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

<b><i>Background:</i></b> 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. <b><i>Objective:</i></b> To evaluate the application of MIT in HS. <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> 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. <b><i>Conclusion:</i></b> 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.

**背景**：皮肤炎症及活动性疾病严重程度的可靠分级，可借助超声成像与新型化脓性汗腺炎/反向痤疮（hidradenitis suppurativa/acne inversa, HS）分级系统IHS4实现。然而，以连续模式客观评估皮肤炎症仍是学界的终极目标。长波医用红外热成像（medical infrared thermography, MIT）可对炎症状态下的血流与温度差异进行评估。
**目的**：探讨MIT在HS中的应用价值。
**方法**：纳入18例HS受累或疑似受累患者（女性11例、男性7例，中位年龄38.75岁，95%置信区间28.5~51岁；赫尔利分级（Hurley score）I级占5.6%、II级38.9%、III级55.5%），对其受累区域或既往疑似HS受累区域行标准化摄影，同时拍摄MIT图像并与摄影图像叠加。采用改良大津法（Otsu）实现病变与背景的自动分割，以勾勒炎症区域。此外，在HS根治术过程中以实时模式应用MIT进行评估。
**结果**：与对应对称体表区域相比，1℃的温度差异可提示炎症存在。MIT热图显示，健康皮肤平均温度为33.0℃，腋窝炎症病灶中心温度逐渐升高至35.0~36.6℃，腹股沟区炎症病灶中心温度则升至35.4~36.9℃。术中实时MIT评估可明确手术干预的边界与深度。
**结论**：MIT是检测HS病灶炎症严重程度的潜在有效工具，可作为HS内科与外科治疗评估研究中的临床生物标志物。