We introduce a general description of the RF response of an implant, defined as the implant response matrix (IRM). An analytical expression for the IRM is derived through basis functions that depend on a limited number of parameters. This analytical model is validated with a simulation study (Pearson correlation coefficients with simulations R: 0.9979-0.9996). This description allows a significant reduction in unknowns enabling IRM assessment by MRI measurements without hardware modifications to scanner or implant. The feasibility of MRI based IRM/TF measurement is shown in silico. With the simulated complex B1+ fields the IRM is accurately reconstructed (R: 0.974).