MONITORING EARLY RADIATION-INDUCED LIVER INJURY USING FERUCARBOTRAN-ENHANCED MRI AT 3 T: AN ANIMAL MODEL

The aim of this study was to find the time window for monitoring early radiation-induced liver injury (RILI) of rats using ferucarbotran-enhanced magnetic resonance imaging (MRI) at 3 T. Six rats were irradiated with 20 Gy 6 MV X-ray on right side liver and the other six non-irradiated rats were used as the control. Three or four days after irradiation, the rats were examined using MRI. The conventional spin echo (CSE) pulse sequence with various scanning parameters (CSE1: TR/TE = 200/8 ms, CSE2: TR/TE = 1000/8 ms and CSE3: TR/TE = 1000/22 ms) was performed before, 20 min, 1 h, 7 days, 14 days and 21 days after injecting 80 μmol/kg ferucarbotran, a kind of commercialized superparamagnetic iron oxide (SPIO). The ferucarbotran particles were macrophaged by Kupffer cells and this caused decreased signal intensity on MR images because of the T2and susceptibility effect. The irradiated liver had less reduction of MR signal intensity than the non-irradiated liver because radiation impaired the function of Kupffer cells. All CSE images of the irradiated group showed higher right-to-left ratio of the MR signal intensity in the liver than the control group after ferucarbotran injection. Furthermore, CSE2 demonstrated higher efficacy than CSE1 and CSE3. The optimal time window to observe an obvious contrast between the right side and left side liver in the irradiated group was from 20 min to 7 days after a single bolus injection of ferucarbotran. This protocol may be helpful to investigate the effects of radioprotectors and radiosensitizers on the reticuloendothelial system.