Artifacts Flashcards
What is an artifact?
any appearance in an US image that does not accurately display the anatomy being scanned
Why does an artifact occur?
bc soundwaves do not behave as the machine assume it does, or something obstructs or alters the transmission of the soundwaves
What can cause artifacts?
the soundwaves not behaving as they are assumed to, one or more of the equipment settings are incorrect, faulty equipment and/or electrical interference
What causes an attenuation artifact and how can you fix or reduce this?
It’s caused by differences in tissue attenuation which affects the energy of the beam passing through different structures. This can make the images have uneven gain at varying depths. Can fix & reduce this by changing probe position, adjusting the beams focal zone and adjusting the TGC or the overall image gain.
What is a shadow artifact?
An artifact that creates a shadowing appearance - darkened lines posterior to a region. Can be caused by areas having higher attenuation compared to surrounding tissue, an eg. bone in the tissue. Can help adjust this by changing probe position, adjust focal zone, TGC or gain. Is used to help with diagnosis by using posterior shadowing as a terminological description.
what is enhancement artifact?
It looks like a highlightened/bright area behind a region - opposite to shadowing. Can be caused by tissue having lower attenuation than surrounding tissues, eg. fluid filled cysts. Can reduce this by changing position of probe, focal zone, TGC or gain. Is used to describe structures on US to help with diagnosis.
what is edge shadowing
also known as refraction artifact. it looks like line shadows that come off the sides of a circular structure. It’s caused by the beam striking the edge of a circular structure, deflected/refracted away, making it bend, causes that shadow bc it wont be detected by the US probe. Usually happens around the edges of fluid filled structures. Can help fix with changing probe position, adjusting focal zone, TGC or gain. Can be used to assist with diagnosis of structures.
What is a depth artifact?
a type of artifact that is caused by an incorrect display of depth of tissues. Can cause artifacts like reverberation, ring-down, comet-tail artifacts. Fix by changing probe position, adjusting focal zones, TGC or overall gain.
what is reverberation?
it is a depth artifact caused by the sound reflecting back and forth bw two parallel structures that both have strong reflectors causing multiple reflections. Appears as multiple reflectors (bright lines) that are not real structures, as it goes deeper the brightness/strength of echo reduces (starting bright and gets darker as it goes down). Using an ultrasound standoff pad (usually a membrane bag filled with water) to help decrease & prevent the echo reverberations when imaging structures close to the skin.
Ring down artifact
a depth artifact, that causes continuous lines of bright echos that extend right through the depth of the image, usually gets wider with depth and can appear similar to comet-tail artifact. Caused by the beam running into gas bubble reflectors causing reverberation (back & forth), causing echogenic lines as they return to the transducer. to fix or reduce it by changing probe position, adjusting focal zone, TGC and/or overall gain.
Comet-tail
is a depth artifact often caused by calcification and/ or cholestoral cyrstals (from gallbladder), creates series of multiple closely spaces bright bands of echoes that tapers off to a point with depth (look like comets), is a form of reverberation. Can change probe position, adjust focal zone, TGC and or overall image gain. Looks similar to the ring down artifact.
whats the difference bw ring-down and comet-tail?
they’re both depth artifacts that can appear similarly. a ring down artifact will create echogenic bright lines all the way down the depth of an image usually getting wider with depth. The comet tail artifacts are shorter in length and taper with depth
what is a beam path artifact?
this is an artifact that is caused by the machine assuming the ultrasound beam pathway to be in a straight line and can cause image artifacts when the beams path has been disruptered. This can cause mirror or refraction like artifacts.
what is refraction artifact?
it is a beam path artifact caused by the US beam changing direction as it passes through an interface with two tissues of significant different propogation speeds, causing refraction and making an object be displayed twice (doubling). Try moving probe to either side of of the muscle to help reduce or get rid of this artifact
mirror image artifact
this is a beam artifact that is caused by an object sitting close to a very strong reflector, which can display the image twice in various positions (looks like a mirror), happens often with the liver and diaphragm. Try moving probe position but being aware of this artifact can help
