Active Electric Biosignals Part III: Biosignals of f Next Organs

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1 Active Electric Biosignals Part III: Biosignals of f Next Organs Assoc. Prof. Katarína Kozlíkov ková,, RN., PhD. IMPhBPhITM FM CU in Bratislava katarina.kozlikova@fmed.uniba.sk The presentation is a part of the project KEGA 004UK- (MESR&S SR): Electromagnetic biosignals and electromagnetic radiation electronic education of Medical Biophysics (creation of e-learning e courses) Principal investigator: Assoc. Prof. Katarína Kozlíkov ková,, RN., PhD.

2 KEGA 004UK- Active Electric Biosignals III Contents Electric biosignals of skeletal muscles Electromyography Electric biosignals of the brain Electroencephalography Electrocorticography Electric biosignals of the stomach Electrogastrography Electric biosignals of the eyes Electroretinography Electrooculography 2

3 Electric Biosignals of Skeletal Muscles

4 KEGA 004UK- Electromyography Electromyography Measures and records the activity of contracting muscles in response to electrical stimulation to check the health of the muscles and the nerves that control the muscles Electromyogram Graphical output, a record of the intrinsic electric activity in skeletal muscle A record of electric potentials induced by voluntary muscular contraction Electromyograph An instrument used to perform electromyography 4

5 KEGA 004UK- Electromyography Background The voluntary function of the skeletal muscle (the contraction) depends upon the of the motor nerve functions and the nerve-muscle connection A single motor neuron innervates several muscle fibres A motor neuron together with its innervated muscle fibre constitutes a motor unit Electromyography studies functions connected with the motor units Functional diagnosis of the peripheral nerves Two types of myofilaments: actin myosin Principle of muscle contraction. [Cit ] Available at: 5

KEGA 004UK- Electromyography Principle Registration of the electric activity in skeletal muscles Resultant action potential of several motor units Surface electrode placed at the

example of muscle contraction of different intensity. [Cit. 9. 11. 2007] Available at: http://www.lib.mcg.edu/edu/eshuphysio/program/sectio n2/2ch6/2ch6img/elec1.

6 KEGA 004UK- Electromyography Principle Registration of the electric activity in skeletal muscles Resultant action potential of several motor units Surface electrode placed at the skin surface Propagation of the excitation in one nerve fibre and its transmission from the motor neuron to a muscle fibre examination in a single motor unit Needle electrode An example of muscle contraction of different intensity. [Cit ] Available at: n2/2ch6/2ch6img/elec1.jpg Principle of electromyography and an example of a record during muscle contraction. [Cit ] Available at: /section2/2ch6/2ch6img/elec1.jpg 6

KEGA 004UK- Electromyography Application A needle electrode (stimulating electrode ) is inserted into the muscle A surface electrode can be used as well that is placed over the muscle Electric

7 KEGA 004UK- Electromyography Application A needle electrode (stimulating electrode ) is inserted into the muscle A surface electrode can be used as well that is placed over the muscle Electric activity is observed On recording electrodes is measured The time delay between the deflections The amplitudes An example of electromyography. [Cit ] Available at: 7

8 Electric Biosignals of the Brain

9 KEGA 004UK- Electroencephalography Electroencephalography (EEG) Measures and records the activity of the macrorhytm of the cerebral neurons, associated with the function of the central nervous system The process of recording brain wave activity Electroencephalogram Graphical output, a record of the electric activity in brain cells Electroencephalograph An instrument for receiving and recording the electric potential produced by the brain cells 9

10 Electroencephalography Background (1) KEGA 004UK- The electric behaviour of a brain neuron corresponds to the behaviour of excitable cells Resting potential -70 mv It has a positive peak of the action potential Amplitude of the nerve impulse 100 mv Duration of the nerve impulse 1 ms Microrhythm Potential change produced by the action potential appearing in the individual functioning nerve cell 10

11 Electroencephalography Background (2) KEGA 004UK- The number of nerve cells in the brain ~ Cortical neurons are strongly interconnected The surface of a single neuron may be covered with to synapses Macrorhythm The resultant produced by the action potentials of the cerebral neurons 11

Electroencephalography Lead Systems KEGA 004UK- Different lead systems can be used The standardised 10-20 system 21 electrodes located on the surface of the scalp

be used Surface electrodes AgCl small discs Location of electrodes according to the lead system 10-20. [Cit. 5. 4. 2011] Available at: https://www.eee.hku.hk/courses.

12 Electroencephalography Lead Systems KEGA 004UK- Different lead systems can be used The standardised system 21 electrodes located on the surface of the scalp Reference points nasion and inion Skull perimeters in the transverse and median planes are measured and divided into 10 % and 20 % intervals Additional electrodes can be used Surface electrodes AgCl small discs Location of electrodes according to the lead system [Cit ] Available at: elec6081/10-20placement.gif Reference points nasion and inion for the lead system [Cit ] Available at: 12

Electroencephalography Registration KEGA 004UK- Different possibilities of registration Bipolar leads (see figure A) Potential difference between pairs of electrodes (placed relatively close each

13 Electroencephalography Registration KEGA 004UK- Different possibilities of registration Bipolar leads (see figure A) Potential difference between pairs of electrodes (placed relatively close each other) is measured Unipolar leads (see figure B) Potential of each electrode is compared to the reference electrode Created as the average of all electrodes A neutral electrode located usually at the earlobe Bipolar and unipolar measurements. [Cit ] Available at: 13

14 Electroencephalography Outcome Waves (1) KEGA 004UK- EEG waves are characterised by Frequencies (normal range 0.1 Hz 100 Hz) Amplitudes (normal range 5 µv 200 µv) In general, the amplitude decreases as the frequency increases In pathology, frequencies are rather low, amplitudes increase to several hundreds of microvolts The EEG signal is closely related to the level of consciousness of the person 14

15 Electroencephalography Outcome Waves (2) KEGA 004UK- Simultaneous electroencephalograms are recorded lead systems Asymmetrical activity is often an indication of brain disease, therefore, the right side and the left side signals are compared The record in the individual channels consist of superposition of several waves of different frequencies and different amplitudes Separation of individual components of definite frequencies and amplitudes requires appropriate mathematical analysis by computer 15

16 KEGA 004UK- Electroencephalography Outcome Waves (3) Table 1: Four typical EEG waves EEG wave Frequency [Hz] State of typical occurrence Beta awake, focused, problem solving, eyes open Alpha 8-13 awake, non-focused, relaxed, eyes closed Theta 4-7 light sleep Delta deep sleep 16

17 KEGA 004UK- Electroencephalography Outcome Waves (4) Examples of typical EEG waves. [Cit ] Available at: EEG activity dependence on the level of consciousness. [Cit ] Available at: 17

18 KEGA 004UK- Electroencephalography Outcome EEG Brain Mapping (1) Other names Quantitative electroencephalography EEG topography Principle Brain activity simultaneously recorded in many channels Display Distribution of potentials Distribution of wave frequencies (different frequencies) Distribution of intensities of one frequency interval (usually corresponding to one wave) 18

KEGA 004UK- Electroencephalography Outcome EEG Brain Mapping (2) On the left Abnormal activity of the brain cortex On the right Normal activity Distribution of frequency intensities in form of

19 KEGA 004UK- Electroencephalography Outcome EEG Brain Mapping (2) On the left Abnormal activity of the brain cortex On the right Normal activity Distribution of frequency intensities in form of standard deviations from the mean. [Cit ] Available at: 011/01/eeg-brain-mapping.html Excess amount of slow brainwave activity from a person with a long history of depression Red colour the highest activity 19

KEGA 004UK- Electrocorticography Electric activity of the brain Electrodes are

electrodes In surgical interventions Surface electrodes at electrocorticography.

jpg Detail of surface electrode placement at electrocorticography and a needle

20 KEGA 004UK- Electrocorticography Electric activity of the brain Electrodes are placed directly at the brain surface (cortex) Surface microelectrodes Needle electrodes In surgical interventions Surface electrodes at electrocorticography. [Cit ] Available at: Detail of surface electrode placement at electrocorticography and a needle electrode. [Cit ] Available at: 20

21 Electric Biosignals of the Stomach

22 KEGA 004UK- Electrogastrography Background The electric activity of the stomach is correlated to its contractile activity The peristaltic contractions are responsible for mixing and emptying food When gastric contractions occur, a sinusoidal shaped wave is detected, which is believed to be the resultant of the overall electrical activity of the stomach, and thus includes the electrical control activity and electrical response activity 22

23 KEGA 004UK- Electrogastrography Principle Electrogastrography is the recording and measurement of gastric myoelectrical activity Done to determine if abnormal electrical activity of the stomach causes nausea, vomiting or abdominal pain Electrodes are placed on the on the upper abdomen, along the gastro-duodenal axis Placement of electrodeses during EGG recording. [Cit ] Available at: 23

24 KEGA 004UK- Electrogastrography Outcome Meal ingestion increases the amplitude of the EGG signal Increased antral contractility Mechanical distension of the stomach Normal frequency 3 cycles/min Gastric dysrhythmias Tachygastria 4 cycles/min Bradygastria 2 cycles/min EGG record and spectral analysis. [Cit ] Available at: full/ / j x 24

25 Electric Biosignals of the Eyes

$KEGA 004UK- Basic Structure of the Eye Refractive media, through which the light rays pass before reaching the retina Cornea the transparent part of the sclera Anterior chamber filled with aqueous$

26 KEGA 004UK- Basic Structure of the Eye Refractive media, through which the light rays pass before reaching the retina Cornea the transparent part of the sclera Anterior chamber filled with aqueous humour Crystalline biconvex lens Vitreous chamber filled with gelatinous vitreous body Horizontal section of the right human eye seen from above. The anteroposterior diameter averages 24 mm. [Cit ] Available at: 26

KEGA 004UK- Structure of the Retina Cells, through which the light rays pass in the retina Ganglion cells Amacrine cells Bipolar cells Horizontal

27 KEGA 004UK- Structure of the Retina Cells, through which the light rays pass in the retina Ganglion cells Amacrine cells Bipolar cells Horizontal cells Photoreceptors Rods Cones Pigment epitelium The cellular structure of retina. [Cit ] Available at: 27

28 KEGA 004UK- Photoreceptors Cones Responsible for colour (day-light) vision Concentrated mainly in the central fovea (thin centre of the yellow spot macula lutea) About 30 µm long with diameter 5-6 µm Approximate total number Rods Responsible for night vision More sensitive to light than cones At the margin of the yellow spot and in other areas of the retina About 60 µm long with diameter 2 µm Approximate total number

KEGA 004UK- Electroretinography - Principle Unipolar leads Electrodes Different electrode Specially constructed contact lens carrying an AgCl wire, placed on the cornea Reference electrode Placed on

29 KEGA 004UK- Electroretinography - Principle Unipolar leads Electrodes Different electrode Specially constructed contact lens carrying an AgCl wire, placed on the cornea Reference electrode Placed on the forehead, temple, or earlobe Schematic representation of a subject wearing a corneal electrode for a left eye ERG response to a single flash. [Cit ] Available at: erg#method 29

30 KEGA 004UK- Electric Activity of Retina The sources of the electroretinogram arise in various layers of the retina Photopigment molecules Early receptor potential, biphasic deflection Photoreceptors Late receptor potential, hyperpolarisation Horizontal cells Bipolar cells Respond with hyperpolarisation Respond with hyperpolarisation or with depolarisation Amacrine cells The first cells, where the action potential can be generated Respond with depolarization and action potential Have negative feedback effect Ganglion cells Response with action potential Information processing and its transfer to higher-level centres of vision 30

KEGA 004UK- Electroretinography Waves a, b, c, d Amplitudes 0.1 mv Depend on the stimulating and physiological conditions Electroretinogram (ERG) recorded with a long-duration flash in the dark. [Cit.

31 KEGA 004UK- Electroretinography Waves a, b, c, d Amplitudes 0.1 mv Depend on the stimulating and physiological conditions Electroretinogram (ERG) recorded with a long-duration flash in the dark. [Cit ] Available at: ebook/duanes/pages/v3/v3c005.html The retina and an electroretinogram. [Cit ] Available at: 31

32 KEGA 004UK- Electroretinogra troretinography Signal Analyzes Measurement of amplitudes of electroretinogram waves Note the different way of determining the amplitude of the a wave (measured from zero voltage) and the b wave (measured from the minimum of the a wave) Basic ERG waves and measurement of the a wave amplitude (negative), b wave amplitude (positive) and the time t since the onset of the stimulus. [Cit ] Available at: webvision.med.utah.edu

33 Electroretinogram Physiological Variability (1) KEGA 004UK- A normal response will reveal at least two prominent waveform features The a-wave Biphasic negative-positive response <10 ms following light stimulus representing cone photoreceptor hyperpolarization The early a-wave negative peak amplitude and onset time is usually measured with respect to the stimulus onset time A later a-wave component exists that is mediated by rod depolarization which merges with the onset of the b-wave and is therefore difficult to precisely identify The b-wave Usually the largest component of the ERG Positive-going deflection in the ERG with ~50 ms onset following light stimulus Several different cell types contribute to the signal, including: Mueller (glial) cells, bipolar cells, and retinal ganglion cells Amplitude varies with stimulus intensity Amplitude is usually taken from a-wave trough to b-wave peak Time to peak is taken from time of light stimulus 33

34 Electroretinogram Physiological Variability (2) KEGA 004UK- Other ERG potentials may also be present Oscillations on the leading edge of the b-wave Measured in terms of their frequency An afterpotential following the offset of the b-wave The c-wave A biphasic cornea-positive potential Originating in the pigment epithelium, glial cells and other cell types (horizontal and off-bipolar cells) Physiological variability of the electroretinogram. [Cit ] Available at: 34

KEGA 004UK- Multifocal Electroretinogram The patient looks at a pattern of flickering hexagons. Light-sensitive retinal cells in the eyes change this light into electrical signals.

35 KEGA 004UK- Multifocal Electroretinogram The patient looks at a pattern of flickering hexagons. Light-sensitive retinal cells in the eyes change this light into electrical signals. The signals are detected by electrodes and converted into visual response maps. Each hexagon is seen by a separate bit of the retina. An example of a diagram for multifocal electroretinography. The arrangement of elements in the retina in five circles. [Cit ] Available at: 35

36 KEGA 004UK- Multifocal Electroretinogram Example The 3D multifocal ERG (top) and the 63 multifocal ERG responses (bottom) of both eyes. [Cit ] Available at: 36

KEGA 004UK- Electrooculography Background The cornea of the eye is electrically positive relative to the back of the eye Can be regarded as a single dipole oriented from the retina to the cornea The

37 KEGA 004UK- Electrooculography Background The cornea of the eye is electrically positive relative to the back of the eye Can be regarded as a single dipole oriented from the retina to the cornea The eye may be thought of as a battery Corneo-retinal potentials are well established and are in the range of mv Eye movements produce a moving (rotating) dipole source Signals that are a measure of the movement may be obtained Main application Measurement of eye movement A test of retinal function Complement to ERG The standing potential of the eye. [Cit ] Available at: 37

KEGA 004UK- Electrooculography Measurement of the resting potential of retina Not the response of retina to individual light stimuli When determining the eye movement Electrodes left and right from

38 KEGA 004UK- Electrooculography Measurement of the resting potential of retina Not the response of retina to individual light stimuli When determining the eye movement Electrodes left and right from the eye Horizontal component Electrodes over and below the eye Vertical component Electrooculogram Record Electrode placement during EOG. [Cit ] Available at: 38

39 KEGA 004UK- Electrooculogram With the eye at rest the electrodes are effectively at the same potential and no voltage is recorded. The rotation of the eye to the right results in a difference of potential Typical magnitudes From 5 20 µv/ Electrooculogram. [Cit ] Available at: 39

40 KEGA 004UK- Literature CINULČÍK, F., ŠÓTH, J. Základná príručka elektromyografických techník. EMG atlas. Osveta, Martin 1998, 100 s. ISBN DELCHAR T.A. Physics in Medical Diagnosis. Chapman&Hall, London 1997, 360 s. ISBN HRAZDIRA I., MORNSTEIN V., BOUREK A., ŠKORPÍKOVÁ J. Fundamentals of Biophysics and Medical Technology. Brno : Masaryk University, Faculty of Medicine, 2007, 325 p. ISBN JAVORKA, K. a kol. Lekárska fyziológia. Martin : Osveta, s. ISBN RONTÓ, G., TARJÁN, I. (eds.): An Introduction To Biophysics With Medical Orientation. Budapest : Akadémiai Kiadó, p. ISBN MALMIVUO, J., PLONSEY, R. Bioelectromagnetism - Principles and Applications of Bioelectric and Biomagnetic Fields. Oxford University Press, New York, 1995, 512 pp. ISBN-10: , ISBN-13: Available also in electronic form at: [cit ] WEBSTER J.G. (ed.) Medical Instrumentation. Application and Design. John Wiley & Sons, Inc., New York 1998, 710 s. ISBN Lectures on Biophysics. Portal MEFANET LF UK. Available at: Electronic sources listed directly in the text. 40

Basic Electrophysiology, the Electroretinogram (ERG) and the Electrooculogram (EOG) - Signal origins, recording methods and clinical applications

Basic Electrophysiology, the Electroretinogram (ERG) and the Electrooculogram (EOG) - Signal origins, recording methods and clinical applications The body is a complex machine consisting of the central