Biomedical imaging Ultrasound L1

 What is the formula for the speed of a wave c?  where K is bulk modulus of compressibility (N/m2) and rho is density as ever What is acoustic impedance? What two properties does it link together? An inherent property of a medium Relates pressure to particle velocity What is formula for energy density and what are its units? J/m3 What is formula for ultrasound intensity and what are its units?  watts/m2 Give the reflection formula of a wave at a plane surface between two materials of different impedance values Give the transmission formula of a wave at a plane surface between two materials of different impedance values Derive the solutions for reflection at a plane surface What happens when you get multiple layers of material in the path of an ultrasound wave as shown here? You end up with a standing wave How can you ensure a complete transmission when you have three layers like this By picking a matching layer of a quarter wavelength What causes absorption in ultrasound? Viscous loss, thermal conduction, structural vibration resonances What causes attenuation when it comes to ultrasound Absorption and scattering What is the formula for attenuation coefficient in ultrasound? for most tissues, m ~ 1so most important parameter is 'a' with units dB/cm/MHz m=4 for small scatterers and this is rayleigh scattering. What are the properties of the backing layer and how thick should it be? Thick to avoid reflections from back surface (>5mm)Lossy to stop ultrasound reaching back surface Impedance of backing layerIf too high all backwards sound is coupled into the backing layer (transmission increases)IN practice make Z around 5 How do you determine the thickness of the PZT element t = λpzt/2  λpzt = cpzt/f speed of sound in pzt is (4000m/s) What is the speed of sound in nylon and pzt? 2500m/s and 4000m/s Authorkeesukim ID339564 Card SetBiomedical imaging Ultrasound L1 Descriptionultrasound intro Updated2018-05-12T12:08:36Z Show Answers