3105 - Can We Assess Acute Radiation Injury? Feasibility of Redox Imaging by Dynamic Nuclear Polarized (DNP) MRI
Presenter(s)
M. Matsuo1,2, H. Imai1,2, A. E. Elhelaly1, T. Mori1, A. Kobori1, M. Ito1, T. Mori3, H. Tomita4, and F. Hyodo5; 1Department of Radiology, Graduate School of Medicine, Gifu University, Gifu, Japan, 2Innovation Research Center for Quantum Medicine, Graduate School of Medicine, Gifu University, Gifu, Japan, 3Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan, 4Gifu University, Department of Tumor Pathology, Gifu, Japan, 5Department of Pharmacology, Graduate School of Medicine, Gifu University, Gifu, Japan
Purpose/Objective(s): It is known that radiotherapy induces oxidative stress associated with generation of reactive oxygen species (ROS) which in turn plays an important role in acute radiation injury. However, there is no efficient way to detect or predict ROS effects especially in acute radiation injury by conventional imaging modalities such as CT, MRI, and FDG-PET. In this study, we assessed ROS effects in acute radiation injury to visualize the redox reaction of the liver, heart, and intestines after irradiation noninvasively by Dynamic Nuclear Polarized (DNP) MRI.
Materials/Methods: Redox imaging by low filed type of DNP MRI and routine MR (1.5T) were performed on every four mice of the liver, heart, intestines, and control groups before and 1 hour, 1 day, 3 days, and 7 days after single-fraction doses of 10 Gy and 20 Gy to whole body using a linear accelerator at Gifu University Veterinary Hospital. After DNP MRI, Redox images were created from the ROIs of liver, heart, and intestines using ImageJ software, and the redox change rates were calculated from the decay slope of the signal intensity of the enhanced redox image in each image pixel, using spreadsheet software. Finaly, redox images and the redox change rates were compared to histopathological findings.
Results: The redox reaction in mice liver, the redox change rates were clearly enhanced just 1hr after 10 Gy and 20 Gy irradiation. The redox change rates decreased on 1 day and recovered on 7 days after irradiation (P < 0.05). In the heart group, redox images could not show the enhanced signals 1hr after 10 Gy and 20 Gy irradiation. The mice treated by 10 Gy showed a decrease in the redox change rates on 3 days, and 20 Gy showed a marked decrease in the redox change rates on 3 days and a further decrease on 7 days (P < 0.05). In the intestines group, the redox change rates were clearly enhanced just 1hr after 10 Gy and 20 Gy irradiation, and redox images were equivalent to control group on 1 day after irradiation. The redox change rates decreased on 3 days and furthermore decreased on 7 days both 10 Gy and 20 Gy irradiation. Histopathological findings showed the number of neutrophils in the hepatocytes and intestines cells increased 1 hour after irradiation suggesting that the redox reaction was activated in the whole cellular tissue.
Conclusion: This redox imaging by DNP MRI proved the possibility of detecting acute radiation injury of the liver, heart, and intestines after irradiation noninvasively. Our findings suggested that DNP MRI could monitor the ROS effects in clinical radiation treatment.