Artifacts

What are the causes of artifacts?

• Equipment

• Technique

• Propagation

• Attenuation

What are the 4 assumptions of the ultrasound system?

• Sound travels in a straight line

• Echoes originate only from objects located on the beam axis

• Amplitude of returning echoes is related directly to the reflecting or scattering properties of distant objects

• The distance to reflecting or scattering objects is proportional to the round-trip travel time

Beam width perpendicular to the scan plane is greater than 2 adjacent reflectors

Slice Thickness/ Partial Volume

What does slice thickness artifact display as and how is it resolved?

Echoes within an anechoic structure

Use tissue harmonic imaging

Granular appearance of images that is result of interference of echoes from the distribution of scatterers in tissue

Speckle

Equally spaced reflections of diminishing amplitude with increased imaging depth

Reverberation

What causes reverberation

Two or more strong reflectors

Ring down is a type of?

Reverberation

Comet tail is a type of?

Reverberation

Appears as multiple parallel lines or solid band behind a reflector?

Ring Down

What causes ring down?

Vibrations of air bubbles

Duplication of a structure on the opposite side of a strong relfector?

Mirror Image

Mirror Image is a form of?

Reverberation

Where is mirror image commonly seen?

Pleura and diaphragm

Mirror Image can happen in Doppler (T/F)

True

Change in direction of the sound beam from one medium to the next?

Refraction

How does refraction display structures?

Laterally from their correct location

Duplication is an example of?

Refration

Duplication of a reflector

Multipath

Multipath artifact is a form of?

Refraction

Another name for multipath?

Ghost image

What is multipath caused by?

Altered paths of the sound beam

Region of increased brightness at focal zone?

Focal Banding

What is focal banding caused by?

Increased intensity of the beam

How to fix focal banding?

Adjust TGC’s

Additional weak beams from an array transducer

Grating Lobes

Beams from a single element in different directions than the beam

Side lobes

What do grating and side lobes do to the image?

Duplicate structures laterally to the true ones

Speed of sound is faster or slower than assumed and what slower or faster times do to the received echoes

Propagation Speed Error

Slower speed makes echo deeper

Faster speed makes echo closer

All echoes are not received before the next pulse is emitted

Range Ambiguity

Why does range ambiguity occur?

PRF is too high

How are the structures displayed with range ambiguity?

Closer to the surface

Weakening of echoes distal to structure?

Shadowing

What is edge shadowing caused by?

Refraction along the edge of a curved structure that decreases intensity of sound posterior to the curved edge

Strengthening of echoes distal to weakly attenuating structure?

Enhancement

Flow exceeds velocity range and doppler information is on wrong side of the baseline?

Aliasing

How to reduce aliasing?

• Increase PRF

• Shift Baseline

• Increase Doppler Angle

• Use lower operating frequency

• Use CW

Sudden burst of color doppler?

Flash/ Clutter

What is flash caused by?

Tissue or transducer motion

How to reduce flash?

Increase wall filter

Slice Thickness

Speckle

Comet Tail / Twinkle

Ring Down

Mirror Image

Refraction / Duplication

Multipath / Ghost Image

Focal Banding

Grating / Side Lobes

Range Ambiguity

Shadowing

Edge Shadowing

Enhancement

Aliasing

Flash

Damaged Crystal

How to fix clutter?

Wall filter

Reduced by increasing PRF

Aliasing and Flash

How to fix aliasing?

1. Shift Baseline

2. Increase PRF

3. Increase Doppler Angle

4. Decrease operating frequency

5. Switch to continuous wave

Reduced by harmonics?

• Side Lobes

• Grating Lobes

• Reverberation

Artifact reduced by changing probes?

Side Lobes

Reduced by changing approach?

Mirror Image

Flash

Reduced by Spatial Compounding?

1. Speckle

2. Edge shadowing

3. Enhancement

4. Dirty shadowing

Reduced by persistence?

Speckle

Reduced by sliding transducer laterally

Refraction

Reduced by adjusting TGCs?

1. Focal banding

2. Enhancement

Reduced by using one focal zone?

Range Ambiguity

Reduced by adjusting power input or gain?

1. Range ambiguity

2. Enhancement

3. Flash

How to fix flash?

Increasing PRF

Changing approach

Adjusting power input or gain

How to fix side lobes?

Harmonics

Changing probes

How to fix grating lobes?

Harmonics

How to fix reverberation?

Harmonics

How to fix Mirror-Image?

Changing approach

How to fix speckle?

Spatial Compounding

Persistence

How to fix edge shadowing?

Spatial Comounding

How to fix enhancement or shadowing?

Spatial Compounding

Adjust TGCs

How to fix refraction?

Slide transducer laterally

How to fix Focal Banding?

Adjust TGCs

How to fix range ambiguity?

Using one focal zone

Adjusting power input or gain