JPS61187842A - Ultrasonic pulse doppler blood stream meter - 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 an ultrasonic pulse Doppler blood flow meter used in the medical field to measure blood flow velocity in a living body.

BACKGROUND OF THE INVENTION Recently, ultrasonic pulse Doppler blood flowmeters have become popular in medical fields such as the heart and circulation. This ultrasonic/wave pulse Doppler blood flow meter is based on the principle that when an ultrasonic pulse transmitted into a living body is reflected by a moving object such as blood flow, it undergoes a frequency shift due to the Doppler effect, and it corresponds to the blood flow velocity. By displaying the Doppler shift frequency, it is now possible to observe the velocity and distribution of blood flow within the body from the body surface.

Examples of this conventional ultrasonic pulse Doppler blood flow meter include IICICE, Trans, 5, U (SU-17
(3): 170, 1970) and the like are known. The conventional ultrasonic pulse top 2 blood flow meter will be described below with reference to FIG. In FIG. 4, 201 is a probe that transmits and receives ultrasonic pulses to and from a living body, 202 is a transmitting circuit that generates a driving voltage for the probe 201 to generate ultrasonic waves, and 203 is a transmitting circuit 2.
02 is a timing circuit that provides a trigger to generate a pulse voltage, 204 is an amplifier circuit that amplifies the received signal obtained by the probe 201, and 205 is a quadrature circuit that performs phase detection of the received signal amplified by the amplifier circuit 204. a reference signal generation circuit that generates a reference signal; 206 a quadrature phase detector that performs quadrature phase detection of the echo signal amplified by the amplifier circuit 204 using the quadrature reference signal from the reference signal generation circuit 205; 207 a quadrature phase detector 206; An integrating circuit integrates the phase-detected orthogonal phase signal over the interval in which the timing signal of the timing circuit 203 is generated; 208 is a sample hold circuit that holds the integration result of the integrating circuit 207; and 209 controls the transmitting circuit 202 and the amplifier circuit 204. This is a control circuit that

Next, its operation will be explained. timing circuit 203
Then, the transmission timing signal 231, the gate signal 232 of the integrating circuit 207, and the reset signal 233 of the integrating circuit 207
is occurring. The transmission timing signal 231 gives timing for generating a pulse voltage to the trigger input 221 of the transmission circuit 202, and the pulse voltage generated by the trigger is applied to the vibrator of the probe 201 through the drive output 223.

The vibrator is generally made of a piezoelectric material, and the vibrator excited by a pulse voltage transmits ultrasound into the living body, and echo signals reflected from the living body from a depth corresponding to the propagation time of the ultrasound are sent to the probe 201. reach. The echo signal is converted into an electric signal by the probe 201, moderately amplified by the amplifier circuit 204, and then applied to the quadrature phase detector 206. The quadrature phase detector 206 converts the echo signal applied to the echo signal input 261 into a real part 262X and an imaginary part input 262
Orthogonal detection is performed using an orthogonal reference signal of y, and outputted to a real part output 263X and an imaginary part output 263y. A signal whose average value is the phase difference voltage between the quadrature reference signal and the echo signal is obtained from the detection outputs 263x and 263y subjected to quadrature detection by the quadrature phase detector 206, and the integrating circuit 207 outputs a real part 263x and an imaginary part output. 263y are integrated. The integration period is determined by the integration gate signal 232 of the timing circuit 203, and is given the time based on the transmission timing signal 231 and the time width for integration. After integration, the integral output is 271
, 2717, the sum of the quadrature phase difference voltages within the integration interval appears. Integral output 271 with sample hold circuit 208
By holding the sum of the orthogonal phase difference voltages of X and 2717 immediately after the completion of integration, the results of the above series of operations are output as orthogonal signals, with the real part being output to the output X and the imaginary part being output to the output Y. After holding, the integrating circuit 207 is reset by the reset signal 233.

Problems to be Solved by the Invention However, in the conventional configuration as described above, when an echo signal from a stationary tissue other than blood flow is captured, the integration circuit 20
Since at least one of the integral outputs 271X and 2717 of 7 is always saturated, a phenomenon has occurred in which no signal is output to the orthogonal drag-shift signal outputs X and Y. FIG. 5 explains the operation of the integrating circuit 207.
Figure a shows the transmission timing S and the transmission pulse voltage T.

As shown in the figure, which shows the relationship between the integral signal G and the echo signal I, when echo signals mainly from blood flow are captured, the intensity of the echo signal I is relatively weak and the phase also changes each time, so the integral output Doppler shift signals appear at 271 C, integral output 271!
, 2717 output a signal in which a Doppler shift signal is superimposed on a DC component. However, if the gain of the amplifier circuit 204 is larger than necessary, or if the integration interval of the integral signal G is long, the DC component will also be amplified, and the Doppler shift signal will not be output due to the saturation voltage of the integrating circuit 207, and will always be at the saturation voltage Z. Only the sample and hold circuit 208 passes through the output X,
It appears in Y.

Therefore, even if frequency analysis is performed, results can only be obtained continuously or intermittently, and even if either the output This created a confusing situation, posing a clinical problem when blood flow was measured.

Therefore, the present invention solves the above-mentioned conventional problems.
An object of the present invention is to provide an ultrasonic pulse Doppler blood flow meter that can prevent Doppler shift signals from being dropped when echo signals from stationary tissue are captured.

Means for solving the problems and technical means of the present invention for solving the above problems include a probe that transmits and receives ultrasonic pulses, a transmission circuit that drives this probe, A timing circuit that provides a timing signal to generate a pulse voltage to this transmitter circuit, a reference signal generation circuit that generates a quadrature reference signal in synchronization with the timing signal from this timing circuit, and amplifies the echo signal received by the probe. a phase detector that performs orthogonal phase detection of the echo signal amplified by the amplifier circuit using the orthogonal reference signal; and an integrating circuit that integrates the orthogonal phase signal of the phase detector in synchronization with the timing signal. , a comparator that detects that this integrating circuit is in a saturated state and outputs a status signal, a control that issues a warning upon receiving the status signal of this comparator, controls the time constant of the integrating circuit, and controls the gain of the amplifier circuit. It is equipped with a control circuit that performs the control selectively or in combination.

According to the above-mentioned structure, the present invention gives timing for generating a pulse voltage to the transmission circuit by the transmission timing signal generated by the timing circuit, and the P/L/Sumi 1 pressure is applied to the transducer of the probe. . The vibrator excited by the pulse voltage transmits ultrasonic waves into the living body, and echo signals reflected from the living body from a depth corresponding to the propagation time of the ultrasonic waves reach the probe. The echo signal is converted into an electrical signal by the probe,
After being appropriately amplified by the amplifier circuit, it is applied to the phase detector.

The phase detector performs orthogonal detection of the echo signal using the orthogonal reference signal and outputs the result. A signal whose average value is the phase difference voltage between the orthogonal reference signal and the echo signal is obtained from the detection output obtained by orthogonal detection by the phase detector, and each is integrated by an integrating circuit. The interval of integration is determined by the integration gate signal of the timing circuit,
The time based on the transmission timing signal and the time width for integration are given. After integration, the sum total within the integration interval of the phase difference voltage is output. When the output of the integrator circuit reaches saturation, the comparator sends a status signal to the control circuit. If a large number of saturation conditions occur in the control circuit, the user can take appropriate measures such as lowering the gain by issuing a warning on a display or the like. In addition to issuing a warning, control such as automatically lowering the gain or increasing the time constant of the integrating circuit can be performed.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an ultrasonic pulse Doppler blood flow meter in one embodiment of the present invention. In Fig. 1, 1 is a probe that transmits and receives ultrasonic pulses to and from a living body, 2 is a transmitter circuit that generates a driving voltage for the probe 1 to generate ultrasonic waves, and 3 is a transmitter circuit that generates pulses from the transmitter circuit 2. 4 is an amplifier circuit that amplifies the received signal obtained by the probe 1; 6 is an amplifier circuit 4 that provides a trigger to generate a voltage;
A reference signal generation circuit 6 generates a quadrature reference signal for phase detection of the received signal amplified by the reference signal generation circuit 6, and a reference signal generation circuit 6 detects the quadrature phase of the echo signal amplified by the amplifier circuit 4 using the quadrature reference signal of the reference signal generation circuit 6. 1 is a phase detector; 7 is an integration circuit that integrates the orthogonal phase signal phase-detected by the phase detector 6 over the interval in which the timing signal of the timing circuit 3 is generated; 8 is a sample hold circuit that holds the integration result of the integration circuit 7;
0 is a comparator circuit that detects the saturation state of the real part cuff 1x1 imaginary part output cuff 17 of the integrating circuit 7; 9 is the transmitting circuit 2;
This is a control circuit that controls the amplifier circuit 4, the integration circuit 7, display means (not shown), and the like.

The details of the comparator circuit 10 will be explained with reference to FIG. 2. 111 and 112 are the actual component cuffs 1x of the integrating circuit 7, the absolute value circuits that convert the voltage of the imaginary part cuff 17 into absolute values, and 113 and 114 are the a voltage comparator 115 that compares the threshold voltage E and the voltages of the absolute value circuits 111 and 112;
116 is an OR gate that adds the respective outputs of the voltage comparators 113 and 114; 117 is a low-pass filter that calculates the average voltage of the pulse train emitted from the OR gate 116; 118 is a DC power supply that sets a threshold voltage; 1 is a voltage comparator that compares the average voltage obtained by the low-pass filter 117 with a threshold value, 119 is a DC power supply that sets the threshold voltage, and the status signal output 101 of the voltage comparator 118 is as shown in FIG. It is connected to the control circuit 9.

Next, the operation of the above embodiment will be explained. The timing circuit 3 generates a transmission timing signal 31, an integrating circuit gate signal 32, and a reset signal 33 for the integrating circuit 7. The transmission timing signal 31 is the trigger input 2 of the transmission circuit 2.
1 to generate a pulse voltage, and the pulse voltage generated by the trigger is applied to the drive output 23 and the probe 1.
oscillator. The vibrator is generally made of piezoelectric material,
The vibrator excited by the pulse voltage transmits ultrasonic waves into the living body, and echo signals reflected from the living body from a depth corresponding to the propagation time of the ultrasonic waves reach the probe 1 . The echo signal is converted into an electric signal by the probe 1, moderately amplified by the amplifier circuit 4, and then applied to the phase detector 6. In the phase detector 6, the echo signal applied to the echo signal input 61 is orthogonally detected using the orthogonal reference signals of the real part input 62X and imaginary part input 627 of the reference signal generation circuit 5, and the real part outputs 63X, 63
Output to Y. A signal whose average value is the phase difference voltage between the orthogonal reference signal and the echo signal is obtained from the detection outputs 63 Integrate each.

The integration period is determined by the integration gate signal 32 of the timing circuit 3, and is given the time based on the transmission timing signal 31 and the time width for integration. After integration, integrate ratio cuff 1x.

At 717, the sum of the quadrature phase difference voltages within the integral interval appears. The comparator circuit 10 detects the saturated state of the total voltage of the orthogonal phase difference voltages appearing on the real output cuff 1X and the imaginary part quantity cuff 17, and the comparator circuit 1o detects the real output cuff 1X.
The control circuit 9 is informed that the imaginary part amount cuff 1y is saturated. The control circuit 9 warns the user of the saturation state through a display means (not shown) such as a television screen or pilot lamp, and takes measures such as lowering the gain of the amplifier circuit 4 or increasing the time constant of the integrating circuit 7. Request appropriate treatment selectively or in combination. Further, when the saturation state is reached, the control circuit 9 can automatically perform the above-mentioned measures.

However, since saturation occurs even when strong blood flow is captured, it is especially important to ignore the saturation caused by blood flow when controlling automatically, otherwise the orthogonal Doppler shift will be output normally. This will actually worsen the signal. Therefore, the comparator circuit 10 outputs a state output of 1o only when many saturation states occur within a unit time.
1 is transmitted to the control circuit e to control the time constants, etc. of the amplifier circuit 4 and the integration circuit 7. To explain in more detail the operation of the comparator circuit 10 with respect to the control circuit e, first, in FIG. When a strong blood flow is captured, the output waveform of the integrating circuit 7 is an integral waveform T shown in FIG.

If a stationary part is captured, the integral waveform T2 shown in FIG. 3 will be obtained. Integral waveform T1. T2
In either case, the absolute value circuit 111,1 shown in FIG.
12, and voltage comparators 113 and 114 detect signals exceeding the threshold voltage E.

The outputs of the voltage comparators 113 and 114 are K such as C1 and C2 for T, , and T2, respectively. The average voltage of the signals C, , C2 is passed through a low-pass filter 17 to obtain the average voltage shown by the broken line. Therefore, the threshold voltage is appropriately set by the DC power supply 119 and compared with the average voltage of C+IC2, and if saturation is high, the voltage comparator 118 transmits a status signal to the control circuit 9 from the output 101.

On the other hand, in the sample hold circuit 8, the integral ratio cuff 1
, 717 is held immediately after the integration, the real part is output as the output X and the imaginary part is output as the output Y as an orthogonal signal. After holding, the integrating circuit 7 is reset by the reset signal 33.

Effects of the Invention In summary, the present invention provides a probe that transmits and receives ultrasonic pulses, a transmitter circuit that drives the probe, a timing circuit that provides a timing signal for generating a pulse voltage to the transmitter circuit, and a timing circuit that provides a timing signal for generating a pulse voltage to the transmitter circuit. a reference signal generation circuit that generates an orthogonal reference signal in synchronization with a timing signal from the circuit;
an amplifier circuit that amplifies the echo signal received by the probe; a phase detector that detects the quadrature phase of the echo signal amplified by the amplifier circuit using the quadrature reference signal; We provide an ultrasonic pulse Doppler blood flow meter that is fully equipped with an integrating circuit that integrates in synchronization with a timing signal, and a comparator that detects that this integrating circuit is in a saturated state and outputs a status signal. A comparator detects that the output of the signal is in a saturated state, and in accordance with the detection signal of this comparator, control is performed to issue a warning, control the gain of the amplifier circuit, and control the time constant of the integration circuit, thereby eliminating the possibility of missing Doppler shift signals. It is possible to prevent discontinuities in the frequency analysis results that may occur, which is highly effective in terms of diagnosis.

[Brief explanation of drawings]

1 to 3 show an embodiment of the ultrasonic pulsed Doppler blood flow meter of the present invention, FIG. 1 is a block diagram, FIG. 2 is a block diagram of a comparator circuit, and FIGS. 3 a and 3 are outputs thereof. FIG. 4 is a block diagram of a conventional ultrasonic pulse Doppler blood flow meter, and FIGS. 6 and 6C are output waveform diagrams for explaining the operation of the integrating circuit. 1...Probe, 2...Transmission circuit, 3.
...Timing circuit, 4...Amplification circuit,
5... Reference signal generation circuit, 6... Phase detector, 7... Integrating circuit, 8... Sample hold circuit, 9...・Control circuit, 10...
...Comparator circuit. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] A probe that transmits and receives ultrasonic pulses, a transmitter circuit that drives this probe, a timing circuit that provides a timing signal to generate a pulse voltage to this transmitter circuit, and an orthogonal probe that is synchronized with the timing signal from this timing circuit. a reference signal generation circuit that generates a reference signal; an amplifier circuit that amplifies the echo signal received by the probe; and a phase detector that performs orthogonal phase detection of the echo signal amplified by the amplifier circuit using the orthogonal reference signal. , an integrating circuit that integrates the quadrature phase signal of this phase detector in synchronization with the timing signal, a comparator that detects that this integrating circuit is in a saturated state and outputs a state signal, and a state signal of this comparator. 1. An ultrasonic pulse Doppler blood flow meter comprising a control circuit that selectively or in combination performs control for receiving and issuing a warning, controlling the time constant of an integrating circuit, and controlling the gain of an amplifier circuit.