Shielded biplanar gradient coil design

Abstract

An application of the target field method to the design of shielded biplanar gradient coils for magnetic resonance imaging electromagnets is presented. Some specific cases are studied, and optimized geometries are proposed for the axial and transverse gradient coils that eliminate the third‐ and minimize the fifth‐order terms in the magnetic field expansion. J. Magn. Reson. Imaging 1999;9:725–731. © 1999 Wiley‐Liss, Inc.

A uniplanar three-axis gradient set for in vivo magnetic resonance microscopy

“…Relatively few designs for planar gradients have been reported [17][18][19][20][21][22], with most designs representing biplanar gradient sets appropriate for open human MRI systems employing a pair of permanent magnet pole pieces with the main field oriented vertically [17,18,20]. Optimized biplanar coil windings for finite areas and minimum inductance have been reported using methods such as stream function representation of current density that are also applicable to uniplanar gradient geometries.…”

Optimization of biplanar gradient coils for magnetic resonance imaging

“…The method described below is proposed for the design of self-shielded gradient sets with biplanar geometry [1,2]. In these gradient system, currents flow in four parallel (x, y)-planes: The primary current density flows in the two inner planes, placed at z = ±a, and the shielding current density flows in the two outer planes, placed at z = ±b (a ≤ b).…”

“…To null the magnetic field produced by this biplanar configuration outside the coil, a current density given by [1] …”

“…[1]). Therefore, for a continuous symmetric current density j y (x ) in the primary planes, a shielding current density …”

“…Open magnetic resonance imaging (MRI) scanners are frequently based on electromagnets or permanent magnets and require planar gradient coils [1]. In these systems, the gap between pole tips is minimized in order to increase the magnetic field strength, B 0 , and the gradient coils need to fit restricted volumes and are located very close to metallic parts of the scanner.…”