A Superconducting Magnet System for Whole-Body Metabolism Imaging

Abstract

Abstract-A 9.4 Tesla superconducting magnet is designed and fabricated with a warm bore of 800 mm for neuroscience research. The superconducting magnet will be made of a NbTi Wire-in-Channel (WIC) conductor with a higher ratio of copper to non-copper, which thus sustains the high stresses. It is cooled to operate temperature at 4.2 K liquid helium. The cryostat system is cooled through GM cryocoolers, some used to cool the radiation shield, and the others realize the re-condensed liquid helium. The MRI magnet system has a high level of stored energy, about 134 MJ, and a relatively-lower nominal current, about 212.5 A. The magnet will be operated in a persistent current mode with a superconducting switch. The WIC wires are employed to meet the cryostability criteria to avoid any risks from quench. The protection circuit with the subdivision of the coil reduces the terminate voltage and hot-spot temperature. In the paper, the specifications of magnet system will be presented.Index Terms-Metabolism imaging, MRI superconducting magnet, passive shield, sub-division quench protection.

High Field Superconducting Magnet Technologies for Magnetic Resonance Imaging

“…The electromagnetic design includes the homogeneity in the over diameter spherical volume(DSV), the scope of fringe field, the safety of the superconducting magnet and the construction costs. The goal of design is to meet the requirement of homogeneity over the DSV region by arranging a plurality of superconducting solenoids within a predetermined coil region with rectangular cross-section, and 5 G fringe field should be constrained within a reasonable range for an active shielding MRI system [11][12][13][14][15][16][17][18][19][20][21]. A hybrid optimal model with a discrete current-carrying region to solve the electromagnetic inverse problems was proposed.…”

“…In 1996, subsequently, in order to effectively reduce the effects of vibration coming from MRI system to image quality, pulse tube refrigerator successfully replaced GM refrigerator and is commonly used in magnetic resonance imaging systems. The IEE, CAS has been studying on all kinds of magnet and developed electromagnetic optimal design methods and software for MRI superconducting magnets [11][12][13][14][15][16][17][18][19][20][21]. The optimal objective function is the amount of superconducting wire which determines the cost of superconducting magnets.…”

“…By optimal strategy of mixing linear and nonlinear programming, the compact superconducting magnet system can be designed. By this optimal design method, several sets of MRI magnets have been designed and fabricated, including high-field whole body imaging [12,13] and animal imaging system with horizontal warm bore [13], 0.7 T openness MRI whole-body imaging systems [14,15], 3.0 T asymmetric head imaging system [16] and 1.0 T asymmetric horizontal warm bore system. Fig.…”

“…14. The magnet has horizontal length of 3.5 m and large warm bore with diameter of 0.8 m [13]. The magnet system is designed with the minimum cost of wire consumption.…”

Superconducting Magnet Technology and Applications

“…An 11.75 T/900 mm superconducting magnet system is in the process of being fabricated in France; it will be used in neuroscience research in the Commissariat à l'Ènergie Atomique (CEA) in France. Since 2011, a 9.4 T superconducting magnet for metabolic imaging has been undergoing development in the Institute of Electrical Engineering, Chinese Academy of Sciences (IEECAS) (Qiuliang Wang et al 2012). The magnet has a warm bore that is 800 mm in diameter and cryogenics with zero boil-off of liquid helium will be used for cooling the superconductors.…”