Multi-coil Shimming of the Human Brain at 7 Tesla

描述(申请人提供)：许多磁共振(MR)方式，如功能磁共振成像(MRI)、弥散磁共振成像(MRI)和磁共振波谱(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的潜力。所有这些都是 方法得益于高场强磁铁(3T及以上)的灵敏度、分辨率和对比度的提高。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，强磁场的优势还没有完全实现。磁场的不均匀会导致MRI的信号丢失和空间失真，以及MRS的光谱分辨率和灵敏度的损失。这些伪影造成的可靠性损失是这些技术在高场临床应用中未得到广泛应用的主要原因。目前基于球谐填隙线圈的磁场均匀方法在小体积上表现良好，但不足以补偿整个人脑中复杂的磁场分布。在这里，提出了一种基于直流线圈矩阵的新技术，可以在活体人类大脑中实现优越的垫片性能。初步结果表明，多线圈(MC)矩阵在7.0T下对人脑进行匀场是可行的，将建立MC矩阵的静态和时间特性的特征，以及与RF线圈的集成。此应用程序建议开发MC矩阵垫片，以便在7T时以稳健和自动的方式获得整个人脑的出色磁场均匀度，以便与任何现有的临床MR协议一起使用。具体地说，该应用程序由三个目标组成，这三个目标侧重于在7T处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应用中展示改进的磁场均匀度(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).