The Structural And Functional MRI Study Of Hippocampus In Patients With AD

Hippocampus is an essential organ of the central nerve system.Hippocampus is necessary in working memory for the human being.Hippocampal pathology did lead to cognitive and psychological impairment.Fornix is the predominant outflow tract from the hippocampus,and alterations to its microstructure in patients with AD are still being explored.Taking advantage of MPRAGE,DWI images,DTI images,SWI images,we analyzed and compared the diffusion features of hippocampus,macrostructural integrity of hippocampus-fornix fiber tracts,diffusion features of fornix and morphological features of hippocampal veins in patients of AD.First,we acquired Twenty-five probable AD participants and twenty-five ageand education-matched health controls Head MPRAGE and DTI images in a 3 Tesla scanner.The hippocampus-fornix fibers were tracked and ADC and FA values were obtained from DTI.The MTA scale was acquired from coronal MPRAGE images.MMSE scores were completed by one neuropsychologist.All the data were compared and analyzed using 3D NEURO Workstation.P values less than 0.05 were considered to be statistically significant.And we found that compared with the normal group,AD group left and right HFFs morphology(both p<0.05),bilateral hippocampal average ADC(both p<0.05),and left hippocampal average FA(p<0.05)revealed significant difference.Left hippocampal FA significantly correlated with left hippocampal ADC(p<0.05,r =-0.522)in normal group,and with MMSE(p<0.05,r = 0.597)in AD group.Left HFFs and right HFFs presented general linear relationships in normal group(r =0.865,p<0.05),and in AD group(r = 0.611,p<0.05).The MTA scales showed significant difference(p<0.05)between the two groups.No difference was found form left vs.right HFFs morphology scales,left vs.right hippocampal ADC,left vs.right hippocampal FA in normal and probable AD groups.Moreover,DTI was used to assess and analyze the microstructural features of the fornix in subjects with AD(n = 17),mild cognitive impairment(MCI;n = 12)and healthy controls(n = 17).DTI was performed using Explore DTI software and the FSL package.Within the fornix,patients with AD showed decreased fractional anisotropy values(p<0.05)and length of fiber tracts(p<0.05)of the fornix relative to healthy controls,but higher mean diffusivity values(p<0.05).MCI subjects showed a trend towards elevated mean diffusivity values in the fornix.We also acquired the high-resolution 3D MPRAGE and SWI imaging form 16 AD patients and 16 HC on 3 Tesla SIEMENS system equipped with a 32 channel head coil.The hippocampal volume and morphological manifestations of veins in the hippocampal regions were measured and graded on the 3D MPRAGE imaging and SWI imaging,respectively.And we also measured the MMSE scores and Mo CA scores for all the subjects.We found hippocampal volumetry(P < 0.05,morphological manifestation scores of hippocampal regional veins(left,P < 0.05;right,P < 0.05),MMSE scores(P < 0.05)and Mo CA scores(P < 0.05)decreased significantly in patients with AD.The average ADC value of the right hippocampus increased significantly in AD(P < 0.05).In AD group,there were significantly positive correlations between LHV and RHV,between MMSE and Mo CA,Edu.,between Mo CA and LADC,between LADC and RADC(all P < 0.05).Between MMSE and LADC,Mo CA and LADC,Edu.and LADC showed significantly negative correlations in AD group(all P < 0.05).We also found that between LHvein and RHvein,between LHvein and Mo CA,between RHvein and Mo CA showed significantly positive associations in HC group(all P < 0.05).According to all the above results,we found that hippocampal atrophy and abnormal diffusion features of hippocampus,abnormal macro-structural integrity of hippocampus-fornix fiber tracts,abnormal diffusion features of hippocampus-fornix and abnormal morphological features of hippocampus veins in patients with AD.And MMSE scores and Mo CA scores relative to some imaging indicators in patients with AD,but this kind of relationships need further confirmation.We confirmed that hippocampal volume,hippocampus-fornix fiber tracts,diffusion features of hippocampus-fornix and morphological features of hippocampus veins could be used as imaging indicators in the protocols of diagnosis and assessment for AD.