JPS61106136A - Ultrasonic doppler blood stream measuring apparatus - 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 [Technical Field of the Invention] The present invention relates to an ultrasonic Doppler blood flow measurement device that is capable of measuring blood flow velocities over a wide range.

[Technical background of the invention and its problems] Generally, blood pressure measurement is widely used during medical examinations;
If a detailed examination is required, more detailed information may be required, and measurement of blood flow velocity may be required.

Furthermore, measurement of this blood flow velocity is an important factor when diagnosing the heart, for example.

The devices that measure blood flow are generally Doppler devices, which transmit ultrasound waves to a blood flow area, and the frequency of the ultrasound waves that are reflected back from that part shifts depending on the speed of the blood flow. An ultrasonic Doppler blood flow measurement method that uses the effect of blood flow is used.

That is, as shown in FIG. 6, an ultrasonic wave having a frequency of fO is emitted toward a blood vessel 3 from a wave transmitting probe 2 pressed against the body surface 1, and the reflected waves from blood cells within the blood vessel 3 are Receiving probe 4
When received at , the frequency r from the reflected signal is equal to the blood flow velocity V
Doppler shift by
−+−V cosβ. However, C is the speed of sound, and α and β are the angles formed between the blood flow direction of the blood vessel 3 and the wave transmitting or receiving direction of the wave transmitting and wave receiving probes 2 and 4.

When the above transmitting and receiving probes are the same probe, α-β(-〇), and generally speaking, by inserting the condition of /C)fo...(2)
It can be approximated as The Doppler shift frequency is fd (=I'-
f'o), the above equation (2) becomes fd=-2CO3θVf/C (3). From this equation, the blood flow velocity ■ becomes.

In the above-mentioned ultrasonic Doppler blood flow measurement method, when continuous waves are used, resolution in the distance direction cannot be obtained, and reflected signals from blood vessels near the body surface and blood vessels on the deep side are mixed.
To solve this problem, there is an M-sequence modulation method that modulates continuously, but it is inconvenient that two probes are required to transmit and receive waves.

On the other hand, the pulse modulation Doppler method (Pulse ARA method), which transmits pulses, can be performed using the same probe for transmitting and receiving, and a part of the transmitting pulse generation circuit and receiving circuit can be shared with an 8-mode ultrasonic diagnostic device. , currently widely used.

FIG. 7 shows a typical example of a conventional device using the above-mentioned pulse alignment method.

Ultrasonic probe for transmission and reception (ultrasonic transducer) 11
is connected so that a transmission pulse is applied from a transmission pulse generation circuit 12, and the received signal is amplified by a high frequency amplifier 13 and inputted from one input terminal of each of two mixers 14a and 14b.

The two mixers 14a and 14b phase shift the oscillation wave of the carrier frequency fO output from the oscillator 15 using the phase shift circuit 16, and the two mixers 14a and 14b have a phase difference of 90 degrees.
set of orthogonal signals (cos2πfat, 5in2πfot)
is inputted from the other input terminal, and the signals inputted from the one input terminal and the other input terminal are mixed to perform quadrature phase detection.

The oscillation wave of the oscillator 15 is frequency-divided by the same circuit 17, and the frequency dividing circuit 17 outputs a pulse with an ultrasonic pulse repetition frequency fr, and this pulse drives the transmission pulse generation circuit 12. It's under control.

Further, the frequency-divided pulse of the frequency dividing circuit 17 is delayed by a predetermined time from the transmission timing in the delay circuit 18, that is, after the delay time for separating and extracting only the received signal from the target blood vessel part, the divided pulse is divided into one pair. sample hold circuit 19a,
By applying a sampling pulse to 19b, each mixer 14a
, 14b are sampled and held.

This sampled and held signal is passed through a pair of low-pass filters 20a, each having a cutoff frequency fr, /2.

Through 20b, only the Doppler shift frequency components are filtered out. This converted signal is sent to A/D converters 21a and 21b.
The signal is converted into a digitized complex signal by a fast Fourier transform (FFT) circuit 22, where frequency analysis is efficiently performed using a high-speed digital Fourier transform. The frequency-analyzed signal is then converted to a digital scan converter (D
SC) 23 is displayed on the television monitor 24. still,
By using the two systems of signals whose phases differ by 90', they can be input to the real and imaginary axes of the FFT circuit 22 to perform frequency analysis and separate detection of the forward and reverse Doppler shifts (that is, the blood flow direction). It's Nishide.

The operation of the conventional example configured in this way will be described below.

A high frequency wave with a carrier frequency of f is transmitted from the transmission pulse generation circuit 12 at a period of 1/f with a repetition frequency of fr.
r is applied to the probe 11, and a transmission pulse shown in FIG. 8 is emitted.

The frequency spectrum in this case is shown in Figure 9 (a> and <1
)), there is a component whose center frequency is carrier frequency t'o and a component whose center frequency is the repetition frequency fr on both sides, that is, fq+nfr ('n=1.2...
).

When this transmitted pulse is reflected by a moving object, that is, a blood cell with a velocity V in a blood vessel, the frequency spectrum of the reflected signal is equal to the spectral component of any transmitted pulse.
(=fO+nfr, n==o, i.

2 (here, η is a smaller value of n, and both are symbolically equivalent), where fo given by the above-mentioned equation (2) is replaced with fη. ). Therefore, the Doppler shift frequency fηd (=f−
fη) becomes fn d ”'# ” V ” f Tl, which corresponds to the above-mentioned equation (3),
As shown in FIG. 9(C), each transmission pulse spectrum is shifted from each transmission pulse spectrum indicated by a broken line to a frequency position indicated by a solid line. Therefore, the spectral component in the Doppler-shifted reflected signal is expressed as f=(fo+fdo)(1±n)O...(5), where n=o, where fdo is the Doppler shift with respect to 0. 1.2...

The reflected signal having the Doppler shift component is received by the ultrasonic probe 11 and converted into an electrical signal, and the high-frequency amplifier 1
After being amplified by 3, mixer 14a.

14b, the oscillation wave of the frequency of the oscillator 15 is mixed with the local oscillation output, which is phase-shifted, and converted into a sum frequency and a difference frequency component. A difference signal between these signals is taken out, and sample and hold circuits 19a and 19b to which a sampling pulse that has passed through a delay circuit 18 is applied,
Only the reflected signals of the targeted blood vessel portion are captured. This captured signal is passed through low-pass filters 20a and 20b with a cutoff frequency of f r/2, and is converted to the original spectrum frequency t', as shown in FIG. 9(C).

This is equivalent to passing through a bandpass filter having a band of ±f r/2 centered at , and only the Doppler shift frequency fdo with respect to the spectral frequency fo is detected.

In reality, the Doppler shift detected due to sample-holding includes not only fdlo but also other Doppler components dη as shown in FIG. Although the notation in Figure 9 is not precise, the following explanation also uses the spectrum component element d.
Since there is no problem in focusing only on o, a schematic notation as shown in FIG. 9 is used to simplify the explanation.

In the above conventional device, the cutoff frequency is "l-/2
The purpose of using the low filters 20a and 20b is to prevent the Doppler shift of adjacent spectral components from flooding in. Therefore, the cutoff frequency is the blood flow velocity V IHay at which the Doppler shift of fI-72 or more occurs, that is, In equation (4), fd' = ±f "/2 is substituted, that is, V vrax = ±-" L-1・mountain 4 cos θ f.

is the maximum blood flow velocity that can be measured with the conventional device using the pulse-array method, and there is a drawback that blood flow velocity beyond this cannot be measured.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and the present invention provides an ultrasonic wave that can detect large blood flow velocities without the maximum detectable blood flow velocity being limited by the repetition frequency fr of the ultrasonic pulses. The purpose of the present invention is to provide a Doppler blood flow measuring device.

[Summary of the Invention] The present invention provides a feedback loop that forms a tracking filter whose virtual center frequency changes by following the Doppler shift of a received ultrasound signal, and detects and displays the frequency shift of the signal through this tracking filter. With this configuration, even large blood flow velocities can be detected without being restricted by the Doppler shift amount (width).

[Embodiments of the invention] Hereinafter, the present invention will be specifically described with reference to the drawings.

1 and 2 relate to a first embodiment of the present invention, FIG. 1 shows the main part of the configuration of the first embodiment, and FIG. 2 shows a tracking filter as the main part in the first embodiment. FIG. 3 is a diagram for explaining the operation.

A high frequency wave with a center frequency of f is generated from a transmission pulse generation circuit (not shown) at a cycle of 1/f with a repetition frequency of fr.
A pulse of r is applied to the ultrasonic probe, and the ultrasonic transmission pulse shown in FIG. 8 described above is emitted toward the object.

The reflected (ultrasonic) signal received by the probe and converted into an electrical signal is amplified by a high frequency amplification circuit, and is then amplified by a first pair of mixers 34a and 3 which constitute a tracking filter.
4b is input to one input end. These mixers 34a
.

34b, the frequency fOIJt of the output signal of the voltage controlled oscillator (VCO) 35 is shifted by 90 degrees from each other by a phase shift circuit 36.
A pair of orthogonal signals having a phase difference of ' are input from the other input terminal, and these input signals are mixed (first
(detection) and output. The difference signals in these first detected signals are processed by a pair of sample and hold circuits 39, respectively.
a, 39b. Similarly to the conventional device described above, the signals input to the sample and hold circuits 39a and 39b are obtained by dividing the oscillation wave of the frequency fO by a frequency dividing circuit, and then passing it through a delay circuit for each period of 1/f r. Samples and holds are performed using sampling pulses applied to sample hold circuits 39a and 39b. This sampled and held signal is filtered by low-pass filters 40a and 40b, and applied to one input terminal of each of the second pair of mixers 41a and 41b.

Note that the filters 1 to 1 of these low-pass filters 40a and 40b
The off frequency may be f r /2 or even narrower. The pair of mixers 41a and 41b is a local oscillator 42
The oscillation waves of a relatively low frequency f1 (for example, several times to several tens of times as much as fr) outputted from the phase circuit 43 pass through the phase circuit 43, and orthogonal signals having a phase difference of 90' from each other are sent to the other input terminal. is applied to These mixers 4
The mixed outputs of 18.41b are added by an adder 44 and then input to a "frequency/' lightning voltage F'/V" converter 45. When a signal with a frequency of fx is input, the conversion coefficient is changed to 9. As a result, a voltage output of E=Q (fx-fl) is output from the F/V converter 45.

The output of the F/V converter 45 is sent to the display device and also passes through the low-pass filter 46 to the VCO 35.
The output frequency f 0Llt is variably controlled by the voltage level applied to this input terminal. In the first embodiment configured in this way, the frequency of the VCO 35 is varied to follow the deviation of the Doppler signal, and at the same time, the center frequency of the filter functions as a tracking filter that follows the Doppler deviation.
Its characteristic feature is that a feedback loop is formed.

The operation of the first embodiment configured in this way will be described below.

Now, let the component of the received high frequency signal be the above-mentioned formula (5) (% formula % (o/fo)), and the output frequency of the VCO 35 is fO + △
f, the difference component of the signals mixed by the pair of mixers 34a and 34b is fdo−Δf±nfr (1+(f
do/fo )). (Although not shown, the mixer 3
It is assumed that a low-pass filter for high frequency removal is incorporated in the output side of 4a and 34b, and the sum component is not considered. fd
o−Δf). (As mentioned above, we omit the spread of the spectrum caused by the sample hole.) This signal and the orthogonal signal of frequency f1 are
are mixed in a pair of mixers 41a and 41b, and an adder 44.
When added, the frequency component becomes f1+ (fd o−Δf)
becomes.

This signal has an output voltage E for an input signal with a frequency fx.
indicates the input/output characteristics such that Q (fx-t'1)
The converter 45 converts 0(f1+(fdO-Δf)-f
l)=g(fdo-Δf). This signal is converted into fO+h (Q (fd o-
It is converted into a signal with a frequency of Δf)). By the way, since the initial frequency of the VCO 35 was f, +Δf, by configuring a feedback loop, the output frequency of the VCO 35 is adjusted to satisfy fO+h (Cl (fdo-△f))=fO+8f. Or the 8th f locks. In other words, 8f=-301-fd.

1+gh It becomes locked to .

In the above equation, the conversion coefficient q of the F/V converter 45 and the VCO
If the product gh of 35 conversion coefficients is sufficiently large, Δf=fd.

It can be seen that the oscillation frequency of the VCO 35 approximately follows the Doppler shift of one spectrum component of the original received signal.

As mentioned above, the oscillation frequency of the VCO 35 also shifts with the amount of deviation of the Doppler shift frequency fdO applied to the received ultrasound signal, so the output frequency f of the first pair of mixers 34a and 34b, is fwlax=fdO−Δf=l f,.

1+gh, and it can be seen that the low-pass filters Oa and 40b can have very narrow bands. In reality, the blood flow velocity itself has a distribution, and as mentioned above, the spectrum is broadened by performing signal hold, so the cutoff frequency of the low-pass filters 40a and 4-Ob is f r
An appropriate value should be selected within /2. In addition, when considering the filter characteristics that constitute a feedback loop that is mixed with the VCO output that follows the Doppler shift and then passed through a low-pass filter in this way, when it is returned to the original high frequency region, it is equivalently shown in Figure 2. This is the same as applying a bandpass filter centered on the CO frequency.

That is, as shown in FIG. 2(a), when the reflected signal is Doppler-shifted by fdO to the spectrum of the transmitted pulse shown by the broken line and becomes the spectrum shown by the solid line, the feedback loop in the first embodiment causes the Vco output to The frequency changes to follow the Doppler shift ifdo. Even if this Doppler shift Φfdo is small as shown in FIG. 5(a) or large as shown in FIG. 2(b), it changes to follow the amount of change. In other words, the center frequency of the filter is located at a spectral position that is almost Doppler shifted (
Therefore, even if the Doppler shift maximum exceeds f r/2, adjacent spectral components (at J3 in the conventional example) will not be mixed in, and the pulse in the conventional pulsed Doppler apparatus will be locked. Repetition frequency (
This PR
Blood flow velocity can be detected without being affected by F. Filters that function in this manner are generally called tracking filters.

In the first embodiment configured and operated in this way, the output of the F/V converter 45 directly corresponds to the average frequency of the Doppler shift, so it is sufficient to display the time change of this voltage on a CRT or the like. Note that the voltage passed through the second U-bus filter 46 may be displayed on a CRT or the like.

3 and 4 relate to a second embodiment of the present invention, FIG. 3 shows the main part of the second embodiment, and FIG. 4 is for explaining its operation.

Incidentally, the same elements as in the first embodiment are given the same reference numerals, and their explanation will be omitted.

Each output signal of the pair of low-pass filters 40a, 40b is further applied to one input terminal of each of a third pair of mixers 51a, 51b, and to the other input terminal of each of these mixers 51a, 5.1b. The output signal of the VCO 35 is applied with a phase-shifted signal having a phase difference of 90'' from each other in the phase shift circuit 36, and the two applied signals are mixed and sent to the second adder 5.
It is set to output to 2. The addition output of this adder 52 is further applied to one input terminal of each of a fourth pair of mixers 53a and 53b. However, these mixers 53a
, 53b, a quadrature signal obtained by converting a signal of frequency f generated by the local oscillator 54 into a signal with a phase difference of 90° by the phase shift circuit 55 is applied to each of the other input terminals of the two input terminals. The respective applied signals are mixed and outputted as signals having the sum and difference frequencies. Each signal output from each mixer 53a, 53b is passed through a low-pass filter 57a, 57b (for example, the cutoff frequency is sufficiently lower than fo and sufficiently higher than the repetition frequency fr) that removes high frequency components, and then The orthogonal signal of frequency fdO is converted into a complex digital signal by a pair of A/D converters 58a and 58b, and is input to an FFT circuit 59.

The signal subjected to frequency analysis by the FF7 circuit 59 is DS
The image is displayed on the television monitor 61 via C60. Note that when blood flow is not measured, a B-mode signal is input to the DSC 60 so that an ultrasonic tomographic image can be displayed on the television monitor 61.

This second embodiment is designed so that the blood flow measurement range is not restricted by the tracking filter function of the first embodiment, and also enables display of forward and reverse separation of frequency analysis and Doppler shift as in the conventional example. There is, and its operation will be explained below. (A description of the operation of the same parts as in the first embodiment will be omitted.) As explained in the first embodiment above, the reflected wave signal (
The frequency component of the received RF multiplied signal is fo+fdo±nfr
(1-fdo/fo), the output frequency f of the VCO 35, and +△f, a pair of low-pass filters 40a
, 40b becomes fdo-Δf. This signal is converted to V by a third pair of mixers 51a, 51b.
It is mixed with the frequency component of CO35 and quadrature phase modulated,
It is added by the second W adder 52. This addition output is 90'
After being mixed with the orthogonal signal of frequency t'o having a phase difference of 58a and 58b, the signal is converted into a complex digital signal, subjected to frequency analysis and forward/reverse separation of Doppler shift in an FFT circuit 59, and displayed on a television monitor 61 via 08C60.

Note that since a feedback loop functioning as a tracking filter is formed, even if the Doppler shift IfdO exceeds 1/2 of the pulse repetition frequency fr, adjacent spectrum components do not mix.

The above operation can be explained mathematically as follows. still,
To simplify the notation, the angular frequency ω (=2πf) is used.

As shown in Fig. 4(a), the angular frequency spectrum of the transmitted pulse before undergoing Doppler shift is an (n=0
．． ±1. ±2...), and as a result of the Doppler shift caused by the blood flow, it becomes ωn- as shown in FIG. 2(b). However, ωn=ω0−tnωr, and ωη′=(
ω0+ωdo)(Lln(ωr/ωo)).

Further, the angular frequency of the VCO 35 is assumed to be ωV. Now, if the received signal is S(↑), it is expressed as 5(t)=Σ(a71sinωn−I).

If the outputs of the first pair of mixers 34a and 34b are respectively Mt (t>, M2 (t>), then Ml(t)
=S (t> ・cos oov t= (1/2)Σ
(an 5in(ωn′ −ω Vat −to s
in (ω η ′+ωVat) M2 (t)=S (t) −5inωv t= (
1/2)-Σ(an cos(an8'ωv)t-cos(ωη-+ωv)t). When these Ml (t) and M2 (t) are passed through low-pass filters 40a and 40b, respectively, FIG.
), only the term (ω0′-ωV) remains, and Ml
(t), M2 (t) are respectively Ml (t>=(1
/2) ao 5in(ωo'-ωv)t M2 (t)=(1/2>ao cos(ωo--
ωv)t. Dl (t)D2
(t) then D+ (t)=Mt (t) −cosωv t=
(1/4)aQ (sinωo-t-5in (
2(Z)V-ωo-)t)D2 (t) =M2
(t) −5in ωv t= (1/4)ao (s
inωo-t+sin (2ωv-ωo-)t), and when added by the second adder 52, Dl (t)+
Dz(t)=(1/2)a.

sinωo′t, and finally ω0 as shown by the solid line in Figure 4(d).
Only the - term remains, and other adjacent spectra included in the original signal 5(t) disappear.

After this, substantially the same processing as in FIG. 7 is performed. In other words, quadrature phase detection is performed at frequency t'o using a fourth pair of mixers 53a and 53b, and input to the FFT circuit 59 through the Doppler shift components using low-pass filters 57a and 57b, where the frequency is analyzed and the forward and reverse directions of the Doppler shift are performed. Separation is performed and displayed on the television monitor 61.

The above explanation deals with the case where the spectrum subjected to Doppler shift does not have a spread, but even if each spectrum has a spread due to blood velocity distribution, etc., the spectrum included within the band of the tracking filter is as shown in Figure 4. It is obvious that it is restored to exactly the same shape as shown by the broken line J in (d).

Furthermore, since the Doppler signal from within the living body generally includes a crank component (reflection component from an unmoving object), the followability of the tracking filter is improved by using a rutter removal filter 71 as shown in FIG. 5(a). be able to. Here, reference numeral 72 is a delay line with a delay time τ of 1/f i-, and a subtracter 73 subtracts the signal passed through this delay line 72 from the signal that does not pass, thereby outputting a difference signal between them. By doing so, the same figure (b
), a comb filter having a NULL point for each frequency fr can be constructed. The clutter removal filter 71 shown in FIG. 5 is used before the circuit of the first embodiment shown in FIG. 1 or the second embodiment shown in FIG. (Installed immediately before or before the high-frequency amplification circuit. In this case, the S/N ratio is generally better if the amplification is performed after the high-frequency amplification circuit has been amplified.) Also, when sample-holding is performed using the sample-hold circuits 39a and 39b, may be installed before this stage.

In addition, in FIGS. 1 and 3, the sample and hold circuits 39a and 39b are not used, and a two-dimensional Doppler tomographic image is extracted by making the tracking filter track the received signal in real time. It can also be applied to other things.

Also, when using a sample-and-hold circuit, as the sampling pulse for sample-and-holding, the distance between the delay sections is gradually increased from a small one through a variable delay means.
A two-dimensional Doppler tomographic image is obtained by calculating the Doppler shift amount in real time, performing this process for each scanning direction, and displaying the brightness etc. corresponding to the Doppler shift amount on the B-mode scanning line. You can also have them draw it.

Note that the Doppler shift frequency detection circuit system or display circuit system after the second adder 52 in FIG. 3 is not limited to that shown in the figure; for example, the center frequency is
An FM detection circuit set to o can be used.

[Effects of the Invention] As described above, according to the present invention, a feedback loop is formed that functions as a tracking filter whose filter center frequency changes in accordance with the frequency shift caused by the Doppler effect, so that the detection in the conventional example is The maximum possible blood flow velocity constraint is N, 8! i can handle high blood flow speeds.

Furthermore, by using a tracking filter, the blood flow distribution can always be displayed while being locked to the center of the filter.

Furthermore, a two-dimensional Doppler tomographic image can also be displayed.

[Brief explanation of drawings]

1 and 2 relate to a first embodiment of the present invention, FIG. 1 is a block diagram showing the configuration of the main part of the first embodiment, FIG. 2 is an explanatory diagram of the operation of the first embodiment, 3 and 4 relate to the second embodiment of the present invention, FIG. 3 is a block diagram showing the configuration of the main part of the second embodiment, FIG. 4 is an explanatory diagram of the operation of the second embodiment, and FIG. 5(a) is a block diagram showing a crack removal filter according to the third embodiment of the present invention, and FIG.
Figure 6 is an explanatory diagram of the Doppler blood flow measurement method, Figure 7 is a block diagram showing the configuration of a conventional example, and Figure 8 is a waveform diagram showing the waveform of the transmitted pulse. , FIG. 9 is an explanatory diagram of the operation of the conventional example, and FIG. 10 is a distribution diagram showing the spread of the Doppler shift spectrum in the conventional example. 34a, 34b - Mixer 35... Voltage controlled oscillator (VCO) 36... Phase shift circuit 39a, 39b... Sample hold circuit 40a, 4
0b...Low pass filter 41a, 41b-.
・i combination z 42... local oscillator 43... phase shift circuit 44...
Adder 45...Frequency/voltage converter 46...
Low-pass filter 59...Fast Fourier transform circuit 60...Digital scan converter 61...Television monitor agent Patent attorney Susumu Ito' 1.0.
-da Figure 4 10' Figure 5 Figure 6 Figure 7 Figure 9 Figure 10 Procedure Ne 10 Official document (spontaneous) October 23, 1985 1゜Indication of incident 1988 Patent Application No. 227275
No. 2, Title of the invention Ultrasonic Doppler blood flow measuring device 3,
Relationship with the case of the person making the amendment Representative of the patent applicant Satoshi Shimoyama Dept. 5, Attachment of amendment order (self-motivated) , SθV f
/C...(3)] is rfd==-2CO3θ
Vfo /C... (3) Correct to 1. 2. In lines 18 to 20 of page 8 of the specification, "...Frequency analysis... will be carried out...1" should be replaced with "...Frequency analysis will be carried out..."・Corrected to ``. 3. In the 9th line to the 12th line of the 9th page of the specification, the phrase ``Transmission pulse... is emitted.'' is replaced with ``The transmission pulse is transmitted from the transmission pulse generation circuit 12 every period 1/[r. A pulse is applied to the probe 11 at a carrier frequency f, not shown in FIG.
An ultrasonic pulse of O is emitted. ” will be corrected. 4. In the 8th line of page 10 in the specification, 5-" and -
10 ■ Φf TI J ``fηd=-2CO3θ is corrected to ``fηd=-2CO3θfη/Cl.'' 5. In the 13th line of page 10 of the specification, ``...Doppler... " will be corrected to "...Doppler...". 6. I will correct the statement on page 10, line 14 of the statement. 7. In the 10th line of page 11 of the specification, it says "...filter 20a...shown in FIG. 9(C)".
...filtered by filters 20a and 20b. This is the 9th
Please correct it to "shown in Figure (C)". 8. On the 19th and 20th lines of page 11 in the specification, there is a 1...spread...The notation in Figure 9 is...''
The statement has been corrected to ``...the spread has occurred, and the notation in Figure 9 (C) is...''. 9. In the second and third lines of page 12 of the specification, [...in Figure 9...] is replaced with "... in Figure 9 (
Correct it to "C)...". 10. On the fifth line of page 12 of the Middle East specification, the text [...low filter...] will be corrected to [...low pass filter...]. 11. In the 7th and 8th lines of page 12 of the specification, [Therefore...Doppler shift...] is replaced with [Therefore, Doppler shift of fr/2...] "Corrected to 1゜12,
In the 14th line of page 18 of the specification, "...frequency ftIax" is replaced by [...frequency f' min
I will correct it to ``. 13. rfax on page 18, line 15 in the specification
Correct "=-..." to "fmin=...". 14. Lines 16 to 1 of page 21 in the specification
In the 8th line, correct the statement "...for example...larger..." to "...however, the cutoff frequency is sufficiently larger than fr/z...". 15. In the 17th line of the 22nd page of the specification, "Frequency fO+..." is replaced with "Frequency: 0(-...")
I will correct it. 16, Akira I [[R = (1/2) % (ansin (ωn'-ω
V) t+sin (ωη ′′−ωv)t) j is r= (1/2) stone (an (sin (ωn′～ω
v) t+sin (ωη′ +ωv)t)) Correct it to j. 17. Lines 16 to 1 of page 24 in the specification
In the 8th line, r = (1/2> 1. (ancos (ωn'-ω
V) t+cos (ωη′ −t ω v) t)
J [= (1/2) % (an (cos (ωη′−
ωv) t+cos (ωη−+ω■)t〉 )
” will be corrected. 18. Delete "Also, samples..." from lines 11h [] to 13th on page 27 of the specification. 19. Delete "Also, sample hold...can be done." in the 6th line of page 27 to 6th line of page 28 of the 1Jm book.

Claims (6)

[Claims] (1) In an ultrasonic Doppler blood flow measurement device that transmits ultrasonic pulses into a living body at a constant repetition frequency and detects the blood flow velocity in the living body from the frequency deviation of the received reflected ultrasound signal, A tracking filter whose virtual center frequency changes in accordance with changes in the Doppler shift of the sound wave signal is provided, thereby forming means for detecting the amount of frequency shift of the reflected ultrasound signal through the tracking filter. Ultrasonic Doppler blood flow measuring device. (2) The tracking filters are 90 degrees in phase with each other.
° A voltage controlled oscillator that generates a set of different orthogonal signals, a first mixer pair that mixes the output signal of this voltage controlled oscillator and a received high frequency signal, and an ultrasonic pulse that transmits the output of this mixer pair. A pair of sample and hold circuits that sample and hold in synchronization with the repetition period of , a first pair of low-pass filters that filter the output of this pair of sample and hold circuits, and a pair of orthogonal a fixed frequency local oscillator for generating a signal; a second mixer pair for mixing the output of the local oscillator with the output of the first pair of low-pass filters; and summing the outputs of the second mixer pair. an adder;
A frequency/voltage converter converts the average frequency of the output of the adder into a voltage, and the output frequency of the voltage controlled oscillator is adjusted by filtering the output of the frequency/voltage converter and applying it to the voltage controlled oscillator. and a second low-pass filter that controls the first low-pass filter.
The ultrasonic Doppler blood flow measuring device described in 2. (3) Ultrasonic Doppler blood flow measurement according to claim 2, wherein the frequency/voltage converter displays a temporal change in its output voltage as a blood flow velocity change on a display means. Device. (4) The detection means between the frequency deviations are arranged so that the phases thereof are 90 degrees relative to each other.
a voltage controlled oscillator that generates a set of orthogonal signals that differ by 0°;
A first mixer pair that mixes the output signal of this voltage controlled oscillator and the received high frequency signal, and a pair of sample and hold circuits that sample and hold the output of this mixer pair in synchronization with the repetition period of the transmitted ultrasonic pulse. a first pair of low-pass filters that filter the outputs of the pair of sample-and-hold circuits; a fixed-frequency local oscillator that generates a set of orthogonal signals whose phases differ by 90 degrees from each other; and an output of the local oscillator. a second mixer pair that mixes the outputs of the first pair of low-pass filters; a first adder that adds the outputs of the second mixer pair; and an average frequency of the output of the adder. a tracking filter comprising a frequency/voltage converter that converts the frequency to a voltage; and a second low-pass filter that filters the output of the frequency/voltage converter and applies the filtered voltage to the voltage controlled oscillator; a third mixer pair for remixing the output of the low-pass filter pair with the output of the voltage controlled oscillator; a second adder for summing the outputs of this third mixer pair; 2. The ultrasonic Doppler blood flow measurement device according to claim 1, further comprising frequency detection means for detecting a frequency change in the output of the adder. (5) The frequency detection means have phases different from each other by 90 degrees.
a second local oscillator for generating a set of orthogonal signals, and a fourth for mixing the output of this local oscillator with the output of said second adder.
a pair of mixers, a third pair of low-pass filters that filter the output of the fourth pair of mixers, and a fast Fourier transformer (FFT) that calculates a frequency spectrum using the output of the pair of low-pass filters as a complex signal input. ) The ultrasonic Doppler blood flow measuring device according to claim 4, characterized in that it is constructed by: (6) The ultrasonic Doppler blood flow measuring device according to claim 1, wherein the tracking filter is provided with a comb-shaped filter for removing clutter signals at a preceding stage thereof.