Correlation Mapping of Perfusion Patterns in Cutaneous Tissue

Perfusion patterns of cutaneous tissue represent a valuable source of information about the state of the patient’s cardiovascular system and autonomic nervous system (ANS). This concept aims to observe the perfusion changes in the foot sole in two healthy individuals and two subjects affected by diabetes mellitus (DM). We use photoplethysmography imaging (PPGI) to monitor cutaneous perfusion changes. This method, in contrast to conventional contact photoplethysmography (PPG), allows the monitoring of skin perfusion with spatial distribution. We use a machine vision camera and an illumination system using the green light. To induce the perfusion changes, we perform an experiment in the form of a deep breathing test (DBT). The experiment consists of three stages, with the middle stage being the DBT. To evaluate spatial perfusion changes, we use a normalized measure of the correlation of PPGI signals with a reference PPG signal obtained from the foot’s little toe. This method also increases the signal-to-noise ratio (SNR). Subjects with DM shows different patterns of tissue perfusion changes compared to healthy subjects. The DM subjects show increased perfusion after DBT compared to the pre-DBT state, whereas in healthy subjects, the tissue perfusion does not reach the level of the pre-DBT phase. This work can be considered as proof of concept in developing a non-contact and non-intrusive monitoring system that allows a different view of microcirculatory damage in patients with diabetes mellitus, focusing on its spatial distribution.