Acoustic artifacts

Noise/speckle

Caused by non-specular reflections from rough surface

More speckle seen with lower frequency transducers

Scattering causes wave interference, resulting in speckled appearance

Typically associated with liver, spleen, thyroid tissue

Side lobes

Weak off axis portions of the beam; seen with single PE element

Grating lobes

Weak off axis portions of the beam; seen with an element array

When wea, off axis portions of the beam encounter a string reflector, the reflected energy may become part of the main beam

Reverberation

Caused by reflection of US back and forth between two closely spaced interfaces

Multiple echogenic lines equally spaced apart

Ring down artifact

Type of resonance artifact

Occurs with gas/tissue interface

Vertical streak of parallel lines project posterior to interface

Comet tail artifact

Series of echoes caused by small multiple reflections from a highly reflective object

Forms a single long hyperechoic artifact

Posterior enhancement

Anechoic structures allow sound to be transmitted through and there is increased reflection from structures posteriorly

Posterior shadowing

Echogenic structures reflects majority of sound, no sound is transmitted posteriorly

Bayonet artifact

Propagation speed artifact that causes the appearance of a bent needle

Caused by variations of densities

Mirror image

Created as sound reflects off a strong reflector

Appears as a second copy of structure deeper to image

Range ambiguity

Shallow depth = High PRF

Shallow reflectors reflect sound energy that arrives at the transducer before the rest of the pulse finishes transmitting

Causes confusion on echo placement in near field

Refraction artifact

Refraction of the beam between two dissimilar media can cause a structure to appear more lateral than the actual structure

Volume averaging

AKA slice thickness or beam width artifact

Affect eval of superficial lesions

Reduced with standoff pad

Can cause solid lesions to appear anechoic

Echo texture of adjacent structures is then averaged to that of lesion

Aniostrphy artifact

Falsely hypoechoic areas of tendon

Occurs when transducer is not completely parallel to tendon

Reduced by rocking the transducer to make the face of the transducer more parallel to tendon

Element damage

If a PE element is not functioning, data will be missing from the image

If the probe is a single element, the entire image will not be displayed

A linear, sector or vector will demonstrate the area of no reflected info as a black vertical line

An annular array with demontsrate an anechoic horizontal arch of missing data

A curved array will demonstrate a vertical line of missing data

Nyquist limit

Maximum frequency that can be displayed is ½ PRF

Blooming

Color obscures gray scale display of soft plaque becuase of resolution of color Doppler is lower than the gray scale

The adjacent flow causes the pixel to be displayed as color instead of gray scale info

Crosstalk

Mirror image of Doppler signal

Which of the following is an artifact caused by gas-tissue interface

Ring down

Mirror

Speckle

Shadowing

Ring down

What acoustic artifact is associated with adenomyomatosis

Comet tail

Which of the following results in a copy of a structure displayed laterally on the image?

Ring down

Mirror

Enhancement

Refraction

Refraction

Anisotropy artifacts are seen on the evaluation of:

Tendons

How can you differentiate element damage from posterior shadowing when using a linear transducer?

Identify where the shadowing beings

What causes clutter artifact?

Low velocity scale settings

Blossoming of the spectral Doppler waveform can cause:

Overestimation of PSV