Physiological swelling imaging in human calf under stocking compression by sparse Bayesian learning implemented into electrical impedance tomography (SBL-EIT)

Physiological swelling in human calf has been imaged under stocking compression by the sparse Bayesian learning implemented into electrical impedance tomography (SBL-EIT) to evaluate the in situ treatment effect of various compression pressures. SBL-EIT reconstructs conductivity distribution [Formula: see text] to image excessive extracellular fluid in subcutaneous adipose tissue (SAT), indicating the susceptibilities to physiological swelling due to various compression pressures. The SBL-EIT was applied to the imaging of eight-subject calves during prolonged standing under three types of net compression pressures <i>P</i> ^net measured by pressure sensor - strong pressure: <i>P</i> ^{net, Strong} = 11.9 [Formula: see text] 2.0 mmHg, weak pressure: <i>P</i> ^{net, Weak} = 4.47 [Formula: see text] 3.1 mmHg, and control pressure: <i>P</i> ^{net, Control} = 0.00 [Formula: see text] 0.0 mmHg, respectively. From the experimental results, the spatial-mean conductivity ⟨<b>σ</b>⟩^α2 with two pre-processing steps to eliminate undesirable effects, i.e., the difference in skin condition and effect of wearing stockings itself, is the highest in the case of stocking with control pressure, followed by weak and strong pressures across all subjects. Moreover, the ⟨<b>σ</b>⟩^α<i>2</i> has a strong positive correlation with the conventional inversed impedance 1/<i>z</i> ^BIA by bioelectrical impedance analysis (BIA) (a correlation coefficient 0.528 < <i>R</i> < 0.990; <i>n</i> = 19 and <i>p</i> < 0.05), which is mainly increased during the prolonged standing. Moreover, various susceptibilities to physiological swelling are investigated based on the increase in [Formula: see text] for each subject, which is associated with subject external factors such as postural changes and circumference and internal factors like SAT.