supply 4 in order to generate imaging sequences comprising rf pulses and temporary magnetic gradient fields after excitation of nuclear spins in a part of the body placed within the examination space the receiver coil 5 receives an mr signal the phase and amplitude derived therefrom are sampled and further processed in the amplification and demodulation unit 10 an image reconstruction unit 12 processes the signals presented so as to form an image via an image processing unit 13 this image is displayed for example on a monitor 14 the control unit 11 also controls the image reconstruction unit 12 the image processing unit 13 and a catheter power supply unit 16 fig1 also shows a catheter 15 as an embodiment of an invasive device the catheter 15 comprises a coil not shown which is connected to the catheter power supply unit 16 fig2 shows a detailed embodiment of the catheter the catheter 15 comprises a duct 20 a distal end 21 a proximal end 22 and the coil 23 the catheter 15 is made of an electrically suitably insulating material of low magnetic susceptibility the catheter 15 has a diameter which is for example between 0 3 mm and 3 mm and has a fixed length in a range of for example from about 110 to 150 cm for the remainder the catheter 15 has a customary shape and construction including a hull 24 the duct 20 may be optional the coil 23 is provided for example near the distal end 21 directly underneath the surface and adjacent the duct 20 in the catheter 15 the coil 23 consists of a non magnetic conductive material for example copper wire having a diameter of for example 0 1 mm the coil is.