Magnetic resonance imaging (MRI) may cause tissue heating in patients implanted with pacemakers, cardioverters/defibrillators, or similar medical devices. As a consequence, these patients, whose number is increasing every year, are often preventatively excluded from MRI investigations. The issue has been studied for several years now, in order to identify the mechanisms involved in heat generation, and define safety conditions by which MRI may be extended to patients with metal implants. In this sense, numerical studies not only widen the range of experimental measurements, but model a realistic patient’s anatomy on which it is possible to study individually the impact of the many parameters involved. In order to obtain reliable results, however, each and every numerical analysis needs to be validated by experimental evidence. In this book both numerical and experimental studies are presented, to analyze thoroughly the mechanisms involved in the MRI-induced heating on metal leads and to understand how far we are from the possibility to define safe conditions for MRI procedures on implanted patients.