Spectral broadening is a display phenomenon that occurs when the number
of energy-bearing Fourier frequency components increases at any given point in
time. As a consequence, the spectral display is broadened. Spectral broadening
can indicate the disturbed flow caused by a lesion, and therefore it is important
diagnostically. However, broadening can also result from interaction between
flow and sample volume size, in which case it is an artifact.
Speed of sound artifacts occur if the sound propagation path to a reflector
is partially through bone, and the speed of sound is greater than in the average
soft tissue. Echo position registration artifacts will be produced. Reflectors appear
closer to the transducer than their actual distance because of this greater speed
of sound, resulting in a shorter echo transit time than for paths not containing
bone.
Acoustic Artifacts in 3D Imaging
Resolution, attenuation, and propagation artifacts are all common to 3D
imaging. Careful scrutiny of the original 2D images is necessary to identify and
preclude these types of artifacts from the 3D volume image.
Color gain, directional, and motion artifacts can present themselves in
3D imaging. Color and Color Power Angio gain artifacts are mainly related to
the use of excessive gain resulting in random color patterns in the 3D image that
might be interpreted as diagnostically significant. Directional artifacts are due to
aliasing or directional confusion: The velocity range must be set properly, and
the relationship between the transducer orientation and the flow vector must
be understood. Patient motion can produce flash artifacts that are less obvious
in 3D images than in 2D imaging.
Acquisition, rendering, and editing artifacts are specific to 3D volume
images. Acquisition artifacts are related to patient motion, organ motion, or
position-sensing errors. Rendering artifacts include elimination of structures by
limiting the region of interest boundaries, thresholding that eliminates structures,
and adjacent structure artifacts that add additional information or hide structures.
Editing artifacts result from data deleted from a rendered image.
Fetal limb deficit artifacts are specific to 3D volume images. Partially absent
fetal limb bones have been demonstrated. One explanation for the missing limbs
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Transducers
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