Phase information of the magnetic resonance signal of biological tissue

磁共振(MR)是一种非侵入性的、多功能的成像和光谱分析技术。利用磁共振，人们可以通过各种方式探测生物组织，包括研究水的扩散、信号松弛或细胞代谢物的光谱。当我们用磁场操纵原子核时，所有这些信息都是由原子核发出的信号携带的。磁共振信号可以比作灯塔的横梁。MR信号强度对应于波束的亮度。MR信号的第二个方面是它的相位，它对应于波束在某一时刻指向的方向。通常，只使用震级，而忽略了相位。然而，阶段承载着丰富的信息。例如，相位允许研究自旋的磁性环境，如组织磁化率。最近的研究也表明，组织的微观结构和取向对相有影响。然而，这些频移的来源仍然鲜为人知。拟议的研究计划的长期目标是开发基于磁共振信号相位的定量技术，用于生物组织的研究。我们将研究组织的空间取向和结构如何影响相位。为此，我们将开发新的磁共振数据采集和处理技术。我们将把这些方法应用于植物、动物和人类的组织，如芹菜、大脑和脊髓的白质，以及软骨。

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.