MSK Artifacts Flashcards
what are three assumptions in which ultrasound functions with?
- Speed of sound is 1540m/s
- Area is being imaged with a straight beam
- Sounds travels out and back in a straight line
why are artifacts an issue in MSK imaging?
superficial nature of MSK structures and high reflectively of bone
what is anisotropy artifact
• Occur when the sound beam misses the transducer on the return because if the curve of the structure on the return because of the curve of the structure
what do the angle and direction of the reflected beam depend on?
depend on the angle of incidence
what is an example of anisotropy
Loss of definition of the curved pole of the right kidney
what structure produces the most pronounced anisotropy
Tendons
Anisotropy correction
Heel-to-toe rocking of the transducer creates a perpendicular angle of incidence, removing the anisotropy
Reverberation may be ______or ________
• May be beneficial or detrimental
what occurs in reverberation
• Multiple delayed reflections from a strong tissue boundary result in decreased linear artifact superimposed over primary signal
what is comet tail artifact
function of sound bouncing between two closely placed reflectors within the imaged structure
Correction of reverberation
o Anterior reverberation can be minimized with the use of a stand-off pad or by changing the angle of incidence
what is Refractile shadowing
• Bending of transmitted sound beam to an oblique path
what does refractile shadowing create
• Hypoechoic band posterior to the structure
what is the cause of refractile shadowing?
• Can be caused by acoustic impedance mismatch
where can refractile shadowing be seen?
o Seen at the edge of a round or oval ligament or as the result of a traumatic tear of a musculoskeletal system
Where is refractile shadowing most commonly seen?
o Most commonly seen in complete tendon tear
Refractile shadowing correction
o Use of new technologies, such as compound imaging or harmonics, helps reduce artifact. Changing the angle of incidence may move the artifact out of the region of interest
what is Time of flight artifact
• Speed of sound artifacts occurs when returning sound wave has passed between two tissues with different speeds
when speed is less then 1540m/s
object appears farther away from the transducers
when speed is more then 1540m/s
, object appears closer to the transducer
what plane does time of flight displace
Axial
What occurs when time of flight artifact is coupled with refraction
creates an incorrect shape
Time of Flight correction
May not be able to eliminate as a result of tissue artifact sound properties. Change the angle of incidence to demonstrate surrounding tissue
