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):1334-41.
The magnetization transfer ratio (MTR) is a sensitive and quantitative identifier of underlying structural changes in the brain. We quantitatively evaluated age- and sex-related MTR changes in global gray matter (GM) and global white matter (WM) in healthy adults.
Fifty-two healthy volunteers (21 men, 31 women) aged 20-86 years underwent dual-echo fast spin-echo and magnetization transfer imaging performed with and then without a saturation pulse. GM and WM were distinguished by using a computer-assisted semiautomated segmentation technique. MTR histograms were generated for each segmented tissue in each subject and compared among age and sex groups.
The mean, median, first quartile, and peak height of the MTR histogram were significantly lower in the older group (> or =50 years) than those in the younger group (<50 years) for both GM and WM. The age dependency of these values can be expressed in a quadratic fashion over the entire span of adulthood. The MTRs started to decline only after the age of approximately 40 years in both tissues. No statistically significant differences in MTR histogram measurements between the sexes were observed.
The different MTR values for both GM and WM in the two age groups suggest that notable microscopic changes occur in GM and WM with advancing age, yet no significant sex-related variations in MTR measurements were found in these neurologically healthy adults. Such normative data based on the inherent contrast in MTRs are essential in studies of specific disorders of aging, and they may have implications for our understanding of the gross structural changes in both GM and WM in the aging brain.
磁化传递率（MTR）是大脑潜在结构变化的敏感且定量的标识物。我们定量评估了健康成年人全脑灰质（GM）和全脑白质（WM）中与年龄和性别相关的MTR变化。
52名年龄在20 - 86岁的健康志愿者（21名男性，31名女性）接受了双回波快速自旋回波成像和有及无饱和脉冲的磁化传递成像。采用计算机辅助半自动分割技术区分GM和WM。为每个受试者的每个分割组织生成MTR直方图，并在年龄和性别组之间进行比较。
在GM和WM中，老年组（≥50岁）的MTR直方图的均值、中位数、第一四分位数和峰值高度均显著低于年轻组（<50岁）。在成年期的整个跨度内，这些值的年龄依赖性可以用二次函数来表示。在这两种组织中，MTR仅在大约40岁之后才开始下降。未观察到性别之间MTR直方图测量值的统计学显著差异。
两个年龄组中GM和WM的不同MTR值表明，随着年龄增长，GM和WM中发生了显著的微观变化，但在这些神经健康的成年人中未发现MTR测量值存在显著的性别相关差异。基于MTR固有对比度的此类规范数据在衰老特定疾病的研究中至关重要，并且它们可能对我们理解衰老大脑中GM和WM的总体结构变化具有启示意义。
