Sec 4 emg

Sec 4 emg

1. ELECTROMYOGRAPHY
(EMG)
By: Mohammed Attia
SBE-310 Medical Equipment I

2. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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3. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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4. Definition
■Electromyography(EMG)isanelectro-diagnosticmedicinetechniquefor
evaluatingandrecordingtheelectricalactivityproducedbyskeletal
muscles.
■EMGisperformedusinganinstrumentcalledanelectromyographto
producearecordcalledanelectromyogram.
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5. Definition (continue…)
■Anelectromyographdetectstheelectricpotentialgeneratedbymuscle
cellswhenthesecellsareelectricallyorneurologicallyactivated.
■Thesignalscanbeanalyzedtodetectmedicalabnormalities,activation
level,orrecruitmentorder,ortoanalyzethebiomechanicsofhumanor
animalmovement.
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6. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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7. Physiological Background
■Amotorunitisdefinedasonemotorneuronandallofthemusclefibersit
innervates.
■Whenamotorunitfires,theimpulse(calledanactionpotential)iscarried
downthemotorneurontothemuscle.
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■Theareawherethenerve
contactsthemuscleiscalled
theneuromuscularjunction,
orthemotorendplate.

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9. Physiological Background(continue…)
■Aftertheactionpotentialistransmittedacrosstheneuromuscular
junction,anactionpotentialiselicitedinalloftheinnervatedmuscle
fibersofthatparticularmotorunit.
■Thesumofallthiselectricalactivityisknownasamotorunitaction
potential(MUAP).
■Thiselectrophysiologicactivityfrommultiplemotorunitsisthesignal
typicallyevaluatedduringanEMG.
■Thecompositionofthemotorunit,thenumberofmusclefibrespermotor
unit,themetabolictypeofmusclefibresandmanyotherfactorsaffectthe
shapeofthemotorunitpotentialsinthemyogram.
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10. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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11. Block diagram
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12. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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13. Medical uses
■EMGtestinghasavarietyofclinicalandbiomedicalapplications:
–EMGisusedasadiagnosticstoolforidentifyingneuromuscular
diseases,or
–asaresearchtoolforstudyingkinesiology,anddisordersofmotor
control.
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–EMGsignalsaresometimesused
toguidebotulinumtoxinor
phenolinjectionsintomuscles.
–EMGsignalsarealsousedasa
controlsignalforprosthetic
devicessuchasprosthetichands,
arms,andlowerlimbs.

14. Medical uses(continue…)
■OnebasicfunctionofEMGistoseehowwellamusclecanbeactivated.
■Themostcommonwaythatcanbedeterminedisbyperforminga
maximalvoluntarycontraction(MVC)ofthemusclethatisbeingtested.
■Muscleforce,whichismeasuredmechanically,typicallycorrelateshighly
withmeasuresofEMGactivationofmuscle.
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15. Medical uses(continue…)
■EMGcanalsobeusedforindicatingtheamountoffatigueinamuscle.
ThefollowingchangesintheEMGsignalcansignifymusclefatigue:
–anincreaseinthemeanabsolutevalueofthesignal,increaseinthe
amplitudeanddurationofthemuscleactionpotentialandanoverall
shifttolowerfrequencies.
■Monitoringthechangesofdifferentfrequencychangesthemostcommon
wayofusingEMGtodeterminelevelsoffatigue.
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16. Medical uses(continue…)
■EMGisusuallyperformedwithanotherelectrodiagnosticmedicinetest
thatmeasurestheconductingfunctionofnerves.Thisiscalledanerve
conductionstudies(NCS).
■NeedleEMGandNCSsaretypicallyindicatedwhenthereis
–paininthelimbs,
–weaknessfromspinalnervecompression,or
–concernaboutsomeotherneurologicinjuryordisorder
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18. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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19. Two kinds of EMG
■TherearetwokindsofEMG:
–surfaceEMGand
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–intramuscularEMG.

20. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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21. Surface EMG
■SurfaceEMGassessesmusclefunctionbyrecordingmuscleactivityfrom
thesurfaceabovethemuscleontheskin.
■Surfaceelectrodesareabletoprovideonlyalimitedassessmentofthe
muscleactivity.
■SurfaceEMGcanberecordedbyapairofelectrodesorbyamore
complexarrayofmultipleelectrodes.
■MorethanoneelectrodeisneededbecauseEMGrecordingsdisplaythe
potentialdifference(voltagedifference)betweentwoseparateelectrodes.
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22. Surface EMG (continue…)
■Limitationsofthisapproacharethefactthatsurfaceelectroderecordings
–arerestrictedtosuperficialmuscles,
–areinfluencedbythedepthofthesubcutaneoustissueatthesiteof
therecordingwhichcanbehighlyvariable
–dependingoftheweightofapatient,themorebodyfatanindividual
has,theweakertheEMGsignal
–andcannotreliablydiscriminatebetweenthedischagresofadjacent
muscles.
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23. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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24. Intramuscular EMG
■IntramuscularEMGcanbeperformedusingavarietyofdifferenttypesof
recordingelectrodes.
–Thesimplestapproachisamonopolarneedleelectrode.
■Thiscanbeafinewireinsertedintoamusclewithasurfaceelectrodeas
areference;
■ortwofinewiresinsertedintomusclereferencedtoeachother.
■Mostcommonlyfinewirerecordingsareforresearchorkinesiology
studies.
■DiagnosticmonopolarEMGelectrodesaretypicallyinsulatedandstiff
enoughtopenetrateskin,withonlythetipexposedusingasurface
electrodeforreference.
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25. Intramuscular EMG (continue…)
■Needlesforinjectingtherapeuticbotulinumtoxinorphenolaretypically
monopolarelectrodesthatuseasurfacereference.
■Inthiscase,itisusedbothtorecordsignalsandtoinject.
–Slightlymorecomplexindesignistheconcentricneedleelectrode.
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26. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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27. EMG machine types
■ConventionalEMGsystem
–Itisbasedonneedleorsurfaceelectrodes
–ItcouldcontainmorethanoneEMG
channelUsedinhospitalsandclinics
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28. EMG machine types (continue…)
■PortableEMGsystem
–Itisusedforout-doorinvestigationand
wellasinclinicalpractice.
–Sometypesusewirelessgelelectrodes
appliedtotheskinoftheuser,
–Then,electrodesamplifythesignal
receivedbytheelectromyogram.
–Thedataisthentransferredtothe
computerandanalyzedinreal-time.
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29. EMG machine types (continue…)
■NOVIIWIRELESSPATCHSYSTEMisawearabledevicedesignedfor
highBMI(BodyMassIndex)patients.
■Thissmall,wearabledeviceenablesaccuratewithnobeltsandcords,it
improvespatients'comfortandfreedomduringthebirthingprocess.
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30. Outlines
■Definition
■PhysiologicalBackground
■Blockdiagram
■Medicaluses
■TwokindsofEMG
■SurfaceEMG
■IntramuscularEMG
■EMGmachinetypes
■EMGartifacts
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31. EMG artifacts
■PhysiologicalNoise:
–ECG,EOG,respiratorysignals,etc.
–Reducedbyproperpositioningofthesensors(locationand
orientation).
■AmbientNoise:
–Powerlineradiation(50,60Hz)
–Removedbydifferentialamplification
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32. EMG artifacts (continue…)
■BaselineNoise:
–Electro-chemicalnoise(skin-electrodeinterface)
–Reducedbyeffectiveskinpreparation
■MovementArtifactnoise
–Movementofelectrodewithrespecttotheskin
–Reducedbyeffectiveskinpreparation,properfixationofthesensor
totheskinandfiltering
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