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.

项目摘要 该项目的目的是为反式传输（PTX）开发一个框架 与各种MRI扫描仪相处，并将其应用于推动空间编码限制的Echo Planar成像限制 （EPI）在7特斯拉。 EPI是迄今为止最广泛使用的脉冲序列，用于快速功能，扩散和灌注 成像，近年来一直是考虑发展的重点，以提高其速度和空间 解决。现在，人们强烈希望将EPI的空间分辨率推向微观量表。用于功能 MRI（fMRI），这将使皮质和皮层的细胞结构成像（层，柱和核）成像 在更好地解决血液动力学反应的同时。对于扩散MRI（DMRI），微尺度EPI将 改善皮质中纤维的表面和层流分析，以及使用分数各向异性的脑包裹 灰质区域之间的差异，同时广泛降低了部分体积的影响。它将进一步启用 EPI将广泛应用于加速与fMRI和DMRI扫描匹配的解剖扫描。 但是，增加单发epi的分辨率需要更长的读数，以扩展回声时间并重新 fMRI中的Duce功能对比和DMRI在7 Tesla中的信噪比，同时增加了几何变形 和模糊。分段或多曲EPI是增加空间分辨率而不增加空间分辨率的经典方法 读数持续时间，但主要是由于其对运动和动态相变的高灵敏度 在引起大图像的镜头之间。 我们建议开发一种称为Chattered Epi的新的多疗法EPI技术，该技术解决了LIM- 传统多曲EPI的效率通过在每个镜头中对一组空间不相交的百叶窗进行成像。百叶窗 由多维刺激的脉搏产生，并在镜头之间空间移动以覆盖整个 片。然而，刺激脉冲的长度是不切实际的（20-100毫秒）。多层PTX（> 8个线圈）可以将这些脉冲的长度缩短到可行的持续时间，但是当前的7个特斯拉扫描仪只有8个 由于成本，足迹，电缆和其他限制因素而发送通道。在第一个项目时期，我们开创了 称为阵列压缩PTX（ACPTX）的技术，它克服了此限制。使用ACPTX，8传输Chan- NELS可以控制一个任意数量的线圈，其中通道和线圈通过数组连接 用RF脉冲进行优化的压缩网络，以进行特定兴奋。在这个项目中，我们将开发并 应用ACPTX方法和硬件（多型线头传输阵列以及8个通道到许多线圈阵列com- 压力网络）以达到可行的RF脉冲持续时间 EPI。这些发展将在两个主要的7T扫描仪平台上实施，并在亚毫米表中进行评估 （600微米）fMRI和DMRI采购。总体而言，该项目涵盖了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。