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Examples of Biomedical Signals

Examples of Biomedical Signals. 2nd practice Medical Informatics Biomedical Signal Processing TAMUS, Zoltán Ádám zoltanadam_tamus@yahoo.com. Examples of Biomedical Signals. Action potential Electroneurogram (ENG) Electromyogram (EMG) Electrocardiogram (ECG) Electroencephalogram (EEG)

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Examples of Biomedical Signals

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  1. Examples of Biomedical Signals 2nd practice Medical InformaticsBiomedical Signal Processing TAMUS, Zoltán Ádám zoltanadam_tamus@yahoo.com

  2. Examples of Biomedical Signals • Action potential • Electroneurogram (ENG) • Electromyogram (EMG) • Electrocardiogram (ECG) • Electroencephalogram (EEG) • Electrogastrogram (EGG) • Phonocardiogram (PCG) • Carotid Pulse (CP) • Vibromyogram (VMG) • Vibroarthogram (VAG)

  3. The Action Potential Basic component of bioelectrical signals Caused by the flow of Na+, K+ and Cl- ions across the cell membrane

  4. The Action Potential • Resting potential: • In their resting state, the membrane readily permit the entry of K+ and Cl- ions, but effectively block the entry of Na+ ions. • The permeability of membrane for K+ is 50-100 times that for Na+ ions. • A cell in resting state is said to be polarized. • The resting potential is in order of -60 to -100 mV

  5. The Action Potential • Depolarization: • When a cell is excited the membrane changes its characteristics and begins to allow Na+ ions to enter the cell. • This movement of Na+ ions constitutes an ionic current, which further reduces the membrane barrier to Na+ ions. • This leads to an avalache effect: Na+ ions rush into the cell. • The inside of the cell becomes positive. • The peak value of action potential is about 20 mV

  6. The Action Potential • Repolarization: • Membrane depolarization also increases the permeability of membrane for K+ ions via a voltage-dependent K+ channels. • The permeability of membrane for Na+ ions decrease near the peak of depolarization. • The efflux of K+ ions from the cell makes the inside more negative thereby effecting repolarization back to the resting potential. • Duration in nerve and muscle cells ~1 ms, in heart muscle cells 150-300 ms

  7. The Action Potential • All-or-none phenomenon • Absolute refractory period: 1 ms in nerve cells • Relative refractory period: several ms in nerve cells

  8. The Action Potential

  9. The Action Potential

  10. Electroneurogram (ENG) • The ENG is an electrical signal observed as a stimulus and the associated nerve action potential propagate over the length of nerve. • ENGs may be recorded using contcentric needle electrodes or Ag-AgCl electrodes at the surface of the body. • In order to minimize muscle contraction strong but short stimulus is applied (100 V amplitude, 100-300 μs). • ENGs have amplitudes of the order of 10 μV.

  11. Electroneurogram (ENG) Wirst BElbow - below the elbow AElbow – above the elbow

  12. Electroneurogram (ENG) • Typical values of propagation rate or nerve conduction velocity are: • 45-70 m/s in nerve fibers • 0.2-0.4 m/s in heart muscle • 0.03-0.05 m/s in time delay fibers between the atria and ventricles. • Neural diseases may cause a decrease in conduction velocity.

  13. Electromyogram (EMG) Motor units Single Motor Unit Action Potential (SMUAP)

  14. Electromyogram (EMG) Normal SMUAPs are usually biphasic or triphasic 3-15 ms in duration, 100-300 μV in amplitude, 6-30 Hz in frequency range

  15. Electroencephalogram (EEG) The 10-20 system of electrode placement for EEG recording.

  16. Electroencephalogram (EEG) • The commonly used terms for EEG frequency range: • Delta (0.5-4 Hz): deep sleep • Theta (4-8 Hz): beginning stages of sleep • Alpha (8-13 Hz): principal resting rhythm • Beta (>13 Hz): background activity in tense and anxious subjects

  17. Electroencephalogram (EEG) • a: delta, b: theta, c: alpha, d: beta, e: blocking of alpha rhythm by eye opening, f: marker 50 μV, 1 sec

  18. Electrogastrogram (EGG) The electrical activity of the stomach consists of rhytmic waves of depolarization and repolarization of its constituent smooth muscle cells. The activity originates in the mid-corpus of the stomach, with intervals of about 20 s in human. Recorded by abdomen electrodes e.g. three electrodes along the antral axis of stomach and the common reference electrode

  19. Carotid Pulse (CP) • The CP is a pressure signal recorded over the carotid artery. • Parts of CP: • P (percussion wave): ejection of blood from the left ventricle • T (tidal wave): reflected pulse from the upper body • D (dicrotic notch): closure of the aortic valve • DW (dicrotic wave): reflected pulse from the lower body

  20. Vibromyogram (VMG) Direct mechanical manifestation of contraction of a skeletal muscle. Accompanies the EMG Recorded by contact microphones or accelerometers placed on the muscle surface.

  21. Vibroarthogram (VAG) • The VAG is the vibration signal recorded from a joint during movement (articulation) of the joint. • Normal joint surfaces are smooth and produce little or no sound. • Joint affected by osteoarthiritis and other degnereative diseases may have suffered cartilage loss and produce grinding sounds. • The VAG is complex signal and difficult to analyze.

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