Lin Zijie, Zhang Zhan, Li Jiaxin, Gao Zhaoyao, Chu Zhenyu, Liu Yongsuo, Zhang Panfeng, Wu Leping, Zhou Chao
Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.
Science Island Branch, Graduate School of USTC, University of Science and Technology of China, Hefei, China.
Med Phys. 2025 May;52(5):3270-3279. doi: 10.1002/mp.17641. Epub 2025 Jan 28.
High-resolution brain imaging is crucial in clinical diagnosis and neuroscience, with ultra-high field strength MRI systems ( ) offering significant advantages for imaging neuronal microstructures. However, achieving magnetic field homogeneity is challenging due to engineering faults during the installation of superconducting strip windings and the primary magnet.
This study aims to design and optimize active superconducting shim coils for a 7 T animal MRI system, focusing on the impact of safety margin, size, and adjustability of the second-order shim coils on the MRI system's optimization.
The study employs a nonlinear optimization method to determine the parameters of the shim coils, considering the size of the coil, the level of undesired harmonics, and the whole number approximation of the turns in each coil. The study also conducts a thorough robustness analysis, examining the effects of coil winding accuracy, former processing accuracy, and assembly angle accuracy on the harmonic intensity of each coil.
The optimization design results for the 7 T MRI system's shim coils show that the magnetic field changes are less than 0.5 %. After second-order shimming and the harmonic coupling an, the low-order harmonics are minimized, resulting in an improved magnetic field peak-to-peak uniformity from 254.47 to 8.970 ppm.
The study successfully demonstrates the creation of a set of second-order shim coils for a 7 T animal MRI system through numerical optimization. The design outputs provide essential technological support for the development of a human whole-body 7 T MRI system, ensuring high-quality imaging at the neuronal level. The project also highlights the importance of considering manufacturing and assembly flaws in the shim coil design process to achieve effective shimming in practical engineering scenarios.
高分辨率脑成像在临床诊断和神经科学中至关重要，超高场强MRI系统在成像神经元微观结构方面具有显著优势。然而，由于超导带绕组和主磁体安装过程中的工程故障，实现磁场均匀性具有挑战性。
本研究旨在设计和优化用于7T动物MRI系统的有源超导匀场线圈，重点关注二阶匀场线圈的安全裕度、尺寸和可调性对MRI系统优化的影响。
该研究采用非线性优化方法来确定匀场线圈的参数，考虑线圈尺寸、不期望谐波的水平以及每个线圈匝数的整数近似。该研究还进行了全面的稳健性分析，检查线圈绕组精度、线圈架加工精度和装配角度精度对每个线圈谐波强度的影响。
7T MRI系统匀场线圈的优化设计结果表明，磁场变化小于0.5%。经过二阶匀场和谐波耦合an后，低阶谐波最小化，磁场峰峰值均匀性从254.47 ppm提高到8.970 ppm。
该研究通过数值优化成功展示了为7T动物MRI系统创建一组二阶匀场线圈。设计输出为人类全身7T MRI系统的开发提供了重要的技术支持，确保在神经元水平上实现高质量成像。该项目还强调了在匀场线圈设计过程中考虑制造和装配缺陷对于在实际工程场景中实现有效匀场的重要性。
