JPH0747025B2 - Ultrasonic Doppler blood flow diagnostic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to an ultrasonic Doppler blood flow diagnostic apparatus which obtains blood flow information by an ultrasonic Doppler method and is used for diagnosis.

(Prior Art) For example, in analyzing and diagnosing the circulatory system, observing blood flow and blood pressure flowing in the heart and blood vessels and obtaining the information is
Most importantly. And in this observation, ultrasonic Doppler is excellent in that it can be observed in a non-invasive and natural state that does not substantially disturb the circulatory system. Among them, as blood flow information detection, distance resolution is excellent. For this reason, the ultrasonic pulse Doppler method (ultrasonic pulse modulation Doppler method) is used.

In recent years, the clinical application of an ultrasonic pulse Doppler blood flow meter for performing Doppler observation using ultrasonic pulses is becoming established, and the applicable diagnostic area extends to large and medium blood vessels of the whole body.

However, in the vicinity of the heart and respiratory system, the movement of blood vessels due to heartbeats and respiration is large, and it is difficult to keep the sample gate for blood flow at a designated portion of continuous blood vessels. For this reason, the sample gate fluctuates in the blood vessel during measurement, and not only the true blood flow velocity cannot be measured, but in the case of a thin blood vessel, the sample gate periodically deviates from the blood vessel and captures a weak blood flow Doppler component. I can't. Therefore, a method in which the sample gate is made to follow the movement of the blood vessel wall has been attempted. This uses a Phase Locked Loop (PLL) and is called an echo tracking method.

That is, specifically, this type of blood flow diagnostic apparatus, for example,
Sector electronic scanning type (sector electronic scanning method) ultrasonic diagnostic equipment is used to sequentially scan the ultrasonic beam with a sector electronic scanning probe, which is a kind of array transducer in which a plurality of micro-vibration elements are arranged in parallel. Then an ultrasonic tomographic image is obtained by receiving the echo and displaying it.At the same time, the ultrasonic beam is emitted in a predetermined sector direction including the Doppler observation target part. By receiving the echo,
The frequency shift of the transmitted and received waves is obtained, and the blood flow velocity and direction information is obtained from this, and this observation information is displayed together with the tomographic image.The echo from the predetermined sector direction including the Doppler observation target part is displayed. Of these, a sample gate is applied to shift the time in accordance with the movement of the blood vessel wall so as not to capture the echo of the blood vessel wall position, and by extracting the received signal from the blood vessel position portion, the blood flow velocity and This is to get information on the direction. A composite ultrasonic probe provided with such an array transducer and a single transducer is used to perform a sector scan with the array transducer to obtain a B-mode image.
There is also a transducer in which Doppler measurement is performed to obtain information on blood flow velocity and direction.

However, in such a method, since the reflection signal (echo) from the blood vessel wall portion is also received, the Doppler shift component due to the movement of the blood vessel wall is also included. Therefore, the S / N
Not only does the (signal / noise ratio) deteriorate, but the true blood flow velocity cannot be captured.

(Problems to be Solved by the Invention) As described above, in order to avoid the influence of the blood vessel wall, the conventional blood flow diagnostic apparatus attempts to use the echo tracking method in which the sample gate follows in the same manner as the movement of the blood vessel wall. However, in this method, the Doppler shift component due to the movement of the blood vessel wall is also included, and therefore the S / N (signal / noise ratio)
Not only did it worsen, but there was a drawback that the true blood flow velocity could not be captured.

Therefore, the object of the present invention is to remove the Doppler shift component due to the movement of the blood vessel wall and the heart wall,
An object is to provide an ultrasonic Doppler blood flow diagnostic apparatus that can obtain accurate blood flow information.

[Structure of Invention]

(Means for Solving Problems) In order to achieve the above object, the present invention is configured as follows. That is, an ultrasonic drive pulse signal generating means for generating an ultrasonic drive pulse signal at a predetermined repetition cycle, an ultrasonic probe for transmitting and receiving ultrasonic waves to and from blood in the circulatory organ tissue, and the ultrasonic probe. A means for obtaining a blood flow Doppler signal by mixing at least a reflection component due to blood and a reference signal among the reflected ultrasonic signals obtained by the tentacle, and Doppler by sampling and holding this blood flow Doppler signal by a sampling hold signal. Sampling and holding means for extracting the blood flow Doppler signal from the target position for measurement,
A means for detecting a depth change of the circulatory organ tissue with respect to the ultrasonic probe and a variable phase means for controlling the phases of the ultrasonic drive pulse signal and the sampling and holding signal based on the depth change are used.

(Operation) In such a configuration, the ultrasonic wave drive pulse signal generating means generates an ultrasonic wave drive pulse signal at a predetermined repetition period, and the ultrasonic wave drive pulse signal drives the ultrasonic probe to circulate the circulator. While transmitting ultrasonic waves to the blood in the tissue and receiving the reflected echo, at least the reflected component by blood and the reference signal among the reflected ultrasonic signals obtained by this ultrasonic probe. The blood flow Doppler signal is mixed to obtain a blood flow Doppler signal, and the depth change is detected by means for detecting the depth change of the circulatory organ tissue with respect to the ultrasonic probe. Then, the phase of the ultrasonic drive pulse signal and the sampling hold signal are controlled by the variable phase means based on the depth change, and the blood flow Doppler signal is sampled and held by the sampling hold signal for use in Doppler measurement. The blood flow Doppler signal from the position is extracted. Then, by controlling the phase of the ultrasonic drive pulse signal based on the depth change of the target portion, the ultrasonic echo from the target portion due to the ultrasonic pulse of the previous transmission and the ultrasonic pulse of the present transmission are complicated. Then, the ultrasonic wave transmission / reception is made to follow the movement of the target portion so as not to affect the measurement, and the ultrasonic pulse is transmitted / received with respect to the target portion, and the timing of the sampling hold is the phase control described above. The shape is such that ultrasonic echoes of only the target portion, excluding the echoes from the wall of the circulatory organ tissue, can be obtained. Therefore, it is not necessary to capture the echo from the wall of the circulatory organ tissue, the depth of which changes according to the pulsation as in the conventional case, and it becomes possible to perform accurate Doppler observation by capturing the echo of only the target portion.

Therefore, according to the present invention, the Doppler shift component due to the movement of the blood vessel wall and the heart wall can be removed, and accurate blood flow information can be obtained.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram showing the configuration of this device.
3 and 4 are timing charts for explaining the operation of this device.

In FIG. 1, reference numeral 1 is a reference signal oscillator for generating a reference sine wave signal. Reference numeral 2 is a rate pulse generator, which divides the reference sine wave signal output from the reference signal oscillator 1 by a predetermined frequency division ratio to generate and output a rate pulse signal having a predetermined repetition period. Reference numeral 3 is a burst width setting device, which outputs the input pulse having a set width. Reference numeral 4 denotes a burst generator, which extracts and outputs the reference sine wave signal output from the reference signal oscillator 1 for a predetermined period corresponding to the output pulse width of the burst width setting device. The pulsar 5 receives a sine wave signal of a predetermined cycle output from the burst generator and generates a drive signal of a level capable of ultrasonically driving.
An ultrasonic probe (probe) 6 has a function of receiving an output from the pulsar 5 and being excited to transmit an ultrasonic wave, and receiving a reflected wave thereof to convert it into an electric signal.

Reference numeral 7 is a living body as a subject, 8a is a blood vessel wall, and 8b is blood.
A preamplifier (preamplifier) 9 amplifies the output signal of the ultrasonic probe 6, and a mixer 10 multiplies the amplified output by the reference sine wave output by the reference signal oscillator 1. The difference component is obtained. 11 is a low pass
The filter is for extracting only the low frequency component of the output of the mixer 10. 12 is a sample hold circuit, 13
Is a sampling pulse generator, sample and hold circuit
Reference numeral 12 samples and holds the output of the mixer 10 sent through the low-pass filter 11 by the sampling pulse output from the sampling pulse generator 13. Reference numeral 14 denotes a bandpass filter, which extracts a band component from the signal sample-held by the sample-hold circuit 12. A changeover switch circuit 15 selects either the rate pulse generator 2 or the output of a counter 29 described later and supplies it to the burst width setting unit 3. The changeover switch circuit 15 is controlled by a control means (not shown) so that it is switched to the side a when the gate pulse is not made to follow the movement of the target portion, and is switched to the side b when the gate pulse is made to follow the movement of the target portion. To be done.

Reference numeral 20 denotes an ultrasonic transmission pulse phase variable circuit, which is composed of constituent elements 21 to 31 below. That is, 21 is a gate pulse generator, which is obtained by delaying the rate pulse output from the rate pulse generator 2 by a delay time set according to the depth to be measured when the gate is not made to follow the target portion. When the gate is made to follow the target portion by the pulse, it operates in synchronization with the output of the comparator 28 to generate a gate signal having a predetermined pulse width. 22 is a gate circuit,
Only when the output pulse of the gate pulse generator 21 is received and the pulse is received, the saturated signal of the output of the preamplifier 9 is passed. 23 is an integrator circuit, and this gate circuit 22
The output of is integrated. An adder circuit 24 adds the integrated output and the output of a DC setting circuit 31 described later. Reference numeral 25 is a low-pass filter for extracting the low frequency component of the output of the adder circuit 24, and 26 is a gated signal generator, which outputs the output of the reference signal generator 1 in synchronization with the rise of the output signal of the gate pulse generator 21. A pulse having the same frequency as the frequency is generated. 27 is a ramp wave generation circuit,
A ramp wave is generated with the rate pulse generation cycle, and the ramp wave serves as a reference for determining the depth of the ultrasonic echo to be extracted. The comparator 28 compares the ramp wave with the output of the low-pass filter 25, and outputs a pulse when the voltage levels match.
29 is a counter, which starts counting the gated signal in synchronization with the rising edge of the gate pulse,
When the count value reaches a preset value, a pulse (carry) CC1 is generated and given to the sampling pulse generator 13, and the count value of the gated signal started in synchronization with the rising of the gate pulse is When a preset value corresponding to the time for generating an ultrasonic pulse is reached, a pulse CC2 is generated and given to the b-side terminal of the changeover switch circuit 15. The DC setting circuit 31 starts the gate pulse signal generation time t from the rising edge of the rate pulse signal.
Is for generating a DC voltage (DC voltage) proportional to the output voltage, and the output voltage can be set to a desired value. Further, the gate pulse generator 21 receives the output of the comparator 28 and generates a gate pulse.

Next, the operation of the present apparatus having the above configuration will be described. The reference sine wave signal generated by the reference signal oscillator 1 is frequency-divided by the rate pulse generator 2 and converted into a rate pulse signal having a predetermined repetition period. The rate pulse signal or the output pulse of the counter 29 is given to the burst width setting device 3 through the changeover switch circuit 3, and is converted into a pulse width signal set by the burst width setting device 3 to generate a burst. Input to the container 4. Burst generator 4
Extracts the reference sine wave signal corresponding to this pulse width and supplies it to the pulser 5. That is, every time the rate pulse signal or the output pulse of the counter 29 is received, the burst generator 4 extracts several cycles (set width of the burst width setter 3) of the reference sine wave signal and outputs this signal ( The burst signal) is supplied to the ultrasonic probe 6 as a transmission pulse signal via the pulser 5 and is energized.

As a result, the ultrasonic probe 6 transmits an ultrasonic pulse into the living body 7, and receives a reflected wave (ultrasonic echo) of the ultrasonic pulse by the blood vessel wall 8a and the blood (red blood cells) 8b. Convert to received signal.

Here, the Doppler shift frequency fd for the blood flow of the reflected wave signal is the frequency of the ultrasonic pulse fc, and fc >>
When there is a relationship of fd, it is expressed by fd = (2vcosθ / C) fc (1). Here, V is the blood flow velocity, θ is the angle between the traveling direction of the ultrasonic pulse and the blood flow direction, and C is the propagation velocity of the ultrasonic pulse in the living body (about 1530 m / sec).

Therefore, the blood flow velocity V can be obtained from the relationship of the equation (1).

On the other hand, the reception signal of the ultrasonic echo obtained by receiving the ultrasonic probe 6 is amplified by the preamplifier 9 and then
The mixer 10 multiplies and mixes with the reference sine wave signal, extracts the difference component, that is, the signal component (frequency shift component) excluding the carrier component, and extracts the low pass filter (low pass filter; LPF). It is sent to 11, where harmonic components are removed and detected as a Doppler signal.

The sample hold circuit 12 is a sampling pulse generator 13
It is provided to extract a signal component of a specific depth, that is, a component corresponding to the blood flow, from the Doppler signal according to the sampling pulse signal generated in.

Therefore, the Doppler signal from the desired depth extracted by the sample hold circuit 12 is then sent to a bandpass filter (bandpass filter; BPF) 14 where a harmonic signal and a blood vessel wall or the like are relatively generated. Doppler shift due to slow movement is eliminated. After that, the frequency is converted by a spectrum analyzer, a cross counter, or the like (not shown) for observation. Thus, the blood flow information is detected.

Next, the operation of the ultrasonic transmission pulse phase varying circuit 20 for causing the sampling position of the Doppler signal to follow the pulsation of the tissue will be described.

Rate pulse signal output from rate pulse generator 2
RP ((a) in FIG. 2) is used for generation of a transmission burst wave and is also guided to the gate pulse generator 21 of the phase variable circuit 20. The gate pulse generator 21 delays the rate pulse signal RP for a predetermined time corresponding to the target depth, and then, in synchronization with this delay signal, a gate pulse signal GP having a predetermined pulse width ((c) in FIG. 2). ) Occurs. At this time, the delay time is determined in accordance with the depth when the blood vessel wall 8a on the ultrasonic probe 6 side comes closest to the ultrasonic probe 6.

The reflected ultrasonic signal RS ((b) in FIG. 2) received by the ultrasonic probe 6 is amplified by the preamplifier 9 and then supplied to the mixer 10 and ultrasonic transmission pulse. It is guided to the gate circuit 22 of the phase variable circuit 20.

As shown in FIG. 3 (d), the gate circuit 22 receives the ultrasonic echo reception signal RS (FIG. 3 (b)) according to the gate pulse signal GP (FIG. 3 (d)). When a signal saturated with the signal ((c) in FIG. 3) is gated and a specific portion to be measured (for example, the blood vessel at a specific position comes closest to the transmitting / receiving surface of the ultrasonic probe 6) Signal GS ((e) in FIG. 3) only at the depth position of (3). Then, the output signal GS of only the specific portion thus extracted is integrated by the integrating circuit 23 ((f) in FIG. 3). As a result, a reflection signal portion due to the blood vessel wall 8a having a high echo signal level is extracted.

That is, the gate is set so as to correspond to the depth position when the blood vessel at the set specific position comes closest to the transmitting / receiving surface of the ultrasonic probe 6, and the width of the gate is set smaller than the blood vessel width. If so, the echo signal in the gate is extracted and integrated to obtain a level corresponding to the position of the blood vessel wall 8a with respect to the ultrasonic probe 6 (the echo signal due to the reflection of the blood vessel wall 8a has a high level). You can get a signal.

On the other hand, in the DC setting circuit 31, a DC voltage value proportional to the time t from the rise of the rate pulse signal RF to the gate pulse signal GP is set, and the voltage is output in synchronization with the rise of the rate pulse signal RP and added. Given to circuit 24. Then, the adder circuit 24 adds the integrator circuit output signal IS and the DC voltage value. Therefore, the signal corresponding to the distance to the wall portion of the blood vessel of the desired depth, which is extracted and integrated by the gate circuit 22, corresponds to the time t from the rise of the rate pulse signal RP to the output of the gate pulse signal GP. The shape is adjusted by the voltage value. Then, the added value and the low pass filter 25 are introduced.

Then, the high frequency components are filtered here. Therefore, the output signal LS of the low-pass filter 25 ((g) in FIG. 3) is almost only a DC component including the time component element.

The ramp wave generating circuit 27 generates a ramp wave LP ((h) in FIG. 3) corresponding to the elapsed time in the cycle of the rate pulse RP. Then, the ramp wave LP is compared with the low-pass filter output LS by the comparator 28, and an output pulse S1 ((i) in FIG. 3) is generated when the voltage levels match. Since the output pulse S1 of the comparator 28 is fed back to the gate pulse generating circuit 21, it is possible to obtain a gate pulse corresponding to the depth corresponding to the blood vessel wall position accompanying the pulsation of the blood vessel wall 8a. Become. Therefore, at the time of generation of the rate pulse in the next and subsequent times, the above-mentioned operation will be repeated with the gate aligned with the depth position of the blood vessel wall 8a associated with the pulsation.

Returning to FIG. 2 again, description will be made. The gate pulse GP ((c) in FIG. 2) follows the movement of the blood vessel wall as just described.

Now, in synchronization with the rise of the gate pulse GP, a gated signal is generated by the generator 26 to generate a pulse (or burst wave) signal having the same frequency as that of the reference signal oscillator 1 as shown in FIG. Next, in the counter 29, the gated signal output GO is used as a clock signal from the rise of the gate pulse GP, and the carry signal CC1 is input to the sampling pulse generator 13 by counting the number set by the preload of the counter. As a result, the sampling pulse generator 13 outputs the waveform shown in FIG. That is, when the gate pulse signal GP is shifted, the sampling pulse is also shifted with the movement.

Similarly, the output signal CC2 of the other system of the counter 29 (second
(G) in the figure is also input to the changeover switch circuit 15.
The control of the changeover switch circuit 15 is switched to the a side when the ultrasonic echo does not follow the gate pulse, and to the b side when the ultrasonic echo follows the gate pulse. An output signal CC2 of the counter 29 is given to the b-side terminal, and the output signal CC2 determines the timing for energizing the next ultrasonic pulse at a predetermined time from the rise of the gate pulse. , Can be set arbitrarily.

Therefore, when the gate pulse is made to follow the ultrasonic echo, the changeover switch circuit 15 is switched to the b side, and the output signal CC2 of the counter 29 activates the next ultrasonic pulse at a predetermined time from the rise of the gate pulse. The timing can be determined, and the phase of the ultrasonic transmission pulse can be changed by following the movement of the ultrasonic echo from the blood vessel wall 8a, that is, following the position of the blood vessel wall. Further, since the sampling and holding timing of the sampling and holding circuit 12 can be adjusted by the output CC1 of the counter 29, by appropriately setting the preload value of the counter 29, only the echo from the blood portion excluding the echo from the blood vessel wall is obtained. You will be able to.

That is, by controlling the phase of the ultrasonic drive pulse signal based on the depth change of the target portion, the ultrasonic echo from the target portion due to the ultrasonic pulse of the previous transmission and the ultrasonic pulse of the present transmission are complicated. And in the form of following the movement of the target portion of the ultrasonic transmission and reception so as not to affect the measurement, ultrasonic pulse transmission and reception to the target portion,
Further, the timing of sampling and holding is such that an ultrasonic echo of only the target portion can be obtained by removing the echo from the wall of the circulatory organ tissue. Therefore, it is not necessary to capture the echo from the wall portion of the circulatory organ tissue, the depth of which changes according to the pulsation as in the conventional case, and it becomes possible to perform accurate Doppler observation by capturing the echo of only the target portion.

When the gate pulse is not made to follow the ultrasonic echo, the rate pulse causes the gate pulse generator 21 to operate in synchronization.

Further, the echo signal can be obtained by quadrature detection, sampling, filtering to obtain a frequency shift, and Fourier transform of this to obtain sound velocity information. The positioning of Doppler observation is performed by referring to the B-mode image.

As described above, the present apparatus generates the ultrasonic wave drive pulse signal at a predetermined repetition cycle by the ultrasonic wave drive pulse signal generating means, and drives the ultrasonic wave probe by the ultrasonic wave drive pulse signal so that the ultrasonic wave is generated in the circulatory tissue. Of the reflected ultrasonic signal obtained by this ultrasonic probe, at least the reflected component of blood and the reference signal are mixed together. To obtain a blood flow Doppler signal, and to detect the depth change by means for detecting the depth change of the circulatory organ tissue with respect to the ultrasonic probe, and the ultrasonic wave based on the depth change by the variable phase means. The phase of the drive pulse signal and the sampling and holding signal are controlled, and the blood flow Doppler signal is sampled and held by the sampling and holding signal to perform Doppler measurement. It is obtained so as to extract a blood flow Doppler signal from a target position to be subjected to. Then, by controlling the phase of the ultrasonic drive pulse signal based on the depth change of the target portion, the ultrasonic echo from the target portion due to the ultrasonic pulse of the previous transmission and the ultrasonic pulse of the present transmission are complicated. Then, the ultrasonic wave transmission / reception is followed by the movement of the target portion so as not to affect the measurement, and the ultrasonic pulse transmission / reception is performed with respect to the target portion. This makes it possible to obtain an ultrasonic echo of only the target portion without the echo from the wall of the circulating tissue. Therefore, it is not necessary to capture the echo from the wall portion of the circulatory organ tissue, the depth of which changes according to the pulsation as in the conventional case, and it becomes possible to perform accurate Doppler observation by capturing the echo of only the target portion.

Therefore, the Doppler shift component due to the movement of the blood vessel wall or the heart wall can be removed, and accurate blood flow information can be obtained.

The present invention is not limited to the embodiments described above and shown in the drawings, and may be appropriately modified and implemented within the scope of the invention.

〔The invention's effect〕

As described in detail above, according to the present invention, the Doppler shift component due to the movement of the blood vessel wall or the heart wall can be removed, and accurate blood flow information can be obtained. It is possible to provide an ultrasonic Doppler blood flow diagnostic apparatus having the characteristics of.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of this device.
3 and 4 are timing charts for explaining the operation of this device. 1 ... Reference signal oscillator, 2 ... Rate pulse generator, 3
…… Burst width setting device, 4 …… Burst generator, 5 ……
Pulser, 6 ... Ultrasonic probe, 7 ... Living body, 9 ... Preamplifier, 10 ... Mixer, 11,25 ... Low pass filter, 12 ... Sample hold circuit, 13 ... Sampling pulse generator, 14 …… Band pass filter, 15 …… Changeover switch, 20 …… Ultrasonic transmission pulse phase variable circuit,
21 …… Gate pulse generator, 22 …… Gate circuit, 23 ……
Integrator circuit, 24 ... Adder circuit, 26 ... Gated signal generator, 27 ... Ramp wave generator circuit, 28 ... Comparator, 29 ... Counter.

Claims (1)

[Claims] 1. An ultrasonic drive pulse signal generating means for generating an ultrasonic drive pulse signal at a predetermined repetition cycle, an ultrasonic probe for transmitting and receiving ultrasonic waves to and from blood in a circulatory organ tissue, A means for obtaining a blood flow Doppler signal by mixing at least a reflection component due to blood and a reference signal in the reflected ultrasonic signal obtained by the ultrasonic probe, and a sampling hold signal for sampling and holding the blood flow Doppler signal. And sampling and holding means for extracting the blood flow Doppler signal from the target position to be used for Doppler measurement,
An ultrasonic probe comprising means for detecting a change in depth of the circulatory organ tissue with respect to the ultrasonic probe; and variable phase means for controlling the phases of the ultrasonic drive pulse signal and the sampling and holding signal based on the depth change. Sonic Doppler blood flow diagnostic device.