Cerebrovascular CirculationBlood Flow VelocityUltrasonography, Doppler, TranscranialXenon RadioisotopesRegional Blood FlowMiddle Cerebral ArteryCerebral ArteriesBrainTomography, Emission-ComputedTechnetium Tc 99m ExametazimeIofetamineTomography, Emission-Computed, Single-PhotonXenonHypocapniaOximesCarbon DioxideOxygen RadioisotopesEchoencephalographyHyperventilationIntracranial PressureAcetazolamideBlood PressureOrganotechnetium CompoundsAnterior Cerebral ArteryAmphetaminesBlood VolumeBrain IschemiaCerebral InfarctionVascular ResistanceHomeostasisAntipyrineCerebrovascular DisordersHypercapniaHemodynamicsBlood Circulation TimeLaser-Doppler FlowmetryOxygenMagnetic Resonance ImagingTilt-Table TestEthamsylateKryptonReference ValuesNitrous OxideIschemic Attack, TransientCerebral CortexModels, CardiovascularHeart RateHypotension, OrthostaticImage Processing, Computer-AssistedAutoradiographyUltrasonography, DopplerVasomotor SystemPartial PressureDominance, CerebralRadiopharmaceuticalsBrain MappingSubarachnoid HemorrhageOxygen ConsumptionPulsatile FlowPositron-Emission TomographyPostureOphthalmic ArteryFrontal LobeInfant, PrematurePhotoplethysmographyTime FactorsPapioCarotid Artery, InternalElectroencephalographyMicrospheresArterial Occlusive DiseasesUltrasonography, Doppler, ColorTomography, X-Ray ComputedAnalysis of VarianceBrain EdemaInfant, NewbornRestHyperemiaFunctional LateralityMicrocirculationBlood Gas AnalysisInfarction, Middle Cerebral ArteryCerebral AngiographyPia MaterSpin LabelsRadioisotopesUltrasonography, Doppler, PulsedCerebral Arterial DiseasesCarbon RadioisotopesHemodilutionHypoxia, BrainCoronary CirculationInfant, Premature, DiseasesReperfusionHypotensionAnoxiaOccipital LobeBlood-Brain BarrierTidal VolumeArteries