Gastric EmptyingStomachGastric AcidGastrinsGastric JuiceVagus NervePepsin AGastroparesisGastrointestinal MotilityGastric MucosaDyspepsiaPentagastrinDuodenumEcho-Planar ImagingHydrogen-Ion ConcentrationEcholocationImage EnhancementMagnetic Resonance ImagingChiropteraPhantoms, ImagingImage Interpretation, Computer-AssistedArtifactsReproducibility of ResultsContrast MediaUltrasonographyEchocardiographySensitivity and SpecificityImaging, Three-DimensionalEchocardiography, TransesophagealDoppler EffectAlgorithmsUltrasonicsMagnetic Resonance SpectroscopySignal-To-Noise RatioEchovirus 9Echovirus InfectionsTransducersGadolinium DTPAMagnetic Resonance Imaging, CineSignal Processing, Computer-AssistedSpectrophotometry, InfraredSpin LabelsObserver VariationMitral Valve StenosisRadio WavesBrainAuditory PerceptionFourier AnalysisSoundFeasibility StudiesAtrial Function, LeftEchocardiography, Stress