New concepts in the design of phased arrays for hyperthermia

The problem of effective power delivery to a semi-deep target by a phased array has been addressed for application to hyperthermia treatment of some tumors in the thorax. Three efficiencies have been introduced, which estimate system ability in power transfer from generators to body, from body to tumor, and from generators to tumor. They are formulated in terms of a dissipation matrix [H] and an interference matrix [Q]. These efficiencies fall into ranges whose end-points are solutions of extremum problems which can be stated as ordinary or generalized Hermitian eigenvalue problems. Bounds to achievable efficiencies are obtained. The properties of [Q], which allow maximal power transfer to the target, are expressed by a filling index.