Integral mapping of the sweat-gland activity using differential thermography technique

Background and Objectives: The sweat-gland activity is associated with the functional state of small sympathetic nerve fibers that are subject to destructive changes in a amount of pathologies, for example, such as diabetic peripheral neuropathy and rheumatoid arthritis. In this work, we have solved the problem of visualizing sweat pores on the skin surface using dynamic differential thermography. Materials and Methods: Based on the wavelet analysis of the fingers phalanges skin temperature fluctuations, it was found that the sweat-gland activity forms spectral components at frequencies of about 0.1 Hz and higher. As a result, it was proposed to consider the temperature signal as a twocomponent one. It is believed that the low-frequency component less than 0.1 Hz is mainly due to hemodynamics, the high-frequency component is mainly due to the functioning of the sweat glands and sweating. To implement differential thermography, the difference between the current frame and the frame delayed by 10 s relative to it was used. Results: As a result, this made it possible to isolate spatial high-frequency information corresponding to sweat pores on the dynamic thermogram. Testing with a sharp breath showed that the signal level of the differential thermogram characterizes the level of the sweat-gland activity that changes over time. Building an integral map of sweat-gland activity by averaging differential thermograms over the entire registration period makes it possible to assess the spatial distribution of sweat gland activity time. The given example of an integral map showed a decrease in the spatial density of functioning sweat glands in a patient with type 2 diabetes mellitus compared with a normal subject. Conclusion: Thus, differential thermography and integral maps of the sweat-gland activity can find application in the field of medicine and physiology for quantitative diagnosis and monitoring of therapy for sympathetic nerve fibers dysfunction, which is relevant in a number of socially significant diseases.