Physics chapter 8 Flashcards
5 categories of artifacts
-Image detail resolution related
-locational artifacts
-attenuation artifacts
-phase related
-doppler artifacts
Section thickness artifact
If the slice thickness is wider then the object the surrounding tissue may be displayed along with the object of interest
Noise from slice thickness
partial volume artifact
Acoustic Speckle
Interference of echoes returning at the same time from multiple scatterers due to destructive/constructive interference
propagation artifact.
Reverberation artifact
Multiple echoes or reflections in ultrasound an artificial image due to delay of an echo that has been reflected back and forth before returning to transducer
Comet tail
Grey scale ultrasound finding when small calcific/crystalline/highly reflective object are interrogated
special form of reverberation
due to metal
twinkle artifact
Colour artifact equivalent to comet tail
Ring down artifact
From air
When sound reverberates with air sac boundaries are redrawn repeatedly creating a bright tail like image below air sac
Emphysematous Cholectysititus
Gas in gall bladder wall or lumen
Hematometra with presence of air bubbles inside represented by ring down artifact can lead to endometriosis.
Multi path artifact
Incorrectly displays the depth of a structure results in insonification of specular at an oblique angle Not perpendicular
the machine believes echos return in a straight line
Mirror Image (Ghost)
Highly reflective surfaces such as lung diaphragm may result in multiple reverberations of sound waves causing some echoes to be delayed returning to transducer
superficial structure may appear deeper
Refraction
beam is directed away from correct oath (refracted) laterally displaced because transducer assumes the echo is straight
Side and grating lobes
Grating lobes are weaker lobes in directions other than the main beam direction
Energy is usually low enough that it goes unnoticed but if the lobes encounter strong specular reflectors the main beam will create a structure or cloud over the image
Range ambiguity artifact
Result in reflected data from previous acoustic transmit adding to reflection of current acoustic line
Shadowing
shadowing is caused by excessive reflection, absorption or refraction
Edge (refractive) shadowing
Occurs when a beam of US refracts at the edge of rounded structure
caused by excess refraction
Enhancement
reciprocal of shadowing most common beneath a fluid filled structure
Focal banding/ focal enhancement
side to side region of image appears brighter than tissues at other depths
occurs in the focal region of the transducer when using multiple focal lengths
caused increased intensity due to multiple foci
