最新CT成像原理CTbasictheoryppt课件.ppt

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1、CT成像原理CTbasictheoryComputedTomographyCTBasicsPrincipleofSpiralCTScanParameter&ImageQualityOptimizingInjectionProtocolsClinicalApplicationsX-RayDiscoveryX-raywasdiscoveredbyaGermanscientistRoentgen100yearsago.Thismadepeopleforthefirsttimebeabletoviewtheanatomystructureofhumanbod

2、ywithoutoperationButit'ssuperimposedAndwecouldn'tviewsofttissueHowdoesCTWork?Recon.&postpro.DataacquisitionX-raygenerationX-raygoesthroughcollimatorthereforepenetrateonlyanaxiallayeroftheobject,called"slice"HowdoesCTWork?PatientisplacedinthecenterofthemeasurementfieldX-rayispas

3、sedthroughthepatient’sslicefrommanydirectionalonga360°pathThetransmittedbeamsarecapturedbythedetectorswhichdigitizesthesesignalsThesedigitizedsignalscalledrawdataaresenttoacomputerwhichcreatetheCTimageHowdoesCTWork?Theobjectsliceisdividedintosmallvolumeelementscalledvoxels.Each

4、voxelisassignedavaluewhichisdependentontheaverageamountofattenuationHowisCTImagegenerated?Theattenuationvaluesaretransferredtothecomputerwheretheyarecoded&usedtocreateasliceimageHowisCTImagegenerated?CTGenerations&Design“Generation”isusedtolabelCTtube-detectordesigns3rdGenerati

5、onDesignRotatingtube&detector4thGenerationDesignFixedringdetectorSlip-ringTechnologyPoweristransmittedthroughparallelsetsofconductiveringsinsteadofelectricalcablesContinuousGantryRotationPrerequisiteforSpiralCTNonSlip-ringScannerSlip-ringScannerComputedTomographyCTBasicsPrinc

6、ipleofSpiralCTScanParameter&ImageQualityOptimizingInjectionProtocolsClinicalApplicationsWhatisSpiralScan?--just4“C”Continuouslyrotatingtube/detectorsystemContinuouslygeneratingX-rayContinuouslytablefeedContinuouslydataacquisitionReconstructionofarbitraryslices(eithercontiguouso

7、roverlapping)withinthescannedvolumeDistancebetweentheslicesiscalledIncrementABVolumeDataContinuousdataacquisitionIncrementSliceThicknessIncrement=SliceThicknessNoOverlapNoGapsContiguousImageReconstructionIncrementOverlapSliceThicknessOverlappingImageReconstructionIncremen

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