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Winding patterns for actively shielded shim coils with asymmetric target-fields


Brideson, MA and Forbes, LK and Crozier, S, Winding patterns for actively shielded shim coils with asymmetric target-fields, Measurement Science and Technology, 14, (4) pp. 484-493. ISSN 0957-0233 (2003) [Refereed Article]

DOI: doi:10.1088/0957-0233/14/4/312


A method is presented for calculating the currents and winding patterns required to design independent zonal and tesseral shim coils for magnetic resonance imaging. Both actively shielded and unshielded configurations are considered, and the region of interest can be located asymmetrically with respect to the coil's length. Streamline, target-field and Fourier-series methods are utilized. The desired target-field is specified at two cylindrical radii, on and inside a circular conducting cylinder of length 2L and radius a. The specification is over some asymmetric portion pL < z < qL of the coil's length (-1 < p < q < 1). Arbitrary functions are used in the outer sections, -L < z < pL and qL < z < L, to ensure continuity of the magnetic field across the entire length of the coil. The entire field is then periodically extended as a half-range cosine Fourier series about either end of the coil. The resultant Fourier coefficients are then substituted into the Fourier-series expressions for the internal and external magnetic fields, and current densities and stream functions on both the primary coil and shield. A contour plot of the stream function directly gives the required coil winding patterns. Spherical harmonic analysis and shielding analysis on field calculations from a ZX shim coil indicate that example designs and theory are well matched.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Condensed matter physics
Research Field:Electronic and magnetic properties of condensed matter; superconductivity
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the mathematical sciences
UTAS Author:Brideson, MA (Dr Michael Brideson)
UTAS Author:Forbes, LK (Professor Larry Forbes)
ID Code:27031
Year Published:2003
Web of Science® Times Cited:9
Deposited By:Mathematics
Deposited On:2003-08-01
Last Modified:2004-06-21

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