Supplementary Material for: Long-Wave Medical Infrared Thermography: A Clinical Biomarker of Inflammation in Hidradenitis Suppurativa/Acne Inversa

Background: A more reliable classification of skin inflammation and severity of active disease results from ultrasound sonography and the new hidradenitis suppurativa/acne inversa (HS) classification system IHS4. However, an objective assessment of skin inflammation in a continuous mode is still the ultimate goal. Long-wave medical infrared thermography (MIT) may offer a blood flow and temperature differential assessment in inflammatory conditions. Objective: To evaluate the application of MIT in HS. Methods: Standardized photography of the areas involved or previous candidates for HS involvement was performed and MIT pictures were taken simultaneously and superimposed on the photographs of 18 patients (11 female, 7 male, median age 38.75 years [95% confidence interval 28.5–51 years], Hurley score I 5.6%, Hurley score II 38.9%, and Hurley score III 55.5%). A modification of the Otsu method facilitated the automatic lesion segmentation from the background, depicting the inflammation area. Moreover, MIT was administered in real-time mode during radical HS surgery. Results: A 1°C temperature difference from a corresponding symmetric body region was indicative of inflammation. MIT figures detected a gradual increase of skin temperature from 33.0°C in healthy skin on average to 35.0–36.6°C at the center of inflamma tory lesions in the axilla and to 35.4–36.9°C at the center of inflammation in the groin area. Real-time MIT assessment enabled the definition of the margins and depth of the surgical intervention during the procedure. Conclusion: MIT is a promising tool for the detection of inflammation severity in HS lesions and can be used as a clinical biomarker in evaluation studies of medical and surgical HS treatment.