JPH0213448A - Ultrasonic wave doppler device - Google Patents

Abstract

PURPOSE:To enable an effective incorporation of the fluid information of the flow velocity, etc., at the vicinity of a cardiac valve by comparing a doppler signal level and a deviated frequency value, and eliminating the signal only in the case where the signal level is high and the deviated frequency value is low. CONSTITUTION:A reflected echo signal obtained with a probe 10 is converted into a complex signal with a mixer 13. With an absolute value operation circuit 24, the signal level of a doppler signal is detected with the absolute value of the complex signal operated, and the output of the signal level is compared with a given reference value with a first comparator 26. When the signal level is higher than the reference value, the digital signal of 1 is outputted from the comparator 26. On the other hand, a deviated frequency f d operated with a frequency operation circuit 18 is supplied to a second comparator 28, and when the frequency f d is below a given deviated frequency (reference value), the digital signal of 1 is outputted. This causes the digital signal of 1 to be outputted from an AND circuit 30, and in this case switching is made with a switching instrument 32 so that the output of the circuit 18 is made to a zero output.

Description

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

[Prior Art] Ultrasound displays an image of a moving reflector, that is, the state of cardiac blood flow and body fluid flow, on a CRT display by emitting an ultrasound beam intermittently or continuously into a subject such as a living body. A Doppler apparatus is well known, and it determines the state of flow velocity and the like by detecting the Doppler effect exerted on 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 transmitter/receiver 12 supplies a transmission signal of a predetermined frequency 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 ultrasound is reflected from a moving part within the subject, or 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 supplied to two mixers 13a and 13b, where the received signal is transmitted at the ultrasonic carrier frequency and at a phase difference of 90 degrees.
It is mixed with different reference signals (cos ω t, sin ω t). Therefore, the outputs of the mixers 13a and 13b are two types of signals in which information subjected to the Doppler effect is extracted.
This can be understood as a complex signal with one part being a real part and the other part being an imaginary part, and by processing this complex signal, the Doppler shift frequency can be calculated. That is, the outputs of the mixers 13a and 13b are supplied to a delay line canceller 16 via A/D converters 14a and 14b (details are described in Japanese Patent Publication No. 6144494). subtracts the current output signal from the signal that has undergone even one cycle on the delay line. In this case, signals that do not change such as at a stationary part become zero, and only signals that change at a moving part are output, thereby making it possible to remove signals (clutter signals) from a stationary part such as the heart wall.

The output of the delay line canceller 16 is supplied to a frequency calculation circuit 18, and a shift frequency is calculated by calculating, for example, the argument of a complex signal that 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. I can do something.

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 2o. - Converted to B (blue) signal and displayed on display 22
, the display 22 displays a color image of the movement state of the movement part within the subject. Conventionally, motion information is displayed superimposed on a B-mode tomographic image obtained by a processing circuit (not shown).

[Problem to be solved by the invention] However, in such a conventional device, the transmitter/receiver 12
It is difficult to effectively remove unnecessary signals such as stationary parts from the reflected echo signals obtained in the above-mentioned method without losing Doppler information.

That is, in the above example, the stationary part signal (clutter signal) is removed by the delay line canceller 16, or in this case, although information about the stationary part that is almost at rest can be removed, the information about the stationary part signal (clutter signal) is the same as that of a signal with low blood flow velocity. Objects that move at relatively low speeds 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. but,
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 of the blood flow information is also removed, making it difficult to obtain Doppler information. Can not.

OBJECT OF THE INVENTION The present invention has been made in view of the dual problems of the prior art.
The purpose is to provide an ultrasonic Doppler device that can effectively remove only unnecessary signals other than fluid information and display information close to the actual state of motion as an image.

[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 determined from the Doppler signal is compared by a second comparator with a predetermined reference value corresponding to a low frequency signal (slow velocity), and if it is lower than this reference value, the signal is Output. 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 calculation circuit power is set to zero output.

As a result, in addition to signals with small signal levels, signals with large signal levels and medium or high deviation frequencies are extracted, allowing more accurate image display of fluid velocity information that was previously discarded. That will happen.

[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, and includes a transmitting/receiving circuit consisting of a probe 10 to an A/D converter 14, and a frequency calculation circuit 18 to
The circuit configuration up to the display 22 is the same as the conventional one.

The characteristic feature of the present invention is that only signals unnecessary for displaying fluid motion information are effectively removed.
To this end, the present invention compares the level of the Doppler signal, that is, the amplitude value and the shift frequency value to select unnecessary signals.

In the embodiment, a Doppler information selection circuit (wall motion circuit) 100 is provided to remove unnecessary signals, and an absolute value calculation circuit 24 is provided as a level detector for detecting the signal level of the Doppler signal. The absolute value calculation circuit 24 calculates the absolute value of the complex signal output from the A/D converter 14.
Xl, the amplitude of the signal output from the A/D converter 14b
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.
In the case of the heart, this means that it is a signal from tissues such as the heart wall and heart valves, and a low signal level means that it is a signal from fluid such as blood, but fluid signals are detected. Depending on the direction, the signals may overlap, resulting in high-level signals, and signals from blood near the heart valves will be detected as high-level signals, and the necessary Doppler signals are included in the high-level signals. 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 it is a signal from the fluid or a signal from tissues such as walls or heart valves, and when the signal level is higher than the reference value, a predetermined signal is detected. Then output a digital signal of 1.

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 10 digital signal 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.

Then, the switch 32 sets the output of the deviation frequency calculation circuit 18 to zero when a digital signal of 1 is output from the AND circuit 30, and outputs a digital signal of O from the AND circuit 30 in other cases. It is switched to output the output of the arithmetic circuit 18 as it is, and in the embodiment, this switch 32 is equipped with a ROM (read-only memory) that stores a zero value and a speed value corresponding to the deviation frequency fd. When the output of the AND circuit is a digital signal of 1, stored information of zero is read out, and when the output of the AND circuit is a digital signal of O, speed information corresponding to the shift frequency fd is read out.

The AND circuit output becomes a digital signal of O when the signal level of the Doppler signal is high and the deviation frequency is low. Only the signal from the tissue will be 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 transceiver 12, and the mixer 13 separates the real part (mixer 13a) and the imaginary part (mixer 1
3b), which is a Doppler signal for extracting the Doppler shift frequency. This complex signal is then 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. Ru.

The absolute value calculation circuit 24 calculates the absolute value of the complex signal, thereby detecting the signal level of the Doppler signal1+I1.
．． ．． The absolute value calculation circuit 24 indicates this signal level.
The output of is compared with a predetermined reference value by a first comparator 26. 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 from the frequency calculation circuit 18 is supplied to the second comparator 28, and the second
A digital signal of 1 is output from the comparator 28 when the deviation frequency is below a predetermined deviation frequency (reference value).

Then, the AND circuit 30 outputs a digital signal of 1, and in this case, the switch 32 switches between the output of the frequency calculation circuit 18 and the zero output. Therefore, only when the signal level of the Doppler signal is high and the deviation frequency is low, a zero output signal is supplied to the color conversion circuit 20, and in other cases, the output of the frequency calculation circuit 18 is directly supplied to the color conversion circuit 20. will be done.

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 for 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 an excellent manner on the display 22.

Further, such a display can be controlled by adjusting the reference values of the first comparator 26 and the second comparator 28, and although not shown in the embodiment, an adjuster for adjusting these reference values is used. We are prepared. According to this, in particular, the second comparator 28 can be adjusted to better display the state of motion of the boundary between the tissue and the fluid as a structure of the subject.

[Effects of the Invention] As described above, according to the present invention, the level of the Doppler signal and the deviation frequency value are compared, and only the signal when the signal level is high and the deviation frequency value is small is selected. Since this feature is removed, 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 is hidden by heart valves that move at high speeds, thereby allowing the detection of actual motion conditions. It becomes possible to provide information close to .

[Brief explanation of the drawing]

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 ... Delay line canceller 18 ... Frequency calculation circuit 22 ... Display 24 ... Absolute value calculation circuit 26 ... First comparison Device 28... 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 that calculates the Doppler shift frequency, which is information about the motion state of the moving part, from the Doppler signal. an ultrasonic Doppler apparatus having an arithmetic circuit; 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. a first comparator that outputs a signal, and a second comparator that compares the shift frequency signal obtained from the Doppler signal with a predetermined reference value and outputs a signal if it is lower than the reference value;
An ultrasonic wave characterized by comprising: a switching circuit that switches the output of the frequency calculation circuit to zero output when signals from both the first comparator and the second comparator are output. Doppler device.