超音波影像成像原理.ppt

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1、超音波影像成像原理上課內容Analogvs.DigitalThedigitaladvantageLateralResolution(LR)HighFrequencyImaginglimitationAdvancedtechnologyWideAperture/LowF-NumberImagingNoisereducedConclusionAnalogvs.DigitalThedigitaladvantageThesignalintegritywillbemaintainedMuchgreater

2、precisionNotrequirethefrequentcalibrationReprogrammingthesize,shape,direction,andintensityofthebeamLateralresolution(LR)Thespeedofsound(v=1540m/s)Frequency(f)Wavelengthofsound(λ=v/f)Thedepthofscan(D)Apertureofthetransducer(A)HighFrequencyImaginglimit

3、ationElectronicsPrecisioninAnalogSystemsA/DConversionRatesinDigitalSystems(Nyquistsamplingtheorem)TransducerDesignandFabricationTissuePenetrationatHighFrequenciesAdvancedtechnologyADconverter(20MHz→40MHz)WideAperture/LowF-NumberImagingPhantomcompari

4、sonoflowF#(right)tohighF#(left).ChannelcountApertureWideAperture/LowF-NumberImagingPhantomcomparisonoflowF#(right)tohighF#(left).ApertureFocalzoneFramerateNoisereducedScanningfromdifferentanglesproducesdifferentartifactpatterns.Speckle,clutter,noise

5、,glint,dropoutandrefractiveshadowsaresuppressed,andrealstructuresreinforced.ConclusionWhydigital?LRapproachedCTHighfrequencyisatrendWideApertureMultiplefocalzoneNoiseisabigproblem3-Dreconstructionwillbekeypoint