Anisotropy effects of the magnetic resonance signal of biological tissue.

磁共振成像（MRI）是一种非侵入性和多功能的成像技术，在研究和诊断方面取得了巨大的成功。有了先进的MRI，人们可以探测生物组织的方式，使研究人员能够创建组织特性的定量地图。MRI评估的特征包括信号松弛、细胞代谢物浓度以及水扩散或血流的量和方向。近年来，已经表明，一些MRI技术对各向异性组织的主轴与磁场方向之间形成的角度敏感。例如，已经特别针对R2* 信号弛豫的图像描述了系统的取向依赖性（OD），其由当前的数学模型归因于各向同性和各向异性组织两者的贡献。如果能很好地理解，这些效应可能会被用于绘制早期大脑发育或组织损伤和修复的地图。

Magnetic Resonance Imaging (MRI) is a non-invasive and versatile imaging technique, which has seen tremendous success in research and diagnosis. With advanced MRI, one can probe biological tissues in ways that allow researchers to create quantitative maps of tissue properties. Characteristics assessed with MRI include the signal relaxation, the concentration of cell metabolites, and the amount and direction of water diffusion or blood flow. In recent years it has been shown that some MRI techniques are sensitive to the angle formed between the main axis of anisotropic tissues and the direction of the magnetic field. For instance, a systematic orientation dependency (OD) has been described in particular for images of R2* signal relaxation, attributed by current mathematical models to the contributions of both isotropic and anisotropic tissues. If understood well, these effects may be used to map early brain development or tissue damage and repair.