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.