Diffusion Imaging in Gray Matter

描述（由申请人提供）：扩散张量成像（DTI）对神经组织中扩散各向异性（DA）的微观变化具有敏感性，作为一种提供神经组织结构状态非侵入性评估潜力的方法，在基础神经科学研究和临床应用中引起了极大的兴趣。然而，标准的DTI方法，包括其高角分辨率（HARDI）扩展，它利用了一对脉冲场梯度（sPFG），是基于存在的体素组合物，表现出宏观DA的成像分辨率的规模。这通常是含有白色物质（WM）纤维束的体素的情况，因此WM中的DTI已经成为DTI研究和应用的主要焦点。然而，这是不是在灰质（GM）的情况下，这是微观异质性，但缺乏结构的连贯性体素的空间尺度上表现出宏观DA。这严重限制了我们的能力，利用MRI的灵敏度扩散GM微观结构的调查，这是一个组织的显着的临床利益。最近，一组新的MR方法的基础上的双脉冲场梯度（dPFG）对理论上进行了研究，并在简单的实验中验证，表现出对微观DA的体素是宏观均匀的灵敏度。这些研究主要应用于具有微观孔隙的材料，反映了这些方法开发的多孔材料的重点。然而，虽然我们假设这些方法对GM的研究具有很大的潜力，但这种组织的巨大复杂性使得在GM中研究dPFG方法几乎不可能进行分析。因此，本提案的目标是利用我们最近开发的扩散模拟平台（DiffSim），结合我们最近开发的dPFG理论框架，研究dPFG方法检测和定量灰质结构参数和变化的能力，并开发实验技术，将这些方法应用于临床。 公共卫生相关性：虽然扩散张量成像（DTI）是一种磁共振成像（MRI）技术，其提供了对神经组织结构的非侵入性评估的潜力，但其使用是基于在成像分辨率尺度上具有宏观组织的神经纤维的存在;因此，其应用几乎仅限于白色物质（WM）结构和疾病，而不包括灰质（GM），其在宏观上是不连贯的，尽管在微观上是连贯的。然而，最近，一类新的扩散敏感的MRI方法，称为双脉冲场梯度（dPFG）MRI，已被证明是一个独特的敏感性，显微镜相干组织，从而可能有一个巨大的影响，广泛的临床和基础研究应用相关的GM。我们的目标是使用我们先进的扩散MRI模拟平台DiffSim来增强我们对GM中dPFG的理论研究，以开发在人类中的实际实施，从而为临床技术提供一致和有意义的GM结构和生理学测量提供基础。

DESCRIPTION (provided by applicant): Diffusion tensor imaging (DTI), with its sensitivity to microscopic variations in diffusion anisotropy (DA) in neural tissues, has generated great interest in both basic neuroscience research and clinical applications as a method that offers the potential for the non-invasive assessment of the status of neural tissue architecture. However, the standard DTI methodology, including its high angular resolution (HARDI) extensions, which utilizes a single pair of pulsed field gradients (sPFG), are predicated on the existence of voxel compositions that exhibit a macroscopic DA on the scale of the imaging resolution. This is often the case with voxels containing bundles of white matter (WM) fibers and thus DTI in WM has become a major focus of DTI research and applications. However, this is not the case in gray matter (GM) which is microscopically heterogeneous but lacks the structural coherence on the spatial scale of voxels to exhibit macroscopic DA. This has severely limited our ability to utilize the sensitivity of MRI to diffusion in the investigation of GM microstructure, which is a tissue of significant clinical interest. Recently, a novel set of MR methods based upon the double pulsed field gradient (dPFG) pairs have been investigated theoretically and verified in simple experiments to exhibit sensitivity to microscopic DA in voxels that are macroscopically homogeneous. These studies have primarily been applied to materials with microscopic pores, reflecting the focus on porous materials from which these methods developed. However, while we hypothesize that these methods have great potential for the study of GM, the great complexity of this tissue makes investigation of dPFG methods in GM nearly impossible to do analytically. Thus the goal of this proposal is to utilize our recently developed diffusion simulation platform (DiffSim), in conjunction with our recently developed theoretical framework for dPFG, to investigate the ability of dPFG methods to detect and quantitate gray matter architectural parameters and changes, and develop experimental techniques for applying these methods clinically. PUBLIC HEALTH RELEVANCE: While diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that offers the potential for the non-invasive assessment of neural tissue structure, its usage is predicated on the existence of neuronal fibers with macroscopic organization on the scale of imaging resolution; thus its application has been almost exclusively to white matter (WM) structure and disease, to the exclusion of gray matter (GM), which is macroscopically incoherent, despite being microscopically coherent. Recently, however, a new class of diffusion sensitive MRI methods, called double pulsed field gradient (dPFG) MRI, has demonstrated a unique sensitivity to microscopically coherent tissues and thus may have an enormous impact on a wide range of clinical and basic research applications related to GM. Our goal is to use our sophisticated diffusion MRI simulation platform DiffSim to augment our theoretical studies of dPFG in GM to develop practical implementations in humans and thus provide the basis for clinical techniques that provide consistent and meaningful measurements of GM architecture and physiology.