Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

18 Small Animal Radiolo g y and Ultrasono graphy
Fig. 1-10 Longitudinal sonograms
of the cranial abdomen of a dog. The
liver and gall bladder are visible. The
portion of the liver deep to the gall
bladder appears more echogenic
(brighter) than the area cranial and
caudal to the gall bladder. This is
because of acoustic enhancement.
The fluid within the gall bladder
does not attenuate the ultrasound to
the same extent as the liver, thereby
increasing the strength of the echoes
from that portion of the liver deep to
the gall bladder.
Fig. 1-11 Longitudinal sonogram of
the urinary bladder of a dog. A series
of echogenic (bright) parallel lines
can be seen within the superficial
portion of the urinary bladder.
These are reverberation artifacts.
They may be originating at the skin
surface or from the dorsal bladder
wall. They are accentuated by the
high gain setting that was used to
obtain this image.
corresponding to the time elapsed from the signal pulse to echo reception. Comet-tail and
ring-down artifacts are forms of reverberation artifacts (Fig. 1-13). The comet-tail artifact may
originate at a highly reflective surface, such as a fluid:gas interface, and is helpful in indicating
the presence of air. The ring-down artifact commonly occurs within metals and often is
observed in association with biopsy needles or metallic foreign objects. Reverberations are
more likely to occur when the interface is close to the transducer, at highly reflecting surfaces,