Electromagnetic Method for Sample Induced Resistance Calculation of Magnetic Resonance Coils

SNR calculation in Magnetic Resonance experiments requires the knowledge of biological sample resistance value. In dependence on system geometry, many authors studied sample-coil interaction by using quasi-static approach, with very simple coil geometry (circular or square) and homogeneous infinitely long cylinders, spheres or half-space as an approximation of the sample geometry. However, in real MR experiments, both shape and dimensions can be very different respect to these coil and sample models. Moreover, quasi-static method fails at high field MR imaging. In this paper we propose a theoretical algorithm for sample resistance estimation which use a numerical solver based on Finite-Difference Time-Domain method for simulating MR systems, without approximations in sample and coil geometries. Comparison with experimental data, performed on a home-built simple coil, demonstrated the great accuracy of the developed algorithm. The proposed method can be used as a tool to estimate sample resistance values for more complex geometries.