just study

• What are the 6 assumptions of imaging systems ?

  Sound travels in a straight line; sound travels directly to a reflector and back; sound travels in soft tissue at exactly 1,540 m/s; reflections arise only from structures positioned in the beam's main axis; the imaging plane is very thin; the strength of a reflection is related to the characteristics of the tissue creating the reflection
• How can you differentiate artifacts and actual anatomy ?

  Artifacts appear in some views and disappear in others while actual anatomy always remains visible
• What are some characteristics of reverberation artifact ?

  appears in multiples, equally spaced, located parallel to the sound beam's main axis, and located at ever-increasing depths
• What assumption does reverberation artifact invalidate ?

  assumption 2: Sound travels directly to a reflector and back
• What are characteristics of comet tail artifact ?

  appears as a single long hyperechoic echo, located parallel to the sound beam's main axis
• What assumption does comet tail artifact invalidate ?

  assumption 2: sound travels directly to a reflector and back
• What are some characteristics of a shadow artifact ?

  hypo- or anechoic, results from too much attenuation, located beneath the structure with abnormally high attenuation, prevents visualization of true anatomy scan
• Shadowing is entirely unrelated to the speed of sound in a medium.
• What assumption does shadow artifact invalidate ?

  assumption 6: the strength of a reflection is related to the characteristics of the tissue creating the reflection
• What are some characteristics of edge shadow ?

  hypo- or anechoic, results when the beam spreads after striking a curved reflector, extends downward from the curved reflectors edge (parallel to beam), and prevents visualization of true anatomy on the scan
• An edge shadow is also called:

  shadowing by refraction
• What assumption does edge shadow invalidate ?

  assumption 6
• What are some characteristics of enhancement ?

  Hyperechoic, result of too little attenuation, located beneath a structure with abnormally low attenuation
• What assumption does enhancement invalidate ?

  assumption 6
• True or false: In enhancement, the number of reflectors is correct.

  True
• Enhancement artifact can be clinically useful
• Enhancement artifact is unrelated to the speed of sound in a medium
• What are some characteristics of focal enhancement ?

  hyperechoic side-to-side region, results from increased intensity at the focus
• What assumption does focal enhancement invalidate ?

  assumption 6
• What are some characteristics of mirror image artifact ?

  a second copy of a true reflector; artifact is DEEPER than the true reflector, a bright reflector (the mirror) lies on a straight line between the artifact and the transducer, and the true reflector and artifact are equal distances from the mirror