Artifacts

What artifact is this?

Reberferations

What assumption does reverberation violate?

sound travels directly from the reflector and back

What artifact is this

comet tail/ring down

What is a comet tail/ring down

a merged from of reverberation and a solid hyperachoic line that appears behind a strong reflector in ultrasound imaging.

What artifact is this

shadow

What is shadow artifact

anechoic or hypoechoic. high attenuation or scatter, and obscures digital image

Shadowing violates the assumption that

the reflection intensity is related to the tissues property

Edge shadow is also called

shadow by refraction

What artifact is this

edge shadowing

Edge shadowing is

The refraction at the edge of a curved structure. The beam is diverging and loses intensity

Enhancement artifact appears

hyperachoic

What artifact is this

enhancement

Enhancement artifact happens

Posterior to structures with low attentiations

Enhancement violates the assumption that

the intensity of the reflection is related to the tissue properties

focal enhancement looks like

a TGC error

What artifact is this

focal enhancement

What assumption does focal enhancement violate

the intensity of the reflection is related to the tissue properties

Mirror artifact is

a duplicate of the real anatomy and will ALWAYS be deeper than the real structure

What artifact is this

mirror

Mirror artifacts are at an _________ distance from the reflector

equal

The mirror artifact violates the assumptions that

sound travels in a straight line AND sound travels directly to the reflector and back

mirror artifact can also appear in our

color and spectral doppler analysis

Mirror artifact on doppler is called

cross talk

Propagation speed artifact is when

the prop speed is greater than 1.54 km/sec and the go-return-time is invalid

When the PS is > 1.54 km/sec

it makes the reflector shallower

When the PS is < 1.54 km/sec

it makes the reflector deeper

What artifact is this

Propagation speed

PS error is also referred to as

range error artifact

PS artifact violates the assumption that

sound travels at 1,540 m/sec

side lobe and grading lobe artifacts are

weak echos that are not in the main sound beam are put into the sound beam

Side lobe/ grading lobe artifacts violate the assumption that

Reflections arise only from structures in the main beam axis

subdicing will reduce

grating lobes by making it into smaller pieces

apodization will reduce

grating lobes by adjusting the voltages so the middle voltages are excited

Side lobes are created by _______ element transducers

single

Grating lobes are created by _________ element transducers

array

Refraction artifact

sound changes direction with oblique incidence and change in PS

like mirror is makes another copy but at he same depth

What artifact is this

refraction

Refraction degrades

lateral resolution

Refraction violates the assumption that

sound travels in a straight line

slice thickness artifact is the

height of the sound beam and the US pulls n reflections above and below sound beam and puts them in the beams main axis

happens in hallow structure like the bladder

What artifact is this

slice thickness

Slice thickness violates the assumption that

the imaging plane is always extremely thin

Lateral Resolution artifacts

ability to identify two structures side by side

will lump together structures and make it look like one

What artifact is this

lateral resolution

How to adjust lateral resolution

adjust focus to decrease beam width bc structures need ot be further apart than the beam width

axial resolutions is

the ability to identify structures that are parallel or on top of each other (front and back)

SPL/2

high freq transducers have better

axial resolution

Multi-path artifact

path reflects of 2nd structure

reflects off two structures

Multi-path artifact violates the assumption

that a pulse travels directly to a structure and back

Curved and oblique reflector artifacts is similar to the

multi path artifact

hits curved structure at oblique angle and bounces of so takes longer to get to transducer

Temporal Resolution artifact

slow shutter speed

cant accurately image structures in motions

low frame rate = low TR

Spatial resolution artifact

Overall detail

high line density = increased SR

greater pixel density = greater SR

Range ambiguity artifact

reflection by a very deep reflector that is beyond the depth of the image

The reflection from the first pulse reaches the reflector after the plus is emitted so the system assumes the reflection is from the second pulse so the echo is placed to close or shallow

Acoustic speckle artifact

low level echos that are not valuable to image

affect detial resolution

Electronic interference

disturbance from other electrical equipment

causes moving bands

degrades image quality

clutter or noise artifact

low level echos we don’t need

can be from side lobe or thickness artifact