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1、ieeetransactionsonultrasonics,ferroelectrics,andfrequencycontrol,vol.55,no.8,august20081755FastParametricBeamformerforSyntheticApertureImagingSvetoslavIvanovNikolov,JørgenArendtJensen,SeniorMember,IEEE,andBorislavGueorguievTomovAbstract—Thispaperdescribesthede
2、signandimple-imaging[8]–[13]promptedbytheadvancesindigitaltech-mentationofareal-timedelay-and-sumsyntheticaperturenology.Duringthisperiod,severaltechniquestoincreasebeamformer.Thebeamformingdelaysandapodizationco-thesignal-to-noiseratiohavebeenintroduced,sucha
3、stheefficientsaredescribedparametrically.Theimageisvieweduseofmultipleelementsintransmit[9],[10],[14]–[20],andasasetofindependentlinesthataredefinedin3-Dbytheirorigin,direction,andinter-sampledistance.Thedelaycal-newwaysofcalculatingthepropagationpathhavebeencula
4、tionisrecursiveandinspiredbythecoordinaterotationdefined[21].Theuseofcodedexcitationshasfurtherin-digitalcomputer(CORDIC)algorithm.Only3parameterscreasedthesignal-to-noiseratio,imagecontrast,andpen-perchannelandlineareneededfortheirgeneration.Theetrationdepth[2
5、2]–[26].TherealappealofusingSAmeth-calculationofapodizationcoefficientsisbasedonapiece-odsformedicalultrasoundistheuseofsynthetictransmitwiselinearapproximation.Theimplementationofthebeamformerisoptimizedwithaperture(STA)focusing,wherealltransducerelementsareres
6、pecttothearchitectureofanovelsyntheticapertureusedtoreceiveateverytransmission[19],[27]–[29].Thereal-timeultrasoundscanner(SARUS),inwhich4chan-combinationofalltheseapproacheshasmadeitpossiblenelsareprocessedbythesamesetoffield-programmabletogeneratenotonlyimage
7、sathighframerates,butalsogatearrays(FPGA).Insynthetictransmitapertureimag-imagesthathavesuperiorcontrastandresolution[30],[31].ing,low-resolutionimagesareformedaftereveryemission.Summingalllow-resolutionimagesproducesaperfectlyfo-Inthelastdecade,effectsofmotion
8、inSAimagingcusedhigh-resolutionimage.Thedesignofthebeamformerhavebeenstudied[32],andnewmethodsforestimatingismodular,andasinglebeamformationunitcanproducethebloodvelocityweredevelo
