BioSignal Processing

1. BioSignal Processing

2. Introduction • Biological signals or biosignals • Are space, time, or space–time records of a biological event such as a beating heart or a contracting muscle. The electrical, chemical, and Mechanical activity that occurs during these biological event often produces signals that can be measured and analyzed. • Contain useful information that can be used to understand the underlying physiological mechanisms of a specific biological event or system, and which may be useful for medical diagnosis.

3. Introduction Digital processing methods • Data acquisition • Using stethoscope to listen to patient’s heart • Signal analysis • Retrieve useful information • Amplification • Filtering • Digitization • Processing • Storage

4. Physiological Origins of Biosignals • Bioelectric Signals • Generated by nerve and muscle cells as a result of electrochemical changes within and between cells • Can be measured with intracellular or extracellular electrodes • ECG, EGG, EEG, and EMG are results of the Bioelectric signals taken from the human body

5. Physiological Origins of Biosignals • Biomagnetic Signals • Different organs(heart, lungs & brain) generate weak magnetic fields • Measured from specific physiological activity that is linked to an accompanying electric field from a specific tissue or organ • Uses very precise magnetic sensors or SQUID magnetometers (Superconducting Quantum Interference Device)

6. Physiological Origins of Biosignals • Bio magnetic Signals (cont.) • Magnetoencephalography (MEG) - monitor magnetic activity from the brain • Magnetoneurography (MNG) – monitor peripheral nerves • Magnetogastrography (MGG) – monitor gastrointestinal tract • Magnetocardiography (MCG) – monitor the heart

7. Physiological Origins of Biosignals • Biochemical Signals • Contain information about changes in concentration of various chemical agents in the body • Oxygen concentration • Determine levels of glucose, lactate and metabolites • Provides information about the function of various physiological systems

8. Physiological Origins of Biosignals • Biomechanical Signals • Produced by the mechanical functions of biological signals such as: • motion, displacement, tension, force, pressure, and flow • Blood pressure measurement

9. Physiological Origins of Biosignals • Bioacoustic Signals • Are special subset of biomechanical signals that involve vibrations (motion) • Respiratory system, joints, and muscles generate distinct bioacoustic signals • Often measured at the skin using acoustic transducers such as microphones and accelerometers

10. Physiological Origins of Biosignals • Biooptical Signals • Generated by the optical, or light-induced, attributes of biological systems • May occur naturally or signals can be introduced to measure a biological parameter using an external light medium

11. Characteristics of Biosignals • Biosignals can be classified according to various characteristics: • Waveform Shape • Statistical Structure • Temporal Properties • 2 broad classes of signals: • Continuous • Discrete

12. Characteristics of Biosignals • Continuous Signals • Defined over a continuum of time or space and are described by continuous variable functions • Produced by biological phenomena: • Like voltage measurements from the heart • Arterial blood pressure measurements • Measurements of electrical activity from the brain

13. Characteristics of Biosignals • Discrete Signals • Defined only at a subset of regularly spaced points in time and/or space • Commonly used in today’s clinical setting • Continuous signals from human body are converted to discrete signals that can be analyzed and interpreted by a computer