| Objective: Using diffusion kurtosis imaging to evaluate the diffusion properties of gray matter, white mater and cerebrospinal fluid on SD rats, and discuss their age-related changes.Methods: The male SD rats were divided into five groups: 3 months, 6months, 10 months, 13 months, 24months(N=10 for each group). The 24 months rats were obtained from 3 months, which were subcutaneous injected with D-galactose at 300mg?kg-1?d-1 for 6 weeks. Using blood of eye veins, assay SOD activity and MDA content before and after injecting. The SOD activity decreaded(P<0.05) and the MDA content increased(P<0.05) are the indicators of successful model. All animals were performed conventional MRI and DKI. By drawing the regions of interest, the values of mean kurtosis(MK),axial kurtosis(K∥),radial kurtosis(K⊥),mean diffusivity(MD) and fractional anisotropy(FA) in the corpus callosum(cc), both side of the external capsule(ec), cortical gray matter(CGM), caudate putamen(CPu) and cerebrospinal fluid(CSF) were measured. Using SPSS 17.0 statistics software to evaluate the significance of left and right diffusion parameters of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid with paired-samples T-test; tested the diffusion parameters of different positions among different age groups by One-Way ANOVA and campared the values each of two different age groups by LSD-t test; analyzed the relationship of different age groups of different parts’ parameter values with Pearson or Spearman correlation and drew the estimated curves.Results:1 No laterality was found in the MK, K∥, K⊥, MD and FA values of both side of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid(P<0.05).2 The corpus callosum, both side of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid were significantly different among different age groups on the MK values(P<0.05).There were different MK values in the corpus callosum on M3-10, M3-13, M6-13, M6-24, M10-13, M10-24, M13-24; the left external capsule MK values on M3-6, M3-13, M6-13, M6-24, M10-13, M13-24; the right external capsule on M3-10, M3-13, M6-13, M6-24, M10-13, M10-24, M13-24; the left cortical gray matter MK values on M3-13, M6-13, M10-13, M13-24; the right cortical gray matter MK values on M3-10, M3-13, M6-10, M6-13, M6-24, M10-13, M10-24, M13-24; the left caudate putamen MK values on M3-6, M3-10, M6-13, M6-24, M10-13, M10-24; the right caudate putamen MK values on M3-6, M3-10, M3-13, M6-13, M6-24, M10-13, M10-24; both the left and the right cerebrospinal fluid MK values on M3-10, M3-13, M6-13, M10-13, M10-24, M13-24.There were significantly difference when compared the left cortical gray matter K∥ values of different age groups(P<0.05) on M3-13, M3-24, M6-13, M10-13, M13-24. The other parts were no difference of different age groups(P>0.05).The corpus callosum, both side of the external capsule, cortical gray matter, caudate putamen, cerebrospinal fluid were different among different age groups on the K⊥ value(P<0.05). There were different K⊥ values in the corpus callosum on M3-13, M3-24, M6-10, M6-13, M10-13, M10-24; the left external capsule K⊥ values on M3-6, M3-10, M3-13, M6-13, M6-24, M10-13, M10-24, M13-24; the right external capsule on M3-10, M3-13, M6-10, M6-13, M10-13, M10-24; the left cortical gray matter K⊥ values on M3-13, M6-13, M10-13, M13-24; the right cortical gray matter K⊥ values on M3-13, M6-13, M10-13, M10-24; the left caudate putamen K⊥ values on M3-6, M3-10, M6-13, M6-24, M10-13, M10-24; the right caudate putamen K⊥ values on M3-6, M3-10, M6-13, M6-24, M10-13, M10-24; the left cerebrospinal fluid K⊥ values on M3-13, M6-13, M10-13, M13-24; the right cerebrospinal fluid K⊥ values on M3-10, M3-13, M6-13, M6-24, M10-13, M10-24, M13-2.Both side of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid’s MD values were found significant difference among different age groups(P<0.05). The left external capsule MD values were different on M3-13, M6-13, M10-13, M13-24; The right external capsule MD values on M3-13, M6-13, M10-13, M10-24, M13-24; The left cortical gray matter on M3-13, M6-13, M10-13, M13-24; The right cortical gray matter on M3-10, M3-13, M6-13, M10-13, M10-24; The left caudate putamen on M3-6, M3-10, M6-13, M6-24, M10-13, M10-24; The right caudate putamen on M6-10, M6-13, M6-24; The left cerebrospinal fluid on M6-13, M6-24, M10-13, M10-24; The right cerebrospinal fluid on M3-24, M6-13, M6-24, M10-13, M10-24. Compared the corpus callosum’s MD values among different age groups, there were not found any difference(P>0.05).There were significant difference in both side of the external capsule, cortical gray matter and the right caudate putamen among FA values of different age groups(P<0.05).The left external capsule FA values were different on M3-13, M3-24, M6-13, M6-24, M10-13; the right external capsule FA values on M3-13, M6-13, M10-13, M13-24; the left cortical gray matter on M3-13, M3-24, M6-13, M10-13, M13-24; the right cortical gray matter on M3-10, M3-13, M6-13, M13-24; the right caudate putamen on M3-13, M6-10, M6-13, M13-24. There were no significant difference in the FA values of different age groups in the corpus callosum, the left caudate putamen and the both side of cerebrospinal fluid(P>0.05).3 There were no significant linear correlations between diffusion parameters and age in the corpus callosum, both side of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid(P>0.05). When estimated curves, all of the positions’ MK, K∥, K⊥ values and age showed “parabola” type, except the left caudate putamen and the right cerebrospinal fluid with “Slow down and speed up” type in K∥ values. The MD values and age showed “parabola” type in all of the positions. The corpus callosum, both side of the external capsule, cortical gray matter, cerebrospinal fluid showed rising type in FA values, while the left and right caudate putamen showed the type like “U”.Conclusion:1 No laterality is found in the MK, K∥, K⊥, MD and FA values of both side of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid.2 There are significant difference in the MK and K⊥ values of different age groups in the corpus callosum, both side of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid; the K∥ values in the left cortical gray matter; the MD values in both side of the external capsule, cortical gray matter, caudate putamen and cerebrospinal fluid; the FA values in both side of the external capsule, the right cortical gray matter and both side of the caudate putamen. While the other positions find no significant difference in different parameters of different age groups.3 Showing in the estimated curves: with age growing, the MK, K∥, K⊥, MD values show “parabola” type in all of the corpus callosum, both side of the external capsule, cortical gray matter, caudate putamen, cerebrospinal fluid, except the left caudate putamen and the right cerebrospinal fluid with “Slow down and speed up” type in K∥ values. The left and right caudate putamen show the type like “U”,while other parts show rising type in FA values,4 Compared MK and K⊥ with MD and FA, the formers are more sensitive to microstructural changes. |
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