简介:Phasecontrastimagingtechniquehasbeenimprovedpromptlyinrecentyears.Amongthesetechniquesin-linephase-contrastimagingiswidelyused.Variousalgorithmsforin-linephaseretrievalhavebeenproposedsofarsuchasTIE(transportofintensityequation),CTF(contrasttransferfunction),firstborn-approximations,GSF(Gerchberg-Saxton-Fienup),etc.Bronnikov'salgorithm(BA)isatypeoflinearalgorithmthatissimpleandefficient.Butitcanonlybeusedwithoutabsorptionsituations.Inthispaper,animprovedalgorithmbasedonBAwaspresented.TheapproachaddsΔφ(x,y)tothephasemapφ_b(x,y)retrievedbyBAtomakethereconstructedphasemapmoreprecise.Further,theapproachwasevaluatedonsimulatedimagesandconfirmedtobeaccurateathigherabsorptionrates.
简介:AnewmethodofphasespectralanalysisofEEGisproposedforthecomparativeanalysisofphasespectrabetweennormalEEGandepilepticEEGsignalsbasedonthewaveletdecompositiontechnique.Byusingmultiscalewaveletdecomposition,theoriginalEEGsaremappedtoanorthogonalwaveletspace,suchthatthevariationsofphasecanbeobservedatmultiscale.Itisfoundthatthephase(andphasedifference)spectraofnormalEEGsaredistinctfromthatofepilepticEEGs.Thatisthevariationsofphase(andphasedifference)ofnormalEEGshaveadistinctperiodicpatternwiththeelectricalactivityproceedsinthebrain,butdonottheepilepticEEGs.ForepilepticEEGs,onlyatthosetransientpoints,thephasevariationsareobvious.Inordertoverifytheseresultswiththeobservationaldata,thephasevariationsofEEGsinprincipalcomponentspaceareobservedandfoundthat,thefeaturesofphasespectraisincorrespondencewiththatthewaveletspace.TheseresultsmakeitpossibletoviewthebehaviorofEEGrhythmsasadynamicspectrum.
简介:Propagation-basedphase-contrastimagingwassimulatedbasedonparaxialFresnel-Kirchoffdiffractionintegralandsphericalwaveillumination.Underadevelopedmicro-CTsystemparameters,theeffectsoffocal-spotsizeandimaginggeometryonphase-contrastimaginghavebeeninvestigatedusinga2-mm-thicknesspolystyreneedgephantom.Anequivalentmono-energywasusedtosubstitutethepolychromaticspectrumofthemicro-focusX-raysource.Toconsidereffectsoffocal-spotsizeanddetectorresolution,theobtainedphase-contrastimagewithanidealpointsourcewasconvolvedwithsourceintensitydistributionandpointspreadfunctionofdetector.Simulationsshowreasonableinfluencesofthetwoparameterswhichareingoodagreementwithexperimentalresults.
简介:Inthisarticle,wepresentanalternativederivationforBronnikov’sreconstructionalgorithminX-rayphasecontrasttomographywithholographicmeasurements.Atwo-stepmethodwasusedinthealternativederivation.ThephaseshiftinducedbytheobjectwasobtainedbyFouriertransformandtherealpartofthecomplexrefractiveindexoftheobjectwasretrievedbyapplyingtheconventionalfilteredbackprojectionmethod.Thealternativederivationprovidesaneasierwaytounderstandthereconstructionformula.
简介:Themajortherapyforischemicstrokeisthrombolytictreatment,butsevereconsequencesoccurwhenthismethodisusedtotreathemorrhagicstroke.Currently,computedtomographyandmagneticresonanceimagingareusedtodifferentiatebetweentwotypesofstroke,butthesetwomethodsarein-effectiveforpre-hospitalcare.