The invention provides for a magnetic resonance imaging (MRI) (100) system comprising a main magnet (102) with an with an adjustable main magnetic field. The MRI system further comprises a current source (124) for supplying RF current between multiple electrodes (122, 122') divided between a first portion (122) and a second portion (122'). The current source is configured for supplying the RF current between the first portion and the second portion. Execution of the machine executable instructions cause a processor controlling the MRI system to: set (200) the average magnetic field strength within the imaging zone to a first value； set (202) the average magnetic field strength within the imaging zone to a second value, the second value is lower than the first value； control (204) the current source to have a known RF current (144) travel between the first portion of the electrodes and the second portion of the electrodes； acquire (206) the magnetic resonance data from the subject by controlling the magnetic resonance imaging system with readout gradient commands according to a three-dimensional imaging protocol； reconstruct (208) three-dimensional image data (148) from the magnetic resonance data； and calculate (210) a resistive model (150) of the subject using the three-dimensional image data and the known RF current through the electrodes.L'invention concerne un système d'imagerie par résonance magnétique (IRM) (100) comprenant un aimant principal (102) avec un champ magnétique principal réglable. Le système d'IRM comprend en outre une source de courant (124) destinée à fournir un courant RF entre de multiples électrodes (122, 122') divisées entre une première partie (122) et une seconde partie (122'). La source de courant est configurée pour fournir le courant RF entre la première partie et la seconde partie. L'exécution des instructions exécutables par une machine amène un processeur commandant le système d'IRM à : régler (200) l'intensité de champ magnétique mo
