Artifacts Flashcards
(34 cards)
What are artifacts in imaging?
Artifacts are an error in imaging
Artifacts can misrepresent anatomical structures.
What are the causes of artifacts?
- Violation of assumptions
- Equipment malfunctions
- Poor design
- Operator error
Each cause can contribute to inaccuracies in imaging results.
What are the basic assumptions used in imaging?
- 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.
What is reverberation?
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.
What are the characteristics of reverberation?
- Appears in multiples
- Appears equally spaced
- Located parallel to the sound beam’s main axis
Recognizing these characteristics helps in identifying reverberation artifacts.
What is a comet tail artifact?
A form of reverberation that appears as a solid hyperechoic line directed downward.
Comet tails occur due to mechanical reflections.
What are the characteristics of comet tail artifacts?
- Appears as a single long hyperechoic echo
- Located parallel to the sound beam’s main axis
These traits distinguish comet tails from other artifacts.
What is shadowing in imaging?
Shadowing appears as a hypoechoic or anechoic region due to excessive attenuation.
It prevents the display of anatomical structures beneath the shadow.
What are the characteristics of shadowing artifacts?
- 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.
What is edge shadowing?
A special form of shadowing that appears as a hypoechoic region.
It occurs due to beam spreading after striking a curved reflector.
What are the characteristics of edge shadowing?
- Hypoechoic/anechoic color
- Results when the beam spreads after striking a curved reflector
Edge shadowing extends downward from the curved reflector’s edge.
What is enhancement in imaging?
Enhancement appears as a hyperechoic region beneath tissues with abnormally low attenuation.
It is the opposite of shadowing.
What are the characteristics of enhancement artifacts?
- Hyperechoic
- Result of too little attenuation
Enhancements can indicate areas of low density in tissues.
What is a mirror image artifact?
Created when sound reflects off a strong reflector and is redirected toward a second structure.
This artifact is located deeper than the real structure.
What are the characteristics of mirror image artifacts?
- A second copy of a true reflector
- The artifact appears deeper than the true reflector
This can confuse the interpretation of structures.
What is speed air artifact?
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.
What happens when the medium speed is slower than 1540 m/s?
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.
What happens when the medium is faster than 1540 m/s?
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.
What are the characteristics of speed air artifacts?
- Correct number of reflectors
- Improper depth represented
This can lead to diagnostic errors.
What are lobes in imaging?
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.
What are the characteristics of lobe artifacts?
- 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.
What are side lobes and grading lobes?
- Side lobes are created by a single crystal transducer
- Grading lobes are created by arrays of transducers
Both types can cause artifacts in imaging.
How can grading lobes be reduced?
By dividing each PZT element into small pieces, a process called sub-dicing.
This technique helps improve image quality.
What is refraction in imaging?
Created when a sound pulse changes direction as it strikes obliquely.
Refraction artifacts degrade lateral resolution.