Design of a conduction-cooled 9.4T REBCO magnet for whole-body MRI systems
Design of a conduction-cooled 9.4T REBCO magnet for whole-body MRI systems
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DOI：
10.1088/0953-2048/29/10/104001
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发表时间：
2016-10-01
影响因子：
3.6
通讯作者：
Fukuyama, Hidenao
中科院分区：
文献类型：
--
作者：
Miyazaki, Hiroshi;Iwai, Sadanori;Fukuyama, Hidenao
2013年启动了一个开发用于超高场磁共振成像（MRI）的REBa 2Cu 3 O 7-delta（REBCO）磁体的项目。由于REBCO涂层导体在拉伸应力下具有高机械强度和高临界电流密度，因此使用REBCO线圈将允许超导磁体比常规磁体更小和更轻。此外，传导冷却的超导磁体比由液氦浴冷却的超导磁体使用起来更简单，因为低温系统的操作和维护变得更简单，而不需要处理低温流体。用于MRI的超导磁体需要均匀、稳定的磁场。磁场的均匀性高度依赖于线圈的形状和位置。此外，在REBCO磁体中，屏蔽电流感应磁场改变磁体的磁场分布，是关键问题之一。为了评估磁场均匀性和屏蔽电流感应磁场，制作了1 T模型磁体和一些测试线圈。从1 T模型磁体的评估发现，磁场不均匀性的主要原因是线圈的z轴位置的公差，因此，重要的是控制单个薄煎饼之间的差距。此外，我们已经证明了一个8.27 T的中心磁场在10 K与一个小的测试线圈的产生。屏蔽电流感应磁场为0.43 T，可通过使用电磁场模拟程序进行预测。这些结果反映在用于全身MRI系统的传导冷却9.4 T REBCO磁体的设计中。磁体由六个主线圈和两个有源屏蔽线圈组成。总导体长度为581 km，储存能量为293 kJ。对于500 mm直径的球形体积（DSV），场不均匀性为24 ppm峰-峰和3 ppm体积根均方（VRMS）。轴向和径向5高斯线位置分别小于5 m和4.2 m。
A project on the development of REBa2Cu3O7-delta (REBCO) magnets for ultra-high-field magnetic resonance imaging (MRI) was started in 2013. Since REBCO-coated conductors feature high mechanical strength under tensile stress and high critical current density, use of REBCO coils would allow superconducting magnets to be made smaller and lighter than conventional ones. In addition, a conduction-cooled superconducting magnet is simpler to use than one cooled by a liquid helium bath because the operation and maintenance of the cryogenic system become simpler, without the need to handle cryogenic fluid. Superconducting magnets for MRI require homogeneous, stable magnetic fields. The homogeneity of the magnetic field is highly dependent on the coil shape and position. Moreover, in REBCO magnets, the screening-current- induced magnetic field, which changes the magnetic field distribution of the magnet, is one of the critical issues. In order to evaluate the magnetic field homogeneity and the screening-current- induced magnetic field, a 1 T model magnet and some test coils were fabricated. From an evaluation of the 1 T model magnet, it was found that the main reason for magnetic field inhomogeneity was the tolerances in the z-axis positions of the coils, and therefore, it is important to control the gap between the single pancakes. In addition, we have already demonstrated the generation of an 8.27 T central magnetic field at 10 K with a small test coil. The screening-current-induced magnetic field was 0.43 T and was predictable by using an electromagnetic field simulation program. These results were reflected in the design of a conduction-cooled 9.4 T REBCO magnet for whole-body MRI systems. The magnet was composed of six main coils and two active shield coils. The total conductor length was 581 km, and the stored energy was 293 kJ. The field inhomogeneity was 24 ppm peak to peak and 3 ppm volume-root-mean-square (VRMS) for a 500 mm diameter spherical volume (DSV). The axial and radial 5 gauss line locations were less than 5 m and 4.2 m respectively.