Objective ToevaluateimagequalityoflowerextremityCTAoflowradiationdoseandlowcontrastmediumprotocol withsinogram-affirmediterativereconstruction(SAFIRE).Methods Thisstudyincluded116patientswhoreferredtolowerextremityCT angiographyusinga128-sliceCTscanner.Accordingtovoltageandcontrastmediumconcentration,patientsweredividedintofour groups:100kV+350mgI/mL,100kV+320mgI/mL,100kV+300mgI/mL,80kV+CarekV+300mgI/mL.Imagereconstructionunderwent conventionalfilteredback-projection (FBP)andSAFIREtechniqueineachprotocoltocompareSNR,CNRofarterialimages.Results Comparisonoftwosubgroupsinthesamegroup,SAFIREhadsignificantlyhigherimagequalitythanFBP.Comparisonamong groupsshowed:imagequalityinlowcontrastmediumandlowradiationdoseSAFIREgroupcouldreachsimilarorbetterthanthatin higherdoseFBPgroup.SAFIREcouldreduceimagenoiseandimproveimageSNRandCNR.Conclusion InlowerextremityCTA, 80kV+CarekV,300mgI/mLcontrastmediumwithSAFIREexamineprotocolcouldreducecontrastmediumconcentrationandradiationdose withnocompromiseddiagnosticdemand.

Directed evolution is a cyclic process that alternates between constructing different genes and screening functional gene variants. It has been widely used in optimization and analysis of DNA sequence, gene function and protein structure. It includes random gene libraries construction, gene expression in suitable hosts and mutant libraries screening. The key to construct gene library is the storage capacity and mutation diversity, to screen is high sensitivity and high throughput. This review discusses the latest advances in directed evolution. These new technologies greatly accelerate and simplify the traditional directional evolution process and promote the development of directed evolution.
Base Sequence ; Directed Molecular Evolution ; Gene Library ; Mutation ; Proteins/genetics*