Wearable Loops for Unobtrusive Electromagnetic Detection of Joint Effusion

Joint effusion is associated with synovial fluid build-up in or around a joint. Current state-of-the-art medical imaging methods such as X-ray, ultrasound, and Magnetic Resonance Imaging (MRI) can provide high-resolution images but are resource-intensive and limited to specialized medical facilities, preventing them from being used for long-term, continuous and real-time monitoring. In this work, we propose an alternative, wearable method for detecting joint effusion which addresses these shortcomings. The method relies on monitoring changes in the transmission coefficient (S21) between two conducting loops placed around the limb near the joint region. Using electromagnetic simulations on a simplified arm-effusion model, a clear trend is presented between the magnitude/phase of S21 and effusion radius. Particularly, for the best design, 0.5-cm variations from 1 to 3 cm in spherical effusion radius can be detected with a minimum required S21 precision of 1.02 dB for magnitude or/and 13.50° for phase. Significance of this approach lies in early stage detection and ease of treatment for such medical conditions.