MR Resting State Study Of Cognitive Impairment In Patients With Nasopharyngeal Carcinoma Late Stage Post-radiotherapy

Objective: Up to now,the neurophysiological effects of radiotherapy on nasopharyngeal carcinoma(NPC)patients are not clear.In recent years,some scholars believe that it may be related to the abnormal connection of the brain networks.However,most scholars used the method of presupposing seed points based on prior experience to study the brain network connectivity of NPC patients,and the results are susceptible to human interference.Independent component analysis(ICA)is a datadriven brain network analysis method,which is not affected by human factors.Therefore,this study uses ICA to explore the changes in the functional connectivity of the whole brain in patients with NPC in late stage(>6 months)after radiotherapy and its relationship with changes in radiation dose and cognitive level.Methods and Materials: 60 subjects were included in this study.After radiotherapy,30 NPC patients(male 20,female 10,30-73 years,education period is 6-16 years)were included in experimental group.According to the 8th edition of AJCC,the tumor stage was T1N0M0-Ta N2M0,and the follow-up time was 6-48 months.30 cases(male 17,female 13,aged 33-73 years,being educated for 9-16 years)were enrolled in the control group.The cognitive function of the subjects were measured with the Montreal Cognitive Assessment(Mo CA)Scale(Beijing version).According to the radiotherapy plan,the patient’s bilateral temporal lobe radiation doses were counted in the case group.The resting functional magnetic resonance data were obtained using a 3.0T GE MRscanner and an 8-channel cranial coil.First,conventional T1 WI and T2 WI scans were performed to exclude diseases related to brain tissue changes,and then Sag 3D BRAVO and BOLD f MRI scans were performed.During the scanning,all the subjects were told to stay still,close their eyes,neither to consciously think nor to fall asleep.Gender differences were tested using the Chi-square test,and data on age,years of education,and cognitive rating scales were tested using the independent samples t-test,setting P<0.05 differences to be statistically significant.The DPABI software package of Matlab2012 platform was used for data preprocessing.The independent component statistical analysis was carried out using GIFT software,and the independent brain network was automatically calculated and extracted in a data-driven manner.The change of functional connectivity(FC)within and between networks in the case group and the control group was analyzed using spm8 software.First,two groups of single-sample t-tests were performed,and then independent sample t-tests were performed between the two groups.The brain regions with statistical differences in the two groups of networks were extracted by the rest software package and the average z value of these brain regions was calculated.The resting functional network connection with statistical difference between networks was obtained by independent sample t-test.Finally,Pearson correlation analysis was used in SPSS to extract the average z value of nodes within and between the network with statistical differences,and the scores of Mo CA scale and the radiation dose of bilateral temporal lobe.Results: Compared with healthy controls,the Mo CA score of NPC group was significantly lower,and the visual space,executive ability and delayed recall function were lower(P<0.05).In NPC group,the functional connectivity of three nodes in the network decreased,respectively,the right insular lobe of insular network,the left cerebelum crus II of cerebellar network and the right cuneus of posterior visual network.The change of FC in the right insular lobe was significantly correlated with Mo CA score and was dose dependent.There were 4 pairs of abnormal functional connections between the networks of NPC group: the functional connection between the anterior default mode network and the salience network decreased,the functional connection between the left executive control network and the posterior visual network decreased,the functional connection between the left executive control network and the insular network increased,and the functional connection between the salience network and the sensorimotor network increased.Moreover,the FC change between the left executive control network and the insular network was positively correlated with the radiation dose.Conclusion: After radiotherapy,NPC patients may experience cognitive impairment,which is related to radiotherapy,especially in terms of visual space,executive function and delayed memory.In patients with NPC late stage postradiotherapy,functional connectivity changes occurred in and between multiple brain area networks after radiotherapy,and functional connectivity changes in the right insular lobe were dose dependent.These abnormal connectivity changes may be potential biomarkers for patients with visual impairment,memory deficiency,and cognitive disorder after radiotherapy,while the increase of brain functional connectivity may indicate the compensatory response of the body.In brain tissue with normal conventional MR images,abnormalities in functional connectivity can be detected using MR resting-state functional brain imaging,and the independent component analysis method can reveal changes in brain function beyond the scope of radiotherapy.