VeinsPopliteal VeinLegUltrasonography, Doppler, DuplexSaphenous VeinPortal VeinVaricose VeinsFemoral VeinPulmonary VeinsJugular VeinsMesenteric VeinsRenal VeinsUmbilical VeinsIliac VeinHepatic VeinsSubclavian VeinSplenic VeinCerebral VeinsCranial Fossa, PosteriorRetinal VeinAzygos VeinBrachiocephalic VeinsAxillary VeinRetinal Vein OcclusionPosterior Cerebral ArteryVenous ThrombosisPosterior Cruciate LigamentPhlebographyVenous InsufficiencyMagnetic Resonance ImagingUveitis, PosteriorTreatment OutcomeVena Cava, InferiorHypothalamus, PosteriorGraft Occlusion, VascularOssification of Posterior Longitudinal LigamentTomography, X-Ray ComputedVascular PatencyTime FactorsHuman Umbilical Vein Endothelial CellsThrombophlebitisVascular Surgical ProceduresSpinal FusionPostoperative ComplicationsPituitary Gland, PosteriorFollow-Up StudiesRetrospective StudiesLens Capsule, CrystallineCatheter AblationEndothelium, VascularPosterior Leukoencephalopathy SyndromeCadaverUltrasonography, Doppler, ColorVascular GraftingConstriction, PathologicBody PatterningInfratentorial NeoplasmsVenous PressurePosterior Capsule of the LensAnastomosis, SurgicalParietal LobeVenae CavaeBrain MappingProspective Studies