Unit 4 Imaging Artifacts - DMU 3315

artifacts, anatomical, physiologic

Ultrasound ___ represent a wide range of misleading ultrasound appearances that do not accurately represent ___ structures of ___ exams.

real, sing, placed, brightness, shape, size

Artifacts can affect structures by making them…

• Not ___

• Mis___

• Mis___

• Incorrect ___

• Incorrect ___

• Incorrect ___

assumptions, straight line, same straight, constant, 1540 m/s, Attenuation rate, echo amplitude, height, axial, y, width, lateral, x, thickness, slice thickness, elevational, z, central axis, one echo, last, preceding, image acquisition, operator, system, system controls, transducer, electronic system

To create an image, the ultrasound system must have a set of rules/___ to process echoes

1. Ultrasound travels in a ___ ___ during transmission and echoes follow the ___ ___ path back

2. Speed of sound in the body is a ___ (___)

3. ___ ___ is uniform and predictable

4. Two comparable tissue reflectors in a similar location will generate a comparable ___ ___

5. The beam dimensions are small in ___ (___, ___-axis), ___ (___, ___-axis), and ___ (___ ___, ___, ___-axis)

6. Echoes originate only from the ___ ___ of the beam

7. Each reflector only generates ___ ___

8. The arriving echo was generated by the ___ emitted ultrasound pulse, not by any ___ pulses

9. The rate of ___ ___ exceeds the rate of physiologic events and the rate of transducer movement

10. The ___ is using the ___ appropriately

11. All ___ ___ have been adjusted correctly

12. The ___ elements and the ___ ___ components are functioning normally and without interference from surrounding equipment

System, Operator, Acoustics, Patient

Anytime the assumptions on which the ultrasound equipment has been designed are violated, artifacts will occur (SOAP):

1. ___

2. ___

3. ___

4. ___

Acoustics

Is essentially the way sound works within the body

system, real, real echoes, absence, real structures, operator, operator’s

• While ultrasound artifacts do not accurately reflect reality, to the ultrasound ___, artifacts appear perfectly “___”

• Artifacts represent ___ ___ or the real ___ of echoes; however, they DO NOT represent ___ ___ the way the operator would expect these to appear

• Alternatively, the ___ may misinterpret artifacts as real structures

• It is the ___ responsibility to determine whether the image accurately represents reality or not

Equipment related, Propagation group, Attenuation group

What are the three classifications of artifacts?

Equipment related

This classification of artifacts occurs anytime there is a defective part of the ultrasound instrument

Propagation group artifacts

• Comet tail

• Grating lobe

• Mirror image

• Range ambiguity

• Refraction

• Reverberation

• Ring-down

• Slice (section) thickness

• Speckle

• Speed error

Attenuation group artifacts

• Enhancement

• Focal enhancement

• Refraction (edge) shadowing

• Shadowing

Propagation

What classification of artifacts is comet tail?

Propagation

What classification of artifacts is grating lobe?

Propagation

What classification of artifacts is mirror image?

Propagation

What classification of artifacts is range ambiguity?

Propagation

What classification of artifacts is refraction?

Propagation

What classification of artifacts is reverberation?

Propagation

What classification of artifacts is ring-down?

Propagation

What classification of artifacts is slice (section) thickness?

Propagation

What classification of artifacts is speckle?

Propagation

What classification of artifacts is speed error?

Attenuation

What classification of artifacts is enhancement?

Attenuation

What classification of artifacts is focal enhancement?

Attenuation

What classification of artifacts is refraction (edge) shadowing?

Attenuation

What classification of artifacts is shadowing?

electrical interference, electrical, interference

• Strong ___ ___ from other nearby ___ devices can create ___ patterns

• In the image, we see horizontal lines traveling through the image, especially at the bottom (far field)

Faulty Elements

• Piezoelectric crystals may become damaged or breaks in wiring can occur

• Displayed as anechoic vertical lines

• To confirm:

  • Use more gel

  • Change approach

  • Use on various patients

  • Confirmed if still appears in exact location

crystals, wiring, anechoic, gel, approach, patients, location

Faulty Elements

• Piezoelectric ___ may become damaged or breaks in ___ can occur

• Displayed as ___ vertical lines

• To confirm:

  • Use more ___

  • Change ___

  • Use on various ___

  • Confirmed if still appears in exact ___

Focal Banding

• Horizontal brightness at the level of the focus

• Occurs because of the increased intensity in the focal zone

  • Results in increased amplitude of echoes

  • There’s increased intensity of the beam at the focal zone because the intensity equals power divided by area and since the area goes down at the focus, the intensity is increased.

• Adjust TGCs to fix

Horizontal brightness, focus, intensity, amplitude, focal zone, power, area, increased, TGCs

Focal Banding

• ___ ___ at the level of the ___

• Occurs because of the increased ___ in the focal zone

  • Results in increased ___ of echoes

  • There’s increased intensity of the beam at the ___ ___ because the intensity equals ___ divided by ___ and since the area goes down at the focus, the intensity is ___.

• Adjust ___ to fix

Side Lobes

• Caused by echoes from a strong reflector outside of the central beam

  • Most of the intensity is in the main sound beam, but sometimes additional beams travel out in directions not included in the main beam

• Occur with single element transducers

• Reduced with harmonics

• Results in a structure being shown as being laterally displaced or going out laterally

• In the image, the gallbladder is located behind the bowel and is not visible. The black oval next to the bowel is this artifact mimicking the gallbladder.

strong, central beam, intensity, single element, Side, Single, Strong, harmonics, laterally

Side Lobes

• Caused by echoes from a ___ reflector outside of the ___ ___

  • Most of the ___ is in the main sound beam, but sometimes additional beams (side lobes) travel out in directions not included in the main beam

• Occur with ___ ___ transducers

  • (___ lobes = ___ element = ___ reflector)

• Reduced with ___

• Results in a structure being shown as being ___ displaced

Grating Lobes

• Echoes from weaker beams outside the main beam from an array transducer

• Appears as duplicated structures laterally

  • Seen a lot with echo

• Reduced with harmonics

weaker, array, laterally, echo, harmonics

Grating Lobes

• Echoes from ___ beams outside the main beam from an ___ transducer

• Appears as duplicated structures ___

  • Seen a lot with ___

• Reduced with ___

Slice (Section) Thickness

• AKA Partial Volume Filling

• Beam is too thick in the elevation plane

• Gives the appearance of debris in an echo-free structure

Partial Volume Filling, thick, elevational, echo-free

Slice (Section) Thickness Artifact

• AKA ___ ___ ___

• Beam is too ___ in the ___ plane

• Gives the appearance of debris in an ___ structure

Speckle

• The granular appearance of images that is caused by the interference of echoes from the distribution of scatterers in tissue.

• The generation of this artifact can be compared to throwing a handful of marbles into a pond. Each marble generates a circular propagating wave. These waves combine together through the effects of constructive and destructive interferences.

• The location of the highest wave does not necessarily represent the location where the marble impacted the water, but rather where the marble waves come together to form a larger wave.

• Reduced by using:

  • Spatial compounding

  • Persistence

granular, interference, scatterers, circular propagating, constructive, destructive, larger, Spatial compounding, Persistence

Speckle

• The ___ appearance of images that is caused by the ___ of echoes from the distribution of ___ in tissue.

• The generation of speckle can be compared to throwing a handful of marbles into a pond. Each marble generates a ___ ___ wave. These waves combine together through the effects of ___ and ___ interferences.

• The location of the highest wave does not necessarily represent the location where the marble impacted the water, but rather where the marble waves come together to form a ___ wave.

• Reduced by using:

  • ___ ___

  • ___

Mirror Image

• Occurs when the beam encounters a large specular reflector

• Appears as duplication of objects opposite of a highly reflective structure

• May be reduced by changing approach

• Common behind the diaphragm

specular reflector, mirror, reflective structure, approach, diaphragm

Mirror Image

• Occurs when the beam encounters a large ___ ___ that acts as a ___

• Appears as duplication of objects opposite of a highly ___ ___

• May be reduced by changing ___

• Common behind the ___

Reverberation

• Occurs between two strong reflectors

  • Sound waves bounce back and forth between structures

• Appears as equally spaced extra reflectors on the image

  • Commonly occurs in the anterior portion of the bladder

• Reduced with harmonics (but can’t be completely eliminated)

strong reflectors, Sound waves, equally, bladder, harmonics, can’t

Reverberation

• Occurs between two ___ ___

  • ___ ___ bounce back and forth between structures

• Appears as ___ spaced extra reflectors on the image

  • Commonly occurs in the anterior portion of the ___

• Reduced with ___ (but ___ be completely eliminated)

False

True or False: Reverberation can be completely eliminated

Comet Tail

• Type of reverberation artifact

• Small focal reflectors cause a narrow reverberation artifact

• Often seen with and useful in the diagnosis of:

  • Adenomyomatosis/cholesterolosis of the gallbladder (GB)

  • Colloid thyroid nodules

reverberation, reflectors, reverberation, Adenomyomatosis, cholesterolosis, gallbladder, Colloid thyroid nodules

Comet Tail

• Type of ___ artifact

• Small focal ___ cause a narrow ___ artifact

• Often seen with and useful in the diagnosis of:

  • ___/___ of the ___ (GB)

  • ___ ___ ___

Ring-down

• Type of reverberation artifact

• Associated with gas – commonly seen in bowel

• Appears as high amplitude streaks (bright white)

• Can be helpful to identify gas in conditions such as:

  • Pneumobilia – air in the bile ducts

  • Pneumo = lung, air

• Emphysematous cholecystitis – gas in the gallbladder wall

• Abscesses containing air

  • An abscess is a collection of pus that forms in a localized area of the body

reverberation, gas, bowel, Ring, Gas, high, bright, Pneumobilia, Pneumo, Emphysematous cholecystitis, Abscesses, abscess

Ring-Down

• Type of ___ artifact

• Associated with ___ – commonly seen in ___

  • ___ = ___

• Appears as ___ amplitude streaks (___ white)

• Can be helpful to identify gas in conditions such as:

  • ___ – air in the bile ducts

  • ___ = lung, air

  • ___ ___ – gas in the gallbladder wall

  • ___ containing air

  • An ___ is a collection of pus that forms in a localized area of the body

Comet tail, ring down

___ ___ artifacts are short, tapering trails from highly reflective surfaces like metal or stones, which quickly fade with depth, while ___ ___ artifacts are long, continuous bands of echoes from gas bubbles causing fluid resonance, persisting further into the image.

Refraction

• AKA Duplication or Ghost Artifact

• Change in beam direction when the beam encounters a boundary between two materials with different propagation speeds

• Causes object to be projected laterally

• Appears as:

  • Widening (of object)

  • Duplication (of object)

• Can be reduced by sliding the transducer laterally

  • Happens quite frequently at the midline of the body, especially in the abdomen, because of the rectus abdominis muscles

  • This often affects the aorta in transverse, so you would just slide the transducer laterally

Duplication, Ghost Artifact, direction, propagation speeds, laterally, Widening, Duplication, sliding, laterally, midline, abdomen, rectus abdominis, aorta, laterally

Refraction

• AKA ___ or ___ ___

• Change in beam ___ when the beam encounters a boundary between two materials with different ___ ___

• Causes object to be projected ___

• Appears as:

  • ___ (of object)

  • ___ (of object)

• Can be reduced by ___ the transducer ___

  • Refraction happens quite frequently at the ___ of the body, especially in the ___, because of the ___ ___ muscles

• This often affects the ___ in transverse, so you would just slide the transducer ___

Edge Shadowing

• Type of refraction artifact

• Caused by a combination of reflection and refraction at the margin of a well-defined object

  • The beam is being bent because of refraction and because of attenuation in the area next to the bent beam, we end up with the shadow as shown in the diagram

• Appears as a shadow originating from the edge of a structure

• Reduced with spatial compounding

  • …because spatial compounding takes different averages/different frames of the beam shot at different angles. So, we’re actually able to angle the beam behind the structure and area that causes the refraction to help reduce those shadows.

refraction, reflection, refraction, well, bent, refraction, attenuation, shadow, shadow, edge, spatial compounding, spatial compounding

Edge Shadowing

• Type of ___ artifact

• Caused by a combination of ___ and ___ at the margin of a ___-defined object

  • The beam is being ___ because of ___ and because of ___ in the area next to the bent beam, we end up with the ___ as shown in the diagram

• Appears as a ___ originating from the ___ of a structure

• Reduced with ___ ___

  • …because ___ ___ takes different averages/different frames of the beam shot at different angles. So, we’re actually able to angle the beam behind the structure and area that causes the refraction to help reduce those shadows.

Multipath

• Beam reflects off the structure at an angle

• The reflection then bounces off another structure before heading back to the transducer

• Displays object deeper than it really is because the beam traveled longer

angle, another, deeper, longer

Multipath

• Beam reflects off the structure at an ___

• The reflection then bounces off ___ structure before heading back to the transducer

• Displays object ___ than it really is because the beam traveled ___

Propagation Speed Error

• Caused by a structure of lower or higher velocity than 1540 m/s (what the machine assumes)

• Appears as:

  • Vertical displacement behind area of non-1540 m/s

  • Faster = shallower

  • Slower = deeper

  • Distortion of shape of the object

• Cannot be eliminated

• The image shows a hemangioma that causes a slower velocity and therefore makes a part of the diaphragm appear deeper than it really is

1540 m/s, Vertical, 1540, shallower, deeper, shape, Cannot

Propagation Speed Error

• Caused by a structure of lower or higher propagation speed than ___ (what the machine assumes)

• Appears as:

  • ___ displacement behind area of non-___ m/s

• Faster = ___

• Slower = ___

• Distortion of ___ of the object

• ___ be eliminated

True

True or False: Propagation speed error cannot be eliminated

Range Ambiguity

• Occurs when echoes from the preceding pulse arrive at a time when another pulse has been emitted

• Causes:

  • Depth is relatively shallow and a low attenuating structure lies beyond the field of view (FOV)

  • Multiple focal zones - because image is stitched together

• Reduce:

  • For structure beyond FOV - decrease output power or gain

  • Switch to one focal zone

preceding, emitted, shallow, low, field of view, FOV, focal zones, output power, gain, focal zone

Range Ambiguity

• Occurs when echoes from the ___ pulse arrive at a time when another pulse has been ___

• Causes:

  • Depth is relatively ___ and a ___ attenuating structure lies beyond the ___ ___ ___ (___)

  • Multiple ___ ___ - because image is stitched together

• Reduce:

  • For structure beyond FOV - decrease ___ ___ or ___

  • Switch to one ___ ___

Shadowing

• Caused by a highly attenuating structure

  • Reflection

  • Scattering

  • Absorption

  • Refraction

  • Combination of any of these

• Complete absence of echo information behind attenuating structure

• Can be reduced by spatial compounding

  • Different angles can angle behind these attenuating structures

highly, Reflection, Scattering, Absorption, Refraction, absence, spatial compounding, angles

Shadowing

• Caused by a ___ attenuating structure

• RSAR:

  • ___

  • ___

  • ___

  • ___

  • Combination of any of these

• Complete ___ of echo information behind attenuating structure

• Can be reduced by ___ ___

  • Different ___ can angle behind these attenuating structures

Dirty Shadowing

• Also behind a strongly attenuating structure, but the structure produces some echoes but is highly attenuated in the process

• Appears as a hypoechoic shadow behind a structure

• Commonly seen with bowel

• Can be reduced by spatial compounding

strongly, echoes, hypoechoic, bowel, spatial compounding

Dirty Shadowing

• Also behind a ___ attenuating structure, but the structure produces some ___ but is highly attenuated in the process

• Appears as a ___ shadow behind a structure

• Commonly seen with ___

• Can be reduced by ___ ___

Enhancement

• Caused by a structure of low attenuation adjacent to a structure of normal attenuation

• Appears as a band of increased echogenicity behind an area of low attenuation

• Reduced by:

  • Gain & TGCs

  • Spatial compounding

• Can be diagnostically useful to distinguish fluid-filled from solid objects

  • Fluid filled objects have this artifact

  • Solid objects DO NOT have this artifact

Posterior Acoustic Enhancement, low, normal, increased, attenuation, Gain, TGCs, Spatial compounding, Fluid-filled, Solid

Enhancement

• AKA ___ ___ ___

• Caused by a structure of ___ attenuation adjacent to a structure of ___ attenuation

• Appears as a band of ___ echogenicity behind an area of low ___

• Reduced by:

  • ___ & ___

  • ___ ___

• Can be diagnostically useful to distinguish fluid-filled from solid objects

  • ___ objects have enhancement

  • ___ objects DO NOT have enhancement