Unit 7

• what is hyperechoic 


  brighter
• what is hypoechoic 


  darker
• what is anechoic 


  completely black
• what is isoechoic

  same echogenisity
• what is homogenous 


  smooth, same texture
• what is heterogenous


  different texture
• what is an artifact 


  occurs when a structure is not real, missing, misplaced, incorrect brightness, shape, or size
• what are the propagation artifacts 


  slice thickness

  speckle

  reverberation

  comet tail

  ring down

  mirror image

  refraction

  edge shadow

  grating lobe

  speed error

  rand ambiguity
• what are the attenuation artifacts 


  shadowing

  enhancement
• what are the spectral doppler artifacts 


  aliasing

  range ambiguity

  mirror image

  flash
• what is slice thickness 


  third dimension

  beam with perp to the scan plane

  can fix by using tissue harmonic imaging
• what is speckle 


  granular appearance of images

  can fix by compound imaging
• what is reverberation 


  equally spaced reflections of diminishing amplitude

  2 or more strong reflectors are encountered in the sound path
• what is comet tail 


  similar to reverberation but lines are very close together
• what is ring down 


  often caused by fluid trapped between gas bubbles
• what is another name for ring down


  dirty shadowing
• what is mirror image

  duplication of a structure on the opposite side of a strong reflector

  can fix by trying a different angle or increasing gain
• what is mirror image common around

  pleura and diaphragm
• what is refraction 


  change of direction of the sound beam

  displaces structures laterally from their correct locations
• what are grating lobes 


  additional weaker beams emitted from an array transducer

  displaces laterally from true structures
• what is speed error 


  occurs when the speed of sound in soft tissue is faster or slower that 1.54
• what is range ambiguity

  all echoes are not received before the next pulse is emitted

  places the structures closer to the surface than they should be

  can fix if we increase depth PRF which should adjust it
• what is shadowing 


  weakening of echoes distal to a strongly attenuating or reflecting structure

  can fix with spatial compounding
• what is enhancement 


  strengthening of echoes distal to a weakly attenuating structure

  can fix with spatial compounding
• what is aliasing

  under sampling of the doppler shifts in a pulsed doppler system

  appearance of doppler info on wrong side of baseline

  occurs when doppler shift exceeds the Nyquist limit

  can fix by increasing spectral scale or baseline
• what is range ambiguity (color/spectral)


  pulse is emitted before all the echoes from the previous pulse have been received

  increase PRP
• what is mirror (color/spectral)


  duplication of vessel or doppler shift on opposite side of strong reflector

  happens closer to 90 degrees

  can fix by decreasing doppler gain and changing the angle
• what is flash artifact 


  sudden burst of color doppler

  usually caused by tissue or transducer motion

  color beyond the region of blood flow