Progress toward radiometry controlled conformal microwave array hyperthermia applicator

The purpose of this effort is to produce a microwave applicator that can heat skin and superficial disease overlying large areas of contoured anatomy with minimal setup complexity and maximum patient comfort. We describe the design of a 3-layer printed circuit board (PCB) array of independently driven Dual Concentric Conductor (DCC) microwave antennas intended for heating tissue, interspersed with a second set of concentrically mounted receive mode antennas to be connected by a multiplexing switch to the input of a radiometer for measuring temperature dependent emissions from tissue. Results of applicator heating performance are given demonstrating the controllability of power deposition in homogeneous muscle phantom as well as the uniformity of steady state temperature in a patient with chestwall recurrence of breast carcinoma. Because adequate temperature monitoring of large contoured tissue regions is difficult to accomplish with probe technology, this effort includes initial feasibility studies of adding microwave radiometry sensing of temperature under each heat aperture. Preliminary results characterize the measurement region of a spiral microstrip receiving antenna when mounted concentrically inside a DCC heating aperture, and demonstrate the linear correlation of radiometer-recorded brightness temperature as a function of load temperature when measured through an intervening 5 mm thick water bolus at 40°C. The data clearly indicate that complimentary heating and radiometry antennas may be combined in a thin and flexible microstrip array applicator for time-sequenced microwave heating and non-invasive temperature monitoring of large contoured superficial tissue regions