bg physiological signal processing 01 introduction to electrophysiology2019mk 7667

Nguyễn Công Phương PHYSIOLOGICAL SIGNAL PROCESSING Introduction to Electrophysiology Contents I Introduction II Introduction to Electrophysiology III Signals and Systems IV Fourier Analysis V Signal Sampling and Reconstruction VI The z-Transform VII.Discrete Filters VIII.Random Signals IX Time-Frequency Representation of Physiological Signals X Physiological Signal Processing s i tes.google.com/site/ncpdhbkhn Introduction to Electrophysiology Concept of Electrophysiology Membranes Bioelectrical Currents Membrane Polarization Action Potentials Propagation Extracellular Signals Electrocardiography (ECG) Electromyography (EMG) 10 Electroencephalography (EEG) s i tes.google.com/site/ncpdhbkhn Concept of Electrophysiology • Electrophysiology: the study of the role of electricity in the physiology of organism functions (R Corsini, The Dictionary of Psychology, Routledge, 2016) • The classical concept of electrophysiology assumes that a nerve impulse is traveling wave of depolarization, moving at a constant velocity along a nerve pathway, with an accompanying pattern of circulating currents around and outside the pathway • In hospitals: electrophysiology refers to the electrical function of your heart (https://www.medstarunionmemorial.org/ourservices/heart-care/diagnosis/electrophysiology/) s i tes.google.com/site/ncpdhbkhn Introduction to Electrophysiology Concept of Electrophysiology Membranes Bioelectrical Currents Membrane Polarization Action Potentials Propagation Extracellular Signals Electrocardiography (ECG) Electromyography (EMG) 10 Electroencephalography (EEG) s i tes.google.com/site/ncpdhbkhn Membranes (1) • Bioelectricity has its origin in the voltage differences present between the inside and outside of cells • Membranes are the site of the electrically active elements – pumps, channels, and connexons joining cells that create the voltages and currents that cause electrical events to occur • The membrane has a high capacitance, about 1μF/cm2 https ://en.wikipedia.org/wiki/Membrane_potential s i tes.google.com/site/ncpdhbkhn Membranes (2) Cell membrane possesses a number of active characteristics of marked importance to its bioelectric behavior: – Some integral proteins function as pumps • These pumps use energy to transport ions across membrane, working against a concentration gradient, a voltage gradient, or both • The most important pump moves sodium ions out of the intracellular volume and potassium ions in s i tes.google.com/site/ncpdhbkhn Membranes (3) Cell membrane possesses a number of active characteristics of marked importance to its bioelectric behavior: – Other integral proteins function as channels, that is, openings through the membrane that open and close over time • These channels can function selectively so that, for a particular kind of channel, only sodium ions may pass through • Another kind of channel may allow only potassium ions or calcium ions s i tes.google.com/site/ncpdhbkhn Membranes (4) Cell membrane possesses a number of active characteristics of marked importance to its bioelectric behavior: – The activity of the membrane’s integral proteins is modulated by signals specific to its particular function • For example, some channels open or close in response to photons or to odorants; thus they function as sensors for light or smell • Pumps respond to the concentrations of the ions they move • Rapid electrical impulse transmission in nerve and muscle is made possible by changes that respond to the transmembrane potential itself, forming a feedback mechanism s i tes.google.com/site/ncpdhbkhn Membranes (5) https ://en.wikipedia.org/wiki/Resting_potentia l s i tes.google.com/site/ncpdhbkhn 10 Extracellular Signals (2) [Bronzino, 2006] s i tes.google.com/site/ncpdhbkhn 31 Introduction to Electrophysiology Concept of Electrophysiology Membranes Bioelectrical Currents Membrane Polarization Action Potentials Propagation Extracellular Signals Electrocardiography (ECG) Electromyography (EMG) 10 Electroencephalography (EEG) s i tes.google.com/site/ncpdhbkhn 32 ECG (1) • ECG: the recording on the body surface of the electrical activity generated by the heart • Waller in 1889 & Einthoven in 1903 • The most commonly known, recognized, and used biomedical signal s i tes.google.com/site/ncpdhbkhn 33 ECG (2) aVL aVR aVF I Vw vi II III Ι = VRA − VLA ΙΙ = VRA − VLL ΙΙΙ = VLA − VLL 2VLA − VRA − VLL 2V − V − V aVR = RA LA LL 2V − V − V aVF = LL LA RA aVL = s i tes.google.com/site/ncpdhbkhn VRA + VLA + VLL Vw = Vi = vi − Vw i = 1, 2,3, 4,5,6 34 ECG (3) Vw vi VRA + VLA + VLL Vw = Vi = vi − Vw i = 1, 2,3, 4,5,6 [Rangayyan, 2015] s i tes.google.com/site/ncpdhbkhn 35 ECG (4) [Bronzino, 2006] s i tes.google.com/site/ncpdhbkhn 36 ECG (5) https ://www.thoughtco.com/heartnodes-anatomy-373242 [Rangayyan, 2015] s i tes.google.com/site/ncpdhbkhn 37 ECG (6) • The typical recording speed used is 25 mm/s, resulting in a graphical scale of 0.04 s/mm or 40 ms/mm • The ECG signal peak value is normally about mV • The amplifier gain used is 1000 • Clinical ECG is usually filtered to a bandwidth of about 0.05 – 100 Hz, with a recommended sampling rate of 500 Hz for diagnostic ECG • ECG for heart-rate monitoring could use a reduced bandwidth 0.5 – 50 Hz & a lower sampling rate 100 Hz • High-resolution ECG requires a greater bandwidth of 0.05 – 500 Hz s i tes.google.com/site/ncpdhbkhn 38 Introduction to Electrophysiology Concept of Electrophysiology Membranes Bioelectrical Currents Membrane Polarization Action Potentials Propagation Extracellular Signals Electrocardiography (ECG) Electromyography (EMG) 10 Electroencephalography (EEG) s i tes.google.com/site/ncpdhbkhn 39 EMG (1) https://www.pinterest.com/pin/7810 999324933682/?lp=true • Movement and position of limbs are controlled by electrical signals traveling back and forth between the muscles and the peripheral and central nervous system • Electromyography (EMG) is the registration and interpretation of these muscle action potentials • EMG are recorded primarily for exploratory or diagnostic purposes • Functional electrical stimulation (FES) s i tes.google.com/site/ncpdhbkhn 40 EMG (2) Monophasic waveforms Biphasic waveforms Triphasic waveforms [Rangayyan, 2015] s i tes.google.com/site/ncpdhbkhn 41 EMG (3) http://www.ricercadiagnostica.it/en/ phys ical-therapy/electromyography/ https ://onlinelibrary.wiley.com/doi/abs/10.1002/mus.24955 s i tes.google.com/site/ncpdhbkhn 42 Introduction to Electrophysiology Concept of Electrophysiology Membranes Bioelectrical Currents Membrane Polarization Action Potentials Propagation Extracellular Signals Electrocardiography (ECG) Electromyography (EMG) 10 Electroencephalography (EEG) s i tes.google.com/site/ncpdhbkhn 43 EEG (1) https://i.imgur.com/ZrmxJRu.jpg s i tes.google.com/site/ncpdhbkhn 44 EEG (2) https://www.sciencedirect.com/topics/medicine-and-dentistry/electroencephalogram s i tes.google.com/site/ncpdhbkhn 45