Vertebral ArteryVertebrobasilar InsufficiencyBasilar ArteryVertebral Artery DissectionSubarachnoid Hemorrhage, TraumaticCerebral AngiographyStrokeMagnetic Resonance AngiographyIntracranial AneurysmArteriesAneurysm, DissectingAngioplasty, BalloonSubclavian ArteryStentsSubclavian Steal SyndromeCarotid ArteriesCerebral ArteriesPulmonary ArteryCarotid Artery, InternalAngiography, Digital SubtractionAngiographyArterial Occlusive DiseasesTomography, X-Ray ComputedCerebrovascular DisordersRenal ArteryFemoral ArteryBrain IschemiaMesenteric ArteriesVertigoCarotid Artery DiseasesSubarachnoid HemorrhageCerebral InfarctionIschemic Attack, TransientIntracranial ArteriosclerosisEmbolization, TherapeuticLateral Medullary SyndromeTreatment OutcomeAneurysm, RupturedMammary ArteriesCoronary Artery BypassConstriction, PathologicIliac ArteryCarotid Artery, CommonCerebrovascular CirculationIntracranial Embolism and ThrombosisOccipital BoneRadial ArteryCerebellar DiseasesMagnetic Resonance ImagingUltrasonography, Doppler, TranscranialFollow-Up StudiesCarotid Artery, Internal, DissectionBrain Stem InfarctionsCervical VertebraeCarotid StenosisCerebral RevascularizationEchoencephalographyHemifacial SpasmCervical AtlasInfarction, Posterior Cerebral ArteryNeck InjuriesRetrospective StudiesBrachial ArterySplenic ArteryBrain InfarctionFibromuscular DysplasiaCarotid Artery, ExternalPosterior Cerebral ArteryTime FactorsHepatic ArteryAngioplastyCircle of WillisProspective StudiesAxisBrachiocephalic TrunkRisk FactorsCoronary VesselsMiddle Cerebral ArteryHeadacheCeliac ArteryAneurysm, FalseCerebellumNerve Compression SyndromesOphthalmic ArteryBlood Flow VelocityAneurysmMesenteric Artery, SuperiorPetrous BoneUltrasonographyRecurrenceTrigeminal NeuralgiaUmbilical ArteriesCerebral HemorrhageRenal Artery ObstructionInfarction, Middle Cerebral ArteryThoracic ArteriesUltrasonography, Doppler, ColorUltrasonography, DopplerTemporal ArteriesRegional Blood Flow