The influence of myelin ultrastructure in determining magnetic resonance contrast

磁共振成像(MRI)是研究大脑和脊髓的强大技术，也被称为中枢神经系统(CNS)。核磁共振测量的信号主要来自水--水的位置和行为提供了关于组织结构的信息。尽管磁共振成像用于中枢神经系统成像已有三十多年的历史，但对影响磁共振成像信号的具体因素仍知之甚少。例如，大脑发育过程中发生的MRI对比度变化的原因需要更多的研究。此外，MRI对比度在不同的大脑和脊髓区域也有差异，但这种信号差异的来源尚不清楚。中枢神经系统组织的一个主要成分是髓鞘，它在大脑和脊髓周围的结构上有所不同。髓鞘是包裹神经细胞的绝缘鞘--它使信号快速传递，对中枢神经系统的功能至关重要。髓鞘对MRI信号的影响还没有详细的研究，但可能是非常重要的。髓鞘由多层蛋白质和脂类组成。由于MRI扫描仪的局限性，我们无法从髓鞘脂类和蛋白质中获得信号。然而，髓磷脂也含有~40%的水分，存在于脂肪/蛋白质层之间。这种“髓鞘水”可以用我们开发的一种特殊的高级核磁共振方法来测量，该方法已被证明与髓鞘脂/蛋白层有关。鉴于MRI的广泛使用，确定髓鞘如何影响中枢神经系统的MRI对比度是很重要的。例如，髓鞘脂肪和蛋白质含量的区域差异以及髓鞘厚度的差异将影响MRI测量。我们研究的长期目标是了解组织微结构如何影响中枢神经系统的MRI对比度。短期内，我们的研究将集中于确定

Magnetic resonance imaging (MRI) is a powerful technique for studying the brain and spinal cord which is also called the central nervous system (CNS). The signal that MRI measures comes mainly from water – the location and behaviour of the water gives information about tissue structure. Despite the fact that MRI has been used to image the CNS for over three decades, the specific factors that contribute to the MRI signal are still poorly understood. For example, the cause of MRI contrast changes that happen during brain development needs more research. Also, variation in MRI contrast is seen in different brain and spinal cord regions, but the source of this signal variation is unknown. A major component of CNS tissue that varies structurally around the brain and spinal cord is myelin. Myelin is an insulating sheath that surrounds nerve cells - it makes signals travel quickly and is crucial to CNS function. The influence of myelin on MRI signal has not been studied in detail, but is likely very important. Myelin is made up of many layers of proteins and lipids. Because of the limitations of the MRI scanner, we cannot get signal from the myelin lipids and proteins. However, myelin also contains ~40% water which is found between the lipid/protein layers. This ‘myelin water’ can be measured with a special advanced MRI method we have developed that has been proven to be related to the myelin lipid/protein layers. Given the widespread use of MRI, determining how myelin influences MRI contrast in the CNS is important. For example, regional variations in myelin lipid and protein content and differences in myelin thickness would influence MRI measurements. The long term goal of our research is to understand how tissue microstructure influences MRI contrast in the CNS. In the short term, our research will focus on determining how