as those shown in FIG. Is omitted.

The third embodiment is different from that shown in FIG. 1 in that the STC control signal from the STC controller 7 and the reference signal from the inverter 11 are added by the adder 15 so that the distance from the short distance is increased. This is because the clutter removing circuit 8C configured to increase the erasing level of the echo signal corresponding to the sound wave echo and send the attenuation reference signal corresponding to the attenuation characteristic of the ultrasonic wave to the comparator 12 is used.

According to the device of the third embodiment, since the pulse signal corresponding to the attenuation reference signal can be sent from the comparator 12 to the gate circuit 14, the suppression action of the large amplitude component which is more suitable for the attenuation characteristic of the echo signal. Can be demonstrated.

Needless to say, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist thereof.

FIG. 4 shows a modified example of the present invention. In the apparatus shown in FIG. 4 as well, those having the same functions as those shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. To do.

The device shown in FIG. 4 omits the inverter 11 and the comparator 12 as the clutter removing circuit 8C, and replaces the gate circuit 14 with an AGC (Auto Matic Gain Control) circuit 16 in which an amplifier and a ring diode attenuator are combined. This is to use the one that automatically controls the gain of the echo signal provided with the predetermined delay time by the delay circuit 13 based on the output signal of the amplitude detector 10.

The device shown in FIG. 4 can exert the same function as the device of the first embodiment, and in addition to this, even if there is a difference in sensitivity of the ultrasonic probe, the blood is always obtained with the optimum gain. An echo signal can be obtained based on the flow.

[Effects of the Invention] According to the present invention described in detail above, since a large amplitude echo signal from the cardiovascular wall or myocardium can be suppressed, an echo signal based on the blood flow can be efficiently extracted and a mixer, It is possible to provide an ultrasonic blood flow imaging apparatus which does not require any particular expansion of the dynamic range of other components of this apparatus such as a filter, an amplifier, an A / D converter, and which does not cause abnormal characteristics of these elements. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing the first embodiment of the present invention, and FIG.
FIG. 4 is a block diagram showing a second embodiment of the present invention, FIG. 3 is a block diagram showing a third embodiment of the present invention, FIG. 4 is a block diagram showing a modification of the present invention, and FIG. It is a block diagram which shows the structure of the conventional apparatus. 1 ... Amplifier, 2 ... Bandpass filter, 3a ... First mixer, 3b ... Second mixer, 4a ... First low-pass filter, 4b ... Second low-pass filter, 6a ... Second 1 buffer amplifier, 6b …… second buffer amplifier, 8,8A, 8B, 8C …… clutter removal circuit, 10 …… amplitude detector, 11 …… inverter, 12 …… comparator, 13 …… delay circuit, 14 …… Gate circuit, 15 …… Adder, 16 …… AGC circuit.

Claims (1)

[Claims] 1. An ultrasonic blood flow imaging apparatus, wherein an ultrasonic blood flow image is obtained by transmitting and receiving ultrasonic waves to and from a subject, and obtaining a blood flow image of the subject based on an echo signal subjected to frequency shift obtained. An ultrasonic blood flow imaging apparatus comprising means for suppressing the output of the echo signal when the amplitude of the echo signal is larger than the signal obtained by inverting the phase of the envelope waveform signal of the echo signal.