A computational procedure for predicting the thermal effects produced by MRI gradient coils in orthopedic implants

This work proposes a numerical procedure for accurately evaluating the energy deposed by MRI gradient coils in bulk metallic prostheses and the consequent temperature increase of the surrounding tissues. An original method, based on a time periodic approach, allows to accurately reproduce the evolution of the phenomena produced by the switching gradient field associated with any MRI sequence. Then, the Pennes’ bioheat equation is solved through the Douglas–Gunn method to compute the time-dependent temperature increase, which can be superposed to the thermal effects caused by the RF fields. As an example, the procedure is applied to evaluate the heating generated inside the body when a patient with a hip prosthesis undergoes a Echo-Planar Imaging (EPI) MRI sequence.