Design of RF needle applicators for optimum SAR distributions in irregularly shaped tumors

The impedance method has been used to obtain specific absorption rate (SAR) distributions for a model of a brain tumor for which the shape was determined from CT head scans. Different locations of 4, 5, or 6 needles were used to obtain optimum arrangements that gave minimum standard deviations (SDs) for the SARs in the volume of the tumor. Further work, presently underway, will develop the thermal model to obtain 3-D temperature distributions for the tumor and its surrounding volume to help design applicators giving tumor temperatures with minimum SDs. The procedure described should be applicable for treatment planning of thermotherapy for a number of tumors for which local hyperthermia by RF needle applicators has been found useful.