Abstract

Superior mesentric lymph nodes which lie as a chain near the small intestine are difficult to visualize in the rat with MRI either with or without the use of contrast agents. We previously demonstrated that the oral administration of an ultrasmall superparamagnetic iron oxide (AMI-227) produces a brightening of the lumen of the GI tract with a T1-weighted spin-echo pulse sequence. We have also shown that AMI-227 darkens abdominal lymph nodes. In the present study we show that the combined oral and intravenous administration of AMI-227 produces a brightening of the lumen of the GI tract and a darkening of the superior mesenteric lymph node chain. As a result of these combined and opposing effects on image signal intensity, a necessary contrast is established to reliably locate the superior mesenteric lymph nodes in vivo, which, to our knowledge, have been elusive by other techniques.