Lack of a suitable oral contrast agent is the major drawback of abdominal MR imag-ing. FAC(Ferric ammonium citrat) was chosen
to use as MR oral contrast agent.Test tube,animal ex-periment and clinical study were done to resolve a series of issues,including relaxation enhancing charac-teristics,the most appropriate
concentration and clinical effectiveness of FAC. FAC demonstrates strong relaxation enhancing effect.At low concentration,the signal intensity increases with concentration due to
predominance of T_1 shortening。At high concentration,the signal intensity decreases with increase in concentration due to predominance of T_2 shortening. The most appropriate concentration for FAC is 2.1mmol/L, with which the signal intensity of gastro-intestinal tract can be properly enhanced both on T_1 and T_2 weighted images.Orally administered FAC can well mark the gastrointestinal tract and im-prove delineation of adjacent normal and abnormal structures。The best result was abtained for the group using hypotonic technique,in which the delineation of the left lobe of the liver, all parts of the pancreas and the lowest part of the common bile duct are all significantly improved compared to the plain-scan group.Therefore,FAC is an effective, inexpensive oral MR contrast agent with no side effects.