Toward designing asymmetric head gradient coils for high‐resolution imaging

Abstract

ABSTRACT:The aim of the research described here is to design head gradient coils using approaches previously developed by the authors. The wave equation method for designing gradient coils is used to design a transverse gradient coil winding on a cylindrical/spherical former. The results are compared with asymmetric cylindrical designs and other well-known head gradient coil designs to establish the quality of the gradient coil winding. Comparisons of field, inductance, torque, and other quality factors are made before conclusions are drawn about the adequacy of such a winding pattern to perform high-resolution imaging of the head. We show that it is possible to generate a robust winding pattern that has good efficiency and produces a sufficiently large imaging volume.

A wrapped edge transverse gradient coil design for increased gradient homogeneity

“…The quality factor h was calculated according to (40), where the diameter d of the FoV to the 5% contour line is used to reflect a measure of delivered energy. The quality factor as a measure of FoV volume is greatly increased for the wrapped edge design, indicating that significantly more usable imaging volume is obtained in the wrapped edge design.…”

“…Self-Adaptive Differential Evolution (SaDE) (39) was then used to find the best contour level spacing through iterated evaluations of the error function, which is computed as the sum of squares of the deviations of the computed gradient magnetic field from the expected gradient magnetic field. Details of the error function and the treatment of inductance and resistance are provided in (40,41). …”

3D Gradient coil design – Toroidal surfaces

“…In an attempt to address specific gradient problems further and improve coil performance, more recent gradient designs have tended to deviate away from the established primary plus shield coil, cylindrical or biplanar gradient system and a variety of geometries have been considered (see for example [25][26][27][28][29][30][31][32][33]). However, despite these methods being applicable and adaptable to arbitrary geometry, this geometry must still be chosen prior to the method being implemented.…”

Design of transverse head gradient coils using a layer-sharing scheme

“…This advantage can be used to improve other coil properties, such as reducing inductance, resistance, and so on. Numerical simulations on asymmetric head coil designs using this method [10][11][12] were carried out and the coil performances were compared with the corresponding conventional coils.…”