The invention concerns a system capable of generating a magnetic indication B0 comprising gradients (Gx, Gy, Gz) in certain directions, transmitting ratio frequency wave pulse sequences (RF) perpendicular to B0 in a range of adjustable frequencies, and detecting electromagnetic signals received from a body part (4). The method includes injecting a contrast product in said body part, capable of being temporarily fixed in an observed zone (1), and comprising an element capable of causing chemical displacement of a resonance frequency of water hydrogen protons; exciting said body part, using a radio wave pulse sequence; in a range of frequencies adjusted on the basis of the magnetic induction B0 and the chemical displacement for some of said waves; detecting the electromagnetic signals received in said body part, substantially corresponding to the magnetic resonance signals of the protons of the observed zone having undergone the chemical displacement.