Acoustic Artifacts In 3D Imaging - Philips EPIQ 7 User Manual

Acoustic Artifacts Transducers
between the mirrors. The image of the head is reflected back and forth infinitely between the
two mirrors, creating the optical illusion of multiple heads. Reverberations are easily
identifiable, because they are equally spaced on the display.
Scattering is the diffuse, low-amplitude sound waves that occur when acoustic energy reflects
off tissue interfaces smaller than a wavelength. In diagnostic ultrasound, Doppler signals come
primarily from acoustic energy back-scattered from red blood cells.
Shadowing is the reduction in echo amplitude from reflectors that lie behind a strongly
reflecting or attenuating structure. This phenomenon occurs when scanning a lesion or
structure with an attenuation rate higher than that of the surrounding tissue. The lesion causes
a decrease in beam intensity, which results in decreased echo signals from the structures
beyond the lesion. Consequently, a dark cloud behind the lesion image forms on the display.
This cloud, or shadow, is useful as a diagnostic clue.
Side lobes (from single-element transducers) and grating lobes (from array transducers) cause
objects that are not directly in front of the transducer to be displayed incorrectly in lateral
position.
Speckle appears as tissue texture close to the transducer but does not correspond to scatterers
in tissue. It is produced by ultrasound wave interference and results in general image
degradation.
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

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,
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