The Age-Related Changes Of Normal Adult Brain Structure And White Matter Fiber: Studied With Diffusion Tensor Imaging

[Objective] Diffusion tensor imaging is a new imaging method that can reflect the structural changes by measuring the diffusion changes of water molecules. In this study, the anisotropy and average diffusion coefficient (DCavg) of white matter fibers and gray matter nucleus of various age groups were quantified to reflect the brain microstructure changes with advancing age indirectly. Also, we reconstruct human brain fibers with fiber tracking in vivo, and discuss its consistence with known anatomy.[Materials and Methods] 106 normal adults(50 men, 56 women; age range 20-79 years; mean age 48 years) were divided into 3 groups according to their ages: younger group(20³9 years), middle age group(40⁵9 years) and older group(2s60 years). All subjects were examined with 1.5T Twin-Speed Infinity with Excite I (Signa; GE Medical System), and scaned with 8 channels head coil. The sequence included axial and sagittal T₁ FLAIR, axial and coronal T₂WI, axial diffusion-weighted imaging, and axial diffusion tensor imaging with diffusion sensitive gradients applied in 13 directions. For each subject, centrum semiovale, anterior limb, genu and posterior limb of internal capsule, genu, body and splenium of corpus callosum, the pericallosal parietal and frontal lobe, pyramidal tract, middle peduncle of cerebellum, thalamus, lentiform nucleus, and head ofcaudate nucleus were selected as regions of interest (ROIs). Fractional anisotropy(FA), 1-volume ratio(l-VR), relative anisotropy(RA) and DCavg of each ROI were measured and compared among the 3 groups, and also were correlated with the age respectively, and P value less than 0.05 was considered as statistical significance.The DTI data was transferred into computer with DICOM format, and was reconstructed with the diffusion tensor software VolumeOnel.44. [Results]l.The correlation of DTI parameters in different structures with age 1) FA, 1-VR and RA showed significant negative correlation with age in all ROIs (P<0.05 ) except in ROI of lentiform nucleus.2) The DCavg showed significant positive correlation with age in centrum semiovale, posterior limb of internal capsule, genu and splenium of corpus callosum, pericallosal frontal lobe, thalamus and head of caudate nucleus(P<0.0S ) . The correlation of DCavg with age did not reach statistical significance in anterior limb, genu of internal capsule, body of corpus callosum, pericallosal parietal lobe, middle peduncle of cerebellum and pyramidal tract(P>0.05) .3) Surprisingly, all the FA> 1-VR> RA and DCavg of lentiform nucleus showed positive correlation with age (P<0.05) .2.The comparison of DTI parameters of different structures among groups1) The comparison of anisotropy among groups? The difference of FA -. 1-VR and RA in anterior limb, posterior limb ofinternal capsule, genu, body of corpus callosum, pericallosal parietal lobe,pyramidal tract, the difference of FA in genu of internal capsule, the difference of1-VR in pericallosal frontal lobe were statistically significant among 3 groups(PO.05) , the values of the above parameters in younger groups were biggerthan that in middle age groups, the middle age groups bigger than older groups(2) The difference of FA , 1-VR and RA in centrum semiovale, splenium of corpus callosum, middle peduncle of cerebellum, thalamus and head of caudate nucleus were statistically significant among part of the groups (P<0.05) .(3) The difference of FA in lentiform nucleus between younger and older groups , middle age and older groups, the difference of 1-VR and RA between younger and older groups were statistically significant (P<0.05 ), but its trend was opposite to that in other structures, that is the values of the above parameters in older groups were bigger than that in younger groups and middle age groups.2) The comparison of DCavg among groups? The difference of DCavg in centrum semiovale, anterior limb, posterior limb of internal capsule, genu and splenium of corpus callosum, pericallosal frontal lobe, lentiform nucleus between middle age and older groups, younger and older groups, the difference of DCavg in pericallosal parietal lobe, middle peduncle of cerebellum between middle age and older groups, and the difference of DCavg in thalamus and head of caudate nucleus between younger and older groups were statistically significant (P<0.05) , the DCavg values in older groups were bigger than that in younger groups and middle age groups.?The difference of DCavg in genu of internal capsule, body of corpus callosum between younger and middle age groups, middle age and older groups were statistically significant (P<0.05) , but the DCavg values in younger groups were bigger than that in middle age groups, older groups bigger than middle age groups; the difference of DCavg in pyramidal tract between younger and middle age groups were statistically significant (PO.05) ,but the DCavg values in younger group was bigger than that in middle age group.3.In FT, the color tensor mapping showed fiber tracts trajectory with different colors, and different fibers of white matter in human brain were reconstructed...