IN-VIVO ANIMAL TESTS OF AN ARTIFACT-FREE CONTRAST AGENT FOR GASTROINTESTINAL MRI

A variety of shortcomings are associated with most currently used gast rointestinal contrast agents for magnetic resonance imaging (MRI). Art ifacts resulting from peristalsis and other motions in the abdominal r egion are produced by many positive contrast agents (which increase si gnal intensity). Although this is not a problem for negative contrast agents (which decrease signal intensity), some negative contrast agent s produce magnetic susceptibility artifacts that are especially pronou nced at high field strength and with gradient echo pulse sequences. Th ese susceptibility artifacts are produced by both paramagnetic and dia magnetic agents. It has been demonstrated in phantoms, however, that s usceptibility matching can be used to produce contrast agents with des irable relaxation and contrast properties but without deleterious susc eptibility artifacts. We now report results of animal tests of such an oral contrast agent, consisting of a suspension of superparamagnetic iron oxide particles and diamagnetic barium sulfate particles, compare d to individual suspensions of the iron oxide and of the barium sulfat e. Iron oxide was the least effective and the matched susceptibility m ixture was the most effective for the intestine, which has traditional ly been the most difficult region of the GI tract to visualize clearly . Matched susceptibility mixtures, which are inherently able to yield images free of susceptibility artifacts without compromising contrast, show promise of being improved oral negative contrast agents fur use in gastrointestinal MRT. (C) 1997 Elsevier Science Inc.