Non-invasive monitoring of diabetic foot ulcers healing process by using optical-thermal imaging techniques

Visual assessment is the gold standard for monitoring diabetic foot ulcers (DFUs), a clinical procedure that is sometimes subjective. Non-invasive imaging techniques have become a potential approach for DFUs' objective monitoring. In this regard, it has been hypothesized that the healing process of DFUs can be non-invasively monitored in terms of physiological parameters related to tissue oxygenation and temperature. This research presents a pilot study that was conducted by using an optical-thermal imaging setup, that uses near-infrared spectroscopy (NIRS) and thermal imaging. The objective was to assess the healing status of DFUs with different manifestations. Clinical conditions included post-amputee, normal healing, non-healing, and infected cases. All the patients were recruited by following a clinical protocol of inclusion. Tissue oxygenation parameters in the wound and surrounding areas of the DFU were estimated by applying the Modified Beer-Lambert Law (MBLL) to diffuse reflectance images acquired with a custom-made smartphone-based NIRS scanner, and thermal variations in the wound and periwound areas were detected using a commercial mobile thermal camera. Preliminary results showed that (1) optical imaging has the potential to distinguish healing and non-healing cases using wound:surrounding contrast ratios in terms of total hemoglobin and oxygen saturation; and (2) thermal imaging can detect early signs of infections, that weren’t detected by visual assessment or optical imaging, by assessing its temperature variation across time. Ongoing studies regarding a quantitative analysis are discussed to present a wound:periwound temperature ratio, and its relationship with the oxygenation parameters that present a potential approach for DFUs objective monitoring.