JPS6014846A - Embryo cardiac pulse meter for observing movement state - 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 The present invention relates to a fetal heart rate meter that counts the heart rate of a fetus using the ultrasonic Doppler method.

Conventional Doppler fetal heart rate monitors based on the Doppler method detect periodicity and derive heart rate by extracting pulsating components derived from the movement of the cardiac muscle or valves of the fetal heart. .

However, although this method is well-developed, it still has some drawbacks. For example, the following two points.

(If the fetal heart deviates from the directivity of the probe, there will be no signal and no work will be possible. This problem cannot be completely resolved even if a wide-angle directivity probe is used.

(2) When observing while walking or doing light work, periodic movements of the mother's body cause periodic artifacts that can be confused with heartbeats.

From this point of view, even when attempting to observe the dynamics of fetal physiology, accurate observation has been difficult in situations where the mother's body is under stress.

There are many things.

In order to achieve such an objective, the present invention uses the ultrasound Dob 2 method to detect the Doppler shift value from the fetal artery blood flow, which exhibits a higher Doppler shift value than the Doppler shift value of the archia act, which occurs due to sudden maternal movement. It is characterized in that only the pulsatile Doppler signal is extracted using a filter and the fetal heart rate is measured.

The present invention will be described in detail below using the drawings. in the first place,
For a Doppler blood flow signal, the correct way to evaluate the blood flow velocity is to focus on its amplitude, Doppler shift local wave number, or its distribution.

However, if the Doppler blood signal is extracted through a bandpass filter whose center frequency is near the highest possible Doppler shift frequency and whose passband has a moderate cut below, it is possible to It is possible to obtain almost the same results as by focusing on the flow velocity.

Incidentally, in the case where only the rise in blood pulsation is to be detected, the lower cut of the band-pass filter may be made sharp. This kind of filter corresponds to a Doppler filter in a broad sense, and the invention that considers the myocardium, valves, body movement artifacts, etc. as unnecessary components with a low Doppler shift is much higher than before. of the area,
For a Doppler shift of about 0.3 to 1 pamil]11
It includes a matching bandpass filter and means for subsequent amplitude detection. FIG. 1 shows a block diagram of one embodiment. In the figure, 1 is a probe that sends and receives ultrasonic waves to and from the subject (mother body), 2 is an oscillator that generates high-frequency energy to drive the probe, and 3 is a Doppler shift signal that is generated from a reflected wave signal. Doppler receiver, 4, is a Doppler shift ratio of at least 24 dB/octave or higher power, which allows components of 0.3 to 1 bar mil to pass through but sharply cuts off components of less than 24 dB/octave. 5 is a detection circuit, 6 is a low-pass filter, and 7 is a binarization circuit ◇ In such a configuration, the ultrasonic wave is energized by the high frequency energy from the oscillator 2. The generated probe beam then receives the reflected wave, converts it into an electrical signal, and outputs it. The Doppler receiver 3 calculates a Doppler shift signal from the frequency of the oscillator 2 (corresponding to the frequency of the sound wave transmitted by the probe) and this electrical signal. The next-stage Doppler filter 4 extracts only pulsatile Doppler blood flow signals in a useful range, that is, a Doppler shift ratio of about 0.3 to 1 pamil. This filtering effect can suppress interference with blood flow signals caused by maternal oscillations and fetal movements. After detecting this pulsating Doppler signal, a low-pass filter 6 removes its high-frequency components to obtain a pulsating waveform as shown in FIG. 2 (0). Next, this is applied to the binarization circuit 7 and binarized at a certain threshold level to obtain a pulse train signal as shown in FIG. 2(b). By inputting and measuring the pulse signal obtained in this manner into a heart rate meter (not shown) or the like, the fetal heart rate can be easily determined.

FIG. 3 is a diagram showing another embodiment of the present invention. In the same figure,
Regarding the waveform of the Doppler shift signal obtained through the filter 4 in the same manner as above, the rising point of the waveform is detected by the zero-cross detector 21, and the mono-staple vibrator 22 is activated by the output of the detector, thereby detecting the waveform for a certain period of time. Obtain a pulse train signal consisting of pulses of the same width. When this pulse train signal is applied to a low-pass filter 6, a pulsating waveform is obtained as in the case of FIG. 1, which is then similarly detected by a binarization circuit 7 and output as a signal having a period corresponding to the fetal heartbeat.

Note that the method of determining the period of the fetal heartbeat based on the output signal from the Doppler filter 4 is not limited to this embodiment, and a method using the Fourier transform method or autocorrelation method may also be adopted. good.

Furthermore, with respect to the fetal blood flow signal, it is necessary to devise a method to distinguish between the fetal artery blood flow Doppler signal and that of the maternal artery blood flow and extract only the Doppler signal of the fetal artery blood flow. Physiological standard parameters are used to differentiate between the two types of arterial blood flow. Tsuma υ,
As shown in Figure 4, from the envelope of a certain frequency band of the blood flow signal or the envelope of the spectrum 2m viewed from a broadband perspective, Rise time t of the flow pattern at the beginning
If we focus on one or both of r (shorter in the fetus), we can distinguish and extract only the Doppler signal of the fetal arterial blood flow, since there are statistical differences roughly as shown in Table 1. .

Table 1, that is, FIG. 5 shows an example of the configuration of a means for distinguishing such maternal artery blood flow signals, and in this table, regarding the pulsation waveform 51 obtained as described in d above, (very large) and very small Point detection is performed by charge/discharge type peak followers 52,53. FIG. 6 is a waveform diagram showing the working process, and FIG. 7 shows an example of the important circuit of FIG. 5.

In FIG. 7, a portion consisting of amplifier A1, capacitor vcm, diode D□, resistor R and current source cs1 forms a positive peak follower, and similarly A2. C2゜D21
The portion consisting of R2 and cs2 forms a negative peak follower. C1, 2 are charged only in the direction allowed by D1, 2 so as to follow the signal waveform (input pulse wave 51), but discharged in the opposite direction only at a rate controlled by each cs□, 2. Because of the warpage and warpage, the terminal waveforms of cl and C2 can only follow the upward slope or downward slope (in the same order) toward the top or bottom point of the corresponding side, as shown in FIG. 6, 61 and 62.

While tracking, the output of A1 or A2 follows the input voltage, respectively, but when it cannot follow, a negative saturation value is output. The large amplitude rise and fall during this period are C3 to C3 respectively.
6 and R3-R6 and applied to G□ to G4 (exclusive OR game) When G□ to G4 are connected as shown in the figure, K is applied to each of them to respond to a narrow pulse of the desired polarity.
Become. The results are summarized in 65, and when any one of these comes (in principle, they cannot come at the same time), an interrupt request is sent to the CPU (not shown), and the same
This includes measuring the time width between -d and determining whether the signal source is a mother or a child, taking into consideration that value and the data in Table 1 above. Note that measuring the time interval for each type of interrupt based on the interrupt using software is a well-known technique, and its explanation will be omitted here.

In addition, when the above-mentioned heart rate value is measured based on the heart cycle period τ, each period between d and d in Fig. 6 corresponds to τ, and even though the signal has a characteristic of 164 points of timing, there is little variation, so it is It is most preferable to use

In addition, it is possible to distinguish between mother and child based on T in Figure 4 as mentioned above, which is palliative but also based on C in Figure 6.
This can also be done by determining the time between -d.

As explained above, according to the present invention, among the Doppler shift signals, only the signals particularly related to the fetal heartbeat are extracted through the Doppler filter, so that the signal is not affected by maternal sway or fetal movement. It is possible to easily determine the fetal heart rate from this signal by obtaining a pulse train signal related only to the fetal heartbeat, which has a great effect in practical use.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the fetal heart rate meter for measuring dynamics according to the present invention, FIG. 2 is an operational waveform diagram of each part in FIG. 1, and FIG. 5 is a diagram of another embodiment of the present invention. , FIG. 4 is a diagram for explaining the physiological standard parameters of arterial blood flow, FIG.
The figure is a waveform diagram for explaining the operation in Figure 5.
The figure is a more detailed configuration diagram of a part of FIG. 5. DESCRIPTION OF SYMBOLS 1... Subject, 2... Oscillator, 3... Doppler receiver, 4... Doppler filter, 5... Detection circuit, 6...
...Low pass filter, 7...Binarization circuit, 21...
・Zero cross detector, 22... Mono staple pipe rake. Fig. l Fig. 2

Claims (2)

[Claims] (1) In a fetal heart rate monitor that uses the Doppler ultrasonic method from above the maternal abdominal wall to obtain a Dobb 2 shift signal based on the fetal arterial blood flow and determine the fetal heart beat cycle, the Doppler shift ratio is approximately A Doppler filter is provided that blocks components with a Doppler shift ratio of about 0.3 to 1 per mil. A fetal heart rate monitor for dynamic observation, characterized in that it is possible to extract signals related to the beating cycle of the fetal heart without being affected by maternal movement or fetal movement. (2) The device is configured to obtain a fetal heart rate value by detecting the periodicity of changes in the short-term average frequency of the fetal blood flow signal obtained through the Dob 2 filter. Fetal heart rate monitor for dynamic observation according to item 1 (5) With respect to the fetal blood flow signal obtained through the Doppler filter, a Doppler signal of the fetal arterial blood flow is determined due to the length of the ejection period of the heartbeat stroke. The fetal heart rate monitor for dynamic observation according to claim 1, characterized in that the fetal heart rate monitor is configured to distinguish between maternal artery blood flow and that of maternal artery blood flow.