Coil Array Design for Parallel Imaging: Theory and Applications

Basic principles of radiofrequency coil array design for parallel imaging are described, and illustrated in practice. Because parallel magnetic resonance imaging (MRI) techniques rely upon the spatial distribution of coil sensitivity patterns to provide spatial information about the field of view to be imaged, a careful choice of array design is essential. Both qualitative perspectives and formal descriptions of spatial encoding in parallel imaging are outlined, along with basic principles of noise propagation and signal-to-noise behavior, both for particular coil arrays and at the theoretical limits of performance. Considerations essential to effective array design for parallel MR applications are then reviewed, and particular case studies involving high-performance head arrays are used to demonstrate the practical application of these principles. Potential complications encountered during the experimental evaluation of coil array performance are discussed, and the results of particular comparisons are presented. Finally, various classes of application-targeted array designs are identified, and selected tips regarding array troubleshooting are provided. This review is intended to assist coil designers in the effective design of coil arrays intended for parallel MR applications. It may also serve to provide insight into how arrays are currently used for parallel MRI and to place in context new innovations to come.