医学影像分析与实作

醫學影像分析與實作1.OUTLINEImageacquisitionmethodImageenhancementMethodsofQualitativeImageAnalysisExampleforclinicalmedicalimageanalysis2.Mostnuclearmedicineimagingsystemspresenttheirinformationasdigitalimages.Adigitalimageisstoredinthecomputerasanarrayormatrixofcountvaluesandisdisplayedbyassigningagrayorcolorscalethatdependsonthenumberofcountsineachelement.

3.DigitalImageTheImagearraysaresquarematricesthathavedimensionsrangefrom32*32upto1024*1024Innuclearmedicine:32*32,64*64,128*128,256*256,512*512,1024*1024Bytemode&wordmode

4.ImageformationFrameModeListModeDualIsotopeImaging5.Framemode X-YcoordinateBytemode:256grayscale1byte=8bitsWordmode:65535grayscale2byte=1word6.Listmode2bytedataseriesEventaddressesTimeflagListmodecanbeformattedanyframesizeListmodeneedmorememory7.SamplingSamplingsize:pixelsize(mm)=fieldofview(mm)/#ofpixelsWhatshouldthepixelsizebe?1.Thespatialresolutionofimagingsystem2.Thesmallestobjectofinterestintheimage3.Thetimeittakestoperformanyprocessingsteps.4.Theamountofstorageandarchivalspaceavailable.8.InformationDensityWhatinformationcanweexpecttoperceiveatagivencountdensity?

☆thisdependsonthesizeofthesmallestregionintheimageyouaretryingtoperceiveanditsapparentcontrasttothesurroundingbackground.※Howtodefinetheimageinformationdensity?n>k2/C2d2

n:estimatethecountdensityk:thesignal–to–noiseratio(3~5)C:imageconstrastd:imagediameter◎Imageconstrast=(objectcountdensity-backgroundcountdensity)/backgroundcountdensity9.ImageAcquisitionStaticstudiesWhole-BodyImagingDynamicstudiesGatedAcquisitionSPECTAcquisition10.DataAcquisitionMethodFrameModeListMode11.FramemodeAcquisitionPictureelements64*64128*128256*256Pixel:PictureelementSquaremosaic:Imagematrix,Imagearraypixelarray12.ResolutionSpatialResolutionTemporalResolutionEnergyResolution13.SpatialResolution Eachpixelintheimagematrixhasone-to-onecorrespondencewithagivenlocationintheplaneofNaIcrystalEx:GammacameraFOV=40cmdiameterFor64*64S.R=400/64=6.25mm/pixelFor128*128S.R=400/128=3.13mm/pixel14.StatisticalNoise15.IncreaseSpatialresolutionZoomingHardwareSoftwareZoomcan(1)decreaseBackgroundcount(2)increaseresolutionThespatialresolutionofcomputerimageisultimatelylimitbyresolutionofgammacamera16.BytemodeV.S.Wordmode1Byte=28bits=256(0-255)1Word=216bits=65536(0-65535)1Word=2Bytes17.BytemodeV.S.WordmodeBytemodeAcquisition:apixeldeepis1byteWordmodeAcquisition:apixeldeepis2byteWhatKindoftheacquisitionmodeweshouldused?Inlowcountstudies=>BytemodeInHighcountstudies=>Wordmode18.BytemodeV.S.WordmodeBytemode優點:lessmemory缺點:1.deadtime2.truncationerrorWordmode優點:1.Nodeadtime2.Notruncation缺點:morememory

Overflow:Deadtime:Truncation:19.臨床診斷上使用的應用軟體影像增強(Imageenhancement)量化分析(QualitativeImageanalysisECT影像重建(ECTimagereconstruction)20.ImageEnhancementImagesmoothingfiltersP721.ImageEnhancementNine-pointsmooth(mask)w1 w2 w3w4 w5 w6w7 w8 w911111111122.ImageEnhancement23.ImageEnhancement24.ImageEnhancementMediumsmoothHalfwaymask=>replaceaverage(weight)>50%countvalue(mask)<50%countvalue(Keep)25.26.27.ImageEnhancementEdge-enhancementfilter(sharpenmask)Mask:(2N+1)*(2N+1)28.29.ImageEnhancementPointprocessingoperationsBackgroundsubtractionGrayscalesColortranslationtableFrameprocessingoperationex:Parathyroidscanstudy30.Parathyroidsubtractuin31.ImageEnhancement-1-1-1-18-1-1-1-132.影像量化分析ROI(regionofinteresting)createHistogramcreateAnalysisROIandHistogramClinicalmathematic33.PointprocessingoperationBackgroundsubtraction(pixel-by-pixel)34.PointprocessingoperationInterpolatedbackgroundsubtraction(weight)Wa=Xb/XaWb=Xa/XbWc=Yd/YcWd=Yc/YdXa:Q距A點距離Xb:Q距B點距離Yc:Q距C點距離Yd:Q距D點距離35.GrayscalesandcolortableGrayscale(dynamicrange)thenumberofshadesofgraybetweenthesetwoextremesType:Linearexponentiallogarithmic36.Grayandcolortable37.Grayscalesandcolordisplay38.Grayscalesandcolordisplay39.Lungperfusion/ventilationratio40.Tl201myocardialperfusionstudy41.CreatingROIsAutomaticedgedetectionmethods:42.CreateROIMethod:CircularROIRectangularROIIrregularROIAutomaticROI43.CurveGenerationandAnalysisThestartingpointforanalyzingtheflowpatternquantitativelyistheconstructionofanactivity-versus-timecurve.MethodEye-ballingThemoveaveragemethodTheweightedmoving-averagemethod44.TheMovingAveragemethod45.TheMovingAveragemethod46.DatasmoothingbycurveFitting47.ClinicalMathematicinNuclearMedicineNuclearCardiologyMultiple-gateequilibriumFirstpassblood-poolStaticmyocardialperfusionstudyRenalfunctionGFRKidneyradioERPFDiureticrenography(Lasix)CaptoprilrenographyOther48.ExampleforVentricularEjectionFraction49.Multiplegatemode50.EjectionFraction51.EjectionFraction52.EjectionFraction53.EjectionFraction54.Ejectionfraction55.Gastricemptytimestudy56.Exampleforrenalfunction57.AnalysistoolsForrenalimageratio:1.Arithmeticmethod2.GeometricmethodForfunctionalimage:1.ROI(regionofinteresting)2.Histogram(Timeactivitycurve,TAC)3.Curvefitting58.Arithmeticv.s.GeometricROIinformation(RINFO)Renalimageratio59.ImageratioArithmeticmethod:anteriorview:rightkidneycount(Ra)leftkidneycount(La)posteriorview:rightkidneycount(Rp)leftkidneycount(Lp)mean:(Ra+Rp)/