The effects of an internally placed metallic bar on the thermal distribution in agar phantom by RF hyperthermia were studied. There was no hot spot when the metallic-bar was parallel to both electrodes, whereas hot spots were there in both edges of the bar if the bar was perpendicular to the electrodes. In the clinical application of RF hyperthermia, we treated one patient with recurrent sacral tumor (synovial sarcoma) who had metallic bar implants in his lumbosacral region. As we applied the electrodes parallel to the metallic implants, he could receive RF hyperthermia safely and effectively fourteen times without any complication. It is important to give careful considerations to spatial relation of electrodes and metal when treating patients who have metallic implants.
