Ge Yulin, Grossman Robert I, Babb James S, Rabin Marcie L, Mannon Lois J, Kolson Dennis L
Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, USA.
AJNR Am J Neuroradiol. 2002 Sep;23(8):1327-33.
A technique of segmenting total gray matter (GM) and total white matter (WM) in human brain is now available. We investigated the effects of age and sex on total fractional GM (%GM) and total fractional WM (%WM) volumes by using volumetric MR imaging in healthy adults.
Fifty-four healthy volunteers (22 men, 32 women) aged 20-86 years underwent dual-echo fast spin-echo MR imaging. Total GM, total WM, and intracranial space volumes were segmented by using MR image-based computerized semiautomated software. Volumes were normalized as a percentage of intracranial volume (%GM and %WM) to adjust for variations in head size. Age and sex effects were then assessed.
Both %GM and %WM in the intracranial space were significantly less in older subjects (> or =50 years) than in younger subjects (<50 years) (P <.0001 and P =.02, respectively). Consistently, %GM decreased linearly with age, beginning in the youngest subjects. %WM decreased in a quadratic fashion, with a greater rate beginning only in adult midlife. Although larger GM volumes were observed in men before adjustments for cranium size, no significant differences in %GM or %WM were observed between the sexes.
GM volume loss appears to be a constant, linear function of age throughout adult life, whereas WM volume loss seems to be delayed until middle adult life. Both appear to be independent of sex. Quantitative analysis of %GM and %WM volumes can improve our understanding of brain atrophy due to normal aging; this knowledge may be valuable in distinguishing atrophy of disease patterns from characteristics of the normal aging process.
目前已有一种在人脑内分割全灰质（GM）和全白质（WM）的技术。我们通过对健康成年人进行容积磁共振成像，研究年龄和性别对全脑灰质分数（%GM）和全脑白质分数（%WM）体积的影响。
54名年龄在20 - 86岁之间的健康志愿者（22名男性，32名女性）接受了双回波快速自旋回波磁共振成像检查。使用基于磁共振图像的计算机半自动软件分割全脑GM、全脑WM和颅内空间体积。将体积归一化为颅内体积的百分比（%GM和%WM），以校正头部大小的差异。然后评估年龄和性别的影响。
颅内空间的%GM和%WM在老年受试者（≥50岁）中均显著低于年轻受试者（<50岁）（分别为P <.0001和P =.02）。一致地，%GM从最年轻的受试者开始就随年龄呈线性下降。%WM呈二次方下降，仅在成年中期开始下降速度加快。尽管在调整颅骨大小之前男性的GM体积较大，但在%GM或%WM方面未观察到性别间的显著差异。
在整个成年期，GM体积损失似乎是年龄的恒定线性函数，而WM体积损失似乎延迟至成年中期。两者似乎均与性别无关。对%GM和%WM体积进行定量分析可增进我们对正常衰老所致脑萎缩的理解；这一知识对于区分疾病模式的萎缩与正常衰老过程的特征可能具有重要价值。
