Angiography, Digital SubtractionCerebral AngiographyMagnetic Resonance AngiographyIntracranial AneurysmAngiographySubtraction TechniqueIntracranial Arteriovenous MalformationsTomography, X-Ray ComputedImaging, Three-DimensionalEmbolization, TherapeuticContrast MediaCerebral ArteriesCarotid Artery, InternalSubarachnoid HemorrhageCentral Nervous System Vascular MalformationsAneurysm, RupturedCerebral VeinsCoronary AngiographySensitivity and SpecificityRadiographic Image EnhancementArterial Occlusive DiseasesCarotid StenosisCerebral InfarctionCerebrovascular CirculationCranial SinusesImage Processing, Computer-AssistedCerebrovascular DisordersAnterior Cerebral ArteryArteriovenous MalformationsConstriction, PathologicCarotid Artery DiseasesVertebral ArteryVertebrobasilar InsufficiencyTomography, Spiral ComputedVasospasm, IntracranialUltrasonography, Doppler, DuplexBasilar ArteryMiddle Cerebral ArteryUltrasonography, Doppler, ColorIopamidolCircle of WillisMagnetic Resonance ImagingCerebral RevascularizationIschemic Attack, TransientBrain IschemiaMoyamoya DiseaseCarotid-Cavernous Sinus FistulaReproducibility of ResultsIohexolSurgical InstrumentsCerebral HemorrhageArteriovenous FistulaObserver VariationUltrasonography, Doppler, TranscranialIntracranial ArteriosclerosisGadolinium DTPANeurosurgical ProceduresRetrospective StudiesCarotid ArteriesBlood Flow VelocityX-Ray Intensifying ScreensPredictive Value of TestsProspective StudiesRadiographic Image Interpretation, Computer-AssistedArtifactsEndarterectomyTreatment OutcomeInjections, Intra-ArterialIothalamate MeglumineAneurysmRadiography, InterventionalFluorescein AngiographyTibial ArteriesBrainCollateral CirculationTriiodobenzoic AcidsUltrasonographyCerebral PalsyCavernous SinusCarotid Artery, ExternalImage EnhancementRenal ArteryFollow-Up StudiesPosterior Cerebral ArteryUltrasonography, DopplerVascular PatencyTime FactorsEndarterectomy, CarotidAortographyRadiation DosageStentsPopliteal ArteryFeasibility StudiesStrokeRegional Blood FlowIntracranial Embolism and ThrombosisFalse Negative ReactionsInfarction, Middle Cerebral ArteryGadoliniumSeverity of Illness Index