Smartphone-Based Infrared Thermography as an Option for Evaluating the Treatment Effect of Revascularization Procedure in Patients With Peripheral Arterial Disease, a Prospective Study

Abstract

Infrared imaging has been used to assess peripheral perfusion; however, large, heavy, and prohibitively expensive cameras have precluded its adoption for widespread clinical applications. With advent of more affordable and portable infrared cameras in recent years, they have become more accessible for clinical use. In this study, we aim to introduce the use of smart phone based thermal camera using thermal ankle-brachial index (TABI) to assess the perfusion in peripheral arterial disease (PAD)-affected lower extremities both preintervention and postintervention and simultaneously comparing with ABI. To our knowledge, this is the first study in the Indian scenario. We included 52 patients with 67 lower limbs with PAD requiring revascularization who presented to our institute between July 2020 and December 2021 in the study. Revascularization procedures included endovascular or open surgical bypass. ABI was measured in affected lower limb using Handheld Doppler device before revascularization, after revascularization at discharge and at 1-month follow-up after revascularization. Thermal images of upper and lower limbs were obtained using FLIR ONE PRO (a smartphone-based infrared thermal camera) at the time of measuring ABI. TABI was calculated by dividing maximum lower limb temperature by maximum upper limb temperature. ABI and TABI were compared for correlation using Pearson analysis. After revascularization, there was statistically significant improvement in ABI, 0.38 ± 0.20, t(66) = 15.1; P < .001, and TABI, 0.09 ± 0.053, t(66)=14.2; P < .001, at discharge when compared with before intervention (Table). Before intervention, positive correlation was found between ABI and Lower limb temperature (r = 0.973; P < .001) and ABI and TABI (r = 0.810; P < .001). After intervention at discharge, positive correlation was found between ABI and Lower limb temperature (r = 0.682; P < .001) and ABI and TABI (r = 0.662; P < .001). At the 1-month follow-up after intervention, positive correlation was found between ABI and Lower limb temperature (r = 0.874; P < .001) and ABI and TABI (r = 0.663; P < .001). Smart phone-based thermal imaging can be used to assess perfusion status in PAD in clinical settings as non-invasive, portable, cost effective and reproducible alternative to ABI. It has shown improvement in perfusion status corresponding to standard Doppler ABI.TableShowing descriptive analysis of revascularized lower limbsBefore interventionAfter intervention at dischargeAt the 1-month follow-upABITABILower extremity temperature (℉)Ambient temperature (℉)ABITABILower extremity temperature (℉)Ambient temperature (℉)ABITABILower extremity temperature (℉)Ambient temperature (℉)Mean.28.8382.786.4.67.9392.986.8.68.9492.987.7Median.27.8382.988.4.67.9592.688.4.67.9692.688.2Std deviation.21.044.219.40.22.065.779.54.17.055.348.64Minimum.00.7574.864.0.00.7879.560.8.00.7878.664.2Maximum.83.9796.6101.41.11.02103.6102.31.11.02103.1102.3Range.83.2221.837.41.1.2424.141.51.1.2424.538.1Interquartile range.28.045.37.90.21.1010.137.35.19.099.456.67TABI, Thermal ankle-brachial index. Open table in a new tab