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SNR，硬件和脉冲序列的挑战限制了MRSI进入临床使用的渗透，但它仍然是评估大脑功能和持续7T开发的重要动机的最敏感途径。然而，在任何现场强度下，MRSI都面临着光谱质量，可接受的获取时间和空间覆盖范围的挑战。具体而言，虽然3T MRSI在室外位置报道了NAA出色的SNR，但在包括时间和额叶的关键大脑区域的光谱质量方面仍然存在公认的问题。 7T MRS显示了SNR的预期加倍，与3T相比，扫描时间的扫描时间总数较高2倍，其频谱分辨率较高。但是，7T的问题集中在RF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，同时又与等效B1生成所需的功率线性增加。为了在7T处开发和实施MR光谱成像，我们的小组开发了一个收发器检测器，该检测器与RF Shimming一起使用，在7T时表现出了出色的性能。与Resonance Research Inc.合作，我们还表明，通过高阶垫片映射和校正，可以在扩展的大脑区域实现出色的野外同质性。到目前为止，这一成功主要是在单个切片区域实现的。在这个项目中，我们将继续为7T的大脑和多片MRSI开发这项工作。这将通过AIM 1实现，从而扩展了收发器的纵向覆盖范围并进一步提高了BO均匀性，并发展了脉冲序列（基于B1的本地化，Hadamard和Sense编码的AIM 2），我们的目标是高SNR Multi-Slice Multi-Slice Plastroscopic Imaging a Low sarroscopic Imaging a Low sar（〜2W/kg）。 因为理想情况下，方法论发展是现实世界中的，所以我们将使用新皮层癫痫（NE）的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，因此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。在此过程中，很明显，需要在何处放置电极的高级知识，以免“错过”癫痫发作区域。然而，即使有了这一复杂的过程，手术后的结果是约有40-50％的患者继续癫痫发作。随着NE中的病因可变，MRSI覆盖范围存在重大挑战（癫痫发作可能来自任何皮质位置），体积分辨率（典型的ICTAL发作区的典型大小）和最佳的代谢物模式（比NAA更好）。这些未知数可能解释了为什么在3T处常规使用MRSI，而是在解剖学上定义明确的颞叶癫痫中，也存在3T的光谱质量问题。在AIM 3中，我们将检验以下假设：在癫痫发作和传播区域（由ICEEG定义）中，NAA/CR和GLU/CR将异常，从而确定这种鉴定所需的典型素素尺寸，以及NAA或Glutamate是否更准确。为了使这项工作更加实施，AIM 4将使7T确定的参数与纽约大学的O Gonen Phd合作，后者是3T大脑覆盖MRSI的开发和应用领导者。我们将在健康对照组和有限的患者组中比较3T和7T处于3T和7T的延长体积覆盖率，从而使我们能够在3T处定义最佳方法以实现鉴定裂缝区域。 该项目提出了7T MRSI的硬件和脉冲序列中的协调开发。我们认为，该项目的影响很广，不仅是为了改善NE的神经外科管理，而且还用于改善成像和3和7T的MRSI。如前所述，虽然3T MRSI在颞叶中取得了成功，但在颞叶中并不一致。这将通过我们提出的更高垫片和算法的拟议工作来改善，这些工作最佳地纠正和重新分布B0同质性。在7T时，收发器的工作至关重要，因为目前尚无清楚的解决方案解决均质和扩展的RF（〜20UT）覆盖范围的问题。因此，尽管该项目的影响显然是7T MRSI的影响，但B1方法和B0 Shimming中提出的工作将与高领域MR的许多方面高度相关，包括7和3T。