Biological Spatial Resolution Limits in fMRI

描述(由申请者提供)：该项目将支持初级教员的培训和职业发展，优先接受计算神经科学和电气工程方面的培训，过渡到磁共振成像(MRI)和功能神经成像领域。培训将在马萨诸塞州总医院的A.A.Martinos生物医学成像中心进行，由L.L.Wald教授指导，隶属于超高场成像和成像物理组。候选人将进行一项研究，以量化功能磁共振空间分辨率的基本生物学极限，并使用为克服仪器、数据采集和实验设计以及数据分析所造成的分辨率限制而开发的新方法，对人类视觉系统的功能架构进行精确测量。该项目的长期目标是实现对人类视觉皮质精细细节的非侵入性成像，包括定向偏好、眼睛优势和视网膜复制的独特空间地图，其空间分辨率足以得出这些视觉系统基本特征的准确、定量测量。为了量化空间分辨率的生物学极限，本研究将集中于三个目标：(I)开发一种量化功能磁共振成像空间分辨率和精度的方法；(Ii)通过多个实验设计测量空间精度，并确定哪种实验设计提供了最高可达到的分辨率；以及(Iii)利用这一知识测量和量化初级视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有意义的结论。尽管过去已经对空间分辨率进行了估计，但采集和分析技术方面的新进展，以及对实验设计的新见解，要求重新评估这些估计，以确定现在可行的估计。重要的是，我们使用的新兴方法能够在单个皮质板层内进行分解活动。层流fMRI不仅为测试神经系统和神经血管耦合的新假说提供了可能性，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-由于预期在大软脑膜静脉远端的中央血管层中更紧密的生物点扩散，这些层的有针对性的采样将使更高的空间分辨率成为可能。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建造、fMRI数据的精确计算分析以及人脑及其血管系统的解剖和生理学方面的培训。为这项研究开发的工具可以帮助几个应用，如识别视力障碍或弱视患者的病理组织，测量枕叶淀粉样脑血管病患者局部充血的影响，设计皮质假体，并将使未来对神经系统精细组织的研究成为可能。 公共卫生相关性：项目叙述功能磁共振成像的空间准确性受到血液输送生物学的限制。我们将沿着大脑皮层施加活动的空间模式，以测量单个大脑皮层的空间准确性，并使用这些模式来测试进一步提高准确性的方法。

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. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE The spatial accuracy of functional MRI is limited by the biology of blood delivery. We will impose spatial patterns of activity along the cortex to measure the spatial accuracy in individual cortical layers, and use these patterns to test methods for further improving accuracy.