JPH02203849A - Pulsed Doppler measurement device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a pulse 1 method for detecting the velocity of an object using ultrasonic waves.
Kubla Meter A (11 Device 1 “Regarding darkness, especially +r in the living body
+ I'm interested in a device that calculates points in real time.

[Conventional technology]

Various devices are known for determining the flow velocity of an object using the Doppler effect of sound waves. In particular, in a device that uses the pulsed Doppler method (for example, see the H-book? [1 'Journal of the Japanese Society of Sound Engineers, Vol. Con old +0118
Wave) is repeatedly transmitted, and the received wave 4r4 receives I1?1(
distance to 11 parts), 5 L, time game 1-
It is known that it is possible to identify the measurement site by applying .

[Problem to be solved by the invention]

If the transmission interval of ultrasonic pulses is l' (see), the range of l' bra frequencies that can be measured with conventional pulsed Doppler measuring devices is ±1. / 2 T(HZ).

For example, when 'l' = 250 μsec, ±2 K
Hy, it is. For example, 2. bKH
z I ~ Bra frequency is −1, b
K Hy.

It is incorrectly set to 81. When considering the direction of direct current, the direction of blood flow with a positive Doppler frequency is called the forward direction, and the direction of blood flow with a negative Doppler frequency is called the opposite direction.If the blood flow is in the forward direction and has a high velocity, it is in the opposite direction. The blood flow and the table will be >J<.

The purpose of the present invention is to reduce erroneous measurements of blood flow direction by correcting the Doppler frequency determined by the conventional method.In particular, in Doppler analysis, it is possible to detect Doppler frequency fluctuations without aliasing. That is.

[#Means to solve the problem]

The above object of the present invention is to receive ultrasonic pulses reflected by an object, detect the phase difference of the ultrasonic pulses, add and average the phase differences or phase difference vectors, and then calculate the average phase difference (angle). By dividing by the time just before the transmission of the ultrasonic pulse to find the frequency fluctuation, ^ "Means for approximating the phase difference carbonization curve of the average phase difference to a broken line in the pulsed Doppler meter 8111 device that calculates the velocity of the recorded object, 2π to the approximate curve
Approximate broken line 41 by adding or subtracting multiples of
A pulse Doppler measurement device (t achieved by

[Operation] In the present invention, a retardation carbonization curve is approximated by a 4Jr line, a group of approximated lines is obtained by adding or subtracting a multiple of 2π from the approximated line, and then a line with no repetition is obtained from the group of approximated lines. Select one from multiple candidates.

This allows measurement without aliasing in Doppler analysis. Finally, a retardation carbonization curve corresponding to the approximate folded line without folding is generated (1), so the front edge (which reduces errors due to folding) is defined as lIf function.

〔Example〕

Hereinafter, an embodiment of the present invention is shown in Fig. 1. In Fig. 4, 1 is an ultrasonic probe, 2 is a transmitter circuit, 3 is a receiver circuit, and 4 is a・14 comparators, one is A/
1) a transducer, 6 a target object, 1 a speed calculation calculator (folding algorithm 1, ), 8 an operation), 9 a control unit, and 10 a display device.

In the pulsed Doppler apparatus, ultrasonic pulses are repeatedly transmitted every 1' seconds from the wave transmitting circuit 2 to the ultrasonic sensor toward the target object 6. A reflected signal reflected from the target object 6 passes through the ultrasonic sensor 1, is received and amplified by the wave receiving circuit 3, and is input to the phase comparator 4.

The velocity calculation calculator ``1'' is characterized by calculating and detecting the velocity of blood flow, and if the direction is wrong, performing correction [E processing], performing Doppler analysis, and detecting the maximum blood flow velocity.Therefore,
First, in the phase comparator 4, the low frequency output signal is mixed with two reference signals α, α' having a 90° phase difference and low-pass filtered, and then the low frequency output signal is converted into a digital signal in the A/D converter 5. , complex number phase signal ■, speed calculation calculator 7
is man-powered.

Vn=exρ(jen) However, An is the amplitude and On is the phase.

FIG. 3 shows the PAD flowcharts 1 to 1 regarding blood flow velocity in the velocity calculation calculator 'l. An overview of the processing of the speed calculation computer 7 will be explained with reference to FIG.

The M T1 filter in step 1 bypass filters the phase signal and separates the blood flow signal from the low frequency signal due to the movement of the blood vessel wall. In step 2, waves are repeatedly transmitted every J', and the phase j1.・Eighty. is detected, and an 11L average phase difference Δθ1 is obtained within the bucket. Step 3 converts 01 to the average phase difference of the whole interval (and several seconds) to 80 + (i = 1) of a certain small time interval (approximately 5 milliseconds).
, 20), and then approximated by broken lines. Therefore, the variation in Δθ1 for each small section is approximated by a straight line. Find and store the coordinates (time, phase i, etc.) of the approximate curve and the starting and ending points of the straight line.

Figure 2a shows the Doppler analysis waveform of the Doppler valve for about 1 second.The blood flow velocity is fast (large), so it cannot be measured correctly, and it is folded back (the direction and velocity are wrong). For example) 1<L/.

Figure 2 shows an approximate broken line Doppler waveform. In F' ET analysis, the average frequency is used as the original Doppler analysis waveform. The explanation uses short-time analysis Doppler waveforms using the autocorrelation method.

Step 4 generates a group of approximate broken lines by adding or subtracting a multiple of 2π to the obtained straight line.

The process selects a polygon line without a cutting point (folding) from the group of approximate polygon lines. In the approximate broken line group shown in Fig. 2C, the broken line without a cutting point (turnback) is a candidate for No.
, (1) to (12). It can be seen that in the rising portion (section A), there are seven candidates, No., (]) to (7). In the falling part (section B), there are three lines. In the end, the continuous broken lines are No. (3), and are selected in step 5.

Step 6 is to read out the original Doppler waveform data from the memory and restore the phase difference. FIG. 2d is a redundant Doppler waveform group corresponding to the approximate broken line group. FIG. 2e is a predicted diagram of the restored phase difference, that is, the estimated Doppler change waveform, and the aliasing disappears (l).

On the display device hq, 10, each Debuch analysis diagram shown in FIG. In particular, the finger, J (if there is no one, the 6 Doppler analysis diagram in Figure 2a) and the estimated Doppler analysis diagram in Figure 2e are displayed. When it is desired to obtain a table in terms of blood flow velocity, the phase difference is converted into blood flow velocity via the control device i' (9) according to the instructions on the console 8. This conversion is performed using the phase difference Δ & 1 pulse transmission interval This is possible by dividing by .

■=to 8/k T However, k=4π/λ, λ is the wavelength of the transmitted pulse.

At that time, the maximum blood flow velocity V, d8 is simultaneously detected and displayed on the display h'10.

〔Effect of the invention〕

As described above, according to the present invention, an ultrasonic pulse reflected by an object is received, the phase difference of the ultrasonic wave pulse is detected, and the phase difference or the phase difference vector is added and averaged. , in a Vals Dobra measurement device that calculates the speed of the object by dividing the average phase difference (angle) by the transmission interval of ultrasonic pulses to find the frequency fluctuation, the phase difference change curve of the average phase difference is plotted as a polygonal line. means for approximating, means for obtaining a group of approximate broken lines by adding or subtracting a multiple of 2π from the approximate straight line, means for selecting one broken line without folding from a plurality of candidates from the group of approximate broken lines, and a position corresponding to the approximate broken line. Since we have provided a means to reproduce the phase difference change curve,
This has the effect of realizing a pulsed Doppler measuring device that enables display that reduces errors due to aliasing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention, FIG. Approximate broken line group, Figure 2d
is the original Doppler waveform group corresponding to the approximate broken line group, FIG. 2e is a prediction diagram of the estimated Doppler change waveform, and FIG. 3 is a flowchart showing the signal processing method according to the embodiment of the present invention. 1... Ultrasonic probe, 2... Transmission circuit, 3...
Receiving circuit, 4... Phase comparator, b... A/IJ converter, 6... Target object, 'l... Velocity calculation calculator (folding algorithm), 8... Operation console, 9 ...Control unit, 1 (N...Table, 1<Installation (■0) No.

Claims (1)

[Claims] 1. Receive the ultrasonic pulse reflected by an object, detect the phase difference of the ultrasonic pulse, add and average the phase difference or phase difference vector, and then calculate the average phase difference (angle) of the ultrasonic pulse. In a pulsed Doppler measurement device that calculates the speed of the object by dividing by the transmission interval to find the frequency fluctuation, means for approximating the phase difference change curve of the average phase difference as a broken line, adding a multiple of 2π to the approximate straight line, or The apparatus is characterized by comprising means for obtaining a group of approximate broken lines by subtraction, means for selecting one of a plurality of candidates for a broken line without folding from the group of approximate broken lines, and means for reproducing a phase difference change curve corresponding to the approximate broken line. Pulsed Doppler measurement device.