Blood Flow VelocityCerebrovascular CirculationUltrasonography, Doppler, TranscranialMiddle Cerebral ArteryCerebral ArteriesRegional Blood FlowHypocapniaEchoencephalographyAnterior Cerebral ArteryHyperventilationCarbon DioxideBrainBlood PressureIntracranial PressureXenon RadioisotopesHomeostasisVascular ResistanceTilt-Table TestHemodynamicsEthamsylateHypercapniaLaser-Doppler FlowmetryHypotension, OrthostaticBlood Circulation TimeOxygenUltrasonography, DopplerModels, CardiovascularHeart RateXenonBrain IschemiaAcetazolamideTomography, Emission-ComputedBlood VolumePulsatile FlowPostureOphthalmic ArteryVasomotor SystemCerebral InfarctionInfant, PrematurePhotoplethysmographyTechnetium Tc 99m ExametazimeUltrasonography, Doppler, ColorOxygen RadioisotopesNitrous OxideTomography, Emission-Computed, Single-PhotonInfant, NewbornIofetamineUltrasonography, Doppler, PulsedOximesCoronary CirculationInfant, Premature, DiseasesMagnetic Resonance ImagingCerebrovascular DisordersTidal VolumeAntipyrineAnoxiaCardiac OutputMicrocirculationPartial PressureOxygen ConsumptionReference ValuesRheologyCiliary ArteriesAnalysis of VarianceTime FactorsRetinal ArteryHyperemiaSubarachnoid HemorrhageEchocardiography, DopplerCerebral AngiographyCerebral VeinsOrganotechnetium CompoundsArteriesSnoringIschemic Attack, TransientUmbilical ArteriesPia MaterInfarction, Middle Cerebral ArteryIntelligence TestsCarotid Artery, InternalPapioMagnetic Resonance AngiographyUltrasonographyBlood Gas AnalysisPosterior Cerebral ArteryBlood ViscosityCircle of WillisDogsAmphetaminesVasodilationArterial Occlusive DiseasesSpectroscopy, Near-InfraredInfant, Low Birth WeightHypotensionVasodilator AgentsUltrasonography, PrenatalDiastoleImage Processing, Computer-AssistedCerebral HemorrhageMicrospheres