Chapter 21 Artifacts Flashcards
What are the 6 assumptions in ultrasound
1.Sound travels in a straight line
2. Sound travels directly to a reflector and back
3. Sound travels in soft tissue exactly at 1540 m/s
4. Reflections arise only from structures positioned in the beams main axis
5. The imaging plane is very thin
6. The strength of a reflection is related to the characteristics of the tissue creating reflection
A violation of those ultrasound assumptions result in ______
Artifacts
What is reverberation artifact
Multiple equally spaced echoes cause by the bouncing of sound wave between 2 strong reflectors positioned parallel to the beam
What assumption does reverberation break
Sounds travels directly to a reflector and back
Comet tail artifact is also known as
Ring down
What does the comet tail artifact look like
Solid hyperechoic line directed downward
What assumption does the comet tail artifact break
Sound travels directly to a reflector and back
What is shadowing artifact
It happens beneath a structure with very high attenuation, hypoechoic or anechoic line extending downward
What assumption does shadow artifact breaks
The intensity of a reflection is related to the tissue creating reflection
Edge shadow is also known as
Shadowing by refraction
Describe edge shadowing
Hypoechoic region extending down from the edge of a curved reflector like a cyst
Edge shadowing breaks what assumption
The intensity of a reflection is related to the tissue creating the reflection
Describe enhancement artifact
Hyperechoic region beneath tissues with low attenuation
Enhancement breaks what assumption
- The intensity of a reflection is related to the tissue creating the reflection
Focal enhancement is also known as
Focal banding
What is focal enhancement
Side to side region of an image appears brighter than tissues at other depths. Happens often at the focus
What assumption does focal enhancement break
- The intensity of the reflection is related to the tissue creating the reflection
Define mirror image artifact
A string reflector creates a second structure (fake) that is always located deeper than the real structure. Both the real and the fake are at the same distance from the mirror
Mirror image on spectral Doppler is called
Crosstalk artifact
Mirror image breaks what assumptions
- Sound travels in a straight line
- Sound travels directly to a reflector and back
Speed error is also known as
Range ambiguity artifact or range error artifact
What is speed error
When a sound propagates through 2 different media, correct order of reflectors are displayed but at incorrect depths
What assumption does speed error break
- Sound travels exactly at 1540 m/s
Describe lobe artifacts
Creates a copy of reflector and are located side by side
What assumption does lobe artifacts break
- Reflections arise from structures located along the beams main axis
What resolution does the love artifacts degrade
Lateral
What are the two types of lobe artifacts
Side lobes, and grating lobes
Grating lobes are created by which kind of transducer
Array probes
Side lobes are created by which kind of transducer
Mechanical probes
What is refraction artifact
Transmission with a bend, creates second copy of reflector and it’s located side by side, think of the aorta
Refraction breaks what assumption
- Sound travels in a straight line
Slice thickness arrifact is also known as
Section thickness artifact, or partial volume artifact
Slice thickness artifact breaks what assumption
- The image plane is extremely thin
Elevational resolution is determined by
The thickness of the image plane
Lateral resolution artifact is also known as
Point spread artifact
Lateral resolution artifact occurs when
The beam is wider than the distance between 2 reflector located side by side. 2 objects appear as one
Axial resolution artifact occurs when
2 objects located parallel to sound beam appears as one if they are closer together than 1/2 the spatial pulse length
Multi path artifact breaks what assumption
- Sound travels directly to a reflector and back
Clutter is noise associated with
Doppler
