Application Of Neurite Orientation Dispersionand Density Imaging In Evaluating The Direction Of White Matter Fiber Bundles In Elderly Patients With Postoperative Cognitive Dysfunction

Objective: To explore the abnormities of white mater in elderly patients with post-operative cognitive dysfunction(POCD)using neurite orientation dispersion and density imaging(NODDI).Methods: Participated in this 85 patients aged 70 to 85 years,scheduled for elective orthopedic,urologic,general or vascular surgeries,under general anesthesia.All the patients underwent a battery of clinical quantitative neurologic/neuropsychologic tests and NODDI MR exmination on the day before surgery(Day 0)and 7 days after surgery(Day 7).The battery encompassed the following tests: forward and backward Digit span,Digit symbol substitutions test(DSST),Trail making test(part A),Verbal fluency test and Word recognition memory test.A Z score for each individual test was calculated by comparing baseline scores(Day 0)with test results of Day 7 using the reliable change index(RCI).POCD was defined as Z scores equal to or greater than-1.96 on at least two tests and/or their combined Z score was less than –1.96.Diffusion MRI data for NODDI were acquired with a 3T MR system using 32 gradient directions with three b-values(from 0 to 2000 s/mm2).The orientation dispersion index(ODI)and intra-cellular volume fraction(Vinc)were calculated.Tract-based spatial statistics(TBSS)analyses of WM tracts were then performed.Con-images of skeletonized ODI and Vinc images(created via TBSS pipeline)were created by substracting Day 0 images from Day7 images.The con-images of POCD and non-POCD participants were compared with Permutation Test.Results: POCD was observed in 16 participants(18.9%).Compared with non-POCD participants,POCD participants exhibited differences in change of ODI in bilateral corpus callosum,cingulum,inferior longitudinal fasciculus,left superior longitudinal fasciculus and right uncinate fasciculus,however,differences in change of Vinc were found in in bilateral corpus callosum,cingulum and left inferior longitudinal fasciculus(P<0.05,TFCE corrected).Conclusion: Postoperative changes of white matter in corpus callosum,cingulum,inferior longitudinal fasciculus,superior longitudinal fasciculus and uncinate fasciculus might be associated with the onset of POCD.