Optimization of Human Head MRI and MRS Using High Order Shim Insert

描述（由申请人提供）：MR的多项研究提供了无可辩驳的证据，证明使用高阶垫片来控制磁场不均匀性可以显著改善图像质量，特别是在高场和具有挑战性的垫片区域，例如人类头部的额叶和颞叶。然而，MRI制造商一直非常抵制提高高场扫描仪中垫片性能的想法，尽管已经证明，所有3T和7T系统中可用的传统二阶垫片的性能都不令人满意。升级到更高阶垫片能力的成本和复杂性，对垫片软件和应用程序开发的必要改进，为纠正这种情况和实现改进造成了严重的障碍。唯一的商用7T扫描仪与三阶垫片是由飞利浦制造的，但在许多应用中，它缺乏一些软件功能，使垫片有用。本提案的目标是开发用于头部MR的高阶（第3,4和第5）垫片插入，克服将这些垫片集成到磁体孔中的成本和复杂性，并为人类头部的有效垫片提供高度实用的安排。使用三阶垫片的性能显著改善的明确演示已在导致本提案的初步结果中记录。我们现在正在领导开发实际实施的四阶垫片。我们开发的新颖方面将是构建高阶阻性垫片线圈组，其强度和性能足以消除大脑挑战性区域中存在的四阶球面谐波分量，并且也可以在现有的梯度线圈中进行改造。特别是，神经学应用需要更长的游动性能。为此，通过使用高度优化的头部射频线圈，可以在全身扫描仪中节省足够的空间来安装能够以高强度提供三阶和四阶垫片的插入件，同时不影响其他应用的可访问性。演示拟议的内孔垫片线圈组的安全性和有效性，将使该技术以升级的形式进行商业应用成为可能，该技术可应用于目前缺乏此功能的大量商用扫描仪。公共卫生相关性：磁共振成像（MRI）和光谱学（MRS）是获得高质量图像和完整健康和患病人体组织代谢谱的领先技术。不幸的是，组织易感性引起的磁场空间变化会严重降低MRI和MRS数据的质量，以至于可能无法区分正常和病变区域。目前的项目侧重于开发和实施可用于新扫描仪或改造现有扫描仪的新技术，从而大大提高核磁共振数据的质量，从而有利于公共卫生。

DESCRIPTION (provided by applicant): Multiple studies in MR provide irrefutable evidence that the use of high order shims for controlling magnetic field inhomogeneity brings significant improvement to image quality, particularly at high fields and in challenging shimming regions, such as in the inferior frontal and temporal lobes of the human head. MRI manufacturers however, have been very resistant to the idea of improving the performance of shims in high field scanners even though it has been demonstrated that the performance of the conventional 2nd order shims available in all 3T and 7T systems is unsatisfactory. The cost and complexity of the upgrade to higher order shim capability, the necessary improvement in shimming software and the applications development create serious barriers for rectifying this situation and in bringing about an improvement. The only commercial 7T scanner with 3rd order shims is manufactured by Philips but in many applications it lacks some software capabilities for rendering the shims useful. The goal of this proposal is to develop a high order (3rd, 4th and 5th) shim insert for head MR that overcomes the cost and complexity of integrating those shims into the magnet bore, and renders a highly practical arrangement for efficient shimming of the human head. An unequivocal demonstration of significant improvements in performance using 3rd order shims has been documented in the preliminary results leading to this proposal. We are now leading the development of the practical implementation of the 4th order shims. The novel aspect of our development will be the construction of a high order resistive shim coil set which has strength and performance sufficient to null the 4th order spherical harmonic field components present in challenging regions of the brain and which can also be retrofitted inside an existing gradient coil. In particular, neurological applications require extended shimming performance. For such a purpose, by using a highly optimized head RF coil, enough space can be saved in a whole body scanner to mount an insert capable of delivering the 3rd and 4th order shims at high strength, while not compromising the accessibility for other applications. Demonstrating the safety and efficacy of the proposed in-bore shim coil set will make possible the commercial use of this technology in the form of an upgrade that can be applied to a large number of commercial scanners that presently lack this capability. PUBLIC HEALTH RELEVANCE: Magnetic resonance imaging (MRI) and spectroscopy (MRS) are the leading techniques for obtaining high-quality images and metabolic profiles of intact healthy and diseased human tissues. Unfortunately, tissue susceptibility induced spatial variations of magnetic field can severely degrade the quality of MRI and MRS data, to the extent that distinction between normal and diseased areas may be compromised. The current project focuses on developing and implementing novel technology that can be used in new scanners or retrofitted to existing scanners thereby leading to greatly increased quality of MR data with consequent benefit to public health.