Noninvasive Internal Body Temperature Tracking With Near-Field Microwave Radiometry

This paper presents a study of near-field radiometry for internal temperature measurements of the human body. The radiometer has a Dicke architecture and operates in the 1.4-GHz quiet band for centimeter penetration into tissues with minimized radio frequency interference (RFI). The total blackbody power from a tissue stack is received by a probe placed on the skin, designed to receive a high percentage of the total power from a buried tissue layer. Temperature retrieval for subsurface tissue layers is performed using near-field weighting functions obtained from full-wave simulations. The calibrated radiometer is demonstrated to track the temperature of a phantom muscle tissue layer under phantom fat and skin layers within a fraction of a degree. It is shown that RFI can be reduced through the use of a second probe and adaptive processing. Measurements on the human cheek show good agreement with independent thermocouple measurements inside the mouth.