Parallel MRI for High Field Neuroimaging

描述(申请人提供)：高场强磁共振成像(MRI)是在临床人群中非侵入性研究大脑结构和功能的无价工具。在功能磁共振成像(FMRI)中，较高的磁场提供更高的信噪比和更高的对比度。例如，功能磁共振成像的使用对于理解奖励处理和决策背后的神经机制至关重要，这可能与药物滥用风险的增加有关。了解药物依赖人群中大脑回路的变化对于寻找有效、持久的治疗方法至关重要。虽然现在在临床研究中可以使用高场磁共振来研究神经回路和脑结构，但这些研究受到关键的方法学限制，包括磁化率伪影和射频场不均匀。易感性伪影会在许多关键的脑区，如腹侧纹状体、杏仁核、眶前皮质、基底节和伏隔核产生信号丢失。所有这些区域对于理解奖赏和成瘾以及许多其他神经精神障碍都是至关重要的。此外，提高fMRI对比度所需的高场也会产生巨大的图像强度变化和与射频场的波动行为相关的伪影。这些问题随着磁场强度的增加而变得更糟，目前使超高场扫描仪(如7T)无法用于临床。本应用是R21-DA15900的延续，我们的研究团队将解决这些技术限制，并开发和验证旨在提高我们在高场下研究大脑的能力的解决方案。具体地说，我们将设计、构建和验证使用敏感度编码和多发射机(XSense)，以创建在3T的定制RF脉冲的实际实施。定制的RF脉冲将被用来整形MRI激励，产生具有更好的均质性和更少的信号损失的切片。我们将并行传输和并行接收相结合，以进一步提高图像精度。将创建用于功能磁共振成像和结构磁共振成像的全脑采集并仔细描述其特征。功能磁共振成像序列将允许对下部大脑区域进行成像，使新的临床应用成为可能。结构磁共振序列将对射频场不均匀具有很强的耐受性，并将在7T下进行测试。这些技术将在健康的人类志愿者身上进行验证和比较，然后在戒毒者和对照组人群中进行的fMRI奖励回路试点研究中进行。

DESCRIPTION (provided by applicant): Magnetic Resonance Imaging (MRI) at high field strengths is a n invaluable tool for non-invasively studying brain structure and function in clinical populations. Higher magnetic fields provide greater signal to noise and increased contrast in functional MRI (fMRI). For example, the use of fMRI is crucial for understanding the neural mechanisms underlying reward processing and decision-making, which are likely to be associated with an increased risk of drug abuse. Understanding the altered brain circuitry in populations with drug dependencies is vital to finding effective, lasting treatments. Although it has now possible to use MRI at high fields to investigate neural circuitry and brain structure in clinical research, these studies are severely hampered by critical methodological limitations including magnetic susceptibility artifacts and RF field inhomogeneity. Susceptibility artifacts produce signal loss in many key brain regions such as the ventral striatum, amygdala, orbitofrontai cortex, basal ganglia, and nucleus accumbens. All of these regions are vital to understanding reward and addiction as well as numerous other neuropsychiatric disorders. Furthermore, the high fields needed for improved fMRI contrast also produce large image intensity variations and artifacts associated with the wavelike behavior of the RF field. These problems become worse as the field strength increases and currently leave ultra-high field scanners such as 7T impractical for clinical use. In the present application, which is a continuation of R21-DA15900, our group of investigators will tackle these technical limitations and develop and validate solutions designed to improve our ability to investigate the brain at high field. Specifically, we will design, build, and validate the use sensitivity encoding with multiple transmitters (XSENSE) to create practical implementations of tailored RF pulses at 3T. The tailored RF pulses will be used to shape MRI excitations, producing slices with improved homogeneity and less signal loss. We will combine parallel transmission with parallel reception for further refinements in image accuracy. Whole brain acquisitions for fMRI and structural MRI will be created and carefully characterized. The fMRI sequence will allow for the imaging of inferior brain regions, making new clinical applications possible. The structural MRI sequence will be robust to RF field inhomogeneity and will be tested at 7T as well. The techniques will be validated and compared in healthy human volunteers and then in an fMRI pilot study of the reward circuit in a population of abstinent drug users and controls.