PhotonsBone DensityTomography, Emission-Computed, Single-PhotonPopulation DensityCentrifugation, Density GradientElementary ParticlesScattering, RadiationLightPhantoms, ImagingMonte Carlo MethodRadiometryScintillation CountingMicroscopy, Fluorescence, MultiphotonOrganotechnetium CompoundsRadiation DosageParticle AcceleratorsRadiopharmaceuticalsAbsorptiometry, PhotonLipoproteins, LDLTime FactorsTechnetium Tc 99m ExametazimeThallium RadioisotopesTomography, Emission-ComputedTechnetiumImage Processing, Computer-AssistedEquipment Failure AnalysisEquipment DesignElectronsOximesRadiotherapy Planning, Computer-AssistedComputer SimulationQuantum TheoryTelluriumLipoproteins, HDLRelative Biological EffectivenessPhotometryCell CountRadiotherapy, High-EnergyRadiotherapy DosageRadiusTomography, OpticalSemiconductorsOptical ProcessesOptics and PhotonicsIodine RadioisotopesTomography, X-Ray ComputedLasersKineticsProton TherapyOsteoporosisAlgorithmsSensitivity and SpecificityReproducibility of ResultsModels, BiologicalRadioisotopesBrainLipoproteins, VLDLDose-Response Relationship, RadiationGamma CamerasX-RaysBone and BonesDensitometryLuminescent MeasurementsSynchrotronsPositron-Emission TomographySpectrum AnalysisModels, TheoreticalDiagnostic ImagingRetinal Rod Photoreceptor CellsSpectrometry, GammaIofetamineRadiationCadmium CompoundsRhodopsinLutetiumPost-Synaptic DensityLuminescenceReceptors, LDLRadionuclide ImagingPhotoreceptor CellsNeutronsFluorescencePhotosynthesisMicroscopy, ElectronHeavy Ion RadiotherapyCholesterolThalliumXenon RadioisotopesLinear Energy TransferVision, OcularLipoproteinsMammographyTechnetium Tc 99m SestamibiMineralsCerebrovascular CirculationApolipoproteinsRadiotherapy, Intensity-ModulatedSpectrometry, FluorescenceTomographyIodobenzenes