Artifacts Flashcards
Reflection
Sounds ave strikes specular interface, rebounds off
Angle of incidence = angle of reflection
Refraction / ghost image artifact cause
Sound wave bents as it passes through tissue with different sound velocity
Machine assumes straight line
Requires oblique incidence
Refraction / ghost image artifact appearance
Structures misplaced laterally
Side by side double image
Fixing refraction/ghost image
Angulation change
Scatter
Waves scatter in many directions off small or rough objects
Higher frequency = increased scatter
Reverberation artifact / multi path reflection artifact
Multiple, equal spaced echoes caused by wave bouncing between 2 strong reflects parallel to main beam
May look like rungs of a latter
Parallel to sound beam
Fixing reverberation artifact
Angulation change
Contrast and color go through
Comet tail artifact / ring down artifact
Closely spaced reverberations merge, causes single hyper echoic line
Parallel to main sound beam
Near field reflection artifact cause
Strong acoustic signals close to transducer
Return signal reflected back off transducer, creates additional images
i.e. artifact at apex
Near field reflection artifact fix
Contrast
Shadow artifact cause
Hypoechoic / anechoic region below a structure causes strong attenuation
Reduction in strength of returning echo caused by intervening structure
Prevents display of true anatomic structures
Shadow artifact fix
Change angle
Enhancement artifact
Hyperechoic region below tissue with low attenuation
Opposite of shadowing
Multipath duplication / mirror image artifact cause
Sound hits reflector and returns to transducer
Some of reflection bounces back at an angle and takes longer to come back, creating a separate deeper structure
Multipath duplication / mirror image appearance
Appears as replica of true reflector (artifact always deeper)
Color is fooled
Resolution artifact
2 reflectors that are closely spaced together appear as one
Axial / longitudinal resolution
Differentiating objects parallel to or along long axis
Better with higher frequency
Lateral resolution
Differentiating structures perpendicular to beam
Beam width is key
Stitch artifact
3D image made by stitching together multiple cardiac cycles
Velocity error artifact
Sound propagates through some structures at velocity other than 1540 m/s
Lobe artifact cause
Strong reflector outside main beam may generate echoes detected by transducer
Lobe artifact appearance
Misplaced echoes displayed as having originated within main beam
May overlap with normal structure
Range ambiguity artifact appearance
Distal structure appears to float over cardiac structures, doesn’t move with them
Range ambiguity cause
Structure distal to image with echoes returning from a different pulse
Fixing range ambiguity
Increase depth or alter transducer position
Linear artifact in ascending aorta
Reverberation
More common when aortic diameter > LA diameter
Moves with posterior aortic wall
Beam width artifact / slice thickness artifact
Occur distal to focal zone where lateral resolution is worst
Lateral resolution degraded, may have alteration in size or shape of a structure
Improving beam width artifact
Focusing
PRF as imaging depth increases
PRF decreases
Avoiding range ambiguity artifact
PRF is reduced when scanning deeper structrues
Spectral doppler mirror-image artifact
Symmetric spectral images on opposite side of baseline from true signal created
Reducing spectral doppler mirror-image artifact
Decrease power output or gain
Optimize angle between beam and doppler flow
Distinguish LV thrombus from artifact
Increase frequency
Decrease depth
Using multiple views
Use contrast
Mirror image structure locations
Structure located in front of highly reflective surface
Near field clutter artifact
High amplitude oscillations of piezoelectric elements
Affects near field of US beam
Eliminating near field clutter artifact
Higher frequency Decreasing depth Changing views Contrast Harmonic imaging
Figure of 8 artifact
From atrial septal occluder device
Looks like 8 in LA
Shielding artifact
White echoes
Bright beam of ultrasound artifact that obscures visualization beyond that point
Ghosting
Color doppler distorted beyond anatomic borders due to multiple reflections
