7T MR spectroscopic imaging for human epilepsy

人类癫痫的 7T MR 光谱成像

• 批准号: 8249832
• 负责人: Hoby P Hetherington
• 金额: $ 50.47万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-01 至 2015-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8249832
• 关键词: Acute; Address; Algorithms; Anatomy; Brain; Brain region; Cerebrum; Chemicals; Clinical; Collaborations; Complex; Data Quality; Deposition; Development; Disease; Doctor of Philosophy; Electrodes; Electroencephalography; Epilepsy; Etiology; Evaluation; Functional disorder; Generations; Glutamates; Goals; Health; Human; Hybrids; Image; Knowledge; Lipids; Location; Magnetic Resonance Imaging; Maps; Measurement; Medial; Methods; Monitor; Morphologic artifacts; Motivation; Neurosurgical Procedures; New York; Operative Surgical Procedures; Outcome; Patients; Pattern; Penetration; Performance; Physiologic pulse; Predisposition; Process; RF coil; Reporting; Research; Resolution; Scanning; Seizures; Signal Transduction; Slice; Solutions; Surface; System; Technology; Temporal Lobe; Temporal Lobe Epilepsy; Testing; Time; Tissues; Tonic-Clonic Epilepsy; Ventricular; Weight; Work; base; coping; detector; frontal lobe; imaging modality; improved; insight; neocortical; reconstruction; research clinical testing; spectroscopic imaging; success

DESCRIPTION (provided by applicant): While challenges of SNR, hardware, and pulse sequence have limited the penetration of MRSI into clinical use, it remains among the most sensitive avenues towards assessing cerebral function and an important motivation for ongoing 7T development. However at any field strength, MRSI has challenges for spectral quality, acceptable acquisition time and spatial coverage. Specifically, while 3T MRSI has reported excellent SNR for NAA in supraventricular locations, there remain acknowledged problems for spectral quality in critical brain regions including the temporal and frontal lobes. 7T MRS has shown the expected doubling in SNR, which with the >2-fold greater spectral resolution effectively gives a total 16x reduction for scan time in comparison to 3T. However, problems at 7T focus on rf coil technology and B0 inhomogeneity. At 300MHz, the dielectric constant of tissue results in marked axial and longitudinal B1 inhomogeneities, simultaneous to a linear increase in required power for equivalent B1 generation. With a goal of developing and implementing MR spectroscopic imaging at 7T, our group has developed a transceiver detector which as used with RF shimming, has shown excellent performance at 7T. In collaboration with Resonance Research Inc., we have also shown that with higher order shim mapping and corrections, outstanding field homogeneity can be achieved over extended brain regions. Thus far this success has been primarily achieved over single slice regions. In this project, we will continue to develop this work for wide brain and multi-slice MRSI at 7T. This will be achieved through Aim 1 that extends the longitudinal coverage of the transceiver and further improves large volume Bo homogeneity, and Aim 2 which develops the pulse sequences (B1 based localization, Hadamard and SENSE encoding with the J-refocused acquisition), our goal being high SNR multi-slice spectroscopic imaging with low SAR (~2W/kg). Because methodologic development ideally occurs with real-world targets, we will test these developments with the challenging problem of neocortical epilepsy (NE). Since many NE patients are clinically complex, their evaluation commonly requires intracranial EEG (icEEG), a neurosurgical procedure where intracranial electrodes are used to localize seizures. For this process, it is clear that as much advanced knowledge on where to place electrodes is needed, so as to not "miss" the seizure onset zone. Yet even with this complex process, the post-surgical outcome is that ~40-50% of patients continue with significant seizures. With the variable etiologies in NE, there are major challenges for MRSI coverage (seizures can arise from any cortical location), volume resolution (typical size of ictal onset zone), and optimal metabolite pattern (is glutamate better than NAA). These unknowns likely explain why MRSI is not routinely used at 3T, but even in anatomically well defined medial temporal lobe epilepsy, there are spectral quality problems at 3T. In Aim 3, we will test the hypothesis that in regions of seizure onset and propagation (as defined by icEEG) the NAA/Cr and Glu/Cr will be abnormal, thus determining the typical voxel size needed for such identification, and whether NAA or glutamate may be more accurate. To bring this work into greater implementation, Aim 4 will take the parameters identified at 7T into a collaboration with O Gonen PhD, New York Univ., a leader in the development and application of 3T wide brain coverage MRSI. We will compare extended volume coverage MRSI at 3T and 7T in healthy controls and in a limited group of patients, allowing us to define the optimum methods at 3T to achieve identification of ictogenic regions. This project proposes a coordinated development in hardware and pulse sequences for 7T MRSI. We believe that this project's impact is broad, not just for improved neurosurgical management of NE, but also for improved imaging and MRSI at 3 and 7T. As stated, 3T MRSI, while successful for supra- ventricular regions, is inconsistent in the temporal lobes. This will improve with our proposed work in higher order shims and algorithms that optimally correct for and redistribute B0 homogeneity. At 7T, the transceiver work is critical as presently there is no clear solution to the problem of homogeneous and extended rf (~20uT) coverage. Thus while the impact of this project is clearly for 7T MRSI, the proposed work in B1 methods and B0 shimming will be highly relevant for many aspects of high field MR, both 7 and 3T.

描述（由申请人提供）：虽然信噪比、硬件和脉冲序列的挑战限制了核磁共振成像在临床应用中的渗透，但它仍然是评估大脑功能最敏感的途径之一，也是正在进行的7T发展的重要动力。然而，在任何场强下，MRSI在频谱质量、可接受的采集时间和空间覆盖方面都存在挑战。具体来说，虽然3T MRSI已经报道了脑室上位置NAA的出色信噪比，但在包括颞叶和额叶在内的关键大脑区域，频谱质量仍然存在公认的问题。7T MRS显示出预期的信噪比翻倍，与3T相比，光谱分辨率提高了2倍，有效地将扫描时间减少了16倍。然而，7T的问题主要集中在射频线圈技术和B0的不均匀性上。在300MHz时，组织的介电常数导致显著的轴向和纵向B1不均匀性，同时产生等效B1所需的功率呈线性增加。为了开发和实现7T的MR光谱成像，我们小组开发了一种与射频闪烁一起使用的收发器探测器，在7T下表现出优异的性能。在与共振研究公司的合作中，我们还表明，通过更高阶的垫片映射和校正，可以在扩展的大脑区域上实现出色的场均匀性。到目前为止，这种成功主要是在单片区域取得的。在这个项目中，我们将继续在7T的宽脑和多层核磁共振成像中开展这项工作。这将通过Aim 1扩展收发器的纵向覆盖范围并进一步改善大体积波均匀性来实现，Aim 2开发脉冲序列（基于B1的定位，Hadamard和SENSE编码与j重聚焦采集），我们的目标是低SAR （~2W/kg）的高信噪比多层光谱成像。由于方法的发展理想地发生在现实世界的目标上，我们将用新皮质癫痫（NE）这一具有挑战性的问题来测试这些发展。由于许多NE患者在临床上很复杂，他们的评估通常需要颅内脑电图（icEEG），这是一种神经外科手术，使用颅内电极来定位癫痫发作。在这个过程中，很明显需要尽可能多的关于电极放置位置的先进知识，这样才不会“错过”癫痫发作区域。然而，即使有了这个复杂的过程，术后的结果是约40-50%的患者继续出现明显的癫痫发作。由于NE的病因多变，mri覆盖范围（癫痫发作可发生在任何皮质部位）、体积分辨率（癫痫发作区典型大小）和最佳代谢物模式（谷氨酸优于NAA）存在重大挑战。这些未知因素可能解释了为什么mri不能常规用于3T，但即使在解剖学上定义明确的内侧颞叶癫痫中，3T的频谱质量也存在问题。在Aim 3中，我们将检验在癫痫发作和传播区域（由icEEG定义）NAA/Cr和Glu/Cr将异常的假设，从而确定这种识别所需的典型体素大小，以及NAA或谷氨酸是否可能更准确。为了使这项工作得到更大的实施，Aim 4将把7T时确定的参数与纽约大学的O Gonen博士合作，他是开发和应用3T全脑覆盖核磁共振成像的领导者。我们将比较健康对照和有限患者组在3T和7T时的扩展体积覆盖MRSI，使我们能够确定3T时的最佳方法，以实现ictogenic区域的识别。本项目提出了7T核磁共振成像硬件和脉冲序列的协调发展。我们相信这个项目的影响是广泛的，不仅对改善神经外科治疗NE，而且对改善成像和mri在3和7T。如前所述，3T磁共振成像虽然在脑室上区域是成功的，但在颞叶中是不一致的。这将通过我们在高阶垫片和算法中提出的工作来改善，这些算法可以最佳地纠正和重新分配B0均匀性。在7T时，收发器工作是至关重要的，因为目前还没有明确的解决方案来解决均匀和扩展rf （~20uT）覆盖的问题。因此，虽然该项目对7T磁共振成像的影响明显，但B1方法和B0 shimming的拟议工作将与高场磁共振成像的许多方面高度相关，包括7和3T。