1、CTCT成像原理介绍英文成像原理介绍英文版医学知识讲解版医学知识讲解 CT Basics Principle of Spiral CT Scan Parameter&Image Quality Optimizing Injection Protocols Clinical Applications2CT成像原理介绍英文版医学知识讲解X-ray was discovered by a German scientist Roentgen 100 years ago.This made people for the first time be able toview the anatomy stru
2、cture of human body without operationBut its superimposed And we couldnt view soft tissue3CT成像原理介绍英文版医学知识讲解l My name is Godfrey Hounsfieldl I work for the Central Research Labs.of EMI,Ltd in Englandl I developed the the first clinically useful CT scanner in 1971History of Computed Tomography Early 1
3、970s1963-Alan Cormack developed a mathematical method of reconstructing images from x-ray projections4CT成像原理介绍英文版医学知识讲解 For the first time we could view:-Tomographic or“Slice”anatomy-Density differenceBut its time consumingAnd resolution needs to be improved5CT成像原理介绍英文版医学知识讲解Concept of X-ray Attenua
4、tionAn X-ray beam passing throughthe body is attenuated(loses itsenergy)by:AbsorptionScatteringIncident X-rayTransmitted rayBODYTISSUEAbsorption by the tissue is proportional to the densityLessdensetissueMoredensetissueMORE ATTENUATIONLESS ATTENUATION6CT成像原理介绍英文版医学知识讲解Recon.&postpro.Data acquisition
5、X-ray generation7CT成像原理介绍英文版医学知识讲解X-ray goes through collimator thereforepenetrate only an axial layer of the object,called slice8CT成像原理介绍英文版医学知识讲解 Patient is placed in the center of the measurement field X-ray is passed through the patients slice from many direction along a 360 path The transmitted
6、 beams are captured by the detectors which digitizes these signals These digitized signals called raw data are sent to a computer which create the CT image9CT成像原理介绍英文版医学知识讲解The object slice is divided into small volume elements called voxels.Each voxel is assigned a value which is dependent on the a
7、verage amount of attenuation10CT成像原理介绍英文版医学知识讲解The attenuation values are transferred to the computer where they are coded&used to create a slice image11CT成像原理介绍英文版医学知识讲解CT Generations&Design“Generation”is used to label CT tube-detector designs12CT成像原理介绍英文版医学知识讲解Slip-ring TechnologyPower is transmit
8、ted through parallel sets of conductive ringsinstead of electrical cables Continuous Gantry Rotation Prerequisite for Spiral CT13CT成像原理介绍英文版医学知识讲解 CT Basics Principle of Spiral CT Scan Parameter&Image Quality Optimizing Injection Protocols Clinical Applications14CT成像原理介绍英文版医学知识讲解What is Spiral Scan?
9、-just 4“C”Continuously rotating tube/detector systemContinuously generating X-rayContinuously table feedContinuously data acquisition15CT成像原理介绍英文版医学知识讲解Reconstruction of arbitraryslices(either contiguous or overlapping)within thescanned volume Distance between the slices is called IncrementABVolume
10、DataContinuous data acquisition16CT成像原理介绍英文版医学知识讲解IncrementSlice ThicknessContiguous Image Reconstruction17CT成像原理介绍英文版医学知识讲解IncrementOverlapSliceThicknessOverlapping Image Reconstruction18CT成像原理介绍英文版医学知识讲解Image Reconstruction with GapsIncrementSlice Thickness19CT成像原理介绍英文版医学知识讲解20CT成像原理介绍英文版医学知识讲解21C
11、T成像原理介绍英文版医学知识讲解 CT Basics Principle of Spiral CT Scan Parameter&Image Quality Optimizing Injection Protocols Clinical Applications22CT成像原理介绍英文版医学知识讲解Scan ParametersX-ray Tube Voltage(kVp)X-ray Tube Current(mA)Scan Time(s)Slice thickness or Collimation(mm)23CT成像原理介绍英文版医学知识讲解Table Speed&Pitch Table S
12、peed is defined as distance traveled in mm per 360 rotationPitch =Table Feed per rotation CollimationT Ta ab bl le e F Fe ee ed d C Co ol ll li imma at ti io on n P Pi it tc ch h 1 10 0 mmmm/r ro ot t1 10 0 mmmm1 1.0 01 15 5 mmmm/r ro ot t1 10 0 mmmm1 1.5 52 20 0 mmmm/r ro ot t1 10 0 mmmm2 2.0 024CT
13、成像原理介绍英文版医学知识讲解25CT成像原理介绍英文版医学知识讲解30s15s26CT成像原理介绍英文版医学知识讲解To reduce artifacts due to table motion during spiral scanning,we use a special reconstruction process called INTERPOLATIONInterpolation Algorithm27CT成像原理介绍英文版医学知识讲解28CT成像原理介绍英文版医学知识讲解29CT成像原理介绍英文版医学知识讲解Slice Sensitivity Profile(SSP)SSP desc
14、ribes the effective slice thickness of an image and to what extent anatomy within that slice contribute to the signalSSPRESOLUTIONAll points within the slice contribute equally&points outside of the slice do not contribute to the image at all.Image signalIdeal SSPZ-axis(mm)Collimation=width of x-ray
15、 beam=slice profile30CT成像原理介绍英文版医学知识讲解Slice Profile(SP)Effective slice thickness of an image Slice ProfileResolution31CT成像原理介绍英文版医学知识讲解Factors influencing SSPCollimator width collimation=SSPSpiral CTTable speed or PitchInterpolation Algorithm=mathematical process required to reconstruct axial images
16、 from the spiral volume data set32CT成像原理介绍英文版医学知识讲解Pitch&Slice Profile33CT成像原理介绍英文版医学知识讲解Slim vs Wide SSP ComparisonSlice Profile Slim%Broaden Wide%BradenPitch One 5.0 mm 0 6.3 mm 26Pitch Two 6.5 mm 30 10.8 mm 11634CT成像原理介绍英文版医学知识讲解WIDE720 degreeMore photonsSLIM464 degreeLess photons SSP Spatial res
17、olutionSSPSpatialresolutionSmoother imageNoisier image35CT成像原理介绍英文版医学知识讲解Slim-AdvantagesImproved Z ResolutionReduced partial volume artifactsSlim+extended PitchLonger coverageSame coverage with shorter scan time or thinner slicesLess radiation dose36CT成像原理介绍英文版医学知识讲解Slice Profile ComparisonC Co ol l
18、l li imma at ti io on n5 5.0 0 mmmmWWi id de eI In nt te er rp po ol la at ti io on nS Sl li immI In nt te er rp po ol la at ti io on nP Pi it tc ch h 1 1.0 06 6.3 3 mmmm5 5.0 0 mmmm%B Br ro oa ad de en ne ed d2 26 60 0P Pi it tc ch h 2 2.0 01 10 0.8 8 mmmm 6 6.5 5 mmmm%B Br ro oa ad de en ne ed d1
19、11 16 63 30 038CT成像原理介绍英文版医学知识讲解 Lesion smaller than 1cm SCAN RANGE=150mm Slice Profile=10mm Slice Profile=6.5mmOptimizing the Scanning Parameters39CT成像原理介绍英文版医学知识讲解Smallest Possible Effective Slice ThicknessDepends on the scan length&patients breath-hold compliance1 Pitch 2 to cover the whole volum
20、e in one breath-hold40CT成像原理介绍英文版医学知识讲解 CT Basics Principle of Spiral CT Scan Parameter&Image Quality Optimizing Injection Protocols Clinical Applications41CT成像原理介绍英文版医学知识讲解Peripheral vein eg.antecubital vein 19-20 gauge needle or IV catheter42CT成像原理介绍英文版医学知识讲解Tailoring Scan&Injection Protocols43CT成
21、像原理介绍英文版医学知识讲解Determines optimal scan delay for spiral CTA sequence44CT成像原理介绍英文版医学知识讲解Test Bolus Procedure45CT成像原理介绍英文版医学知识讲解Dynamic EvaluationTime-density curve Scan Delay Peak Enhancement Time Dynamic ScansROI placed in the Aorta46CT成像原理介绍英文版医学知识讲解 CT Basics Principle of Spiral CT Scan Parameter&Image Quality Optimizing Injection Protocols Clinical Applications47CT成像原理介绍英文版医学知识讲解48CT成像原理介绍英文版医学知识讲解49CT成像原理介绍英文版医学知识讲解CT Angiography50CT成像原理介绍英文版医学知识讲解3D Post-processing51CT成像原理介绍英文版医学知识讲解52CT成像原理介绍英文版医学知识讲解53CT成像原理介绍英文版医学知识讲解54CT成像原理介绍英文版医学知识讲解
