Diagnostic US Flashcards
What is reverse piezoelectric effect?
waves return to transducer
varying electrical potentials
assigned a gray scale
convert to an image
signal/noise:
low =?
high=?
low=worse picture/something absorbs or obstructs the signal
high= better picture
what is refraction?
occurs when waves bend as they pass through different materials. depends on speed of wave and impedence of the materials
what is reflection?
some of the propogating sound strikes a boundary between 2 media and returns to the transducer
what is scatter?
reflection and refraction of waves away from the transducer
what is absorption?
ultrasound waves are turned into heat
what is attenuation?
as sound waves travel through tissue, they decrease in intensity, power and amplitude
harmonics
higher frequencies attenuate more
when to use high freq transducer?
lower freq?
high= better resolution, less penetration low= less resolution, deeper structures
diff between linear and curvilinear transducers?
column of sound waves vs fan of soundwaves
what is focus?
beam narrows and widens
narrow region can be adjusted and has the best resolution
multiple focuses will decrease the temporal resolution
what is gain?
increases/ decreases overall brightness
time gain compensation
changes gain at one segment of screen
what are harmonics?
help eliminate artifact in deep tissue
what is compounding?
simultaneous images from multiple angles
what are the following?
power doppler
color doppler
spectral
- sensitive for motion
- detects direction of motion
- pulsed wave and continuous wave
