JPS6222637A - Ultrasonic doppler blood flowmeter - 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 Doppler blood flow meter used in the medical field to measure blood flow velocity in a living body.

Conventional technology Ultrasonic Doppler blood flowmeters detect the Doppler shift frequency received by echo signals from moving reflective objects and measure blood flow velocity in living organisms, such as the circulatory system and heart. used in the medical field.

The conventional ultrasonic Doppler blood flow meter will be explained below. Ultrasonic waves are transmitted into the living body by bringing the ultrasound transmitting means into close contact with the surface of the living body and driving the ultrasound transmitting means. The transmitted ultrasound waves are reflected at points with different acoustic impedances, such as tissues and blood cells in the living body, and are received as echo signals by the ultrasound receiving means and converted into electrical signals. (Generally, the ultrasonic transmitting means and the ultrasonic receiving means are housed in the same housing and are configured as one probe.) At this time,
If the echo signal is from a stationary object, the transmitted ultrasonic wave and the reflected echo signal have the same frequency components, but if the echo signal is from a moving object, the echo signal will be different due to the Doppler effect. The frequency components of are shifted by an amount proportional to the velocity of the object. A Doppler signal having a frequency that is the difference between the ultrasound signal that transmitted this echo signal and the received echo signal can be obtained. Dotsupura signal is
Since the signals are obtained as orthogonal signals, the phase delay or lead changes depending on whether the object approaches or moves away from the ultrasound beam direction. By frequency-analyzing this, it is possible to observe the velocity, direction, and distribution of various velocity components of blood flow.

Problems to be Solved by the Invention However, in order to obtain Doppler signals with sufficient sensitivity, it is necessary to amplify the echo signals with low noise, and furthermore, the power of the transmitted ultrasonic waves must not have any effect on living organisms. Although it is only a small amount, it requires a very large amount. Therefore, the power consumed by the dielectric loss of a piezoelectric element commonly used as an ultrasonic transmitting means turns into heat, and the acoustic energy generated by the piezoelectric element turns into heat. This heat will be radiated if the transmitting surface of the ultrasonic transmitting means is in contact with an object that easily propagates heat and sound waves, but if it is left in the air for a long time, the heat will accumulate inside and the ultrasonic waves will Although it depends on the shape and conversion efficiency of the transmitting means, when several hundred mw of driving power is supplied to the piezoelectric element, the temperature may reach 50 to 60° C. or more. As a result, in the long term it constitutes an ultrasonic transmitting means. The adhesion between the piezoelectric element, acoustic lens, and backing can sometimes peel off due to differences in thermal expansion coefficients, which has been a problem in terms of the lifespan of the probe.

Therefore, the present invention has been made to solve the above problems, and can prevent heat generation in the ultrasonic transmitting means, and can prevent the generation of heat between the piezoelectric element, the acoustic lens, and the backing that constitute the probe. The object of the present invention is to provide an ultrasonic Doppler blood flow meter that can prevent adhesive peeling and extend its life.

Means for solving the problems and technical means of the present invention to solve the above problems include an ultrasonic wave transmitting means for transmitting continuous ultrasonic waves into the living body, and receiving echo signals reflected within the living body. a reference signal generator that generates a driving frequency for driving the ultrasonic transmitting means and a reference signal for detecting a Doppler shift signal component from an echo signal; , a drive circuit that power amplifies the drive signal generated by the reference signal generator and drives the ultrasonic transmitting means, a detector that mixes the echo signal and the orthogonal reference signal and detects the Doppler signal, and the detector. The apparatus is equipped with a determination means that determines the contact state of the tentacle with the living body using a Doppler signal, and reduces the driving power of the drive circuit that supplies the ultrasonic wave transmitting means to the ultrasonic transmitting means when the contact is weak. .

Effect of the present invention With the above configuration, the ultrasonic transmitting means driven by the drive circuit transmits ultrasonic waves into the living body, and the ultrasonic receiving means receives the echo signals reflected within the living body and converts them into electrical signals. . The detector detects a Doppler signal from the echo signal converted into an electrical signal, and the determining means determines the state of contact of the probe with the living body based on the Doppler signal. When the probe is not in contact with the living body, the ultrasonic transmitting means can be prevented from generating heat by reducing the drive power of the drive circuit that supplies the ultrasonic transmitting means.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an ultrasonic Doppler blood flow meter according to a first embodiment of the present invention. In the same figure, ■ is a probe,
2 is an ultrasonic transmitting means of the probe 1, 37 is an ultrasonic receiving means of the probe 1, 4 is a drive circuit of the ultrasonic transmitting means 2, 5 is a receiving circuit of the ultrasonic receiving means 3, and 6 is a detection circuit. 7 is an F/V converter (frequency-voltage converter), 8
is a comparator, 9 is a reference voltage, ]0 is a reference signal generator, 11 is a frequency analyzer, and 12 is a display means. 13 is the body surface of the living body, and 13a is a reflector inside the living body.

The operation of the above configuration will be explained below. Ultrasonic waves of frequency f are continuously transmitted from the ultrasonic transmitting means 2 driven by the drive circuit 4, propagate from the body surface 13 of the living body, and are reflected by the reflector 1312 inside the living body.

If the reflector 131Z is moving in the same direction as the ultrasonic propagation direction, the frequency of the reflected echo signal is due to the Doppler effect, and ff, tcfd is the Doppler shift frequency, and the frequency of the reflected echo signal is the Doppler shift frequency. The frequency is proportional to the speed. ), and if it moves in the opposite direction, f+fd
becomes. The ultrasonic receiving means 3 converts this echo signal into an electrical signal, which is subjected to appropriate amplification and filtering processing in the receiving circuit 5, and then a Doppler signal is detected by the detector 6. The reference signal generator 10 generates a reference signal having the frequency f of the drive signal, and the reference signal having the same frequency is also provided to the wave detector 6. Further, when displaying blood flow information in the forward direction and reverse direction separately, a reference signal having the same frequency and orthogonal to each other is applied to the detector 6. The detector 6 detects the Doppler signal fd as the beat frequency fd of the reference signal frequency f and the echo signal frequency f+fd. The detected Doppler signal is subjected to frequency analysis by a frequency analyzer 11 and displayed as diagnostic information on a display means 12 such as a CRT or chart record. In parallel, the detected Doppler signal is converted by the F/V converter 7 into a DC frequency voltage proportional to the Doppler shift frequency fct. The comparator 8 compares the frequency voltage with a preset reference voltage 9, and when the frequency voltage is lower than the reference voltage 9, controls the drive circuit 4 to reduce the amplitude of the drive signal.

2(a) and (h) show the relationship between the general input/output characteristics of the F/■ converter 7 and the comparator 8. FIG.

■TH is the reference voltage that the comparator 8 compares, and the set value is ftt, when it is several Hz,
Let it be the frequency voltage output by the F/■ converter 7.

Therefore, when the Doppler signal is below several Hz, the frequency voltage falls below VTH, the output of the comparator 8 becomes the "■1" level, and the amplitude of the drive signal output from the drive circuit 4 is reduced. At this time, if the drive signal is completely stopped, when the probe 1 comes into contact with the living body again, no echo signal will be detected and it will be impossible to determine whether or not there is contact. The minimum driving power must be supplied to the extent that a possible echo signal can be obtained.

As explained above, according to this embodiment, the F/V converter 7 and the comparator 8 determine whether or not the probe 1 is in contact with the body surface 13 of the living body based on the frequency of the received Doppler signal.
When the frequency of the Doppler signal is determined to be several Hz or less by a determination means such as Therefore, the life of the probe 1 can be extended.

FIG. 3 on page 10 is a block diagram of an ultrasonic Doppler surface flowmeter according to a second embodiment of the present invention. In this embodiment, the function of the determination means consisting of the F/V converter 7, comparator 8, etc. explained in the first embodiment is replaced by a frequency analyzer 11 and an arithmetic circuit 1.
4, and the other configurations are the same as in the first embodiment.

The operation of the configuration of the second embodiment as described above will be explained below. In this embodiment as well, the process from obtaining a Doppler signal to frequency analysis and outputting blood flow information to the display means 12 is the same as in the first embodiment. In this embodiment, in order to determine whether the probe 1 is in contact with the body surface 13, the calculation circuit 14 calculates the Doppler signal converted into a spectral signal by the frequency analyzer 11, and calculates the 1
(The drive power of the drive circuit 4 is reduced when there is no spectral value greater than or equal to z.

As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained by determining the state of the probe 1 based on the frequency vector of the frequency-analyzed Doppler signal.

As described in detail, according to the ultrasonic Doppler flowmeter of the present invention, the determining means determines the contact state of the ultrasonic transmitting surface of the probe with the living body from the Doppler signal, and
If not, the drive power of the drive circuit that supplies the ultrasonic transmitter is reduced, which prevents heat generation and prevents the adhesive between the piezoelectric element, acoustic lens, and backing that makes up the probe from peeling off. It is possible to extend the service life by doing this.

[Brief explanation of drawings]

1 and 2 show an ultrasonic Doppler blood flow meter according to a first embodiment of the present invention, FIG. 1 is a block diagram, and FIG.
FIG. 3 is a block diagram showing an ultrasonic Doppler blood flow meter in a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Probe, 2... Ultrasonic transmitting means, 3... Ultrasonic receiving means, 4... Drive circuit, 5... Receiving circuit,
6...Detector, 7...F/Vl inverter, 8...
Comparator, 10... Reference signal generator, 11...
Frequency analyzer, 14... arithmetic circuit.

Claims (3)

[Claims] (1) A probe having an ultrasonic transmitting means for transmitting continuous ultrasonic waves into the living body, an ultrasonic receiving means for receiving echo signals reflected within the living body, and a driving frequency for driving the ultrasonic transmitting means. a reference signal generator that generates a reference signal for detecting the Doppler shift signal component from the echo signal; and a drive signal generated by the reference signal generator that is power amplified to drive the ultrasonic transmitting means. a drive circuit that mixes the echo signal and the orthogonal reference signal and detects a Doppler signal; An ultrasonic Doppler blood flow meter characterized by comprising a determining means for reducing the driving power of the driving circuit supplied to the transmitting means. (2) The determination means compares an F/V converter that converts the frequency of the Doppler signal into a voltage, and this voltage with a reference voltage,
The ultrasonic Doppler blood flow meter according to claim 1, further comprising a comparator that controls the amplitude of the output signal of the drive circuit based on the determination result. (3) The method according to claim 1, wherein the determining means comprises an arithmetic circuit that calculates a Doppler signal converted into a vector by a frequency analyzer and reduces the drive power of the drive circuit based on the determination result. Sonic Doppler blood flow meter.