Structural dynamics of the human brain in vivo from tagged MRI and MR elastography.

项目总结/摘要 创伤性脑损伤（TBI）是广泛的，并可能使人衰弱，多次轻度头部撞击可 可能导致慢性创伤性脑病（CTE）。尽管其重要性， 大脑对头骨加速度的反应还不完全清楚。该项目旨在确定和 利用磁共振成像（MRI）， 在轻微的头部加速度（无论是非常轻的影响或低振幅振动）的大脑。模式 振荡是大脑特别容易受到伤害的运动类型;这种模式可以被头骨激活 具有特定频率分量的特定方向的运动。在初步研究中，我发现 通过分析位移和应变， 数据集从标记的MRI与方法称为动态模式分解。在这个项目中，我假设 特别是主要的自然振荡模式，以及大脑对头骨的动态反应， 一般来说，所有受试者的兴奋程度都是相似的，但反应的参数在数量上会有所不同 在不同年龄和性别的受试者中（由于大小、形状和硬度的差异）。在目标1中，我将确定 并再次使用标记的动态模式分解来表征人脑中的振荡模式。 MRI数据，不同年龄和性别的受试者组。具体来说，我将量化阻尼自然 频率、阻尼比、模态系数和表征每个模态的空间模式（模态形状） 模式这些数量将在两个不同的时间段内从三个年龄组的男性和女性受试者中获得。 头部运动的类型：（i）前后运动（颈部伸展，或“是”点头）和（ii）轴向旋转（颈部 旋转或“不”点头）。在目标2中，我将确定人脑对谐波颅骨的频率响应 运动使用磁共振弹性成像（MRE），再次在不同年龄和性别的受试者。这将 以确定在MRE中观察到的谐波脑变形是否反映了解剖学或 由于年龄或性别的生理差异。MRE研究将在一定频率范围内进行， 枕部兴奋（前后运动）或侧向兴奋（左右运动）。的关键特征 大脑的响应是大脑变形的幅度（剪切应变幅度）相对于头骨的幅度 加速度这一比例预计会随着颅骨运动的方向和频率以及年龄而变化 和性别这些目标的成功完成将提供定量的了解如何颅骨运动导致 在不同的影响情况下，大脑特定区域的大脑变形，并允许定量 评估TBI的计算机模型。这种理解最终将对有效预防和 TBI和CTE的治疗。

PROJECT SUMMARY/ABSTRACT Traumatic brain injury (TBI) is widespread and potentially debilitating, and multiple mild head impacts can potentially cause chronic traumatic encephalopathy (CTE). Despite its importance, the underlying mechanics of the brain’s response to skull acceleration are not fully understood. This project is designed to identify and characterize natural modes of oscillation in the living human brain, using magnetic resonance imaging (MRI) of the brain during mild head accelerations (either very light impacts or low-amplitude vibration). Modes of oscillation are types of motion to which the brain is particularly vulnerable; such modes can be activated by skull motion in specific directions with particular frequency components. In preliminary studies I have identified seemingly consistent modes of oscillation in brains of 19 human subjects, by analyzing displacement and strain data sets from tagged MRI with a method known as dynamic mode decomposition. In this project, I hypothesize that the dominant natural modes of oscillation in particular, and the dynamic response of the brain to skull excitation in general, will be similar across all subjects, but the parameters of the response will differ quantitatively in subjects of different age and gender (due to differences in size, shape, and stiffness). In Aim 1, I will identify and characterize modes of oscillation in the human brain, again using dynamic mode decomposition of tagged MRI data, in groups of subjects of different ages and genders. Specifically I will quantify the damped natural frequencies, damping ratios, modal coefficients, and spatial patterns (mode shapes) that characterize each mode. These quantities will be obtained for male and female subjects in three age groups, during two different types of head motion: (i) anterior-posterior motion (neck extension, or “yes” nodding) and (ii) axial rotation (neck rotation, or “no” nodding). In Aim 2 I will determine the frequency response of the human brain to harmonic skull motion using magnetic resonance elastography (MRE), again in subjects of different ages and genders. This will be done to determine whether the harmonic brain deformations observed in MRE reflect anatomical or physiological differences due to age or sex. MRE studies will be performed over a range of frequencies, with either occipital excitation (anterior-posterior motion) or lateral excitation (right-left motion). A key feature of the brain’s response is the amplitude of brain deformation (shear strain amplitude) relative to the amplitude of skull acceleration. This ratio is expected to vary with the direction and frequency of skull motion, as well as with age and sex. Successful completion of these Aims will provide quantitative understanding of how skull motion leads to brain deformation in specific regions of the brain, under different impact scenarios, and allow quantitative assessment of computer models of TBI. This understanding will ultimately be critical to effective prevention and treatment of TBI and CTE.