Coherent ultra-wideband radar-on-chip for biomedical sensing and imaging

Abstract

Medical microwave imaging (MWI) has been investigated in the past two decades due to the attractive properties of microwave radiation: Electromagnetic waves at microwave frequencies can penetrate biological tissue and are non-ionising. Several MWI prototypes have been developed for breast cancer imaging and stroke detection, some of which are currently under clinical investigation. The recent innovation of coherent ultra-wideband (UWB) radar-on-chip (RoC) technology could enable MWI at a much lower cost and with portable or even wearable devices. Due to the ability to operate multiple RoC receivers simultaneously, multistatic radar data can be acquired at a much higher rate than when using conventional microwave techniques. This would allow for dynamic imaging of the cardiovascular system: An application which has been mostly out of reach for MWI systems. This thesis describes the work undertaken to investigate the use of coherent UWB RoC technology for biomedical sensing and imaging, specifically of the cardiovascular system. Imaging hardware was developed by research partners University of Oslo and sensor company Novelda. A modular system of simultaneously operated RoC transceivers with body-coupled antennas was constructed. Original contributions were made by generating system requirements, characterising MWI hardware, developing signal processing and imaging algorithms, and experimentally validating the system in human participants. More specifically, microwave interactions with biological tissues along with the anatomy and physiology of the cardiovascular system were considered to generate system requirements. Developed hardware was tested and characterised experimentally and its feasibility for in-body sensing and imaging was assessed. Sensing experiments were performed with a single radar module, to demonstrate the ability of monitoring cardiovascular dynamics in the human body, and to explore the challenges associated with in-body radar signal processing. Finally, different antenna arrays with multiple synchronised radar modules were used to perform two-dimensional imaging: Dynamic imaging of both the femoral artery and the heart were demonstrated, as well as static imaging of a tissue-mimicking phantom. Simulated data were used to inform and optimise imaging algorithms. To our knowledge, this work was the first to demonstrate imaging in the human body using UWB RoC technology, and the second work to demonstrate dynamic MWI. Although many challenges remain, this work signifies that RoC technology could potentially enable accessible and low-cost devices for the assessment of cardiovascular function.