Reference Standard for Digital Infrared Thermography of the Surface Temperature of the Lower Limbs

Abstract

Digital infrared thermographic imaging (DITI) is a supplementary diagnostic technique to visualize the surface temperature of the human body. However, there is currently no reference standard for the lower limbs for accurate diagnosis. In this study, we performed DITI on the lower limbs of 905 healthy Korean volunteers (411 males and 494 females aged between 20 and 69 years) to obtain reference standard data. Thermography was conducted on the front, back, lateral sides, and sole area, and 188 regions of interest (ROIs) were analyzed. Additionally, subgroup analysis was conducted according to the proximity of ROIs, sex, and age groups. The mean temperatures of ROIs ranged from 24.60 ± 5.06 to 28.75 ± 5.76 °C and the absolute value of the temperature difference between both sides reached up to 1.06 ± 2.75 °C. According to subgroup analysis, the sole area had a significantly lower temperature than any other areas, men had higher temperatures than women, and the elderly had higher temperatures than the young adults except for the 20s age group (p < 0.001, respectively). This result could be used as a foundation for the establishment of a reference standard for DITI. Practical patient DITI can be accurately interpreted using these data, and it can serve as a basis for further scientific research.

Reference Standards for Digital Infrared Thermography Measuring Surface Temperature of the Upper Limbs

“…The average age of all subjects ( n = 905) was 42.86 ± 12.87 years, and the male-to-female ratio was 411:405. The sample consisted of 183 individuals (97 males and 86 females) in their 20s, 213 (108 males and 105 females) in their 30s; 228 (109 males and 119 females) in their 40s; 177 (65 males and 112 females) in their 50s; and 104 individuals (32 males and 72 females) in their 60s [ 20 ].…”

“…The average surface temperature of the upper limbs varied depending on regions and ROIs, ranging from 27.08 ± 5.14 °C to 31.27 ± 5.53 °C, which is consistent with the results found in our previous study on the lower limbs. However, the average temperatures of the upper limbs were higher than those of the lower limbs (range, 24.60 ± 5.06 °C–27.75 ± 5.76 °C) [ 20 ]. We believe this difference is due to the different distance from the heart [ 21 , 22 , 23 ].…”

“…The sample size for this study was determined to be 922 participants, with a dropout rate of 15%, based on the equation provided in our previous report [ 20 ]. The equation used was as follows: …”

“…However, 17 patients were excluded due to test failure or withdrawal of consent. Therefore, the results from 905 participants were included in the analysis [ 20 ]. All testing was performed under controlled conditions after obtaining informed consent.…”

“…DITI testing was performed using the same equipment and methodology as we previously described [ 20 ]. The Iris-XP Digital infrared imaging system (Medicore, Seoul, Republic of Korea) was employed to obtain the images.…”