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“Victor Babes” UNIVERSITY OF MEDICINE AND PHARMACY TIMISOARA

“Victor Babes” UNIVERSITY OF MEDICINE AND PHARMACY TIMISOARA. DEPARTMENT OF MEDICAL INFORMATICS AND BIOPHYSICS Medical Informatics Division www.medinfo.umft.ro/dim 2004 / 2005. BIOSIGNAL PROCESSING. NON-PERIODICAL SIGNALS. COURSE 8. 1. EEG SIGNAL. 1.1. EEG SIGNAL ELEMENTS:

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“Victor Babes” UNIVERSITY OF MEDICINE AND PHARMACY TIMISOARA

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  1. “Victor Babes” UNIVERSITY OF MEDICINE AND PHARMACY TIMISOARA DEPARTMENT OF MEDICAL INFORMATICS AND BIOPHYSICS Medical Informatics Division www.medinfo.umft.ro/dim 2004 / 2005

  2. BIOSIGNAL PROCESSING. NON-PERIODICAL SIGNALS. COURSE 8

  3. 1. EEG SIGNAL

  4. 1.1. EEG SIGNAL ELEMENTS: • a) TYPICAL WAVES: • DELTA : 0.5 - 3 Hz • large; in pathological states, normal in babies only • THETA : 4 - 7 Hz • large amplitude, dominant in some sleep stages • ALPHA : 8 - 12 Hz • medium amplitude, normal in relaxed brain, originating in occipital area • BETA : 13 - 30 Hz (18 - 22) • small amplitude, associated with brain activity, typical for frontal areas

  5. b) TRANSITORY ELEMENTS • PEAK - WAVE COMPLEX (pathological) • ARTIFACTS: blinking, ECG, EMG etc • c) RECORDING TYPES • SPONTANEOUS SIGNAL • AWAKE • ASLEEP • EVOKED POTENTIALS

  6. 1.2. ANALYSIS METHODS CLASSIFICATION a) ELEMENTARY METHODS • TEMPORAL • FREQUENTIAL • PARAMETRICAL b) INTEGRATIVE METHODS • PATTERN RECOGNITION • SYNTACTIC ANALYSIS c) EVOKED POTENTALS

  7. 1.3. TEMPORAL ANALYSIS a) AMPLITUDE ANALYSIS - histograms • low / normal / high amplitude (voltage)

  8. Amplitude Histogram

  9. b) INTERVAL ANALYSIS - level crossing • zero crossing • c) AMPLITUDE / INTERVAL - areas • d) SEQUENTIAL ANALYSIS – peak-to-peak

  10. e) CORRELATION FUNCTION – shows the potential source • inter-correlation or self-correlation (auto-correlation)

  11. 1.4. FREQUENTIAL ANALYSIS • SIGNAL REPRESENTATION: • TEMPORAL Ampl = f (time) • FREQUENTIAL (spectrum) Ampl = f (freq)

  12. Examples: 1 Hertz sine signal and its spectrum

  13. A 2 Hz signal

  14. Mixed signals

  15. b) FILTER ANALYSIS • BAND - PASS FILTERS ( d, q, a, b ) • WAVES PROPORTIONS - mingographs • c) FOURIER ANALYSIS • Definition: SIGNAL DECOMPOSITION INTO FREQUENCIAL COMPONENTS • Domain: 0 - 30 Hz • Types of spectra: • AMPLITUDE • POWER (proportional to A2)

  16. c) SPECTRAL RESOLUTION • DEFINITION: distance between two neighbour points in the spectrum • RELATION WITH EPOCH LENGTH (recorded signal duration, in seconds) D f = 1 / D T (5) • d) TIME CONSTANT • e) TESTS FOR SIGNALS • STATIONARITY, NORMALITY AND TREND TESTS

  17. g) TRANSITORY PHENOMENA DETECTION • SPIKES CONTRIBUTION IN SPECTRA • MOBILE WINDOW METHOD (BERG)

  18. h) GRAPHICAL REPRESENTATIONS • CURVES, HISTOGRAMS • BICKFORD REPRESENTATION (time course) • i) OTHER FREQUENTIAL ANALYSES • WALSH, HAAR, ZERO CROSSING • KALMAN RECURSIVE FILTERING • CONVOLUTION FUNCTION

  19. Bickford Reprezentation

  20. 1.5. PARAMETRIC ANALYSIS • a) STOCHASTIC PARAMETERS • PEAKS NUMBER AND INTENSITY • STATISTICAL PARAMETERS (m,s) • b) HJORTH PARAMETERS • ACTIVITY - amplitude • MOBILITY - frequency ( 1st derivative) • COMPLEXITY - frequency variations (2nd derivative)

  21. 1.6. PATTERN RECOGNITION

  22. 1.7. SYNTACTIC ANALYSIS • SHORT EPOCHS (non-stationary) • EPOCHS LABELING • SIGNAL = LABELS SEQUENCE (sentence) • 1.8. EEG MAPPING • 16-108 ELECTRODS • INTERPOLATION METHODS • TYPES OF MAPS: • AMPLITUDE / POWER • FREQUENCY • HJORTH PARAMETERS, ETC

  23. 1.9. EVOKED POTENTIALS • a) TYPES OF STIMULATION: • IN STANDARD RECORDINGS • OPEN / CLOSED EYES • HYPERVENTILATION • STROBOSCOPIC LIGHT • IN EVOKED POTENTIAL RECORDINGS • VISUAL PATTERNS (chessboard like) • AUDITORY STIMULI • SOMATIC STIMULI

  24. 1.9. EVOKED POTENTIALS

  25. b) EVOKED POTENTALS DETECTION • VERY SMALL AMPLITUDES (2-5 mV compared with 50-100 mV ground) • AVERAGING METHOD • RANDOM SIGNAL MEAN = 0 • REPEATED STIMULATIONS • EPOCHS SUPERPOSITION • RANDOM STIMULATION

  26. Evoked potential extraction by “averaging”

  27. 1.10. BIOFEEDBACK • a) RHYTHM ADAPTATION • b) STATE ADAPTATION ??? • c) Extension of relaxation procedures: a - band pass filter background modulated mild sound intensity controlled by a waves amplitude self-control training therapeutical effects

  28. 2. OTHER BIOSIGNALS

  29. 2.1. NEUROMUSCULAR INVESTIGATIONS • EMG (electro-myography) • NCV (nervous conduction velocity) • 2.2. RESPIRATORY INVESTIGATIONS • SPIROGRAPHY • VENTIALTION TESTS

  30. 2.3. EXERCISE TESTS • MULTIPLE SIGNAL • 2.4. PLETISMOGRAPHY • MULTIPLE SIGNAL • COMPLEX INVESTIGATION • 2.5. CARDIOVASCULAR EXPLORATION • PHONOCARDIOGRAPHY • RHEOGRAPHY

  31. 2.6. SENSE ORGANS INVESTIGATIONS • RETINOGRAMS • AUDIOGRAMS • 2.7. ULTRASONOGRAPHY • a) ECHO SIGNALS • SYSTEMS : A, B, M • ECHOCARDIOGRAPHY • PHOETAL ULTRASONOGRAPHY • b) DOPPLER SIGNALS

  32. 2.8. EXTRAVERBAL COMMUNICATION • GAIT ANALYSIS • WALKING PATTERNS • WRITING / DRAWING • GESTURE • POSITION MAPPING

  33. - e n d -

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