An acquisition and reconstruction framework to enable mesoscale human fMRI on clinical 3 Tesla scanners

一种采集和重建框架，可在临床 3 Tesla 扫描仪上实现中尺度人体 fMRI

• 批准号: 10481056
• 负责人: Kawin Setsompop
• 金额: $ 85.32万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10481056
• 关键词: 3-Dimensional; Address; Adoption; Animal Model; Animals; Benchmarking; Blood Vessels; Blood Volume; Blood flow; Brain; Brain imaging; Caliber; Cell Nucleus; Clinical; Communities; Consensus; Cortical Column; Coupling; Data; Data Set; Development; Dropout; Excision; Functional Imaging; Functional Magnetic Resonance Imaging; Goals; Human; Image; Imaging technology; Knowledge; Magnetic Resonance Imaging; Measurement; Measures; Medical center; Methods; Microscopic; Motor; Motor Cortex; Neurons; Noise; Outcome; Oxygen; Preparation; Protocols documentation; Research; Research Personnel; Resolution; Rest; Sampling; Scanning; Signal Transduction; Specificity; Speed; Techniques; Technology; Testing; Time; Weight; base; blood oxygen level dependent; blood oxygenation level dependent response; brain circuitry; cerebral blood volume; contrast imaging; experimental study; human imaging; image reconstruction; imaging approach; imaging modality; imaging study; improved; next generation; novel; optical imaging; preconditioning; reconstruction; relating to nervous system; response; simulation; spatiotemporal; targeted imaging; temporal measurement; tool; usability; volunteer

PROJECT SUMMARY/ABSTRACT Functional MRI (fMRI) is the most widely-used tool to noninvasively measure brain function and has produced much of our current knowledge about the functional organization of the human brain. However, all fMRI methods measure neuronal activity indirectly by tracking the associated local changes in blood flow, volume and oxygenation, which limit their spatiotemporal specificity to the underlying neuronal activity. While this is often viewed as the fundamental limitation of fMRI, recent optical imaging studies in animal models have shown a tight coupling between microvascular diameter changes and neural activity. These data indicate that human fMRI— as it is performed today—has vast untapped potential that can only be reaped if our measurements can be made sensitive exclusively to changes in these smallest blood vessels. Recent human studies have demonstrated that fMRI based on tracking changes in cerebral blood volume (CBV) with high sensitivity to microvascular diameter changes indeed provide improved neural specificity compared to the conventional blood-oxygenation-level- dependent (BOLD) method. Since the advent of fMRI, BOLD has been the most used fMRI contrast due to its robustness and high sensitivity, yet consensus is building that CBV provides far more faithful measurements of neural activity. Adoption of this powerful non-BOLD fMRI approach has been lacking due to its low sensitivity. To address this, we will develop new imaging methods to dramatically increase sensitivity of CBV-based fMRI. The key to our approach is the recognition that it is now possible, with advanced acquisition methods that we have recently developed, to separate “contrast encoding” in fMRI from image encoding. Because the standard image encoding with EPI in fMRI inherently introduces T2* weighting (and thus BOLD contrast), emerging non-BOLD techniques must inefficiently acquire two sets of data for every measurement to remove the unwanted BOLD contamination in post-processing. The need to acquire two sets of images, along with the necessary post-processing, plus the T2* signal loss combine to cause up to 4× SNR-efficiency loss. Our method, based on our distortion- and blurring-free Echo-Planar Time-resolved Imaging (EPTI) technology, overcomes this SNR loss by eliminating the unwanted BOLD weighting. We call our new framework “Mz fMRI” as it provides a means to generate fMRI contrast based purely on longitudinal magnetization (Mz), applicable to various non- BOLD fMRI methods. We will provide a proof of concept of this powerful framework by integrating EPTI with “VASO” to create an efficient CBV-fMRI without distortion, blurring, or the need for BOLD removal. Our simulations indicate that our approach will deliver sufficient sensitivity for sub-millimeter CBV-fMRI at 3T, and will perform better than existing CBV methods at 7T; the availability of these powerful methods at 3T will open non-BOLD fMRI up to the entire fMRI community, boosting neuronal specificity and enabling broad application of mesoscale fMRI—such as studies of cortical columns and layers and small subcortical nuclei— and thereby opening new possibilities for mapping whole-brain circuitry.

项目概要/摘要 功能性 MRI (fMRI) 是最广泛使用的无创测量脑功能的工具，并已产生 我们目前关于人脑功能组织的大部分知识。然而，所有的功能磁共振成像方法 通过跟踪血流、容量和相关的局部变化来间接测量神经元活动 氧合，限制了它们对潜在神经元活动的时空特异性。虽然这常常是 最近在动物模型中进行的光学成像研究被认为是功能磁共振成像的根本局限性，显示出严格的限制。 微血管直径变化与神经活动之间的耦合。这些数据表明人类功能磁共振成像—— 正如今天所进行的那样——具有巨大的未开发潜力，只有我们能够进行测量才能实现这一潜力 仅对这些最小血管的变化敏感。最近的人类研究表明 基于追踪脑血容量（CBV）变化的功能磁共振成像（fMRI），对微血管直径具有高敏感性 与传统的血氧水平相比，变化确实提供了改进的神经特异性 依赖（粗体）方法。自 fMRI 出现以来，BOLD 一直是最常用的 fMRI 造影剂，因为它具有 鲁棒性和高灵敏度，但人们正在建立共识，即 CBV 可以提供更忠实的测量 神经活动。这种强大的非 BOLD fMRI 方法由于其灵敏度低而一直缺乏采用。 为了解决这个问题，我们将开发新的成像方法来显着提高基于 CBV 的 fMRI 的灵敏度。 我们方法的关键是认识到现在是可能的，先进的采集方法可以 我们最近开发了将功能磁共振成像中的“对比度编码”与图像编码分开的方法。因为 fMRI 中使用 EPI 的标准图像编码本质上引入了 T2* 加权（以及 BOLD 对比度）， 新兴的非 BOLD 技术必须低效地为每次测量获取两组数据以消除 后处理中不必要的 BOLD 污染。需要获取两组图像，以及 必要的后处理，再加上 T2* 信号损失，会导致高达 4 倍的 SNR 效率损失。我们的方法， 基于我们的无失真和模糊回波平面时间分辨成像 (EPTI) 技术，克服了 通过消除不需要的 BOLD 加权来减少 SNR 损失。我们将我们的新框架称为“Mz fMRI”，因为它提供了 一种纯粹基于纵向磁化强度（Mz）生成功能磁共振成像对比的方法，适用于各种非 大胆的功能磁共振成像方法。我们将通过将 EPTI 与 “VASO”创建高效的 CBV-fMRI，不会失真、模糊，也不需要 BOLD 去除。 我们的模拟表明，我们的方法将为亚毫米 CBV-fMRI 提供足够的灵敏度 3T，并且在 7T 时将比现有的 CBV 方法表现更好；这些强大方法在 3T 的可用性将 将非 BOLD fMRI 向整个 fMRI 社区开放，提高神经元特异性并实现广泛 中尺度功能磁共振成像的应用——例如皮质柱和层以及小的皮质下核的研究—— 从而为绘制全脑电路开辟了新的可能性。