Huisman T A, Hawighorst H, Benoit C H, Sorensen A G
MGH-NMR Center, Massachusetts General Hospital and Harvard Medical School, Mailingcode 149 (2301), Charlestown-Boston, MA 02119, USA.
Radiologe. 2001 Dec;41(12):1038-47. doi: 10.1007/s001170170003.
Diffusion weighted magnetic resonance imaging (DWI) represents a recent development that extends imaging from the depiction of the neuroanatomy into the field of functional and physiologic processes. DWI measures a fundamentally different physiologic parameter than conventional MRI. Image contrast is related to differences in the microscopic motion (diffusion) of water molecules within brain tissue rather than a change in total tissue water. Consequently, DWI can reveal pathology where conventional T1- and T2-weighted MR images are negative. DWI has clinically proven its value in the assessment of acute cerebral stroke and trauma by showing cerebral injury early due to ist ability to discriminate between lesions with cytotoxic edema (decreased diffusion) from lesions with vasogenic edema (increased diffusion). Full tensor DWI allows to calculate a variety of functional maps, the most widely used maps include maps of apparent diffusion coefficients and isotropic diffusion. In addition maps of anisotropic diffusion can be calculated which are believed to give information about the integrity and location of fiber tracts. This functional-anatomical information will most probably play an increasingly important role in the early detection of primary and secondary tissue injury from various reasons and could guide and validate current and future neuroprotective treatments.
扩散加权磁共振成像（DWI）是一项最新进展，它将成像从神经解剖结构的描绘扩展到了功能和生理过程领域。与传统MRI相比，DWI测量的是一种截然不同的生理参数。图像对比度与脑组织内水分子微观运动（扩散）的差异有关，而非总组织含水量的变化。因此，在传统T1加权和T2加权MR图像呈阴性的情况下，DWI仍可显示病变。DWI已在临床上证明了其在评估急性脑卒中和创伤方面的价值，因为它能够早期显示脑损伤，这得益于其区分细胞毒性水肿（扩散降低）病变和血管源性水肿（扩散增加）病变的能力。全张量DWI能够计算多种功能图谱，其中使用最广泛的图谱包括表观扩散系数图谱和各向同性扩散图谱。此外，还可以计算各向异性扩散图谱，据信这些图谱能够提供有关纤维束完整性和位置的信息。这种功能解剖学信息很可能在早期检测各种原因导致的原发性和继发性组织损伤中发挥越来越重要的作用，并可为当前和未来的神经保护治疗提供指导和验证。
