Imaging Brain Activation with Steady-State Free Precession MRI

描述（由申请人提供）：功能性磁共振成像（fMRI）通过提供用于监测与脑激活相关的血氧或组织灌注变化的无创工具，彻底改变了神经科学。最常见的方法是血氧依赖（BOLD）成像。不幸的是，提供BOLD中的氧灵敏度的MRI采集参数也产生对图像伪影、信号丢失和空间失真的灵敏度。本提案的目的是开发BOLD的替代品，而不受这些限制。本提案中描述的新方法基于快速、短TR、完全重聚焦成像采集技术中的氧依赖性信号变化，称为稳态自由进动或SSFP。这些方法利用由于氧合变化而引起的稳态信号的变化。一旦已经建立了这种稳态氧合依赖对比度，就可以用任何图像编码方法来捕获它，可以针对效率、分辨率和对伪影的免疫性来选择所述图像编码方法。结果是高分辨率，在大脑的任何区域都是各向同性的，没有信号丢失或空间失真。这将是神经科学家研究大脑激活可用工具的重要补充。具体来说，这个项目的目的是开发两种不同的方法来利用功能磁共振成像的SSFP响应。第一种使用SSFP过渡带的频率灵敏度来检测来自血氧变化的绝对频率偏移。第二个利用氧依赖的表观T2变化的稳态磁化。然后，这些技术将进行评估，并与传统的BOLD在视觉系统的良好特性的研究进行比较。

DESCRIPTION (provided by applicant): Functional magnetic resonance imaging (fMRI) has revolutionized the neurosciences by providing noninvasive tools for monitoring changes in blood oxygenation or tissue perfusion associated with brain activation. The most common approach is blood oxygenation dependent (BOLD) imaging. Unfortunately, the MRI acquisition parameters that provide the oxygen sensitivity in BOLD also produce sensitivity to image artifacts, signal dropouts, and spatial distortion. The aim of this proposal is to develop alternatives to BOLD without these limitations. The new methods described in this proposal are based on oxygen-dependent signal changes in rapid, short TR, fully refocused imaging acquisition techniques, known as steady-state free precession, or SSFP. These approaches exploit the changes in the steady-state signal due to oxygenation changes. Once this steady-state oxygenation dependent contrast has been established, it can be captured with any image encoding method, which can be chosen for efficiency, resolution, and immunity to artifacts. The result is high-resolution, isotropic in any area of the brain, without signal dropouts or spatial distortion. This will be an important addition to the tools available to neuroscientists for studying brain activation. Specifically, this project aims to develop two different approaches for exploiting the SSFP response for fMRI. The first uses the frequency sensitivity of the SSFP transition band to detect absolute frequency shifts from blood oxygenation changes. The second exploits oxygen-dependent apparent T2 changes to the steady state magnetization. These techniques will then be evaluated and compared with conventional BOLD in well characterized studies of the visual system.