Chapter 21 Pt 1 Flashcards
(39 cards)
Artifacts are reflections that are described as what 5 things?
Not real Not seen on the image Incorrect shape or size Incorrect position Incorrect brightness
An ______ is essentially an error in imaging
Artifact
What 4 things do artifacts result from?
- Violation of assumptions
- Equipment malfunction or poor design
- the physics of ultrasound
- operator error
Portions of an image that are brighter than surrounding tissues, or tissues that appear brighter than normal
Hyperechoic
Portions of an image that are not as bright as surrounding tissues, or tissues that appear less bright than normal
Hypoechoic
An extreme form go hypoechoic, meaning entirely without echoes
Anechoic
Describes structures with equal echo brightness
Isoechoic
A portion of the tissue or an image that has similar echo characteristics throughout
Homogeneous
A portion of the tissue or an image that has differing echo characteristics throughout
Heterogeneous
The six 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 1,540m/s
- reflections arise only from structures positioned in the beams main axis
- the imaging plane is very thin
- the strength of a reflection is related to the characteristics of the tissue creating the reflection
_____ malfunction should be considered when obvious artifacts remain visible even after corrective measures have been takes
Instrument
______ appears on the display as multiple, equally spaced echoes caused by the bouncing of the sound wave between two strong reflectors positioned parallel to the ultrasound beam
Reverberations
- appear in multiples
- appear equally spaced
- are located parallel to the sound beams main axis
- are located at ever-increasing depths
Reverberation characteristics, reverberations resemble a ladder or Venetian blind
The first or second reflections (in reverberation), ______ to the transducer are real, but the remainder are not
Closest
Comet tail artifact often described as “reverberation with the spaces squeezed out” appears as a ______ line directed downward! it is also known as ring down artifact
Solid hyperechoic
______ artifacts is created when closely spaced reverberations merge. It is more likely to appear when reflecting surfaces are located in a medium with a very high propagation speed, such as a mechanical heart valve
Comet tail
Comet tail can also arise from the resonance, or vibration, of small structures such as gas bubbles after they have been bombarded by a ______
Sound Pulse
______ appears as a hypoechoic or anechoic region extending downward from a highly attenuating structure, they are the same color as the image background
Shadowing
Shadows appear when the attenuation is ______ in the tissue above the shadow than in the surrounding tissue
Higher
- hypo-or anechoic
- the result of too much attenuation
- located beneath the structure with abnormally high attenuation
- prevents visualization of true anatomy on the scan
Characteristics of shadowing, it is unrelated to speed of sound in a medium
An ______ artifact is a special from of shadowing that appears as a hypoechoic region extending down from the edge of a curved reflector; it prevents the display of true anatomic structure that are positioned within the extended hypoechoic region
Edge shadowing
With edge shadowing the sound beam ______ (transmits with a bend) at the edge of a curved reflector, the beam simultaneously diverges, resulting in a drop in intensity
Refracts
What’s is another name for edge shadowing?
Shadowing by refraction
- hypo or anechoic
- results when the beam spreads after striking a curved reflector
- extends downward from the curved reflectors edge, parallel to the beam
- prevents visualization of true anatomy on the scan
Characteristics of edge shadowing
