JPH0655210B2 - State quantity measuring device in blood circulation system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a state quantity measuring device in a blood circulation system that non-invasively measures arteriosclerosis, heartbeat, blood flow, and the like.

<Prior Art> Conventionally, as a method of non-invasively measuring arteriosclerosis, as shown in FIG. 5, an oscillation output signal from an oscillator (21) is supplied to a filter (22), an amplifier (23), And the matching circuit (24) to the wave transmitter (25) to transmit the ultrasonic wave of frequency f to the artery wall, and the reflected wave (frequency f + Δf) from the artery wall is received by the wave receiver (26). The received signal is received and the output signal from the receiver (26) is fed to the matching circuit (27), the bandpass filter (28), and the amplifier (2
9) supplied to the mixer (30), mixed with the oscillation output signal supplied from the oscillator (21) via the attenuator (31),
The mixed signal is supplied to the extraction circuit (32) to extract only the Doppler shift component, the calculation circuit (33) performs a predetermined calculation, and the calculation result is supplied to the display device (34) to display the degree of arteriosclerosis. There is a proposal to do so (Japanese Patent Application Laid-Open No. 6-58242).
0-176634).

In addition, in the arteriosclerosis measuring device having the above-mentioned configuration, in order to match the level of the output signal from the wave receiver (26) and the oscillation output signal from the oscillator (21), the attenuation with the amplifier (29) is used. vessel
(31) and the amplification factor and the attenuation factor are set to relatively small predetermined values.

<Problems to be Solved by the Invention> In the arteriosclerosis degree measuring device having the above configuration, the transmitter (2
The ultrasonic output intensity from 5) is kept constant, but the ultrasonic intensity in the receiver (26) fluctuates depending on the attachment angle to the arterial wall, the distance to the arterial wall, etc. The amplitude of the mixed output signal from the mixer (30) varies.

This amplitude fluctuation does not pose any particular problem as long as the processing after the mixer (30) is performed in an analog manner, but in the case of digital processing, the following problems will occur.

That is, since the amplitude of the output signal from the wave receiver (26) fluctuates, it is equivalent to that the signal of frequency f + Δf is amplitude-modulated by the signal of different frequency f ′. Therefore, even if the mixer (30) mixes the oscillation output signal of the frequency f from the oscillator (21) and only the Doppler shift component (frequency | Δf |) is extracted by the extraction circuit (32),
Actually, not only the Doppler shift component (frequency | Δf |) but also the signal (frequency | Δf | ±
f ′) is also extracted, and after A / D conversion, the combined signal of them is grasped as a Doppler shift component. Therefore, the obtained signal includes the attachment angle to the arterial wall, the distance to the arterial wall, etc. The error caused by is included. Therefore, there is a problem that the degree of arteriosclerosis finally obtained becomes inaccurate.

<Objects of the Invention> The present invention has been made in view of the above problems,
An object of the present invention is to provide a state quantity measuring device in a blood circulatory system that can accurately measure the degree of arteriosclerosis, heartbeat, blood flow, etc. by removing the effects of the attachment angle to the arterial wall, the distance to the arterial wall, etc. I am trying.

<Means for Solving Problems> A state quantity measuring device in a blood circulatory system of the present invention for achieving the above object sends an ultrasonic wave to an arterial wall using an oscillation output signal from an oscillator as an input. A wave transmitter,
A receiver for receiving a reflected wave from the arterial wall, a conversion circuit for amplifying an output signal from the receiver with a large amplification factor, and chopping to convert it into a rectangular wave signal, and an oscillation output from the oscillator. It is characterized by comprising a signal and a mixing detector for mixing the rectangular wave signal to extract only the Doppler shift component, and a conversion circuit for converting the Doppler shift component into digital data.

<Operation> With the state quantity measuring device in the blood circulatory system having the above configuration, the ultrasonic wave is transmitted to the arterial wall by supplying the oscillation output signal of the oscillator to the wave transmitter. This ultrasonic wave is reflected by the arterial wall, received by the wave receiver, and outputs a signal having a frequency subjected to Doppler shift. This signal is amplified by the conversion circuit with a larger amplification factor and is converted into a rectangular wave signal by being chopped. By supplying this rectangular wave signal and the oscillation output signal to the mixing detector, the Doppler shift component is obtained. Only the signal is extracted, and then the conversion circuit converts the Doppler shift component into digital data, whereby a signal corresponding to a state quantity such as arteriosclerosis, heartbeat, and blood flow can be obtained.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 3 is a schematic diagram showing a state quantity measuring device in the blood circulatory system of the present invention, in which ultrasonic waves of frequency f are transmitted to the arterial wall (2) by the wave transmitter (1), Frequency f that received the Doppler effect due to the radial movement (pulsation) of the wall (2)
The reflected wave of + Δf is received by the wave receiver (3).

FIG. 4 is a diagram showing a waveform diagram of an ultrasonic signal transmitted from the wave transmitter (1) and a waveform diagram of a reflected wave signal from the arterial wall (2). Δf fluctuates positively and negatively in response to the bulge and contraction (see a and b in FIG. 9B).

FIG. 1 is a block diagram showing an embodiment of a state quantity detecting device for a blood circulatory system, including a hand pass filter (5) and an amplifier.
The oscillation output signal from the oscillator (4) is supplied to the wave transmitter (1) via (6) and the matching circuit (7). The matching circuit (8), bandpass filter (9), and waveform shaping circuit
The output signal from the receiver (3) is sent via the (10) to the mixed detector (1
In addition to being supplied to 1), the oscillation output signal from the oscillator (4) is also supplied to the mixing detector (11). further,
The output signal from this mixing detector (11) is the A / D converter (1
The frequency analysis device (13) is supplied via 2), and the analysis output signal from the frequency analysis device (13) is supplied to the display device (14). However, the frequency analysis device (13) may have a dedicated circuit configuration or a microcomputer having a dedicated program.

The oscillator (4) outputs an oscillation output signal of about 10 MHz, the amplifier (6) has a predetermined amplification factor which is not so large, and the waveform shaping circuit (10)
Is to amplify a signal with a very large amplification factor and generate a rectangular wave by chopping the amplified signal at a predetermined level to eliminate the amplitude change of the signal input to the mixed detector (11). However, the amplitudes of both signals input to the mixed detector (11) are set so that the oscillation output signal from the oscillator (4) becomes significantly larger than that of the rectangular wave.

The mixed waveform in the above case will be described below.

The oscillation output signal from the oscillator (4) and the amplitude of the reflected wave having the Doppler shift component are A and B (A >> B), respectively.
Then, the oscillation output signal from the oscillator (4) can be expressed as A sin (2πft), and the reflected wave can be expressed as B sin {2π (f + Δf) t}.

Therefore, the mixed waveform is A sin (2πft) + B sin {2π (f + Δf) t} = A [1+ (2B / A) cos (2πΔft) + (B / A) ² ] ^1/2 sin ( 2πft + ψ) ≈ A [1+ (2B / A) cos (2πΔft)] ^1/2 sin (2πft + ψ) ≈ A [1+ (B / A) cos (2πΔft)] sin (2πft + ψ) = [A + B cos ( 2πΔft)] sin (2πft + ψ) However, a modification of the above formula is established because (B / A) ² ≈0 and 1 >> 2B / A.

Therefore, by detecting the mixed waveform, B c
os (2πΔft), that is, only the Doppler shift component is detected.

Although the case where both signals are sine waves has been described above, the rectangular wave is a basic sine wave (frequency is f + Δ).
The harmonics of 2 times, 3 times, ... Are superimposed on f), and even if f >> Δf (for example, the signal frequency output from the oscillator (4) is 10 MHz, the Doppler shift component is Since it is several hundreds of Hz), it is possible to extract only the Doppler shift component by applying the above calculation.

The frequency analyzer (13) digitally performs frequency analysis. Specifically, for example, v = (c / 2 cos θ) (Δf / f) (c is the in-vivo sound velocity of about 1500 m). / Sec) to calculate the motion velocity of the arterial wall (2). Furthermore, the matching circuit
(7) and (8) are for impedance matching between the circuit and the wave transmitter (1) and the wave receiver (3).

The operation of the state quantity measuring device in the blood circulatory system having the above configuration will be described with reference to FIG. 2 showing a waveform diagram.

Oscillation output signal of frequency f from the oscillator (4) (Fig. 2A
Is supplied to the transmitter (1) through the bandpass filter (5), the amplifier (6), and the matching circuit (7), the transmitter
An ultrasonic wave of frequency f is transmitted from (1) toward the arterial wall (2). This ultrasonic wave is reflected in a state where it is Doppler-shifted in response to the radial swelling and contraction of the arterial wall (2),
A signal (frequency f + Δf) containing a Doppler shift component is output from the wave receiver (3) and input to the waveform shaping circuit (10) via the matching circuit (8) and the bandpass filter (9). Here, due to the radial swelling and contraction of the arterial wall (2), the wave receiver (3), the mounting angle corresponding to the arterial wall (2), the arterial wall
Since the distance to (2) fluctuates, the reception intensity of the ultrasonic signal in the wave receiver (3) fluctuates, and the state becomes the same as the case where amplitude modulation is performed by a signal of a predetermined frequency (Fig. 2B). reference).

A signal having this amplitude variation is greatly amplified by the waveform shaping circuit (10) and chopped at a predetermined level, so that not only the portion where the amplitude is initially large but also the portion where the amplitude is small is shaped into a rectangular wave ( (See C in FIG. 2). That is, a signal (frequency f + Δf) in which the amplitude variation is completely removed and only the frequency variation due to the Doppler shift component is applied,
And the oscillation output signal (frequency f) from the oscillator (4) is supplied to the mixing detector (11) to extract only the Doppler shift component Δf (see D in FIG. 2), and the A / D converter (12) Converted to digital data. This digital data is supplied to the frequency analysis device (13) for digital analysis processing, and the analysis device result is supplied to the display device (14) to determine the degree of arteriosclerosis, heartbeat, blood flow. It is possible to display the state quantity in the blood circulation system such as.

<Effects of the Invention> As described above, the present invention eliminates the measurement error caused by the intensity change of the ultrasonic signal received by the wave receiver, and accurately measures the state quantity in the blood circulation system. It has the unique effect of being able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a state quantity measuring device in a blood circulatory system of the present invention, FIG. 2 is a signal waveform diagram of each part, and FIG. 3 is a transmitter and a receiver for an arterial wall. FIG. 4 is a schematic diagram showing a positional relationship, FIG. 4 is a signal waveform diagram for explaining Doppler shift, and FIG. 5 is a block diagram showing a conventional example. (1) …… Transmitter, (2) …… Arterial wall, (3) …… Receiver, (4) …… Oscillator, (10) …… Wave shaping circuit, (11) …… Mixed detector , (13) …… Frequency analyzer

Claims (1)

[Claims] 1. A transmitter for transmitting an ultrasonic wave to an arterial wall using an oscillation output signal from an oscillator as an input, a receiver for receiving a reflected wave from the arterial wall, and an output from the receiver. A conversion circuit that amplifies a signal with a large amplification factor and chops it to convert it into a rectangular wave signal, an oscillation output signal from the oscillator, and a mixing detector that mixes the rectangular wave signal and extracts only the Doppler shift component. And a conversion circuit for converting a Doppler shift component into digital data, a state quantity measuring device in a blood circulatory system.