Objective To detect radiation-induced changes of temporal lobe normal-appearing white matter on conventional MRI following radiation therapy (RT) for nasopharyngeal carcinoma (NPC).Methods The clinical and imaging features of 75 patients with nasopharyngeal carcinoma were retrospectively analyzed,all patients were confirmed by biopsy.All patients performed conventional MRI and Diffusion-tensor imaging (DTI) examinations,and there was no abnormal finding on conventional MRI.Eighteen patients without radiotherapy were selected as the control group and fifty-seven patients with radiotherapy were as the experimental group.We divided the experimental group into five subgroups based on completion time of RT:group 1 (less than 3 months,n =16),group 2 (3 to 6 months,n =12),group 3 (6 to 9 months; n =10),group 4 (9 to12 months,n =8),and group 5 ( more than 12 months,n =11 ).The mean diffusivity ( MD),apparent diffusion coefficient ( ADC ),fractional anisotropy ( FA),radial diffusivity ( λ⊥ ) and axial diffusivity ( k ‖ ) were calculated in bilateral temporal lobe.One-way analysis of variance (one-way ANOVA) test was used for comparison among groups.Results The mean λ⊥ values of the control group and experimental groups ( group1-5 ) after radiotherapy were ( 6.075 ± 0.341 ) × 10 -4 (6.700±0.379) × 10-4,(6.976 ±0.527) ×10-4,(6.621 ±0.388) ×10-4,(6.751 ±0.460) ×10-4,(6.222 ±0.256) × 10-4 mm2/s,respectively.The mean λ ‖ values of the control group and experimental groups were (12.524±0.713) ×10-4,(11.764 ±0.574) ×l0-4,(11.842±0.471) ×10-4,(11.569 ± 0.552) × 10-4,( 12.050 ±0.614) × 10-4,( 12.100 ±0.529) × 10-4 mm2/s,respectively.The mean FA values of the control group and experimental groups were 0.452 ± 0.030,0.379 ± 0.028,0.382 ± 0.028,0.389 ± 0.032,0.388 ± 0.022,0.423 ± 0.232,respectively.The three indicators were significantly different among groups ( F =10.485,4.625,16.539,respectively,P ＜ 0.05 ). Multiple comparisons showed that λ⊥ increased significantly in group 1-4 compared with that in the control group.In group 5,λ ⊥ was not significantly different from that in the control group,λ ‖ decreased in group 1-3 compared with that in the control group,but was not significantly different in the control group and group 4-5. In all experimental groups,FA decreased significantly. MD and ADC values in experimental groups were not significantly different from those in the control group. Conclusion Diffusion tensor imaging is a noninvasive and quantitative method to detect the structural changes in WM after RT and can provide scientific evidence for the early diagnosis and intervention treatment of radiation-induced changes.