Quantitative magnetic resonance imaging in the transgenic APC ^δ468 mouse model of hereditary colon cancer

In this study, we investigated the use of high-resolution magnetic resonance imaging (MRI) methods for in vivo detection and quantitative characterization of colorectal tumors in the transgenic APC^δ468 mouse model. High-resolution T₁-weighted (T₁W) images, T₂-weighted (T₂W) images, and dynamic contrast-enhanced (DCE) measurements were performed using a 7.0 T small-animal imaging system (N 5 10). Individual tumors were identified on both T₁Wand T ₂Wimages. Twenty-eight tumors (2.8 ± 0.9 mm, mean ± SD) were detected with high-resolution MRI across a distance of roughly 3 cm from the rectum to the splenic flexure, whereas 29 tumors were found within corresponding colon tissue samples examined at gross necropsy in the same area. T₂ values were significantly different between tumor, skeletal muscle, and normal intestinal wall tissues (p <.05). For analysis of the vascular characteristics of colon tumor tissues using DCE measurements, the initial area under the curve (IAUC) for Gd contrast concentration curve (time) (CGd [t]) was calculated with integration times of 60 and 120 seconds post-contrast infusion; two integration times were selected to capture both tracer wash-in and wash-out characteristics. IAUC measurements were significantly larger in tumor tissues compared to both normal intestinal wall and skeletal muscle tissues (p <.001). In vivo anatomic and quantitative MRI measurements were readily feasible in the transgenic APC^δ468 mouse model. These noninvasive methods should improve experimental efficiencies during longitudinal survival studies that otherwise would require single-end-point necropsy measurements.