Victor Babes UNIVERSITY OF MEDICINE AND PHARMACY TIMISOARA

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Victor Babes UNIVERSITY OF MEDICINE AND
PHARMACY TIMISOARA

• DEPARTMENT OF
• MEDICAL INFORMATICS AND BIOPHYSICS
• Medical Informatics Division
• www.medinfo.umft.ro/dim
• 2004 / 2005

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BIOSIGNAL PROCESSING. NON-PERIODICAL SIGNALS.

• COURSE 8

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1. EEG SIGNAL
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• 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

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

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1.2. ANALYSIS METHODS CLASSIFICATION

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

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1.3. TEMPORAL ANALYSIS

• a) AMPLITUDE ANALYSIS - histograms
• low / normal / high amplitude (voltage)
• b) INTERVAL ANALYSIS - level crossing
• zero crossing
• c) AMPLITUDE / INTERVAL - areas
• d) SEQUENTIAL ANALYSIS - peak-to-peak
• e) CORRELATION FUNCTION - origin
• inter-correlation
• self-correlation (auto-correlation)

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1.4. FREQUENTIAL ANALYSIS

• SIGNAL REPRESENTATION
• TEMPORAL
• Ampl f (time)
• FREQUENTIAL (spectrum)
• Ampl f (freq)

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Examples 1 Hertz sine signal and its spectrum
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A 2 Hz signal
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Mixed signals
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• 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)

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• 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

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Exemple - problem

• We record an EMG signal using a 10 bit ADC,
  with a sampling frequency of 500 Hz, recording
  epochs of 2 seconds. The input signal has
  values between 0 and 100 mV. Calculate
• Sampling period (in ms)
• Maximal frequency in the spectrum
• Spectral resolution
• Number of amplitude steps
• Reading precision (quantum value, how many mV
  correspond to 1 bit)

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• g) TRANSITORY PHENOMENA DETECTION
• SPIKES CONTRIBUTION IN SPECTRA
• MOBILE WINDOW METHOD (BERG)
• h) GRAPHICAL REPRESENTATIONS
• CURVES, HISTOGRAMS
• BICKFORD REPRESENTATION (time course)
• I) OTHER FREQUENTIAL ANALYSES
• WALSH, HAAR, ZERO CROSSING
• KALMAN RECURSIVE FILTERING
• CONVOLUTION FUNCTION

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Bickford Reprezentation
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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)

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• 1.6. PATTERN RECOGNITION
• 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

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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

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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

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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

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

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

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

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2.8. EXTRAVERBAL COMMUNICATION

• GAIT ANALYSIS
• WALKING PATTERNS
• WRITING / DRAWING
• GESTURE
• POSITION MAPPING

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