JPH0459895B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an ultrasonic Doppler device, in particular, a device that receives Doppler signals from a moving part that have received the Doppler effect, and accurately determines the blood flow state of a moving part such as the heart. The present invention relates to an ultrasonic Doppler device for pixel display.

[Prior art] Ultrasonic waves that emit an ultrasound beam intermittently or continuously into a subject such as a living body to display moving reflectors, that is, the state of cardiac blood flow and body fluid flow, in pixels on a CRT display. A Doppler apparatus is well known, and it determines the state of flow velocity and the like by detecting the Doppler effect received by reflected echoes from within the subject as a shift in the ultrasonic carrier frequency.

FIG. 2 shows a schematic configuration of a conventional device, in which a transmitting signal of a predetermined frequency is supplied from a transceiver 12 to a probe 10 that emits ultrasonic waves into the subject. By exciting the transducer within the probe 10 with this transmission signal, ultrasonic waves are emitted into the subject.

On the other hand, the ultrasonic waves are reflected from the moving part inside the subject, but this reflected echo is input to the transceiver 12 via the probe 10, and is orthogonally detected by the next mixer 13 and converted into a Doppler signal. . That is, the transmitter/receiver output is transmitted through two mixers 13a and 13b.
Here, the received signal is mixed with two types of reference numbers cosω ₀ t and sinω ₀ t at the ultrasonic carrier frequency and having a phase difference of 90 degrees. Therefore, the outputs of the mixers 13a and 13b are two types of signals in which information subjected to the Doppler effect is extracted, and these can be understood as complex signals in which one has a real part and the other has an imaginary part. The Doppler shift frequency can be calculated by processing the complex signal. That is, the outputs of the mixers 13a and 13b are supplied to the delay line canceller 16 via A/D converters 14a and 14b (details are described in Japanese Patent Publication No. 62-44494). In the Yancera 16, a signal shifted by one period on the delay line is subtracted from the current output signal. In this way, signals that do not change, such as in the stationary part, become zero, and only signals that change in the moving part are output. This makes it possible to eliminate signals (clutter signals) in the static part, such as the heart wall. .

The output of this dayley line canceller 16 is
The signal is supplied to the frequency calculation circuit 18, and the shift frequency is calculated by calculating, for example, the argument of the complex signal, which is a Doppler signal. This deviation frequency is information corresponding to the magnitude of the speed of the moving part, and the speed can be measured from a signal obtained by averaging this deviation frequency, and the direction of movement can be detected from the sign of the deviation frequency value. can do.

The motion information output from the frequency calculation circuit 18 is supplied to the display 22 via the color conversion circuit 20, and the motion information is converted into R (red) and G (green) by the color conversion circuit 20. - Since the signal is converted into a B (blue) signal and input to the display 22, the display 22 displays a color image of the state of movement of the moving part within the subject. Conventionally, motion information is displayed superimposed on a B-mode tomographic image obtained by a processing circuit (not shown).

[Problems to be Solved by the Invention] However, in such conventional devices, it is difficult to effectively remove unnecessary signals such as stationary parts from the reflected echo signal obtained by the transceiver 12 without losing Doppler information. Have difficulty.

That is, in the above example, the stationary part signal (clutter signal) is removed by the delay line canceller 16, but in this case, information about the stationary part that is almost stopped can be removed, but information about the stationary part where the blood flow velocity is low can be removed. Objects that move at the same low speed cannot be removed.

In addition, in the case of the heart, echo signals from tissues other than blood (fluid) such as the heart wall have high levels, so in order to remove unnecessary signals, all high-level signals are removed from the echo signals. It is also being done. However, in this case, unnecessary wall signals, heart valve signals, etc. other than blood flow information can be effectively removed, but at the same time some blood flow information is also removed, making it possible to obtain Doppler information well. I can't.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to effectively remove only unnecessary signals other than fluid information, and to display information close to the actual state of motion as an image. An object of the present invention is to provide an ultrasound Doppler device.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a transmitting/receiving circuit that emits ultrasonic waves into a subject and demodulates the reflected echo signal and converts it into a Doppler signal; a frequency calculation circuit that calculates a Doppler shift frequency, which is information on a motion state, from a signal, a level detector that detects the signal level of the Doppler signal, and a signal output from the level detector. a first comparator that compares the level with a predetermined reference value and outputs a signal if the level is greater than this reference value; a second comparator that outputs a signal when the signal is output, and a switch that switches the output of the frequency calculation circuit to zero when the signals of both the first comparator and the second comparator are output. It is characterized by comprising a circuit.

[Operation] According to the above configuration, the signal level of the Doppler signal is detected by the level detector, and the first comparator detects the signal level from a reference value that distinguishes the signal level from a signal from a tissue such as a heart wall or a heart valve. Outputs a signal if it is large (if it is a signal from tissue). On the other hand, the shift frequency signal obtained from the Doppler signal is compared with a predetermined reference value corresponding to a low frequency signal (low speed) by a second comparator, and outputs a signal if it is lower than this reference value. do. Therefore, a signal is output to the switching circuit when the signal level is high and the deviation frequency is low, and only in this case the frequency arithmetic circuit output is set to zero.

As a result, in addition to signals with low signal levels, signals with large signal levels and medium or high deviation frequencies are extracted, making it possible to more accurately display fluid velocity information that was previously discarded. become.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a block diagram of a schematic configuration of an ultrasonic Doppler apparatus according to the present invention.
The circuit configuration from the transmitter/receiver circuit including the 0 to A/D converters 14 and the frequency calculation circuit 18 to the display 22 is the same as the conventional one.

The characteristic feature of the present invention is that it effectively removes only unnecessary signals for displaying fluid motion information, and for this purpose, the present invention is capable of effectively removing signals that are unnecessary for displaying fluid motion information. Compare the signals and select unnecessary signals.

In the embodiment, a Doppler information screening circuit (wall motion circuit) 10 is used to remove unnecessary signals.
0 is provided, and first, an absolute value calculation circuit 24 is provided as a level detector that detects the signal level of the Doppler signal, and this absolute value calculation circuit 24
calculates the absolute value of the complex signal output from the A/D converter 14, x i is the amplitude of the signal output from the A/D converter 14a, and x _i is the amplitude of the signal output from the A/D converter 14b. Let the amplitude of be y _i , then the absolute value can be found from √ _i ² + _i ² .

The absolute value of this complex signal indicates the signal level, or amplitude, of the Doppler signal.In principle, a high signal level means that the reflector tissue is somewhat hard, or in the case of the heart, the heart wall. This means that the signal is from a tissue such as a valve, and a low signal level means that it is a signal from a fluid such as blood, but depending on the direction in which fluid signals are detected, they may overlap and may be at a large level. In addition, signals from blood near the heart valves are detected as large signals, and the necessary Doppler signals are included in those with large signal levels. Therefore, the present invention extracts such signal components.

For this reason, a first comparison circuit 26 is provided on the output side of the absolute value calculation circuit 24, and compares the signal level output from the absolute value calculation circuit 24 with a predetermined reference value. This reference value is set to a value that can distinguish whether the signal is from a fluid or a signal from a wall, heart valve, or other tissue, and when the signal level is greater than the reference value, a predetermined signal,
In the embodiment, one digital signal is output.

On the other hand, the second comparator 28 converts the shift frequency signal fd obtained by the frequency calculation circuit 18 into a predetermined reference value for distinguishing signals from tissues such as walls moving at low speed from other signals. It is compared with. Then, when the value is lower than this reference value, a predetermined signal, in this embodiment, a digital signal of 1 is output.

A switching circuit consisting of an AND circuit 30 and a switching device 32 is connected to the first comparator 26 and the second comparator 28, and both the first comparator 26 and the second comparator 28 When the output is a 1 signal, the AND circuit 30 outputs a 1 digital signal to the switch 32
Output to.

Then, the switch 32 switches the AND circuit 30 to 1
When the digital signal of is output, the output of the deviation frequency calculation circuit 18 is set to zero output, and in other cases, a digital signal of 0 is output from the AND circuit 30, and the output of the calculation circuit 18 is switched to be output as is. In the embodiment, this switch 32
has a ROM (read-only memory) that stores the speed value corresponding to the 0 value and the deviation frequency fd, and when the AND circuit output is a digital signal of 1, the stored information of 0 is read out, and the AND circuit outputs When is a digital signal of 0, speed information corresponding to the deviation frequency fd is read out.

The output of the AND circuit becomes a digital signal of 0 when the signal level of the Doppler signal is high and the deviation frequency is low.
From No. 2, only signals from tissues such as walls at a predetermined low speed or less are removed.

The embodiment has the above configuration, and its operation will be explained below.

First, the reflected echo signal obtained by the probe 10 is supplied to the mixer 13 via the transmitter/receiver 12, and the real part (mixer 13
a) and an imaginary part (mixer 13b), and this complex signal is a Doppler signal for extracting the Doppler shift frequency. and,
This complex signal is output to the frequency calculation circuit 18 via the A/D converter 14, and is also output to the absolute value calculation circuit 24, where the frequency calculation circuit 18 calculates the deviation frequency fd of the Doppler signal.

The absolute value calculation circuit 24 calculates the absolute value of the complex signal, thereby detecting the signal level of the Doppler signal, and the output of the absolute value calculation circuit 24 indicating this signal level is sent to the first comparator 26. It is compared with a predetermined reference value. Then, when the signal level is higher than the reference value, the first comparator 26 outputs a digital signal of 1.

On the other hand, the deviation frequency fd calculated by the frequency calculation circuit 18 is supplied to a second comparator 28, and from this second comparator 28 it is determined that when the deviation frequency fd is below a predetermined deviation frequency (reference value), A digital signal of 1 is output.

Then, a digital signal of 1 is output from the AND circuit 30, and in this case, the output of the frequency calculation circuit 18 is switched by the switch 32 so that it becomes a zero output. Therefore, only when the signal level of the Doppler signal is high and the deviation frequency is low, a signal with zero output is supplied to the color conversion circuit 20, and in other cases, the output of the frequency calculation circuit 18 is directly sent to the color conversion circuit 20. will be supplied.

This means that when the signal level is small, or when the signal level is large and has a medium or high frequency, the calculated deviation frequency is output as it is, but especially the signal that was previously discarded. The following advantages can be obtained by acquiring high-level, medium- or high-frequency signals.

That is, information based on Doppler signals with a high signal level, flow velocity information near the heart valve, etc. that is hidden by the heart valve moving at high speed, etc. can be displayed in a good manner on the display 22.

Further, such a display is provided by the first comparator 2.
This can be controlled by adjusting the reference values of 6 and the second comparator 28, and although not shown in the embodiment, an adjuster for adjusting these reference values is provided. According to this, it is possible to particularly adjust the second comparator 28 to obtain a good indication of the state of motion of the boundary portion between the tissue as a structure of the subject and the fluid.

[Effects of the Invention] As explained above, according to the present invention, the level of the Doppler signal and the deviation frequency value are compared, and only the signal where the signal level is high and the deviation frequency value is small is removed. As a result, it is possible to effectively capture Doppler information from fluids with high signal levels and fluid information such as flow velocity near heart valves that are hidden by heart valves that move at high speeds, which is close to the actual moving state. Information can be provided.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a schematic configuration of an ultrasonic Doppler device according to the present invention, and FIG. 2 is a circuit block diagram showing a schematic configuration of a conventional device. 10...probe, 12...transmitter/receiver, 13...
...Mixer, 16...Daily line canceller,
18...Frequency calculation circuit, 22...Display device, 24
... Absolute value calculation circuit, 26 ... First comparator, 2
8... Second comparator, 30... AND circuit, 32
...Switcher, 100...Doppler information selection circuit.

Claims (1)

[Claims] 1. A transmitting/receiving circuit that emits ultrasonic waves into the subject, demodulates the reflected echo signal, and converts it into a Doppler signal, and a frequency calculation circuit that calculates the Doppler shift frequency, which is information on the motion state of the moving part, from the Doppler signal. and a level detector for detecting the signal level of the Doppler signal, and a signal level output from the level detector is compared with a predetermined reference value, and if the signal level is greater than the reference value, the signal is detected. a first comparator that outputs a shift frequency signal obtained from the Doppler signal with a predetermined reference value, and a second comparator that outputs a signal when it is lower than this reference value; An ultrasonic Doppler apparatus comprising: a switching circuit that switches the output of a frequency calculation circuit to zero output when signals from both a comparator and a second comparator are output.