Chapter 21 Pt 1 Flashcards
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
_____ artifact appears as a hyperechoic region beneath tissues with abnormally low attenuation
Enhancement
- it is unrelated to the speed at which sound travels in a medium
- hyperechoic
- the result of too little attenuation
- located beneath a structure with abnormal low attenuation
Characteristics of enhancement
______ is a special form of enhancement in which a side-to-side region of an image appears brighter than tissues at other depths
Focal enhancement
What is an other name for focal enhancement?
Focal bending- resembles incorrect TGC settings
Structures at the ______ appear brighter than those at other depths in focal enhancement
Focus
- a hyperechoic side-to-side region
- results from increased intensity at the focus
Characteristics of focal enhancement
______ artifact is created when sound reflects off a strong reflector, and is redirected toward a second structure. The redirection causes a replica of the structure to incorrectly appear on the image
Mirror artifact
The mirror artifact is located ______ than the real structure, the mirror is always located along a straight line between the transducer and the artifact
Deeper
-a second copy of a true reflector
-the artifact appears deeper than the true reflector a bright reflector, the mirror, lies on a straight line between the artifact and the transducer
-true reflector and artifact are equal distance from the mirror
-
Characteristics of a mirror image artifact
______ article is a mirror image artifact that appears on a spectral Doppler display
Crosstalk
______ artifact is created when a sound wave propagates through a medium at a speed other than that of soft tissue. The correct number of reflectors are displayed but they appear an incorrect depths
Speed error
In speed error what happens when the mediums speed is slower than that in soft tissues?
- sounds travels slower than US system expects
- go-return time is too long
- system assumes reflectors are far from transducer
- reflectors placed too deep on image
- distances are overestimated
In speed error what happens when the mediums speed is faster than that in soft tissues?
- sounds travels faster than US system expects
- go-return time is too short
- system assumes reflectors are close to the transducer
- reflectors are located too shallow on image
- distances are underestimated
Propagation speed errors are also called ______
Range error artifact
- Correct number of reflectors
- improper depth
- appears as a step-off
Characteristics of speed error
