The redox active MRI contrast agent Fe-PyC3A is shown to provide strong, selective contrast enhancement of acutely inflamed pancreatic tissue in a murine model. Fe-PyC3A is administered in the weakly contrasting Fe(2+) oxidation state but is converted to the 15-fold more strongly contrasting Fe(3+) state in the presence of reactive oxygen species (ROS). Fe-PyC3A does not provide contrast enhancement of normal pancreas, but provides significant contrast enhancement of inflamed pancreas. Pancreatic enhancement correlates tightly with activity levels of the pro-inflammatory biomarker myeloperoxidase. This is the first example of using metal ion redox for MR imaging of pathologic change in vivo.