Parallel MRI for High Field Neuroimaging

描述（由申请人提供）：高场强磁共振成像（MRI）是临床人群非侵入性研究大脑结构和功能的宝贵工具。更高的磁场在功能性磁共振成像（fMRI）中提供更强的噪声信号和增强的对比度。例如，fMRI的使用对于理解奖赏处理和决策的神经机制至关重要，这可能与药物滥用风险的增加有关。了解药物依赖人群大脑回路的改变对于找到有效、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磁场的MRI来研究神经回路和大脑结构，但这些研究受到包括磁化率伪影和射频场不均匀性在内的关键方法限制的严重阻碍。易感性伪影在许多关键的大脑区域产生信号丢失，如腹侧纹状体、杏仁核、眶额皮质、基底神经节和伏隔核。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，提高fMRI对比度所需的高场也会产生较大的图像强度变化和与RF场的波状行为相关的伪影。随着磁场强度的增加，这些问题变得更加严重，目前使得7T等超高场扫描仪无法用于临床。在目前的应用程序中，这是R21-DA15900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下研究大脑能力的解决方案。具体来说，我们将设计、构建和验证多发射机（XSENSE）的使用灵敏度编码，以创建3T定制RF脉冲的实际实现。定制的射频脉冲将用于形成MRI激发，产生具有改进的均匀性和更少的信号损失的切片。我们将把平行传输和平行接收结合起来，进一步提高图像精度。功能磁共振成像和结构磁共振成像的全脑采集将被创建并仔细表征。fMRI序列将允许对下脑区域进行成像，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鲁棒性，并将在7T下进行测试。这些技术将在健康的人类志愿者中进行验证和比较，然后在戒断吸毒者和对照组中进行fMRI奖励回路的试点研究。

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.