Abstract
Magnetic Resonance Imaging (MRI) has provided significant clinical utility in the diagnosis of diseases and will become a powerful tool to assess phenotypic changes in genetically engineered animals. Several studies have demonstrated non-invasive assessment of free radical reactions and redox state in small animals using low frequency electron spin resonance (ESR) spectroscopy and nitroxyl radicals. In vivo ESR signal intensities of nitroxyl radicals decrease with time after injection; and the decreases are enhanced by ROS, generated in oxidative disease models in a site-specific manner. Overhauser enhanced MRI (OMRI), which is a double resonance technique, creates images of free radical distributions in small animals by enhancing the water proton signal intensity via the Overhauser Effect.
In this paper, we show in vivo ESR analysis of free radical reactions in various disease models and images of dual labeled nitroxyl probes by changing the external magnetic field for ESR irradiation in field-cycled OMRI, which should offer significant applicability to nanometer scale molecular imaging and simultaneous assessment of redox state in gene-modified animals. These techniques may become powerful tools to clarify mechanisms of disease and to monitor pharmaceutical therapy.
