S BY Da_Trainee

7/28/2019 S BY Da_Trainee

1/15

MyOwnU/SNotes

!

Da_Traine

e

4th Apri

l2013


2/15

Wha

tisU/S

?

} Ultrasoundusessoundwaveproduceimages.

} Soundisavibraonthattravel

throughamediumorair,andc

heardwhentheyreachaperson

animalsear.Forhumans,theau

soundrangesbetween16Hzand

20,000Hz(20KHz).Thehearingfo

otherspeciescanbemuchhigher

20KHz,thesehigherwavesarerefe

toasUltrasound.

} Thespeedbywhichthewavestravethroughamediumisdeterminedby

densityandsffnessofthemedium.


3/15

Prope

rtyo

f

s

ounds

} Thesoundwavesintensityan

amplitudechangesasittravels

amedium,thisiscalledAOenu

Thisisthereasonwhyechoesfr

deeperstructuresareweakerth

echoesfromsuperficialstructure

} ThereareseveralsourcesofaOenuaoniname

dium.Themajo

sourceissossueabsorpon,wh

istheconversionofacouscenergy

intoheat.Theothermechanismsare

Reflecon,RefraconandScaOer.


4/15

Atten

uati

onof

U/S

} Reflecon:Thesoundwavesenboundaryoftwodifferentmedia

wavesbouncesbacktowardsthe

echo.Theangleofincidenceiside

angleofreflecon.

}Theremainingsoundwaves,travels

secondmediumorssueandisben

originalpath,resulngintheangleo

beingdifferenttotheangleoftransm

ThisisknownasRefracon.

} ScaOeroccurswhenU/Swavesencoun

mediumofnon-homogeneoussurface.

poronwillbescaOeredinarandomdir

whilemostoftheoriginalwaveconnue

originalpath.


5/15

Ultr

asoun

d

pro

ductio

n} TheU/Sproduconisbasedo

calledPulse-echoprinciple.T

sourceoftheU/Swaveisthe

Pizoelectricwhichisplacedint

transducer.Thesehavetheabili

transformelectricalcurrentinto

ultrasoundwavesandviceversa.

} Itswitchesfromsendingintoliste

aboutseveralmillionmespersec

} Electricityintosound=PULSE

} Soundintoelectricity=ECH


6/15

Tran

sducer

s

}Thereareseveraltypetransducers:}Curvedprobe

}Linearprobe

}Intra-cavityprobe


7/15

Tran

sducer

s

compo

nent

s


8/15

Curve

dpr

obe

Thisisalsoknownasprobe,itisusedforscofthedeeperstructur

crystalsarealignedtog

alongacurvedsurface&

causeafanningoutofth

beam.Frequency:1-8MHz

Uses:-Abdominalaorta

Biliary/liver/pancreasKUB

Trans-abdominalexaminaons


9/15

Linea

rpr

obe

} Thisprobeisdesignedfortheofthesuperficialstructures.T

crystalsarealignedinlinearfa

withintheflatheadanditprod

soundwavesinastraightline.

} Frequency:5-13MHz} Uses:-Vascularaccess(centralanperipheral)Evaluaonfor

DVT

&sossueforabscessFB

Musculoskeletaltendonbones

MusclesTescularAppendicisi

thinpaentsEvaluaonofthepleu

lineforpnemothorax,intersalfluid

andocularultrasound.


10/15

Intra

-cavity

prob

e} Intra-cavityprobeswereintro

overcometheproblemwithim

deeperstructures.Theycanals

combinedwithendoscopestog

regardingdeeperlayersofhollo

viscusandthesurroundingstruc

likelymphnodes.} Frequency:7-15MHz} Uses:Tra

ns-rectalprobeforprosta

scansTrans-vaginalprobefor

gynecologyandearlyobstetricsand

trans-esophagealforechocardiograph


11/15

Freque

ncy

} Thepiezoelectriccrystatocreatesoundwave

s.T

vibrangcreatealternate

andlowpressurewhichtr

forward.

Highpressure

Lowpressure


12/15

Freque

ncy

Frequencyisthenumberofhandlowpressureinaperiod

second.nesecond

nesecond


13/15

Freque

ncy

} TheunitoffrequencyisHertz,wabbreviatedHzreferstoth

enum

persecond.} ThehigherthefrequencythebeOe

scaleresoluonandalsoprovidesim

abilitytodisnguishfinddetails.How

penetraonisreduced.

} Frequencyunits:necyclespersecond=oneHertz(Hz)

nethousandscyclepersecond=oneKiloh

nemillioncyclepersecond=oneMegaher


14/15

Term

s} Wavelength:Thedistancebe

consecuvecyclesofsound.

} Bandwidth:AllU/Stransducer

rangeoffrequenciestermed

bandwidth.} TimeGainCompensator:peratcontrolledadjustmenttocompen

fortheaOenuaonofsoundasit

travelsintothessue.

} Resolu@on:Theabilitytodifferena

structuresthatarecloselyrelated;in

termsofspace&echoamplitude

(Wavelengthdependenti.e.Frequenc

}


15/15

Imagin

g

mod

alitie

s

A-mode:Ultrasoundwavethatcomesoutthestraightpath.Thisisusedtomeasuretheleng

pthamologistwoulduseittomeasurethelen

} B-mode:(Brightness)Alsoknownasthebasicg

dimensionalimaging,referstostandardblackan

thewavemeetsthefirstwall,partofthewaveis

intotheprobe.Thestrengthofthereturningwav

brightdot.Thebrighterthedotthestrongeristhe

therestshowsjustafewdotsofadifferentbrightn

} M-Mode:UsedtovisualisethingsthatarephysicallyusedinconjunconwithB-modescanning.Usedine

cardiacvalve,fetalheartacvity,helpfulinmeasuring

variabilityofinferiorvenacavaandevaluaonoflung

pnemothorax.} Doppler:Usesfrequency

shiofsoundwavestomeasu

ColourDopplerdisplaysthemovementtowardstheprob

andawayasblue.ItishelpfulwhenaOempngtoidenf

vesselsanddifferenateitfromsurroundingstructures.P

Dopplermeasuresflowwithinanobjectbutnotthedirec

alsoreliesonfrequencyshitodetectthepresenceofflow

displaysitonecolour,usuallyorange.Itismoresensiveth

colourdopplerandpicksuponsmallflow.However,thedow

isthatunwantedmoonarfactarecommon.

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