Near field pattern uniformity for high resolution magnetic resonance imaging systems based on metaheuristic optimization

This document studies the problem of near‐field pattern uniformity in high resolution magnetic resonance imaging (MRI) systems. The existence of such inhomogeneity is related to the composition of the global near field radiation pattern of the receiving antennas in the MRI system. For the MRI image uniformity enhancement, two approaches are proposed in order to obtain the optimal image in terms of the acquisition process and subsequent post‐processing. The first one is based on a progressive variation of the antenna phase feeding in the array distribution, either at each arraying or between rings, which lets reduce the radial inhomogeneity between the central value (maximum) and the rest of the surrounding values. The second one is based on a progressive variation (rotation) of the antenna location in the array distribution, which lets reduce the pattern ripples at the outer cylindrical rings of the volume under test. In this work, a metaheuristic optimization strategy has been selected to obtain the optimal configuration. This optimal configuration implies angular rotation and the addition of feeding phase values to strain ripple reduction and pattern uniformity, depending on the particular size of the cylinder volume that conforms the volume under exploration for image acquisition.