Figures of merit and their bounds in radiofrequency heating by phased arrays

Purpose: 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 tumours in the thorax. Methods: Three efficiencies have been introduced, which estimate system ability in power transfer from generators to body, from body to tumour, and from generators to tumour. They are formulated in terms of a dissipation matrix and an interference matrix. Bounds to achievable efficiencies are obtained. Further figures of merit have also been introduced. The necessary mathematics has been developed. Results: A numerical analysis has been carried out for a partially interdigitated planar array of resonant dipoles. Results show how the new parameters can be exploited for optimal selection of the array’s degrees of freedom. Conclusion: The figures of merit and their bounds allow comparisons between RF heating devices and provide guidelines to phased array design.