OPTIMIZATION OF THE DEPOSITED POWER DISTRIBUTION INSIDE A LAYERED LOSSY MEDIUM IRRADIATED BY A COUPLED SYSTEM OF CONCENTRICALLY PLACED WAVE-GUIDE APPLICATORS

A method is proposed for controlling the deposited power distribution in a layered cylindrical lossy model, irradiated by a phased-array hyp erthermia system consisting of four waveguide applicators. A rigorous electromagnetic model of the heated tissue, which takes into account c oupling phenomena between system elements, is used for predicting the electric held at any point inside tissue, The relative amplitudes and relative phases of the array elements are optimized in order to attain desired specific absorption rate (SAR) distributions inside and outsi de malignant tissues. A constrained nonlinear optimization problem is solved by using the penalty function method and the resulting unconstr ained minimization of the penalty function is carried out by the downh ill simplex method. Two practical phased-array hyperthermia systems ha ve been studied and numerical results are presented.