Single-frequency and multiband microwave radiometry for feasible brain conductivity variation imaging during reactions to external stimuli

Recent research results imply that microwave radiometry may exhibit the capability of detecting local variations of the conductivity attributes of the media under measurement. The contactless measurements in question are a function of the geometrical spatial properties of a newly developed microwave radiometry imaging system (MiRaIS), comprising an ellipsoidal conductive wall cavity. The proposed methodology is based on single-frequency and multiband microwave radiometry in conjunction with the implementation of an ellipsoidal reflector to achieve focusing on the areas of interest. The theoretical fundamentals as well as an overview of the system modules and past experimental results are herein presented, forming the background and context on which current and future research is based. Experimentation using small water phantoms in order to verify the system's focusing properties and saline solution phantoms in order to investigate the system's capability of sensing conductivity changes at various microwave frequencies with a sensitive multiband receiver has been conducted. The results show that local resistance variations in small phantoms can be detected at microwave frequencies by the MiRaIS. Combining these experimental data with previous human experimental results, the feasibility of brain conductivity variation imaging during reactions to external stimuli by the proposed system is examined and discussed in the present paper.