DuringDoppleracquisitiontheangleofbloodflowmaynotbedirectlytowardorawayfromthetransducer.Toensureaccuratedisplayofbloodflowvelocity,theanglebetweentheultrasoundbeamandbloodflowisincludedinthevelocitycalculation.Accuracyofthemeanvelocitycalculationdependsonanaverageofallvelocitieswithinthespectrum.Ifasmallsamplevolumesizeisusedforthistypeofmeasurement,onlyflowfromthecenterofthevesselwillbeincluded....[
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Aconflictariseswhenperformingdupleximaging.Optimalvisualizationofthevesselinreal-timeimagingrequiresthatstructuresofinterestareperpendiculartothetransducer.OptimalDopplersamplesareobtainedwhenflowisclosetoparalleltothetransduceratsmallDopplerangles.Anglecorrectedvelocitymeasurementaddressesthisissue.ItisverydifficulttocomparedataobtainedusingdifferentfrequencyDopplertransducers.Datawillchangedepen...[
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AngleofInsonationCalculationofvelocityisverydependentupontheangleofinsonationused.TheDopplerequationshowsthatthedetectedDopplershiftdependsontheangleofinsonationcosq.Thevalueofcosqchangesmorerapidlyastheangleapproaches90°.[
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VelocityRatioClassificationofarterialdiseaserequiresconsiderationofothervelocitymeasurementsbesidesmaximumvelocity.Velocityratioscomparepeaksystolicmeasurementsfromastenosistoanormalproximalsegmentofthevessel.Caremustbetakenwhenthismeasurementisperformedthatsimilaranglesofinsonationareused.Ifthevelocityratiosarecalculatedusingvelocitymeasurementsobtainedatdifferentangles,significanterrorisintroduc...[
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'Yourbrowserisnotsetuptorunthisapplication.PleasedownloadandinstalltheFlash6Player.Getithere.TheDopplerequationcanbeusedindupleximagingtoconvertfrequenciesintovelocities.ThisisbecausetheanglebetweentheDopplerbeamandthebloodvesselcanbeestimated.AnalysisofthecomponentsoftheDopplerwaveformshowsthatmanyvelocitiesaredisplayedinthespectrumandthesevelocitiesvarywithtime,duetothecardiaccycle.Thevaluemostc...[
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TheDopplerequationcanbeusedindupleximagingtoconvertfrequenciesintovelocities.ThisisbecausetheanglebetweentheDopplerbeamandthebloodvesselcanbeestimated.AnalysisofthecomponentsoftheDopplerwaveformshowsthatmanyvelocitiesaredisplayedinthespectrumandthesevelocitiesvarywithtime,duetothecardiaccycle.Thevaluemostcommonlyusedforthemeasurementofvelocityispeaksystolicflow.Thisisthemaximumvelocityinthespectru...[
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Otherflowpatternsemergewithacriticalstenosis.Theredbloodcellspassthroughthenarrowedsegmentandvorticesformdistaltothestenosiscausingareasofflowreversalwherethevesselhasreturnedtoitsnormaldiameter.
Howeveroneshouldbeawarethatflowreversalcanoccurinnormalvesselsaswell.Ithasbeenwelldocumentedthatanareaofflowreversaloccursatthenormalcarotidarterybifurcation.Flowreversalcanalsooccurwherebranchesleave...[
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杨振宁和28岁的翁MM订婚,thatisagoodnews,isn'tit?杨振宁isapersonhaswisdom,Ithinkheisagrestmanintheworld,eventhoughhehassomedrawbacks.to翁MM,shewanttomarrywithawisdomman,stillagoodthing,youknowmanypeoplejustsoshallow,superficiallyjudgethings,theythinktheyaresmart,butacturallynot,theylackofwisdom,somepeopleintheirwholelifecannotgetwisdom.if杨振宁和28岁的翁MMhappywitheachother,whatelsedotheywant?itisno...[
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健康长寿成为人类追求的生活目标，科学家们经研究认为以下10种人有望健康长寿：
身材矮者美国科学家认为，人类存在着一个适宜的高度，以便让身体的潜能得到最大限度的发挥。这个高度是：南子165-168厘米，女子159-162厘米。
稍胖（重）者美国科学家在调查600万人的体重与寿命关系时发现，稍胖的人从体能、抗病力到抗癌力，均比瘦人优，因而寿命高。
秃顶者男[
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