Noncircular Birdcage Coils Optimization and Implementation

One of the favorite methods to produce a homogeneous radiofrequency (RF) magnetic field, B1, in MRI is with a cylindrical birdcage coil. While this coil produces a very homogeneous field in a cylidrical volume, a coil that is shaped more like the human body would be more sensitive to the signal received from the nuclei in the body. We have developed a method for optimization and implementation of birdcage coils with elliptical cross-sections and linearly polarized B1 fields (ref). Notable gains in signal-to-noise ratio over those of cylindrical birdcage coils are achieved. More recently, we have developed a method for numerically optimizing non-circular coils with circularly-polarized B1 fields within cylindrical RF shields and implementing them.