The Value Of MR-DWI And T1 Mapping On Predicting Radiation Induced Soft Tissue Fibrosis And Its Molecular Basis

Objective:To investigate the value of MR-DWI?Magnetic Resonance Diffusion Weighted Imaging?and T1 mapping on early prediction of radiation induced soft tissue fibrosis and its molecular basis.Methods:?1?Thirty mice of C57BL/6 were randomly divided into control group?group NOR?,irradiation group?group IR?and irradiation plus glycyrrhetinic acid group?group GA?.The right hind limbs of the mice of group IR and group GA were received a single dose of 30 Gy irradiation with 6MV X-rays.MRI was performed before irradiation and on the 7th day after irradiation,and the apparent diffusion coefficient?ADC?value and longitudinal relaxation time?T1?value of the hind limb muscles of mice were measured.The hind limb contracture level was measured on the90th day after irradiation,and HE staining and masson staining were performed for the right hind leg thigh muscles.The expression level of a-SMA and Fibronectin was analyzed by immunohistochemical staining and Western blot test??2?Another 30 mice were divided into four groups as before.On the 7th day after irradiation,the ADC values and T1 values of thigh muscles in the right hind limbs wered measured by MRI?Mice wered sacrificed immediately after The MRI scanning,the expression levels of IL-1?,IL-6,TNF-a and TGF-?1 of right hind limb thigh muscles were analyzed by ELISA method.Results:?1?There were no significant difference in the ADC value and T1 value of the right hind leg thigh muscles among the three groups before irradiation.?2?On the 7th day after irradiation,the ADC values of right hind leg thigh muscle in group NOR,group IR and group GA were:?1.35±0.11?×10^-3mm²/s,?1.48±0.07?×10^-3mm²/s,?1.36±0.13?×10^-3mm²/s respectively,There were significant differences between the ADC values of group NOR?P=0.008?,group GA?P=0.013?and them of group IR,And the T1 values of them were:?1369.7±62.7?ms,?1483.7±127.7?ms and?1304.1±82.3?ms respectively,There were significant differences between the T1values of group NOR?P=0.012?,group GA?P<0.001?and them of group IR.?3?The lengths of contracture of the right hind limb in the three groups of mice on the 90th day after irradiation were?0.00±0.07?cm,?2.08±0.32?cm and?1.49±0.70?cm respectively,There were significant differences between the T1 values of the lengths of contracture of the right hind limb between group NOR?P<0.001?,group GA?P=0.030?and group IR.There were certain correlation between the ADC values?r=0.379,P=0.039??T1 values?r=0.377,P=0.040?,which were measured on the 7day after irradiation,and the length of contracture on the 90th day after irradiation.?4?The average optical density values from masson staining of group NOR,group IR and group GA were 0.003±0.002,0.071±0.056 and 0.011±0.008,respectively.There were significant differences between average optical density values of group NOR?P=0.031?,group GA?P=0.046?and group IR.?5?Immunohistochemical method:The mean optical density values of a-SMA in group NOR,group IR and group GA were:0.003±0.001,0.013±0.006 and 0.007±0.002,respectively.There were significant differences between average optical density values of group NOR?P<0.001?,group GA?P=0.009?and group IR.The mean optical density values of Fribronectin of the three groups were 0.001±0.000,0.013±0.007 and 0.004±0.003,respectively.There were significant differences between average optical density values of group NOR?P=0.011?,group GA?P=0.027?and group IR.Western blot analysis showed that the mean optical density values of a-SMA relative to the internal reference of the group NOR,the group IR and the group GA were 0.537±0.095,1.271±0.236 and0.666±0.157,respectively,There were significant differences between average optical density values of group NOR?P<0.001?,group GA?P=0.001?and group IR.The mean optical density values of the three groups in Fibronectin relative to the respective internal reference were:0.078±0.013,1.521±0.376 and 0.269±0.226,respectively.There were significant differences between average optical density values of group NOR?P<0.0001?,group GA?P=0.0001?and group IR.?6?On the 7th day after irradiation,the expression levels of IL-1?in the right hind limb thigh muscle of group NOR,group IR and group GA were?422.1±66.5?pg/mg,?766.1±150.2?pg/mg and?569.7±97.6?,respectively.There were significant differences between IL-1?of group NOR?P<0.0001?,group GA?P=0.001?and group IR.The expression levels of IL-6 were?153.8±39.1?pg/mg,?261.9±45.8?pg/mg and?147.0±39.8?pg/mg,respectively,There were significant differences between IL-6 of group NOR?P<0.0001?,group GA?P<0.0001?and group IR.The expression levels of TNF-a were?145.8±35.6?pg/mg,?192.8±45.5?pg/mg and?113.6±25.7?pg/mg,respectively,There were significant differences between TNF-a of group NOR?P=0.019?,group GA?P<0.001?and group IR.The expression levels of TGF-?1 were?1804.6±496.0?pg/mg,?2176.0±617.8?pg/mg and?1965.0±541.9?pg/mg,respectively.There were no significant difference among the three groups.?7?Correlation between ADC?T1 values and inflammatory factors:ADC values were positively correlated with IL-6?r=0.553,P=0.002?,and not significantly correlated with IL-1?,TNF-a and TGF-?1.there were positive correlation between T1 value and IL-1??r=0.419,P=0.021?,IL-6?r=0.535,P=0.002?and TNF-a?r=0.540,P=0.002?,and was not significant correlation with TGF-?1?r=0.155,P=0.413?.Conclusion:?1?MR-DWI and T1mapping can detect early changes of local soft tissue after being irradiated;?2?There are certain relationships between the degree of contraction of radiation induced fibrosis in the late stage and ADC value and T1 value of soft tissue in the early stage after irradiating;?3?ADC value and T1 value were found significant elevation after irradiating in the early stage after irradiating,which may be related to the rising of the inflammatory factors.