An accurate simulator for MR coil sensitivity estimation

Coil sensitivity estimation in Magnetic Resonance experiments requires the knowledge of biological sample induced resistance. In dependence on system geometry, many authors studied sample-coil interaction by using very simple coil geometry (circular, square, etc.) and homogeneous infinitely long cylinders, spheres or half-spaces as approximations of the sample geometry. However, in real MR experiments, both shape and dimensions can be very different respect to these coil and sample models. In this paper we propose the application of Finite-Difference Time-Domain method for sample induced resistance estimation. The developed approach can be used as a tool to estimate sample induced resistance in complex receiving systems, without approximations in sample and coil geometries. Calculation of both sample induced resistance and magnetic field pattern permits to estimate coil sensitivity for optimal coil design in dependence on the sample size and geometry. Comparison with experimental data, performed on two home-built saddle coils, demonstrated the great accuracy of the developed method.