Application Value Of Intravoxel Incoherent Motion Diffusion On MR For Evaluating Radiation-induced Salivary Gland Injury In SD Rat

Objective: To assess the feasibility of intravoxel incoherent motion(IVIM)on MR for evaluating radiation-induced salivary injury.Methods: 12 rats were divided into blank control group(0Gy),experimental group A(15Gy)and experimental group B(20Gy)according to different radiation dose.All the rats were performed MR-IVIM scan and collected saliva at three time points including pre-irradiation,4weeks and 8weeks post-irradiation.The IVIM parameters(D value?D* value?fraction value)in submandibular glands areas were measured and the salivary flow rate of every rat were calculated.Changes of salivary flow rate and IVIM parameters at different time points in three groups were compared respectively in use of repetitive measurement and analysis of variance.Correlations between IVIM parameters and salivary flow rate were investigated.Results:(1)salivary flow rate: Changes of salivary flow rate in control group at pre-irradiation,4 weeks post-irradiation and 8 weeks post-irradiation were negative(P=0.775).There was a significant decrease of salivary flow rate at 4 weeks post-irradiation(P=0.047,P<0.001,respectively)and an insignificant increase of salivary flow rate at 8weeks post-irradiation in experimental groups(P>0.05).But no significant difference was observed between experimental group A and B.(2)IVIM parameters: Changes of D value,D* value and fraction in control group at pre-irradiation,4 weeks post-irradiation and 8 weeks post-irradiation were all negative(all P>0.05).There was a significant decrease of D value at 4 weeks post-irradiation in experimental groups(P <0.001).Fraction was increased at 4 weeks post-irradiation and 8 weeks post-irradiation(P=0.027;P=0.042,respectively),while D* value was no change at different time points(P>0.05).No significant difference of was observed between experimental group A and B(all P>0.05).(3)correlation: The salivary flow rate and D value were showed a positive correlation(P=0.011,r=0.532)and no correlation was found with D* value and fraction.Conclusion: MR-IVIM may be an important noninvasive and quantitative technology of evaluating radiation-induced salivary injury.