Biplanar Radiofrequency Coil Design

Abstract

A novel geometry for radiofrequency coil design is described. In this geometry, longitudinal wires of the coil lie on two parallel planes. The currents in the wires of one plane run in the direction opposite to those of the other plane. An analytic solution is provided for the field produced by infinite surface currents running in the biplanar geometry. For the case of discrete wires, computer-generated field maps imply that the homogeneity and sensitivity of the biplanar design are superior to those of a saddle coil, but worse than those obtained in an equivalent discrete cosine or birdcage coil design. Optimization of this coil design was performed using computer simulations. The measured B1 map of an optimized, single-tuned biplanar coil compares favorably to that of an equivalent discrete cosine coil, demonstrating excellent homogeneity in the central region of the coil. A 30 × 24 × 40 cm biplanar coil has been coupled to a 1.5 T imaging system. Images of the human abdomen generated with this coil demonstrate a high degree of homogeneity across nearly all of the sensitive region of the coil.