High-Resolution Imaging of Narrow Bone Fractures With a Novel Microwave Transceiver Sensor Utilizing Dual-Polarized RIS and SRR Array Antennas

In this study, a new transceiver system is presented for detecting the location and orientation of narrow bone fractures. The system comprises a multilayer patch resonator integrated with a reactive impedance surface as the transmitter and a three-element array of split-ring resonator (SRR) probes as the receiver. It operates at 2.45 GHz in the Industrial, Scientific, and Medical (ISM) frequency band. Dielectric plano-concave lenses are used in the transmitter and receiver to improve impedance matching and adapt to the human body curvature. By using three adjacent SRR probes to divide the area being investigated into smaller sections, the system concentrates power in the fractured region, improving image resolution. The high capacitance of the split gap in the SRR probes allows for precise tracking of small changes. The system performs longitudinal and rotational raster scans to localize bone cracks and achieves an impressive resolution of 1 mm. The experimental measurements were conducted using a gelatin-based arm phantom and a real arm with various healthy and broken bones. The dual-polarized configuration of the system enables effectively detecting the orientation of fractures. The presence of fractures can be determined by comparing the power received from the three SRR probes. When the crack is parallel to the incident
${E}$
-field, the probe directly facing the crack receives more power than the adjacent probes. This power difference is significantly reduced in healthy bone and also when the incident wave is perpendicular to the crack. The results from both measurement and simulation support each other, validating the reliability of the proposed transceiver system.