Disclosure of Invention
In order to solve the above technical problems, an object of the present invention is to provide a fast and efficient multi-channel evoked potential monitoring method and system based on independent component analysis.
In one aspect, an embodiment of the present invention provides a multichannel evoked potential monitoring method based on independent component analysis, including the following steps:
collecting multi-channel electroencephalogram signals of a tested person under the action of repeated stimulation; the repeated stimulation is formed by repeatedly arranging a plurality of identical transient stimulation units in series;
preprocessing the acquired multi-channel electroencephalogram signals;
carrying out independent component analysis on the preprocessed multi-channel electroencephalogram signals to obtain a plurality of independent components;
taking the initial time of the stimulation unit as a reference, and taking a period of time before and after the reference to form a time window of signal segmentation; segmenting the independent components obtained after the independent component analysis according to a time window so as to obtain independent component samples of each stimulation unit;
carrying out time domain superposition averaging on the independent component samples to obtain an average evoked potential of each independent component;
after the evoked energy gain of the average evoked potential of each independent component is calculated, independent component samples are screened and removed according to a set criterion;
selecting a detection sample from the independent component samples, calculating the total evoked energy gain of the detection sample and the total evoked energy gain of the average sample of the detection sample, and judging whether the selected detection sample has the evoked potential caused by the stimulation unit.
Further, the step of selecting a detection sample from the independent component samples, calculating a total evoked energy gain of the detection sample and a total evoked energy gain of an average sample of the detection sample, and determining whether the selected detection sample has an evoked potential caused by the stimulus unit specifically includes:
selecting a plurality of independent component samples as detection samples, and calculating the total evoked energy gain of each detection sample;
performing superposition averaging on the selected detection samples, and then calculating the total induced energy gain of the averaged average samples;
and comparing the total evoked energy gain of the detection sample with the total evoked energy gain of the average sample, and judging whether the evoked potential caused by the stimulation unit exists in the detection sample.
Further, in the step of comparing the total evoked energy gain of the detection sample with the total evoked energy gain of the average sample and judging whether the evoked potential caused by the stimulation unit exists in the detection sample, a modified unilateral t-test method is adopted for test judgment.
Further, in the step of preprocessing the acquired multi-channel electroencephalogram signals, the preprocessing includes at least one of filtering processing, interpolation processing and abnormal data elimination.
Further, in the step of obtaining a plurality of independent components after performing independent component analysis on the preprocessed multi-channel electroencephalogram signals, independent component analysis is performed by adopting an information maximization ICA algorithm or a maximum likelihood ICA algorithm.
Further, the calculation formula of the evoked energy gain is as follows:
where EER denotes the evoked energy gain in dB, x (τ) denotes the signal to be calculated, τ -0 denotes the starting time of the stimulation unit, Δ t1B-a denotes spineA time before the initiation of the excitation unit, specifically representing the rest period of the evoked response, Δ t2D-c denotes the period of time after the stimulation unit has started the onset of evoked potentials.
Further, after the evoked energy gain of the average evoked potential of each independent component is calculated, the step of screening and rejecting independent component samples according to a set criterion is specifically as follows:
and after the evoked energy gain of the average evoked potential of each independent component is calculated, screening out the independent component corresponding to the evoked energy gain smaller than a preset threshold value as an interference component to remove.
Further, the calculation formula of the total evoked energy gain is as follows:
wherein GEER represents the total induced energy gain in dB, xj(τ) represents the signal to be calculated, j ═ 1,2, …, p, the serial number of the individual component samples remaining after screening, τ ═ 0 represents the starting time of the stimulation unit, Δ t1B-a denotes the moment before the start of the stimulation unit, in particular the resting period of the evoked response, Δ t2D-c denotes the period of time after the stimulation unit has started the onset of evoked potentials.
In another aspect, an embodiment of the present invention provides a multi-channel evoked potential monitoring system based on independent component analysis, including:
at least one processor;
at least one memory for storing at least one program;
when the at least one program is executed by the at least one processor, the at least one program causes the at least one processor to implement a multi-channel evoked potential monitoring method based on independent component analysis according to an embodiment of the present invention.
In this embodiment, after acquiring and preprocessing a multi-channel electroencephalogram signal, performing independent component analysis to obtain a plurality of independent components corresponding to the multi-channel electroencephalogram signal, so as to obtain an independent cost sample of each stimulation unit based on the starting time of the stimulation unit, performing time-domain superposition averaging on the independent component samples to obtain an average evoked potential of each independent component, screening and removing the independent components based on an evoked energy gain of the average evoked potential of each independent component according to a set criterion, selecting a plurality of independent component samples as detection samples from the independent component samples, calculating a total evoked energy gain of the detection samples and a total evoked energy gain of the average sample of the detection samples, and thus determining whether the selected detection samples have evoked potentials caused by the stimulation units Screening and rejecting can detect whether any detection sample contains evoked potential, the calculation speed is high, the efficiency is high, the detection sensitivity is high, the problems of long time consumption and low efficiency of the existing detection method are solved, and whether the signal to be detected contains evoked potential can be quickly detected.
Detailed Description
The step numbers in the embodiments of the present invention are set for convenience of illustration only, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.
Method embodiment one
Referring to fig. 1, the present embodiment provides a multi-channel evoked potential monitoring method based on independent component analysis, which is executed by a microprocessor, an embedded processor or a computer terminal, and comprises the following steps:
s1, collecting multi-channel electroencephalogram signals of the testee under the action of repeated stimulation; the repetitive stimulus is composed of a plurality of identical transient stimulus units arranged in series, and in this embodiment, the repetitive stimulus is composed of N series of stimulus units.
S2, preprocessing the acquired multi-channel electroencephalogram signals; in this step, the preprocessing includes at least one of filtering, interpolation, and elimination of abnormal data. The filtering processing is as follows: the band-pass filtering is carried out on the multi-channel electroencephalogram signals, and the specific pass band range can be set according to the actual signal bandwidth. The interpolation processing means: according to the statistical characteristics, after detecting the electroencephalogram signals of a plurality of channels with abnormality, carrying out interpolation processing on the electroencephalogram signals; the statistical characteristics refer to the correlation, variance and the like among the electroencephalogram signals of each channel. The abnormal data elimination means that: detecting abnormal observation signals of a single stimulation unit according to the statistical characteristics, and marking the abnormal observation signals as invalid values; statistical properties here refer to the deviation, variance, etc. between the mean of the evoked responses of a single stimulation unit and the mean of the evoked responses of all stimulation units of the channel. By preprocessing the multichannel electroencephalogram signals, obviously abnormal data and invalid data can be removed, and the calculation amount of the subsequent data processing process is reduced.
S3, carrying out independent component analysis on the preprocessed multichannel electroencephalogram signals to obtain a plurality of independent components; in the step, an information maximization ICA algorithm or a maximum likelihood ICA algorithm is adopted to carry out independent component analysis, and a plurality of obtained independent components comprise components such as signals with different proportions, artifact interference and the like.
S4, taking the starting time of the stimulation units as a reference, obtaining independent component samples of each stimulation unit; the method comprises the following specific steps: the method specifically comprises the following steps: taking the initial time of the stimulation unit as a reference, and taking a period of time before and after the reference to form a time window of signal segmentation; and segmenting the independent components obtained after the independent component analysis according to the time window so as to obtain the independent component sample of each stimulation unit.
S5, carrying out time domain superposition averaging on the independent component samples to obtain an average evoked potential of each independent component; the method comprises the following specific steps: and segmenting each obtained independent component according to the starting time of each stimulation unit which is repeatedly stimulated, aligning the independent component samples obtained by segmentation according to the starting time of the stimulation units, and calculating the average value of all the independent component samples to be used as the average evoked potential of the independent component.
S6, after calculating the evoked energy gain of the average evoked potential of each independent component, screening and rejecting independent component samples according to a set criterion;
s7, selecting a detection sample from the independent component samples, calculating the total evoked energy gain of the detection sample and the total evoked energy gain of the average sample of the detection sample, and judging whether the selected detection sample has an evoked potential caused by the stimulation unit.
In this embodiment, after acquiring and preprocessing a multi-channel electroencephalogram signal, performing independent component analysis to obtain a plurality of independent components corresponding to the multi-channel electroencephalogram signal, so as to obtain independent cost samples of each stimulation unit based on the starting time of the stimulation unit, performing time-domain superposition averaging on the independent component samples to obtain an average evoked potential of each independent component, screening and removing the independent component samples according to a set criterion after the evoked energy gain of the average evoked potential of each independent component is based on, and then selecting a plurality of independent component samples as detection samples from the independent component samples to calculate a total evoked energy gain of the detection samples and a total evoked energy gain of the average sample of the detection samples, thereby determining whether the selected detection samples have evoked potentials caused by the stimulation units Screening and rejecting can detect whether any detection sample contains evoked potential, the calculation speed is high, the efficiency is high, the detection sensitivity is high, and whether the signal to be detected contains evoked potential can be rapidly detected.
In a further preferred embodiment, in step S6, the formula for calculating the induced energy gain is:
where EER denotes the evoked energy gain in dB, x (τ) denotes the signal to be calculated, τ denotes the time, τ -0 denotes the starting time of the stimulation unit, Δ t1B-a denotes the moment before the start of the stimulation unit, in particular the resting period of the evoked response, Δ t2D-c denotes the period of time after the stimulation unit has started the onset of evoked potentials.
Evoked energy gain EER essentially represents the energy gain of neural activity before and after stimulation. In the calculation formula, x (τ) represents the signal to be calculated, and in the present step, x (τ) refers to the average evoked potential of the individual components. Since the correlation between the average evoked potential of the independent components and the conventional evoked potential waveform is not clear, and the ratio of the included evoked components, spontaneous components, and artifact interference is unknown, for a section of signal x (τ) that may include an evoked potential, the signal components and energy distribution change due to the stimulation that may trigger the neural synchronization activity, and therefore, the evoked response energy gain can be expressed by the formula of the evoked energy gain EER defined in this step. The extracted independent components are screened based on the evoked energy gain EER, so that the evoked potential components and the gain of the enhanced reaction can be more effectively highlighted in the subsequent treatment process, and the detection capability of the evoked potential is obviously improved.
Further preferably, the criterion set in step S6 is a set criterion for screening the independent components, and for example, the independent components having an induced energy gain within a certain interval are screened and removed. Specifically, in step S6, it specifically is:
and after calculating the induced energy gain EER of the average induced potential of each independent component, screening out the independent component corresponding to the induced energy gain EER smaller than a preset threshold value as an interference component to remove.
For example, a preset threshold is set to 3dB, the independent component having an EER smaller than the preset threshold is determined as an interference component and discarded, and the remaining independent component is determined as a signal component, i.e., a valid independent component.
The smaller the evoked energy gain EER, the less the energy of the evoked potential contained, or the greater the disturbance, based on which the independent component of the larger disturbance can be removed. In the process of filtering and rejecting the independent components, various customized rules may be adopted for filtering and rejecting, for example, step S6, and may also be:
after the evoked energy gain EER of the average evoked potential of each independent component is calculated, all the calculated evoked energy gains EER are sequenced, and thus the independent component corresponding to the evoked energy gain EER with the lowest numerical value and the preset proportion is screened out and removed as an interference component. For example, after sorting, the independent component corresponding to the EER with the lowest value of 5% is taken as an interference component to be removed.
Because the acquired multi-channel electroencephalogram signals can be regarded as different weight mixtures of source signals from different brain areas, interference and the like, after independent component analysis is carried out in the step S3, the source signals can be separated from the multi-channel electroencephalogram signals to be detected to obtain a plurality of source signals, which are called as independent components in the application. In step S6, by removing the independent component with low signal-to-noise ratio, the number of subsequent calculations can be reduced, and the detection efficiency of the method can be improved.
In a further preferred embodiment, in step S7, the total induced energy gain is calculated by the following formula:
wherein GEER represents the total induced energy gain in dB, xj(τ) represents the signal to be calculated, j ═ 1,2, …, p, the number of the individual component samples remaining after screening, τ represents the time, τ ═ 0 represents the starting time of the stimulation unit, Δ t represents the number of the individual component samples remaining after screening, and1b-a denotes the moment before the start of the stimulation unit, in particular the resting period of the evoked response, Δ t2D-c denotes thornThe time period during which the evoked potential begins to appear after the firing of the cells.
The embodiment enhances the reserved independent components by defining the measurement parameter of the total evoked energy gain, and is more convenient for realizing the detection of the evoked potential.
Further as a preferred embodiment, the step S7 specifically includes:
s71, selecting a plurality of independent component samples as detection samples, and calculating the total induced energy gain of each detection sampleGEER j(j ═ 1, 2.., n), where n denotes the number of samples tested. In this step, x required for computing the GERj(τ) represents the individual component samples after screening of the test sample.
S72, performing superposition averaging on the selected detection samples, and calculating the total induced energy gain of the averaged average samples; in this step, after n detection samples are subjected to time domain superposition averaging to obtain an average sample, the total induced energy gain is calculated and recorded as mgER. In the step, the average sample after the superposition average of the selected detection samples is used as x required for calculating the GEERj(τ) is calculated by substituting the total induced energy gain into the calculation formula.
And S73, comparing the total evoked energy gain of the detection sample with the total evoked energy gain of the average sample, and judging whether the evoked potential caused by the stimulation unit exists in the detection sample. Specifically, whether the evoked potential caused by the stimulation unit exists in the detection sample is judged by judging whether the sum of the total evoked energy gain of the detection sample and the total evoked energy gain of the average sample is significantly larger than 0, and if the sum is larger than 0, the evoked potential caused by the stimulation unit exists in the detection sample is judged, otherwise, the sum is judged to be absent.
In a further preferred embodiment, in step S73, the check judgment is performed by a modified one-sided t-test method. The method specifically comprises the following steps: taking the total evoked energy gain value of each detection sample as the sample value of the t-test; taking the total induced energy gain of the average sample of the selected detection samples as the offset value of the sample of the t-test; a one-sided t-test is used to detect if the sum of the sample value and the offset value is greater than 0. Utensil for cleaning buttockBody pass judgment sample setGEER j(ii) whether + mGEER } is significantly greater than 0 is examined (p)<0.001). By adopting a modified unilateral t-test method for test judgment, whether the evoked potential exists can be accurately and quickly detected.
Method embodiment two
The embodiment is a detailed example of the first embodiment of the method, and particularly adopts a NeuroScan (synthesis amps2) electroencephalogram recording system to acquire multi-channel electroencephalogram signals of a tested person under the action of repeated stimulation. In this embodiment, the repetitive stimulation is composed of a plurality of identical transient stimulation units arranged in series and repeatedly, specifically, the repetitive stimulation composed of short pure tones with duration of 50ms is adopted, the stimulation interval is 1.01s, and the number of stimulation is about 500. In the test process, the placement mode of the test electrodes is as follows: adopting an international 10-20 system, 36 positions of the electrodes are selected, wherein the 36 positions are respectively as follows: FT7, FC5, FC3, FC1, FCZ, FC2, FC4, FC6, FT8, T7, C5, C3, C1, CZ, C2, C4, C6, T8, TP7, CP5, CP3, CP1, CPZ, CP2, CP4, CP6, TP8, P7, P5, P3, P1, PZ, P2, P4, P6, P8, wherein the reference electrode is at the midpoint of CZ and CPZ and Ground (GND) is at the midpoint of Fz and FpZ.
The method mainly comprises the following steps:
step 1, outputting repeated stimulation to a tested person through a professional earphone (such as an ER-3 plug-in earphone), recording observation signals of 36 channels by an acquisition system, and simultaneously recording output time of the repeated stimulation to be used as multi-channel electroencephalogram signals.
And 2, after preprocessing of filtering processing, interpolation processing, abnormal data elimination and the like is carried out on the acquired multi-channel electroencephalogram signals, independent component analysis is carried out on the preprocessed multi-channel electroencephalogram signals by adopting a maximum likelihood ICA algorithm, and 30 independent components are obtained through decomposition.
And 3, segmenting each independent component according to the starting time of each stimulation unit, specifically segmenting according to-400 ms to +600ms to obtain 565 independent component samples, aligning the independent component samples, and performing time domain superposition averaging to obtain the average evoked potential of each independent component. In this example, the average evoked potentials of the individual components obtained are shown in FIG. 2.
Step 4, calculating an evoked energy gain EER of the average evoked potential of each independent componentiI-1, 2, …,30, where Δ t2250-50-200 (ms), namely selecting a time period (corresponding to N100 and P200 component waves in the evoked potential) 50-250 ms after the starting time of the stimulation unit, and inducing response rest time period delta t1400-0-400, namely, selecting the time period from-400 ms to 0ms before the starting time of the stimulation unit.
Step 5, calculating the obtained EERiSorting in an ascending manner, determining that the EER selection threshold is 3dB, and judging the independent component with the EER smaller than the threshold as the interference component to be discarded.
Step 6, arbitrarily selecting n (═ 11) detection samples, and calculatingGEER jJ is 1,2, …,11, and then the mger of n consecutive stimulation units is calculated. Performing unilateral t test, and obtaining a test resultGEER j+ mGEER } is significantly greater than 0 (p)<0.001), the presence of evoked potential is judged. In this embodiment, the total induced energy gain of the sample is detectedGEER jAs shown in fig. 3, line a represents the average energy at rest before stimulation, line b represents the average energy of the signal after stimulation, and it can be seen from fig. 3 that the average energy of the signal after stimulation is significantly greater than the average energy at rest before stimulation.
System embodiment
Referring to fig. 4, the present embodiment provides a multi-channel evoked potential monitoring system based on independent component analysis, including:
at least one processor 100;
at least one memory 200 for storing at least one program;
when executed by the at least one processor 100, cause the at least one processor 100 to implement the independent component analysis based multi-channel evoked potential monitoring method.
The multi-channel evoked potential monitoring system based on independent component analysis of the embodiment can execute the multi-channel evoked potential monitoring method based on independent component analysis provided by the method embodiment of the invention, can execute any combination implementation steps of the method embodiment, and has corresponding functions and beneficial effects of the method.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.