Array-Compressed Parallel Transmission for High Resolution Neuroimaging at 7T

用于 7T 高分辨率神经成像的阵列压缩并行传输

• 批准号: 10093035
• 负责人: William A Grissom
• 金额: $ 37.88万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-10 至 2023-01-01
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10093035
• 关键词: 3-Dimensional; Address; Algorithms; Anatomy; Anisotropy; Architecture; Biological; Brain; Brain imaging; Cell Nucleus; Data; Development; Diffusion; Diffusion Magnetic Resonance Imaging; Echo-Planar Imaging; Elements; Fiber; Functional Magnetic Resonance Imaging; Funding; Goals; Head; Homebound Persons; Image; Image Enhancement; Imaging Techniques; Length; MRI Scans; Machine Learning; Magnetic Resonance Imaging; Measurement; Methods; Morphologic artifacts; Motion; Noise; Patients; Pattern; Performance; Phase; Physiologic pulse; Physiological; Problem Formulations; Relaxation; Research Project Grants; Resolution; Scanning; Shapes; Signal Transduction; Slice; Speed; Structure; Surface; System; Techniques; Thinness; Time; base; blood oxygen level dependent; cost; design; gray matter; hemodynamics; image reconstruction; improved; magnetic field; motion sensitivity; neuroimaging; perfusion imaging; phase change; reconstruction; response; simulation; spectroscopic imaging; time use; transmission process; virtual

Project Summary The goal of this project is to develop a framework for high-performance parallel transmission (pTx) that is trans- ferable to a wide range of MRI scanners, and apply it to push the spatial encoding limits of echo planar imaging (EPI) at 7 Tesla. EPI is by far the most widely used pulse sequence for rapid functional, diffusion, and perfusion imaging, and has been the focus of considerable development in recent years to increase its speed and spatial resolution. Now there is a strong desire to push EPI's spatial resolution down to the micro scale. For functional MRI (fMRI), this would enable imaging of fine structures (layers, columns, and nuclei) of cortical and subcortical architecture while better resolving the hemodynamic response. For diffusion MRI (dMRI), micro scale EPI would improve surface and laminar analysis of fibers in the cortex, as well as brain parcelation using fractional anisotropy differences between gray matter regions, while broadly reducing partial volume effects. It would further enable EPI to be broadly applied to accelerate anatomic scans that are geometrically matched to fMRI and dMRI scans. However, increasing the resolution of single-shot EPI requires longer readouts which extend echo times and re- duce functional contrast in fMRI and signal-to-noise in dMRI at 7 Tesla, while increasing geometric distortions and blurring. Segmented or multishot EPI is a classic method to increase spatial resolution without increasing readout durations, but is underutilized, primarily due to its high sensitivity to motion and dynamic phase changes between shots which cause large image artifacts. We propose to develop a new multishot EPI technique called shuttered EPI, which addresses the lim- itations of conventional multishot EPI by imaging a set of spatially disjoint shutters in each shot. The shutters are produced by a multidimensional excitation pulse and are spatially shifted between shots to cover an entire slice. However, with thin slices the length of the excitation pulses are impractical (20-100 ms). Many-coil pTx (> 8 coils) can shorten the length of these pulses to feasible durations, but current 7 Tesla scanners have only 8 transmit channels due to cost, footprint, cabling, and other constraints. In the first project period we pioneered a technique called array-compressed pTx (acpTx) which overcomes this limitation. Using acpTx, 8 transmit chan- nels can control an arbitrarily large number of coils, where the channels and coils are connected via an array compression network that is optimized with RF pulses for specific excitations. In this project, we will develop and apply acpTx methods and hardware (a many-coil head transmit array and an 8 channel-to-many coil array com- pression network) to achieve feasible RF pulse durations when exciting the shutter patterns required for shuttered EPI. These developments will be implemented on two major 7T scanner platforms and evaluated in submillimeter (600 micron) fMRI and dMRI acquisitions. Overall, the project encompasses the synergistic design of RF pulses, hardware, acquisitions and reconstructions to achieve a major advance in spatial encoding.

项目概要 该项目的目标是开发一个高性能并行传输（pTx）框架 适用于各种 MRI 扫描仪，并应用它来突破回波平面成像的空间编码极限 (EPI) 7 特斯拉 EPI 是迄今为止用于快速功能、扩散和灌注的最广泛使用的脉冲序列。 成像，并且近年来一直是相当大发展的焦点，以提高其速度和空间 现在人们强烈希望将 EPI 的空间分辨率降低到微观尺度。 MRI (fMRI)，这将能够对皮质和皮质下的精细结构（层、柱和核）进行成像 对于扩散 MRI (dMRI)，微型 EPI 可以更好地解决血流动力学响应问题。 使用分数各向异性改进皮层纤维的表面和层流分析以及大脑分区 灰质区域之间的差异，同时广泛减少部分体积效应。 EPI 将广泛应用于加速与 fMRI 和 dMRI 扫描几何匹配的解剖扫描。 然而，提高单次 EPI 的分辨率需要更长的读数，这会延长回波时间并重新 在 7 特斯拉时，减少 fMRI 中的功能对比度和 dMRI 中的信噪比，同时增加几何失真 分段或多镜头 EPI 是在不增加空间分辨率的情况下提高空间分辨率的经典方法。 读出持续时间，但未得到充分利用，主要是由于其对运动和动态相位变化的高敏感性 镜头之间的干扰会导致较大的图像伪影。 我们建议开发一种新的多镜头 EPI 技术，称为快门 EPI，它解决了 通过在每个镜头中对一组空间不相交的快门进行成像来实现传统多镜头 EPI 的迭代。 由多维激励脉冲产生，并在发射之间进行空间移动以覆盖整个 然而，对于薄片，激励脉冲的长度是不切实际的（20-100 ms）。 8 个线圈）可以将这些脉冲的长度缩短到可行的持续时间，但当前的 7 Tesla 扫描仪只有 8 个线圈 由于成本、占地面积、布线和其他限制，我们在第一个项目期间开创了一种传输通道。 称为阵列压缩 pTx (acpTx) 的技术克服了这一限制，使用 acpTx，8 个传输通道。 nels 可以控制任意数量的线圈，其中通道和线圈通过阵列连接 在这个项目中，我们将开发和优化针对特定激励的射频脉冲的压缩网络。 应用 acpTx 方法和硬件（多线圈头发射阵列和 8 通道对多线圈阵列组成） 压力网络），以在激发快门所需的快门模式时实现可行的射频脉冲持续时间 EPI。这些开发将在两个主要的 7T 扫描仪平台上实施，并以亚毫米级进行评估。 （600 微米）fMRI 和 dMRI 采集总体而言，该项目包括 RF 脉冲的协同设计， 硬件、采集和重建以实现空间编码的重大进步。