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(申请人提供)：虽然信噪比、硬件和脉冲序列的挑战限制了MRSI在临床应用中的渗透，但它仍然是评估大脑功能的最敏感途径之一，也是正在进行的7T开发的重要动机。然而，在任何场强下，MRSI在频谱质量、可接受的捕获时间和空间覆盖方面都面临挑战。具体地说，尽管3T MRSI报告了室上位置NAA的良好SNR，但包括颞叶和额叶在内的关键大脑区域的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，它的光谱分辨率提高了2倍，扫描时间总共减少了16倍。然而，7T的问题集中在射频线圈技术和B0不均匀上。在300 MHz时，组织的介电常数导致显著的轴向和纵向的B1不均匀，同时产生等效B1所需的功率线性增加。为了开发和实现7T下的磁共振光谱成像，我们团队开发了一种收发机探测器，与射频匀场一起使用，在7T下表现出了优异的性能。在与Resonance Research Inc.的合作中，我们还表明，通过更高阶的填隙映射和校正，可以在扩展的大脑区域实现出色的场均匀度。到目前为止，这一成功主要是在单片区域实现的。在这个项目中，我们将继续为7T的宽脑和多层磁共振成像开展这项工作。这将通过目标1和目标2实现，目标1扩展了收发机的纵向覆盖范围，并进一步改善了大容量BO的均匀性，目标2开发了脉冲序列(基于B1的定位、Hadamard和带有J重聚焦采集的感测编码)，我们的目标是在低SAR(~2W/kg)的情况下进行高信噪比多层光谱成像。由于方法学的发展理想地发生在真实世界的靶点上，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患者临床复杂，他们的评估通常需要进行颅内EEG(IcEEG)，这是一种神经外科手术，使用颅内电极来定位癫痫发作。对于这一过程，显然需要更多关于在哪里放置电极的先进知识，以便不“错过”癫痫发作起始区。然而，即使在这个复杂的过程中，手术后的结果是大约40%-50%的患者继续发生严重的癫痫发作。由于NE的病因多种多样，在MRSI的覆盖率(癫痫可发生在任何皮质位置)、体积分辨率(典型的发作区大小)和最佳代谢模式(谷氨酸优于NAA)方面存在重大挑战。这些未知因素可能解释了为什么3T没有常规使用MRSI，但即使在解剖学上定义明确的内侧颞叶癫痫中，3T也存在频谱质量问题。在目标3中，我们将检验一种假设，即在发作开始和传播区域(由icEEG定义)，NAA/Cr和Glu/Cr将异常，从而确定这种识别所需的典型体素大小，以及NAA或谷氨酸可能更准确。为了更好地实施这项工作，AIM 4将采用7T确定的参数，与纽约大学O Gonen博士合作，O Gonen博士是3T广脑覆盖MRSI开发和应用的领先者。我们将在健康对照组和有限的患者组中比较3T和7T的扩展体积覆盖MRSI，使我们能够定义3T的最佳方法来实现ICI区域的识别。本项目提出了一种7T MRSI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，不仅是为了改善NE的神经外科治疗，也是为了改善3T和7T的成像和磁共振成像。如上所述，3TMRSI虽然在室上区获得成功，但在颞叶却不一致。这将随着我们在高阶垫片和算法中提出的工作而得到改进，这些算法最优地校正和重新分配B0同质性。在7T，收发机工作至关重要，因为目前还没有明确的解决方案来解决均匀和扩展RF(~20uT)覆盖的问题。因此，虽然这个项目的影响显然是对7T MRSI，但在B1方法和B0垫片方面的拟议工作将与高场MR的许多方面高度相关，包括7和3T。