Multi-coil Shimming of the Human Brain at 7 Tesla

描述（由申请人提供）：许多磁共振（MR）模态，如功能性MR成像（MRI）、弥散MRI和MR波谱（MRS），在研究和诊断脑部疾病和损伤以及指导手术治疗方面具有巨大潜力。所有这些 这些方法极大地受益于来自高场强磁体（3T及以上）的增加的灵敏度、分辨率和对比度。然而，由于空气和组织之间的磁化率差异引起的磁场不均匀性的日益混杂的影响，较高磁场的优点尚未完全实现。磁场不均匀性导致MRI中的信号损失和空间失真以及MRS中的光谱分辨率和灵敏度损失。由于这些伪影而导致的可靠性损失是这些技术在高场临床应用中没有广泛使用的主要原因。目前基于球面谐波匀场线圈的磁场均匀化方法在小体积上表现良好，但不足以补偿整个人脑的复杂磁场分布。在这里，提出了一种基于DC线圈矩阵的新技术，该技术可以在体内人脑中实现上级匀场性能。初步结果表明，多线圈（MC）矩阵匀场在7.0 T的人脑的可行性。将建立MC矩阵的静态和时间特性的表征，以及与RF线圈的集成。本申请提出将MC矩阵匀场开发到可以以稳健和自动化的方式在7 T下获得整个人脑的出色磁场均匀性的程度，以与任何现有的临床MR协议一起使用。具体而言，该应用程序由三个目标组成，重点是在7 T条件下优化用于人脑应用的MC矩阵（目标1）、MC矩阵场生成的自动化（目标2）以及在许多MRI、MRS和MRSI应用中证明改善磁场均匀性（目标3）。

DESCRIPTION (provided by applicant): Many magnetic resonance (MR) modalities, like functional MR imaging (MRI), diffusion MRI and MR spectroscopy (MRS) have great potential for the study and diagnosis of brain disease and injury, and guiding surgical therapy. All of these methods benefit greatly from the increased sensitivity, resolution and contrast from high field strength magnets (3T and above). However, the advantages of higher magnetic fields have not been fully realized due to the increasingly confounding effects of magnetic field inhomogeneity caused by magnetic susceptibility differences between air and tissue. Magnetic field inhomogeneity leads to signal loss and spatial distortion in MRI and loss in spectral resolution and sensitivity in MRS. The loss of reliability due to these artifacts is a major reason why these techniques have not seen widespread use in high-field clinical applications. Current methods of magnetic field homogenization based on spherical harmonic shim coils perform well on small volumes but are inadequate to compensate the complex magnetic field distribution across the entire human brain. Here a novel technique based on matrices of DC coils is presented that can achieve superior shimming performance in the human brain in vivo. Preliminary results demonstrate the feasibility of multi-coil (MC) matrix shimming on human brain at 7.0 T. Characterization of the static and temporal characteristics of MC matrices will be established, as well as the integration with RF coils. This application proposes to develop MC matrix shimming to the point where excellent magnetic field homogeneity across the entire human brain at 7 T can be obtained in a robust and automated fashion for use with any existing clinical MR protocol. Specifically, the application is composed of three aims that are focused on optimization of the MC matrix for human brain applications at 7 T (Aim 1), the automation of MC matrix field generation (Aim 2) and demonstration of improved magnetic field homogeneity in a number of MRI, MRS and MRSI applications (Aim 3).