Non-invasive temperature profile estimation in a lossy medium based on multi-band radiometric signals sensed by a microwave dual-purpose body-contacting antenna

Abstract

Microwave radiometry has during the past two decades been investigated as a non-invasive scheme for measurement of subcutaneous tissue temperatures, basically for monitoring and control in hyperthermic treatment of cancer. In this effort, we test a contact-type, dual-purpose antenna with integral water bolus. To overcome conflicting optimization criteria in the integration of this thermometry technique with heat applicators exhibiting a large effective field size during superficial hyperthermia, a stacked configuration design is proposed, where the radiometer receive antenna (Archimedean spiral) is located on the front (skin) surface of the water bolus and the heating antenna (Dual-Concentric Conductor aperture) is placed on the bolus back surface. The motivation is to achieve homogeneous tissue heating simultaneously with non-invasive thermography of the target tissue under the applicator. This paper addresses the feasibility of predicting one-dimensional depth temperature profiles from multi-band brightness temperatures. The performance is investigated statistically by a Monte Carlo technique on both simulated and real heated-phantom data using up to six radiometric bands. Analysis of measured data shows that during the transient heating period in a solid lossy phantom, the inversion technique exhibits a precision (2σT) and skewness (bias) of estimated compared to actual temperature profiles of better than ±0.38°C and ±0.55°C, respectively.