Skin temperature of the foot: Reliability of infrared image analysis based in the angiosome concept

Abstract

Studies reporting the reliability of image analysis when assessing skin temperature of the foot are scarce. The aim of this study was to assess the interrater and intrarater reliability of the analysis of foot skin temperature based on the angiosome concept and the association between skin temperature differences and the differences in size of the ROIs. Methodology: Thermograms from 26 feet were analysed by two independent assessors and each assessor analysed the same images on different occasions. Mean temperature values of each of the six ROIs were extracted for analysis. Relative reliability was assessed by Intraclass Correlation Coefficient (ICC) measures and absolute reliability was assessed using Bland and Altman agreement measures and standard error of measurement (SEM). The Spearman correlation coefficient was used to assess the association between the skin temperature differences and the differences in size of the ROIs in the interrater and intrarater analysis. Results: The ICC values evidenced excellent interrater and intrarater reliability with the 95% confidence intervals (CI) ranging between 0.962 and 1.000 and the SEM ranged between 0.00°C and 0.36°C. The mean absolute difference (bias) between the measurements ranged between 0.002°C and 0.117°C and small to moderate associations between the differences in skin temperature and the difference in the number of pixels were identified. Conclusion: The excellent interrater and intrarater reliability measures suggest that the methodology of analysis was reliable and may be used in research and clinical settings. Although statistical significant associations between the skin temperature differences and the differences in size of the ROIs were found, the magnitude of the skin temperature differences between assessments and between assessors (0.02-0.17°C) is not clinically relevant.

Thermal imaging for detecting temperature changes within the rheumatoid foot

“…Imaging heat radiation in the form of differences in the temperature distribution on the surface of the skin and the tissues situated deep in the body can provide information about the pathological changes [21,24]. Registered temperature changes are shown in the form of hot spots or areas of inhomogeneity in the curves [15].…”

“…Many authors have reported that the use of thermovision techniques is a very useful tool in the examination of patients. Thermovision techniques have been used for various purposes in medicine, including clinical testing of drugs [12], assessment of vascular reactions in hands [13][14][15][16][17][18], diagnosis of Raynaud's syndrome [19,20], evaluation of observational changes in osteoarthritis [9,15], detection of different kinds of tumors [21,22], and assessment of the skin condition in diabetic feet [23,24].…”

Dynamics of plantar foot temperature after conductive cold provocation in diabetic patients and healthy controls

“…The camera was positioned perpendicular to the feet at 1 metre distance. Images were analysed with FLIR ResearchIR Max software (FLIR Systems, version 4.30.0.69) and regions of interest (ROI) were defined according to the angiosome concept (figure 1), which is a reliable methodology of infrared image analysis [10].…”

Regions of interest selection and thermal imaging data analysis in sports and exercise science: a narrative review

“…First, the number of pixels within the ROI was found to induce an inaccurate evaluation of T sk (Ring and Ammer 2000). The ROI selection was found to play a fundamental role in the reliability of IRT measurements (Ring and Ammer 2000, Seixas et al 2018. In fact, a relevant issue for biomedical IRT is the availability of tools for an objective comparison of images across different conditions or participants.…”