Electromagnetic Fields near Implanted Cardiac Devices during Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) is widely used in daily clinical practice for the diagnosis of soft tissue in general and for several cardiac diseases in particular. With the implantation of active devices like pacemakers the patients become unavailable for this means of imaging due to potentially hazardous effects for the patient. Coupling of RF-fields into the device can lead to interference with the electronics and heating of the tissue near to the electrode. Aim of this work was to determine the field distributions inside the patient by means of computer models and numerical field calculation. In a phantom study all examined objects were placed in a saline filled plexiglass phantom which was positioned in the center of a birdcage coil. The frequency of the RF-signal was set to 64 MHz corresponding to 1.5 Tesla MRI systems. The simulations showed that the level of energy absorption near to the metallic object depends on the distance from the center of the phantom as well as the straight length of the wires.