CT+成像原理介绍.ppt

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1、CT成像原理介紹ComputedTomographyCTBasicsPrincipleofSpiralCTScanParameter&ImageQualityOptimizingInjectionProtocolsClinicalApplicationsX-RayDiscoveryX-raywasdiscoveredbyaGermanscientistRoentgen100yearsago.Thismadepeopleforthefirsttimebeabletoviewtheanatomystructureofhumanbodywi

2、thoutoperationButit'ssuperimposedAndwecouldn'tviewsofttissueMynameisGodfreyHounsfieldIworkfortheCentralResearchLabs.ofEMI,LtdinEnglandIdevelopedthethefirstclinicallyusefulCTscannerin1971HistoryofComputedTomographyEarly1970s1963-AlanCormackdevelopedamathematicalmethodofr

3、econstructingimagesfromx-rayprojectionsForthefirsttimewecouldview:CTBroketheBarrier-Tomographicor“Slice”anatomy-DensitydifferenceButit'stimeconsumingAndresolutionneedstobeimprovedConceptofX-rayAttenuationAnX-raybeampassingthroughthebodyisattenuated(losesitsenergy)by:Ab

4、sorptionScatteringIncidentX-rayTransmittedraySCATTEREDX-RAYSBODYTISSUEAbsorptionbythetissueisproportionaltothedensityLessdensetissueMoredensetissueMOREATTENUATIONLESSATTENUATIONHowdoesCTWork?Recon.&postpro.DataacquisitionX-raygenerationX-raygoesthroughcollimatortherefor

5、epenetrateonlyanaxiallayeroftheobject,called"slice"HowdoesCTWork?PatientisplacedinthecenterofthemeasurementfieldX-rayispassedthroughthepatient’sslicefrommanydirectionalonga360°pathThetransmittedbeamsarecapturedbythedetectorswhichdigitizesthesesignalsThesedigitizedsignal

6、scalledrawdataaresenttoacomputerwhichcreatetheCTimageHowdoesCTWork?Theobjectsliceisdividedintosmallvolumeelementscalledvoxels.EachvoxelisassignedavaluewhichisdependentontheaverageamountofattenuationHowisCTImagegenerated?Theattenuationvaluesaretransferredtothecomputerwhe

7、retheyarecoded&usedtocreateasliceimageHowisCTImagegenerated?CTGenerations&Design“Generation”isusedtolabelCTtube-detectordesigns3rdGenerationDesignRotatingtube&detector4thGenerationDesignFixedringdetectorSlip-ringTechnologyPoweristransmittedthroughparallelsetsofconductiv

8、eringsinsteadofelectricalcablesContinuousGantryRotationPrerequisiteforSpiralCTNonSlip-ringScannerSlip-ringSc