A magnetic resonance imaging system is provided with one or more electrical accessory devices, for example, catheters (10) or RF surface coils (6), which are intended for use during the examination of an object, as well as with a connection lead (13) which is arranged so as to extend through an examination zone (1) of the magnetic resonance imaging apparatus, which zone can be exposed to an RF field, and to connect the accessory device to a connection unit (12). In order to avoid heating of the connection lead (13) due to common mode currents induced in the connection lead by the RF field, which currents could lead to injury of a patient or damage of the accessory device or the connection unit (12), the connection lead (13) comprises at least two lead segment (131, 132, . . . ) which are coupled to one another via a transformer (141) and at least one matching network (151, 152) comprising at least one T-, L- and/or .pi.-quadrupole, which each comprise at least two impedance elements in the form of a capacitor and/or an inductivity, between a lead segment (131; 132) and the inductive coupling element (141) for matching the impedances of both.