Enhancing the imaging performance of electrical capacitance tomography for monitoring osseointegrated prostheses

Osseointegrated prostheses (OIP) are an alternative to traditional socket-based prostheses, since amputees can experience an unrestricted range of motion and improved sensory feedback. However, the risk of infection at the tissue-OIP interface is very high. Subcutaneous infections, if undetected at an early stage, can result in prosthesis loosening, bone fracture, and OIP mechanical failure. In order to avoid such issues, most of the current OIP monitoring techniques rely on physicians' inspections and conventional imaging techniques. Recent studies showed that electrical capacitance tomography (ECT), which is inherently noncontact and radiation-free, could potentially be used for imaging OIPs. In addition, embedded passive nanocomposites interrogated by ECT could reveal pH changes indicative of infection. However, the ECT images suffer from limited resolution. Thus, this study investigated a rotational ECT system in which the ECT electrode array is rotated with respect to its central axis to provide additional electric field interrogation patterns and corresponding measurements for solving the ECT inverse problem. The results showed that better quality images could be produced as a result of the increased number of independent boundary measurements. Furthermore, a limited region tomography algorithm was also developed and implemented to image only the region corresponding to the OIP-tissue interface. By limiting the region of interest, the ill-posed nature of the ECT inverse problem was significantly reduced, which resulted in enhanced resolution of the reconstructed images. Proof-of-concept was successfully demonstrated through laboratorybased experimental tests.