J Korean Soc Magn Reson Med.  2011 Apr;15(1):32-40. 10.13104/jksmrm.2011.15.1.32.

The Age-related Microstructural Changes of the Cortical Gray and White Matter Ratios on T2-, FLAIR and T1-weighted MR Images

• Choi S
• Kim WY
• Lee KN
• Ha DH
• Kang MJ
• Lee JH
• Yoon SK

• KMID: 2041225
• DOI: http://doi.org/10.13104/jksmrm.2011.15.1.32

Abstract

PURPOSE
The purpose of this study was to investigate the microstructural changes according to aging on the thickness and signal intensity (SI) of the cortical gray matter (GM) and white matter (WM) on the T2-, fluid-attenuated inversion recovery (FLAIR) and T1-weighted MR images in normal subjects.
MATERIALS AND METHODS
The 10, 20, 30, 40, 50, 60, 70, 80 and 90 year age groups of men and women (each 10 individuals) who underwent routine brain MRI, including the T2-, FLAIR and T1-weighted images, were selected for this study. We measured the thickness and the SI of the cortical GM and WM at the postcentral gyrus, which has an even thickness at the level of centrum semiovale, on the axial scans and we calculated the mean values of the thickness ratio of the gray/white matter (TRGW) and the signal intensity ratio of the gray/white matter (SRGW), and we compared the ratios of each age group.
RESULTS
On the T2-weighted images, the TRGWs were 0.81 and 0.79 at the age of 10 and they were 0.73 and 0.71 at the age of 90 in the men and women, respectively. So, the GM thickness was decreased more than the WM thickness was with aging. On the FLAIR images, the TRGWs were 1.09 and 1.00 at the age of 10 and they were 1.11 and 0.95 at the age of 70 in the men and women, respectively. On the T1-weighted images, the TRGWs were 0.66 and 0.80 at the age of 10, and the ratio was changed to 0.90 and 0.78 at the age of 90 in the men and women, respectively. On the T2-weighted image, the SRGWs were 1.53 and 1.43 at the age of 10, and they were 1.23 and 1.27 at the age of 90 in the men and women, respectively. On the FLAIR images, the SRGWs were 1.23 and 1.25 at the age of 10 and they were 1.06 and 1.05 at the age of 90 in the men and women, respectively. On the T1-weighted images, the SRGWs were 0.86 and 0.85 at the age of 10, and they were 0.90 and 0.87 at the age of 90 in the men and women, respectively.
CONCLUSION
We suggest that the age-related microstructural changes of the thickness and the SI of the cortical GM and WM on the T2-, FLAIR and T1-weighted images are unique, and so this knowledge will be helpful to differentiate neurodegenerative disease from normal aging of the brain.

Keyword

Brain; Aging; MRI

MeSH Terms

Aging
Brain
Female
Humans
Male
Neurodegenerative Diseases

Figure

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  Fig. 1 Example of measuring the thicknesses of the cortical gray matter (upper row) and white matter (bottom row) on the T2-weighted (left), FLAIR (middle) and T1-weighted (right) images.

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  Fig. 2 Example of measuring the signal intensities of the cortical gray matter (upper row) and white matter (bottom row) on the T2-weighted (left), FLAIR (middle) and T1-weighted (right) images.

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  Fig. 3 The slopes of the thickness ratios on the T2-weighted images. The ratios decreased slightly with aging.

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  Fig. 4 The slopes of the thickness ratios on the FLAIR images. The ratios showed the lowest value at the age of 30 in men and at the age of 40 in women. The measurements of the GM and WM thickness separately were not possible in the aged brain, and so the 80 and 90 year old age groups were excluded.

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  Fig. 5 The slopes of the thickness ratios on the T1-weighted images. The ratios increased slightly with aging.

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  Fig. 6 The slopes of the signal intensity ratios on the T2-weighted images. The contrast between the GM and WM was decreased with aging.

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  Fig. 7 The slopes of the signal intensity ratios on the FLAIR images. The ratios were decreased to 1 with aging, which means the contrast between the GM and WM had almost disappeared.

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  Fig. 8 The slopes of the signal intensity ratios on the T1-weighted images. The ratios were slightly increased with aging due to the decreased contrast between the GM and WM.

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