In Vivo ¹⁹F MR Imaging Cell Tracking of Inflammatory Macrophages and Site-specific Development of Colitis-associated Dysplasia.

Abstract

Purpose To investigate whether the magnitude of in vivo fluorine 19 (¹⁹F) magnetic resonance (MR) imaging signal is associated with subsequent development of colitis-associated dysplasia after in situ fluorination of inflammatory macrophages in a mouse model of inflammatory bowel disease (IBD). Materials and Methods Experiments were approved by the institutional animal care and use committee. Mice in the experimental group (n = 10) were administered azoxymethane and dextran sulfate sodium to induce colitis-associated dysplasia. Five mice were in the noninduced control group. Animals were injected with a commercially available perfluorocarbon and were examined in vivo with an 11.7-T MR imager for up to 110 days. Colons were then harvested followed by high-spatial-resolution ex vivo MR imaging. Multiple colon segments with or without ¹⁹F signal were histologically graded and were correlated with ¹⁹F signal intensity by using a Spearman correlation test. The signal intensity in mice with colitis-associated dysplasia was compared with that in control mice with a two-tailed Mann-Whitney U test. Results Patchy distributions of ¹⁹F signal intensity in the colon wall were seen on in vivo and ex vivo images, representing chronic inflammation as shown by immunohistochemistry. Histologic scores of inflammation and site-specific development of colitis-associated dysplasia in the descending colon showed good correlation with normalized ¹⁹F signal intensity (r = 0.88, P = .033 for the ascending colon; r = 0.82, P = .006 for the descending colon). A significantly (P = .002) higher normalized ¹⁹F signal-to-noise ratio was found at sites that developed dysplasia (mean, 0.58 ± 0.09 [standard deviation]) as compared with sites that did not (mean, 0.17 ± 0.22). Conclusion ¹⁹F MR imaging cell tracking of macrophages can be used to assess local inflammation in a mouse model of IBD. The resulting local ¹⁹F signal intensity, representing the magnitude of inflammation, has a positive correlation with the development of colitis-associated dysplasia. ^© RSNA, 2016 Online supplemental material is available for this article.