超声彩色多普勒colordoppler课件

《超声彩色多普勒colordoppler课件》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、DopplerPrinciplesColorPrinciplesTheDifferencesInGrayscale,strongechoreflectionscausepixelstobedisplayed.InColorandDoppler,changesinfrequencycausepixelstobecolored.ADopplerProcessorTheDopplerprocessorputsadotonthe“spectrum”basedonthevelocityofamovingobject.Dopple

2、rProcessorWhenthereareobjectsmovingatdifferentspeeds,theDopplerprocessordisplaysadotforeachobject.DopplerProcessorTheverticalpositionrepresentstheobject’svelocity.DopplerProcessorWhenseveralobjectsmoveatthesamevelocity,thecorrespondingdotonthespectrumisbrighter.

3、DopplerProcessorDopplerInformationVelocityTurbulenceIntensityThereare3keypiecesofinformationinaDopplersignalIngeneral,flowtowardthetransducerwillbeabovethebaseline,andflowawayfromthetransducerwillbebelowthebaseline.PopQuiz1.Describe3keydifferencesbetweenthetwoDo

4、pplerWaveformsbelow.2.Matchthewaveformwiththesamplevolumeposition.AB21TheAngleProblemIftheflowisn’tparalleltotheultrasoundbeam,theultrasoundsystemonlysee’saportionofthevelocity.ActualVelocityApparentVelocityTheAngleProblemThetransduceronly“sees”aportionofthetota

5、lvelocity.TheAngleProblemOntheotherside,theapparentdirectionappearstobeopposite,eventhoughtheflowdirectionisthesame!TheAngleProblemAndinthecenter...thereisNOapparentflow.Dopplerprocessorscannotseeflowperpendiculartotheultrasoundbeam.TheDopplerEquationDon’tmemori

6、zethis.Butrememberacoupleofrulesofthumb:WHATSOWHATTheapparentvelocityisYouwon’tgetmuchflowwhendependentontheangle()theangleisnear90°ThehigherthetransmitLowerfrequencyprobesarefrequency(ft),thelowertheusedtomeasurehigherdetectedvelocityvelocitiesv=fd·c2ftcos

7、TheAliasingProblemWhatifyoucheckedyourclockevery5seconds...whatwouldyouseeonthesecondhand?1234TheAliasingProblemWhathappensifyoulookatthesameclockevery55seconds?111098PopQuizHowoftendoyouhavetolookattheclocktocorrectlydeterminethedirectionofthesecondhand?12PopQu

8、izHowoftendoyouhavetolookattheclocktocorrectlydeterminethedirectionofthesecondhand?126Every29.99999secondsPopQuizHowfastcantheclockbe,ifyou’regoingtoaccuratelydemonst