Detection And Evaluation Of Early Radiation-Induced Liver Injury In Rabbit By MRI

PURPOSE: 1) To determine the value of MR imaging with and without superparamagnetic iron oxide (SPIO)- enhanced in detection and evaluation of early radiation-induced liver injury. 2) To determine the correlation between the MRI features of early radiation-induced liver injury and its histopathologic findings. MATERIALS AND METHODS: 1) 18 rabbits were separated randomly into 3 groups. After focal irradiation (40Gy) lday, 2days and 3days, took one group of rabbits for performing the MR imaging and obtaining the specimens. Conventional MR imaging (TSE-T2WI and TSE-TiWI) and then SPIO contrast-enhanced MR imaging (TSE-T2WI and TSE-T|WI) were performed in all rabbits. The time that should take for detection of radiation-induced liver injury on each sequence was analysed. The relationship between the MR imaging features of early radiation-induced liver injury and its histopathologic findings were discussed. 2) 25 rabbits were separated randomly into 5 groups. The rabbits in different groups accepted different doses of focal irradiation (0, 10, 20, 30 and 40Gy). 3 days after irradiation, MR imaging (TSE-T2WI) and then SPIO contrast-enhanced MR imaging (TSE-T2WI) were performed in all rabbits. The minimum dose of early radiation-induced liver injury which MR imaging can detection was analysed. The evaluation of MR imaging in early radiation-induced liver injury was discussed according the correlation between the SI enhancement degrees of the irradiated portion of the liver and the number of Kupffer cells containing stained iron particles.RESULTS: 1) 2 days after irradiation, there were 2 rabbits' radiation-induced liver injuries, which were detected on IVweighted imaging enhanced by SPIO. However, 3 days after irradiation, there were 6s. The SIs of the irradiated portion of the liver were higher than the shielded portion. The margins of the irradiated portion were demarcated. Allspecimens seemed to be normal, and no evidence of edema, fibrosis, congestion, infiltration of inflammatory cells was found by light microscopy. Nevertheless, the swelling of mitochondria and vacuolization in the hypatocytes and Kupffer cells of the irradiated liver were found by the electron microscopy. The number of Kupffer cells containing stained iron particles was less in the irradiated liver than in the shielded liver in the group of 3 days after irradiation (P<0.01). 2) 3 days after irradiation, the numbers of different groups of rabbits with liver injuries which were detected on SPIO-enhanced T2-weighted imaging were as follows: l/5(10Gy), 3/5(20Gy), 5/5(30Gy), 5/5(40Gy). Significant regression was observed as a dose-related change of the SI in the irradiated portion on SPIO-enhanced T2WI imagings (P<0.01) and of the number of Kupffer cells containing stained iron particles (P<0.01).CONCLUSION: MRI SPIO-enhanced T2WI was reliable for detecting the range and extend of liver injury 3 days after irradiation.