Gabriel A Wallace1, Niten Singh1, Elina Quiroga1, Nam T Tran2. 1. Division of Vascular Surgery, Department of Surgery, Harborview Medical Center, University of Washington, Seattle, WA. 2. Division of Vascular Surgery, Department of Surgery, Harborview Medical Center, University of Washington, Seattle, WA. Electronic address: nam@uw.edu.
Abstract
BACKGROUND: Ankle-brachial index (ABI) is a reliable method to evaluate extremity perfusion but can be prohibitive to obtain secondary to patient discomfort or extremity trauma. This study investigates smart phone-based forward looking infrared imaging to assess peripheral perfusion using thermal ABI (tABI). METHODS: ABIs were measured by a certified vascular laboratory. Thermographs of each extremity (hands/feet) were obtained, and maximum surface temperature was recorded. tABI was calculated by dividing the lower extremity (LE) temperature by the upper extremity (UE). ABI and tABI were compared using Pearson's correlation and Bland-Altman plot. RESULTS: Twenty-three patients (45 limbs) had ABI's and thermographs recorded on the same day. Median ABI was 0.89 (range 0.33-1.46, IQR 0.4). Median LE temperature was 83.0°F (range 60.7-96.9°F, IQR 14.1). Median UE temperature was 91.2°F (range 81.9-94.6°F, IQR 3.4). Median tABI was 0.93 (range 0.33-1.4, IQR 0.2). Positive correlation was seen between ABI and tABI with Pearson analysis (r = 0.83, P < 0.0001) and Bland-Altman plot (bias -0.01, LOA -0.13 to -0.12). CONCLUSIONS: Thermal imaging correlates with ABI in the evaluation of extremity perfusion. Smart phone-based FLIR can be used to determine peripheral perfusion in clinical settings where ABI is difficult to obtain.
BACKGROUND: Ankle-brachial index (ABI) is a reliable method to evaluate extremity perfusion but can be prohibitive to obtain secondary to patient discomfort or extremity trauma. This study investigates smart phone-based forward looking infrared imaging to assess peripheral perfusion using thermal ABI (tABI). METHODS: ABIs were measured by a certified vascular laboratory. Thermographs of each extremity (hands/feet) were obtained, and maximum surface temperature was recorded. tABI was calculated by dividing the lower extremity (LE) temperature by the upper extremity (UE). ABI and tABI were compared using Pearson's correlation and Bland-Altman plot. RESULTS: Twenty-three patients (45 limbs) had ABI's and thermographs recorded on the same day. Median ABI was 0.89 (range 0.33-1.46, IQR 0.4). Median LE temperature was 83.0°F (range 60.7-96.9°F, IQR 14.1). Median UE temperature was 91.2°F (range 81.9-94.6°F, IQR 3.4). Median tABI was 0.93 (range 0.33-1.4, IQR 0.2). Positive correlation was seen between ABI and tABI with Pearson analysis (r = 0.83, P < 0.0001) and Bland-Altman plot (bias -0.01, LOA -0.13 to -0.12). CONCLUSIONS: Thermal imaging correlates with ABI in the evaluation of extremity perfusion. Smart phone-based FLIR can be used to determine peripheral perfusion in clinical settings where ABI is difficult to obtain.
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