User's Manual

64
Indirect controls
Thecontrolsthatindirectlyaffectoutputarecontrolsaffectingimagingmode,freeze,and
depth.Theimagingmodedeterminesthenatureoftheultrasoundbeam.Tissueattenuationis
directlyrelatedtotransducerfrequency.ThehigherthePRF(puls erepetitionfrequency),the
moreoutputpulsesoccuroveraperiodoftime.
Receiver controls
Thereceivercontrolsarethegaincontrols.Receivercontrolsdonotaffectoutput.Theyshould
beused,ifpossible,toimproveimagequalitybeforeusingcontrolsthatdirectlyorindirectly
affectoutput.
Acoustic artifacts
Anacousticartifact isinformation,presentorabsentinanimage,thatdoesnotproperly
indicatethestructureorflowbeingimaged.Therearehelpfulartifactsthataidindiagnosisand
thosethathinderproperinterpretation.Examplesofartifactsinclude:
• Shadowing
• Throughtransmission
• Aliasing
• Reverberations
•Comettails
Formoreinformationondetectingandinterpretingacoustic
artifacts,seethefollowing
reference:
Kremkau,FrederickW.DiagnosticUltrasound:PrinciplesandInstruments.7thed.,W.B.
SaundersCompany,(Oct.17,2005).
Guidelines for reducing MI and TI
ThefollowingaregeneralguidelinesforreducingMIorTI.Ifmultipleparametersaregiven,
thenthebestresultsmaybeachievedbyminimizingtheseparameterssimultaneously.Insome
modeschangingtheseparameterswillnotaffectMIorTI.Changestootherparametersmay
alsoresultinMIandTIreductions.
Pleasenotethe‘MI’or‘TI’readoutontherightsideofthe
LCDscreen.