医学影像分析与实作课件

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1、醫學影像分析與實作.OUTLINEImageacquisitionmethodImageenhancementMethodsofQualitativeImageAnalysisExampleforclinicalmedicalimageanalysisMostnuclearmedicineimagingsystemspresenttheirinformationasdigitalimages.Adigitalimageisstoredinthecomputerasanarrayormatrixofcountvaluesand

2、isdisplayedbyassigningagrayorcolorscalethatdependsonthenumberofcountsineachelement.DigitalImageTheImagearraysaresquarematricesthathavedimensionsrangefrom32*32upto1024*1024Innuclearmedicine:32*32,64*64,128*128,256*256,512*512,1024*1024Bytemode&wordmodeImageformation

3、FrameModeListModeDualIsotopeImagingFramemodeX-YcoordinateBytemode:256grayscale1byte=8bitsWordmode:65535grayscale2byte=1wordListmode2bytedataseriesEventaddressesTimeflagListmodecanbeformattedanyframesizeListmodeneedmorememorySamplingSamplingsize:pixelsize(mm)=fieldo

4、fview(mm)/#ofpixelsWhatshouldthepixelsizebe?1.Thespatialresolutionofimagingsystem2.Thesmallestobjectofinterestintheimage3.Thetimeittakestoperformanyprocessingsteps.4.Theamountofstorageandarchivalspaceavailable.InformationDensityWhatinformationcanweexpecttoperceivea

5、tagivencountdensity?☆thisdependsonthesizeofthesmallestregionintheimageyouaretryingtoperceiveanditsapparentcontrasttothesurroundingbackground.※Howtodefinetheimageinformationdensity?n>k2/C2d2n:estimatethecountdensityk:thesignal–to–noiseratio(3~5)C:imageconstrastd:ima

6、gediameter◎Imageconstrast=(objectcountdensity-backgroundcountdensity)/backgroundcountdensityImageAcquisitionStaticstudiesWhole-BodyImagingDynamicstudiesGatedAcquisitionSPECTAcquisitionDataAcquisitionMethodFrameModeListModeFramemodeAcquisitionPictureelements64*64128

7、*128256*256Pixel:PictureelementSquaremosaic:Imagematrix,ImagearraypixelarrayResolutionSpatialResolutionTemporalResolutionEnergyResolutionSpatialResolutionEachpixelintheimagematrixhasone-to-onecorrespondencewithagivenlocationintheplaneofNaIcrystalEx:GammacameraFOV=4

8、0cmdiameterFor64*64S.R=400/64=6.25mm/pixelFor128*128S.R=400/128=3.13mm/pixelStatisticalNoiseIncreaseSpatialresolutionZoomingHardwareSoftwareZoomc