Techniques are provided for controlling magnetic resonance imaging (MRI) systems for imaging patients having implantable medical devices. In one example, a scaling factor is determined based on maximum local specific absorption rate (SAR) values for patients with implants and for patients without implants. The MRI determines the radio-frequency (RF) power and flip angle sequences to be used for a given patient, without regard to the presence of an implanted device. However, for patients with implanted devices, the MRI reduces its RF power or adjusts its flip angle sequences based on the scaling factor so as to ensure that the local SAR within the patient does not exceed acceptable levels. In other examples, rather than reducing the RF power of the MRI or adjusting the flip angles, blankets or pads formed of RF power attenuating materials, such as dielectrics, are positioned around the patient near the implantable device, to reduce the RF power incident tissues adjacent the device.