MSK Artifacts

Question 1

what are three assumptions in which ultrasound functions with?

Answer 1

• Speed of sound is 1540m/s
• Area is being imaged with a straight beam
• Sounds travels out and back in a straight line

Question 2

why are artifacts an issue in MSK imaging?

Answer 2

superficial nature of MSK structures and high reflectively of bone

Question 3

what is anisotropy artifact

Answer 3

• 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

Question 4

what do the angle and direction of the reflected beam depend on?

Answer 4

depend on the angle of incidence

Question 5

what is an example of anisotropy

Answer 5

Loss of definition of the curved pole of the right kidney

Question 6

what structure produces the most pronounced anisotropy

Answer 6

Tendons

Question 7

Anisotropy correction

Answer 7

Heel-to-toe rocking of the transducer creates a perpendicular angle of incidence, removing the anisotropy

Question 8

Reverberation may be ______or ________

Answer 8

• May be beneficial or detrimental

Question 9

what occurs in reverberation

Answer 9

• Multiple delayed reflections from a strong tissue boundary result in decreased linear artifact superimposed over primary signal

Question 10

what is comet tail artifact

Answer 10

function of sound bouncing between two closely placed reflectors within the imaged structure

Question 11

Correction of reverberation

Answer 11

o Anterior reverberation can be minimized with the use of a stand-off pad or by changing the angle of incidence

Question 12

what is Refractile shadowing

Answer 12

• Bending of transmitted sound beam to an oblique path

Question 13

what does refractile shadowing create

Answer 13

• Hypoechoic band posterior to the structure

Question 14

what is the cause of refractile shadowing?

Answer 14

• Can be caused by acoustic impedance mismatch

Question 15

where can refractile shadowing be seen?

Answer 15

o Seen at the edge of a round or oval ligament or as the result of a traumatic tear of a musculoskeletal system

Question 16

Where is refractile shadowing most commonly seen?

Answer 16

o Most commonly seen in complete tendon tear

Question 17

Refractile shadowing correction

Answer 17

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

Question 18

what is Time of flight artifact

Answer 18

• Speed of sound artifacts occurs when returning sound wave has passed between two tissues with different speeds

Question 19

when speed is less then 1540m/s

Answer 19

object appears farther away from the transducers

Question 20

when speed is more then 1540m/s

Answer 20

, object appears closer to the transducer

Question 21

what plane does time of flight displace

Answer 21

Axial

Question 22

What occurs when time of flight artifact is coupled with refraction

Answer 22

creates an incorrect shape

Question 23

Time of Flight correction

Answer 23

May not be able to eliminate as a result of tissue artifact sound properties. Change the angle of incidence to demonstrate surrounding tissue