Biological Spatial Resolution Limits in fMRI

描述（申请人提供）：本项目将支持一名初级教员的培训和职业发展，该教员之前受过计算神经科学和电子工程方面的培训，并将过渡到磁共振成像（MRI）和功能神经成像领域。本次培训将在麻省总医院A. A. Martinos生物医学成像中心进行，由超高场成像和成像物理组的L. L. Wald教授指导。该候选人将进行一项研究，量化功能性MRI空间分辨率的基本生物学极限，并使用开发的新方法对人类视觉系统的功能结构进行精确测量，以克服仪器，数据采集和实验设计以及数据分析所带来的分辨率限制。该项目的长期目标是实现人类视觉皮层精细细节的非侵入性成像，包括定向偏好、眼优势和视网膜切除的独特空间地图，具有足够的空间分辨率，可以对视觉系统的这些基本特征进行精确的定量测量。为了量化空间分辨率的生物学极限，本研究将集中在三个目标上：(i)开发一种量化fMRI空间分辨率和准确性的方法；（ii）测量多个实验设计的空间精度，并确定哪一个提供可实现的最高分辨率；（iii）利用这些知识来测量和量化初级视觉皮层的地形和柱状结构，从而根据已知的测量精度得出关于它们的组织的明智结论。虽然过去已经对空间分辨率进行了估计，但获取和分析技术的新进展以及对实验设计的新见解要求对这些估计进行重新评估，以确定现在可行的方法。重要的是，我们掌握的新兴方法能够解决单个皮质层内的活动。层流功能磁共振成像不仅为测试神经系统和神经血管耦合的新假设提供了可能性，而且所提出的方法可能产生一种实用的技术来提高空间分辨率——由于在大脑脊液远端的中央血管层中预期的更紧密的生物点分布，这些层的目标采样将实现更高的空间分辨率。候选人将接受超高场成像方法、加速并行成像技术、射频线圈探测器的设计和构建、功能磁共振成像数据的精确计算分析以及人脑及其血管系统的解剖学和生理学方面的培训。为本研究开发的工具可用于多种应用，如识别视力缺陷或弱视患者的病理组织，测量枕脑淀粉样血管病患者局部充血的影响，设计皮质假体，并将使未来的神经系统精细组织研究成为可能。

DESCRIPTION (provided by applicant): This project will support the training and career development of a junior faculty member, with prior training in computational neuroscience and electrical engineering, transitioning into the fields of magnetic resonance imaging (MRI) and functional neuroimaging. This training will take place at the A. A. Martinos Center for Biomedical Imaging at the Massachusetts General Hospital, under the mentorship of Prof. L. L. Wald, within the Ultrahigh-field Imaging and Imaging Physics Group. The candidate will conduct a study into quantifying the fundamental biological limits of spatial resolution in functional MRI, and perform precise measurements of the functional architecture of the human visual system using novel methods developed to overcome resolution limits placed by the instrumentation, data acquisition and experimental design, and data analysis. The long-term objective of this project is to enable non-invasive imaging of fine-scale details of the human visual cortex, including the distinctive spatial maps of orientation preference, ocular dominance, and retinotopy, with a spatial resolution sufficient to derive accurate, quantitative measurements of these basic features of the visual system. To quantify the biological limits of spatial resolution, this study will focus on three aims: (i) to develop a methodology for quantifying spatial resolution and accuracy in fMRI; (ii) to measure spatial accuracy across multiple experimental designs and identify which provides the highest achievable resolution; and (iii) to exploit this knowledge to measure and quantify the topographic and columnar structures in primary visual cortex, and thus draw informed conclusions about their organization based on the known measurement accuracy. Although estimates of spatial resolution have been made in the past, new advances in both acquisition and analysis technology, and new insights into experimental design, require that these estimates be re-assessed to determine what is now feasible. Importantly, emerging methods at our disposals enable resolving activity within individual cortical laminae. Not only does laminar fMRI open possibilities for testing new hypotheses about the nervous system and neurovascular coupling, but the proposed methods may yield a practical technique for increasing spatial resolution-due to the tighter biological point-spread expected in central vascular layers distal to large pial veins, targeted sampling of these layers will enable higher achievable spatial resolution. The candidate will receive training in ultrahigh-field imaging methods, accelerated parallel imaging techniques, design and construction of radiofrequency coil detectors, accurate computational analysis of fMRI data, and the anatomy and physiology of the human brain and its vascular system. The tools developed for this study can assist in several applications such as identifying pathological tissue in patients with visual deficits or amblyopia, measuring the impact of localized hyperemia in patients with occipital cerebral amyloid angiopathy, designing cortical prostheses, and will enable future studies into the fine organization of the nervous system.