Ultrawide-Band Microwave Space–Time Beamforming for Hyperthermia Treatment of Breast Cancer: A Computational Feasibility Study

Abstract
A new noninvasive ultrawide-band (UWB) microwave method for hyperthermia treatment of breast cancer is proposed. A train of UWB pulses are passed through a space-time beamformer and transmitted simultaneously from multiple antennas into the breast. The filters in the space-time beamformer are designed to compensate for dispersive propagation through breast tissue so that the pulses from each antenna add coherently at the treatment location and add incoherently elsewhere. Thus, the transmitted microwave energy is tightly focused at the treatment location to produce localized heating. The effectiveness of this procedure is shown by calculating the power density deposited in the breast using finite-difference time-domain (FDTD) electromagnetic simulations of realistic numerical breast phantoms derived from magnetic resonance images of patients. Both supine and prone patient configurations are considered. The robustness of our approach to variations in breast density and heterogeneity is demonstrated. We also present examples of temperature distributions calculated using the FDTD method applied to a simple thermal model for the breast phantoms. The results illustrate that, within the confines of this model, our UWB approach achieves sufficiently elevated temperatures in the vicinity of small tumors while maintaining safe temperatures throughout the remainder of the breast. The promising outcome of this feasibility study suggests that further development of this technique should be pursued.