Two-dimensional near infrared spectroscopic imaging of the hand to assess microvascular abnormalities in systemic sclerosis: A pilot study

Patients affected by systemic sclerosis (SSc) develop functional and structural microvascular alterations and progressive fibrosis of the skin and internal organs. Evaluation of skin microcirculation is an important clinical step in the workup of SSc patients. Near infrared (NIR) spectroscopy is a well-established non-invasive technique to assess haemoglobin oxygen saturation (StO2) in the illuminated tissue. The recent development of NIR spectroscopic two-dimensional (2D) imaging offers the possibility of visualising StO2 distribution in large tissue areas. This is particularly important in SSc characterised by a very heterogeneous spatial distribution of the microvascular abnormalities. In addition, the short acquisition time of NIR spectroscopic images allows microvascular "dynamic" conditions, such as the vascular response to physical or pharmacological stimuli, to be evaluated. The present study reports the results of the test application of NIR spectroscopic 2D imaging of the palmar whole-hand surface for the evaluation of peripheral microcirculatory dysfunction in one patient with SSc, as compared with a healthy control, both in "static" (resting) and in "dynamic" (ischaemia-reperfusion) conditions. Spatial heterogeneity of microvascular alterations associated with temporal heterogeneity in vascular reactivity to ischaemic challenge make 2D NIR spectroscopic imaging a promising tool in the assessment of SSc, as compared with the current available techniques. A NIR spectroscopic camera by Kent Imaging Inc, Calgary, Canada was used.