SPI Module 7 Image Features & Artifacts Flashcards
a feature that appears on the image but does not correspond to an anatomical structure is called:
artifact
the artifact that interferes with the ability to detect a low-contrast object is known as:
acoustic speckle
*acoustic speckle often considered to be an artifact because one-to-one correspondence between image brightness and scanned objects does not exist
the artifact that occurs from the thickness of the scanned tissue volume perpendicular to the scan plane is called:
elevational resolution
*also called: section thickness, slice thickness, out-of-plane focusing, width focusing
note: misdiagnosis may occur when echo fill-in occurs in the cystic structure. ex: debris appearance in the gallbladder that is not real
multiple equally-spaced reflections on the image decreasing in intensity is called:
reverberation
- reverb appears as more interfaces than actually exist. Harmonics has helped overcome reverb
- s portion of the sound beam reverberates between two highly reflected surfaces sending back multiple echoes from the same two interfaces
- comet-tail & ring-down are forms of reverberation artifacts
a type of reverberation artifact due to metal within the body is called:
comet-tail
acoustic energy emitted in a direction different than from the main axis of the sound beam is called:
side lobes
*artifact associated with propagation
- side lobes or grating lobes: energy off the main axis of single crystal TDR (side lobes) or arrays (grating lobes) can introduce positioning artifacts
- reflection appears at correct depth but lateral from true anatomy
- array TDR - not commonly seen due to corrective process (sub-dicing & apodization)
if the speed of sound is greater than 1540 m/s, the echo will be placed:
too close to the TDR
the absence or reduced intensity of echo information distal to a reflector is called:
shadowing
*artifacts associated with attenuation
- shadowing is caused by the sound beam intersecting a highly attenuating (highly reflective) structure, such as calcium (bone). when this happens most or the entire sound beam is redirected to the TDR, leaving a black space behind the strong echo
- this is one of the useful artifacts that assists in the diagnosis e.g. cholelithiasis, nephrolithiasis, calcified valve vs vegetation
an example of an artifact helpful in diagnosis is:
shadowing
the extension of color beyond the region of flow to the adjacent tissue is called:
blossoming
*also called: color bleed & can be eliminated by decreasing the transmit power and color gain
low-level echo image artifact caused by other electrical equipment is called:
noise
*electrical interference from other equipment in the room e.g. patient monitors may introduce 60-cycle interference. this appears as arc of vibrating bands across the monitor and is present (when the image is not frozen) on the screen whether the operator is imaging or not. all types of outside interference and noise can lead to degradation of contrast resolution.
Harmonics can be used to eliminate:
reverberation
when the Doppler gain is too high, which one of the following artifacts can appear on the image?
- aliasing
- cross talk
- comet tail
- shadowing
cross talk
*mirror image or crosstalk: spectral Doppler shows waveform above and below the baseline. It occurs when the Doppler gain is set to high or the Doppler angle is close to 90 degree
You are observing a sonographer artifact based on the interfaced patterns of scattered echoes. What are artifact are you imaging
Acoustic speckle
What will improve acoustic speckle
Use of frame rate
Use of compound imaging
