Muc luc A.Li m u B.Ni dung chnh 1.t vn 1.1.EEG l g? 1.2.Ti sao phi thu nhn tn hiu EEG? 2.Ngun gc ca tn hiu EEG 2.1.Cu trc gii phu v chc nng ca no 2.2.Cu to chc nng ca t bo thn kinh 2.3.Cch thc truyn tn hiu ca noron thn kinh 2.4.in th ngh v in th hot ng ca no 2.5 Ngun gc ca tn hiu in no 3 Thu nhn v o c tn hiu in no 3.1V tr t in cc chun 3.2 Thu nhn tn hiu in no 4.Cc dng tn hiu in no 4.1.Cc dng tn hiu in no theo tn s 4.2.Cc bin th bnh thng 4.3.Cc dng sng phc hp-dng bnh l 4.4.Tn hiu EEG bnh thng khi thc 4.5.Tn hiu EEG khi ng 5.Cc nh hng tc ng ln no ( nhiu) 6.Phng php x l tn hiu in no 6.1.Bin i Fuorier 6.2.Bin i sng 6.3.nh v EEG 7.C s ly thuyt bin i FFT 8.Ve ph tin hiu EEG 9.Ti liu tham kho C.Kt lunA.LI M U Sc khe l vn qu nht ca con ngi. Khi x hi pht trin th nhu cu v chm sc sc khe, nhu cu s dng cc dch v y t ca con ngi ngy cng i hi cao hn. Do vy cc thit b y t v k thut mi phi pht trin h tr trong vic chn on, quan st, theo di v x l cc chiu trng bt thng v bnh tt ca con ngi. Tn hiu y sinh hc cha ng lng thng tin v cng phong ph rt c ch cho con ngi cho nn vic ghi li v x l cc tn hiu y sinh hc c ngha rt quan trng. ti Tm hiu in no EEG bao gm vic tm hiu cch thc b no pht sinh ra tn hiu, phng php ghi li cc dng tn hiu pht ra t no, phng php x l tn hiu ny nh th no, cc dng sng c ngha ra sao?... Do vy em a chon tai tin hiu in nao tim hiu. Em xin cm n thy TS. Ha Hoang Kha gip em trong qu trinh thc hin an nay.B.NI DUNG CHNH1.t vn 1.1.EEG l g?EEG l in th hot ng ca v no pht ra. EEG c pht hin bi Berger nm 1924 bng 1 dng c o dng in vi 1 in cc b mt trn u con trai ng v ghi li c 1 mu nhp nhng nhng dao ng in. Tn hiu ny l phn hi in sinh hc ngay tc khc ca t bo no. Ngy nay, ngi ta cho rng tn hiu EEG ging nh nh tn hiu EEG ly t lng cc trong lp t bo hnh chp. Rt nhiu t bo hnh chp v si thn kinh ca n c sp xp thng ng. S sp xp ny c a ra 1 dendro-somatic lng cc hoc in th l ci dao ng do tc nhn kch thch gy ra.1.2. Ti sao phi thu nhn tn hiu EEG?No b ca con ngi l mt t chc phc tp, tinh vi nht ca h thn kinh. Thng qua cc gic quan nh mt, tai, da, b no tip thu cc thng tin v th gic, thnh gic, xc gic... t nhn thc ra i tng, x l v giai p thng tin qua cc hnh thc vn ng. Do vy b no gi vai tr quan trng trong hot ng ton din, a dng ca con ngi, gip con ngi thch ng vi cc hon cnh x hi. Ngy nay, khi th gii ngy cng pht trin th cc bnh v no cng ngy cng pht trin nh: cc bnh v ng kinh, vim no,u no .. Do vy, vic thu nhn v x l tn hiu in no s gip chng ta chn on chnh xc c cc bnh v no. V th, cc bnh nhn no s c c hi c cu cha nhiu hn.2. Ngun gc ca tn hiu EEG:Hans Benger (1873 1941) mt nh sinh vt hc v tm thn hc ngi c c ghi nhn l ngi u tin ghi li EEG trn con ngi. Ci tn EEG cng l do ng t. y c nh gi l mt pht minh ng kinh ngc, ng ch v quan trng nht trong lch s thn kinh hc lm sang.2.1: in th ngh v in th hot ng ca no:No con ngi c xp x 100 t nron hoc t bo thn kinh. T bo c th ngi gm nhiu nucleus, nhnh c gi l ng processes. T bo thn kinh di nht l si trc axon l t bo c th mang tn hiu ra ngoi. Mt axon c th ko di t h thng nron trung tm CNS n ngn ci hoc ngn tr v c th ni c vi c. 2.4.1.in th mng ngh trng thi ngh, mt trong v ngoi mng nron c s phn b 3 ion Na+, K+ v Cl- khc nhau (mmol/L): S phn b ny do 2 c ch to nn:Do bm Na+ - K+: cn gi l bm sinh in nm trn mng t bo. Mi ln bm hot ng, 3 ion Na+ c a ra ngoi trong khi ch c 2 ion K+ i vo bn trong.Do s khuch tn ca Na+ v K+ qua mng t bo. Na+ c khuynh hng i vo bn trong cn K+ i ra ngoi.Do s phn b khc bit m mt trong mng nron c in th thp hn mt ngoi 70mV v c gi l in th ngh (-70mV). 2.4.2. in th hot ng:L s thay i rt nhanh ca in th mng t bo khi mng t bo b kch thch.in th hot ng xy ra khi 1 n ron truyn thng tin t 1 t bo ny sang t bo khc. in th hot ng l 1 s bng n ca hot ng in ci c thit lp bi 1 dng kh cc. Ngha l c 1 tc nhn kch thch lm cho in th ngh tng qua 0mV. Khi s kh cc ti -55mV, gii hn ca 1 n ron, n s pht ra 1 in th hot ng. Nu khng ti c nc ngng gii hn ny th khng c in th hot ng. Hn na, khi t c ngng, mt in th hot ng ca 1 i lng c nh lun c pht ra. Nn vi bt k n ron no, ln in th hot ng l ging nhau.2.5 Ngun gc tn hiu in no:V no l ngun gc ca cc hot ng in ca no thu c t b mt ca da u, cc dng khc nhau ca hot ng in v dn ti trng in th c to ra bi cc t bo thn kinh v no.3. Thu nhn v o c tn hiu in no (recording and measurement EEG signal):3.1. V tr t in cc chun:Hip hi quc t v sinh l thn kinh lm sng v in no a ra chun t in cc cho 21 in cc(gm c in cc ti di tai) c ch ra hnh di y.

H thng t in cc ghi 10-20 quc t (international 10-20 system) ghi in no. C 3 ng ni chnh: 1- n 2 ng tai ngoi (thc ra l ngay trc tai - preauricular points), 2- ni gc mi vi chm ngoi, c 2 ng ni ny u i qua nh s, v 3- ng chu vi ca s kt ni 2 im tn cng nht trn s. Ba ng ny c chia theo t l 10-20-20-20-20-10%, theo c trc trc giao (2 ng vung gc), ln theo vng trn chu vi, theo kiu chia i cc im ni. Khi nghin cu gic ng, c th ngi ta khng dng ht cc v tr ghi ny, v ch t in cc mt s v tr: trn hnh v l nhng ch c vng trn en.

3.2 Phng php thu nhn tn hiu in no: Cc h thng o tn hiu EEG gm s lng ln cc in cc tinh vi, cc mch khuch i vi sai (cho mi knh), b lc v ng h ghi c mi kim ch. Tn hiu EEG a knh c ghi li ln tm giy nhn hoc giy c li. Ngay sau , h thng o tn hiu EEG ny c tung ra th trng, cc nh nghin cu bt u tm kim h thng c my tnh ha, h thng ny s ha v lu tr tn hiu. Do vy phn tch tn hiu EEG, ban u phi hiu rng tn hiu c chuyn sang dng s. S ha tn hiu bao gm cc bc: ly mu, lng t ha, v m ha tn hiu. Khi s cc c s dng cng tng th s lng d liu cng ln, tc s bt m ha tn hiu cng nhiu hn. H thng c my tnh ha cho php thit lp cc kiu khc nhau, m phng v ly mu tn s v trong mt s trng hp tch hp c cc cng c x l tn hiu n gin hoc hin i gip nng cao hiu qu qu trnh x l tn hiu. Qu trnh bin i t tn hiu EEG tng t sang dng s c thc hin bi b chuyn i s tng t a knh. Di tn hiu qu cho tn hiu EEG xp x 100Hz. Do tn s ly mu nh nht l 200 mu/s tha mn qui tc Nyquist l ly mu tn hiu EEG. Trong mt s ng dng cc hot ng ca no c quan st i hi phn gii cao hn tn s ly mu c th ln ti 2000 mu/s. duy tr thng tin chn on th qu trnh lng t ha tn hiu thng thng phi rt tt. Cc h thng ghi tn hiu EEG ph bin s dng cc mu tn hiu di dng 16bits. Cc in cc ghi in tim c chnh xc cao ch yu c s dng thu thp d liu cht lng cao. Cc loi in cc c s dng trong h thng ghi tn hiu in no nh: in cc dng mt ln (dng gel) in cc c th s dng nhiu ln (vng, bc, thp hoc tin) in cc kp v chp u in cc c nhng mn in cc dng kim Khi ghi a knh vi s lng ln ca cc in cc, th in cc dng m chp thng c dng. Thng thng in cc dng m chp gm a Ag AgCl c ng knh nh hn 3mm, vi cc cc linh hot c th gn vo b khuch i. in cc kim phi c cm di v no vi su nh nht c th. Tr khng cao gia in cc v da u cng nh cc in cc c tr khng cao cng c th dn ti mo dng tn hiu. Do vy cc my ghi in no thng mi thng thng c trang b b phn theo di tr khng. m bo vic ghi tn hiu in no chnh xc, tr khng ca in cc phi nh hn 5k , tt nht l 1k cn bng vi cc in cc khc trong m. Tng ng vi tng cu trc lp v xon ca no s phn b cc in cc ln da ph hp.4.Cc dng tn hiu in no: 4.1. Cc dng tn hiu in no theo tn s:Ngi ta nhn thy trn bn ghi EEG bnh thng, nhp ca cc sng in no gm c vi loi. Nhp sng d thy nht c Berger t tn cho l nhp hay sng alpha (alpha wave, alpha rhythm). Cc sng ny thng c bin khong 50 microvolts (mc d cng c th giao ng t 5 ti 100 microvolts) v xut hin 8-13 ln trong 1 giy (8-13 Hertz). Sng ny thy r nht phn pha sau ca no ngi, vn l ni x l cc tn hiu th gic, tc l vng chm (occipital region). ). V vy, i khi ngi ta cn gi nhp alpha l nhp tri pha sau (the posterior-dominant rhythm). Sng alpha tr nn r nht khi ta nhm mt li. N b trit tiu khi ta m mt. Nh vy sng alpha l du hiu cho bit no ang tnh trng khng ch (inattentive brain), v ang ch c kch thch. Thc t l c mt vi tc gi gi n l nhp ch t ("waiting rhythm"). Ni mt cch hnh nh, ta c th hnh dung n nh l mt ngi ang st rut ch i, vi biu hin nhp 2 chn hay g ngn tay trn mt bn, ch i c vng ng dy lm mt vic g . Khi m khng cn phi ch i na (bng cch m mt hay tnh nhm trong u), th sng alpha cng bin mt. cc phn vng trn ca no (frontal region), c mt sng nhanh hn, gi l sng beta (beta wave). N xut hin 13-35 ln trong 1 giy, nhng c bin di 30 microvolts.

Betal sng 4-35 Hz, thng c in th thp (5-30 mV), sng beta c bin cao nht l phn pha trc ca no. Dng sng ny thng chim di 20% ca ton b bn ghi, nu n chim s lng nhiu hn th ln bn in no bt thng hoc l phn nh tc dng ca thuc.

Cn mt loi sng khc na, gi l sng theta (theta wave), th c tn s 4-8 Hz, v thng thy khi ang trong tnh trng bun ng v trong cc giai on ng nng (light stages of sleep).

Dng sng delta (delta wave) th him khi ghi c trn ngi bnh thng ang thc tnh, nhng bnh thng vn thy khi ng su (deep sleep) hoc vo lc tnh gic ca tr nh.

Sng delta l sng c bin cao nht trong tt c cc sng in no. Ni chung nu n xut hin trn mt ngi ln (tr khi ang ng) th chng t no c vn no : v d u no, ng kinh, tng p lc nt s, khim khuyt v tr tu, hay hn m. Khi xut hin, th n c khuynh hng thay th cho nhp alpha. C sng beta ln sng delta u khng b nh hng bi m mt hay nhm mt. Chi tit: Tn s ca sng tc l s lng ca sng trong mt n v thi gian, y l trong 1 giy. Tn s ca cc sng in no vo khong t 0,5/giy cho ti vi trm/giy. Tuy nhin cc my ghi EEG thng ch ghi c cc sng c tn s di 26/giy. Cc sng c phn bit bi tn s, v c chia thnh cc loi sau: Alpha l nhng sng c tn s trong khong t 7,5 ti 13 sng/giy (Hz). Thng thy r alpha nht l cc vng pha sau ca u, c 2 bn, nhng thng bn bn cu u th th c bin (chiu cao) cao hn. Alpha thng r ln khi nhm mt v th gin, v bin i khi m mt hoc thc tnh cnh gic bi bt c c ch no (suy ngh, m). y l nhp sng ch yu thy c trn ngi ln bnh thng v th gin sng hin din trong hu ht cc thi k ca cuc i, nht l khi trn 30 tui, khi y sng ny chim u th trn ng ghi EEG lc ngh ngi. Beta l nhng sng nhanh. Tn s ca n l t 14 Hz tr ln. Sng beta thng thy c 2 bn cu, phn b i xng hai bn, v r nht l vng trn. Sng s ni bt ln khi dng thuc an thn gy ng, nht l khi dng benzodiazepines v barbiturates. Sng c th mt hoc suy gim vng c tn thng v no. Nhp beta thng c coi l nhp bnh thng. N l nhp chim u th nhng bnh nhn ang thc tnh cnh gic hc lo s, hoc khi m mt.Theta l nhng sng c tn s t 3,5 ti 7,5 Hz, v c xp vo loi sng chm. N c coi l bt thng nu thy ngi ln ang tnh to, nhng li coi l hon ton bnh thng tr di 13 tui v ang ng. Cng c th thy theta to thnh 1 vng bt thng cc b trn nhng ni c tn thng di v cc b. C th thy sng theta lan ta trong cc bnh l no lan ta hay bnh no do chuyn ha, hoc bnh l ng gia nm su (deep midline disorders) hoc trong mt s trng hp no nc (hydrocephalus).Delta l nhng sng c nhp t 3 Hz tr xung. N c xu hng l nhng sng c bin cao nht v l nhng sng chm nht. N hon ton c coi l bnh thng v l sng u th tr s sinh di 1 tui v giai on 3 hoc 4 (stages 3 and 4) ca gic ng. N c th xut hin cc b khi c tn thng di v v phn b rng khp khi c tn thng lan trn, trong bnh no do chuyn ha (metabolic encephalopathy), bnh no nc (hydrocephalus) hay tn thng ng gia trong su (deep midline lesions). N thng tri nht vng trn ngi ln (v d FIRDA - Frontal Intermittent Rhythmic Delta sng delta c nhp cch hi vng trn) v phn b tri cc vng pha sau trn tr em (v d OIRDA - Occipital Intermittent Rhythmic Delta - sng delta c nhp cch hi vng chm). 4.2. Cc bin th bnh thng:C mt s sng hoc hnh dng sng t khi thy xut hin, nhng chng khng c ngha bt thng hay bnh l. Nhng chng c th lm cho ta din gii nhm ln v bn ghi in no . Trong cc bin th bnh thng ny, thng gp nht l nhp mu (mu rhythm), bin th tm thn vn ng (psychomotor variant), cc sng lambda, POSTS, cc thoi (spindles), sng ca nh s (vertex waves) v phc b K (K Complexes).a)Lambda v POSTS:

Lambda v POSTS tng t nhau v hnh dng v c hnh tam gic. Chng xut hin khu vc pha sau v cn xng hai bn. POSTS l biu hin ca sng dng thong qua chm ca gic ng (positive occipital transients of sleep) v xut hin trong gic ng giai on 2. Lambda xut hin bnh nhn tnh to khi nhn trng trng vo mt b mt trng. C hai loi ny u l dng sng bnh thng, v xut hin n c, hay ko di, hay thnh mt chui ngn.b)Phc b K: phc b K (K Complexes) xut hin khi ang ng m b nh thc ta thy n khi c kch thch m thanh hay cc kch thch khc khi bnh nhn ang ng. Tip sau phc b K thng c p ng thc tnh c th l mt chui cc sng theta c bin cao. Tip sau phc b K, in no li cho thy biu hin gic ng, hoc trng thi thc tnh.c)Sng V (V Waves): Sng V xut hin vng cnh dc gia (parasaggital areas) ca 2 bn cu v c dng mt sng nhn (sharp waves) hoc thm ch l dng gai (spikes), khu vc lng nh (biparietal regions), tc l nh u (vertex), vi pha ngc o nhau ti ng gia, nhng o trnh bc ngang (tranverse montages) hoc nh s trn cc o trnh trc - sau (front-to-back). Cc sng ny thy c trong gic ng giai on 2 (stage 2 sleep), cng vi cc thoi (spindles), phc b K, POSTS, v.v...d)Hot ng in MU (MU activity):

hot ng in Mu l dng nhp trong cc sng c hnh nhn ging nh hnh ro chn (wicket fence) vi nh nhn v chn cong trn. Gia 2 knh, nhp Mu c th c pha nghch o nhau. Tn s ni chung vo khong mt na ca hot ng in nhanh hin c.e)Bin th tm thn vn ng (Psychomotor Variant):L loi nhp him gp, n xut hin ging nh l s ha nhp ca 2 hay nhiu nhp c bn vo vi nhau to nn mt dng phc hp. Nh thy hnh bn, n c bin cao hn so vi xung quanh, v cc sng c hnh dng nh dy ni (nh cc kha to hnh ch V). Loi nhp ny hon ton khng cn xng 2 bn v thng b nhm vi hot ng in kch pht. Tuy nhin n l loi hot ng in lnh tnh.g)Nhp 14 v 6 (Fourteen and Six Rhythm): Nhp 14 v 6 rt hay thy tr em v thanh nin mi ln. Nh thy trn hnh, cc sng 6 Hz v 14 Hz i khi un ln theo cng 1 hng (ln hoc xung), v i khi th li i theo hng ngc nhau. Nhp kiu ny thy c in hnh trng thi ng hoc bun ng (ng g gt), v thng thy c trn bn ghi n cc (monopolar recordings). 4.3. Cc dng sng phc hp(complex wave pattern)-( dng bnh l):Cc dng sng c tnh c hiu do hnh dng ca chng bao gm: a)Gai v sng (spike and wave): Dng gai v sng thy c mi la tui, nhng thng nht l tr em. N bao gm 1 gai (c th l ngun pht nm v no) v mt sng chm (thng l delta) c bin cao, sng chm ny c coi l c ngun pht cc cu trc ca i th, phc b ny lp i lp li. Chng c th xut hin ng b (ng th synchronously) v cn i hai bn trong cc bnh ng kinh ton th ha (generalized epilepsies) hoc khu tr trong bnh ng kinh cc b. Trong nhng dng gai v sng ton th ha, cn vng thc s (true absense) hay l cn nh (petit mal) c trng bng gai-sng 3 Hz, trong khi gai chm sng (slow spike-wave) thng thy hn khi no b tn thng v trong hi chng Lennox-Gastaut. Nhng gai v sng nhanh hn 3 Hz s c trnh by trong phn di y, phn v a gai v sng (polyspike-wave).b)a gai v sng (polyspike and wave):L mt dng ca gai sng, trong mi mt sng chm i km vi 2 hoc nhiu gai. Dng thng gp l dng gai v sng c tn s nhanh hn 3 Hz thng l 3.5 ti 4.5 Hz. Dng ny thng c i km vi git c (myoclonus) hoc cc cn kch pht git c (myoclonic seizures). ng nhm ln n vi gai sng 6 Hz, vn c coi l gai sng khng thc (phantom spike and wave) l mt bin th ca bnh thng.c)Cc phng in dng ng kinh lch bn theo chu k (PLEDS - Periodic Lateralized Epileptiform Discharges): L mt dng phng in i km vi tn thng hay chn thng no cp tnh. Ngi ta thy dng sng ny r nht khi tn thng no cp tnh c kt hp thm vi ri lon chuyn ha. N khi u bng nhng sng nhn xut hin mt cch u n, trn mt nn tng i bng phng, 1 vng hay 1 bn ca no. Sau nhp ca n chm dn li v xut hin cc sng chm theo chu k, v hot ng in c s nm gia cc phng in dng ng kinh ny cng kh dn ln. Cui cng cc sng dng ng kinh kiu ny cng bin mt hon ton. Kiu PLEDS thng thy khi c triu chng nh khu nng, hoc l trn mt bnh nng ang c xu hng kh dn ln.

d)Cc sng 3 pha (triphasic waves): Sng 3 pha l 3 sng to vin cho mu trng trn hnh minh ha. Chng thng xut hin khi c cc hot ng in gi cn kch pht (pseudoparoxysmal activity). Cc sng ny thy c trong bnh no do gan (hepatic encephalopathy), nhng cng c th thy trong cc dng bnh no do chuyn ha khc.e)Bng n v c ch (burst supression): Bng n v c ch l mt dng bng n cc sng chm v hn hp (mixed waves) thng vi bin cao, v xen k lun phin bng ng ng in. Thng l c c hai bn, nhng khng phi lc no cng cn i 2 bn. Loi sng ny thng thy sau mt tn thng no nng, nh sau t qu thiu mu no (postischemia), hay sau trng thi thiu oxy (postanoxia). Cng c th thy tm thi (thong qua) trong gy m su, trng thi trc khi EEG tr nn ng in hon ton. 4.4.EEG bnh thng khi thcGm: Nhp alpha Hot ng beta Nhp mu a)Nhp alpha: l c im ni bt nht ca in no trng thnh bnh thng. Nhp alpha bnh thng c cc c im sau:Tn s: 8-12 Hz. V tr: u th vng sau. Hnh dng: c nhp, u, hnh sin. Bin : thng 20-100 mV. Phn ng: tt nht khi nhm mt v gim khi m mt. b) Hot ng beta:Tn s: > 13 Hz, thng 18-25 Hz. V tr: thng trn-trung tm. Hnh dng: c nhp, tng gim v cn xng. Bin : thng 5-20 mV. Phn ng: thng tng trong giai on gic ng I v II. c)Nhp mu (rhythm en arceau or wicket rhythm) :Tn s: 7-11 Hz. V tr: thng trung tm-nh. Hnh dng: dng cung hay m, thng khng cn xng v khng ng b hai bn, c th ch mt bn. Bin : thng thp n va. Phn ng: gim vi vn ng chi i bn, c ngh vn ng hay xc gic. Khng phn ng khi m hay nhm mt. 4.5.Tn hiu EEG khi ngGic ng c chia lm hai loi ln: Gic ng khng c ng mt nhanh (NREM) Gic ng c ng mt nhanh (REM) Da vo nhng thay i trn EEG gic ng NREM c chia thnh 4 giai on: I, II, III v IV. Gic ng NREM chim khong 75-90% thi gian ng (3-5% giai on I, 50-60% G II, v 10-20% G III v IV). Gic ng REM chim khong 10-25% thi gian ng. a) Gic ng NREM-giai on IVi c im l bun ng (drowsiness). C cc tnh cht sau: Vn nhn cun trn chm - Slow rolling eye movements (SREMs) Gim nhp alpha Hot ng theta trung tm hay trn trung tm Tng hot ng beta Sng nhn dng vng chm tm thi ca gic ng - Positive occipital sharp transients of sleep (POSTS) Sng nhn tm thi nh Tng ng b do gic ng . b)Gic ng NREM-giai on II:L giai on gic ng u th trong gic ng ban m bnh thng. EEG: thoi gic ng v phc hp K v cc c im khc nh giai on I (ngoi tr SERM

c)Gic ng NREM-giai on III v IV:Cn gi l giai on gic ng sng chm hay gic ng delta. Giai on ny thng khng c vn ng, tuy nhin c th ghi nhn mt s vn ng vo cui giai on.

d)Gic ng REMGic ng REM c xc nh bng: Vn ng mt nhanh Mt trng lc c Mt ng b trn EEG: hot ng in th nhanh hn v thp hn so vi NREM. Cc sng hnh rng ca: loi hot ng theta t bit vng trung tm, hnh nh rng ca v thng st vng vn ng mt nhanh. 5.Cc yu t nh hng ti tn hiu in no( nhiu)Nhiu l nhng sng hoc nhng nhm cc sng do li k thut hoc do cc li khc gy ra, v khng phi do hot ng in ca no gy ra. Nhiu l cc ri lon do khim khuyt k thut gy ra, thng l nhng li c tnh tm thi. Bao gm do di ng cc in cc lm cho mt tip xc, cc hot ng in ca c che khut in no , do c ng ca u, chy xc da u, ra m hi, v.v Nu ta dng phng i ln, th tt c cc bin lon k trn u c phng i ln, bao gm cc nhiu ca mch v in tm , ca in cc v cc c ng, nhiu 60 Hz v nhiu do m hi, l loi nhiu biu hin c dung dch mui nm gia cc in cc lm cho n b on mch. 5.1.Nhiu do in tm v do mch (EKG and pulse artifacts): C 2 loi nhiu ny u c th nhn bit c nh vo tnh cht c chu k ca chng. Nhiu in tm cho thy r phc b QRS theo chu k, v in tm th c tn hiu in ln hn nhiu so vi in no . Nhiu do mch l do mch p pha di ca in cc lm cho n chuyn ng theo chu k. C 2 loi nhiu nu u d nhn din, nhng cng c th gy kh khn cho c in no. 5.2.Nhiu do chuyn ng ca in cc v cc chuyn ng khc: Nhiu do chuyn ng ca bnh nhn th c ng biu th t ngt, v trong hu ht trng hp n dc ngc t ngt. So vi cc sng EEG chun th cc nhiu c bin cao v ko di v thi gian. Mt nhiu kiu POP l do chuyn dch in cc rt ngn (nhanh), ngi mi vo ngh d nhm ln n vi mt gai (spike), tuy nhin gai kiu ny ch thy 2 knh cnh nhau v khng thy knh th ba nh nhng gai ng kinh. 5.3.Nhiu do dng c truyn tnh mch v nhiu 60 Hz:Nhng nhiu ny thng c thy trong khi ghi in no trong phng sn sc c bit (ICU) v c 2 u l nhng giao thoa v in. Trn hnh v, nhiu do dng c truyn l nhiu c mu ; n c tnh cht chu k, c bin thp v d dng nhn bit. Nhiu su mi Hz thy c nhng ni in cc tip xc km, ni t khng tt, v c mt thit b in chuyn dng t gn . N gy nn nhng gai (spikes) c tn s 60 chu k giy to thnh vt mc in trn giy chy vi tc thng thng. 6.X l tn hiu in noEEG c c tnh phc tp v ngha ca n trong nghin cu no v thc hnh lm sng mang li 1 s gii thiu sm v nhng phng php phn tch tn hiu EEG. Trong phn tip theo , chng ta s miu t ngn gn nhng phng php c bn v x l tn hiu EEG. Chng ta s bt u vi nhng phng php quang ph. Ta xt v thc nghim u tin ca ng dng phn tch Fuorier v in no. 6.1. Bin i FuorierTrong th k 19, nh ton hc ngi Php J.Fuorier, m t bt k 1 hm tun hon no cng c th din gii bng 1 tng v hn ca nhng hm m phc tp tun hon. Nhiu nm sau, ng khm ph ra 1 c tnh khc thng ca hm, tng ca ng c khi qut ha nhng hm khng tun hon u tin v sau l nhng tn hiu thi gian ri rc tun hon hoc khng tun hon. Sau n c khi qut ha thnh 1 cng c thch hp tnh ton my tnh. Nm 1965, 1 thut ton mi gi l truyn Fuorier nhanh (FFT) c pht trin v FT ngy cng tr nn ph bin. 6.2. nh v EEG:Vi kh nng ghi ng thi 1 s lng ln knh s ha ca EEG, 1 k thut mi ra i: nh v EEG, ti thi im cui ca 80. Trong k thut ny, 1 s ln cc in cc c t trn u theo 1 dy hnh hc cc im even space. Mt phn mm c bit bn trong my tnh, th hot ng trn mt mn hnh mu hoc my in, bi m ha s lng ca hot ng trong 1 vi mc ca mu sc (v d, mu en v xanh c th m t bin EEG thp, trong khi vng v c th m t bin ln hn). Nhng im trong khng gian nm gia cc in cc c tnh ton bng nhng k thut ton hc ca php ni suy (tnh ton gi tr ngay tc khc trn c s gi tr lin k), v nh th t c s phn cp u n v mu sc.

S li gn hn na chnh xc v tm nhn in hnh ca v tri ca s thay i nhp , bin , trong mi quan h vi dng in I trn b mt hp s. Bc s thn kinh lm vic vi h thng nh v EEG sm phn bit 1 vi dng khc nhau ca chn on. Xc nh v tr chnh xc ca s bin i EEG cng lm cho n d dng hn. Trong phn thm vo, s dng ch cine lm tng kh nng nghin cu ca chc nng no trong hot ng( Maurer 1991).nh v EEG khng c thc hin trong cc trng hp ghi li hot ng ca no. S ch dn chnh ca n xc nh s c mt ca khi u v bnh ca no (trong chng ng kinh, t qu). N cng thch hp khi nhiu trong trng thi tnh to v thn trng c thit lp nh chng ng kch pht, hn m nh v EEG ngy cng c s dng cho my kim tra ngi s dng ma ty, v bnh truyn nhim ca no v d nh vim mng no. Trong tm thn, nh v EEG nhn ra s ri lon ca ngun gc sinh hc, nh bnh tm thn phn lit, chng mt tr, tnh hiu ng thi qu v trm cm, chng teo no v suy nhc c th ca tr em ( Peter 1995). N ph thuc vo thi im no php ni suy c thc hin. Nu ta ly gi tr bin trc tip trong cc khong thi gian, ta s c 1 bn bin . S kt hp quang ph Mt kt qu ring bit ca phn tch quang ph c o lng gia 2 in cc. N c nh c im ging nhau ca ni dung quang ph ca 2 in cc . N l hu nh khng th nh gi s kt hp bng kim sot EEG th gic. Mt s cn bnh c th bt u vi nhng s d thng ca 2 v no, Leuchter vit v nhng chng bnh Alzheimer v Thatcher tm ra nhng chng bnh ca kt hp nh b phn bit tt nht ca thng tn u phn mm. Ta s ch ra kh nng ca nhng k thut trn cc v d ca b thu nhiu chp chn. Ta s thc hnh s tnh ton kt hp quang ph trong 4 di tn s tng ng vi cc dng sng alpha, beta, delta v nhng sng game.7.Bin i FFT: BIN I FOURIER RI RC (DFT)7.1. nh ngha v tnh cht:2.1.1: inh nghia:Bin i Fourier ri rc (DTFT) ca x(n) m t nh sau:

Bin i Fourier ri rc (DFT Discrete Fourier Transform) N im ca x(n) m t nh sau:

Bin i Fourier ngc (IDFT Inverse DFT):

7.2. Tnh cht ca DFT N im:-Tun hon: Nu x(n) v X(k) l mt cp bin i DFT N im th:

x(n + N) = x(n) n

X(k + N) = X(k) k-Tuyn tnh: Nu:x1(n) DFT-N X1(k)x2(n) DFT-N X2(k)thi: a1(n) x1(n) + a2(n) x2(n) DFT-N a1(k) X1(k) a2(k) X2(k)-i xng:

Xet: va DFT N im thi:

Va:

Nu x(n) chn: x(n) = x(-n) thiX(k) = XR(k) = XR(-k)Nu x(n) le: x(n) = -x(-n) thiX(k) = jXT(k) = -jXT(-k)Nu x(n) la tin hiu thc, xT(n) = 0:XR(k) = XR(-k)XT(k) = -XT(-k)Hay: X(k) = X*(-k)Nu x(n) la tin hiu ao, xR(n) = 0:XR(k) = -XR(-k)XT(k) = XT(-k)Hay: X(k) = -X*(-k)- o trn min thi gian:Nu:x(n) DFT-N X(k) thi: x1(N - n) DFT-N X(N k)-Dch chuyn thi gian v dch chuyn tn s:Nu: x(n) DFT-N X(k) thi: x(n-1) DFT-N X(k)e-j2kl/Nva: x(n)ej2kl/N DFT-N X(k-1)-Lin hip phc:Nu:x(n) DFT-N X(k) thi: x*(n) DFT-N X*(N-k) -Tng quan:Nu:x(n) DFT-N X(k) v y(n) DFT-N Y(k) thi: rxy DFT-N X(k)Y*(k)-Nhn:x1(n) DFT-N X1(k) x2(n) DFT-N X2(k) thi: x1(n) x2(n) DFT-N (1/N) X1(k) X2(k)8. Ve ph:Vi mt tin hiu EEG thu c vi tn s ly mu Fs=128Hz, ph FFT c ve bi knh th nht (hang 1 trong ma trn):

8.1. Ph DFT:

8.2: S dung DFT tinh toan cng quang ph:

8.3: Peridogram: Periodogram l thc o quang ph nng lng v cng tng t nh vi bnh phng ca cng quang ph -trn thc t, s khc bit duy nht l cc yu t quy m . Nu chng ta tnh ton cng s dng ph DFT, hnh vung, quy m v sau chuyn sang decibel (dB), chng ta s c periodogram.Mt ham ca s co th khng cn thit cho tin hiu, nhng khi mt ca s c s dung binh thng co N khng ln lm, nhng co CN trong o C c tinh bi:

Va w[n] c s dung nh la mt ca s. iu ny l trnh bt k s thin v trong d ton do vic s dng cc ca s.Quang ph thu c c gi l bin i periodogram.Hinh di y la mt Periodogram cua tin hiu EEG:

8.4 Welch's Method :Mt c lng ci tin ca PSD l mt trong nhng xut ca Welch. Phng php ny bao gm phn chia cc d liu chui thi gian vo (c th chng cho ) phn on, tnh ton mt periodogram sa i ca tng phn khc , v sau a ra kt qua d toan trung bnh PSD.

Bc u tin trong phng php ny l phn chia cc d liu vo phn khc vi K im chng cheo mi cai co cha M im ly mu. Khng chng cho co chiu di l D, tc l cc phn on trng vi mu . Do v t l phn tram chng cho l .Phng php Welch mang li mt c lng kin ca PSD . Gi tr d kin c th c tm thy l:

Ls l chiu di ca cc phn on d liu, U l bnh thng cng c mt lin tc trong nh ngha ca bin i periodogram. c lng ca Welch l tim cn. i vi mt bn ghi d liu chiu di c nh, s tim cn ca d ton Welch l ln hn so vi periodogram v Ls < L.

Hinh di nay la tin hiu EEG c ly vi 301 mu:

Chng ta c th c c c tnh ph Welch cho 3 phn khc vi 50% chng ln nhau vi pwelch (xn,toa( 150 ),75.512 ,fs) ;

Hinh sau a c c tinh ph cho 3 phn khuc vi 50% chng ln nhau:

-Trong periodogram, ting n v s r r trong tin hiu thu c khng th phn bit t cc nh.

Ngc li, mc d cc tin hiu c ve bng phng php Welch c nh rng ln hn, bn vn c th phn bit hai ng hinh sin , trong ni bt so vi cc mc nhiu.

8.5H s t hi nh cc tnh nng phn bit nhim v tinh thn:

H s AR cac tinh nng, ta se xem xt cc tn hiu EEG thu c trong hai hot ng tinh thn khc nhau. Ta se xem xet hai hot ng ton hc v tng tng mt i tng c lun chuyn. Vi cac tin hiu EEG thu c ta kho co th phn bit c cac tin hiu o ang noi v gi, y la mt kho khn. Nhng bng cch s dng h s AR 6 phn t ta co th phn bit c cc hot ng ton hc v lun chuyn i tng. y mc d gi tr chnh xc nhng khng c a ra, bi m hnh m hnh cho cc hot ng tinh thn nh nhau, cc gi tr l gn trong mt hot ng tinh thn v khc nhau qua cc hot ng (c bit l nhng h s AR u tin).Hinh di y minh ha vic s dng cc h s AR.