Combining reflector focused and phased array beamforming for microwave diagnosis and therapy

Abstract

In this paper we continue our recently reported work on the exploitation of the focusing properties of a conductive ellipsoidal reflector in conjunction with directive phased antenna configurations in order to achieve diagnosis and therapy at the microwave frequency regime. Both aforementioned modules are parts of a hybrid microwave radiometry and hyperthermia system comprising a symmetrical axis ellipsoidal conductive wall cavity which ensures the necessary beamforming and focusing on the body/brain areas of interest. The proposed system operates in an entirely non-invasive contactless manner providing temperature and/or conductivity variations monitoring while it is also designed to provide hyperthermia treatment. Recently, the effect of the use of patch antennas as receiving or emitting elements on the system's focusing properties and specifically the use of two-element phased array setups to achieve scanning of the areas under measurement was investigated. In the present paper, four element antenna setups are used and extensive simulations to compute the electric field distributions inside the whole ellipsoidal reflector and inside two types of human head models were carried out. The results show that clear focusing (creation of “hot spots”) inside the head models is achieved at 1GHz. In the case of the four element antennas, the “hot spot” performs a linear scan around the brain area of interest while the phase values of the four antenna elements significantly affect the way the scanning inside the head model is achieved. The proposed setups enhance and increase the dimensions and scanning of the focusing area toward the acquisition of tomography images without the need of subject movement.