Shimmer：用于低场MRI磁体的端到端开源无源B0匀场方法
Shimmer: End-to-End Open-Source Passive B0 Shimming Methodology for Low-Field MRI Magnets
AI总结：
Shimmer是一种端到端开源无源B0匀场方法，结合磁场测绘、模拟与优化等技术，可降低低场MRI磁体的场不均匀度，实现体模无畸变成像，为低场MRI性能改进提供可复现方案。
AI中文摘要：
基于永磁体阵列的低场MRI扫描仪需要精确的B0匀场，以获得足够的场均匀性来实现成像。本文提出了Shimmer，一种使用放置在主磁体阵列外部的额外钕铁硼（NdFeB）磁体对低场MRI磁体进行无源匀场的开源方法。该端到端方法结合了磁场测绘、磁场模拟、匀场磁体位置与朝向的数值优化，以及3D打印匀场支架的自动化生成。研究考虑并评估了连续磁体旋转及多种优化策略。该方法在三个不同的直径200mm、磁场强度约50mT的永磁体阵列上进行了验证与应用，将初始场不均匀度9361ppm、31721ppm和34143ppm分别降至888ppm、1812ppm和1602ppm。提升后的均匀性实现了体模的无畸变MR成像，Shimmer为改进低场MRI磁体的性能提供了可复现且可适配的方法。
英文摘要：
Low-field MRI scanners based on permanent magnet arrays require accurate B0 shimming to achieve sufficient field homogeneity for imaging. Here, we present Shimmer, an open-source methodology for passive shimming of low-field MRI magnets using additional NdFeB magnets placed outside the main magnet array. The end-to-end methodology combines magnetic field mapping, magnetic field simulations, numerical optimization of shim magnet positions and orientations, and automated generation of 3D-printable shim holders. Continuous magnet rotations and several optimization strategies are considered and evaluated. The method was validated and applied to three different permanent magnet arrays ~50 mT in 200 mm diameter spherical volumes, reducing initial field inhomogeneities of 9361ppm, 31721 ppm and 34143 ppm to 888 ppm, 1812 ppm and 1602 ppm respectively. The improved homogeneity enabled undistorted MR imaging of a phantom. Shimmer provides a reproducible and adaptable approach for improving the performance of low-field MRI magnets.
