Comparison of three dimensional magnetic resonance imaging in conjunction with a blood pool contrast agent and nuclear scintigraphy for the detection of experimentally induced gastrointestinal bleeding

Abstract

Background and aims - To compare the performance of 3D magnetic resonance imaging (MRI) in conjunction with an intravascular contrast agent with that of scintigraphy, with respect to detection and localisation of gastrointestinal haemorrhage in vivo in pigs. Methods - Intraluminal bleeding sites were surgically created in the small bowel and colon of six pigs. The animals underwent scintigraphy with 99mTc labelled red blood cells and 3D MRI following administration of an intravascular contrast agent (NC100150) at five minute intervals over 30 minutes. For analysis, the intestinal tract was divided into six segments. Based on the two evaluated methods, each segment was characterised on a five point scale regarding the presence of a bleed. At autopsy, the surgically manipulated bowel segments were inspected for the presence of haemorrhage. Results - Bleeding was confirmed at autopsy in 18/36 segments. Contrast extravasation with subsequent movement through the bowel could be documented on MRI data sets. All segments were correctly characterised, resulting in 100% sensitivity and specificity for MRI. Based on scintigraphy, interpretation of seven segments (19%) was false (sensitivity/specificity of 78%172%). Differences in diagnostic performance were evident in the receiver operator characteristic (ROC) analysis, with an area under the MRI curve of 0.99 and under the scintigraphy curve of 0.85. Conclusion - In conjunction with an intravascular contrast agent, 3D MRI permits accurate detection and localisation of gastrointestinal bleeding. The extent and evolution of intestinal bleeding can be determined with repeated data acquisition.