Magnetic resonance imaging of experimental inflammatory bowel disease: quantitative and qualitative analyses with histopathologic correlation in a rat model using the ultrasmall iron oxide SHU 555 C.

Objectives: To quantitatively and qualitatively characterize the MR findings of inflammatory bowel disease in a rat model after i.v. injection of the reticuloendothelial system cell specific ultrasmall iron oxide SHU 555 C. Materials and Methods: Colitis was induced in 15 rats using dinitrobenzene sulfonic acid instillation. Five rats served as controls. Tl- and T2-weighted spin-echo- and T2*-weighted gradient-echo-sequences were acquired at 2.4 Tesla before and immediately, 15, 45, 60, and 90 minutes, and 24 hours after i.v.-injection of SHU 555 C (0.1 mmol Fe/kg). MR images were evaluated quantitatively regarding thickness and signal-to-noise ratio (SNR) of the bowel wall and qualitatively regarding overall bowel wall signal intensity and the occurrence of bowel wall ulcerations. MR findings were correlated to histology. Results: The inflamed bowel wall was significantly thicker than the noninflamed bowel wall and 90 minutes after contrast injection it showed a significant reduction of SNR in Tl- (94 ± 27 vs. 61 ± 29; P < 0.01), T2-(67 ± 26 vs. 28 ± 17; P < 0.05), and T2*- (92 ± 57 vs. 10 ± 7; P < 0.05) weighted images as compared with unenhanced images. At 24 hours, the respective SNR values remained significantly reduced. The signal loss was homogeneous in 12 and focal in 3 of the 15 rats with colitis. Nine rats showed colonic wall ulcerations. In all but one animal (missed focal ulceration) MR findings correlated to the histologic findings. Conclusions: SHU 555 C leads to a significant signal intensity loss of the inflamed bowel wall in T1-, T2- and T2*-weighted images. SHU 555 C enhanced MRI findings correlate well with histologic findings.