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

Brideson, M. A., Forbes, L. K. and Crozier, S. (2003) Winding patterns for actively shielded shim coils with asymmetric target-fields. Measurement Science & Technology, 14 4: 484-493. doi:10.1088/0957-0233/14/4/312

Author Brideson, M. A.
Forbes, L. K.
Crozier, S.
Title Winding patterns for actively shielded shim coils with asymmetric target-fields
Journal name Measurement Science & Technology   Check publisher's open access policy
ISSN 0957-0233
Publication date 2003-01-01
Year available 2003
Sub-type Article (original research)
DOI 10.1088/0957-0233/14/4/312
Open Access Status Not yet assessed
Volume 14
Issue 4
Start page 484
End page 493
Total pages 10
Editor P. Hauptmann
Place of publication Bristol
Publisher IOP Publishing
Language eng
Subject C1
291500 Biomedical Engineering
671402 Medical instrumentation
Abstract 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.
Keyword Engineering, Multidisciplinary
Instruments & Instrumentation
Magnetic Resonance Imaging
Shim Coil
Asymmetric Systems
Fourier Series
Stream Function
Q-Index Code C1
Institutional Status UQ

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Created: Wed, 15 Aug 2007, 11:32:15 EST