An approach to transverse field-gradient coil design is presented quired to cover the subject of interest and will use the smallwhich locates all current elements in planes perpendicular to the est possible coil-winding volume. In addition, smaller coil main magnetic field. The linear volume of the resulting coil strucdesigns have reduced interaction with the cryostat and other ture can be made to extend nearly to both ends of the coil. This metal structures in the magnet which produce eddy currents, design is based on forming a concentric return path in the same so the need for shielding is reduced.
plane as the field-producing arcs. The coil structure consists of
We have taken a design approach (8, 9) that results in a stacked planar units which give a desired field-gradient configuratransverse gradient coil which is torque free and has a linear tion. The size of the linear-field region is optimized by varying the region that extends quite close to both ends of the coil. It is current in each plane, by varying the location of a plane relative possible to construct a coil which fits over the human head to the others in the stack, or by varying both current and location.
while avoiding the shoulders, thus improving the efficiency.
Coils with linear regions having a wide range of length-to-diameter ratios can be designed, as illustrated by two examples. The con-The gradient coil is composed of a number of planar units, struction of a prototype coil is presented and its performance in as shown in Fig. 1a, having current return paths located on imaging confirms the analysis. This type of design is suited to a larger concentric cylinder. This coil design is referred to magnetic resonance of the human head without obstruction from as a concentric return path (CRP) coil because the currentthe shoulders.