Diagnostic ultrasound ( PDFDrive )

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APPENDIX
Ultrasound Artifacts: A Virtual Chapter
For reverberation due to gas, see next section.
GAS-RELATED ARTIFACTS
Several physical properties of gases lead to unique artifacts in
ultrasound that help identify gas but also may hinder visualization
of other organs. hese properties include the very dissimilar
acoustic impedance of gas compared with sot tissues, making
them highly relective surfaces. he varied and ever-changing
shape of gas in the body, including foam, leads to variability of
its appearance even in the same ield. he very low density of
gases makes them quite compressible, and they can undergo
resonant oscillation in response to sound waves, leading to
ampliication of echoes. hese properties result in three distinct
artifacts, which can be present at the same time: reverberation,
ring-down, and dirty shadowing. 16
Reverberation Artifact
he physical pressure of the probe on the sot tissues, such as
the abdominal wall, lattens their shape in the near ield, making
them perpendicular to the surface of the probe and the incident
sound beam. Because gases conform to the shape of their containers,
they too will form a linear and perpendicular interface to
the incident sound beam, especially when in the form of a large
bubble. he highly relective gas interface will act like a mirror,
resulting in reverberation artifacts.
Click here to see an explanatory video of reverberation artifact
due to gas (Video A.13).
FIG. A.33 Reverberation Artifact. Small amount of gas within the
bladder is recognizable by the reverberation artifact (arrow).