JP2002153435A - Brain wave recording processing method - Google Patents
Brain wave recording processing methodInfo
- Publication number
- JP2002153435A JP2002153435A JP2000351125A JP2000351125A JP2002153435A JP 2002153435 A JP2002153435 A JP 2002153435A JP 2000351125 A JP2000351125 A JP 2000351125A JP 2000351125 A JP2000351125 A JP 2000351125A JP 2002153435 A JP2002153435 A JP 2002153435A
- Authority
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- Japan
- Prior art keywords
- waveform
- time series
- electrocardiogram
- electroencephalogram
- brain wave
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 210000004556 brain Anatomy 0.000 title claims abstract description 47
- 238000003672 processing method Methods 0.000 title claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 57
- 210000003128 head Anatomy 0.000 claims abstract description 5
- 210000004761 scalp Anatomy 0.000 claims abstract description 5
- 238000010606 normalization Methods 0.000 claims description 18
- 238000012935 Averaging Methods 0.000 claims description 15
- 230000001360 synchronised effect Effects 0.000 claims description 7
- 238000012545 processing Methods 0.000 abstract description 7
- 238000000537 electroencephalography Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 8
- 238000005259 measurement Methods 0.000 description 4
- 210000000624 ear auricle Anatomy 0.000 description 3
- 230000008030 elimination Effects 0.000 description 3
- 238000003379 elimination reaction Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
- 238000007025 Shibasaki cyclization reaction Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000003925 brain function Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 210000002837 heart atrium Anatomy 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
Landscapes
- Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、波形形状把握に
基づいた心電図アーチファクト除去処理による脳波記録
処理方法に関する。[0001] 1. Field of the Invention [0002] The present invention relates to an electroencephalogram recording processing method based on electrocardiogram artifact removal processing based on waveform shape grasp.
【０００２】[0002]
【従来の技術】脳機能の状態を調べる有効かつ簡便な方
法として脳波記録方法があるが、一般的な脳波記録方法
としては、耳朶に基準電極をおく導出法が用いられる。
しかしながら、この方法では、耳朶にしばしば脳電位が
混入する（耳朶活性化現象）ため、正確な電位マップ等
を求める際の障害となる。そこで、脳電位の影響が及ば
ない頭部外に基準電極を設置する方法が採用されている
が、この方法では、脳波よりも非常に大きい振幅（１０
倍以上）を有する、心臓の鼓動によって生ずる電位、す
なわち、心電図アーチファクト（脳波測定にとって雑
音）が混入するため、この心電図アーチファクトの除去
が重要となる。2. Description of the Related Art There is an electroencephalogram recording method as an effective and simple method for examining the state of brain function. As a general electroencephalography method, a derivation method in which a reference electrode is placed on an earlobe is used.
However, in this method, a brain potential is often mixed into the earlobe (earlobe activation phenomenon), which is an obstacle to obtaining an accurate potential map or the like. Therefore, a method of installing a reference electrode outside the head, which is not affected by the brain potential, has been adopted.
(I.e., twice or more), which is generated by a heart beat, that is, an electrocardiographic artifact (a noise for electroencephalogram measurement) is mixed in. Therefore, it is important to remove the electrocardiographic artifact.
【０００３】従来の頭部外基準電極による脳波記録方法
としては、人体の胸面と背面とに電極を設置し、２電極
間に適当な抵抗を挟んだものを基準電極として用いる方
法「Y. Ishiyama, M. Ebe, I. Honma and Z. Abe: Elim
ination of EKG artifactsfrom EEG s recorded with b
alanced non-cephalic reference electrodemethod, El
ectroenceph. clin. Neurophysiol., 53, 662/665, 198
2 」があるが、これは抵抗値の変動などで心電図アーチ
ファクトを精度良く除去できない場合があった。また、
脳波と同時に記録した心電図をトリガー信号として心電
図Ｒ波による頂点同期加算平均によってアーチファクト
形状を推定し除去する方法［M. Nakamura and H. Shiba
saki: Elimination of EKG artifacts from EEG record
s; A New method of Non-cephalic Referential EEG Re
cording,Electroenceph. clin. Neurophysiol., 66, 88
/92, 1987 ］があるが、個々の心電図アーチファクトの
形状変動が無視できないので、除去精度が低いという問
題点があった。As a conventional method for recording an electroencephalogram using a reference electrode outside the head, an electrode is provided on the chest and the back of the human body, and a method in which an appropriate resistance is sandwiched between two electrodes as a reference electrode [Y. Ishiyama, M. Ebe, I. Honma and Z. Abe: Elim
ination of EKG artifactsfrom EEG s recorded with b
alanced non-cephalic reference electrodemethod, El
ectroenceph. clin. Neurophysiol., 53, 662/665, 198
2), but in some cases, it was not possible to accurately remove ECG artifacts due to fluctuations in resistance. Also,
Method of estimating and removing artifact shape by vertex-synchronous averaging using R-wave of ECG using ECG recorded simultaneously with EEG as a trigger signal [M. Nakamura and H. Shiba
saki: Elimination of EKG artifacts from EEG record
s; A New method of Non-cephalic Referential EEG Re
cording, Electroenceph. clin. Neurophysiol., 66, 88
/ 92, 1987], but there is a problem that the removal accuracy is low because the shape variation of each ECG artifact cannot be ignored.
【０００４】[0004]
【発明が解決しようとする課題】そこで、本発明は、上
記課題に鑑み、高精度に心電図アーチファクトの除去を
行うことができる、波形形状把握に基づいた心電図アー
チファクト除去処理による脳波記録処理方法を提供する
ことを目的とする。SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides an electroencephalogram recording processing method by electrocardiogram artifact removal processing based on waveform shape grasp, which can remove electrocardiogram artifacts with high accuracy. The purpose is to do.
【０００５】[0005]
【課題を解決するための手段】上記目的を達成するため
に、本発明の脳波記録処理方法は、頭皮上の電極と脳電
位の影響が及ばない頭部外に設置した基準電極との間の
電位差を測定する脳波記録方法において、記録された原
脳波時系列から、原脳波時系列に混入した心電図アーチ
ファクト波形の正規化標準波形を作成し、心電図アーチ
ファクト正規化標準波形を用いて、原脳波時系列から、
波形変動特性を考慮して心電図アーチファクト推定時系
列を作成し、原脳波時系列から心電図アーチファクト推
定時系列を差し引き、脳波時系列成分のみを抽出するこ
とを特徴とする。In order to achieve the above object, an electroencephalogram recording and processing method according to the present invention provides a method for recording an electroencephalogram between an electrode on the scalp and a reference electrode placed outside the head which is not affected by brain potential. In the electroencephalogram recording method of measuring the potential difference, a normalized standard waveform of an electrocardiogram artifact waveform mixed with the original electroencephalogram time series is created from the recorded original electroencephalogram time series, and the electrocardiogram artifact normalized standard waveform is used. From the series,
The method is characterized in that an electrocardiogram artifact estimation time series is created in consideration of waveform fluctuation characteristics, an electrocardiogram artifact estimation time series is subtracted from an original electroencephalogram time series, and only an electroencephalogram time series component is extracted.
【０００６】また、正規化標準波形の作成は、原脳波時
系列を心電図アーチファクト波形の周期毎に分割し、分
割した各々の心電図アーチファクト波形の頂点時刻を同
期させて加算平均し、加算平均して求めた波形を電位０
となる時刻によって要素波形に分割し、要素波形毎に振
幅及び持続時間を正規化することを特徴とする。正規化
標準波形作成の他の方法は、脳波と同時記録した心電図
時系列と原脳波時系列を心電図波形周期毎に分割し、分
割した心電図波形から各々の正規化パラメータを抽出す
ると共に、この各々の正規化パラメータを用いて対応す
る各々の分割した原脳波時系列を正規化し、この正規化
した原脳波時系列を頂点時刻を同期させて加算平均し、
加算平均して求めた波形を電位０となる時刻によって要
素波形に分割し、この要素波形毎に振幅及び持続時間を
正規化することを特徴とする。[0006] In addition, the generation of the normalized standard waveform is performed by dividing the original brain wave time series for each cycle of the ECG artifact waveform, synchronizing and summing the vertice times of each of the divided ECG artifact waveforms, and performing averaging. Potential 0
The waveform is divided into element waveforms according to the following time, and the amplitude and the duration are normalized for each element waveform. Another method of creating a normalized standard waveform is to divide the electrocardiogram time series and the original electroencephalogram time series recorded simultaneously with the electroencephalogram for each electrocardiogram waveform cycle, extract each normalization parameter from the divided electrocardiogram waveform, and Normalize each of the divided original brain wave time series using the normalization parameter of, and add and average the normalized original brain wave time series by synchronizing the vertex time,
The waveform obtained by the averaging is divided into element waveforms at the time when the potential becomes 0, and the amplitude and the duration are normalized for each element waveform.
【０００７】波形変動特性を考慮した心電図アーチファ
クト推定時系列の作成は、正規化標準波形の相似波形を
作成し、相似波形と原脳波時系列との相関を計算し、こ
の相関の最も高い相似波形の相似パラメータから求める
ことができる。また、波形変動特性を考慮した心電図ア
ーチファクト推定時系列の他の作成方法は、正規化標準
波形を前記正規化パラメータによって逆正規化して求め
ることを特徴とする。相似波形の相似パラメータは、分
割した波形毎の各々の要素波形の、持続時間、頂点時刻
及び振幅である。さらに、正規化標準波形は、心電図ア
ーチファクト波形の測定毎に、心電図アーチファクト波
形の正規化標準波形を求め、正規化標準波形を重み付き
で既使用中の正規化標準波形に加算平均して更新するこ
とを特徴とする。In order to create an ECG artifact estimation time series in consideration of waveform fluctuation characteristics, a similar waveform of a normalized standard waveform is created, a correlation between the similar waveform and the original brain wave time series is calculated, and a similar waveform having the highest correlation is calculated. From similarity parameters of Further, another method of creating an ECG artifact estimation time series in consideration of waveform variation characteristics is characterized in that a normalized standard waveform is inverse-normalized using the normalization parameter. The similarity parameter of the similar waveform is the duration, the peak time, and the amplitude of each element waveform for each divided waveform. Further, the normalized standard waveform obtains a normalized standard waveform of the ECG artifact waveform every time the ECG artifact waveform is measured, and adds and averages the normalized standard waveform with the weighted normalized standard waveform and updates the normalized standard waveform. It is characterized by the following.
【０００８】上記構成によれば、心電図アーチファクト
波形の正規化標準波形を、原脳波時系列または同時記録
した心電図時系列から求めるから、正確な波形形状把握
が成された心電図アーチファクト正規化標準波形を得る
ことができる。正確な心電図アーチファクト正規化標準
波形を用い、要素波形毎に相似係数法または逆正規化法
に基づいて原脳波時系列から心電図アーチファクト推定
時系列を得るようにすれば、心電図アーチファクト個々
の変動特性を含んだ正確な心電図アーチファクト推定時
系列を得ることができる。原脳波時系列から正確な心電
図アーチファクト推定時系列を差し引くようにすれば、
脳波成分のみを抽出することができる。さらに、本発明
によれば、正確な脳波測定が可能になると共に、これま
での脳波測定方法では実現できなかった遠隔電場誘発脳
電位の正確な頭上マップの作成や脳波活動量（脳電位）
の絶対値の測定も可能になる。また、正規化標準波形
を、心電図アーチファクト波形の測定毎に更新するの
で、実時間処理など逐次的に脳波データの処理を行う場
合に、より高度な心電図アーチファクト除去が可能とな
る。According to the above configuration, the normalized standard waveform of the electrocardiogram artifact waveform is obtained from the original electroencephalogram time series or the simultaneously recorded electrocardiogram time series, so that the standardized electrocardiogram artifact standard waveform whose accurate waveform shape is grasped is obtained. Obtainable. By using an accurate ECG artifact normalized standard waveform and obtaining an ECG artifact estimation time series from the original EEG time series based on the similarity coefficient method or the inverse normalization method for each element waveform, the variation characteristics of each ECG artifact can be obtained. An accurate ECG artifact estimation time series including the above can be obtained. By subtracting the accurate ECG artifact estimation time series from the EEG time series,
Only brain wave components can be extracted. Further, according to the present invention, accurate electroencephalogram measurement becomes possible, and an accurate overhead map of a remote electric field-induced brain potential and an electroencephalographic activity (brain potential) which cannot be realized by the conventional electroencephalogram measurement methods.
Can also be measured. Further, since the normalized standard waveform is updated every time the electrocardiogram artifact waveform is measured, a more advanced electrocardiogram artifact can be removed when the electroencephalogram data is processed sequentially such as in real time.
【０００９】[0009]
【発明の実施の形態】以下、本発明の脳波記録処理方法
の実施の形態を、図面に基づいて詳細に説明する。脳波
の記録は、国際１０−２０法に従って設置された頭皮上
の電極と、脳電位の影響が及ばない左手に設置した基準
電極との電位差を記録することで行った。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the brain wave recording processing method of the present invention will be described below in detail with reference to the drawings. The recording of the electroencephalogram was performed by recording the potential difference between an electrode on the scalp installed according to the international 10-20 method and a reference electrode installed on the left hand that was not affected by brain potential.
【００１０】心電図アーチファクトの除去の全体手順
は、（ａ）記録された原脳波時系列から、この原脳波時
系列に混入した心電図アーチファクト波形の正規化標準
波形を作成し、（ｂ）この心電図アーチファクト正規化
標準波形を用いて、原脳波時系列から波形変動特性を伴
った心電図アーチファクト推定時系列を作成し、（ｃ）
心電図アーチファクト推定時系列を原脳波時系列から差
し引き、脳波時系列成分のみを抽出する、段階から成
る。上記（ａ）、（ｂ）、（ｃ）の手順を以下に順番に
説明する。The general procedure for removing the electrocardiographic artifact is as follows: (a) From the recorded original electroencephalogram time series, a normalized standard waveform of the electrocardiographic artifact mixed in the original electroencephalogram time series is created; Using the normalized standard waveform, create an ECG artifact estimation time series with waveform fluctuation characteristics from the original brain wave time series, and (c)
Subtracting the electrocardiogram artifact estimation time series from the original electroencephalogram time series and extracting only the electroencephalogram time series component. The procedures (a), (b) and (c) will be described below in order.
【００１１】（ａ）正規化標準波形の作成 正規化標準波形の作成法には２つの方法がある。一つ
は、処理対象である脳波時系列の情報のみを用いた同期
加算平均による方法、もう一つは、同時記録した心電図
の情報を用いる方法である。(A) Creation of normalized standard waveform There are two methods for creating a normalized standard waveform. One is a method based on synchronous averaging using only information on the electroencephalogram time series to be processed, and the other is a method using simultaneously recorded electrocardiogram information.
【００１２】最初に、同期加算平均による方法を説明す
る。図１は、本発明の同期加算平均法による正規化標準
波形の作成方法を示す図である。図１（Ａ）に示すよう
に、頭部外基準電極法により記録した原脳波時系列ｙ
（ｔ）は、心電図波形と脳波が重畳しているが、心電図
波形が支配的であり、心電図アーチファクト波形の最大
振幅時刻、すなわちＲ波頂点時刻を検出する。原脳波時
系列ｙ（ｔ）のｋ個目の頂点時刻をｔp （ｋ）とし、そ
の時刻より２００ｍｓさかのぼった時刻から、次の頂点
時刻ｔP （ｋ＋１）より２００ｍｓ前までの波形を一つ
の心電図アーチファクト波形と定義し、図１（Ｂ）に示
すように、これらを一つの頂点時刻に同期させてそろ
え、次の加算平均式によって加算平均を行うことで脳波
の影響を相殺し、図１（Ｃ）に示すように、心電図アー
チファクト加算平均波形ｙ* （ｔ）を得る。First, a method based on synchronous averaging will be described. FIG. 1 is a diagram showing a method for creating a normalized standard waveform by the synchronous averaging method of the present invention. As shown in FIG. 1 (A), the original brain wave time series y recorded by the extra-head reference electrode method
In (t), the electrocardiogram waveform and the brain wave are superimposed, but the electrocardiogram waveform is dominant, and the maximum amplitude time of the electrocardiogram artifact waveform, that is, the R wave peak time is detected. The k-th vertex time of the original EEG time series y (t) and t p (k), from the time of going back 200ms from that time, of one waveform of than the next vertex time t P (k + 1) before 200ms An electrocardiogram artifact waveform is defined, and as shown in FIG. 1 (B), these are synchronized in synchronization with one vertex time, and the averaging is performed by the following averaging equation to cancel the effect of the electroencephalogram. As shown in (C), an electrocardiogram artifact addition average waveform y * (t) is obtained.
【００１３】[0013]
【数１】 (Equation 1)
【００１４】続いて、得られた心電図アーチファクト加
算平均波形の振幅と持続時間を規格化し、心電図アーチ
ファクトの正規化標準波形を作成する。加算平均波形ｙ
* （ｔ）を電位が０となる時刻によって分割し、それぞ
れの波形をＰ波、Ｑ波、Ｒ波、Ｓ波、Ｔ１波、Ｔ２波と
する。分割された個々の波形に対して、振幅を１に、各
要素波形の頂点時刻を境に前後の持続を１に正規化し、
図１（Ｄ）に示すように、正規化標準波形ｘ（τ）を得
る。心電図アーチファクト波形は、心臓の心房、心室そ
れぞれの動きに起因するため、要素波形毎に変動特性も
異なる。そのため、心電図アーチファクト波形を電位０
となる時刻によって要素波形に分割し、処理を行うこと
によって、高精度の心電図アーチファクト除去が可能に
なる。Subsequently, the amplitude and the duration of the obtained averaged waveform of the electrocardiogram artifact are normalized to create a normalized standard waveform of the electrocardiogram artifact. Averaging waveform y
* (T) is divided according to the time when the potential becomes 0, and the respective waveforms are P, Q, R, S, T1, and T2 waves. For each of the divided waveforms, the amplitude is normalized to 1 and the duration before and after the peak time of each element waveform is normalized to 1,
As shown in FIG. 1D, a normalized standard waveform x (τ) is obtained. Since the electrocardiogram artifact waveform is caused by the movements of the atrium and ventricle of the heart, the fluctuation characteristics are different for each element waveform. Therefore, the electrocardiogram artifact waveform is changed to potential 0
By dividing the waveform into elemental waveforms according to the time and performing the processing, it is possible to remove the electrocardiogram artifact with high accuracy.
【００１５】次に、脳波記録と同時に記録した心電図の
情報を用いる正規化標準波形の作成方法を説明する。図
２は、本発明の脳波記録と同時に記録した心電図の情報
を用いる正規化標準波形の作成方法を示す図である。図
２（Ａ）に示すように、頭部外基準記録脳波時系列ｙ
（ｔ）と同時記録した心電図ｕ（ｔ）より、個々の心電
図波形を抜き出す。個々の心電図波形より、図２（Ｂ）
に示すように、０電位を基準として波形を分割し、それ
ぞれの要素波形から振幅に関するパラメータ〔Ｈ
p （ｋ），ＨQ （ｋ），ＨR （ｋ），ＨS （ｋ），ＨT1
（ｋ），ＨT2（ｋ））と、持続に関するパラメータ（Ｄ
P f （ｋ），ＤQ f （ｋ），ＤR f （ｋ），Ｄ
S f （ｋ），ＤT1 f （ｋ），ＤT2 f（ｋ），Ｄ
P b （ｋ），ＤQ b （ｋ），ＤR b （ｋ），Ｄ
S b （ｋ），ＤT1 b （ｋ），ＤT2 b （ｋ）〕を抽出す
る。図２（Ｃ）に示すように、これらのパラメータを用
いて脳波時系列ｙ（ｔ）を正規化し、振幅と持続に関す
る変動を抑えた脳波時系列ｙ**（τ）を得る。この脳波
時系列ｙ**（τ）を加算平均することによって、図
（Ｄ）に示す正規化標準波形ｘ（τ）を得る。Next, a method of creating a normalized standard waveform using the information of the electrocardiogram recorded simultaneously with the electroencephalogram recording will be described. FIG. 2 is a diagram showing a method for creating a normalized standard waveform using information of an electrocardiogram recorded simultaneously with the electroencephalography according to the present invention. As shown in FIG. 2A, the extra-head reference recording brain wave time series y
Individual electrocardiogram waveforms are extracted from the electrocardiogram u (t) recorded simultaneously with (t). From each ECG waveform, Fig. 2 (B)
As shown in FIG. 7, the waveform is divided based on the zero potential, and the parameter [H
p (k), H Q (k), H R (k), H S (k), H T1
(K), H T2 (k)) and a parameter (D
P f (k), D Q f (k), D R f (k), D
S f (k), D T1 f (k), D T2 f (k), D
P b (k), D Q b (k), D R b (k), D
S b (k), D T1 b (k), D T2 b (k)]. As shown in FIG. 2 (C), these parameters are used to normalize the electroencephalogram time series y (t) to obtain an electroencephalogram time series y ** (τ) in which fluctuations in amplitude and duration are suppressed. By adding and averaging this brain wave time series y ** (τ), a normalized standard waveform x (τ) shown in FIG.
【００１６】 （ｂ）心電図アーチファクト推定時系列の作成 次に、心電図アーチファクト推定時系列の作成について
説明する。個々の心電図アーチファクト波形は、その持
続時間と振幅にばらつきが大きいため、それぞれの要素
波形毎に変動特性を考慮した心電図アーチファクト推定
時系列を作成することによって、心電図アーチファクト
推定時系列の精度が向上する。アーチファクト推定時系
列の作成方法には、相似係数を用いる方法と、心電図情
報を用いた逆正規化による方法の二つがある。(B) Creation of ECG Artifact Estimation Time Series Next, creation of an ECG artifact estimation time series will be described. Since the individual ECG artifact waveforms vary greatly in their duration and amplitude, the accuracy of the ECG artifact estimation time series is improved by creating an ECG artifact estimation time series in consideration of the variation characteristics for each element waveform. . There are two methods for creating an artifact estimation time series, a method using similarity coefficients and a method using inverse normalization using electrocardiogram information.
【００１７】最初に、相似係数を用いる方法を説明す
る。図３は、本発明の相似係数を用いた心電図アーチフ
ァクト推定時系列の作成方法を示す図である。相似係数
を用いた方法は、持続の推定と振幅の推定という二つの
段階を踏む。図３に示すように、始めに、正規化標準波
形ｘ（τ）に対して相似係数を導入し、相似波形を作成
する。相似波形は、分割したＰ波、Ｑ波、Ｒ波、Ｓ波、
Ｔ１波、Ｔ２波のそれぞれの要素波形に対して作成す
る。相似波形の作成は、波形振幅が最も大きく、その変
動も最も大きいＲ波部分から行い、続いてその両隣のＱ
波とＳ波、Ｐ波とＴ１波、最後にＴ２波の順で行う。Ｒ
波部分について説明すると、Ｒ波部分の正規化標準波形
に対して、持続時間を変化させるための相似パラメータ
αR （ｋ）とβR （ｋ）、及びＲ波部分の頂点時刻ｌR
（ｋ）を導入し、Ｒ波に対する相似波形ｓR （ｔ）を下
記式によって作成する。First, a method using a similarity coefficient will be described. FIG. 3 is a diagram showing a method for creating an electrocardiogram artifact estimation time series using similarity coefficients according to the present invention. The method using the similarity coefficient involves two steps, estimating the duration and estimating the amplitude. As shown in FIG. 3, first, a similarity coefficient is introduced into the normalized standard waveform x (τ) to create a similar waveform. Similar waveforms are divided P wave, Q wave, R wave, S wave,
It is created for each component waveform of T1 wave and T2 wave. The similar waveform is created from the R-wave portion where the waveform amplitude is the largest and the variation is the largest.
Waves and S waves, P waves and T1 waves, and finally T2 waves. R
To explain the wave portion, similarity parameters α R (k) and β R (k) for changing the duration, and the vertex time l R of the R wave portion, with respect to the normalized standard waveform of the R wave portion
(K) is introduced, and a similar waveform s R (t) for the R wave is created by the following equation.
【００１８】[0018]
【数２】 (Equation 2)
【００１９】この相似波形ｓR （ｔ）と原脳波時系列ｙ
（ｔ）との間で相似係数を計算し、その時の相似パラメ
ータαR （ｋ），βR （ｋ），ｌR （ｋ）を求める。相
似係数の計算は、下記の式によって行う。This similar waveform s R (t) and the original brain wave time series y
A similarity coefficient is calculated with respect to (t), and similarity parameters α R (k), β R (k), and l R (k) at that time are obtained. The calculation of the similarity coefficient is performed by the following equation.
【００２０】[0020]
【数３】 (Equation 3)
【００２１】上記式中、バーｓ及びバーｙを、明細書で
はそれぞれｓm ，ｙm と表示する。ｓm ，ｙm はｙ
（ｔ）とＳR （ｔ）それぞれの相似係数計算区間におけ
る平均値を表す。［数３］は、相似パラメータα
R （ｋ），βR （ｋ），ｌR （ｋ）を変化させて脳波時
系列との相関を計算し、その値が最も大きいものを求め
ることを意味している。［数３］を満たすときの相似波
形をｓR （ｋ，ｔ）とする。[0021] In the above formula, the bar s and bars y, the specification indicated as s m, y m, respectively. s m and y m are y
(T) and S R (t) represent average values in similarity coefficient calculation sections. [Equation 3] is a similarity parameter α
This means that the correlation with the brain wave time series is calculated by changing R (k), β R (k), and l R (k), and the one having the largest value is obtained. A similar waveform when satisfying [Equation 3] is defined as s R (k, t).
【００２２】続いて、得られた相似波形ｓR （ｋ，ｔ）
を用いて、振幅の推定を行う。振幅推定のためのパラメ
ータａR （ｋ）を導入し、原脳波時系列ｙ（ｔ）と相似
波形ｓR （ｋ，ｔ）の間の誤差が最も小さくなるよう
に、即ちSubsequently, the obtained similar waveform s R (k, t)
Is used to estimate the amplitude. A parameter a R (k) for amplitude estimation is introduced so that the error between the original brain wave time series y (t) and the similar waveform s R (k, t) is minimized, that is,
【数４】 によって係数ａR （ｋ）を決定する。係数ａR （ｋ）は
最小二乗法によって(Equation 4) Determines the coefficient a R (k). The coefficient a R (k) is calculated by the least squares method.
【数５】 を求めることによって一意に求めることができる。これ
によってＲ波部分の心電図アーチファクト推定波形が得
られた。(Equation 5) Can be uniquely obtained by obtaining As a result, an estimated ECG artifact waveform of the R wave portion was obtained.
【００２３】同様の手順をＲ波部分の両隣にあるＱ波，
Ｓ波に対しても行い、続いてＰ波，Ｔ１波部分、最後に
Ｔ２の波部分の心電図アーチファクト推定波形を求め
る。Ｐ波，Ｑ波，Ｒ波，Ｓ波，Ｔ１波，Ｔ２波に対して
それぞれ求めた心電図アーチファクト推定波形を全ての
時間軸上で足し合わせることで、ｋ個目の心電図アーチ
ファクトに対する推定波形ｘ* （ｋ，ｔ）を得る。同様
にして、全てのｋにおいてｘ* （ｋ，ｔ）を得ることに
よって、心電図アーチファクト推定時系列を作成する。The same procedure is repeated for the Q waves on both sides of the R wave portion,
The process is also performed for the S wave, and subsequently, an estimated electrocardiogram artifact waveform of the P wave, T1 wave portion, and finally, the T2 wave portion is obtained. By adding the estimated ECG artifact waveforms obtained for the P, Q, R, S, T1, and T2 waves on all time axes, the estimated waveform x * for the k-th ECG artifact is obtained . (K, t) is obtained. Similarly, an electrocardiogram artifact estimation time series is created by obtaining x * (k, t) for all k.
【００２４】次に、心電図情報を用いた逆正規化による
心電図アーチファクト推定時系列の作成方法を説明す
る。図４は、本発明の心電図情報を用いた逆正規化によ
る心電図アーチファクト推定時系列の作成方法を示す図
である。上記に説明した、正規化標準波形の作成で抽出
した心電図アーチファクトの振幅に関するパラメータ
〔Ｈp （ｋ），ＨQ （ｋ），ＨR （ｋ），ＨS （ｋ），
ＨT1（ｋ），ＨT2（ｋ）〕と、持続に関するパラメータ
〔ＤP f （ｋ），ＤQ f（ｋ），ＤR f （ｋ），ＤS f
（ｋ），ＤT1 f （ｋ），ＤT2 f （ｋ），ＤP b （ｋ），
ＤQ b （ｋ），ＤR b （ｋ），ＤS b （ｋ），Ｄ
T1 b （ｋ），ＤT2 b （ｋ）〕を用いて、図４に示したよ
うに正規化標準波形ｘ（τ）の持続と振幅を変化させる
逆正規化の手順を踏むことで、ｋ個目の心電図アーチフ
ァクトに対する推定波形ｘ* （ｋ，ｔ）を得る。同様に
して、全てのｋにおいてｘ* （ｋ，ｔ）を得ることによ
って、心電図アーチファクト推定時系列を作成する。Next, a method of preparing an electrocardiogram artifact estimation time series by inverse normalization using electrocardiogram information will be described. FIG. 4 is a diagram showing a method for creating an ECG artifact estimation time series by inverse normalization using ECG information according to the present invention. The parameters [H p (k), H Q (k), H R (k), H S (k), and H p (k) related to the amplitude of the electrocardiographic artifact extracted in the creation of the normalized standard waveform described above.
H T1 (k), H T2 (k)], and parameters [D P f (k), D Q f (k), D R f (k), D S f ] related to the duration.
(K), D T1 f ( k), D T2 f (k), D P b (k),
D Q b (k), D R b (k), D S b (k), D
T1 b (k), D T2 b (k)], the inverse normalization procedure of changing the duration and amplitude of the normalized standard waveform x (τ) as shown in FIG. An estimated waveform x * (k, t) for the electrocardiogram artifact is obtained. Similarly, an electrocardiogram artifact estimation time series is created by obtaining x * (k, t) for all k.
【００２５】（ｃ）差し引き 以上の手順で作成した心電図アーチファクト推定時系列
を原脳波時系列ｙ（ｔ）から(C) Subtraction The time series of estimating the electrocardiogram artifact created by the above procedure is derived from the original electroencephalogram time series y (t).
【数６】 のごとく差し引くことで、心電図アーチファクトの除去
された処理脳波時系列ｚ（ｔ）を得る。(Equation 6) As a result, the processed electroencephalogram time series z (t) from which the electrocardiogram artifact is removed is obtained.
【００２６】図５は、本発明の脳波記録処理法によって
心電図アーチファクトが除去された脳波データを示す図
である。図５（Ａ）は、波形形状把握を伴った本発明方
法による結果で、図５（Ａ）において上から順に原脳波
時系列ｙ（ｔ）、心電図アーチファクト推定波形ｘ
* （ｋ，ｔ）、処理脳波時系列ｚ（ｔ）を表す。最下段
の処理脳波時系列ｚ（ｔ）中からは心電図アーチファク
トがほぼ完全に除去されているのが分かる。一方、図５
（Ｂ）は、従来の単純同期加算平均による除去法による
結果であり、特に心電図Ｒ波の部分に大きな残差が残っ
ている。したがって、波形形状把握を伴った本発明方法
によるアーチファクト除去精度が優れていることが分か
る。FIG. 5 is a diagram showing electroencephalogram data from which electrocardiogram artifacts have been removed by the electroencephalogram recording processing method of the present invention. FIG. 5 (A) shows the result of the method of the present invention with the waveform shape grasp. In FIG. 5 (A), the original brain wave time series y (t) and the electrocardiogram artifact estimated waveform x
* (K, t) represents a processed brain wave time series z (t). It can be seen that the electrocardiogram artifact is almost completely removed from the processing brain wave time series z (t) at the bottom. On the other hand, FIG.
(B) shows the result obtained by the conventional simple synchronous averaging elimination method. In particular, a large residual remains in the electrocardiogram R-wave portion. Accordingly, it can be seen that the accuracy of artifact removal by the method of the present invention with grasping the waveform shape is excellent.
【００２７】次に、正規化標準波形の更新方法について
説明する。全ての脳波データを一括して処理する方式に
おいては必要ないが、実時間処理など逐次的に脳波デー
タの処理を行いたい場合には、心電図アーチファクトの
波形変動特性を考慮して正規化標準波形の形状を更新す
ることで、より高度な心電図アーチファクト除去が可能
となる。図６は、本発明の正規化標準波形更新の概念を
示す図である。ｋ−１個目の心電図アーチファクト除去
に用いた正規化標準波形をｘ（ｋ−１，τ）とし、これ
にｋ個目に検出された心電図アーチファクト波形の振幅
と持続時間を規格化したものを重み付きの加算平均によ
って足しあわせることで、更新された心電図アーチファ
クトの正規化標準波形ｘ（ｋ，τ）を得る。Next, a method of updating the normalized standard waveform will be described. Although it is not necessary in the method of processing all the brain wave data collectively, if you want to process the brain wave data sequentially such as real-time processing, consider the waveform fluctuation characteristics of the ECG artifact Updating the shape enables more advanced removal of ECG artifacts. FIG. 6 is a diagram illustrating the concept of updating the normalized standard waveform according to the present invention. The normalized standard waveform used for removal of the (k−1) -th ECG artifact is x (k−1, τ), and the amplitude and duration of the k-th detected ECG artifact waveform are normalized. By adding by weighted averaging, an updated standardized waveform x (k, τ) of an electrocardiogram artifact is obtained.
【００２８】[0028]
【発明の効果】上記説明から理解されるように、本発明
の脳波記録処理方法によれば、脳波時系列から心電図ア
ーチファクトを高精度で除去することができ、高精度の
脳波測定が可能になる。また、本発明の脳波記録処理方
法によれば、脳電位の絶対量の測定、遠隔電場誘発脳電
位の正確な頭皮上マップの作成など、これまで困難とさ
れてきた脳波解析が可能となる。また、本発明の脳波記
録方法はコンピュータのソフトウエアによって実現され
るため、特別な装置を新たに製作する必要がなく、光磁
気デスクなどの電子媒体に記録された脳波データさえあ
れば、脳波解析ができるという利点もある。As will be understood from the above description, according to the electroencephalogram recording processing method of the present invention, an electrocardiogram artifact can be removed from an electroencephalogram time series with high accuracy, and highly accurate electroencephalogram measurement becomes possible. . Further, according to the electroencephalogram recording processing method of the present invention, it has become possible to perform electroencephalogram analysis which has been difficult so far, such as measurement of the absolute amount of brain potential, creation of an accurate scalp map of brain potential induced by a remote electric field. Further, since the electroencephalogram recording method of the present invention is realized by software of a computer, there is no need to newly manufacture a special device, and if there is only electroencephalogram data recorded on an electronic medium such as a magneto-optical desk, an electroencephalogram analysis is performed. There is also an advantage that can be.
【図１】この発明の同期加算平均法による正規化標準波
形の作成方法を示す波形図である。FIG. 1 is a waveform diagram showing a method of creating a normalized standard waveform by a synchronous averaging method of the present invention.
【図２】本発明の脳波記録と同時に記録した心電図の情
報を用いる正規化標準波形の作成方法を示す波形図であ
る。FIG. 2 is a waveform chart showing a method of creating a normalized standard waveform using information of an electrocardiogram recorded simultaneously with an electroencephalogram recording of the present invention.
【図３】本発明の相似係数を用いた心電図アーチファク
ト推定時系列の作成方法を示す波形図である。FIG. 3 is a waveform chart showing a method for generating an electrocardiogram artifact estimation time series using similarity coefficients according to the present invention.
【図４】本発明の心電図情報を用いた逆正規化による心
電図アーチファクト推定時系列の作成方法を示す波形図
である。FIG. 4 is a waveform chart showing a method for creating an ECG artifact estimation time series by denormalization using ECG information according to the present invention.
【図５】本発明の脳波記録処理法によって心電図アーチ
ファクトが除去された脳波データを示す波形図である。FIG. 5 is a waveform diagram showing electroencephalogram data from which electrocardiogram artifacts have been removed by the electroencephalogram recording processing method of the present invention.
【図６】本発明の正規化標準波形更新の概念を示す波形
図である。FIG. 6 is a waveform chart showing a concept of updating a normalized standard waveform of the present invention.
ｔp （ｋ） 心電図アーチファクトＲ波頂点時刻 ｙ（ｔ） 原脳波時系列 ｙ* （ｔ） 加算平均波形 ｙ* * （ｔ） 正規化した原脳波時系列 ｘ（τ） 正規化標準波形 ｘ* （ｋ，τ） 心電図アーチファクト推定波形 ｕ（ｔ） 心電図時系列 ｓ（ｋ、ｔ） 正規化相似波形 αT1（ｋ）、βT1（ｋ） 持続時間の相似パラメータ ＨR （ｋ）、ＨT1（ｋ） 振幅の正規化パラメータ ＤT1 f （ｋ）、ＤT1 b （ｋ） 持続時間の正規化パラ
メータ Ｐ，Ｑ，Ｒ、Ｓ、Ｔ１、Ｔ２ 要素波形t p (k) Electrocardiogram artifact R wave peak time y (t) Original brain wave time series y * (t) Averaged waveform y ** (t) Normalized original brain wave time series x (τ) Normalized standard waveform x * (K, τ) ECG artifact estimated waveform u (t) ECG time series s (k, t) Normalized similar waveform α T1 (k), β T1 (k) Similarity parameters of duration H R (k), H T1 (K) Normalization parameters of amplitude D T1 f (k), D T1 b (k) Normalization parameters of duration P, Q, R, S, T1, T2 Element waveform
フロントページの続き Ｆターム(参考） 4C027 AA02 AA03 CC02 FF03 FF07 GG00 GG01 GG02 GG07 GG10 HH02 HH08 Continued on the front page F term (reference) 4C027 AA02 AA03 CC02 FF03 FF07 GG00 GG01 GG02 GG07 GG10 HH02 HH08
Claims (7)
頭部外に設置した基準電極との間の電位差を測定する脳
波記録方法において、 （ａ）記録された原脳波時系列から、この原脳波時系列
に混入した心電図アーチファクト波形の正規化標準波形
を作成し、 （ｂ）この心電図アーチファクト正規化標準波形を用い
て、上記原脳波時系列から、波形変動特性を考慮した心
電図アーチファクト推定時系列を作成し、 （ｃ）上記原脳波時系列から上記心電図アーチファクト
推定時系列を差し引き、脳波時系列成分のみを抽出する
ことを特徴とする、脳波記録処理方法。1. An electroencephalogram recording method for measuring a potential difference between an electrode on the scalp and a reference electrode placed outside the head which is not affected by brain potential, comprising the steps of: A normalized standard waveform of an electrocardiogram artifact waveform mixed in the original electroencephalogram time series is created. (B) Using this electrocardiogram artifact normalized standard waveform, an electrocardiogram artifact estimation is performed from the above original electroencephalogram time series in consideration of waveform variation characteristics. (C) subtracting the electrocardiogram artifact estimation time series from the original electroencephalogram time series, and extracting only an electroencephalogram time series component;
波時系列を前記心電図アーチファクト波形の周期毎に分
割し、分割した各々の心電図アーチファクト波形の頂点
時刻を同期させて加算平均し、この加算平均して求めた
波形を電位０となる時刻によって要素波形に分割し、こ
の要素波形毎に振幅及び持続時間を正規化することを特
徴とする、請求項１に記載の脳波記録処理方法。2. Creating the normalized standard waveform, the original brain wave time series is divided for each cycle of the electrocardiogram artifact waveform, and the peak times of each of the divided electrocardiogram artifact waveforms are synchronized and averaged. The electroencephalogram recording processing method according to claim 1, wherein the waveform obtained by the averaging is divided into element waveforms according to a time at which the potential becomes 0, and the amplitude and the duration are normalized for each element waveform.
時記録した心電図時系列と前記原脳波時系列を心電図波
形周期毎に分割し、分割した心電図波形から各々の正規
化パラメータを抽出すると共に、この各々の正規化パラ
メータを用いて対応する各々の上記分割した原脳波時系
列を正規化し、この正規化した原脳波時系列を前記頂点
時刻を同期させて加算平均し、この加算平均して求めた
波形を電位０となる時刻によって要素波形に分割し、こ
の要素波形毎に振幅及び持続時間を正規化することを特
徴とする、請求項１に記載の脳波記録処理方法。3. The normalization standard waveform is created by dividing an electrocardiogram time series recorded simultaneously with an electroencephalogram and the original electroencephalogram time series for each electrocardiogram waveform cycle, and extracting respective normalization parameters from the divided electrocardiogram waveforms. At the same time, each of the divided original brain wave time series is normalized using the respective normalization parameters, and the normalized original brain wave time series is added and averaged by synchronizing the apex time, and the added and averaged. The electroencephalogram recording processing method according to claim 1, wherein the obtained waveform is divided into element waveforms according to the time when the potential becomes 0, and the amplitude and the duration are normalized for each element waveform.
チファクト推定時系列の作成は、前記正規化標準波形の
相似波形を作成し、この相似波形と前記原脳波時系列と
の相関を計算し、この相関の最も高い相似波形の相似パ
ラメータから求めることを特徴とする、請求項１に記載
の脳波記録処理方法。4. The method of generating an electrocardiogram artifact estimation time series in consideration of the waveform fluctuation characteristics includes creating a similar waveform of the normalized standard waveform, calculating a correlation between the similar waveform and the original brain wave time series, The brain wave recording processing method according to claim 1, wherein the brain wave recording processing method is obtained from a similar parameter of a similar waveform having the highest correlation.
チファクト推定時系列の作成は、前記正規化標準波形を
前記正規化パラメータによって逆正規化して求めること
を特徴とする、請求項３に記載の脳波記録処理方法。5. The electroencephalogram according to claim 3, wherein the generation of the electrocardiogram artifact estimation time series in consideration of the waveform fluctuation characteristic is performed by denormalizing the normalized standard waveform using the normalization parameter. Recording processing method.
分割した波形毎の各々の要素波形の、持続時間、前記頂
点時刻及び振幅であることを特徴とする、請求項１に記
載の脳波記録処理方法。6. The electroencephalogram recording process according to claim 1, wherein the similarity parameters of the similar waveform are a duration, the peak time, and an amplitude of each element waveform for each of the divided waveforms. Method.
ァクト波形の測定毎に、この心電図アーチファクト波形
の正規化標準波形を求め、この正規化標準波形を重み付
きで既使用中の正規化標準波形に加算平均して更新する
ことを特徴とする、請求項１に記載の脳波記録処理方
法。7. The normalization standard waveform is obtained by obtaining a normalization standard waveform of the electrocardiogram artifact waveform every time the electrocardiogram artifact waveform is measured, and weighting the normalization standard waveform to an already used normalization standard waveform. 2. The brain wave recording processing method according to claim 1, wherein the update is performed by averaging.
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