7T MR spectroscopic imaging for human epilepsy

人类癫痫的 7T MR 光谱成像

• 批准号: 8100798
• 负责人: Hoby P Hetherington
• 金额: $ 50.15万
• 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/8100798
• 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 渗透到临床应用，但它仍然是评估脑功能最敏感的途径之一，也是正在进行的 7T 开发的重要动力。然而，在任何场强下，MRSI 都面临着光谱质量、可接受的采集时间和空间覆盖范围的挑战。具体来说，虽然 3T MRSI 报告了室上位置 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 的 SNR 预期翻倍，其光谱分辨率提高了 2 倍以上，与 3T 相比，扫描时间有效减少了 16 倍。然而，7T 的问题主要集中在射频线圈技术和 B0 不均匀性上。在 300MHz 时，组织的介电常数导致明显的轴向和纵向 B1 不均匀性，同时产生等效 B1 所需的功率线性增加。为了开发和实现 7T 磁共振光谱成像，我们小组开发了一种收发器探测器，与射频匀场一起使用，在 7T 下表现出优异的性能。通过与 Resonance Research Inc. 合作，我们还表明，通过高阶匀场映射和校正，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，这一成功主要是在单片区域上实现的。在这个项目中，我们将继续针对 7T 的宽脑和多切片 MRSI 开发这项工作。这将通过目标 1 来实现，目标 1 扩展了收发器的纵向覆盖范围并进一步提高了大体积 Bo 均匀性，目标 2 开发了脉冲序列（基于 B1 的定位、Hadamard 和 SENSE 编码以及 J 重新聚焦采集），我们的目标是低 SAR（~2W/kg）的高 SNR 多层光谱成像。 由于方法学的发展理想地与现实世界的目标一起发生，因此我们将用具有挑战性的新皮质癫痫（NE）问题来测试这些发展。由于许多 NE 患者临床情况复杂，他们的评估通常需要颅内脑电图 (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，显然需要尽可能多的关于放置电极的先进知识，以免“错过”癫痫发作区域。然而，即使经历了这一复杂的过程，术后结果仍是约 40-50% 的患者继续出现严重癫痫发作。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质位置）、体积分辨率（发作区的典型大小）和最佳代谢模式（谷氨酸比 NAA 更好）都面临着重大挑战。这些未知因素可能解释了为什么 MRSI 不常规用于 3T，但即使在解剖学上明确的内侧颞叶癫痫中，3T 也存在光谱质量问题。在目标 3 中，我们将测试以下假设：在癫痫发作和传播区域（由 icEEG 定义），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 宽脑覆盖 MRSI 开发和应用的领导者。我们将比较健康对照和有限患者组中 3T 和 7T 的扩展体积覆盖 MRSI，使我们能够定义 3T 的最佳方法来识别致发区域。 该项目提出了 7T MRSI 硬件和脉冲序列的协调开发。我们相信该项目的影响是广泛的，不仅改善了 NE 的神经外科管理，还改善了 3T 和 7T 的成像和 MRSI。如前所述，3T MRSI 虽然在室上区成功，但在颞叶却不一致。这将通过我们提出的高阶垫片和算法的工作得到改善，这些工作可以最佳地校正和重新分配 B0 同质性。在 7T 时，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同质和扩展射频 (~20uT) 覆盖范围的问题。因此，虽然该项目的影响显然是针对 7T MRSI，但 B1 方法和 B0 匀场的拟议工作将与高场 MR（7 和 3T）的许多方面高度相关。