Phase information of the magnetic resonance signal of biological tissue

磁共振（MR）是一种非侵入性和多功能的成像和光谱技术。利用MR，可以以各种方式探测生物组织，包括水扩散、信号弛豫或细胞代谢物的光谱的研究。当我们用磁场操纵原子核时，所有这些信息都由原子核发出的信号携带。 MR信号可以比作灯塔的光束。MR信号强度对应于射束的亮度。MR信号的第二方面是其相位，其对应于射束在特定时间指向的方向。通常，只使用幅度，而相位通常被忽略。然而，相位承载着丰富的信息。例如，相位允许研究自旋的磁环境，例如组织磁化率。最近的研究还表明，组织的微观结构和取向对相位有影响。然而，这些频率偏移的来源仍然知之甚少。拟议的研究计划的长期目标是开发定量技术的基础上的MR信号相位的生物组织的调查。我们将研究组织的空间取向和结构如何影响相位。为此，我们将开发用于MR数据采集和处理的新技术。我们将把这些方法应用于植物、动物和人类的组织，如芹菜、脑和脊髓的白色物质和软骨。

Magnetic Resonance (MR) is a non-invasive and versatile technique for imaging and spectroscopy. With MR one can probe biological tissue in various ways, including the investigation of water diffusion, signal relaxation or spectra of cell metabolites. All this information is carried by the signal emitted by atomic nuclei when we manipulate them with magnetic fields. The MR signal can be compared to the beam of a lighthouse. The MR signal strength corresponds to the brightness of the beam. A second aspect of the MR signal is its phase, which corresponds to the direction in which the beam is pointing at a certain time. Usually, only the magnitude is used and the phase is often ignored. However, phase bears a wealth of information. For instance, phase allows the investigation of the spins' magnetic environment, such as tissue magnetic susceptibility. Recent research also showed that the microstructure and the orientation of tissue have an influence on phase. The sources of these frequency shifts, however, are still only poorly understood. The long term objective of the proposed research program is to develop quantitative techniques based on MR signal phase for the investigation of biological tissue. We will investigate how the spatial orientation and the structure of tissue influences the phase. For this we will develop new techniques for MR data acquisition and processing. We will apply these methods to tissues of plants, animals and humans, such as celery, white matter of the brain and spinal cord, and cartilage.