Pilot study on monitoring ulcer healing with diffuse optical imaging in a patient cohort affected by peripheral arterial disease (PAD)

Ulcers are a common occurrence in diabetic patients with peripheral arterial disease (PAD). Early prognosis of ulcer healing can help patients avoid prolonged pain and future amputation by alerting physicians to intervention efficacy. However, monitoring of ulcers and predicting intervention success remains a challenge. We have developed a so-called vascular optical tomography imaging system (VOTIS) to address this problem. The system consists of patches with infrared sources and silicon photodiodes. The patches are placed on areas of interest in the lower extremities and light attenuation data is obtained at multiple frames per second. During data acquisition, a thigh cuff is inflated and deflated to affect blood flow to the lower extremities, resulting in dynamic changes of the recorded signals. Features such as maximum change in total absorption, response time to cuff inflation, and plateau time (PT) between cuff inflation and deflation can be extracted. Here we report on a pilot study of 10 PAD patients (70% diabetic) with ulcers, who had a surgical intervention to improve blood flow. VOTIS measurements were obtained immediately after the intervention, and again three weeks later. Prognosis was determined from EHR and classified as improvement (N=7) - when an ulcer reduces in size - or no improvement (N=3). In an ROC analysis, the VOTIS-derived biomarker PT demonstrated high classification potential (Sn=86%, Sp=100%, AUC=0.95).