MULTI-APPLICATOR HYPERTHERMIA SYSTEM DESCRIPTION USING SCATTERING PARAMETERS

Hyperthermia systems using electromagnetic phased arrays have often be en investigated from a SAR distribution point of view. One of the prob lems in these systems is that the achieved SAR distribution is differe nt from the intended one because of changes in the generator signals d ue to mutual coupling beteen applications. The use of circuit theory a nd S-parameters in the description of an N-applicator phased array sys tem is introduced in this paper, and a compact matrix equation giving excitation as a function of generator signals is derived. Measurement of the S-parameters is discussed using a phased array deep heating sys tem (Danish Hyperthermia Foundation (DHF)) as an example. In a phantom experiment a significant improvement in the SAR distribution is demon strated when the developed method is applied.