Tunica IntimaBasilar ArteryVertebrobasilar InsufficiencyPosterior Cerebral ArteryVertebral ArteryInfarction, Posterior Cerebral ArteryCerebral AngiographyIntracranial AneurysmArteriesBrain Stem InfarctionsCerebral ArteriesSubarachnoid HemorrhageMagnetic Resonance AngiographyCerebrovascular CirculationBrain InfarctionAneurysm, RupturedCerebral InfarctionIntracranial ArteriosclerosisEmbolization, TherapeuticMoyamoya DiseaseVertebral Artery DissectionTunica MediaStrokeCarotid Artery, InternalPenile IndurationAnterior Cerebral ArteryTomography, X-Ray ComputedCarotid ArteriesBrain IschemiaPulmonary ArteryMagnetic Resonance ImagingUltrasonography, Doppler, TranscranialIschemic Attack, TransientIntracranial EmbolismTreatment OutcomeArterial Occlusive DiseasesMuscle, Smooth, VascularAngiography, Digital SubtractionAngiographyTesticular HydrocelePenisFemoral ArteryCerebrovascular DisordersAneurysm, DissectingConstriction, PathologicCerebral RevascularizationRetrospective StudiesVasospasm, IntracranialRenal ArteryMesenteric ArteriesUrologic Surgical Procedures, MaleVasodilationBlood CirculationFollow-Up StudiesVasoconstrictionAcute DiseaseCranial Fossa, PosteriorCoronary VesselsDogsStentsIliac ArteryBrainElastic TissueCerebellumRabbitsProspective StudiesRisk FactorsCarotid Artery, CommonCarotid Artery DiseasesArteriosclerosisCoronary Artery BypassRegistriesEndothelium, VascularVasodilator AgentsMammary ArteriesRadial ArteryAortaRecurrencePredictive Value of TestsTime FactorsMiddle Cerebral ArterySerotoninSubclavian ArteryCircle of WillisPulmonary CirculationDiffusion Magnetic Resonance ImagingBrachial ArteryExtracorporeal CirculationVasoconstrictor AgentsPenile ImplantationImpotence, VasculogenicSplenic ArteryCollateral CirculationRegional Blood FlowCarotid Artery InjuriesPapaverineRats, Sprague-DawleyPenile ProsthesisMuscle ContractionPotassium Chloride