Microwave-based sensing for tissue analysis is recently gaining interest due to advantages such as non-ionizing radiation and non-invasiveness. We have developed a set of transmission sensors for microwave-based real-time sensing to quantify muscle mass and quality. In connection, we verified the sensors by 3D simulations, tested them in a laboratory on a homogeneous three-layer tissue model, and collected pilot clinical data in 20 patients and 25 healthy volunteers. This report focuses on initial sensor designs for the Muscle Analyzer System (MAS), their simulation, laboratory trials and clinical trials followed by developing three new sensors and their performance comparison. In the clinical studies, correlation studies were done to compare MAS performance with other clinical standards, specifically the skeletal muscle index, for muscle mass quantification. The results showed limited signal penetration depth for the Split Ring Resonator (SRR) sensor. New sensors were designed incorporating Substrate Integrated Waveguides (SIW) and a bandstop filter to overcome this problem. The sensors were validated through 3D simulations in which they showed increased penetration depth through tissue when compared to the SRR. The second-generation sensors offer higher penetration depth which will improve clinical data collection and validation. The bandstop filter is fabricated and studied in a group of volunteers, showing more reliable data that warrants further continuation of this development.

The microwave sensing technique is a possible and attractive alternative modality to standard X-rays, magnetic resonance imaging, and computed tomography methods for medical diagnostic applications. This technique is beneficial since it uses non-ionizing radiation and that can be potentially used for the microwave healthcare system. The main purpose of this paper is to present a microwave sensing technique to analyze the variations in biological tissue thickness, considering the effects of physiological and biological properties on microwave signals. In order to fulfill this goal, we have developed a two-port noninvasive sensor system composed of two split ring resonators (SRRs) operating at an Industrial, Scientific, and Medical (ISM) frequency band of 2.45 GHz. The system is verified using the amplitude and phase of the transmitted signal in ex-vivo models, representing different tissue thicknesses. Clinical applications such as the diagnosis of muscular atrophy can be benefitted from this study.

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