Parallel MRI for High Field Neuroimaging

描述（由申请人提供）：高场强下的磁共振成像（MRI）是临床人群无创研究大脑结构和功能的无价工具。更高的磁场提供了更大的信噪比，并增加了功能性MRI（fMRI）的对比度。例如，使用功能磁共振成像对于理解奖励处理和决策的神经机制至关重要，这可能与药物滥用风险增加有关。了解药物依赖人群中改变的脑回路对于找到有效，持久的治疗方法至关重要。虽然现在可以在临床研究中使用高场MRI来研究神经回路和大脑结构，但这些研究受到关键方法学限制的严重阻碍，包括磁化率伪影和RF场不均匀性。敏感性伪影在许多关键的大脑区域产生信号损失，例如腹侧纹状体、杏仁核、眶额皮质、基底神经节和丘脑核。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疾病都至关重要。此外，改善fMRI对比度所需的高场也会产生与RF场的波状行为相关的大的图像强度变化和伪影。这些问题随着场强的增加而变得更糟，并且目前使得超高场扫描仪（诸如7 T）对于临床使用不切实际。在本申请中，这是R21-DA 15900的延续，我们的研究小组将解决这些技术限制，并开发和验证旨在提高我们在高场研究大脑的能力的解决方案。具体而言，我们将设计、构建和验证使用多发射机灵敏度编码（XSENSE），以创建3 T定制RF脉冲的实际实现。定制的RF脉冲将用于塑造MRI激励，产生具有改善的均匀性和更少的信号损失的切片。我们将结合联合收割机并行传输与并行接收，以进一步改善图像精度。将创建用于功能性MRI和结构性MRI的全脑采集并仔细表征。功能磁共振成像序列将允许对大脑下部区域进行成像，使新的临床应用成为可能。结构MRI序列将对射频场不均匀性具有稳健性，并将在7 T下进行测试。这些技术将在健康的志愿者中进行验证和比较，然后在一项关于戒断药物使用者和对照人群的奖励回路的fMRI试点研究中进行验证和比较。

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.