7T MR spectroscopic imaging for human epilepsy

人类癫痫的 7T MR 光谱成像

• 批准号: 8655416
• 负责人: Hoby P Hetherington
• 金额: $ 51.34万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 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/8655416
• 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SNR、硬件和脉冲序列的挑战限制了MRSI在临床应用中的渗透，但它仍然是评估脑功能的最敏感途径之一，也是正在进行的7 T开发的重要动机。然而，在任何场强下，MRSI在光谱质量、可接受的采集时间和空间覆盖方面都存在挑战。具体而言，虽然3 T MRSI报告了室上性位置中NAA的出色SNR，但在包括颞叶和额叶在内的关键脑区域中仍存在公认的频谱质量问题。7 T MRS显示出预期的SNR加倍，与3 T相比，其具有>2倍的更高光谱分辨率，有效地使扫描时间减少了16倍。然而，7 T的问题集中在射频线圈技术和B 0不均匀性上。在300 MHz下，组织的介电常数导致显著的轴向和纵向B1不均匀性，同时等效B1生成所需功率线性增加。为了开发和实现7 T下的MR光谱成像，我们的团队开发了一种收发器探测器，该探测器与RF匀场一起使用，在7 T下表现出出色的性能。与Resonance Research Inc.合作，我们还表明，利用更高阶的匀场映射和校正，可以在扩展的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切片区域上实现的。在这个项目中，我们将继续发展这项工作的宽脑和多层面MRSI在7 T。这将通过目标1和目标2实现，目标1扩展收发器的纵向覆盖范围并进一步改善大体积Bo均匀性，目标2开发脉冲序列（基于B1的定位、Hadamard和SENSE编码以及J重聚焦采集），我们的目标是低SAR（~ 2 W/kg）的高SNR多切片光谱成像。 由于方法学的发展理想地发生在现实世界的目标，我们将测试这些发展与新皮质癫痫（NE）的挑战性问题。由于许多NE患者临床上很复杂，他们的评估通常需要颅内EEG（icEEG），这是一种使用颅内电极定位癫痫发作的神经外科手术。对于这个过程，很明显，需要关于在哪里放置电极的尽可能多的先进知识，以便不“错过”癫痫发作区。然而，即使有这个复杂的过程，手术后的结果是，约40-50%的患者继续严重癫痫发作。由于NE的病因多种多样，MRSI覆盖范围（癫痫发作可能发生在任何皮层位置）、体积分辨率（发作起始区的典型大小）和最佳代谢模式（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MRSI在3 T下不被常规使用，但即使在解剖学上定义良好的内侧颞叶癫痫中，3 T下也存在频谱质量问题。在目标3中，我们将检验以下假设：在癫痫发作和传播的区域（如icEEG所定义）中，NAA/Cr和Glu/Cr将异常，从而确定此类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好的实施，Aim 4将与纽约大学的O Gonen博士合作，在3 T宽脑覆盖MRSI的开发和应用方面处于领先地位。我们将在健康对照和有限的患者组中比较3 T和7 T下的扩展体积覆盖MRSI，使我们能够定义3 T下的最佳方法来识别致癫痫区域。 本项目提出了7 T MRSI硬件和脉冲序列的协调发展。我们相信，该项目的影响是广泛的，不仅是为了改善NE的神经外科管理，而且还为改善成像和MRSI在3和7 T。如前所述，3 T MRSI，而成功的室上区，是不一致的颞叶。这将改善我们提出的工作，在更高的顺序和算法，最佳地纠正和重新分配B 0的均匀性。在7 T下，收发器工作至关重要，因为目前还没有明确的解决方案来解决均匀和扩展的rf（~ 20 uT）覆盖的问题。因此，虽然该项目的影响显然是针对7 T MRSI，但B1方法和B 0匀场的拟议工作将与7 T和3 T高场MR的许多方面高度相关。