INTRODUCTION TO BIOMEDICAL SIGNALS in BSP

INTRODUCTION TO BIOMEDICAL

1. SRI KRISHNA COLLEGE OF TECHNOLOGY An Autonomous Institution Academic year 2024 – 2025 Regulation 2021 21ECE16 – Bio Signal Processing VII Semester Prepared by Dr.S.Nithya Devi, AP / ECE Dr.P.Divya , AP / ECE

2. Module 1 INTRODUCTION TO BIOMEDICAL SIGNALS Action Potential and Its Generation, Origin and Waveform Characteristics of Basic Biomedical Signals like: Electrocardiogram (ECG), Electroencephalogram (EEG), Electromyogram (EMG), Phonocardiogram (PCG), Electroneurogram (ENG), Event-Related Potentials (ERPS), Electrogastrogram (EGG), Objectives of Biomedical Signal Analysis, Difficulties in Biomedical Signal Analysis, Computer-Aided Diagnosis

3. Course Outcome CO 1 : Understand the concepts of bio signal processing.

4. Introduction to Biosignal Processing

5. Definition Biomedical signals are those signals (phenomenon that conveys information) which are used primarily for extracting information on a biological system under investigation. The process of extracting information could be as simple as feeling the pulse of a person on the wrist or as complex as analyzing the structure of internal soft tissues by an ultrasound scanner.

6. Electrocardiogram (ECG)

7. E lectroencephalogram (EEG) The electroencephalogram (EEG) is a recording of the electrical activity of the brain from the scalp. The recorded waveforms reflect the cortical electrical activity. Signal intensity: EEG activity is quite small, measured in microvolts (mV). Signal frequency: the main frequencies of the human EEG waves are: Delta : has a frequency of 3 Hz or below. It tends to be the highest in amplitude and the slowest waves. Theta : has a frequency of 3.5 to 7.5 Hz and is classified as "slow" activity. Alpha : has a frequency between 7.5 and 13 Hz. Beta : beta activity is "fast" activity. It has a frequency of 14 and greater Hz.

8. Electromyography(EMG) Electromyography is a process in which the electrical signals of the   muscles  are captured via an electrode. Electrical signals from the muscles represent anatomical and physiological properties of the muscle, produced during muscle contraction in a normal muscle and even at rest in an abnormal muscle and are controlled by the nervous system. EMG tests can provide data about the impulses from the nerves responsible for contraction and the reactions of the muscle fibres to the said impulses.  Depending on the device used, the resulting raw data can be exported as a graph called an electromyograph , therefore in some cases giving the name electromyography to the original test. Electromyography can be used For Research purpose For Clinical diagnostic procedure

9. E lectroneurogram (ENG) An   electroneurogram  is a method used to visualize directly recorded electrical activity of  neurons  in the  central nervous system  (brain, spinal cord) or the  peripheral nervous system  (nerves, ganglions). The acronym ENG is often used. An electroneurogram is similar to an  electromyogram  (EMG), but the latter is used to visualize muscular activity.  An electroneurogram is usually obtained by placing an electrode in the neural tissue. The electrical activity generated by neurons is recorded by the electrode and transmitted to an acquisition system, which usually allows to visualize the activity of the neuron. Each vertical line in an electroneurogram represents one neuronal action potential. Depending on the precision of the electrode used to record neural activity, an electroneurogram can contain the activity of a single neuron to thousands of neurons. 

10. Event-related potentials (ERPs) Event-related potentials are very small voltages generated in the brain structures in response to specific events or stimuli. They are EEG changes that are time locked to sensory, motor or cognitive events that provide safe and noninvasive approach to study psychophysiological correlates of mental processes. Event-related potentials can be elicited by a wide variety of sensory, cognitive or motor events. They are thought to reflect the summed activity of postsynaptic potentials produced when a large number of similarly oriented cortical pyramidal neurons (in the order of thousands or millions) fire in synchrony while processing information. ERPs in humans can be divided into 2 categories. The early waves, or components peaking roughly within the first 100 milliseconds after stimulus, are termed ‘sensory’ or ‘exogenous’ as they depend largely on the physical parameters of the stimulus. In contrast, ERPs generated in later parts reflect the manner in which the subject evaluates the stimulus and are termed ‘cognitive’ or ‘endogenous’ ERPs as they examine information processing. The waveforms are described according to latency and amplitude .

11. Electrogastrography (EGG)

12. Electromyography

13. What is EMG It is an instrument - recording the electrical activity of the muscles to determine whether the muscle is contracting or not. The record is known as an electromyogram. Study of neuromuscular function is also possible by using EMG. Muscular contractions are caused by the depolarization of muscle fibers. Similarly the recording of peripheral nerves action potentials is called as electro neurography.

14. ELECTRODES USED FOR EMG Two types of electrodes: Surface electrodes- Usually this electrode is used for EMG. But by using this electrode, it is not possible to take the deeper potential. Needle electrodes – These are inserted into tissue or closer to tissue to measure the electrical activity of muscle.

15. EMG RECORDING SETUP

16. MEASUREMENT OF CONDUCTION VELOCITY IN MOOR NERVES

17. Steps: Measurement of conduction velocity Stimulate is applied at point A Electrical activity of muscle is measured at point B The space between A and B is noted as l1 meters. The time delay between applying stimulus and receiving action potential is known as latency. This time delay is denoted as t1 second. Now change the position of A into C. Now the space is reduced. It is noted as l2meters. The time delay noted is t2 second. Usually, l2<l1 and t2 <t1. Now , the conduction velocity is given as , V= l1-l2/t1-t2. Usually V= 50 m/sec. If V<40 m/s. It means there is some disorder in nerve conduction. Thus conduction velocity is measured in motor nerves. Skeletal muscle is organized functionally on the basis of the motor unit.

18. EMG Electrodes Fine wire Surface Electrodes Needle electrode

19. Typical EMG recording Time axis (msec)  Amplitude (mv)  Average amplitude over a time interval = 0

20. PCG-PHONOCARDIOGRAM The graphical record of heart sound is known as Phono Cardiogram. The device which is used to measure heart sound is known as phonocardiograph. Auscultation: The technique of listening sound produced by organs and vessels of the body is known as auscultation. In abnormal heart additional sounds are heard between the normal heart sound. These additional sounds are known as murmurs. Murmurs is generally caused by improper opening of the valves or by regurgitation.

21. Classification of Heart Sound It is divided into four types: Valve closure sound This sound occurs at the beginning of systole and at the beginning of diastole. Ventricular filling sound This sound is occurred at the time of filling of the ventricles. Valve opening sound This sound occurs at the time of opening of atrio- ventricular valves and semi lunar valves. Extra cardiac sound This sound occur in mid systole or late systole or early diastole Systole: The contraction of the heart muscle. The systolic pressure is 120mm of Hg. Diastole: The relaxation of the heart muscle. The diastolic pressure is 80 mm of Hg.

22. PCG RECORDING SETUP Positions Recommended for placing microphone

23. Relationship between heart sound and functions of cardiovascular system

24. PCG WAVEFORM

25. Mitral regurgitation murmur - In this murmur, blood flows in backward direction through the mitral valve during systole. Aortic regurgitation murmur – During diastole, sound is heard. In diastole blood flows in the backward direction from aorta to left ventricles when valves are damaged, then this sound is heard. Mitral stenosis murmur – This murmur is produced when blood is passed from left atrium to left ventricle. This sound is very weak.