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Medical Redox Imaging Group

Excess amount of Reactive oxygen species (ROS) generation is related to causes and development of diseases. It is thus important to scan in vivo generation of ROS in animal to investgate mechanisms of the diseases.

Several studies have demonstrated non-invasive assessment of ROS generation in small animals using low frequency electron spin resonance (ESR) spectroscopy/imaging 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 site-specific manner.

However, spatial resolution in ROS imaging with ESR is affected by linewidth of nitroxyl radicals (typically c.a. 1 gauss) and their relatively short half-life in vivo. The half-life of nitroxyl radicals in most tissues is on the order of minutes and such time window allows probing the tissue redox environment, as the experiments described above This severely limits the sensitivity of the method and spatial resolution of redox mapping using nitroxyl radicals.

In order to achieve high spatial resolution ROS imaging, a technique using magnetic resonance imaging has been developed, using Overhauser enhanced MRI (OMRI). OMRI is also known as proton electron double resonance imaging (PEDRI). OMRI is a dynamic nuclear polarization technique for imaging free radicals based on MRI. The Overhauser effect is a phenomenon of dynamic nuclear polarization, in which saturation of electron spin resonance of a free radical causes a polarized nuclear spin state. The phenomenon is specifically called nuclear Overhauser effect (nOe), when the saturation radio frequency is applied to nuclear spin resonance, which is widely used in NMR researches. OMRI creates images of free radical distributions in small animals by enhancing the water proton signal intensity via the Overhauser Effect. OMRI technique can be applied to image the ROS-dependent changes in nitroxyl radical via proton images and in higher resolution than ESR imaging. Thus it may become a powerful tool to clarify mechanisms of disease and to monitor pharmaceutical therapy.

In our group, we focused on development of OMRI scanner which is compatible to clinical application, and of new class of ROS- and organ- specific nitroxyl radicals.


Kyushu University

Kazuhiro Ichikawa Innovation Center for Medical Redox Navigation, Professor
Kiyoshi Sakai Innovation Center for Medical Redox Navigation, Research Professor
Mayumi Yamato Innovation Center for Medical Redox Navigation, Associate Professor
Kosem Nuttavut Innovation Center for Medical Redox Navigation, Assistant Professor
Yoshitsugu Tanaka Innovation Center for Medical Redox Navigation, Technical staff
Ryuma Kobayashi Innovation Center for Medical Redox Navigation, Technical staff


Deputy Director
Yukio Mizuta JEOL Ltd.
NM Application group leader

Collaboration Company