Fast methods for full-wave electromagnetic solvers in MRI

Abstract

High static field ( 3T) MR scanners can produce human tissue images of astounding clarity, but rely on high frequency ( 123MHz) electromagnetic radiation that generates complex in-tissue field patterns that are patient-specific and potentially harmful. Many such scanners use multiple transmitters to better control field patterns, but then adjust the transmitters based on general guidelines rather than optimizing for the specific patient, mostly because computing patient-specific fields was presumed far too slow. It was recently demonstrated that the combination of fast low-resolution tissue mapping and fast voxel-based field simulation can be used to perform a rapid patient-specific MR safety check. However, the field simulation still required several minutes, making it too slow to perform the dozens of simulations that would be needed for patient-specific optimization. In this work, we develop a set of numerical acceleration techniques that facilitate fast field simulations that bridge the gap between the performance of current state-of-art full-wave electromagnetic packages and time requirements dictated by real-time patient-specific field optimization in a clinical setting. These techniques cater to a large range of body sizes and complex coil geometries.