The present invention relates to a catheter (2) for applying energy to an object (6) and a magnetic resonance imaging system (1) for localizing the catheter (2). The catheter (2) comprises an energy application element for applying energy to the object (6), and a cavity for providing a magnetic resonance fluid from which magnetic resonance signals generated by the magnetic resonance imaging system (1) are receivable, wherein the cavity is adapted for providing a cooling fluid as the magnetic resonance fluid for cooling the energy application element. The catheter (2) comprises further a tracking coil (15) for tracking the catheter (2), wherein the tracking coil (15) is adapted to receive the magnetic resonance signals from the magnetic resonance fluid. Thus, the magnetic resonance fluid fulfils at least two functions, providing magnetic resonance signals for tracking the catheter (2) and cooling the energy application element.
