Superconducting magnets are effective for obtaining a highly stable, strong magnetic field for magnetic resonance imaging (MRI). Current MRI superconducting magnets require cooling in liquid helium at 4.2 K in order to use NbTi superconducting wire. The development of a high-temperature superconducting (HTS) coil that can be used without liquid helium cooling is greatly desired. In order to develop liquid helium-free MRI magnets using a high-temperature superconductor, the author has prototyped a model magnet that is able to generate extremely uniform, highly stable magnetic fields. This particular development includes such subjects as developing a coil structure where the superconducting characteristics do not deteriorate, working on a method of producing precision coils, designing coils that generate extremely uniform magnetic fields, and having high-temperature superconducting coils generate highly stable magnetic fields. MR imaging was carried out to verify the uniformity and stability of the magnetic fields.
A project for developing of RE1Ba2Cu3O7-δ (REBCO) magnets to be utilized in ultrahigh-field magnetic resonance imaging (MRI) was started in 2013. Our final targets are 9.4 T MRI systems for whole-body and brain imaging. In this project, two different development approaches towards the final target were planned. One is a small REBCO coil that can generate 10 Tclass magnetic fields, which is the same level as the target magnetic field. The other is a conduction-cooled 1.5 T REBCO MRI magnet that has a room-temperature bore of 396 mm, which is as large as those of mid-sized model magnets. These results were reflected in the design of a conduction-cooled 9.4 T REBCO magnet for whole-body MRI systems.
A research and development project to reduce the weight of a rotating gantry for carbon ions using high-temperature superconducting (HTS) magnets started in 2013, supported by the Japanese Ministry of Economy, Trade and Industry (METI) and the Japan Agency for Medical Research and Development (AMED). In this project, we aim to develop fundamental technologies for designing and fabricating a HTS gantry, and fabricate a small model of a HTS dipole magnet and evaluate its performance. The results of the project are described in this paper.