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Quantitative assessment of skin chromophores in a non-invasive fashion is often desirable. Especially pixel wise
assessment of blood volume and blood oxygenation is beneficial for improved diagnostics. We utilized a multi-spectral
imaging system for acquiring diffuse reflectance images of healthy volunteers' lower forearm. Ischemia and reactive
hyperemia was introduced by occluding the upper arm with a pressure cuff for 5min with 180mmHg. Multi-spectral
images were taken every 30s, before, during and after occlusion. Image reconstruction for blood volume and blood
oxygenation was performed, using a two layered skin model. As the images were taken in a non-contact way, strong
artifacts related to the shape (curvature) of the arms were observed, making reconstruction of optical / physiological
parameters highly inaccurate. We developed a curvature correction method, which is based on extracting the curvature
directly from the intensity images acquired and does not require any additional measures on the object imaged. The
effectiveness of the algorithm was demonstrated, on reconstruction results of blood volume and blood oxygenation for in
vivo data during occlusion of the arm. Pixel wise assessment of blood volume and blood oxygenation was made possible
over the entire image area and comparison of occlusion effects between veins and surrounding skin was performed.
Induced ischemia during occlusion and reactive hyperemia afterwards was observed and quantitatively assessed.
Furthermore, the influence of epidermal thickness on reconstruction results was evaluated and the exact knowledge of
this parameter for fully quantitative assessment was pointed out.
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