Study On Diffusion Tensor Imaging In Healthy Human Brain And Cerebral Ischemia Disease

Part I: Study MR-DTI parameters of the brain structure in healthy right-handed young subjectsObjective: To quantitatively analysis the diffusion tensor imaging parameter maps of the brain structure in healthy right-handed young subjects. Methods: All volunteers approval and informed consent were obtained. 30 healthy right-handed young volunteers (sixteen men,fourteen women;mean age 28.2 years) underwent diffusion tensor imaging (DTI) and conventional MRI with a GE 3.0T magnetic resonance system.The fractional anisotropy (FA) and mean diffusivity (MD) were determined at thirteen parts of the brain:pons, cerebral peduncle, anterior limb of internal capsule,genu of internal capsule, posterior limb of internal capsule, centrum semiovale, gyrus rectus fiber, splenium of corpus callosum, genu of corpus callosum,body of corpus callosum, dorsal thalamus, lenticular nucleus, lateral cerebral ventricle.For FA and MD, the gender , lateral and regional differences of the parameter values were analyzed.Results:①The FA value of projection fibers in the left pons was superior to the right, P=0.011,whereas the MD values in gyrus rectus fiber was right superior to the left, P=0.029.②Significant difference in FA due to gender were found in the genu of corpus callosum, P=0.020.③The order of MD is: lateral cerebral ventricle>cerebral peduncle, genu of corpus callosum>gyrus rectus fiber,body of corpus callosum, anterior limb of internal capsule,dorsal thalamus>genu of internal capsule, splenium of corpus callosum, pons, lenticular nucleus posterior limb of internal capsule, centrum semiovale.FA: splenium of corpus callosum > genu of corpus callosum >body of corpus callosum, cerebral peduncle >posterior limb of internal capsule > genu of internal capsule>anterior limb of internal capsule,pons > gyrus rectus fiber,centrum semiovale >dorsal thalamus>enticular nucleus,lateral cerebral ventricle.④The normal reference values of FA and MD in 13 structures were acquared.Conclusion: FA and MD are different parameters which reflect different different aspects of the water molecule diffusion. There are sex differences of FA in the genu of corpus callosum and lateral difference both in the pons of FA and in the gyrus rectus fiber of MD. Regional differences are found significant both in MD and FA.Part II: Analysis MR-DTI parameter T2-weighted trace map in healthy right-handed young humanObjective: To investigate the manifestation of DTI T2-weighted trace parameter map in healthy right-handed young human brain.Methods: 30 healthy right-handed young volunteers(sixteen men,fourteen women;mean age 28.2 years) underwent diffusion tensor imaging and conventional MRI with a GE 3.0T magnetic resonance system. Three DTI parameters T2-weighted trace, fractional anisotropy (FA) and mean diffusivity (MD) were determined. Observe the manifestations of T2-weighted trace maps at 13 sites and compare them to FA and MD. Include: pons, cerebral peduncle, anterior limb of internal capsule,genu of internal capsule, posterior limb of internal capsule, centrum semiovale, gyrus rectus fiber, splenium of corpus callosum, genu of corpus callosum,body of corpus callosum, dorsal thalamus, lenticular nucleus, lateral cerebral ventricle.Results: In healthy right-handed young human brain, the value of T2-weighted trace had a large variance among individues and had a left-right asymmetries in pons, cerebral, anterior internal capsual, centrum seimioval and lenticular nucleus, P=0.000-0.017. T2-weighted trace, In places where CSF accumulates MD is high whereas T2-weighted trace and FA are lowest. FA were lowest and MD was highest in lateral cerebral ventricles, sulcus and cistern. Lower T2-weighted trace was found at lenticular nucleus, substantia nigra and red nucleus. The T2-weighted trace parameter mean value and 95% confidence interval in 13 brain structures were calculated.Conclusion: T2-weighted trace is a different diffusion parameter from FA and MD. The values of young human brain are large variance among individues and had hemispheric asymmetries. T2-weighted trace map can clearly display the lenticular nucleus, substantia nigra and red nucleus. There are negative correlation between T2-weighted trace and MD.Part III: Investigate the correlation between MR-DTI parameter and age in healthy brain structureObjective: To investigate the relationship between three DTI parameter map with age in brain of healthy middle and old subjects.Methods: Select 28 middle and oldhealthy right-handed subjects ( 41-76 years ) and 30 sex-matched young volunteers. All subjects underwent diffusion tensor imaging and conventional MRI with a GE 3.0T magnetic resonance system. Three DTI parameters T2-weighted trace, fractional anisotropy (FA) and mean diffusivity (MD) were determined. Observe the manifestations of three diffusion parameter maps at 12 brain structure and measured the value of them. ROI (region of interest ) at: pons, cerebral peduncle, anterior limb of internal capsule,genu of internal capsule, posterior limb of internal capsule, centrum semiovale, gyrus rectus fiber, splenium of corpus callosum, genu of corpus callosum,body of corpus callosum, dorsal thalamus, lenticular nucleus, lateral cerebral ventricle. Analysis the difference of the three parameter values between left-right lateral and among regions of the projection fibers, analysis the difference between the two age groups. Assess the relationship between three parameter values and age.Results: For the middle-old age group, the order of FA, MD, T2-weightedtrace were the same as young group. In the former, there were no sex-difference for three parameters in all 12 brain structure. Lateral analysis: FA value of lenticular nucleus, right >left, t =-2.667,P = 0.012. MD value of gyrus rectus fiber right >left, t = -3.190,P = 0.004. T2-weighted trace value, centrum seimioval, left > right, t=2.14,P=0.042. Comparison to young group: T2-weighted trace of all the 12 sites, the middle-old age group was lower than the young group. For T2-weighted trace: significant negative correlation with age in pons, anterior limb of internal capsule and lenticular nucleus were tested, r = -0.560– 0.275,P = 0.000– 0.037.Conclusion: In middle-old age group, all three diffusion parameters (FA, MD, T2-weighted trace), hand no sex-difference in the 12 brain structure. T2-weighted trace in middle-old age group is more symmetry. All the values of T2-weighted trace are lower than the young. Statistical differences appear in pons, anterior limb of internal capsule and lenticular nucleus. T2-weighted trace and age have significant negative correlation.PartⅣ: MR-DTI parameters exploratory development in ischemic cerebrovascular diseaseObjective: Explore the clinical application value of three DTI parameters in different type of ischemic cerebrovasular disease.Methods: Clinical data, conventional MRI, and DWI data were collected on 18 with clinical diagnosed ischemic cerebrovascular disease. 13 Male and 5 female patients, age range 19-71years old ( mean age 46.8±12.6 years old ). 3 with TIA ( transient ischemic attack ), 4 with hemorrhagic transformation ( HT ) and 11 with non-hemorrhagic infarction. A follow-up DTI checking was performed using a GE 3.0 T magnetic resonance system, sixty-two number of DTIs were performed in all. Three DTI parameters T2-weighted trace, fractional anisotropy ( FA ) and mean diffusivity ( MD ) were determined. Observe the manifestations of three diffusion parameter maps in the three type of ischemic cerebrovascular disease. Assess the imaging characterization of DTI parameter map, diffusion weighted imaging ( DWI ) and conventional MRI. Measure the parameter values in ischemic lesions. Analyse the relative change among FA, MD and T2-weighted trace. Comparison were performed among DTI, DWI and conventional MRI.Results: DTI and DWI-detected acute ischemic lesions were present in 2 of 4 TIA cases. The lesions on DTI manifested: bright area in T2-weighted trace, corresponding raised or reduced FA, low or normal MD values. 3 HT lesions, lowed T2-weighted trace were observed in all the three, and for one at 9-day from hemorrhage, we observed a"black hole"on T2-weighted trace that correspond to a very high FA values, that characterization was not find in the other 2 HT patient, the reason may related to a large hemorrhage volume. In non-hemorrhagic infartions, within 3 days from the first onset, we ovserved a light to moderate rise in T2-weighted trace, and its value continue to heighten at 3-7 days from symptom onset, after that, followed a gradually decrease. In all ischemic lesions where the DWI manifested bright, the lesions on T2-weighted trace seemed more clear and larger than on the DWI and conventional MRI.Conclusions: In patients with ischemic cerebrovascular disease, DTI T2-weighted trace map can detect the responsible-ischemic lesion more clear than DWI and conventional MRI. HT on T2-weighted trace present marked manifestations. Combine use the three DTI parameter maps T2-WT, MD and FA may help judge the time from ischemia onset and predict the prognosis.