Ultrasound Artifacts Flashcards
What is the speed of sound in soft tissue? *
1540m/sec
What is the speed of sound in the breast? *
1450 m/sec
Why is the speed of sound slower in breast than soft tissue? *
Due to high fat content
Because breast speed is slower than soft tissue speed what is a common finding with lesions? *
Often lesions are deeper than they actually appear within the breast
Refraction
Occurs when the beam strikes tissue with a different density than that through which is has been travelling
What is assumed with refraction?
Assume the beams is travelling in a straight line
What angle does refraction occur at?
Occurs at an angle of incidence other than 90 deg
Partial volume effect or volume averaging
Fill-in of cystic structures because echoes are detected outside of the central beam axis
Mirror image artifact
Reverberation artifact secondary to the impedance mismatch between the transducer face material and the patient’s skin as well as that which occurs between two strong specular reflectors
Where does acoustic enhancement occur?
Deep to fluid filled structures
Where does shadowing occur?
Deep to cary dense objects
What are 5 normal anatomical structures that can cause artifact?
- Excessive equipment gain settings or inappropriate TGC settings
- may cause artifactual echoes in cystic structures - Improper transducer selection
- low frequency transducers exhibit poor axial and lateral resolution - Cooper’s ligaments may cause shadowing which is suspicious for malignancy
- A protruding nipple makes scanning of the retroareolar region difficult to assess and may result in artifactual images
- Breast implants may displace and compress normal structures, making them appear normal
Is the speed of sound fast or slower in silicon compared to soft tissue? What is it?
- Slower
- 1000m/sec
What does the Bayonet sign occur?
Because of the difference in the speed of sound between breast tissue and the fluid within the cyst, causing an aspiration needle to appear “broken”
What does the Bayonet sign helpful with?
It can tell us that the needle is indeed in the cyst
What kinda of artifact is edge shadowing an example of?
Refraction
What problem can Cooper’s ligaments cause? How do you fix it?
- May attenuate the sound beam if strike perfectly creating a shadow
- Turn on the shadow caused from this ligament to prove it’s not a mass
