Artifacts Flashcards
All artifacts are bad and should be eliminated.
T/F
False
What assumptions are made with ultrasound?
Sound travels in straight line
Reflections are produced by structures along main axis of beam
Intensity of echo corresponds to reflectors scattering strength
Imaging plane is thin
Sound travels to/from directly
Always travels at 1.54 mm/us
How can axial resolution cause artifact?
When two structures along axis of beam are mistaken as one
Artifact because of poor lateral resolution contributes to:
Incorrect representation of size and shape and to missing interfaces
What is acoustic speckle?
Granular appearance of images and spectral displays
What causes acoustic speckle?
Interference of echoes from distribution of scatterers in tissue
Where does acoustic speckle most often occur?
Near face of transducer
What interferes with the ability of the system to detect low-contrast objects?
Acoustic speckle
Elevational resolution artifacts can cause misdiagnosis when:
Echo fill-in occurs in cystic structure
Reverberation appears as:
More interfaces than actually exist
What helps counteract reverberation?
Harmonics
A type of reverb caused by metal objects:
Comet tail
Reverb produced by small gas bubbles
Ring down
Comet tail appears as multiple small bands that taper in gray scale.
T/F
False
In color
Where will the duplicate mirror image appear?
ALWAYS deeper than true structure
Multi path artifacts result in:
Improper brightness
Makes structure look farther away due to increase travel time of beam
Refraction can produce what kind of artifacts?
Edge shadowing with round structures
Ghost image artifact
What is a ghost image artifact?
A duplication of structures that appear side by side caused by refraction of the beam off the rectus abdominus muscle
*in transverse
Side lobes correspond with:
Single crystal transducers
Grating lobes correspond with:
Array transducers
Side lobes or grating lobes are caused by:
Acoustic energy emitted in a direction different than from main axis of sound beam
Side lobes / grating lobes make the reflection appear:
At correct depth but lateral to true anatomy
Subdicing and apodization help counteract side lobes.
T/F
False, grating lobes
If propagation speed in mass is faster than 1.54 mm/us then the mass will appear:
Too close to the transducer
If the propagation speed in a mass is slower than 1.54 mm/us the reflector will appear:
Too far from the transducer
Shadowing occurs when the sound beam intersects with a:
Highly attenuating structure
Ex: calcium/bone
Name two artifacts that are helpful with diagnosis.
Shadowing and enhancement
Near field artifact is caused by:
Reverberation
Common manifestation of color Doppler aliasing?
Wrap around of display, appears as reversal of flow
Ghosting with color Doppler shows:
True vessel closest to transducer with artifactual vessel below it
Cross talk occurs when:
Doppler gain is set too high or angle close to 90 degrees
What does crosstalk look like?
Shows waveform above and below baseline
Blossoming is another term for:
Color bleed
How can you eliminate color bleed?
Decreasing color gain
Color noise/clutter can be eliminated by:
Adjusting the wall filter
Ghosting may refer to:
Mirror imaging or when color is improperly assigned to stationary structures
