An Investigation into the Role of Dielectric Resonance in Parallel Imaging

F. Wiesinger, P-F. Van de Moortele, G. Adriany, N. De Zanche, C. Snyder, T. Vaughan, K. Ugurbil, K. P. Pruessmann Institute for Biomedical Engineering, ETH and University Zurich, Zurich, Switzerland, Center for MR Research (CMRR), University of Minnesota, Minneapolis, Minnesota, United States INTRODUCTION: Ultra-high field strengths and parallel imaging are expected to form a considerable synergy. This has recently been emphasized both by theoretical investigations (1-3) and practical experiments (4,5). However, a key concern raised by these studies is whether or not dielectric resonance interferes with the efficient use of parallel imaging at ultra-high field strength. In the presence of a significant dielectric resonance, coil sensitivity profiles have significant contributions from resonant eigenmodes of the object. These are specific for the geometry of the object rather than for the positioning and geometry of the coil (6). Accordingly, coil sensitivities become more similar, hence potentially preventing the efficient use of parallel imaging. In order to study these effects, parallel SENSE imaging (7) has been performed in the presence of dielectric resonance in two different phantom geometries on a 7 Tesla MRI system. In particular, the impact of conductivity-related dielectric resonance damping was investigated by graded addition of sodium chloride.