LREN, Département des Neurosciences Cliniques, CHUV, Université de Lausanne, Lausanne, Switzerland.
Neuroimage. 2011 Apr 15;55(4):1423-34. doi: 10.1016/j.neuroimage.2011.01.052. Epub 2011 Jan 28.
Normal ageing is associated with characteristic changes in brain microstructure. Although in vivo neuroimaging captures spatial and temporal patterns of age-related changes of anatomy at the macroscopic scale, our knowledge of the underlying (patho)physiological processes at cellular and molecular levels is still limited. The aim of this study is to explore brain tissue properties in normal ageing using quantitative magnetic resonance imaging (MRI) alongside conventional morphological assessment. Using a whole-brain approach in a cohort of 26 adults, aged 18-85years, we performed voxel-based morphometric (VBM) analysis and voxel-based quantification (VBQ) of diffusion tensor, magnetization transfer (MT), R1, and R2* relaxation parameters. We found age-related reductions in cortical and subcortical grey matter volume paralleled by changes in fractional anisotropy (FA), mean diffusivity (MD), MT and R2*. The latter were regionally specific depending on their differential sensitivity to microscopic tissue properties. VBQ of white matter revealed distinct anatomical patterns of age-related change in microstructure. Widespread and profound reduction in MT contrasted with local FA decreases paralleled by MD increases. R1 reductions and R2* increases were observed to a smaller extent in overlapping occipito-parietal white matter regions. We interpret our findings, based on current biophysical models, as a fingerprint of age-dependent brain atrophy and underlying microstructural changes in myelin, iron deposits and water. The VBQ approach we present allows for systematic unbiased exploration of the interaction between imaging parameters and extends current methods for detection of neurodegenerative processes in the brain. The demonstrated parameter-specific distribution patterns offer insights into age-related brain structure changes in vivo and provide essential baseline data for studying disease against a background of healthy ageing.
正常衰老与大脑微观结构的特征变化有关。虽然体内神经影像学可以在宏观尺度上捕捉到与年龄相关的解剖结构变化的时空模式，但我们对细胞和分子水平上潜在的（病理）生理过程的了解仍然有限。本研究旨在使用定量磁共振成像（MRI）结合常规形态评估，探索正常衰老过程中的脑组织特性。我们对 26 名年龄在 18-85 岁的成年人进行了全脑研究，采用基于体素的形态计量学（VBM）分析和扩散张量、磁化传递（MT）、R1 和 R2弛豫参数的基于体素定量（VBQ）。我们发现皮质和皮质下灰质体积与各向异性分数（FA）、平均弥散度（MD）、MT 和 R2的变化呈年龄相关性降低。这些变化在区域上是特异性的，这取决于它们对微观组织特性的不同敏感性。白质的 VBQ 揭示了与年龄相关的微观结构变化的不同解剖模式。广泛而深刻的 MT 减少与局部 FA 减少和 MD 增加相平行。在重叠的枕顶叶白质区域观察到 R1 减少和 R2*增加的程度较小。我们根据当前的生物物理模型解释我们的发现，认为这是与年龄相关的脑萎缩和髓鞘、铁沉积和水的潜在微观结构变化的指纹。我们提出的 VBQ 方法允许对成像参数之间的相互作用进行系统的、无偏的探索，并扩展了目前用于检测大脑中神经退行性过程的方法。所展示的参数特异性分布模式提供了对体内与年龄相关的大脑结构变化的深入了解，并为研究健康衰老背景下的疾病提供了必要的基线数据。
