The Study Of ~1H-MRS And DTI On Radiation Injury Of Temporal Lobes In Nasopharyngeal Carcinoma After Radiotherapy

Objective:1.To explore the value of ¹H-MRS and DTI in detecting temporal lobes radiation brain injury in nasopharyngeal carcinoma after radiotherapy.2.To investigate the ¹H-MRS and DTI imaging changes of temporal lobe radiation brain injury in nasopharyngeal carcinoma after radiotherapy with compare to control group of normal;Through analyze the radiation brain injury in ¹H-MRS and DTI imaging changes of nasopharyngeal carcinoma patients after radiotherapy in different stages,to investigate the value of ¹H-MRS and DTI in monitoring radiation brain injury in the long-term follow-up after radiotherapy.Methods:Conventional MRI（T1WI、T2WI、FLAIR）and enhanced scan,1H-MRS and DTI were performed in 52 cases of nasopharyngeal patient confirmed by pathology after the first radiotherapy（radiotherapy group）and 24 healthy controls（control group）at the same time.The ratio of the NAA/Cho、NAA/Cr、Cho/Cr and the value of ADC、FA were measured.Then compared and analyzed whether the difference between the radiotherapy group and control group was statistically significant.52 cases of nasopharyngeal patients after the radiotherapy were divided into 4 groups further.The groups as following:the time after the radiotherapy less than 3months were group1;3 to 6 months were group 2;6 to 12 months were group 3;more than 12 months after the radiotherapy were group 4.Observed the dynamic changes of the ratio of metabolites and the value of FA,ADC as time passed.Results:1.There were no statistically significant differences in the control group and the radiotherapy group with regard to age（t=0.190,P=0.850）and gender（χ²=0.501,P=0.479）.There were no change of abnormal signal in the temporal lobes of the radiotherapy group and normal control group with conventional MRI and contrast enhancement scan sequence.2.¹H-MRS imaging results:the NAA/Cho ratio of control group was 1.508±0.419,NAA/Cr ratio was 1.840±0.591,Cho/Cr ratio was 1.488±0.515.While the NAA/Cho ratio of radiotherapy group was 1.117±0.385,NAA/Cr ratio was1.513±0.507,Cho/Cr ratio was1.319±0.505.Compared with the control group,there was a decrease in the metabolites ratio of radiotherapy group in different extent.The differences of NAA/Cho and NAA/Cr ratios between radiotherapy group and control group were statistically significant（P<0.05）,while Cho/Cr ratio was no statistically difference（P=0.063）.Radiotherapy group was divided to 4 groups according to the time after radiotherapy,each group NAA/Cho ratio were 1.236±0.511、1.092±0.382、1.201±0.119 and 1.279±0.235 respectively.The NAA/Cho ratio of 4 groups after radiotherapy were all decreased compared to control group,and the differences between group2-4 and control group were significant statistically.The NAA/Cr ratio of 4 groups were 1.442±0.525、1.588±0.574、1.598±0.402、1.656±0.438 respectively.The NAA/Cr ratio of 4groups were decreased compared to control group,and the differences between them were significant statistically.The Cho/Cr ratio of 4 groups after radiotherapy were 1.167±0.274、1.450±0.633、1.331±0.461、1.295±0.399respectively.The Cho/Cr ratio of group 1 after radiotherapy was lower than the control group and the difference was statistically significant,while the rest has no significant differences by two-two comparison.3.DTI imaging results:the FA value of control group and radiotherapy group were 0.492±0.046 and0.461±0.051 respectively,the FA value of radiotherapy group was lower than control group,and the difference was statistically significant.（t=3.665,P<0.01）.The FA value of 4groups were 0.470±0.035、0.452±0.068、0.455±0.046、0.464±0.039 respectively.The diversity of FA value between the groups with the one-way ANOVA was presented（F=3.971,P=0.004）.All the values were compared in pairs:the FA value of group1、group2、group3were all lower than the control group,and the differences were statistically significant（P<0.05）.However,there were no statistically significant differences between the rest groups through paired-comparisons method.The FA value of group4 was increased than group2 and group3,but still slightly lower than the control group.Compared with the control group,the FA value of3～6 months group after radiotherapy dropped to the lowest,then increased again 6 months later as the time goes on.The ADC value of control group was0.944±0.107×10^-3mm²/s,the ADC value of radiotherapy group was0.899±0.055×10^-3mm²/s,and the difference was statistically significant（t=2.764,P=0.008）.The ADC value of 4 groups after radiotherapy were 0.901±0.048×10^-3mm²/s、0.886±0.069×10^-3mm²/s、0.906±0.048×10^-3mm²/s、0.919±0.018×10^-3mm²/s respectively.The diversity of ADC value between them with the one-way ANOVA was presented（P=0.013）.All the values were compared in pairs:there was statistically significant differences between group2 after radiotherapy and control group,while the rest has no significant differences by two-two comparison.Compared with the control group,the ADC value of 3～6 months group after radiotherapy dropped to the lowest,then increased again 6 months later as the time goes on.Conclusion:¹H-MRS and DTI are more sensitive than the conventional MRI to check out the radiation brain injury of nasopharyngeal carcinoma after radiotherapy.They can observe the incidence and development process dynamically of the radiation brain injury in nasopharyngeal carcinoma after radiotherapy.They are the effective methods to monitor the presence of radiation brain injury in long-term follow-up after radiotherapy for nasopharyngeal carcinoma.