Journal of Ultrasound in Medicine, Vol 3, Issue 8 337-340, Copyright © 1984 by American Institute of Ultrasound in Medicine
Displacement of the diaphragmatic echo by hepatic cysts: a new explanation with computer simulation
J. Mayo and P. L. Cooperberg
Previous demonstrations of distal displacement of interfaces deep to cystic
structures have been based on only the slower speed of sound through the
cystic structure, which has been postulated to cause an apparent
discontinuity in the echo from the diaphragm deep to a cyst. The authors
found cysts whose identification could not be explained by this theory
because they were too small or the diaphragm was displaced in such a manner
that the explanation would not hold true. They propose that, in addition to
the slowing of the speed of sound through the cyst, refraction at the edge
of the cyst can cause the apparent discontinuity. Since the machine does
not distinguish the sound beam as having been refracted, the echo is
displayed at the appropriate distance along the vector in the direction in
which the transducer was pointing at the time. A computer simulation is
used to confirm this theory.
