Near-Field Focusing Phased Array for Hyperthermia Application

175 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.A conventional hyperthermia applicator is an electrically small antenna which produces a divergent beam. In this thesis, we propose a focused applicator made of phased arrays. The advantages of an array applicator are (i) smaller input power and less surface heating for achieving the same field intensity at the tumor, (ii) deeper penetration depth as the propagation loss in the human body is partially compensated by the beam focusing effect, and (iii) smaller and electronically scannable 3 dB spot.A theoretical model is developed to analyze a planar phased array for focusing through a dielectric interface at a near-zone point. This model is validated by measurements. We have made an extensive parametric study to optimize the array. A baseline design for a hyperthermia applicator is obtained. It consists of 19 elements of open-ended waveguides arranged in a triangular lattice over a hexagonal planar area of 9.04 x 7.82 cm('2). At the operating frequency 1500 MHz, it requires 100 watts input power to produce a power density 118 mW/cm('3) at the focal point located at 4 cm depth. The diameter of the 3 dB spot is about 2.2 cm. The spot can be moved electronically within the volume of 5 x 5 x 5 cm('3) with at most 1 dB loss in power density. Thus, the performance of the array applicator is significantly better than that of a conventional single-element applicator.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD