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

项目摘要/摘要 创伤性脑损伤(TBI)很普遍，可能会使人虚弱，多次轻微的头部撞击可能会 可能导致慢性创伤性脑病(CTE)。尽管它很重要，但它的基本机制 大脑对头骨加速的反应还不完全清楚。该项目旨在确定和 使用磁共振成像(MRI)表征活体人脑的自然振荡模式 在轻微的头部加速(非常轻微的撞击或低幅度振动)期间，大脑会受到影响。模式： 振动是大脑特别容易受到影响的运动类型；这种模式可以被头骨激活 在具有特定频率分量的特定方向上的运动。在初步研究中，我已经确定 通过分析位移和应变，19名受试者大脑似乎一致的振荡模式 使用一种称为动态模式分解的方法从标记的MRI中获取数据集。在这个项目中，我假设 尤其是振动的主要自然模式，以及大脑对头骨的动态反应 一般来说，所有受试者的激发都是相似的，但反应的参数在数量上是不同的。 在不同年龄和性别的受试者中(由于大小、形状和僵硬的不同)。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，按不同年龄和性别的受试者分组。具体地说，我将量化受潮的自然界 频率、阻尼比、振型系数和空间模式(振型) 模式。这些数量将在三个年龄组的男性和女性受试者中获得，在两个不同的 头部运动的类型：(一)前后运动(颈部伸展，或“是”点头)和(二)轴向旋转(颈部 轮流，或“不”点头)。在目标2中，我将测定人脑对谐和颅骨的频率响应。 同样，在不同年龄和性别的受试者中，使用磁共振弹性成像(MRE)进行运动。这将是 以确定在MRE中观察到的谐和脑变形是反映解剖学还是 因年龄或性别而产生的生理差异。MRE研究将在一系列频率上进行， 枕部兴奋(前后运动)或侧向兴奋(右-左运动)。的一项关键功能 大脑的反应是大脑变形的幅度(剪切应变幅度)相对于颅骨的幅度 加速。这一比例预计会随着头骨运动的方向和频率以及年龄的不同而变化。 还有性爱。这些目标的成功完成将提供对头骨运动如何导致 到大脑特定区域的变形，在不同的影响情景下，并允许量化 脑外伤计算机模型的评估。这一理解最终将对有效预防和 颅脑损伤和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.