The DTI Study Of White Matter In Human Brains Of Normal Adults And Hypertensive Patients

Objective: To evaluate the diffusion anisotropic properties of white matter of human brain in normal adults and hypertensive patiens. To explore the evaluation of DTI in demonstrating the microstructure and FA value in quantifying the different diffusion properties of white matter in these groups.Methods: 61 healthy volunteers and 60 elderly subjects at our hospital underwent conventional MRI, DWI and DTI covering a period from Sep 2003 to Dec 2004. All subjects were divided into six groups by gender, age and hypertensive conditions. 61 healhy volunteers(20³0y )were divided into two groups by gender: group 1, male, (21³0)y, 30 subjects; group 2, female, (22²9)y, 31 subjects. Group 3 and group 4 were divided by ages: Group 3, (23²9)y, 30 subjects; group 4, (60⁷6)y, 30 subjects. Group 5 and group 6 were divided by hypertensive conditions : Group 5, normotensive group, (60⁷6) y, 30 subjects; hypertensive group, (60⁷8)y, 30 subjects. The subjects of group 1,2, 3, 4, 5 had no neurological or other systemic disease history and no positive findings on conventional MRI. Hypertension was defined as a systolic blood pressure of ≥140mmHg or a diastolic blood pressure of ≥90mmHg or both, with or without the use of antihypertension treatment. Group 6 had no neurological or other systemic disease history. DTI was performed using single shot SE-EPI sequence . The b value was 1000 s· mm^-2. The diffusion was measured along 13 directions. FA (fractional anisotropy) was measured in genu and splenium of corpus callosum, the knee and posterior limb of internal capsule, corona radiata, optic radiations, frontal and occipital white matter, thalamus respectively. Statisticalanalysis was performed.Results: (1) Group 1 and group 2: Increased anisotropy was presented in the male group in both genu and splenium of corpus callosum, the knee of internal capsule in comparison to females. The mean FA value of males was (0.72 ± 0.04) and females was (0.70 ± 0.05)in genu of corpus callosum. The mean FA value of males was (0.72 ± 0.05) and females was (0.70 ± 0.05) in splenium of corpus callosum. The difference of mean FA value between male and female groups in genu and splenium of corpus callosum was statistically significant(P<0.05). The mean FA of males was (0.64±0.04) and females was (0.62+0.04) in the knee of internal capsule. The difference of FA value in the knee of internal capsule between male and female groups was statistically significant (P<0.05)o(2) Group 3 and group 4: The FA value of young group in genu and splenium of corpus callosum, the knee and posterior limb of internal capsule, optic radiations, corona radiata, frontal and occipital white matter, thalamus was (0.71 ±0.04) ,(0.7110.04) , (0.62±0.03) , (0.63±0.03) ,(0.51 ±0.08),(0.52±0.06),(0.43±0.07), ( 0.44±0.07), ( 0.26±0.03) respectively. The FA value of older group in genu and splenium of corpus callosum, the knee and posterior limb of internal capsule, optic radiations, corona radiata, frontal and occipital white matter, thalamus was(0.65±0.08) , (0.67±0.09) , (0.61±0.05) , (0.63+0.04) , (0.47+0.05) , (0.51+0.07), (0.38±0.05), (0.39±0.06 ), (0.27±0.04)respectively. A significant FA decline of older group in genu and splenium of corpus callosum, optic radiations, frontal and occipital white matter was found (PO.05). There was no significant difference of FA value between the left and right hemisphere(P>0.05).(3) Group 5 and group 6: The mean FA value in optic radiations of hypertensive group was (0.44±0.06). A significant FA decline was presented in hypertensive group in optic radiation when compared to normotensive groupCP-^O.OS). The mean FA value of normotensive group in genu and splenium of corpus callosum, the knee and posterior limb of internal capsule, corona radiata, frontal and occipital white matter,thalamus was (0.65+0.08), (0.67±0.09), (0.61±0.05), (0.63±0.04), (0.51+0.07), (0.38±0.05), (0.39±0.06), (0.27±0.04) and hypertensive groups was (0.65±0.05),(0.69±0.06> (0.61±0.06), (0.63±0.04), (0.50±0.08) , (0.39±0.06), (0.41±0.06) , (0.28±0.03 ) respectively. No significant difference was observed between these twogroups(P>0.05).Conclusion: Our findings provide evidence for sex and age difference in normal adults via DTI. There was significant difference of FA value in optic radiation between normotensive and hypertensive elderly. DTI is valuable in assessing the directionality and density of white matter and can reflect the sex and age-related physiological changes and pathological status of white matter in vivo non- invasively. FA value permits the quantification of the directionality and coherence of white matter of human brain in normal and abnormal adults.