3D computational study of non-invasive patient-specific microwave hyperthermia treatment of breast cancer.

Non-invasive microwave hyperthermia treatment of breast cancer is investigated using three-dimensional (3D) numerical breast phantoms with anatomical and dielectric-properties realism. 3D electromagnetic and thermal finite-difference time-domain simulations are used to evaluate the focusing and selective heating efficacy in four numerical breast phantoms with different breast tissue densities. Beamforming is used to design and focus the signals transmitted by an antenna array into the breast. We investigate the use of propagation models of varying fidelity and complexity in the design of the transmitted signals. An ideal propagation model that is exactly matched to the actual patient's breast is used to establish a best-performance baseline. Simpler patient-specific propagation models based on a homogeneous breast interior are also explored to evaluate the robustness of beamforming in practical clinical settings in which an ideal propagation model is not available. We also investigate the performance of the beamformer as a function of operating frequency and compare single-frequency and multiple-frequency focusing strategies. Our study suggests that beamforming is a robust method of non-invasively focusing microwave energy at a tumor site in breasts of varying volume and breast tissue density.