Smartphone-mounted infrared thermography to assess success of open lower limb revascularisation

Abstract

40% of major complications after infrainguinal bypass surgery are found to be related to early graft failure. Current available diagnostic tests have a number of limitations in assessing lower limbs postoperatively. Low-cost smartphone-mounted infrared cameras have been recently validated in assessing arterial lower limb blood flow. This study will assess the role of infrared thermography for the early detection of bypass graft thrombosis following open revascularisation surgery of the lower limbs by looking at temperature differences between the feet pre-operatively and post-operatively. A prospective study was carried out on patients undergoing elective open infrainguinal lower limb bypass surgery for peripheral arterial disease (PAD) at Mater Dei Hospital in Malta. Data collection was done in three stages: at time point 0 i.e. pre-operatively, at time point 1 i.e. day one postoperatively, and at time point 2 i.e. between day five and day seven post-operatively. Clinical examination and non-invasive tests (Doppler waveforms, ABPI and toe pressures) were carried out for both the treated leg i.e. the leg undergoing the infrainguinal bypass surgery, and the non-treated leg i.e. the contralateral leg. Thermal images were captured using a smartphone-mounted infrared thermal camera and temperatures at six different region of interest (ROI) in both feet were recorded. A total of 17 patients were eligible for this study. A temperature difference between the feet was noted at all time points. Temperature readings at the six ROI of the treated leg were higher than those of the non-treated leg at all time points, reaching a statistical significance at time point 1 and time point 2 with a p-value <0.005. The mean foot temperature difference between the treated leg and the non-treated leg was found to be 5.99 degrees Celsius and 4.09 degrees Celsius at time point 1 and time point 2 respectively. A low-cost smartphone-mounted infrared thermal camera can be used to assess perfusion of the treated leg following open infrainguinal bypass surgery by looking at temperature differences between the feet post-operatively. This is a non-invasive, non-contact, and user friendly device. Further studies should be considered to standardise thermograms in such patients post-operatively.