Artifacts

Question 1

What are artifacts in imaging?

Answer 1

Artifacts are an error in imaging

Artifacts can misrepresent anatomical structures.

Question 2

What are the causes of artifacts?

Answer 2

• Violation of assumptions
• Equipment malfunctions
• Poor design
• Operator error

Each cause can contribute to inaccuracies in imaging results.

Question 3

What are the basic assumptions used in imaging?

Answer 3

• Sound travels in a straight line
• Sound travels directly to a reflector and back
• Sound travels in soft tissue at 1540 m/s
• Reflection arises only from structures positioned in the beam’s main axis

These assumptions are crucial for accurate imaging.

Question 4

What is reverberation?

Answer 4

Reverberations appear as multiple equally spaced echoes caused by the bouncing of the sound wave between two strong reflectors parallel to the ultrasound beam.

This can lead to misleading interpretations of structures.

Question 5

What are the characteristics of reverberation?

Answer 5

• Appears in multiples
• Appears equally spaced
• Located parallel to the sound beam’s main axis

Recognizing these characteristics helps in identifying reverberation artifacts.

Question 6

What is a comet tail artifact?

Answer 6

A form of reverberation that appears as a solid hyperechoic line directed downward.

Comet tails occur due to mechanical reflections.

Question 7

What are the characteristics of comet tail artifacts?

Answer 7

• Appears as a single long hyperechoic echo
• Located parallel to the sound beam’s main axis

These traits distinguish comet tails from other artifacts.

Question 8

What is shadowing in imaging?

Answer 8

Shadowing appears as a hypoechoic or anechoic region due to excessive attenuation.

It prevents the display of anatomical structures beneath the shadow.

Question 9

What are the characteristics of shadowing artifacts?

Answer 9

• Hypoechoic or anechoic background color
• Result of too much attenuation
• Located beneath structures with abnormally high attenuation

This phenomenon obscures true anatomy in ultrasound images.

Question 10

What is edge shadowing?

Answer 10

A special form of shadowing that appears as a hypoechoic region.

It occurs due to beam spreading after striking a curved reflector.

Question 11

What are the characteristics of edge shadowing?

Answer 11

• Hypoechoic/anechoic color
• Results when the beam spreads after striking a curved reflector

Edge shadowing extends downward from the curved reflector’s edge.

Question 12

What is enhancement in imaging?

Answer 12

Enhancement appears as a hyperechoic region beneath tissues with abnormally low attenuation.

It is the opposite of shadowing.

Question 13

What are the characteristics of enhancement artifacts?

Answer 13

• Hyperechoic
• Result of too little attenuation

Enhancements can indicate areas of low density in tissues.

Question 14

What is a mirror image artifact?

Answer 14

Created when sound reflects off a strong reflector and is redirected toward a second structure.

This artifact is located deeper than the real structure.

Question 15

What are the characteristics of mirror image artifacts?

Answer 15

• A second copy of a true reflector
• The artifact appears deeper than the true reflector

This can confuse the interpretation of structures.

Question 16

What is speed air artifact?

Answer 16

Occurs when a sound wave propagates through a medium at a speed other than 1540 m/s.

The speed of sound affects the perceived depth of reflectors.

Question 17

What happens when the medium speed is slower than 1540 m/s?

Answer 17

Pulses return slowly, causing the system to assume reflectors are far from the transducer, making reflectors appear deeper than true.

This can lead to misinterpretation of imaging results.

Question 18

What happens when the medium is faster than 1540 m/s?

Answer 18

Pulses return quickly, leading the system to assume reflectors are close, making reflectors appear shallower than true.

This can also distort the representation of structures.

Question 19

What are the characteristics of speed air artifacts?

Answer 19

• Correct number of reflectors
• Improper depth represented

This can lead to diagnostic errors.

Question 20

What are lobes in imaging?

Answer 20

Appear when sound energy is transmitted in any direction other than along the beam’s main axis, degrading lateral resolution.

Lobes can introduce false representations of structures.

Question 21

What are the characteristics of lobe artifacts?

Answer 21

• A second copy of the true reflector
• The artifact and true reflector are located side-by-side at the same depth

This can confuse the interpretation of spatial relationships.

Question 22

What are side lobes and grading lobes?

Answer 22

• Side lobes are created by a single crystal transducer
• Grading lobes are created by arrays of transducers

Both types can cause artifacts in imaging.

Question 23

How can grading lobes be reduced?

Answer 23

By dividing each PZT element into small pieces, a process called sub-dicing.

This technique helps improve image quality.

Question 24

What is refraction in imaging?

Answer 24

Created when a sound pulse changes direction as it strikes obliquely.

Refraction artifacts degrade lateral resolution.

Question 25

What are the characteristics of refraction artifacts?

Answer 25

* A second copy of the reflector * The copy is side-by-side at the same depth as the reflector ## Footnote This can lead to misinterpretation of the location of structures.

Question 26

What is a lateral resolution artifact?

Answer 26

Occurs when a pair of side-by-side reflectors are closer than the width of the sound beam, causing them to appear as one. ## Footnote This results in a wide line rather than a narrow dot.

Question 27

What is an axial resolution artifact?

Answer 27

Created when closely spaced structures are struck by long pulses, causing one to obscure the other. ## Footnote Shorter pulses with higher frequency minimize axial resolution artifacts.

Question 28

What is a multipath artifact?

Answer 28

Created when sound pulses glance, a second structure on the way to or from the primary reflector. ## Footnote Multipath artifacts can lead to misinterpretation of the image due to the presence of additional reflections.

Question 29

What is temporal resolution?

Answer 29

The ability to precisely identify moving objects. ## Footnote Temporal resolution is best with high frame rates.

Question 30

What does temporal resolution artifact cause?

Answer 30

Inability of exact positioning of moving reflectors. ## Footnote This can lead to inaccuracies in imaging moving structures.

Question 31

What is range ambiguity artifact?

Answer 31

Occurs when reflecting structure is located deeper than the imaging depth range. ## Footnote Majority of artifacts are eliminated by increasing PRP for deeper imaging.

Question 32

What is speckle in ultrasound imaging?

Answer 32

Acoustic speckles noise, resulting from constructive and destructive interference of small sound wavelets. ## Footnote Speckle can obscure important details in the ultrasound image.

Question 33

What is clutter in ultrasound imaging?

Answer 33

A form of noise; presence of false ultrasound signals. ## Footnote Clutter can interfere with the interpretation of actual ultrasound signals.

Question 34

What is the goal of harmonic imaging?

Answer 34

To reduce an image's noise content by selectively distinguishing reflections from noise. ## Footnote This increases the signals and noise ratio, improving image clarity.