Establishing the thermal patterns of healthy people from Medellín, Colombia

Abstract

Infrared Thermography has been used in the medical field to diagnose illnesses that produce temperature variations. Furthermore, comparisons between the temperatures of contralateral regions or patients and healthy people are used as thermography diagnostic criteria. Under both approaches, the difference in temperature is calculated and, if it falls outside normal ranges, it is considered a sign and symptom of illness. In previous works, the thermal patterns of healthy individuals have been determined in populations from Finland, Portugal, Taiwan, Brazil, and Mexico. However, a comparison of such patterns reveals meaningful discrepancies since the emissivity of the human skin depends on ethnic characteristics and age. Thus, it is necessary to estimate thermal patterns in healthy people from each population and calculate the maximum and minimum temperature differences in their contralateral regions. Specifically, the thermal patterns of healthy Colombian people have not been established so far. Therefore, this work aims to define the thermal patterns of the population of Medellín-Colombia. Such patterns can later be used as reference values to diagnose illnesses in different hospitals in the city. Thirty-seven healthy individuals participated in this study. Data was acquired from the anterior, posterior, right, and left side of the body using a FLIR A655SC thermal camera, and the acquisition protocol was defined in accordance with the method of previous work. The camera recorded twenty-four thermograms from each subject, which were segmented by region-growing and a grid mask algorithm, thus obtaining 43 regions of interest (ROI). The mean temperature and standard deviations of each ROI were also calculated. In most regions, the mean temperature varied between 31.16 °C and 34.58 °C. The lowest mean temperature and highest variability were found in acral regions. Independent samples were assumed in the statistical analysis, and the normality of the temperature of each ROI was verified by the Shapiro–Wilk test. Moreover, Student’s t-test and Mann–Whitney U test were used in the comparison of temperatures of contralateral regions with normal and non normal distributions, respectively. Finally, the temperature difference was found to be insignificant.