RFID Thermal Monitoring Sheet (R-TMS) for Skin Temperature Measurements during Superficial Microwave Hyperthermia Treatment

Hyperthermia is a widely used anti-cancer treatment that exploits the interactions between high-power electromagnetic fields and the human tissues to locally release a great amount of power in the underlying tissue regions. The electromagnetic source is generally outside the body, in close proximity to the skin. Thus, dangerous hotspots may occur within the skin, and hence continuous monitoring of the superficial temperature distribution is required throughout the treatment. Current Thermal Monitoring Sheets (TMSs), that are grids of many temperature sensors, have some limitations in terms of poor spatial resolution and high thermal conduction errors. Passive Ultra High Frequency (UHF) Radio Frequency IDentification (RFID) devices could offer an attractive alternative thanks to their wireless nature, low-invasiveness, and demonstrated good on-skin performance, especially for temperature monitoring. The preliminary design of an RFID-based Thermal Monitoring Sheet (R-TMS) is presented in this paper as a planar array of circular loop antennas with temperature-sensing-oriented RFID ICs. Both sensing and electromagnetic requirements of the R-TMS are addressed by means of numerical simulations. It proved capable of transmitting the collected temperature data with a remarkable spatial resolution, yet without interfering with the effectiveness of the hyperthermia treatment nor inducing unwanted hotspots over the skin.