Overcoming phase effects of voxel-sized coils in planar and cylindrical arrays

Parallel imaging in MRI (using multiple coils to partially encode k-space) is currently the primary route to decreasing scan time. Single echo acquisition (SEA) imaging is a completely parallel imaging method recently developed by our group that collects a full image in a single echo. Phase encoding is eliminated and replaced by the spatial localization of long and very narrow coils. The fact that the coils are on the order of the voxel size for the first time in an MR application has led to an examination of the effect of the phase of the coil on the signal received from the voxel and how to most effectively manipulate it. Obtaining full signal from a voxel in planar arrays can be accomplished with a single gradient compensation pulse, but the phase effects in cylindrical arrays are more complex due to the changing coil angle with regard to the Cartesian axes of the gradients. This paper discusses the signal-phase interactions of planar and cylindrical arrays of voxel-sized coils and suggests methods for phase manipulation for optimization.