Le Bihan Denis
U.N.A.F., Service hospitalier Frédéric Joliot (SHFJ), Commissariat a ll'Energie Atomique (CEA), 4 place du Général Leclerc, 91401 Orsay, France.
Bull Acad Natl Med. 2006 Nov;190(8):1605-27; discussion 1627.
The success of diffusion MRI, which was introduced in the mid 1980s is deeply rooted in the powerful concept that during their random, diffusion-driven movements water molecules probe tissue structure at a microscopic scale well beyond the usual image resolution. The observation of these movements thus provides valuable information on the structure and the geometric organization of tissues. The most successful application of diffusion MRI has been in brain ischemia, following the discovery that water diffusion drops at a very early stage of the ischemic event. Diffusion MRI provides some patients with the opportunity to receive suitable treatment at a very acute stage when brain tissue might still be salvageable. On the other hand, diffusion is modulated by the spatial orientation of large bundles of myelinated axons running in parallel through in brain white matter. This feature can be exploited to map out the orientation in space of the white matter tracks and to visualize the connections between different parts of the brain on an individual basis. Furthermore, recent data suggest that diffusion MRI may also be used to visualize rapid dynamic tissue changes, such as neuronal swelling, associated with cortical activation, offering a new and direct approach to brain functional imaging.
扩散磁共振成像（Diffusion MRI）于20世纪80年代中期问世，其成功深深植根于一个强大的概念，即在水分子随机的、由扩散驱动的运动过程中，它们能在远超常规图像分辨率的微观尺度上探测组织结构。因此，对这些运动的观察为组织的结构和几何组织提供了有价值的信息。扩散磁共振成像最成功的应用是在脑缺血领域，这是在发现缺血事件非常早期阶段水扩散下降之后。扩散磁共振成像为一些患者提供了在脑组织可能仍可挽救的非常急性期接受适当治疗的机会。另一方面，扩散受到大量平行穿过脑白质的有髓轴突空间取向的调节。这一特性可用于描绘白质纤维束在空间中的取向，并在个体基础上可视化大脑不同部分之间的连接。此外，最近的数据表明，扩散磁共振成像还可用于可视化与皮质激活相关的快速动态组织变化，如神经元肿胀，为脑功能成像提供了一种新的直接方法。
