Ultrasonography, Doppler, TranscranialUltrasonography, DopplerCerebrovascular CirculationBlood Flow VelocityEchoencephalographyCerebral ArteriesUltrasonography, Doppler, ColorUltrasonographyMiddle Cerebral ArteryIntracranial Embolism and ThrombosisIntracranial PressureValsalva ManeuverBrain Hemorrhage, TraumaticTranscranial Magnetic StimulationCerebrovascular DisordersUltrasonography, Doppler, PulsedAnemia, Sickle CellHeart Septal Defects, AtrialArterial Occlusive DiseasesIschemic Attack, TransientCerebral AngiographyIntracranial EmbolismUltrasonography, Doppler, DuplexProspective StudiesCarbon DioxideStrokePulsatile FlowBrain IschemiaBrainUltrasonography, PrenatalBlood PressureDoppler EffectSensitivity and SpecificityEvoked Potentials, MotorRegional Blood FlowCarotid StenosisCarotid Artery, InternalBasilar ArteryReproducibility of ResultsPredictive Value of TestsEmbolism, AirVascular ResistanceMonitoring, IntraoperativeCarotid Artery DiseasesUmbilical ArteriesOphthalmic ArteryAcinonyxEndarterectomy, CarotidCircle of WillisContrast MediaMotor CortexVertebral ArteryHemodynamicsSubclavian Steal SyndromeUltrasonicsCerebral Arterial DiseasesMonitoring, PhysiologicEmbolism, ParadoxicalVasospasm, IntracranialPregnancyEchocardiography, Doppler, PulsedScrotumPortal VeinPlacental CirculationAcetazolamideCollateral CirculationMagnetic Resonance ImagingConstriction, PathologicTreatment OutcomeTime FactorsHypocapniaCarotid ArteriesEchocardiography, Doppler, ColorForamen Ovale, PatentTesticular DiseasesIntracranial Arterial DiseasesReference ValuesAngiography, Digital SubtractionMagnetic Resonance AngiographySubarachnoid HemorrhageFetal DiseasesArteriesHepatic VeinsPortographyIntracranial HypertensionFunctional LateralityFollow-Up StudiesObserver VariationSpermatic CordHomeostasisRetrospective StudiesAcute DiseaseUltrasonography, InterventionalUterusHepatic ArteryEmbolismSeverity of Illness IndexRenal ArteryHyperventilationAngiography