Experimental gastrointestinal hemorrhage: detection with contrast-enhanced MR imaging and scintigraphy

PURPOSE: To examine the use of O-methoxy poly(ethylene)glycol-O'-succinyl-N-epsilon-poly(L-lysyl) gadolinium diethylenetriaminepentaacetic acid (MPEG-PL-Gd-DTPA) as a potential magnetic resonance (MR) angiographic contrast agent for the detection of gastrointestinal (GI) bleeding.
MATERIALS AND METHODS: MPEG-PL-Gd-DTPA was used for blood pool enhancement, and MPEG-PL-technetium-99m DTPA was used for planar nuclear imaging studies. GI bleeding was tested in rats by controlled injection of contrast material-doped blood through a jejunostomy catheter. MR imaging was performed at 1.5 T.
RESULTS: Ideal flip angle, used with a spoiled gradient-echo pulse sequence, was 40 degrees. The smallest amount of hemorrhage detected at MR imaging was 0.05 mL; at nuclear imaging it was 0.02 mL. With the superior spatial resolution of MR imaging, individual loops of contrast material-filled bowel were identified and bleeding points were pinpointed.
CONCLUSION: GI hemorrhage can be easily detected at MR imaging if a long circulating macromolecular contrast agent is used to decrease the T1 of extravasated blood.