Integrated RF/shim body coil array for MRI with localized shimming

项目总结/摘要 空气/组织界面处的磁化率差异诱导强局部静磁场（B 0） 不均匀性，无法用整体球谐（SH）匀场器有效匀场 临床MRI扫描仪上的线圈，导致图像伪影，如失真、模糊、信号丢失， 不完全脂肪抑制。这些伪影在临床应用中引入了诊断不准确性， 在身体成像中尤其严重，其遭受比大脑更广泛的B 0不均匀性 成像，以及用于基于快速成像序列的技术，例如回波平面成像，其被使用 在许多临床应用中，例如弥散加权成像（DWI）。因此，身体DWI是最 具有挑战性的应用，以及开发可实现高B 0均匀性的新技术 为了提高其空间保真度和准确性并增加其临床实用性， 最近提出了一种新的概念，称为集成并行接收，激励和匀场（iPRES） 所提出的，其允许射频（RF）电流和直流（DC）电流在同一线圈中流动， 从而能够利用单个集成RF/匀场线圈阵列实现RF接收和局部B 0匀场。这 因此，新技术可以有效地填补局部B 0不均匀性，而不会降低信噪比 这可能会导致信噪比（SNR）降低或需要磁体孔中的额外空间，这在人脑中得到了证明 32通道iPRES头部线圈阵列然而，它在身体成像方面的应用更具挑战性， 这是因为体线圈阵列中的线圈元件更大以及B 0不均匀性更广泛。 该提案的目标是开发下一代iPRES线圈设计，称为自适应iPRES（N）， 以在体内实现高B 0均匀性。具体地，32通道体线圈的每个RF线圈元件 阵列将被划分为N个较小的独立DC环路，并且将添加开关来分配DC 根据需要将电流输入适当的直流回路，从而实现更高的灵活性和空间分辨率 用于局部B 0匀场，而不需要额外的电源。首先进行模拟， 优化线圈设计（目标1）。线圈阵列然后将通过使用新颖的开关技术来实现 并将集成到3 T MRI扫描仪中（Aim 2）。最后，将通过进行台架测试对其进行验证， 体模实验和人体实验，包括高分辨率腹部DWI（Aim 3）。 这项新技术将在体内提供前所未有的B 0均匀性，而不会带来SNR损失， 将大大提高空间保真度、图像质量、诊断准确性、扫描效率和患者 舒适性，适用于广泛的临床应用，包括身体DWI。它还可以在宽范围内进行填隙- 孔和PET/MR扫描仪，没有SH匀场线圈，并将消除对这种线圈的需要， 未来的扫描仪，导致更低的制造成本和更宽的磁铁孔，以适应更大的病人。

Project Summary / Abstract Magnetic susceptibility differences at air/tissue interfaces induce strong localized static magnetic field (B0) inhomogeneities, which cannot be effectively shimmed with the whole-body spherical harmonic (SH) shim coils onboard clinical MRI scanners, resulting in image artifacts such as distortions, blurring, signal loss, and incomplete fat suppression. These artifacts introduce diagnostic inaccuracies in clinical applications and are particularly severe in body imaging, which suffers from more extensive B0 inhomogeneities than brain imaging, and for techniques based on fast imaging sequences such as echo-planar imaging, which is used in many clinical applications such as diffusion-weighted imaging (DWI). Thus, body DWI is one of the most challenging applications and the development of a new technology that can achieve a high B0 homogeneity in the body is critically needed to improve its spatial fidelity and accuracy and to increase its clinical utility. A novel concept, termed integrated parallel reception, excitation, and shimming (iPRES), was recently proposed, which allows a radiofrequency (RF) current and a direct current (DC) to flow in the same coil, thereby enabling RF reception and localized B0 shimming with a single integrated RF/shim coil array. This new technology can thus effectively shim localized B0 inhomogeneities without reducing the signal-to-noise ratio (SNR) or requiring additional space in the magnet bore, which was demonstrated in the human brain with a 32-channel iPRES head coil array. However, its application to body imaging is more challenging, because of the larger coil elements in body coil arrays and the more extensive B0 inhomogeneities. The goal of this proposal is to develop the next generation of iPRES coil design, termed adaptive iPRES(N), to achieve a high B0 homogeneity in the body. Specifically, each RF coil element of a 32-channel body coil array will be divided into N smaller independent DC loops and switches will be added to distribute the DC currents into the appropriate DC loops as needed, resulting in a much higher flexibility and spatial resolution for localized B0 shimming, without requiring additional power supplies. Simulations will first be performed to optimize the coil design (Aim 1). The coil array will then be implemented by using a novel switch technology and will be integrated into a 3T MRI scanner (Aim 2). Finally, it will be validated by performing bench tests, phantom experiments, and human experiments, including high-resolution abdominal DWI (Aim 3). This new technology will provide an unprecedented B0 homogeneity in the body with no SNR penalty, which will substantially improve the spatial fidelity, image quality, diagnostic accuracy, scan efficiency, and patient comfort for a wide range of clinical applications, including body DWI. It will also enable shimming on wide- bore and PET/MR scanners, which do not have SH shim coils, and will eliminate the need for such coils in future scanners, resulting in lower manufacturing costs and a wider magnet bore to fit larger patients.