JPS62323A - Addition averaging method of living body inducing signal - 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 amplifies signals induced in the biological nervous system, brain, etc. in response to repeatedly generated stimulation waves using an amplifier, and then samples them using a sampling pulse train synchronized with each stimulation wave. This invention relates to an averaging method for biologically induced signals that measures nerve conduction characteristics, etc. by repeatedly adding and updating the signals in a memory and storing them in a memory, and displaying the stored added induced signals on a display unit. be.

[Problems to be solved by the prior art and the invention] According to this averaging method, even a weak induced signal contained in noise is reflected on the display screen by changing the S/N ratio. It can be displayed. However, recently, in order to observe not only the entire induced signal waveform but also its minute phenomena, it has become necessary to enlarge and display minute waveforms such as rising portions. Conventionally, for this purpose, the same measurement was repeated by changing the amplifier characteristics and sampling speed conditions, which resulted in lack of reproducibility of measurements under the same conditions and requiring extra measurement time. Further, if it is attempted to read out such a plurality of types of addition results from the memory and compare them on the display screen, the capacity of the memory must be correspondingly increased.

In view of this point, the present invention provides an arithmetic and averaging method for biologically induced signals that enables display of a part of the time axis and amplitude of the induced signal by enlarging or reducing it by one measurement using a simple circuit configuration. The purpose is to

[Means for solving problems]

In order to achieve this object, the present invention provides a system in which the sampling period of each sampling pulse train and the gain of the amplifier are switched to 0 after a predetermined time has elapsed in synchronization with the stimulation wave.For example, as shown in FIG. When a predetermined time elapses T1, T
2. The period of the sampling pulse is gradually lengthened, and at the same time, the amplification degree of the amplifier is gradually lowered.

[Effect]

When the addition trigger signal is displayed, it is read out from the memory at the same speed, and the sampling pulse period is changed to be relatively short, so that the time axis can be relatively expanded. Furthermore, by switching the amplifier to a direction where the gain is large, the amplitude is also relatively expanded.

For example, the high-frequency small amplitude that appears in the →T1 region, TI-T2 region, and T2→ region from the rise of the input induced signal in FIG.
The mid-range medium amplitude signal and the low-range large amplitude signal are displayed with their time widths and amplitudes expanded in accordance with the inverse ratio of the sampling period and the ratio of the amplification degree so that they can be easily observed on the display screen.

[Embodiments of the invention]

An embodiment in which the present invention is applied to an averager for multi-channel evoked electroencephalogram signals will be described.

In FIG. 2, reference numeral 1 denotes a stimulation wave generator for applying stimulation waves at, for example, 50 Hz to a living body. Reference numeral 2 denotes a sampling pulse generation circuit capable of generating a sampling pulse train in which one cycle is switched in two stages common to all channels. 3
1 to 3n are preamplifiers for n channels whose gain frequency characteristics are independently switched into two stages. 4 is a preamplifier 3 (~3
This is an A/LO converter that sequentially digitizes the output signals of m. Reference numeral 5 denotes an addition memory whose capacity corresponds to the number of addresses and the number of channels according to the time axis resolution of the cathode ray tube display 8. Reference numeral 6 denotes a display control circuit that reads out the contents of the addition memory 5 during or at the end of addition and displays it on the cathode ray tube display 8. Reference numeral 7 denotes an adder that adds the output signal of the A/D converter 4 and the addition result of the corresponding channel and address in the addition memory 5, and updates the addition result. Reference numeral 9 denotes an addition condition setting unit for setting the number of additions, the gain frequency characteristic corresponding to the sampling pulse of the amplifier 3 of each channel, the sampling period of each channel and its switching elapsed time, etc. IO is a control circuit that controls each section 2 to 7 in response to the command from this setting section.0 condition setting is 1, for example, the number of additions is t, ooo times, and the sampling pulse is initially set to 201 times in common to each channel.
512 Ls 1 then 200 IL! Generate 512 1's. The gain frequency characteristics of the preamplifier 3 can be set independently, and the clock pulse duration of 20p, s for the preamplifier 3.

Increase the degree of amplification by 5 times relative to the 2001Ls period,
The shear frequency is 5K) Iz for the former, IKHz for the S type.
shall be.

The operation is as follows.

Each time a stimulation wave is applied to a living body, each amplifier 31 to all
The associated induced signal is input to +, and is amplified with the set gain frequency characteristic. Then, each time a sampling pulse of a set period is generated, the amplified output of each channel is sampled in order, and added to the contents of the channel and address to which it belongs in the addition memory 5 in the adder
For example, 1ch preamplifier 3 whose contents are updated.
Assuming that the stimulation signal shown in Figure 3 is input to 1, the period of 20g5 x 512 = 10.24m5 after the generation of the stimulation wave is amplified at a relatively high frequency and high gain as described above, and the amplified output is relatively sampled at high speed. In the following period of 200 us x 512 = 102.4 ms, the frequency gain characteristic of the amplifier 3I and the sampling pulse of the sampling pulse generation circuit 2 are switched, and the adder 7 is amplified at a relatively low frequency and low gain and sampled at a low speed. The 0 display control circuit 6, which adds and updates the contents of the addition memory 5 1,000 times in synchronization with each sampling pulse, reads the intermediate progress of the memory and the final addition result from the addition memory 5 at the same speed. When read out and displayed on the cathode ray tube display 8, the time axis of the rising portion up to the elapse of the predetermined time of 10.24 m5 is magnified ten times, and the peak value of the amplitude corresponds to the change in the amplification degree, and the peak value is changed to the non-expanded portion. expanded to approximately the same level. Furthermore, after a predetermined period of time has elapsed, the cut-off frequency of the amplifier 3I is switched to a lower value, so that the superimposed high frequency component is removed.

Incidentally, in the above-described embodiment, the sampling pulse with a relatively short period may be inserted not from the starting point of the induced signal but in the middle of the induced signal if necessary. can also be applied. Furthermore, it is also possible to reduce local large signals instead of partially expanding small signals.

〔Effect of the invention〕

According to the above-described first aspect of the present invention, when averaging the induced signals of a living body, the time axis and amplitude of an arbitrary time width portion of the induced signals can be relatively enlarged or reduced to make it easier to see on the monitor screen in one measurement. .

Therefore, not only the measurement time is shortened, but also the influence of fluctuations in conditions such as temperature, the accent of the living body, the test subject's habituation to stimulation, etc. is eliminated, and highly accurate measurement is possible. Enlarged or reduced parts and other parts can be displayed simultaneously without increasing storage capacity.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a block diagram showing the circuit configuration of an embodiment thereof, and FIG. 3 is a waveform diagram of each part of the embodiment.

Claims (2)

[Claims] (1) After amplifying the biologically induced signal in response to the repeatedly generated stimulation waves using an amplifier, it is repeatedly sampled with a sampling pulse train synchronized with each stimulation wave, and the sampling signal is stored in memory while being updated by adding the number of repetitions. In the method for adding and averaging the memorized addition inducement signals on a display unit,
An averaging method characterized in that the sampling period of each sampling pulse train and the gain of an amplifier are switched at the elapse of a predetermined time in synchronization with a stimulation wave. (2) The averaging method according to claim 1, characterized in that the cutoff frequency of the amplifier is also switched when a predetermined time has elapsed.