BioSignal Processing

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.

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

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

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)

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

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

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

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

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

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

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

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