Objective To show the relevance of a simple finite difference transmission line model to help design safe implanted cables in 1.5T MRI’s using the multi-section cable approach. Materials and methods The transfer function and heating under a given incident field predicted by the finite difference model for two-section cables are compared to full-wave and experimental results. The finite difference model was then used to design a three-section cable considering the phase effects. Results The differences between the predicted transfer function given by the transmission line model with the full-wave results and the experimental results are, respectively, less than 10% and less than 5%. The predicted heating differed by less than 7% with the full-wave results and less than 25% with the experimental results. The optimum lengths of the three-section cable reduces by 51% the worst case heating at the electrodes compared to the best case unique section wire. Discussion The multi-section cable design can reduce the heating of cables in MRI taking into account phase effects. The finite difference transmission line model presented is a simple valuable tool to estimate the worst case heating of simple multi-section cables.