中国物理B ›› 2002, Vol. 11 ›› Issue (10): 1008-1012.doi: 10.1088/1009-1963/11/10/307

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A design of novel type superconducting magnet for super-high field functional magnetic resonance imaging by using the harmonic analysis method of magnetic vector potentials

俎栋林, 郭华, 宋枭禹, 包尚联   

  1. Beijing Key Laboratory of Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871, China
  • 收稿日期:2002-03-16 修回日期:2002-04-25 出版日期:2002-10-12 发布日期:2005-06-12
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No 19675005).

A design of novel type superconducting magnet for super-high field functional magnetic resonance imaging by using the harmonic analysis method of magnetic vector potentials

Zu Dong-Lin (俎栋林), Guo Hua (郭华), Song Xiao-Yu (宋枭禹), Bao Shang-Lian (包尚联)   

  1. Beijing Key Laboratory of Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871, China
  • Received:2002-03-16 Revised:2002-04-25 Online:2002-10-12 Published:2005-06-12
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No 19675005).

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摘要： The approach of expanding the magnetic scalar potential in a series of Legendre polynomials is suitable for designing a conventional superconducting magnetic resonance imaging magnet of distributed solenoidal configuration. Whereas the approach of expanding the magnetic vector potential in associated Legendre harmonics is suitable for designing a single-solenoid magnet that has multiple tiers, in which each tier may have multiple layers with different winding lengths. A set of three equations to suppress some of the lowest higher-order harmonics is found. As an example, a 4T single-solenoid magnetic resonance imaging magnet with 4×6 layers of superconducting wires is designed. The degree of homogeneity in the 0.5m diameter sphere volume is better than 5.8 ppm. The same degree of homogeneity is retained after optimal integralization of turns in each correction layer. The ratio Bm/B0 in the single-solenoid magnet is 30% lower than that in the conventional six-solenoid magnet. This tolerates higher rated superconducting current in the coil. The Lorentz force of the coil in the single-solenoid system is also much lower than in the six-solenoid system. This novel type of magnet possesses significant advantage over conventional magnets, especially when used as a super-high field functional magnetic resonance imaging magnet.

Abstract: The approach of expanding the magnetic scalar potential in a series of Legendre polynomials is suitable for designing a conventional superconducting magnetic resonance imaging magnet of distributed solenoidal configuration. Whereas the approach of expanding the magnetic vector potential in associated Legendre harmonics is suitable for designing a single-solenoid magnet that has multiple tiers, in which each tier may have multiple layers with different winding lengths. A set of three equations to suppress some of the lowest higher-order harmonics is found. As an example, a 4T single-solenoid magnetic resonance imaging magnet with 4×6 layers of superconducting wires is designed. The degree of homogeneity in the 0.5m diameter sphere volume is better than 5.8 ppm. The same degree of homogeneity is retained after optimal integralization of turns in each correction layer. The ratio Bm/B0 in the single-solenoid magnet is 30% lower than that in the conventional six-solenoid magnet. This tolerates higher rated superconducting current in the coil. The Lorentz force of the coil in the single-solenoid system is also much lower than in the six-solenoid system. This novel type of magnet possesses significant advantage over conventional magnets, especially when used as a super-high field functional magnetic resonance imaging magnet.

Key words: super-high field superconducting magnet for functional magnetic resonance imaging, high homogeneity functional magnetic resonance imaging magnet, single-solenoid type functional magnetic resonance imaging magnet, magnetic vector potential, harmonic analys

中图分类号:  (Superconducting magnets; magnetic levitation devices)

  • 84.71.Ba
02.10.De (Algebraic structures and number theory) 07.57.Pt (Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques) 02.30.Px (Abstract harmonic analysis) 84.71.Mn (Superconducting wires, fibers, and tapes)