Microwave Technique for Brain Monitoring: State of the Art, Promising Applications, Challenges, and Future Directions

The brain is considered one of the central organs constituting complex biological phenomena that reflect upon the health and well-being of a person. Wearable brain monitoring systems have witnessed increased research and technological achievements in the last two decades. Microwave-based techniques have demonstrated high potential for brain monitoring and have technological benefits, such as non-ionizing radiation, small size, cost-effectiveness, portability, non-invasive operation, and good penetration depth. This review aims to present a critical analysis of research on the utilization of microwaves for brain monitoring. Followed by a comprehensive literature search and thematic analysis, four Research Questions (RQs) related to microwave systems in brain monitoring are formulated and studied. In response to these RQs, the key approaches for microwave modeling of the human brain are explored. Further, a brief outline of different applications focusing on developments in microwave systems for brain temperature measurement, stroke detection, intracranial pressure (ICP) monitoring, and skull fracture detection are elaborated. Additionally, thematic analysis is presented in each application area on inter-technology comparison of the microwave technique with other technologies. Further, the challenges in the development of microwave systems and their clinical usage in different brain monitoring setups are explored along with future directions. This review can serve as a platform for brain researchers to understand the potential of the emerging microwave technology for brain monitoring.