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Experimental gastrointestinal hemorrhage: detection with contrast-enhanced MR imaging and scintigraphy
H Gupta1, R Weissleder, A A Bogdanov
1Department of Radiology, Massachusetts General Hospital, Boston 02114, USA.
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.