A nesting approach for the numerical analysis of MRI birdcage antennas in the presence of the human head

Integral-equation approaches are among the solvers that can be used to analyse RF fields in MRI scanners, in particular when the human body is divided into a collection of homogeneous objects. This solver can be relatively intensive in terms of computation time and memory if the full solution is rerun everytime minor changes are considered in the MRI antennas. In this work, an efficient solving tool based on a nesting approach is proposed. The idea consists of avoiding recomputation of all the equivalent currents inside the body. A validation is provided for a simple structure with a commercial solver (CST); then by using a developed in-house code, the magnetic field inside the brain is shown when a birdcage antenna is used around the human head.