@article {15_PMB_ConvexImplant, title = {Convex optimization of MRI exposure for mitigation of RF-heating from active medical implants}, journal = {Physics in Medicine and Biology}, volume = {60}, number = {18}, year = {2015}, pages = {7293}, abstract = {Local RF-heating of elongated medical implants during magnetic resonance imaging (MRI) may pose a significant health risk to patients. The actual patient risk depends on various parameters including RF magnetic field strength and frequency, MR coil design, patient{\textquoteright}s anatomy, posture, and imaging position, implant location, RF coupling efficiency of the implant, and the bio-physiological responses associated with the induced local heating. We present three constrained convex optimization strategies that incorporate the implant{\textquoteright}s RF-heating characteristics, for the reduction of local heating of medical implants during MRI. The study emphasizes the complementary performances of the different formulations. The analysis demonstrates that RF-induced heating of elongated metallic medical implants can be carefully controlled and balanced against MRI quality. A reduction of heating of up to 25 dB can be achieved at the cost of reduced uniformity in the magnitude of the $\#$$\#$IMG$\#$$\#$ [http://ej.iop.org/images/0031-9155/60/18/7293/pmb516939ieqn001.gif] {$B_{1}^{+} $} field of less than 5\%. The current formulations incorporate a priori knowledge of clinically-specific parameters, which is assumed to be available. Before these techniques can be applied practically in the broader clinical context, further investigations are needed to determine whether reduced access to a priori knowledge regarding, e.g. the patient{\textquoteright}s anatomy, implant routing, RF-transmitter, and RF-implant coupling, can be accepted within reasonable levels of uncertainty.}, url = {http://stacks.iop.org/0031-9155/60/i=18/a=7293}, author = {J C{\'o}rcoles and E Zastrow and N. Kuster} }