Artifacts

Reverberation Artifact

• multiple, equally spaced echoes

• bounce off sound waves between 2 strong reflectors parallel to the sound beam

• only the first 2 are real

• invalidates assumption 2

Comet Tail (a/k/a Ring Down Artifact)

-closely spaced reverberations
-solid hyperechoic line directed downward
-reflectors with high speed or gas bubbles
-parallel to the sound beam’s main axis
-invalidates assumption 2

Shadowing

-too much attenuation
-beneath structure
-invalidates assumption 6

Edge Shadow (a/k/a Shadowing by Refraction)

-hypoechoic region extending down from edge of curved reflector
-parallel to the sound beam
-invalidates assumption 6

Enhancement

-low attenuation
-invalidates assumption 6

Lobes

-side by side
-degrades lateral resolution
-to reduce: apodization or subdicing (& harmonics)
-invalidates assumption 2

Refraction

-side by side at exact same depth
-invalidates assumption 1

Speed Error (a/k/a Range Error)

-invalidates assumption 3

Mirror Image

-below

-invalidates assumptions 1 & 2

Slice Thickness

(a/k/a Section Thickness / Partial Volume)
imaging plane is 3D
NOT razor thin or uniform
flares out - so reflects above or below
reduced with thinner imaging planes, e.g. 1.5D array transducers
invalidates assumption 5

Range Ambiguity

• occurs when a reflecting structure is located deeper than the imaging depth of the image

• eliminated by increasing PRP

Noise

• small amplitude echoes

• electrical interference/signal processing/spurious reflections

• more likely to affect low-level hypoechoic regions

• reduced by harmonic imaging

Speckle

• type of noise

• results from constructive & deconstructive wavelets

• reduced by harmonic imaging

Clutter

• type of noise

• false echoes arising from outside the main sound beam

• reduced by harmonic imaging