wk 2. Sonographic Artifacts in MSK Flashcards
appears when highly reflective structures such as tendons appear hypoechoic rather than hyperechoic because the incidence sound beam is > or < 90 degrees.
anisotrophy
anisotrophy occurs when the incident angle is NOT __ degrees
90
___ artifact occurs when the beam is reflected, absorbed or refracted
posterior acoustic shadowing
__ shadow occurs on small radius curvature or rough surface
clean
__ shadow occurs on large radius of curvature or smooth surfaces
dirty
also called “critical angle shadowing” or “edge shadowing”
refractile shadowing
refractile shadowing occurs at ___
edge of highly curved surfaces
change in direction of sound beam results in hypoechoic band posterior to structure
refractile shadowing
Occurs deep to fluid filled structures
posterior acoustic enhancement
“ring down artifact” or “comet tail artifact” is also called
posterior reverberation
Series of reflect echoes is more continuous deep to structure
ring down
short segment of posterior bright echoes, narrows further from the source of artifact
comet tail artifact
seen with soft tissue gas
comet tail artifact
seen with metal surfaces
ring down
occurs when returning sound wave has been passed between two tissues with different speeds
time of flight (speed of sound) artifact
time of flight artifact results from assumption that speed of sound is ___
constant (1540m/s)
if the speed of sound is less than average in tissue, the artifact appears ___in relation to transducer
farther away
faster speeds in tissue result in artifact being ___ in relation to transducer
closer to
creation of this type of image false info occurs most commonly when imaging obese pts at muscle-fat interface
time of flight
a strong reflector located outside the main US beam may generate echoes that are detectable by the transducer
beam-width artifact
how to fix beam width artifact
adjust focal zone to level of the object of interest
how to fix anisotrophy artifact
heel-toe rocking probe to create perpendicular angle of incidence on muscle
how to fix reverberation artifact
use stand off pad or change angle of incidence
how to fix refractile artifact
compound imaging or harmonics
how to fix the time of flight artifact
change angle of incidence
beams produced at different angles and combined to form a single US image
spatial compound imaging
Disadvantage of spatial compound imaging
smoothing effect may reduce the artifact produced by a foreign body
Evaluation of deep structures and improved joint/ tendon surface visibility. Delineates the edge of a soft tissue mass, fluid filled tendon tear
harmonic imaging
combining image info obtained during real-time scanning to form one “composite” image
extended FOV
allows imaging an entire structure no matter the length
extended FOV (panoramic)
examples of uses for US guidance (4)
- steroid injection
- barbottage
- lavage and aspiration
- biopsy
treatment for calcific tendonitis that breaks up the calcium deposits so they can be absorbed by the body
barbottage
