Angular Dependency of T1 Relaxation Time in Cerebral White Matter in Ultrahigh Field MRI

项目摘要 大脑磁共振成像（MRI）扫描中的对比度受复杂的 水、脑大分子和微结构成分之间的相互作用。的 最常用的基于MR弛豫的对比度随磁场强度而变化， 因为T1和T2 MR弛豫时间都是场相关的。在更高的领域固有的 组织特异性因素，如由于组织微结构而导致的体磁化率 和/或生物化学制造，影响弛豫，从而影响MRI对比度。用于有效 以及在神经科学研究和临床诊断中充分利用MR图像， 关键在于了解组织相关因素对临床上基于松弛的对比的影响 (such如3特斯拉=T）和超高频（UHF，7 T或以上）MRI。 该提案的主旨是研究人类T1弛豫的角度依赖性 白色物质（WM）在3 T和7 T。我们的目标是了解磁共振可见光的影响， 水对WM中T1弛豫的角度依赖性。实验旨在 研究磁场强度、轴突直径和磁化传递在 MR可见水和T1弛豫时间的光纤-场依赖性。MRI数据将 在3 T和7 T下从健康成人参与者获得。该项目的具体目标如下： 目的1：测量MR可见水的角度依赖性的幅度， WM的T1弛豫时间，并研究其与WM束轴突微结构的关系， 例如轴突直径。目的2：研究磁刺激电流幅值的磁场依赖性， MR-可见水和WM中的T1弛豫。目标3：研究磁化的影响 MR-可见水和T1弛豫的角度依赖性的幅度上的转移 3 T和7 T时的WM时间。 该项目增加了我们的长期追求，以促进对生物物理的理解， 大脑图像中MR对比的基础。我们的首要目标是改善 通过MRI对正常脑及其疾病进行成像的组织形态描绘 现代神经影像学

PROJECT SUMMARY Contrast in magnetic resonance imaging (MRI) scans of the brain are influenced by complex interactions between water, brain macromolecules and microstructural compenents. The most commonly used MR relaxation-based contrasts change with magnetic field strength, because both T1 and T2 MR relaxation times are field dependent. At higher fields inherent tissue-specific factors, such as bulk magnetic susceptibility due to tissue microstructure and/or biochemical making, affect relaxation thereby influencing MRI contrast. For efficient and adequate use of MR images in neuroscientific research and clinical diagnosis, it is pivotal to understand effects of tissue-related factors on relaxation-based contrasts at clinical (such as 3 Tesla=T) and ultrahigh field (UHF, 7T or above) MRI. The thrust of the proposal is to study the angular dependency of T1 relaxation in human white matter (WM) at 3T and 7T. Our goal is to gain understanding of effects of MR-visible water on the angular dependency of T1 relaxation in WM. Experiments are designed to study the role of the magnetic field strength, axonal diameter and magnetization transfer in the fiber-to-field dependency of MR-visible water and T1 relaxation time. MRI data will be acquired from healthy adult participants at 3T and 7T. The specific aims of the project are as follows: AIM 1: to measure the amplitude of the angular dependency of MR-visible water and T1 relaxation time in WM and study its relationship with WM tracts axonal microstructure, such as axonal diameter. AIM 2: to study the magnetic field dependency of the amplitude of MR-visible water and T1 relaxation in WM. AIM3: to study the effects of magnetization transfer on the amplitude of the angular dependency of MR-visible water and T1 relaxation time in WM at 3T and 7T. The project adds to our long-term pursuit to advance understanding of biophysical underpinnings of MR contrasts in brain images. Our overarching goal is to improve delineation of tissue morphology by MRI for imaging of normal brain and its disorders in modern neuroimaging.