Biopotentials

Biopotentials and Electrophysiology Measurement

Agenda ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What are biopotentials ,[object Object],[object Object],[object Object]

Mechanism behind biopotentials 1/2 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Mechanism behind biopotentials 2/2 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Electrocardiography (ECG) ,[object Object],[object Object],[object Object],[object Object],1. Atrial depolarization 2. Ventricular depolarization 3. Ventricular repolarization

ECG basics ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

12-Lead ECG measurement ,[object Object],[object Object],[object Object],[object Object],[object Object],Einthoven leads: I, II & III Goldberger augmented leads: V R , V L & V F Precordial leads: V 1 -V 6

Why is 12-lead system obsolete? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Electroencephalography (EEG) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

EEG measurement setup ,[object Object],[object Object],[object Object],[object Object],[object Object]

Electromyography (EMG) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Electrooculography (EOG) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Vectorcardiogram (VCG or EVCG) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The biopotential amplifier ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The Instrumentation Amplifier ,[object Object],[object Object],[object Object],[object Object],CMRR fine tuning

Application-specific requirements ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Electrical Interference Reduction ,[object Object],[object Object],[object Object],[object Object],[object Object]

Filtering ,[object Object],[object Object],Small inductors or ferrite beads in the lead wires block HF frequency EM interference RF filtering with small capacitors High-pass filter to reject DC drifting Low-pass filtering at several stages is recommended to attenuate residual RF interference

50 or 60 Hz notch filter ,[object Object],[object Object],[object Object],[object Object],Twin T notch filter Determines notch frequency Notch tuning

Artifact reduction ,[object Object],[object Object],[object Object],[object Object]

Electrical isolation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Defibrillation Protection ,[object Object],[object Object],[object Object],1. Resistors in the input leads limit the current 3. Protection against much higher voltages is achieved with low-pressure gas discharge tubes (e.g. neon lamps) (note: even isolation components such as transformers and optical isolators need these spark gaps) Discharge @ ~100V 2. Diodes or Zener diodes protect against high voltages Discharge @ 0.7-15V

Electrodes – Basics ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Electrodes - Basics ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Baseline drift due to the changes in junction potential or motion artifacts  Choice of electrodes Muscle signal interference  Placement Electromagnetic interference  Shielding

Ag-AgCl, Silver-Silver Chloride Electrodes ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Gold Electrodes ,[object Object],[object Object],[object Object],[object Object],[object Object],Conductive polymer electrodes ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Metal or carbon electrodes ,[object Object],[object Object],[object Object],[object Object],Needle electrodes ,[object Object],[object Object],[object Object],[object Object]

That’s it, Now for Q&A SQUID = Superconducting Quantum Interference Device

Biopotentials

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Biopotentials