Physics

Category Physics Term Frequency Definition of Frequency Number of Sound Wave Cycles Per Second Measured in Megahertz; Higher Frequency Gives Better Resolution but Less Depth Notes About Frequency Choose Probe Frequency by Depth of Target

Category Physics Term Radionuclide Definition of Radionuclide Unstable Isotope That Emits Ionizing Radiation During Decay Notes About Radionuclide Common Examples Include Tc-99m, I-131, And F-18

Category Physics Term Velocity Of Sound In Tissue Definition of Velocity Of Sound In Tissue Speed At Which Ultrasound Travels Through Tissue (~1540 M/S Average) Notes About Velocity Of Sound In Tissue Used To Convert Time To Depth

Category Physics Term Beam Attenuation Definition of Beam Attenuation Reduction in Beam Intensity With Depth Due to Absorption and Scattering Notes About Beam Attenuation Affects Penetration and Image Brightness

Category Physics Term Far Field (Fraunhofer Zone) Definition of Far Field (Fraunhofer Zone) Region Beyond The Focal Zone Where Beam Diverges Notes About Far Field (Fraunhofer Zone) Lower Lateral Resolution Compared With Focal Zone

Category Physics Term Backscatter Definition of Backscatter Scattering Of Ultrasound Energy Back Toward The Transducer From Tissue Microstructure Notes About Backscatter Basis For Image Texture And Speckle

Category Physics Term Near Field (Fresnel Zone) Definition of Near Field (Fresnel Zone) Region Close To The Transducer Where Beam Is Not Fully Formed Notes About Near Field (Fresnel Zone) Image Quality Varies With Probe Design

Category Physics Term Main Magnetic Field (B0) Definition of Main Magnetic Field (B0) Static Uniform Magnetic Field That Aligns Nuclear Spins Notes About Main Magnetic Field (B0) Measured In Tesla; Typical Clinical Systems 0.5–3.0 T

Category Physics Term Attenuation Definition of Attenuation Loss of Ultrasound Energy as It Travels Through Tissue Due to Absorption and Scattering Notes About Attenuation Higher With Bone and Air

Category Physics Term Acoustic Impedance Definition of Acoustic Impedance Resistance Of Tissue To Ultrasound Wave Propagation Determined By Density And Sound Speed Notes About Acoustic Impedance Mismatch Between Tissues Produces Reflections