American Journal of Roentgenology, Vol 171, 475-481, Copyright © 1998 by American Roentgen Ray Society
Improved retroperitoneal and gastrointestinal sonography using oral contrast agents in a porcine model
D Muradali, PN Burns, G Pron, D Hope-Simpson and S Wilson
Department of Medical Imaging, The Toronto Hospital, Ontario, Canada.
OBJECTIVE: Abdominal sonography can be compromised by the presence of air
within the scanning field. Gas-displacing oral contrast agents have the
potential to improve the diagnostic yield of routine abdominal sonography.
The purpose of this study was to investigate two oral contrast agents and
water and to compare their ability to improve abdominal sonography with an
unenhanced baseline study and each other in a porcine model. MATERIALS AND
METHODS: The acoustic properties of agent 1 (Oralex; Molecular Biosystems,
San Diego, CA), a suspension of polydextrose in purified water; agent 2, a
homemade agent (named BMW), a suspension of polysaccharide particles in
water; and water were assessed in finger phantoms under laboratory
conditions. Each solution was subsequently evaluated in 10 pigs, for a
total of 30 animals. The bolus character, gas artifact, abdominal viscera,
vessels, and gut wall were graded from 1 (nondiagnostic) to 5 (excellent)
in the unenhanced and postcontrast states. Postcontrast grades were
compared with unenhanced baseline grades using the Wilcoxon signed-rank
correlation. Agents were compared with each other using the Mann-Whitney U
test (Wilcoxon rank sum test). RESULTS: All three solutions were
hypoechoic, were homogeneous, and showed minimal attenuation and
backscatter. Both oral contrast agents had excellent bolus characteristics
(agent 1, grade 5.0 +/- 0; agent 2, grade 4.6 +/- 0.5), displaced gas from
the scanning field, and significantly improved visibility in all
categories, particularly the gut. No difference in performance was found
between agents 1 and agent 2. Water had poor bolus characteristics (grade
1.3 +/- 0.48) and did not improve visibility over baseline. CONCLUSION: The
acoustic in vitro properties of agent 1 and agent 2 approach that of an
ideal sonographic contrast agent. Both agents are superior to water in
their improvement of direct visualization of the retroperitoneum and the
gut in abdominal sonography in a porcine model.