Annular Slot Biomedical Antenna for Combined Microwave Heating and Infrared Thermography of the Tissue

A previously introduced annular slot antenna (ASA), utilized for combined microwave heating and radiometry for blood perfusion measurement of tissues, is modified to replace microwave radiometry with infrared thermography. Infrared (IR) thermography is a more convenient and cost effective alternative to microwave radiometry for skin/ superficial and small animal (such as mice and rat) applications. An area with removed metallization is introduced around the central axis of the circular shape ASA, used for heating at 2.4 GHz. The S-11 resonance frequency and/ or depth change with the size of this area. Moreover, a hole at the middle of this area, made across the antenna, from top to bottom, allows the infrared beam to reach the skin. Simulations and measurement show that the presence of this hole has minimal impact on the performance of the ASA in terms of S-11 and specific absorption rate (SAR) profile. In addition, the preliminary result of an IR camera captured images for a heating episode (2 W, at 2.45 GHz), conducted on a tissue phantom, is reported. Temperature rise of 5.7 degrees C after 1 minute is observed at the center of the hole.