量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Significance:Electron Paramagnetic Resonance imaging (EPRI) is a powerful technique capable of generating images of tissue oxygenation using exogenous paramagnetic probes such as trityl radicals and nitroxyl radicals. Using principles similar to Magnetic Resonance Imaging (MRI) with field gradients, the spatial distribution of the paramagnetic probecan be generated and from its spectral features, spatial maps of oxygen can be obtained from live objects. In this review, the two methods of signal acquisition, image formation/reconstruction will be described. The probes used and its application to study tumor physiology and monitor treatment response with chemotherapy drugs in mouse models of human cancer will be summarized.
Recent Advances: By implementing phase encoding/Fourier reconstruction in EPRI in time-domain mode, the frequency contribution to the spatial resolution was avoided and improved images can be obtained. The highresolution EPRI revealed the pO2 change in tumor, which was useful to detect and evaluate the effects of various antitumor therapies. The coregistration with other imaging modalities provided a better understanding of hypoxia related alteration in physiology.
Critical Issues: The high power of EPR irradiation and toxicity profile of radical probes are the main obstacles for clinical application. The improvement of pulse sequence may lower the risk.
Future Directions:Pulsed EPR oximetry will be a powerfultool to research various disease involving hypoxia such as cancer, ischemic heart diseases, stroke, and diabetes. By optimizing radical probes, it can also be applied for various other purposes such as detecting local acid-base balance or oxidative stress.
Pulsed electron paramagnetic resonance imaging: Applications in the studies of tumor physiology
