bmiintroduction

8/4/2019 BMIIntroduction

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Biosignals



What is a Biosignal?

electrical, such as the depolarization of a nerve

or muscle cell membrane,mechanical, such as the sound generated byopening and closing of heart valves orchemical, such as pressure values of blood

gases, PO2 and PCO2.



Importance of Biosignals

•diagnosis

•patient monitoring

•biomedical research



Stages of BiosignalProcessing

patient sensorsanalog

processingA/D

conversioncomputer

pressure,temperatu

re,pH level,

etc.

signal inelectrica

l

form

isolatedand

amplifiedsignal

digitizedsignal

Signal acquisition



- Information is associated with a signal.- Information is always carried by some physical quantity,

usually it is signal.

BIOLOGICAL SIGNALS

The signal, or information, may refer to the state of the system, tosome process, etc.parameter of status - e.g. body temperature.

- the signal associated with this iscontinuous, and its magnitude is approximatelyconstant

- the blood sugar concentration is animportant indicator of the metabolism

Definition:A quantity of matter, resp. change of quantity,carrying or storing information is called a signal.

periodic processes - the ECG signal associated withthe heart function.



Biological signals

Biological systems - open dynamical systems, which areenable to generate, receive, process andemit informations

Input informations – reflect to the health conditions

•Biological signals are generated in life organism

- created by vital manifestation of organism or by stimulusfrom

external space, which may affect vital manifestation

- velocity changes are characterized by large variability

are all signals that are produced by organswithin a body.

• Mediated biological signals

- originate by interaction of organism i.e. with radiation,ultraviolet wave or with the magnetic field.

diagnostic application



Biological signals are a manifestation of activities of verycomplex biological systems, representing real living object.These signals are generated directly by this object.Biological signals are caused by mechanical, chemical or

electrical activities. - ELECTRICAL SIGNALS are either the local electrical changes or the

generalized electrical changes, representedby action potential.

Action potentials are the sources

of biological signals. They aregenerated by membranes or muscle fibers.

Living body represents a kind of a spatial conductor. The spreading of APs through such conductor creates the electricfield. Scanning electrical signals with

different frequency and intensity can beprocessed and analyzed by various methodsto obtain informations about living systemsor clinical applications.

ECG, EEG, EMG, ENG



- NON-ELECTRICAL SIGNALS have to be transformed intoelectrical signals

- e.g. blood pressure, respiratory pressures, volumes, flows,body temperature

BIOLOGICAL SIGNALS

a) Measurement of respiratory pressuresMeasurement of blood pressure (Direct method) - electromanometers

equipped with pressure transducers working on one of those threeprinciples:

tensometric, capacitive, inductive.

b) Measurement of blood flow by an electromagnetic flowmeter orby the ultrasound detectors.

c) Measurement of air flow by pneumotochograph

d) Measurement of air volumes by spirometers

e) Measurement of body temperature by thermometer



FOR RECORDING OF

ELECTRICAL SIGNALS we need:

• Electrodes• Amplifier with Filter• Oscilloscope• Chart Recorder or

Computer (with AD Converter)

FOR RECORDING OFNON-ELECTRIC SIGNALS we need:

• Transducer• Amplifier• Chart Recorder or• Computer (with AD Converter)

BIOLOGICAL SIGNALS



1. ELECTRODES - metals, glass - filled with salt solutions

Macroelectrodes - for a skin recording of ECG,EEG. The electrodes have to be moistured before using by a jell or salt solution inorder to decrease the input resistance, and then firmlyattached to the body.

For ENG or EMG recording we can use a variety of metalelectrodes with

different shape and size (plate electrodes,needle electrodes etc.)

Low impedance electrode

Microelectrodes - for intracellular or extracellular recording from

the neurons.

Microelectrodes for extracellular recording filled in with a high

concentration of NaCl solution (electrolyte)

Microelectrodes for intracellular recording filled in with the high

concentration of K solution.



•Bipolar leads - scan potential difference betweentwo places (two active electrodes) a biphasicpotential is obtained.

Bipolar limb leads I. II. III.

Bipolar chest leads CR, CL, CF

•Unipolar leads - scan potential differencebetween one active electrode and anindifferent one (the Wilson’s clip with a zeropotential) the monophasic potential isobtained.

Unipolar limb leads VR, VL, VF Unipolar augmented limb leads aVR,

aVL, aVFUnipolar chest leads V1 – V6

BIOLOGICAL SIGNALS



Recording

s:

B. MULTIUNIT ACTIVITY =

MULTIPOTENTIAL- results from mixing a variety of APs.

e.g. from the nerve or muscle tissue

A. SINGLE FIBRE NERVE ACTIVITY

orUNIT NEURONAL ACTIVITY- recording from the one nerve fibre or

one neuronal cell

BIOLOGICAL SIGNALS



2. FILTRATION - removes the unwanted components of

electrical signals obtained during recording,

e.g. using RC filters - one can remove 50 Hz of AC current,that superimposed on the taken body electrical signals.

3. AMPLIFIER - increases a low input signal into the higher output signal.

In medical practice the differential amplifiers are commonly used - theyconsist of two amplifiers with common output clamp. Both amplifiers havethe same degree of amplification but one of them serves as inverting.

Basic parameters: discriminating factor of the amplifierinput (output) specifications,gain,width of transmission (frequency) band

BIOLOGICAL SIGNALS



Signal Name Amplitude(mV)

Frequency range (Hz)

ECG Electrocardiogram 0.5 - 5.0 0.01 - 250

EEG Electroencefalogram 0.01 - 50.0 0.1 - 100

EMG Electromyogram(surface electrode)

0.1 - 10.0 0.01 - 10000

EMG Electromyogram(needle electrode)

0.05 - 5 0.01 - 10000

ENG Electroneurogram 0.05 – 10.0 0.01 - 1000

4. OSCILLOSCOPE-

displays the recordedelectrical signals.

BIOLOGICAL SIGNALS



5. CHART RECORDERS or COMPUTERSrecord the curve of signals orstore the parameters of signal within the memory,

on-line or of-line recording digital transform – analog signal is transformed into

digital form by AD Converter sampled signal

subsequent processing and evaluation of signals.

BIOLOGICAL SIGNALS



BIOLOGICAL SIGNALS -EVALUATION

Amplitude of particular wavesand oscillations:

P = 1 to 3 mm, R = 7 to 15 mm,T = 3 to 5 mm, Q and S = -3 to

-5 mm

Wave P – depolarizationof atrium (0.09s – 0.11) s

Interval PQ – timenecessary for transmission of irritationfrom the atrium to theventricles 0.12 s – 0.2 s

Complex QRS –depolarization of ventricles

Wave T - depolarization of

ventricle



BIOLOGICAL SIGNALScan be processed and analyzed by computer analysis with large

number of methods:

Mapping of frequenciesThe computer displays model of the human head andpositioning of the electrodes. The different frequencies

are displayed with different colors in relation to time.

is basis for establishing of diagnosis. Frequencycharacteristic determines which frequencies areincluded in a signal.

Frequency characteristics

Spectral analysis

provides more transparent insight in spectrum of signal frequencies in relation to time. Themagnitude of amplitude expresses correspondingcolor depth according to the chosen scale.

Dominant frequency is 10Hz during 7 seconds of measurement, and amplitude is 32 mV.



ActionPotential



Action Potential = opening of sodium andpotassium channels



Action Potential

K+-channels

Na+-channels

V

m

excitable cell

time

restingpotential



proceeding AP in MUSCLE



equivalent Current Dipole



Active and Passive Transport

chemical (concentration) + electric gradient

electro-chemical potential on membrane

!!! Cell INSIDE is NEGATIVE compare to OUTSIDE(in rest usually –75mV)



Excitable cell: NEURON

structure:

Ø dendrites withsynapses

Ø

bodyØ axon with myelin and

synapses

function:

Ø thresholding of inputsignals

Ø integration (temporaland spacial) of input signals

Ø generation of actionotentials



Synapse



HOW to measure potentials ?

by electrodes - intracellular,- extracellular,- superficial

indirectly – by recording of chargespread ... probes (e.g.fluorescence)

FROM WHERE to measure potentials ?

- from whole body, organ, tissue slices, tissueculture, isolated cell



Types of biosignals

Synaptic potentials – excitatory pre- / post-synapticpotentials, inhibitory pre- / post-postsynaptic potentials mostly they don’tcause AP because of weak time and spacialsummations (correlation) … they don’treach threshold for AP

Unit activity – activity of one neuron, ACTIONPOTENTIALS

Population response – summary response of neuronalpopulation

APs of thousands of neurons

Evoked potentials – response of sensory pathway to



Evoked potentials

… averaged signal of many

cells

… recorded from:

Cerebralcortex

Brainstem

Spinal cord

Peripheralnerves

…



Excitable cell: NEURON andMUSCLE CELL



Striated muscles

skeletal muscle – controlled by CNS via moto-neurons

heart muscle - not controlled by CNS

- refractory phase is longer than contraction(systolic) a relaxation (diastolic) time

Smooth muscles – not controlled by CNS, but byautonomic system



Heart



Atrial systole Ventricularsystole

Heart



cardiac dipol added up the local dipols:

Heart



cardiac cycleHeart



cardiac vector field in transverse

plane

M

Heart



cardiac vector field

ϕ =const

Heart



electrical activity of heart conducted thru

ions in body to surface

l d i



Normal conductionpathway:

SA node -> atrial muscle ->AV node -> bundle of His ->

Left and Right BundleBranches -> Ventricularmuscle



Types of ECG Recordings

Bipolar leads recordvoltage betweenelectrodes placed onwrists & legs (right legis ground)Lead I recordsbetween right arm &

left armLead II: right arm &left legLead III: left arm & left

leg



3 distinct waves are produced during cardiaccycle

P wave caused by atrial depolarization

QRS complex caused by ventriculardepolarization

T wave results from ventricular repolarization

(bl k) l d d



arm (black) electrode andthe left leg (red)

electrode, which"augments" the signalstrength of the positiveelectrode on the right arm:



ElectroCardioGram

Change of electric potentialheart muscle activation

atrium depolarization

3 diff. recording schemes:Einthoven, Goldberger,

Wilson

Frequency = 1-2

Hz !

Heart



2-dimensional recording

Heart



Hea



47

Einthoven’s triangle

Heart



ElectroEncefaloGram

Waves:

•

Delta: < 4 Hz ... sleeping, in awakeness pathological

• Theta: 4.5 -8 Hz ... drowsiness in children, pathological inaduls

(hyperventilation, hypnosis, ...)

• Alfa: 8.5 -12 Hz ... relaxation physical / mental

• Beta: 12 - 30 Hz ... wakefulness, active concentration

• Gama: 30–80 Hz …higher mental activity including perception

and consciousness

Brain



Biosignals Recording:

ElectroMyoGraphy – electric activity of skeletalmuscles

ElectroRetinoGraphy – electric activity of retina

ElectroOculoGraphy – electric activity of eyemovements

ElectroHysteroGraphy – electric activity of hystera(uterus)

ElectroGasteroGraphy – electric activity of stomach

MagnetoEncephaloGraphy – electric activity of brain



OtherBiopotentials?

• ECG• EEG•

EMG• EGG• ERG• …

• Temperature

•

Motion• pH• pO2• Chemicals•

…

Other SignalSources?



Electrode



Electrodelabel (in theUSA)

Electrode placement

RA On the right arm, avoiding thick muscle.

LA In the same location that RA was placed, but on the left arm.

RL On the right leg, lateral calf muscle

LL In the same location that RL was placed, but on the left leg.

V1In the fourth intercostal space (between ribs 4 & 5) just to the right of the sternum (breastbone).

V2In the fourth intercostal space (between ribs 4 & 5) just to the left of

the sternum.V3 Between leads V2 and V4.

V4In the fifth intercostal space (between ribs 5 & 6) in the mid-clavicular line (the imaginary line that extends down from themidpoint of the clavicle (collarbone)).

V5

Horizontally even with V4, but in the anterior auxiliary line. (Theanterior auxillary line is the imaginary line that runs down from thepoint midway between the middle of the clavicle and the lateral endof the clavicle; the lateral end of the collarbone is the end closer tothe arm.)

V6Horizontally even with V4 and V5 in the mid auxiliary line. (Themidaxillary line is the imaginary line that extends down from themiddle of the patient's armpit.)



lead may refer to the tracing of the voltagedifference between two of the electrodes and

is what is actually produced by the ECGrecorder

Lead I" (lead one) is the voltage between theright arm electrode and the left armelectrode, whereas "Lead II" (lead two) is thevoltage between the right limb and the feet.

Twelve of this type of lead form a "12-lead"ECG

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