Next-Generation fMRI with MB-SWIFT: Insights into the Origins of Contrast

采用 MB-SWIFT 的下一代功能磁共振成像：洞察对比度的起源

• 批准号: 10296096
• 负责人: SHALOM MICHAELI
• 金额: $ 57.04万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2024-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10296096
• 关键词: 3-Dimensional; Acoustics; Affect; Air; Animals; Basic Science; Behavioral; Blood flow; Brain; Brain Mapping; Cerebrovascular Circulation; Child; Clinical Research; Coiled Bodies; Consensus; Dependence; Detection; Devices; Dropout; Echo-Planar Imaging; Electrodes; Electrophysiology (science); Event; Frequencies; Functional Magnetic Resonance Imaging; Gases; Goals; Head; Human; Hypercapnia; Hyperoxia; Hypoxia; Image; Immobilization; Implant; Intervention; Investigation; Ions; Link; Loudness; Magnetic Resonance Imaging; Measures; Mediating; Membrane; Membrane Potentials; Metabolic; Methods; Morphologic artifacts; Motion; Movement; Neurons; Noise; Physiologic pulse; Physiological; Population; Predisposition; Proxy; Rattus; Relaxation; Research; Resolution; Rodent; Signal Transduction; Somatosensory Cortex; Specificity; Stimulus; Techniques; Testing; Time; Tissues; Vibrissae; awake; design; hemodynamics; insight; magnetic field; metallicity; neuroregulation; next generation; normoxia; novel; pre-clinical research; preservation; response; temporal measurement; tool; virtual

ABSTRACT Our long term goal is to establish the newly developed zero echo time MRI pulse sequence entitled Multi-Band SWeep Imaging with Fourier Transformation (MB-SWIFT) as the next-generation method of choice for artefact- free, quiet, high-resolution fMRI in humans, suitable for detecting neuronal activity via cellular mechanisms linked to electrical events that are intrinsically unattainable with standard readout sequences. MB-SWIFT has been already proven to offer remarkable advantages as compared to current fMRI techniques, since it is minimally impacted by susceptibility artefacts, has high tolerance for movement, and produces a nearly silent, continuous acoustic noise during acquisitions thanks to the use of slowly switching gradients. However, the origin of the functional contrast has remained elusive so far. Our general hypothesis is that MB-SWIFT functional signals closely reflect changes in local field potentials. We also advance the hypothesis that a non-negligible portion of the contrast may arise from T1 contrast mechanisms involving the pool of immobilized spins that are most likely sensitized to neuronal currents. Before undertaking a full-blown study that elucidates how relaxation mechanisms linked to membrane potentials and ions redistributions impact MB-SWIFT signals, we first need to validate that MB-SWIFT signals are sensitive proxies of neuronal activity, and determine whether they are substantially mediated by relaxation mechanisms not explained by blood flow or oxygenation changes. Ergo, the current proof- of-concept study in rodents will first establish to what extent MB-SWIFT signals reflect changes in neuronal activity under awake, physiological conditions by acquiring fMRI signals with MB-SWIFT and electrophysiological recording in somatosensory cortex during whisker stimulations of different duration and frequency. Then, we will evaluate to what extent MB-SWIFT signals are sensitive to changes in oxygenation levels and cerebral blood flow by conducting mechanistic studies during gas challenges, with different coil designs meant to isolate the inflow contribution, and with different magnetic fields, meant to verify the presence of T1-mechanisms of possible tissue origin. By achieving these aims we will gain pivotal insights into the substrates of the MB-SWIFT fMRI signals, and will reach initial milestones that will advance MB-SWIFT towards detection of neuronal currents, a goal that has been looked after for more than 20 years. In addition, the implications of the mechanistic studies will expand beyond MB-SWIFT, and they will be relevant to other MRI approaches with virtually zero echo time.

摘要 我们的长期目标是建立新开发的零回波时间MRI脉冲序列称为多波段 傅里叶变换扫描成像（MB-SWIFT）是下一代伪影检测方法的首选- 自由，安静，高分辨率的功能磁共振成像在人类，适用于检测神经元活动通过细胞机制连接 对于标准读出序列本质上无法获得的电事件。MB-SWIFT已成为 与目前的功能磁共振成像技术相比，它已经被证明具有显着的优势，因为它是最低限度的 受敏感性伪影的影响，对运动有很高的耐受性，并产生几乎无声的连续 由于使用缓慢切换的梯度，采集期间的声学噪声。然而， 功能对比至今仍是难以捉摸的。我们的一般假设是，MB-SWIFT功能信号 密切反映局部场电位的变化。我们还提出了一个假设，即一个不可忽略的部分， 对比度可以由T1对比度机制引起，该机制涉及最有可能 对神经元电流敏感。在进行一项全面的研究来阐明放松机制如何 与膜电位和离子再分布影响MB-SWIFT信号有关，我们首先需要验证 MB-SWIFT信号是神经元活动的敏感代理，并决定它们是否实质上是神经元活动的信号。 由不能用血流或氧合变化解释的松弛机制介导。因此，目前的证据- 在啮齿动物中的概念研究将首先确定MB-SWIFT信号在多大程度上反映神经元的变化。 在清醒的生理条件下，通过MB-SWIFT和电生理学获取fMRI信号， 在不同的持续时间和频率的胡须刺激过程中记录在躯体感觉皮层中。那就 评估MB-SWIFT信号对氧合水平和脑血变化的敏感程度 通过在气体挑战期间进行机械研究，使用不同的线圈设计来隔离 流入贡献，并与不同的磁场，旨在验证T1的存在-机制的可能 组织起源通过实现这些目标，我们将获得MB-SWIFT fMRI基底的关键见解 信号，并将达到初步的里程碑，这将推动MB-SWIFT对神经元电流的检测， 这个目标已经实现了20多年。此外，机制研究的影响 将扩展到MB-SWIFT之外，并且它们将与回波时间几乎为零的其他MRI方法相关。