Three-Dimensional Patient-Tailored RF Pulses for Spin Echo Neuroimaging at 7 T

用于 7 T 自旋回波神经成像的三维患者定制射频脉冲

基本信息

批准号：
8697577
负责人：
William A Grissom
金额：
$ 36.18万
依托单位：
VANDERBILT UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-04-10 至 2018-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8697577
关键词：
Address Adoption Algorithm Design Algorithms Attenuated Brain Brain imaging Cervical spinal cord structure Clinical Computer software Data Deposition Development Diagnostic Diffusion Diffusion Magnetic Resonance Imaging Electromagnetic Fields Engineering Fatty acid glycerol esters Fiber Frequencies Functional Magnetic Resonance Imaging Goals Image Joints Liquid substance Magnetic Resonance Imaging Maps Methods Metric Modality Neck Neuraxis Noise Pathology Patients Performance Phase Physiologic pulse Protocols documentation Recovery Research Personnel Resolution Scanning Signal Transduction Slice Speed Structure Techniques Thick Time Variant blood oxygen level dependent cohort design flexibility imaging modality improved interest meetings method development neuroimaging non-invasive imaging novel patient safety practical application public health relevance radiofrequency relating to nervous system spinal cord imaging transmission process

项目摘要

DESCRIPTION (provided by applicant): The goal of this project is to develop new technical approaches to mitigate the effects of severely inhomogeneous and patient-dependent RF transmission (B+) fields that limit ultra-high field MRI, with particular emphasis on spin 1 echo and fast spin echo (FSE) neuroimaging at 7 Tesla (T). Our approaches comprise new techniques for patient- tailored single-channel and parallel excitation, including trajectory designs and pulse design algorithms, in spin echo acquisitions of high importance at 7 T. These methods will be essential to realizing the improvements in SNR and resolution, and exploiting the distinct contrast mechanisms that 7 T MRI promises. They stand to enhance the quality of spin echo MRI at lower clinical field strengths, and have broad impact in practical applications. Three imaging methods that stand to benefit greatly from 7 T are FSE acquisitions such as fluid-attenuated inversion recovery (FLAIR), diffusion tensor imaging (DTI), and blood oxygenation level-dependent (BOLD) functional MRI (fMRI). FSE sequences are key for imaging pathologies of the central nervous system, while DTI and BOLD fMRI have revolutionized structural and functional connectivity studies. However, at low field these sequences are hampered by limited SNR and spatial resolution (FSE and DTI), and intravascular contamination (BOLD). At 7 T, FSE and DTI data can be acquired with higher SNR and spatial resolution, and Hahn spin echo (HSE) BOLD fMRI can be used to obtain functional signals that can much more accurately localize neural activation. Unfortunately, because patient-dependent B+ field inhomogeneity causes flip angle inhomogeneity, 1 the quality of spin echo acquisitions at 7 T is currently severely limited. Recently, patient-tailored single-channel and parallel excitation methods have been developed to mitigate the effect of B+ inhomogeneity, and the basic 1 hardware and software required by these methods is becoming standard on 7 T scanners. However, there has been little development of these methods for the large-tip-angle excitations required by spin echo acquisitions. This project will address this gap in development. We will develop new three-dimensional excitation k-space trajectories for large-tip-angle slice-selective excitation, and new pulse design algorithms to design excitation and refocusing pulses using those trajectories. We will improve upon the current dominant 'spokes' trajectory, which is generally unsuitable for large-tip-angle slice-selective excitations due to the high power of spokes RF pulses. We hypothesize that alternative trajectories exist that can provide improved spatial encoding capabilities with higher spectral bandwidths that are minimally impacted by reshaping to reduce RF power deposition, and with improved flexibility in selecting slice thickness and sharpness. Our pulse design methods will enable the joint design of excitation and refocusing pulses to meet the unique demands of spin echo imaging sequences, and will not only improve the pulses' performance, but will also add to their capabilities. We will evaluate the performance of our patient-tailored pulses in FSE, DTI and HSE BOLD fMRI acquisitions, using data and image quality metrics specific to those modalities.

描述（由申请人提供）：该项目的目标是开发新技术方法，以减轻严重不均匀和依赖于患者的射频传输 (B+) 场的影响，这些场限制超高场 MRI，特别强调自旋 1 回波以及 7 特斯拉 (T) 的快速自旋回波 (FSE) 神经成像。我们的方法包括针对患者定制的单通道和并行激励的新技术，包括轨迹设计和脉冲设计算法，在 7 T 的自旋回波采集中非常重要。这些方法对于实现 SNR 和分辨率的改进至关重要，并且利用 7 T MRI 所承诺的独特对比机制。它们能够在较低的临床场强下提高自旋回波 MRI 的质量，并在实际应用中产生广泛的影响。从 7 T 中受益匪浅的三种成像方法是 FSE 采集，例如流体衰减反转恢复 (FLAIR)、扩散张量成像 (DTI) 和血氧水平依赖 (BOLD) 功能 MRI (fMRI)。 FSE 序列是中枢神经系统成像病理学的关键，而 DTI 和 BOLD fMRI 彻底改变了结构和功能连接研究。然而，在低场下，这些序列受到有限的 SNR 和空间分辨率（FSE 和 DTI）以及血管内污染（BOLD）的阻碍。在 7 T 下，可以以更高的 SNR 和空间分辨率获取 FSE 和 DTI 数据，并且可以使用哈恩自旋回波 (HSE) BOLD fMRI 来获取可以更准确地定位神经激活的功能信号。不幸的是，由于患者相关的 B+ 场不均匀性导致翻转角不均匀性，1 目前 7 T 下的自旋回波采集质量受到严重限制。最近，开发了针对患者的单通道和并行激励方法，以减轻 B+ 不均匀性的影响，这些方法所需的基本 1 硬件和软件正在成为 7 T 扫描仪的标准配置。然而，对于自旋回波采集所需的大尖端角激励，这些方法几乎没有发展。该项目将解决这一发展差距。我们将开发新的三维激励 k 空间轨迹，用于大顶角切片选择性激励，以及新的脉冲设计算法，使用这些轨迹设计激励和重新聚焦脉冲。我们将改进当前占主导地位的“辐条”轨迹，由于辐条射频脉冲的高功率，该轨迹通常不适合大尖端角切片选择性激励。我们假设存在替代轨迹，可以提供改进的空间编码能力，具有更高的频谱带宽，并且在选择切片厚度和清晰度方面具有更高的灵活性，并且受整形影响最小，以减少射频功率沉积。我们的脉冲设计方法将能够联合设计激发和重聚焦脉冲，以满足自旋回波成像序列的独特需求，不仅会提高脉冲的性能，还会增强其功能。我们将使用特定于这些模式的数据和图像质量指标来评估患者定制脉冲在 FSE、DTI 和 HSE BOLD fMRI 采集中的性能。