A FIELD-GRADIENT COIL USING CONCENTRIC RETURN PATHS

An approach to transverse field-gradient coil design is presented whic h locates all current elements in planes perpendicular to the main mag netic field. The linear volume of the resulting coil structure can be made to extend nearly to both ends of the coil. This design is based o n forming a concentric return path in the same plane as the field-prod ucing arcs. The coil structure consists of stacked planar units which give a desired field-gradient configuration. The size of the linear-fi eld region is optimized by varying the current in each plane, by varyi ng the location of a plane relative to the others in the stack, or by varying both current and location. Coils with linear regions having a wide range of length-to-diameter ratios can be designed, as illustrate d by two examples. The construction of a prototype coil is presented a nd its performance in imaging confirms the analysis. This type of desi gn is suited to magnetic resonance of the human head without obstructi on from the shoulders. (C) 1996 Academic Press, Inc.